Vacuum Deposition Techniques Research Articles

The electrical properties of n-CdS/p-CdTe and n-ZnS/p-CdTe heterojunctions fabricated by a combination of SILAR and vacuum deposition techniques

The paper reports successful fabrication of CdS/CdTe and ZnS/CdTe heterojunctions by a combination of two different deposition techniques viz. successive ionic layer adsorption and reaction (SILAR) and conventional vacuum deposition. The SILAR deposited CdS and ZnS layers formed well adherent and stable heterojunctions with the vacuum deposited CdTe. The electrical characteristics of the heterojunctions were analyzed by thermionic emission model and Cheung's model. The ideality factor, series resistance, barrier height, space charge density and thickness of the depletion region were determined by rigorous I–V, J-V and C–V characterization. The barrier heights of the devices were found to be in the range of 0.8 eV–0.9 eV. The thickness of the depletion region was found to be 5.2 nm and 7.1 nm while the space charge density was found to be 3.6 × 1022 m−3 and 1.59 × 1021 m-3, respectively, for CdS/CdTe and ZnS/CdTe heterojunctions.

Electrodeposition of Cadmium Selenide on Silicon to Integrate the Semiconductors Properties

Monocrystalline silicon has been considered for years among the materials at the base of the macro and micro-electronics industry. At the bulk state silicon is an intrinsic semiconductor whose conductive properties can be easily modulated by using doping agents. This feature combined with high availability and accessible production costs makes it particularly suitable for many applications based on semiconductor technology. With the development of vacuum deposition techniques, it has been possible to create systems that integrate monocrystalline silicon with other materials of technological interest, thus allowing the realization of highly performing devices. However, the use of these techniques is limited by special working conditions and very expensive instruments. An alternative to these techniques is the electrodeposition from aqueous solution. Studies on the deposition of materials of technological interest on gold and silver have been known for several years now. In this work we use the electrodeposition technique, with all the advantages it brings both in terms of costs and deposition quality, on monocrystalline 100 n-type silicon. The study dealt with the co-deposition and alternate deposition of the semiconductor cadmium selenide (CdSe) [1]. First of all, we carried out the electrochemical characterization of the precursors on the substrate to find the optimal conditions (pH and concentrations) for the deposition, then the deposition was performed using two different approaches: co-deposition (both the precursors present in the same solution) and charge controlled alternate deposition of the two components. Finally, deposits were characterized spectroscopically and microscopically: we found that, with the electrochemical method, we obtained to the formation of micro-clusters of CdSe on n-Si. The present study funded by the PRIN Project (“Progetti di Ricerca di Rilevante Interesse Nazionale”), “Novel Multilayered and Micro-Machined Electrode Nano-Architectures for Electrocatalytic Applications (Fuel Cells and Electrolyzers)”, grant number 2017YH9MRK.

Impact of indium doping on the anti-biofilm activity of ZnO thin films against Escherichia coli and Staphylococcus aureus

The proposed research aims to discover the anti-biofilm activity of pure Zinc Oxide and Indium doped Zinc Oxide (In–ZnO) thin films by varying doping concentration of Indium. Thin films of ZnO and In doped Zinc Oxide was successfully synthesized by resistive thermal vacuum deposition technique. Physical property, like the crystallinity and orientation of the deposited thin films, was examined by XRD analysis. Scanning electron microscopy of ZnO and In–ZnO thin film reveals morphological characteristics. Whereas, HRTEM confirmed the polycrystalline nature of thin films while EDX confirmed element composition. AFM shows that the roughness of thin films increase as doping concentration of In increase in ZnO. An improved result of anti-biofilm activity was examined on Indium doped zinc oxide (In–ZnO) thin-film under an optical microscope against Escherichia coli and Staphylococcus aureus . • In–ZnO thin films. • Roughness of thin films. • Anti-biofilm activity.

Optical properties of Red pigment for Dye Sensitized Solar Cells

This work contains a description of the optical properties of Lithol Bordeaux dye thin films. The main use of this dye is for Dye Sensitized Solar Cells (DSSCs). Hence the need to deposit this dye as a thin layer in order to know its optical properties. The films were successfully grown by physical vapor deposition (PVD) technique in a high vacuum on transparent (glass) kept at room temperature during the deposition process. Optical properties were investigated by transmittance and photoluminescence measurements. Strong luminescence was observed around 1,68×107 CPS and a reaching an absorbance band about 100 nm in the visible range.

