Simple Physical Vapor Deposition Research Articles

Binder-free Cu1.9Bi0.1Se@SWCNT hybrid anodes for lithium-ion and sodium-ion batteries

The rapid growth of portable electronic devices, electric vehicles, and grid-scale energy storage systems has accelerated the demand for enhancing existing materials and innovating new materials in rechargeable battery technologies. Li-ion batteries have dominated the energy storage field among the various battery systems. Na-ion batteries have emerged as promising candidates due to their similarities to Li-ion battery chemistry, low cost, and environmental sustainability. This study explores the potential advantages of synthesizing the binder-free Cu1.9Bi0.1Se@SWCNT heterostructure directly on the copper collector surface. A crucial aspect of this research is the intentional use of nanostructuring during synthesis. This technique capitalizes on the benefits of greater surface area, enhanced electron transport, and superior ionic conductivity. The synthesis method not only ensures excellent electrical and mechanical contact with the collector but also omits the need for a binder, offering a potential for improved overall performance in Li-ion and Na-ion batteries. The electrodes were synthesized using a simple and cost-effective physical vapor deposition method. The structural, morphological, and electrochemical properties of the electrodes were characterized. The binder-free Cu1.9Bi0.1Se@SWCNT electrode with 25 % SWCNT content exhibits excellent performance in Li-ion half cells, maintaining a high energy capacity of 556 mAh g−1 at 0.1 A g−1 over 100 cycles and 244 mAh g−1 at 0.5 A g−1 over 750 cycles. However, in the Na-ion battery system, the performance is notably poorer, revealing challenges and limitations. Most likely, the larger size of sodium ions posed difficulties in intercalation within the anode material structure.

Sputtered Silicon-Coated Graphite Electrodes as High Cycling Stability and Improved Kinetics Anodes for Lithium Ion Batteries.

Amorphous Si thin films with different thicknesses were deposited on synthetic graphite electrodes by using a simple and scalable one-step physical vapor deposition (PVD) method. The specific capacities and rate capabilities of the produced electrodes were investigated. X-ray diffraction, scanning electron microscopy, Raman spectroscopy, profilometry, cyclic voltammetry, galvanostatic techniques, and in situ Raman spectroscopy were used to investigate their physicochemical and electrochemical properties. Our results demonstrated that the produced Si films covered the bare graphite electrodes completely and uniformly. Si-coated graphite, Si@G, with an optimal thickness of 1 μm exhibited good stability, with an initial discharge capacity of 628.7 mAhg-1, a capacity retention of 96.2%, and a columbic efficiency (CE) higher than 99% at C/3. A discharge capacity of 250 mAh g-1 was attained at a high current rate of 3C, which was over 2.5 times that of a bare graphite electrode, thanks to the high activated surface area (1.5 times that of pristine graphite) and reduced resistance during cycling.

Low-Vacuum Catalyst-Free Physical Vapor Deposition and Magnetotransport Properties of Ultrathin Bi2Se3 Nanoribbons.

In this work, a simple catalyst-free physical vapor deposition method is optimized by adjusting source material pressure and evaporation time for the reliable obtaining of freestanding nanoribbons with thicknesses below 15 nm. The optimum synthesis temperature, time and pressure were determined for an increased yield of ultrathin Bi2Se3 nanoribbons with thicknesses of 8-15 nm. Physical and electrical characterization of the synthesized Bi2Se3 nanoribbons with thicknesses below 15 nm revealed no degradation of properties of the nanoribbons, as well as the absence of the contribution of trivial bulk charge carriers to the total conductance of the nanoribbons.

