This work reports the synthesis of CuFe2O4 (CFO) nanoparticles via the co-precipitation method for supercapacitor applications, emphasizing the effect of annealing temperature. High-resolution X-ray diffraction (HR-XRD) confirms a tetragonal spinel phase, with grain size increasing due to Ostwald ripening. Raman spectra further validate CFO's tetragonal phase, while FE-SEM confirms nanoparticle agglomeration. HR-TEM analysis reveals an average particle size of ∼71.66 nm. FTIR identifies functional groups, and EDS confirms the presence of Cu, Fe, and O, with XPS verifying Cu2+, Fe2+, Fe3+, and O2− oxidation states. Magnetic measurements indicate ferromagnetic behaviour. BET analysis shows that CFO annealed at 800 °C has the highest specific surface area, improving electrochemical performance. Electrochemical tests (CV, GCD, and EIS) reveal optimal redox activity and ion diffusion at 800 °C, achieving a specific capacitance of 911.1 F/g at 1 A/g. An asymmetric supercapacitor with CFO-800 used as positive electrode while negative electrode made of activated carbon delivers 44.42 F/g capacitance, 12.97 Wh/kg energy density, and 3.92 kW/kg power density, with 77.26 % cycling retention and 101.8 % Coulombic efficiency over 5000 cycles. These results highlight CFO's potential for next-generation energy storage applications.

Bacterial infections and the rise of antibiotic-resistant strains pose a critical challenge to public health and has intensified the need for alternative antimicrobial agents. This study explores the synthesis, characterization, and antibacterial efficacy of hexagonal Bi2Te3 platelets prepared via a solvothermal method using polyvinylpyrrolidone (PVP) as a stabilizer, ensuring high dispersion stability and preventing agglomeration. The synthesized Bi2Te3 nanoparticles were thoroughly characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM), Raman and Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), confirming the crystalline quality, surface properties, and functional groups of the Bi2Te3 platelets. The antibacterial efficacy was assessed using well-diffusion assays and minimum inhibitory concentration (MIC) tests, demonstrating effective bactericidal action, particularly against Gram-positive bacteria, attributed to membrane disruption and reactive oxygen species (ROS) generation. Additionally, cytotoxicity studies on A549 lung carcinoma cells indicated dose-dependent effects, supporting the biocompatibility of Bi2Te3 at optimal concentrations. The scalable of hexagonal Bi2Te3 platelets position them as promising candidates for advanced antibacterial applications.

Easy-to-fabricate, flexible optoelectronic devices based on conducting organic polymers are in high demand due to their cost-effectiveness and low weight. The hole and electron transport layers (HTL/ELT) are central to the working of these devices. Conductive polymers are now extensively used (HTL/ETL) in solar cells, as hole injection layers in OLEDs, and as electrodes or active channel layers in organic thin film transistors. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is the mainstay of these devices. The energy levels of the tailored PEDOT:PSS determine the work function, the efficiency of charge separation, and the device’s performance. Transparent electrodes are another requirement for the efficient functioning of devices, with indium tin oxide (ITO) being a common choice. To overcome problems associated with ITO, researchers are focusing on conducting polymer materials such as PEDOT:PSS as transparent electrode materials. Flexibility, water processability, high electrical conductivity, good optical transparency, biocompatibility, and good thermoelectric properties make functionalized PEDOT:PSS a versatile conductive polymer. Priced for its versatility and good performance, it is used in cutting-edge applications including LEDs, solar cells, and sensors. Cost-effective production and easy production scalability make it a default material for optoelectronic applications despite some challenges. This review highlights recent research with special emphasis on tuning the work function of PEDOT:PSS to enhance the performance of optoelectronic devices.

In this study, we successfully synthesized α-MoO3 nanolayers using a proximity evaporation technique, positioning the Mo film approximately 1 mm from the target substrate at atmospheric conditions. This novel method bypasses the need for supplemental oxygen sources by utilizing ambient oxygen, resulting in cost-effective and scalable production of MoO3. The α-MoO3 films synthesized at an optimal growth temperature of 550 °C demonstrate well-controlled layer thickness, high crystallinity, and uniform stoichiometry. Detailed characterizations were performed, including XRD for crystallographic confirmation, SEM–EDS for morphology and stoichiometry, Raman spectroscopy for vibrational modes, and UV–Vis for optical properties, revealing a tunable bandgap of approximately 3.7 eV. I-V measurements indicated a high resistance of 8.7 × 106 Ω, confirming the material’s insulating nature, and an optimum dielectric constant of 1253. Photo-response measurements demonstrated a significant photocurrent increase under illumination, with responsivity 8.8 A.W−1, detectivity1.2 × 1013 J, and quantum efficiency of 18.5%, respectively. The proposed proximity evaporation technique demonstrates potential as a scalable approach for synthesizing high-quality two-dimensional (2D) transition metal oxides like MoO3, with implications for applications in optoelectronics and sensing.

Tackling the critical issue of water pollution requires sustainable remediation approaches. This review focuses on the promise of innovative biopolymer-based hydrogel microspheres. Made from natural polymers such as alginate and chitosan, these microspheres have demonstrated substantial effectiveness in adsorbing and eliminating various water contaminants, including heavy metals, organic dyes, and pharmaceuticals. For instance, calcium alginate gel beads are particularly efficient in removing Pd(II) ions, while composite alginate materials excel in capturing radioactive and pharmaceutical pollutants. Moreover, chitosan hydrogel microspheres efficiently remove heavy metals, dyes, and organic pollutants through electrostatic interactions, ion exchange, and chelation. Recent advancements in designing and synthesizing this hydrogel microspheres highlight their enhanced properties, such as high surface area, porosity, and customizable functional groups. Integrating nanomaterials and bioactive agents has further boosted their pollutant removal effectiveness, allowing these microspheres to target various contaminants from azo dyes to pharmaceuticals like ciprofloxacin and methylene blue. This review underscores the transformative potential of alginate and chitosan-based hydrogel microspheres in addressing water pollution. By analyzing recent innovations and potential solutions to scaling challenges, this work helps advance our understanding of how these cutting-edge hydrogels can act as effective, eco-friendly alternatives for sustainable water remediation.