Fabrication of 128Te thin target for nuclear levels lifetime measurements

Measuring nuclear level lifetimes of pico-seconds and femto-seconds order is important for understanding typical nuclear shapes. To extract such short lifetimes, specially designed thin targets are needed. A thin isotopically enriched 128Te target of thickness ∼ 1.2 mg/cm2 on the thick backing foil of natural gold of thickness ∼ 9.8 mg/cm2 has been prepared for the Doppler shift attenuation method (DSAM) lifetime measurement. The target was made by vacuum deposition technique using the cryogenic pump based Ultra High Vacuum (UHV) chamber available at the Inter University Accelerator Centre (IUAC), New Delhi. In this activity, a specially designed indigenously developed graphite crucible with 1 mm opening was used to minimize material loss and to improve the deposition efficiency of the material. To get the desired thickness of the target, only 20 mg of isotopically enriched 128Te material was used. The quality check of the prepared foil was done by the Energy Dispersive X-ray fluorescence (EDXRF) technique.

Alkyl-Substituted Selenium-Bridged V-Shaped Organic Semiconductors Exhibiting High Hole Mobility and Unusual Aggregation Behavior.

Toward the development of high-performance organic semiconductors (OSCs), carrier mobility is the most important requirement for next-generation OSC-based electronics. The strategy is that OSCs consisting of a highly extended π-electron core exhibit two-dimensional (2D) aggregated structures to offer effective charge transport. However, such OSCs, in general, show poor solubility in common organic solvents, resulting in limited solution processability. This is a critical trade-off between the development of OSCs with simultaneous high carrier mobility and suitable solubility. To address this issue, herein, five-membered ring-fused selenium-bridged V-shaped binaphthalene with decyl substituents (C10-DNS-VW) is developed and synthesized by an efficient method. C10-DNS-VW exhibits significantly high solubility for solution processes. Notably, C10-DNS-VW forms a one-dimensional π-stacked packing motif (1D motif) and a 2D herringbone (HB) packing motif (2D motif), depending on the crystal growth condition. On the other hand, the fabrication of thin films by means of both solution process and vacuum deposition techniques forms only the 2D HB motif. External stress tests such as heating and exposure to solvent vapor indicated that 1D and 2D motifs could be synergistically induced by the total balance of intermolecular interactions. Finally, the single-crystalline films of C10-DNS-VW by solution process exhibit carrier mobility up to 11 cm2 V-1 s-1 with suitable transistor stability under ambient conditions for more than two months, indicating that C10-DNS-VW is one of the most promising candidates for breaking the trade-off in the field of solution-processed technologies.

Physical and optical studies of the novel non-crystalline CuxGe20-xSe40Te40 bulk glasses and thin films

In this research work, the authors devoted their efforts to study the physical and optical properties of the novel CuxGe20-xSe40Te40, CGST (x = 0,5,10,15,20 at.%) matrix. Physical properties of bulk samples and optical properties of thin films of this matrix have been studied. The bulk glassy samples were prepared using the known melt quenching method, while thin-film samples were deposited by vacuum deposition technique under pressure 10−4 Pa. X-ray diffraction examination showed that thin-film samples were deposited in the amorphous state, where no discrete sharp diffraction peaks were formed. Energy-dispersive X-ray spectroscopy exhibited also that there is a good agreement between the experimental results and the selected elemental composition ratios for all samples. The optical properties were studied using the spectrophotometric measurements of transmittance and reflectance spectra within the spectral range 300 nm–2500 nm. The absorption coefficient, the absorption index, optical energy gap, Urbach energy and others have been investigated and discussed on the view of the chemical band approach model. The optical energy gap decreases from 1.208 eV to 1.045 eV, while Urbach energy increases from 0.186 eV to 0.219 eV as Cu ratio increased from zero to 20%. These CGST samples showed very low absorbance nature in the NIR and IR regions. Therefore, they can be used in the applications of optoelectronics devices, infrared imaging, and optical filters and detectors.