Enhanced Photoelectrochemical Response of the ZnO/V2O5 Heterojunction Via Improved Visible-Light Absorption and Charge Carrier Separation

Planar ZnO/V2O5 heterojunctions show excellent photocurrent density and are easy to prepare using a simple physical vapor deposition technique. First, ZnO thin-film photo-electrodes were prepared by radio frequency sputtering, and then their thickness was optimized for improved photoelectrochemical (PEC) response, resulting in an optimum photocurrent density value of ∼0.7 mA/cm2 at 0.61 V vs Ag/AgCl for ZnO thin films deposited for 15 min. Thereafter, ZnO/V2O5 heterojunctions were fabricated by depositing V2O5 thin films for different deposition durations of 10, 20, and 30 min onto ZnO thin-film samples which were already optimized to further improve the PEC performance. The structural, optical, and morphological properties of pristine and heterojunction thin-film samples were investigated by X-ray diffraction, Raman spectroscopy, UV–visible spectroscopy, field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy techniques. The maximum photocurrent density value of 1.56 mA/cm2 at 0.61 V vs Ag/AgCl was obtained for ZnO/V2O5 heterojunction photoanodes, where the top V2O5 layer was deposited by RF magnetron sputtering process which occurred for 20 min. The ZnO/V2O5 heterojunction photocurrent density was nearly twice as compared with that of the pristine ZnO photo-electrode. This improved PEC response of the ZnO/V2O5 heterojunction was due to enhanced visible-light absorption and the formation of a staggered n–n heterojunction, which facilitated the separation of electron–hole pairs at the photo-anode/electrolyte junction.

A low-cost flexible material system made of PANI/graphite for resistive detection and quantitative determination of urea

The designing of low-cost, flexible, and easily degradable sensors with organic materials compositions is a challenging one in recent advancements in sensor technology. In order to develop a high-performance sensing device for urea, polyaniline (PANI) deposited on the surface of graphite (Gr) incorporated cellulose paper substrate has been studied. A graphite layer was formed by using commercially available pencil graphite by gently rubbing on one side of the cellulose paper substrate. A uniform layer of PANI was obtained over the graphite-incorporated cellulose paper by a simple physical vapor deposition technique. The prepared sensor material systems of polyaniline/graphite (PANI/Gr) have been studied by using scanning electron microscopy (SEM), X-ray diffraction analysis, ultraviolet–visible spectroscopy, and Keithley 2450 source meter unit for composition, morphology, optical and charge transport properties respectively. The resistive response of these materials with different molar concentrations of urea was studied through I–V characteristics and a notable urea sensing property has been observed. The PANI/Gr composite prepared on a cellulose substrate evolved as an active sensing material for low-cost, non-enzymatic detection of urea.

Core-Shell Electrocatalysts with Nanocolumnar Pt Thin Film Shell on Carbon Support Core for Polymer Electrolyte Membrane Fuel Cells

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is one of the most promising energy conversion technologies with zero carbon emission, and has received significant attention especially for automotive applications. State-of-the-art PEMFCs use platinum or platinum-alloy nanoparticles distributed on carbon as the electrocatalyst. However, there are still significant challenges for PEMFCs before widespread commercialization including short lifetime and high initial cost mainly originating from the catalyst related issues. Recent research efforts have focused on approaches that would improve catalyst lifetime, reduce its manufacturing cost, and reduce the amount of platinum used without losing activity. In this work, we present a new core-shell electrocatalyst design that can potentially address the challenges of conventional PEMFC catalysts. The design involves a shell of nanocolumnar Pt thin film coated on carbon support core (Pt-TF/C). Pt-TF layers were deposited on carbon powder by high-pressure sputtering (HIPS) and their oxygen reduction reaction (ORR) activity relevant to PEMFCs was investigated. HIPS is a simple physical vapor deposition technique that is scalable and easily applicable to industrial sputter deposition systems, in which atoms come to the substrate surface at different angles to form columnar structures. Pt-TF/C powder samples with various types of carbon were produced and studied to investigate their ORR performance. Electrochemical characterization of the samples was performed by cyclic voltammetry and rotating disk electrode measurements. The Pt-TF-to-carbon mass ratios were measured by quartz crystal microbalance and thermogravimetric analysis. X-ray diffraction analysis showed the presence of Pt on the carbon support. Our preliminary results on specific activity, mass activity, and electrochemically active surface area indicate a promising electrocatalyst durability.