Green Hydrogen emerges as a promising energy solution in the quest for achieving Net Zero goals. The application of particulate semiconductors in photocatalytic water splitting introduces a potentially scalable and economically viable technology for converting solar energy into hydrogen. Overcoming the challenge of efficiently transferring photoelectrons and photoholes for both reduction and oxidation on the same catalyst is a significant hurdle in photocatalysis. In this context, we introduce highly efficient crystalline elemental boron nanostructures as photocatalysts, employing a straightforward and scalable synthesis method yield green hydrogen production without the need for additional co-catalysts or sacrificial agents. The resulting photocatalyst demonstrates stability and high activity in H2 production, achieving over 1 % solar-to-hydrogen energy conversion efficiency (>15,000 μmol. g−1.h−1) during continuous 12-h illumination. This efficiency is credited to broad optical absorption and the crystalline nature of boron nanostructures, paving the way for potential scale-up of reactors using crystalline boron photocatalysts.

The increasing environmental challenges caused by pharmaceutical waste, especially antibiotics and contaminants, necessitate sustainable solutions. Cellulose-based membranes are considered advanced tools and show great potential as effective materials for the removal of drugs and organic contaminants. This review introduces an environmentally friendly composite membrane for the elimination of antibiotics and dye contaminants from water and food, without the use of toxic additives. The potential of cellulose-based membranes in reducing the impact on water quality and promoting environmental sustainability is emphasized. Additionally, the benefits of using biobased cellulose membranes in membrane biological reactors for the removal of antibiotics from pharmaceutical waste and milk are explored, presenting an innovative approach to achieving a circular economy. This review provides recent and comprehensive insights into membrane bioreactor technology, making it a valuable resource for researchers seeking efficient methods to break down antibiotics in industrial wastewater, particularly in the pharmaceutical and dairy industries.

The escalating need for lithium-ion batteries (LIBs), driven by their expanding range of applications in our daily lives, has led to a surge in interest in metal selenides as potential anode materials. Among them, Bi2Se3 stands out as a promising anode material for LIBs due to its unique layered structure. Herein, we explored hexagonally structured layered Bi2Se3 platelets synthesized using the solvothermal method. The electrochemical performance of these platelets in LIBs was thoroughly examined, revealing an impressive initial discharge specific capacity of 556 mA h g−1 at a current density of 100 mA g−1 and a coulombic efficiency of 66.5%. Improved cycling stability, rate performance, and discharge voltage profile at various current densities were observed. The plateaus observed during the charge/discharge profile were clearly illustrated by the CV results. The reaction kinetics indicated that both ion diffusion and pseudo-capacitance behavior are crucial for the observed high electrochemical performance. Moreover, the hexagonal Bi2Se3 platelets exhibited a high ion-diffusion coefficient of 1.8 × 10−13 cm2 s−1 and a charge transfer impedance of 23 Ω post-cycling. Furthermore, the crystal structure, lattice vibrational bonding, and surface morphology of Bi2Se3 were explored using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. FTIR spectroscopy was utilized for identifying the functional groups, while X-ray photoelectron spectroscopy (XPS) was used to identify the elemental composition and oxidation states of Bi2Se3.

Nickel ferrite (NiFe2O4) nanostructures (NSs) were synthesized via a low-cost and reproducible co-precipitation method. The as-synthesized material was annealed at different temperatures to investigate electrochemical performances for oxygen reduction reaction (ORR) and energy storage capacity. The X-ray diffraction (XRD) pattern confirmed the cubic structure of NiFe2O4 (NF) NSs. The decreased agglomeration and increased particle size were observed by field effect scanning electron microscopy (FE-SEM) with annealing temperature. The presence of Ni–O and Fe–O bonds at tetrahedral and octahedral sites was confirmed by Fourier transform infrared (FTIR) spectroscopy. The electrochemical analysis studied using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) demonstrated that the NF NSs annealed at 900 °C exhibited impressive electrochemical activity with a specific capacitance of ∼136 F/g, outperforming samples synthesized at lower temperatures. Moreover, the electrode material displayed excellent long-term stability over 3000 cycles for ORR activity. The remarkable electrochemical performance of NF NSs at higher annealing temperatures highlights their potential for future energy storage and conversion devices.

Abstract: This study explores the capabilities of solvothermally synthesized bismuth telluride (Bi2Te3) hexagonal platelets as a promising anode material for both Li-ion and Na-ion batteries. Bi2Te3 anode material exhibits a high initial discharge capacity of 837 mA h g−1 at a current density of 100 mA g−1 against Li metal whereas, an initial discharge capacity of 678 mA h g−1 is observed at a current density of 20 mA g−1 for the same against the Na metal. The Li- and Na-storage mechanism in Bi2Te3 platelets has been investigated by using both galvanostatic charge–discharge and cyclic voltammetry measurements. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy techniques have been used to examine the structural characteristics, surface morphology, and lattice vibrational modes of Bi2Te3 hexagonal platelets. Further, FTIR spectroscopy was employed to determine the presence of functional groups while X-ray photoelectron spectroscopy was employed for the elemental analysis of Bi2Te3 sample. Graphical abstract: (Figure presented.)

The burgeoning electronics industry has sparked a corresponding surge in electromagnetic pollution, necessitating robust shielding methods with a focus on absorption. Polymer-based composites, especially those incorporating polyaniline (PANI), are pivotal in this endeavor due to their electrical conductivity and cost-effectiveness. This review provides a comprehensive examination of current state-of-the-art research in the field of electromagnetic shielding materials, exploring their applications, benefits, and limitations. Graphene’s exceptional mechanical, electrical, and optical properties, when combined with PANI matrices, elevate electromagnetic interference shielding effectiveness (EMI SE). Its unique characteristics enhance electron transport, boosting overall electrical conductivity and reflectivity. Simultaneously, carbon nanotubes show promise for polymer composites, leveraging their superior strength, stiffness, aspect ratio, and electrical conductivity. The inclusion of Fe3O4 magnetic material significantly impacts composite permeability due to its large saturation magnetization. MXene, a two-dimensional transition metal carbonitride, emerges as a promising option for electromagnetic interference (EMI) shielding. With electrical conductivity and specific surface area comparable to graphene, MXene is gaining attention in EMI shielding research. The review explores diverse strategies utilizing various fillers to enhance PANI-based nanocomposites for EMI shielding, presenting a comprehensive overview of advanced shielding materials in various applications.