Nonlinear optical performance of CdO/InSe Interfaces

In this article, the growth nature, structural and optical properties of CdO/InSe interfaces are investigated. The CdO/InSe interfaces are prepared by the thermal vacuum deposition technique. Structurally, while the CdO exhibited cubic structure, the InSe layer was amorphous in nature. The morphological analyses have shown that the interface is composed of randomly distributed circular grains of average sizes of ∼170 nm. The interfacing of the CdO and InSe resulted in enhancing the light absorbability of CdO by ∼21 times in the IR range. It also showed well aligned conduction bands and valence band offset of 0.72 eV. The Drude-Lorentz modeling of the imaginary part of the dielectric spectra of the CdO/InSe interfaces has shown that the device is suitable for the fabrication of field effect transistors. The drift mobility of free carriers at the interface reached 42.27 In addition, a quality factor larger than 103 is achieved in the IR range indicating the suitability of these optical interfaces to store electromagnetic energy. These properties are important as they shows the applicability of the CdO/InSe interface in solar cells and optoelectronics as optical signal receivers or converters.

Comparative investigation of single-layer and multilayer Nb-doped TiC coatings deposited by pulsed vacuum deposition techniques

Hard-yet-tough coatings are required to protect structural materials, cutting, stamping, and forging tools operating under harsh conditions that combine wear, corrosion, and elevated temperatures. To reveal the high potential of niobium (Nb) as an additive to binary Ti-based coatings, single-layer and multilayer Nb-doped TiC coatings were obtained by pulsed arc evaporation (PAE), electro-spark deposition (ESD) in vacuum, and combination of these methods. Structure, elemental, and phase compositions were studied by means of X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, tribological properties, and electrochemical behavior in 3.5% NaCl solution. Tribological tests were carried out under various conditions, such as applied load (5 and 10 N), medium (air and 3.5% NaCl solution), and counterpart material (Al2O3 and 440C steel). Thin PAE coating (1.8 μm thick) consisted of 2–5 × 50–100 nm (Ti,Nb)C crystallites, elongated in direction of the coating growth, embedded in an amorphous matrix (75% sp2 + 25% sp3-hybridized carbon). Thick ESD coating (20 μm) contained TiC grains uniformly distributed in an eutectic Fe(Co)-Fe2(Ti,Nb) matrix with a minor content of Ti-Ni and γ-Fe phases. The single-layer PAE coating demonstrated superior tribological performance both in air and 3.5% NaCl solution, as well as high oxidation resistance during tribocorrosion tests. As a top layer in the PAE/ESD coating, it provided wear protection of less wear-resistant ESD sublayer. It is assumed that the main benefit of the ESD sublayer in the PAE/ESD coating may be that it provides enhanced toughness and high thickness, which prevents a soft substrate from high stress-induced plastic deformation.

Research progress of tin oxide-based thin films and thin-film transistors prepared by sol-gel method

Transparent conductive oxide (TCO) films and transparent oxide semiconductor (TOS) films have been widely adopted in solar cells, flat panel displays, smart windows, and transparent flexible electronic devices due to their advantages of high transparency and good conductivity and so on. Most of TCO and TOS films are mainly derived from indium oxide, zinc oxide and tin oxide. Among these materials, the In element is toxic, rare and expensive for indium oxide film, which will cause environmental pollution; zinc oxide film is sensitive to acid or alkali etchants, resulting in a poor formation of film patterning; tin oxide film is not only non-toxic, eco-friendly, and cheap but also has good electrical properties and strong chemical stability. Thus, tin oxide has a great potential for developing the TCO and TOS films. At present, the film is prepared mainly by the vacuum deposition technique. The drawbacks of this technique are complex and expensive equipment system, high energy consumption, complicated process and high-cost production. However, compared with the vacuum deposition technique, the sol-gel method has attracted extensive attention because of its virtues such as simple process and low cost. In this paper, we review the development status and trend of TCO and TOS films. First, the structural characteristics, conductive mechanism, element doping theory and carrier scattering mechanism of tin oxide thin films are introduced. Then the principle of sol-gel method and correlative film fabrication techniques are illustrated. Subsequently, the application and development of tin oxide-based thin films prepared by sol-gel method in n-type transparent conductive films, thin-film transistors and p-type semiconductor films in recent years are described. Finally, current problems and future research directions are also pointed out.