A wide solar spectrum utilization and fast charge carrier transport upon variable GaAs interlayer thickness in ZnPc/GaAs/ZnPc hybrid thin-film structures

The effects of inorganic layer thickness on the photophysical properties of the organic layer in an organic-inorganic hybrid system were investigated in this paper. Photosensitive Zinc Phthalocyanine (ZnPc) and GaAs layers were alternatively stacked through simple physical vapor deposition, and the impact of GaAs layer thickness was explored through structural, optical, and electrical characterization techniques. The strain-induced quantum size effect was evident in the hybrid structure, and it was confirmed in Raman analysis with broad vibration peaks of the GaAs phase, which resulted in a decrease in the GaAs thickness < Bohr radius (RB). In addition, a complementary absorption edge was obtained at 295 nm along with ZnPc absorption features, but GaAs failed to contribute to spectral absorption with its thickness > RB. The decreased photoluminescence intensity and fluorescence decay time of ZnPc after incorporation of GaAs imply that charge transfer from ZnPc to GaAs occurs quickly. The transient photocurrent measurement demonstrates that the current density of hybrid film with GaAs thickness < Bohr radius was significantly increased. As expected, the GaAs with thickness above the Bohr radius is ineffective for improving the photocurrent. Impedance spectroscopy analysis was applied to explore the electrical transport behavior in the hybrid system using a two-electrode system. An ultra-thin GaAs layer noticeably promoted mass transfer at the ZnPc-GaAs interface and increased the conductivity of the hybrid system with the least charge transfer resistance.

Temperature and size dependent mechanical properties of vapor synthesized zinc tungstate nanowires

Monoclinic structured zinc tungstate (ZnWO4) nanowires were synthesized using a simple physical vapor deposition procedure. The nanowires grew along the [001] direction and exhibited faceted surfaces. The Young's modulus of the nanowires was characterized by a resonant method based on laser Doppler vibrometry. The modulus of nanowires with thicknesses greater than ∼120 nm was close to that of their bulk counterparts, whilst the modulus of those with thicknesses in the range of 120 nm–67 nm decreased by ∼10%. Their modulus was also characterized over a temperature range from 300 to 650 K, and a dependency with temperature was observed. The fracture strain of the nanowires was characterized using a bending test based on optical microscope nanomanipulation in ambient atmosphere. The fracture strain of the nanowires slightly increased from 4% to 5% as their widths decreased from 325 to 50 nm, and no evidence of plastic deformation is observed during the direct fracture analysis by transmission electron microscope.

All-inorganic CsPbBr3 thin-film solar cells prepared by single-source physical vapor deposition

Long-term stability and large-area are key to the commercialization of perovskite solar cells, and the all-inorganic perovskite CsPbBr3 has higher stability compared to organic-inorganic hybrid perovskites. In this work, a simple single-source physical vapor deposition (SSPVD) method is proposed for the evaporation of CsPbBr3 crystal powder to deposit high-quality all-inorganic CsPbBr3 perovskite thin films. The results show that the CsPbBr3 thin films prepared by SSPVD are dense and uniform, with high crystallinity and full surface coverage. After annealing optimization, high-quality CsPbBr3 thin films with good crystallinity and uniformity were obtained. The CsPbBr3 thin film has a high visible absorption coefficient and an optical forbidden bandwidth of 2.33 eV. The CsPbBr3 perovskite thin-film solar cells prepared based on the SSPVD method have a photoelectric conversion efficiency (PCE) of 1.37% with good reproducibility and high stability. These results tentatively suggest that SSPVD is a promising method for preparing high-quality all-inorganic perovskite CsPbBr3 thin films for solar cell applications.

Visible-infrared (0.4–20 μ m) ultra-broadband absorber based on cascade film stacks

In this paper, we present a glass-based double-side cascade film stack structure for visible-infrared ultrabroadband absorption. The proposed structure demonstrates an average absorption as high as ∼95% over an ultrawide range of wavelengths from 0.4 μm to 20 μm. The high absorption feature of the different bandgap materials is applied in this absorption device to realize the ultrabroadband absorption, combining with the metal-dielectric-like configuration for those unmatched-admittance wavelengths and the graded index profile arrangement for the 0.4–2.5 μm band. The proposed ultrabroadband absorber shows a great angular tolerance up to 60° with the average absorption of 90% remaining. The proposed approach can have tremendous potential in fields of optical sensing, camouflage, optical imaging, passive cooling, and sustainable power generation, profiting from the good mechanical characteristics of this compact multilayer film structure and the low manufacture costs with the simple physical vapor deposition.