Increasing dependence and usage of electronic devices has raised the concern for electromagnetic (EM) shielding. This review article is an overview of ongoing cutting-edge research on electromagnetic shielding materials, their applications, advantages and shortcomings. The article highlights doping of polypyrrole(PPy) with different components to achieve desired properties. The work focusses on methods of achieving desired properties of PPy through doping. We have summarized results of doping it with Graphene, Nickel, MXene, Iron Oxide and CNT to achieve desired properties like better electrical conductivity, flexibility and lighter material, greater tensile strength, biocompatibility, better microwave absorption and better magnetic properties. The review presents compilation of most recent ongoing research in the field of electromagnetic shielding. We have also discussed existing limitations and possible future prospects in the ongoing research.

Fabricating large-area two-dimensional (2D) metal dichalcogenide layers with stoichiometry and uniformity has been a research focus over the past few years. Most of the time, the types of growth methods determine of quality of the 2D layers, and in turn, they affect their electronic properties and applications. Here, we report a nonconventional facile way of synthesizing nearly single crystalline 2H hexagonal SnS2 and orthorhombic SnS layers via proximity evaporation, where the distance between the Sn precursor film and the target substrate is ~1 mm. This short distance provides self-limiting 2D layers with good uniformity and stoichiometry. The phase transition study was carried out by varying the growth temperature (300–650°C). Pure phases of SnS2 and SnS were formed at the optimum temperatures. Large hexagonal SnS2 sheets with a 1:2 stoichiometric ratio were observed. The high-resolution transmission electron microscopy (HRTEM) and Raman spectra further revealed the 2H phase of SnS2 sheets. Photoresponse studies of both pure phases of SnS and SnS2 showed significant photoresponse with improved photocurrent. Our synthesis method can be extended to grow large-area uniform sheets of other 2D materials having lower heat of formation. Graphical Abstract: [Figure not available: see fulltext.]

Lithium-Sulfur batteries (LSBs) are one of the most promising next-generation batteries to replace Li-ion batteries that power everything from small portable devices to large electric vehicles. LSBs boast a nearly five times higher theoretical capacity than Li-ion batteries due to sulfur’s high theoretical capacity, and LSBs use abundant sulfur instead of rare metals as their cathodes. In order to make LSBs commercially viable, an LSB’s separator must permit fast Li-ion diffusion while suppressing the migration of soluble lithium polysulfides (LiPSs). Polyolefin separators (commonly used in Li-ion batteries) fail to block LiPSs, have low thermal stability, poor mechanical strength, and weak electrolyte affinity. Novel nanofiber (NF) separators address the aforementioned shortcomings of polyolefin separators with intrinsically superior properties. Moreover, NF separators can easily be produced in large volumes, fine-tuned via facile electrospinning techniques, and modified with various additives. This review discusses the design principles and performance of LSBs with exemplary NF separators. The benefits of using various polymers and the effects of different polymer modifications are analyzed. We also discuss the conversion of polymer NFs into carbon NFs (CNFs) and their effects on rate capability and thermal stability. Finally, common and promising modifiers for NF separators, including carbon, metal oxide, and metal-organic framework (MOF), are examined. We highlight the underlying properties of the composite NF separators that enhance the capacity, cyclability, and resilience of LSBs.

Cadmium sulfide (CdS) nanoparticles (NPs) were synthesized using a biodegradable starch [(C6H10O5)n] polymer as a capping and stabilizing agent. The as-synthesized CdS NPs were highly crystalline and had a hexagonal structure with an average particle size of ~ 10.5 nm. Fourier transform infrared (FTIR) spectroscopy analysis was used to examine the presence and interactions of starch on the surface of the nanoparticles. The electronic behavior of CdS NPs was analyzed using I–V measurements and impedance spectroscopy. These NPs exhibit semiconducting behavior with resistance and conductance values of 1.78 ×108 Ω, and 5.61 × 10−9 S, respectively. Photoresponse studies of CdS NPs showed significant photoresponse with improved photocurrent under light conditions. The dielectric measurements were done at different temperatures, during both the heating and cooling cycles, and the frequency dependence and temperature dependence of dielectric constant and dielectric loss were investigated.

In recent years, there has been a huge surge in interest in improving the efficiency of smart electronic and optoelectronic devices via the development of novel materials and printing technologies. Inkjet printing, known to deposit ‘ink on demand’, helps to reduce the consumption of materials. Printing inks on various substrates like paper, glass, and fabric is possible, generating flexible devices that include supercapacitors, sensors, and electrochromic devices. Newer inks being tested and used include formulations of carbon nanoparticles, photochromic dyes, conducting polymers, etc. Among the conducting polymers, PANI has been well researched. It can be synthesized and doped easily and allows for the easy formation of composite conductive inks. Doping and the addition of additives like metal salts, oxidants, and halide ions tune its electrical properties. PANI has a large specific capacitance and has been researched for its applications in supercapacitors. It has been used as a sensor for pH and humidity as well as a biosensor for sweat, blood, etc. The response is generated by a change in its electrical conductivity. This review paper presents an overview of the investigations on the formulation of the inks based on conductive polymers, mainly centered around PANI, and inkjet printing of its formulations for a variety of devices, including supercapacitors, sensors, electrochromic devices, and patterning on flexible substrates. It covers their performance characteristics and also presents a future perspective on inkjet printing technology for advanced electronic, optoelectronic, and other conductive-polymer-based devices. We believe this review provides a new direction for next-generation conductive-polymer-based devices for various applications.

Starch [(C6H10O5)n]-stabilized bismuth sulfide (Bi2S3) nanoparticles (NPs) were synthesized in a single-pot reaction using bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) and sodium sulfide (Na2S) as precursors. Bi2S3NPs were stable over time and a wide band gap of 2.86 eV was observed. The capping of starch on the Bi2S3NPs prevents them from agglomeration and provides regular uniform shapes. The synthesized Bi2S3NPs were quasispherical, and the measured average particle size was ∼11 nm. The NPs are crystalline with an orthorhombic structure as determined by powder X-ray diffraction and transmission electron microscopy. The existence and interaction of starch on the NP's surface were analyzed using circular dichroism. Impedance spectroscopy was used to measure the electronic behavior of Bi2S3NPs at various temperatures and frequencies. The dielectric measurements on the NPs show high dielectric polarizations. Furthermore, it was observed that the synthesized Bi2S3NPs inhibited bacterial strains (Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) and demonstrated substantial antibacterial activity.