Characterization of the silver thin films produced at different substrate temperatures

Introduction: In recent decades, the antimicrobial surfaces/coating properties towards a longlasting microbicidal effect have drawn enormous attention by researchers, they have been developed and used in a wide variety of high-touch hospital devices as a potential approach.
 Methods: In this work, Ag NPs was synthesized by sputtering method at the different annealing temperatures of 100◦C, 200◦C, 300◦C, and 400◦C.
 Results: As a result, the as-synthesized Ag-300 exhibits the highest E. coli antibacterial performance compared with others. This can be attributed to the change of the Ag NPs toxicity based on the growth of nanoparticles during the deposition process related to the Ostwald ripening process, thermal activation and coalescence particles.
 Conclusion: This work provides an essential insight into the antimicrobial activity of Ag NPs-based films synthesized through the vacuum deposition technique, resulting in opening a new approach for enhancing the antimicrobial efficacy and prospects.
 

3D Organic Nanofabrics: Plasma-Assisted Synthesis and Antifreezing Behavior of Superhydrophobic and Lubricant-Infused Slippery Surfaces.

Herein, we present the development of supported organic nanofabrics formed by a conformal polymer-like interconnection of small-molecule organic nanowires and nanotrees. These organic nanostructures are fabricated by a combination of vacuum and plasma-assisted deposition techniques to generate step by step, single-crystalline organic nanowires forming one-dimensional building blocks, organic nanotrees applied as three-dimensional templates, and the polymer-like shell that produces the final fabric. The complete procedure is carried out at low temperatures and is compatible with an ample variety of substrates (polymers, metal, ceramics; either planar or in the form of meshes) yielding flexible and low solid-fraction three-dimensional nanostructures. The systematic investigation of this progressively complex organic nanomaterial delivers key clues relating their wetting, nonwetting, and anti-icing properties with their specific morphology and outer surface composition. Water contact angles higher than 150° are attainable as a function of the nanofabric shell thickness with outstanding freezing-delay times (FDT) longer than 2 h at -5 °C. The role of the extremely low roughness of the shell surface is settled as a critical feature for such an achievement. In addition, the characteristic interconnected microstructure of the nanofabrics is demonstrated as ideal for the fabrication of slippery liquid-infused porous surfaces (SLIPS). We present the straightforward deposition of the nanofabric on laser patterns and the knowledge of how this approach provides SLIPS with FDTs longer than 5 h at -5 °C and 1 h at -15 °C.

Making reversible transformation from electronic to ionic resistive switching possible by applied electric field in an asymmetrical Al/TiO2/FTO nanostructure

Here, the design and fabrication of an asymmetrical Al/TiO2/FTO sandwiched nanostructure is reported by using simple spin-coating and vacuum deposition techniques. This intentionally designed asymmetrical sandwiched nanostructure is suited for nonvolatile memristor that the electronic resistive switching (eRS) and the ionic resistive switching (iRS) can coexist and reversibly transform each other. The coexistence and reversible transformation could be induced and controlled by applied electric field, which means that there is a critical electric field for transformation of two operating modes. That is when the applied electric field is smaller than the critical electric field, the oxygen vacancies cannot form a conductive filament, instead it acts as a trap centers, and the Al/TiO2/FTO memristor presents the eRS operating mode by trapping and detrapping of carriers. Conversely, when the applied electric field is greater than the critical electric field, the electric field induces oxygen vacancies to migrate, and then the Al/TiO2/FTO memristor presents the iRS operating mode by the formation and rupture of the conductive filaments. For that, we have also discussed the corresponding transformation mechanism for the two modes of resistive switching in detail.

Photoelectrochemical performance of MoBiGaSe5 thin films deposited by vacuum deposition technique

In the present investigation nanocrystalline mixed metal chalcogenide (MMC) MoBiGaSe5 thin films were successfully deposited by vacuum evaporation technique. The asdeposited and vacuum annealed MoBiGaSe5 thin films were studied for their optical, structural, morphological, compositional, electrical and photoelectrochemical (PEC) performance. Optical absorption studies revealed that asdeposited and vacuum annealed MoBiGaSe5 thin films showed absorption in the visible region. X-ray analysis of vacuum annealed film shows the phase transition from orthorhombic Bi2Se3 to stoichiometric hexagonal Bi2Se3 phase. The phase transition confirms the formation of hexagonal nanocrystalline MoBiGaSe5 pure phase. SEM images of the asdeposited film showed uniform well defined morphology, besides annealed sample, had diffused granular growth of uniform spheres. HRTEM images showed an average particle size 58 nm, and SAED pattern confirms the single crystalline hexagonal structure of MoBiGaSe5 thin films. EDS confirmed the presence of Mo, Bi, Ga and Se elements and XPS confirms Mo4+, Bi3+, Ga3+ and Se2− oxidation states. The AFM images were in good agreement with SEM images. Asdeposited and annealed MoBiGaSe5 thin film show semiconducting behavior with p-type conductivity. The PEC performance was studied, and it showed efficiency (ɳ) 0.004 and 0.097% of asdeposited and vacuum annealed MoBiGaSe5 thin films respectively.

