Electron Beam Evaporation Technique Research Articles

Reflective Full‐Color Structural Colors with High Brightness and High Purity Based on Ge2Sb2Se4Te1 Chalcogenide Film

AbstractThis study proposes a general strategy for constructing an asymmetric Fabry–Perot structure based on an ultra‐thin composite absorber, Ni/Ge2Sb2Se4Te1, to produce reflective full‐color structural colors with high brightness and purity. The composite absorber effectively enhances the strong interference effect of thin film, which can significantly reduce the reflection bandwidth of the target band and the reflectivity of the non‐target band. Under the premise of optimizing the five‐layer base structure, full‐color structural colors can be tuned by only changing the thickness of the LaTiO3 layer. Using the ion‐assisted electron beam evaporation technique, a simple and efficient film deposition process, six color devices (namely red, orange, yellow, green, blue, and purple) are successfully prepared with reflection peaks exceeding 90%. The chromaticity coordinates of the proposed high‐purity red, green, and blue (RGB) samples are (0.554, 0.339), (0.280, 0.600), and (0.164, 0.075), respectively. These coordinates are fairly close to the standard RGB color coordinates used in liquid crystal displays. This device has a simple structure with a novel material combination and a low production cost, which makes it feasible for mass production using just one coating run process. It has excellent application potential in various fields such as micro‐nano displays, anti‐counterfeiting measures, reflective color filters, and decorations.

Thermochromic VO[formula omitted] thin film from electron beam evaporated V[formula omitted]O[formula omitted]/Ni/V[formula omitted]O[formula omitted] and V[formula omitted]O[formula omitted]/Co/V[formula omitted]O[formula omitted] multilayer stack system

The oxygen–vanadium system presents different equilibrium phases amongst which monoclinic and tetragonal forms of VO2 exist below and above the phase transition temperature of 68 °C. The structure can be explained by pure Mott phase transition with Peierls electron-lattice distortion giving ultrafast transformation of the semiconducting monoclinic VO2 to metallic rutile structure. Hence, practical applications in technology can be explored such as; switching devices, thermal relays and energy management, sensors and actuators, electrochromic and photochromic memories. In this study, VO2 thermochromic thin films were deposited on a quartz glass substrate by electron beam evaporation technique in ultrahigh vacuum at room temperature using sandwich structured V2O5/metal (Ni, Co)/V2O5 multilayer target followed by post-annealing at 500 °C under vacuum. The morphology and crystal structure were investigated by X-ray diffraction, Ultraviolet/Visible/Near Infrared spectrophotometry, and scanning electron microscopy analyses. The sandwich structure effectively regulates the stoichiometry and polymorphs of the material. It was observed that the polymorph of the films switch from VO2 (B) to VO2 (M) when the Ni and Co middle layer reached 7 nm and 10 nm respectively. For the aforementioned thicknesses of the Ni and Co layers, the V2O5/Ni/V2O5 and V2O5/Co/V2O5 multilayers showed thermochromic properties. For V2O5/Ni (7 nm)/V2O5 and V2O5/Co (10 nm)/V2O5 multilayer films, the temperature-dependent spectral transmission measurements show the change in optical range of ∼ 65% and ∼ 43% respectively after the phase transition at wavelength 2500 nm. Transmission measurements of VO2 thin films, were determined at temperatures below and above the phase transition temperature in both the visible and the near-infrared ranges of the electromagnetic spectrum. The temperature-dependent optical transmittance measurement for V2O5/Co (10 nm)/V2O5 multilayer films shows that the multilayer exhibits thermochromic properties and has higher phase transition temperature.

Pompom 3D flower like carbon-based Mn3O4 thin film electrodes for high performance supercapacitors

Manganese oxides have received a lot of attention as positive electrode materials for supercapacitors, but they still present challenges due to their weak electrical conductivity, lack of electroactive sites, and slow charge transfer kinetics. Herein, utilizing the electron beam evaporation technique, we effectively create pompom 3D flower-like C/Mn3O4 particles on Au/Ti/SiO2/(textured) Silicon (ATS) substrates with a few nanometers thickness. High accessibility to active species is provided by the linked carbon with Mn3O4 and the flower-shaped particles with multiple petals, which further enhance charge transfer kinetics. As a result, C/Mn3O4 thin film electrodes showed outstanding cycling stability of 89% even after 10,000 cycles and a reversible capacity of 1452 Fg−1 at 1 mVs−1 scan rate. The C/Mn3O4 thin film-based electrodes improved electrochemical performance is attributable to their unique surface topology.