Interest in carbon quantum dots (CQDs) has recently boomed due to their potential to enhance the performance of various solar technologies as nontoxic, naturally abundant, and cleanly produced nanomaterials. CQDs and their other variations, such as nitrogen-doped carbon quantum dots (NCQDs) and graphene quantum dots (GQDs), have improved the performance of luminescent solar concentrators (LSCs) and photovoltaic (PV) cells due to their excellent optical properties. As fluorophores in LSCs, CQDs are mostly transparent to visible light and have absorption/re-emission spectra that can be easily controlled. The outstanding optical properties of CQDs make them promising materials to replace expensive, heavy-metal-based fluorophores. Various CQDs have also been used as or doped into the photoanode, counter electrode, hole transport layer (HTL), and electron transport layer (ETL) of dye-sensitized solar cells (DSSCs), organic solar cells (OSC), perovskite solar cells (PSCs), and other PV cell configurations. The addition of CQDs into the various solar cell components has reduced electron recombination, increased charge density, and boosted electron mobility, improving the performance of the PV cells. Enhancing the power conversion efficiency (PCE) of photovoltaic devices is essential in propagating green energy technology. Thus, CQDs offer an affordable, safe, and environmentally friendly method to advance photovoltaic performance.

p-type cupric oxide (p-CuO) thin films on n-type silicon substrates were grown to make p-CuO/n-Si heterojunctions. The CuO deposition on Si was carried out using radio frequency (RF) magnetron sputtering followed by rapid thermal annealing at 350°C. Plasma nitridation was used to incorporate nitrogen (N) for improving the electrical conductivity of the CuO thin films. The crystalline structure and surface composition of RF-sputtered CuO were characterized by x-ray diffraction and x-ray photoelectron spectroscopy. It was observed that the introduction of nitrogen in CuO improves the photovoltaic properties, such as the open-circuit voltage, short circuit current, and the photocurrent of the p-CuO-n-Si heterojunction.

van der Waals (vdW) materials have shown unique electrical and optical properties depending on the thickness due to strong interlayer interaction and symmetry breaking at the monolayer level. In contrast, the study of electrical and tribological properties and their thickness-insensitivity of van der Waals oxides are lacking due to difficulties in the fabrication of high quality two-dimensional oxides and the investigation of nanoscale properties. Here we investigated various tribological and electrical properties, such as, friction, adhesion, work function, tunnel current, and dielectric constant, of the single-crystal α-MoO3 nanosheets epitaxially grown on graphite by using atomic force microscopy. The friction of atomically smooth MoO3 is rapidly saturated within a few layers. The thickness insensitivity of friction is due to very weak mechanical interlayer interaction. Similarly, work function (4.73 eV for 2 layers (hereafter denoted as L)) and dielectric constant (6 for 2L and 10.5-11 for >3L) of MoO3 in MoO3 showed thickness insensitivity due to weak interlayer coupling. Tunnel current measurements by conductive atomic force microscopy showed that even 2L MoO3 of 1.4 nm is resistant to tunneling with a high dielectric strength of 14 MV/cm. The thickness-indifferent electrical properties of high dielectric constant and tunnel resistance by weak interlayer coupling and high crystallinity show a promise in the use of MoO3 nanosheets for nanodevice applications.

Monoclinic molybdenum trioxide (β-MoO 3 ) nanostructures (shaped like nanoribbons: NRs) were grown on Si(1 0 0), Si(5 5 1 2) and fluorine-doped tin oxide (FTO) by molecular beam epitaxy (MBE) technique under ultra-high vacuum (UHV) conditions. The dependence of substrate conditions and the effective thickness of MoO 3 films on the morphology of nanostructures and their structural aspects were reported. The electron microscopy measurements show that the length and the aspect ratio of nanostructures increased by, 260% without any significant change in the width for a change in effective thickness from 5 nm to 30 nm. NRs are grown along 〈0 1 1〉 for all the effective thickness of MoO 3 films. Similarly, when we increased the film thickness from 5 nm to 30 nm, the optical band gap decreased from 3.38 ± 0.01 eV to 3.17 ± 0.01 eV and the local work function increased from 5.397 ± 0.025 eV to 5.757 ± 0.030 eV. Field emission turn-on field decreased from 3.58 V/μm for 10 μA/cm 2 to 2.5 V/μm and field enhancement factor increased from 1.1 × 10 4 to 5.9 × 10 4 for effective thickness variation of 5–30 nm β-MoO 3 structures. The β-MoO 3 nanostructures found to be much better than the α-MoO 3 nanostructures due to low work function, low turn on field and high field enhancement factor, and are expected to be useful applications.

Since the isolation of graphene, various two-dimensional (2D) materials have been extensively investigated. Nevertheless, only few 2D oxides have been reported to date due to difficulties in their synthesis. However, it is expected that the layered transition-metal oxides (TMOs) could be missing blocks for van der Waals heterostructures and essential elements for 2D electronics. Herein, the crystal structure and band structure of van der Waals epitaxially grown α-MoO3 nanosheets on various 2D growth templates are characterized. Monolayer and multilayer α-MoO3 nanosheets are successfully grown on a 2D substrate by simply evaporating amorphous molybdenum oxide thin film in ambient conditions. A single-crystal α-MoO3 nanosheet without grain boundary is epitaxially grown on various 2D substrates despite a large lattice mismatch. During growth, the quasi-stable monolayer α-MoO3 first covers the 2D substrate, then additional layers are continuously grown on the first monolayer α-MoO3. The band gap of the α-MoO3 increases from 2.9 to 3.2 eV as the thickness decreases. Furthermore, due to oxygen vacancies and surface adsorbates, the synthesized α-MoO3 is highly n-doped with a small work function. Therefore, α-MoO3 field-effect transistors (FETs) exhibit a typical n-type conductance. This work shows the great potential of ultra-thin α-MoO3 in 2D-material-based electronics.