Thickness-dependent properties of ultrathin bismuth and antimony chalcogenide films formed by physical vapor deposition and their application in thermoelectric generators

In this work, a simple cost-effective physical vapor deposition method for obtaining high-quality Bi2Se3 and Sb2Te3 ultrathin films with thicknesses down to 5 nm on mica, fused quartz, and monolayer graphene substrates is reported. Physical vapor deposition of continuous Sb2Te3 ultrathin films with thicknesses 10 nm and below is demonstrated for the first time. Studies of thermoelectrical properties of synthesized Bi2Se3 ultrathin films deposited on mica indicated opening of a hybridization gap in Bi2Se3 ultrathin films with thicknesses below 6 nm. Both Bi2Se3 and Sb2Te3 ultrathin films showed the Seebeck coefficient and thermoelectrical power factors comparable with the parameters obtained for the high-quality thin films grown by the molecular beam epitaxy method. Performance of the best Bi2Se3 and Sb2Te3 ultrathin films is tested in the two-leg prototype of a thermoelectric generator.

Oxygen Reduction Reaction Activity of Nanocolumnar Pt Thin Film Electrocatalyst Deposited on Carbon Support By High Pressure Sputtering

Proton-exchange membrane fuel cell (PEMFC) is one of the most important sources of clean energy especially for automotive applications, which currently utilizes platinum nanoparticles dispersed on carbon (Pt/C) as a catalyst. However, the catalyst activity and durability need to be improved and the cost of the fuel cell need to be reduced for successful commercialization. Extensive research has been done to improve the catalyst activity and durability, reduce the amount of platinum used and reduce its manufacturing cost. Continuous thin film layer approach is a promising candidate for non-conventional catalysts to address these challenges. For this purpose, nanocolumnar Pt thin film (Pt-TF) layers supported on carbon was fabricated by high pressure sputtering (HIPS) and investigated as oxygen reduction reaction (ORR) electrocatalysts for PEMFCs. HIPS is a simple physical vapor deposition method that is scalable and easily applicable to industrial sputter deposition systems, in which atoms come to the substrate surface with oblique angles and form columnar structures. Different Pt-TF/C weight ratios ranging from 5% to 20% and Pt:Ni (1:3) TF/C were studied. Weight loading was controlled by changing the sputter deposition time. X-ray diffraction analysis revealed the existence of Pt and formation of the Pt:Ni alloy on carbon support. Electrochemical characterization of the carbon-supported Pt-TF samples was conducted by cyclic voltammetry and rotating disk electrode measurements in an aqueous perchloric acid electrolyte. The electrochemically active surface area, mass activity and specific activity of the Pt-TF/C samples were found to be increasing as the Pt-TF/C ratio was increased.

Oxygen Reduction Reaction Activity of Nanocolumnar Pt:Ni Alloy Thin Films By High Pressure Sputtering