CuO–ZnO nanocomposite films with efficient interfacial charge transfer characteristics for optoelectronic applications

CuO–ZnO nanocomposite films were synthesized through the oxidation of nanostructured Cu–Zn films deposited by vacuum deposition technique at a relatively high pressure of an inert gas. XRD patterns showed that the film samples were nanocomposites containing nanograins of CuO and ZnO and that the size of the CuO grains decreased with the increase in the Zn atom %. Optical absorption and Raman spectra confirmed the samples to be nanocomposites. The decrease in the activation energy for DC conduction and the enhancement in the photocurrent in the CuO–ZnO nanocomposite films with the increase in the atom % of Zn were attributed to an efficient interfacial charge transfer between the CuO and ZnO grains.

Active-Material-Independent Color-Tunable Semitransparent Organic Solar Cells.

Semitransparent colorful organic solar cells (OSC) provide exciting opportunities for harnessing sunlight as colored windows. Previously, color filter (CF) electrodes on (OSC) were demonstrated via vacuum-deposition techniques, resulting in deposition-induced damage. Thus, we present CF integrated organic photovoltaics (CF-OPVs) using solution-processed TiO2-AcAc as the dielectric component. The noninvasive processing substantially expands the range of usable active materials, allowing the device to display pure and vibrant colors that are independent of the inherent color of the active material and show superior optical and photovoltaic characteristics. These results provide practical pathways to realizing colored semitransparent solar cells.

Synthesis and Characterization of Zinc Selenide Thin Films by Vacuum Deposition Technique

Synthesis and Characterization of Zinc Selenide Thin Films by Vacuum Deposition Technique

Synthesis and Characterization of Cadmium Selenide Thin Films by Vacuum Deposition Technique

Synthesis and Characterization of Cadmium Selenide Thin Films by Vacuum Deposition Technique

Effects of varying ion flux on high vacuum evaporated erbium thin films

For the first time, to the best of our knowledge, a comprehensive study has been carried out to investigate the effects of ion beam on erbium thin films. Thin enriched erbium films with areal density ∼50–200 μg/cm2 sandwiched between carbon films were prepared using the high vacuum deposition technique. The samples were bombarded with fluorine ion beam accelerated to 90 MeV energy using a tandem accelerator. Irradiation time was varied for each sample. Accelerator based characterization technique-Rutherford Backscattered Spectrometry (RBS) was used to study the structural changes induced by ion beam irradiation. The morphology and composition of the samples were studied using Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive x-ray Spectroscopy (EDS), respectively. Comparisons have been drawn between the various samples and with pristine erbium sample. These results show that erbium films are quite stable under energetic ion beam irradiation. This makes their application in various fields dealing with high radiation protection and shielding possible.

Surface Modifications of Dental Implants: An Overview

Osseointegration is the key for long term success of endosseous dental implants. Implant surface properties like surface roughness, surface topography, surface energy and surface composition are the major characters that influence the process of osseointegration. Several methods have been used to optimise implant surface roughness to increase surface area thereby improving the process of osseointegration. Blasting using alumina and titanium dioxide, acid treatment, anodization, and laser peeling are some of the subtractive methods used to optimize implant surface roughness. Additive methods used to coat HA onto the surface of endosseous implants include plasma sprayed HA, vacuum deposition technique, sol-gel and dip coating method, electrolytic process and nano-HA coating. Recently, biomimetic implant surfaces are produced with calcium phosphate coatings under physiological conditions. These coatings are also capable to act as vehicles for osteogenic agents like BMPs, GDFs and biologically active drugs like bisphosphonates, gentamicin, tetracycline, etc.,. The methods used for surface modifications of endosseous dental implants are vast and continuously evolving with the recently developed technologies. This article gives an overview on various surface modifications and current trends followed in the field oral implantology.