Despite the great advances in microsurgery, some neural injuries cannot be treated surgically. Stem cell therapy is a potential approach for treating neuroinjuries and neurodegenerative disease. Researchers have developed various bioactive scaffolds for tissue engineering, exhibiting enhanced cell viability, attachment, migration, neurite elongation, and neuronal differentiation, with the aim of developing functional tissue grafts that can be incorporated in vivo. Facilitating the appropriate interactions between the cells and extracellular matrix is crucial in scaffold design. Modification of scaffolds with biofunctional motifs such as growth factors, drugs, or peptides can improve this interaction. In this review, we focus on the laminin-derived Ile-Lys-Val-Ala-Val peptide as a biofunctional epitope for neuronal tissue engineering. Inclusion of this bioactive peptide within a scaffold is known to enhance cell adhesion as well as neuronal differentiation in both 2-dimensional and 3-dimensional environments. The in vivo application of this peptide is also briefly described.

Graphene has received great attention owing to its superior physical properties, making graphene suitable for multiple applications. Numerous graphene growth techniques have been developed in the past decade to provide scalable high quality graphene. Among these techniques, chemical vapor deposition (CVD) on catalytic metal films holds great promises for a large-scale graphene growth. Even though extensive efforts have been devoted to synthesize high quality graphene, formation of defects. In particular, grain boundaries (GBs) have a dominant effect on properties, motivating extensive efforts to tune the CVD growth process to minimize GB. Rapid imaging of GBs will significantly aid in studies of CVD graphene grain structure. Here we report a straightforward technique to optically observe GBs in CVD-grown graphene via optical microscopy, allowing rapid assessment of graphene quality as well as the number of layers. The local oxidation of copper through the damaged GBs induces an optically discernable color change in the underlying copper due to different extend of oxidation between the two copper regions under grains and GBs. Our observation technique for GBs of graphene paves a path for understanding fundamental mechanisms of graphene growth and efficient quality evaluation of large-scale graphene sheet for mass production.

Currently, energy storage devices draw considerable attention owing to the growing need for clean energy. The depletion of fossil fuels and the generation of greenhouse gases have led to the development of alternative, environmentally friendly energy storage devices. Supercapacitors with high power densities are excellent devices for energy storage. Although carbon-based materials are widely used in such devices, their non-faradic behavior in electrical double layer capacitors (EDLCs) limits the maximum power density that can be generated. In contrast, the faradaic mechanism of transition metal hydroxides results in better capacitance rates along with good stability during cycling. This review is confined to nickel cobalt layered double hydroxides (NiCo LDHs) classified based on the fabrication of electrodes for application in supercapacitors. We discuss the growth of the active LDH material in situ or ex situ on the current collector and how the synthesis can affect the crystal structure as well as the electrochemical performance of the electrode.

Novel materials suitable for optoelectronics are of great interest due to limited and diminishing energy resources and the movement toward a green earth. We report a simple film growth method to tune the S composition, x from 1 to 2 in semiconductor ultrathin SnSx films on quartz substrates, that is, single phase SnS, single phase SnS2, and mixed phases of both SnS and SnS2 by varying the sulfurization temperature from 150 to 500 °C. Due to the ultrathin nature of the SnSx films, their structural and optical properties are characterized and cross-checked by multiple surface-sensitive techniques. The grazing incidence X-ray diffraction (GIXRD) shows that the single phase SnS forms at 150 °C, single phase SnS2 forms at 350 °C and higher, and mixed phases of SnS and SnS2 form at temperature between. GIXRD shows structures of SnS film and SnS2 film are orthorhombic and 2H hexagonal, respectively. To complement the GIXRD, the reflection high energy electron diffraction pattern analysis shows that both pure phases are polycrystalline on the surface. Raman spectra support existence of pure phase SnS, pure phase SnS2, and mixed phases of SnS and SnS2. X-ray photoelectron spectroscopy reveals that the near surface stoichiometry of both single phase SnS and single phase SnS2 are close to Sn/S ratios of 1:1 and 1:2, respectively. UV-vis spectroscopy shows the optical absorption coefficient of SnS film is higher than 105 cm-1 above the optical bandgap of 1.38 ± 0.02 eV, an ideal optical absorber. A two-terminal device made of SnS film grown on SiO2 substrates shows good photoresponse. The SnS2 has an optical bandgap of 2.21 ± 0.02 eV. A photoluminescence (PL) peak of SnS2 film is observed at ∼542 nm. Time-resolved PL of the single phase ultrathin SnS2 film indicates a carrier lifetime of 1.62 ns, longer than sub nanosecond lifetime from multilayer SnS2. Our comprehensive results show that ultrathin SnS and SnS2 films have the required properties for potential photodetectors and solar cell applications but consume much less material as compared with current thin film devices.

Remarkable properties of layered metal dichalcogenides and their potential applications in various fields have raised intense interest worldwide. We report tens of microns-sized ultrathin single crystal SnS2 flakes grown on amorphous substrates using a simple one-step thermal coevaporation process. X-ray pole figure analysis reveals that a majority of flakes are oriented with the (0001) plane parallel to the substrate and a preferred fiber texture. For few-layer-thick SnS2, Moire patterns of 6-fold and 12-fold symmetries are observed by transmission electron microscopy imaging and diffraction. These patterns result from the relative rotation between SnS2 layers in the ultrathin flake. The 12-fold symmetry is consistent with a known quasicrystal pattern. The photoluminescence spectrum supports that these ultrathin flakes possess a direct bandgap. Carrier lifetime measured by time-resolved photoluminescence of a single flake is a few nanoseconds. These results improve our understanding of the formation and shape of ultrathin SnS2 flakes.

Ultrathin NbS2 films were synthesized from sputter-deposited ultrathin Nb films on SiO2/Si and quartz substrates at 850 °C under sulfur vapor pressure. The structure and surface composition of the synthesized films were characterized by grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. The films have rhombohedral 3R-NbS2 structure and are nearly stoichiometric. The optical bandgaps of ultrathin NbS2 samples were determined from ultraviolet-visible-near-infrared spectrometry to be in the range of ∼0.43 to ∼0.90 eV and indirect. This implies that the ultrathin NbS2 film is semiconducting and differs from the metallic nature of bulk NbS2. The Raman shifts show distinct Raman active modes that depend on film thickness. The simple growth method developed can be applied to other TMDCs in which the metal has a high oxide heat of formation. (Figure Presented).