Self-supported nanocolumnar Pt-Ni alloy thin films (TFs) with different Pt:Ni compositions and Pt mass loadings were fabricated by high pressure sputtering (HIPS) on a microporous layer (MPL)-like surface composed of carbon particles in order to mimic the catalyst-coated gas diffusion layer (gas diffusion electrode) in a membrane electrode assembly and investigated as oxygen reduction reaction (ORR) electrocatalysts for polymer electrolyte membrane fuel cells. HIPS is a simple physical vapor deposition method that is scalable and easily applicable to industrial sputter deposition systems. At high working gas pressures, columnar and less-dense structures are formed because of angular distribution of sputtered atoms that leads to a shadowing effect. Cauliflower-like microstructures were observed from scanning electron microscopy imaging. X-ray diffraction and quartz crystal microbalance analysis revealed that by simply changing the relative deposition power between Pt and Ni source, different Pt:Ni compositions can be achieved. Benchtop cyclic voltammetry and rotating disk electrode measurements were performed for electrochemical characterization of the Pt:Ni-TF/MPL-like-layer/glassy-carbon samples in an aqueous perchloric acid electrolyte. The electrochemically active surface area (ECSA) ranged between 22-42 m2/g for varying Pt:Ni compositions. Lower Pt mass loadings showed a higher ECSA likely due to smaller nanocauliflower diameters, while the ORR activity of all compositions increased as the Pt mass loading is increased. The catalytic performance of the Pt:Ni-TFs increased in the order of 3:1 < 1:1 < 1:3 with the 1:3 films exhibiting a specific activity of 1781 µA/cm2 and mass activity of 0.66 A/mg, indicating efficient catalyst utilization. The Pt:Ni-TFs were found to exhibit higher ORR activity than traditional high surface area carbon supported Pt nanoparticles, elemental Pt nanorods, and Pt-Ni nanorods.

Catalytic Growth of 1D ZnO Nanoneedles on Glass Substrates Through Vapor Transport

In this study, one-dimensional (1D) zinc oxide (ZnO) nanoneedles are successfully fabricated on a Ag catalyst-coated glass substrate through simple physical vapor deposition via thermal evaporation of zinc (Zn) powder in the presence of oxygen (O2) gas at a low growth temperature of 450°C. The growth rate and diameter of ZnO nanoneedles increase as a function of varying silver (Ag) film thicknesses and argon (Ar) flow rates. Detailed structural investigations confirm that the synthesized nanoneedles have high crystallinity with a hexagonal wurtzite structure, and they preferentially grow along the c-axis orientation. This approach provides a simple and cost-effective method for the synthesis and controlled growth of 1D nanostructures, which can be useful in solid-state devices and various optoelectronic applications.

Highly Sensitive Humidity Sensor Based on Oblique Carbon Nanoplumes.

In this work, we fabricated three carbon nanoplume structured samples under different temperatures using a simple hot filament physical vapor deposition (HFPVD) process, and investigated the role of surface morphology, defects, and graphitic content on relative humidity (RH) sensing performances. The Van der Drift growth model and oblique angle deposition (OAD) technique of growing a large area of uniformly aligned and inclined oblique arrays of carbon nanoplumes (CNPs) on a catalyst-free silicon substrate was demonstrated. The optimal growing temperature of 800 °C was suitable for the formation of nanoplumes with larger surface area, more defect sites, and less graphitic content, compared to the other samples that were prepared. As expected, a low detection limit, high response, capability of reversible behavior, and rapid response/recovery speed with respect to RH variation, was achieved without additional surface modification or chemical functionalization. The holes’ depletion has been described as a RH sensing mechanism that leads to the increase of the conduction of the CNPs with increasing RH levels.

Growth and thermal properties of various In2Se3 nanostructures prepared by single step PVD technique

In2Se3 nanostructures have attracted much attention due to their potential applications in diverse areas, such as solar energy conversion, thermoelectric power generation, phase change random access memories, photodetectors, and optoelectronics in the visible region. In the present work, we have fabricated various In2Se3 nanostructures on SiO2/Si substrate using a simple and single-step physical vapor deposition (PVD) method, without using metal seed layer on the substrates. Morphology, structure and phase of the as-grown In2Se3 nanostructures have been carried out using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, respectively. In addition, we have also explored thermal properties of In2Se3 nanostructures on SiO2/Si substrate using temperature and power dependent Raman spectroscopy. Further, the thermal conductivity of nanoparticles, nanospheres, and rod like flowers at room temperature were found to be ∼37.6, ∼39.5, and ∼15.6 W/m-K, respectively. This work suggests an effective way to form various novel nanostructures, opening up a new scenario to understand the vibrational properties and electron-phonon interactions of In2Se3 nanostructures.