Well-ordered, substrate symmetry-driven, AuxSiy structures of average size ~25 nm were formed under ultra-high vacuum (UHV) conditions using molecular beam epitaxy method. Post-annealing was done at 500 °C in three different vacuum conditions: (1) low vacuum (LV) (10−2 mbar), (2) high vacuum (HV) (10−5 mbar) and (3) UHV (10−10 mbar) (MBE chamber). For both HV and LV cases, the AuxSiy nanostructures were found to have their corners rounded unlike in UHV case where the structures have sharp edges. In all the above three cases, samples were exposed to air before annealing. In situ annealing inside UHV chamber without exposing to air resulted in well-aligned rectangles with sharp corners, while sharp but irregular island structures were found for air exposed and UHV annealing system. The role of residual gases present in LV and HV annealing environment and inhibition of lateral surface diffusion due to the presence of surface oxide (through air exposure) would be discussed. Annealing at various conditions yielded variation in the coverage and correspondingly, the average area of nanostructures varied from a ~329 nm2 (as deposited) to ~2,578 nm2 (at high temperature). High-resolution transmission electron microscopy (planar and cross section) has been utilized to study the morphological variations.

A simple method for the synthesis of Nb2O5 films of thicknesses ranging from tens to several hundreds of nanometers on amorphous silicon dioxide or quartz substrates is presented. Nb2O5 films were formed by annealing the sputter deposited Nb films under an Ar flow and without oxygen plasma in a quartz tube within a furnace at 850 °C. The structural, compositional, optical, and vibrational properties were characterized by grazing incidence X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, and Raman scattering. Each of the Nb2O5 films is polycrystalline with an orthorhombic crystal structure. We observed vibrational modes including longitudinal optical, transverse optical, and triply degenerate modes, and measured the indirect optical band gap to be ∼3.65 eV. The transmittance spectrum of the ∼20 nm thick Nb2O5 film shows over 90% transmittance below the band gap energy in the visible wavelength range and decreases to less than 20% in the ultraviolet regime. The optical properties of the films in the UV-vis range show potential applications as UV detectors.

Ge1-xSnx alloyed films were grown on glass substrates by sequential physical vapor deposition of a biaxial CaF2 buffer layer and a Sn heteroepitaxial layer at room temperature, followed by a Ge layer grown at low temperatures (200-350 °C). The predeposited Sn on the CaF 2 layer enhances Ge diffusion and crystallization. Sn is substituted into the Ge lattice to form a biaxial Ge1-xSnx alloyed film. The epitaxial relationships were obtained from X-ray pole figures of the samples with Ge1-xSnx 〈101〉∥CaF2 〈101〉 and Ge1-xSnx 〈110〉∥CaF 2 〈110〉. Crystallization and biaxial texture formation start at about 200 °C with the best biaxial Ge1-xSnx film grown at about 300 °C, which is 100 °C lower than the growth temperature of biaxial pure Ge film without Sn on the CaF2/glass substrate. The microstructure, texture and Sn concentration of the Ge 1-xSnx films were characterized by X-ray diffraction, X-ray pole figure analysis, and transmission electron microscopy. The spatial chemical composition of Sn in Ge1-xSnx was measured by energy-dispersive X-ray spectroscopy and was found to be nearly uniform throughout the thickness of the alloyed film. Raman spectra show shifts of Ge-Ge, Ge-Sn, and Sn-Sn vibration modes due to the percentage change of substitutional Sn in Ge as a function of growth temperature. This growth method is an alternative cost-effective way to grow biaxial semiconductor films on amorphous substrates. This journal is © the Partner Organisations 2014.

We report on the interfacial phenomena that occur at the initial stages of Ge nanowire growth using gold as the catalyst on Ge(100) substrates under ultra high vacuum (UHV) conditions using molecular beam epitaxy (MBE). Room temperature deposition of a thin Au layer using MBE showed a wetting nature while de-wetting has been observed at 500 °C and higher temperatures. The deposition of a thin layer of Ge at this condition resulted in the formation of Ge nanostructures and Au islands on Ge pedestals, corresponding to the initial growth of the Ge nanowires. Ge deposition at 600°C yielded larger Ge nanowires below the Au/AuGe catalyst interface due to the enhancement of the lateral material transport. © The Royal Society of Chemistry 2014.

Reflection high-energy electron diffraction (RHEED) pole figure technique using the transmission mode has been developed to study the texture evolution of thin films. For quantitative evaluation of thin film texture, including the dispersion of texture, one would require the knowledge of the instrument response function. We report the characterization of instrument response in RHEED pole figure from an epitaxial CdTe(1 0 0) film grown on GaAs(1 0 0) substrate. We found the finite mean free path of electrons in a film contributes to the broadening of the poles. In addition, the image processing step size used in the construction of a pole figure also affects the broadening of constructed poles. We apply the measured instrument response in RHEED pole figure to quantitatively analyze a biaxially textured CdTe(1 1 1) film deposited on a biaxially textured Ge(1 1 1) substrate. Through the deconvolution of the measured dispersions from the poles in the textured CdTe(1 1 1) film by the instrument response function, we obtain the out-of-plane and in-plane dispersions of the biaxially textured CdTe(1 1 1) film. This method is generic and the instrument response should be considered in order to obtain quantitative texture information for other epitaxial and textured nanostructured films through RHEED pole figure measurements. © 2013 Elsevier B.V. All rights reserved.

We report on the phase separation in Au-Ge system leading to the formation of lobe-lobe (bi-lobed) Au-Ge nanostructures under ultra high vacuum (UHV) conditions (≈3 × 10 -10 mbar) on clean Si(100) surfaces. For this study, ≈2.0 nm thick Au samples were grown on the substrate surface by molecular beam epitaxy. Thermal annealing was carried out inside the UHV chamber at temperature ≈500 °C and following this, nearly square shaped Au xSi 1-x nano structures of average length ≈48 nm were formed. A ≈2 nm Ge film was further deposited on the above surface while the substrate was kept at a temperature of ≈500 °C. Well ordered Au-Ge nanostructures where Au and Ge residing side by side (lobe-lobe structures) were formed. In our systematic studies, we show that, gold-silicide nanoalloy formation at the substrate (Si) surface is necessary for forming phase separated Au-Ge bilobed nanostructures. These results show that the Au-Ge bonding is unstable in nature. Electron microscopy (TEM, STEM-EDS, SEM) studies were carried out to determine the structure of Au-Ge nano systems. Rutherford backscattering spectrometry measurements show gold inter-diffusion into substrate while it is absent for Ge. © 2012 American Institute of Physics.

We report on the formation of oriented gold nanostructures on Si(100) substrate by annealing procedures in low vacuum (≈10 -2 mbar) and at high temperature (≈975 °C). Various thicknesses of gold films have been deposited with SiO x (using high vacuum thermal evaporation) and without SiO x (using molecular beam epitaxy) at the interface on Si(100). Electron microscopy measurements were performed to determine the morphology, orientation of the structures and the nature of oxide layer. Interfacial oxide layer, low vacuum and high temperature annealing conditions are found to be necessary to grow oriented gold structures. These gold structures can be transferred by simple scratching method. © 2012 American Institute of Physics.

Growth of Ag islands under ultra-high vacuum condition on air-oxidized Si(110)-(5 × 1) surfaces has been investigated by in situ reflection high energy electron diffraction and ex situ scanning electron microscopy and cross-sectional transmission electron microscopy. A thin oxide is formed on Si via exposure of the clean Si(110)-(5 × 1) surface to air. The oxide layer has a short range order. Deposition of Ag at different thicknesses and at different substrate temperatures reveal that the crystalline qualities of the Ag film are almost independent of the thickness of the Ag layer and depend only on the substrate temperature. Ag deposition at room temperature leads to the growth of randomly oriented Ag islands while preferred orientation evolves when Ag is deposited at higher temperatures. For deposition at 550 °C sharp spots in the reflection high energy electron diffraction pattern corresponding to an epitaxial orientation with the underlying Si substrate are observed. The presence of a short range order on the oxidized surface apparently influences the crystallographic orientation of the Ag islands. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd.

The shape evolution of MBE grown Si 1xGe x islands on ultraclean reconstructed high-index Si(5 5 12), Si(5 5 7) and Si(5 5 3) surfaces has been studied experimentally and explained using a phenomenological kinetic Monte Carlo (kMC) simulation. We show that a self-assembled growth at optimum thickness leads to interesting shape transformations, namely spherical islands to rectangular rods up to a critical size beyond which the symmetry of the structures is broken, resulting in a shape transition to elongated trapezoidal structures. We observe a universality in the growth dynamics in terms of aspect ratio and size exponent, for all three high-index surfaces, irrespective of the actual dimensions of Ge-Si structures. The shape evolution has been simulated using kMC by introducing a deviation parameter () in the surface barrier term (E D) to take the effect of anisotropic diffusion as one of the plausible mechanisms. © Copyright EPLA, 2012.

The morphological evolution and the effect of growth temperature on size, orientation and composition of molecular beam epitaxy grown Ge-Si islands on Si(5512) surfaces have been investigated in the temperature range from room temperature to 800°C. Two modes of substrate heating, i.e. radiative heating (RH) and direct current heating (DH) have been used. The post-growth characterization was carried out ex situ by scanning electron microscopy, cross-sectional transmission electron microscopy and Rutherford backscattering spectrometry. In the RH case, we found spherical island structures at 600°C with a bimodal distribution and upon increasing temperature, the structures got faceted at 700°C. At 800°C thick (122nm) dome-like structures are formed bounded by facets. While in the case of dc heating, after the optimum critical temperature 600°C, well aligned trapezoidal Si 1xGe x structures with a graded composition starts forming along the step edges. Interestingly, these aligned structures have been found only around 600°C, neither at low temperature nor at higher temperatures. © 2012 IOP Publishing Ltd.

Growth of Ag nanoislands on air-oxidized Si(001), (111) and (110) surfaces has been investigated by reflection high energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and cross-sectional transmission electron microscopy. We have shown that the oriented nanocrystalline Ag, similar to the epitaxial growth of Ag on clean Si surfaces, can be grown on oxide-covered Si surfaces. A thin oxide layer (~ 2-3 nm thick) is formed on ultra-high vacuum (UHV)-cleaned Si surfaces via exposure of the clean reconstructed surface to air. Deposition of Ag was carried out under UHV at different substrate temperatures and monitored by RHEED. RHEED results reveal that Ag deposition at room temperature leads to the growth of randomly oriented Ag islands while, in spite of the presence of the oxide layer between Ag islands and Si, preferred orientations with an epitaxial relationship with the substrate evolve when Ag is deposited at higher substrate temperatures. STM images of the oxidized surfaces, prior to Ag deposition, apparently do not show any order. However, Fourier transforms of STM images show the presence of a short range order on the oxidized surface following the unit cells of the underlying reconstructed Si surface. It is intriguing that Ag nanoislands follow an epitaxial orientational relationship with the substrate in spite of the presence of a 2-3 nm thick oxide layer between Ag and Si. Apparently, the short range order existing on the oxide surface influences the orientation of the Ag nanoislands. © 2011 Elsevier B.V. All rights reserved.

We report the growth of Ge nanostructures and microstructures on ultraclean, high vicinal angle silicon surfaces and show that self-assembled growth at optimum thickness of the overlayer leads to interesting shape transformations, namely from nanoparticle to trapezoidal structures,at higher thickness values. Thin films of Ge of varying thickness from 3 to 12 ML were grown under ultrahigh vacuum conditions on a Si(5 5 12) substrate while keeping the substrate at a temperature of 600°C. The substrate heating was achieved by two methods: (i) by heating afilament under the substrate (radiative heating, RH) and (ii) by passing direct current throughthe samples in three directions (perpendicular, parallel and at 45° to the (110) direction of the substrate). We find irregular, more spherical-like island structures under RH conditions. The shape transformations have been found under DC heating conditions and for Ge deposition more than 8 ML thick. The longer sides of the trapezoid structures are found to be along (110) irrespective of the DC current direction. We also show the absence of such a shape transformation in the case of Ge deposition on Si(111) substrates. Scanning transmission electron microscopy measurements suggested the mixing of Ge and Si. This has been confirmed with a quantitative estimation of the intermixing using Rutherford backscattering spectrometry (RBS) measurements. The role of DC heating in the formation of aligned structures is discussed. Although the RBS simulations show the presence of a possible SiOx layer, under the experimental conditions of the present study, the oxide layer would not play a role in determining the formation of the various structures that were reported here. © 2011 IOP Publishing Ltd.