HIT Solar Cell With V20x Window Layer

ABSTRACTIn the conventional crystalline silicon heterojunction solar cell with the intrinsic thin layer structure (the HIT solar cell), a p-doped thin film silicon or its alloy (pDTF-Si/A) is used as the hole collecting window layer. However, the parasitic absorbance in the pDTF-Si/A window layer, and the toxic, explosive diborane gas used for p-doping are limiting factors for achieving HIT cells with reduced processing costs and / or higher efficiencies. In this work, pDTF-Si/A is replaced by V2Ox, which is deposited by a simple physical vapor deposition technique. Due to the wide band gap of V2Ox, the HIT solar cell with the V2Ox window layer generates a higher short-circuit current density than the reference conventional HIT cell under 1 sun, and achieves an open-circuit voltage of 0.7 V. Furthermore, the charge carrier lifetime and pseudo-efficiency values of the HIT solar cell with the V2Ox window layer indicate that this cell has the potential to outperform the conventional HIT cell in terms of the power conversation efficiency under the standard test conditions.

Topological Crystalline Insulator SnTe/Si Vertical Heterostructure Photodetectors for High-Performance Near-Infrared Detection.

Due to the gapless surface state and narrow bulk band gap, the light absorption of topological crystalline insulators covers a broad spectrum ranging from terahertz to infrared, revealing promising applications in new generation optoelectronic devices. To date, the photodetectors based on topological insulators generally suffer from a large dark current and a weaker photocurrent especially under the near-infrared lights, which severely limits the practical application of devices. Owing to the lower excitation energy of infrared lights, the photodetection application of topological crystalline insulators in the near-infrared region relies critically on understanding the preparation and properties of their heterostructures. Herein, we fabricate the high-quality topological crystalline insulator SnTe film/Si vertical heterostructure by a simple physical vapor deposition process. The resultant heterostructure exhibits an excellent diode characteristic, enabling the construction of high-performance near-infrared photodetectors. The built-in electric field at SnTe/Si interface enhances the absorption efficiency of near-infrared lights and greatly facilitates the separation of photogenerated carriers, making the device capable of operating as a self-driven photodetector. The as-grown SnTe film acts as the hole transport layer in heterostructure photodetectors, promoting the transport of holes to electrode and reducing electron-hole recombination effectively. These merits enable the SnTe/Si heterostructure photodetector to have a high responsivity of 2.36 AW-1, a high detectivity of 1.54 × 1014 Jones, and a large bandwidth of 104 Hz in the near-infrared wavelength, which makes the detector have a promising market in novel device applications.

Catalytic growth of one-dimensional single-crystalline ZnO nanostructures on glass substrate by vapor transport

Novel one-dimensional single-crystalline ZnO nanorod and nanoneedle arrays on a Cu catalyst layer-coated glass substrate were investigated via a simple physical vapor-deposition method by thermal evaporation of Zn powder in the presence of O2 gas. The ZnO nanorods and nanoneedles were synthesized along the c-axis growth direction of the hexagonal crystal structure. The diameter and growth rate of the high-quality and well-oriented one-dimensional ZnO nanostructures is achieved as a function of varying growth temperature and growth time. This study serves as the basis for further research on the growth of 1D ZnO nanostructures on a cost-effective glass substrate and at low temperature.

Silicon based solar cells using a multilayer oxide as emitter

In this work, n-type silicon based solar cells with WO3/Ag/WO3 multilayer films as emitter (WAW/n-Si solar cells) were presented via simple physical vapor deposition (PVD). Microstructure and composition of WAW/n-Si solar cells were studied by TEM and XPS, respectively. Furthermore, the dependence of the solar cells performances on each WO3 layer thickness was investigated. The results indicated that the bottom WO3 layer mainly induced band bending and facilitated charge-carriers separation, while the top WO3 layer degraded open-circuit voltage but actually improved optical absorption of the solar cells. The WAW/n-Si solar cells, with optimized bottom and top WO3 layer thicknesses, exhibited 5.21% efficiency on polished wafer with area of 4 cm2 under AM 1.5 condition (25 °C and 100 mW/cm2). Compared with WO3 single-layer film, WAW multilayer films demonstrated better surface passivation quality but more optical loss, while the optical loss could be effectively reduced by implementing light-trapping structures. These results pave a new way for dopant-free solar cells in terms of low-cost and facile process flow.