Real-time electron microscopy observation on morphological changes in gold nanostructures deposited on Si (1 0 0) surfaces as a function of annealing temperatures has been reported. Two types of interfaces with silicon substrates were used prior to gold thin film deposition: (i) without native oxide and on ultra-clean reconstructed Si surfaces and (ii) with native oxide covered Si surfaces. For ≈2.0 nm thick Au films deposited on reconstructed Si (1 0 0) surfaces using the molecular beam epitaxy method under ultra-high vacuum conditions, aligned four-fold symmetric nanogold silicide structures formed at relatively lower temperatures (compared with the one with native oxide at the interface). For this system, 82% of the nanostructures were found to be nanorectangle-like structures with an average length of ≈27 nm and aspect ratio of 1.13 at ≈700 °C. For ≈5.0 nm thick Au films deposited on Si (1 0 0) surface with native oxide at the interface, the formation of a rectangular structure was observed at higher temperatures (≈850 °C). At these high temperatures, desorption of gold silicide followed the symmetry of the substrate. Native oxide at the interface was found to act like a barrier for the inter-diffusion phenomena. Structural characterization was carried out using advanced electron microscopy methods. © 2011 IOP Publishing Ltd.

We report growth of Ge nano/micro structures on ultra clean, high vicinal silicon surfaces of Si(5 5 7) and Si(5 5 12) under two substrate heating conditions: direct current (DC) and radiative heating (RH). These were grown under ultra high vacuum conditions while keeping the substrate at a temperature of 600°C. The results for 10 monolayer (ML) and 12 ML thick Ge deposited on the above surfaces show spherical island structures for RH conditions while aligned trapezoidal structures were observed under DC conditions of heating. We find that the longer side of trapezoid structures are along <110>̄ irrespective of DC current direction. In the case of 10 ML Ge deposited on Si (5 5 7), elongated SixGe1-x nanostructures with an average length of ≈300 nm and a length/width ratio of ≈3.3 have been formed along the step edges. Under similar conditions for 10 ML Ge growth on Si(5 5 12), we found aligned SixGe1-x trapezoidal microstructures of length ≈6.25 μm and an aspect ratio of ≈3.0. Scanning transmission electron microscopy (STEM) measurements showed the mixing of Ge and Si at the interface and throughout the over-layer. Detailed electron microscopy studies (scanning electron microscopy (SEM) and STEM) reveal the structural aspects of these microstructures.

NiO thin films grown on Si(100) substrates by electron beam evaporation, were sintered at 500 °C and 700 °C. The films were irradiated with 120 MeV Au9+ ions. Irradiation had different effects depending upon the initial microstructure of the films. Irradiation of the films at a fluence of 3 × 1011 ions cm-2 leads to grain growth for the films sintered at 500 °C and grain fragmentation for the films sintered at 700 °C. At still higher fluences of irradiation, grain size in 500 °C sintered film decreased, but the same improved in 700 °C sintered film. Associated with the grain size, texturing of the films was also shown to undergo significant modifications under irradiation. © 2010 IACS.

Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time insitu high temperature transmission electron microscopy (with 40ms time resolution), we show the formation of high aspect ratio (≈15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during insitu annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst. © 2009 IOP Publishing Ltd.

Growth of Ag islands under ultrahigh vacuum condition on air-exposed Si(0 0 1)-(2 × 1) surfaces has been investigated by in-situ reflection high energy electron diffraction (RHEED). A thin oxide is formed on Si via exposure of the clean Si(0 0 1)-(2 × 1) surface to air. Deposition of Ag on this oxidized surface was carried out at different substrate temperatures. Deposition at room temperature leads to the growth of randomly oriented Ag islands while well-oriented Ag islands, with (0 0 1) Ag ||(0 0 1) Si , [1 1 0] Ag ||[1 1 0] Si , have been found to grow at substrate temperatures of ≥350 °C in spite of the presence of the oxide layer between Ag islands and Si. The RHEED patterns show similarities with the case of Ag deposition on H-passivated Si(0 0 1) surfaces. © 2009 Elsevier B.V. All rights reserved.

We present a review on the formation of gold silicide nanostructures using in situ temperature dependent transmission electron microscopy (TEM) measurements. Thin Au films of two thicknesses (2.0 nm and 5.0 nm) were deposited on Si (1 1 0) substrate under ultra-high vacuum (UHV) conditions in a molecular beam epitaxy (MBE) system. Also a 2.0 nm thick Au film was deposited under high vacuum condition (with the native oxide at the interface of Au and Si) using thermal evaporation. In situ TEM measurements (for planar samples) were made at various temperatures (from room temperature, RT to 950 °C). We show that, in the presence of native oxide (UHV-MBE) at the interface, high aspect ratio (≈15.0) aligned gold silicide nanorods were observed. For the films that were grown with UHV conditions, a small aspect ratio (∼1.38) nanogold silicide was observed. For 5.0 nm thick gold thin film, thicker and lesser aspect ratio silicides were observed. Selected area diffraction pattern taken at RT after the sample for the case of 5.0 nm Au on Si (1 1 0)-MBE was annealed at 475 °C show the signature of gold silicide formation. © 2009 Elsevier B.V. All rights reserved.

Thin Au films (∼2nm) were deposited on an Si(110) substrate epitaxially under ultra-high vacuum (UHV) conditions in a molecular beam epitaxy (MBE) system. Real-time in situ transmission electron microscopy (TEM) measurements were carried out at various temperatures (from room temperature to 700°C), which shows the formation and growth of aligned gold silicide nanorod-like structures. The real-time selected-area electron diffraction patterns show the presence of silicon and unreacted gold at lower temperatures (up to 363°C), while at higher temperatures only the signature of silicon has been observed. The diffraction analysis from room temperature cooled systems show the presence of gold silicide structures. Around 700 °C, 97% of the nanostructures were found to be aligned nanosilicide-rod-like structures with a longer side of ≈37nm and aspect ratio of 1.38. For a high temperature annealed system (at 600 °C), selected-area diffraction (SAD) and high resolution lattice (after cooling down to room temperature) confirmed the formation of nano- Au 5Si2 structures. The alignment of gold silicide structures has been explained on the basis of lattice matching between the substrate silicon and silicide structures. © 2009 IOP Publishing Ltd.