Fast switching photodetector based on HfO2 thin film deposited using electron beam evaporation technique

Fast switching photodetector based on HfO2 thin film deposited using electron beam evaporation technique

Flexible interdigitated symmetric solid-state micro-supercapacitors with higher energy density for wearable electronics

Planar interdigitated solid-state supercapacitors are one of the most promising energy storage devices as they offer the merit of fast ionic transportation with minimal charge transfer resistance due to the narrow gap between the interdigitated isolated electrode fingers. This study focuses on fabricating flexible symmetric solid-state supercapacitor devices with high energy and power densities. Specifically, a symmetric SnO2‖PVA-LiClO4‖SnO2 solid-state supercapacitor (SSC) device was fabricated using the electron beam evaporation (e-beam) technique on thin, flexible electrodes in interdigitated (ISSC) and stacked (SSSC) configurations and their electrochemical performances were compared. The ISSC exhibiting pseudo-capacitive behavior achieved a maximum volumetric capacitance of 439.5 F cm−3 at a scan rate of 5 mV S−1. Quantitative calculation of the device's charge storage dynamics reveals that the diffusion-limited Lithium insertion processes predominantly contribute to the capacitance of ISSC. Comparatively, the ISSC outperformed the SSSC with a diffusion coefficient of 2.55 × 10−13 m2s−1 and ac conductivity of 2.2 × 10−2 S m−1, demonstrating excellent energy density and power density values. Furthermore, the ISSC with no adverse effect on its capacitance even when bent at various angles suggesting its suitability for flexible wearable electronic devices.

Glancing angle deposition of helical manganese oxide nanostructures on the glass substrate and study the optical nonlinearity by Z-scan technique

Helical manganese oxide nanostructures have been deposited on glass substrate by glancing angle deposition along with electron-beam evaporation technique. X-ray diffraction analysis, FESEM images, and FTIR spectroscopy confirmed the successful growth of the nanostructured thin film. The surface morphology and roughness of the deposited helical manganese oxide thin film were considered using the 2-D and 3-D AFM images. The optical constants along axes a, b, and c have been calculated from the effective medium approximation of Bruggeman. The refractive indices were found to be equal for helical manganese oxide nanostructures along a- and b-axes and greater than the refractive index along c-axis at λ < 600 nm; while these results are reversed for wavelengths greater than 600 nm. The same variations were observed for the extinction coefficients. The Z-scan measurements under continuous-wave (CW) laser irradiation at 532 nm showed a positive sign for both the nonlinear absorption coefficient and nonlinear refractive index of nanostructured helical manganese oxide demonstrating the attendance of induced absorption process and self-defocusing phenomena, respectively. We computed a 3rd-order nonlinear optical susceptibility, χ(3), equal to 0.042 esu that suggests the glancing angle deposited helical manganese oxide nanostructures with a strong nonlinear optical response can be a good candidate to develop nanophotonic devices.

Structural and microstructural investigation of Sm and Sn doped BaTiO3

(Ba0.9Sm0.1) (Sn0.05Ti0.95) O3 (BSST) ceramic powders were synthesized by solid state reaction route and were pelletized and sintered at 1673 K for 4 h. The BSST thin film was also prepared by electron beam evaporation technique by using the sintered pellets. X-ray diffraction of the BSSTO confirmed that the material has formed in crystalline nature and also in single phase. Raman spectroscopy was used to study the morphology, structure and phase transition behaviour of BSST bulk as well as thin film. The Raman analysis indicated that the film formed at 973 K by electron beam evaporation is less crystalline than that of the bulk BSST due to inadequate substrate temperature.

Structural and electrical investigation of BLT films deposited at different times using electron beam evaporation technique

Structural and electrical investigation of BLT films deposited at different times using electron beam evaporation technique

Amorphous-crystalline phase transformation induced changes in linear and non-linear optical properties of Te/As2Se3 bilayer thin films

The current work describes the amorphous state to crystalline state transition upon diffusion of the top Te layer into the bottom As2Se3 layer at 200 °C annealing temperature. The Te/As2Se3 bilayer thin films were prepared by electron beam (e-beam) evaporation technique. The XRD study confirms the amorphous to crystalline phase transformation. The UV–Visible spectroscopy data shows significant changes in both linear and non-linear optical properties due to the diffusion of Te into As2Se3 upon thermal annealing. The phase transformation behaviour of the Te/As2Se3 bilayer thin films can be utilized in various optoelectronic applications.

Polyaniline-Based Infrared Dynamic Patterned Encoder with Multiple Thermal Radiation Characteristics.

A high-level infrared dynamic patterned encoder (IR-DPE) possesses prospective applications for energy-harvesting and information, but a simple and reliable method for fabrication remains challenging. Herein, we first report an IR-DPE with multiple thermal radiation characteristics based on polyaniline (PANI). Specifically, the electron-beam evaporation technique is introduced to obtain the divanadium pentoxide (V2O5) coating, and then the V2O5 film acts as an oxidant to drive in situ polymerization of the PANI film. During the process, we experimentally explore the relationship between the thickness of V2O5 and the emissivity of PANI to obtain up to six emissivity levels and achieve the IR pattern integrated into multiple thermal radiation characteristics. The device shows multiple thermal radiation characteristics at the oxidized state, realizing a pattern visible with the IR camera and the same thermal radiation properties at the reduced state, leading to the pattern concealed in the IR regime. In addition, the highest emissivity tunability of the device is to be tuned from 0.40 to 0.82 (Δε = 0.42) at 2.5-25 μm. Meanwhile, the device exhibits a maximum temperature control of up to 5.9 °C. The results show the enormous potential of IR-DPEs for IR information transfer and thermal management.

Thickness dependent field emission study of LaB6 coated Si nanowire arrays

A simple physical metal mask is efficiently employed to obtain an array of silicon (Si) nanowires (Si-NWs) on a Si substrate grown using the hot filament chemical vapor deposition route. Well adhered and uniform coating of different thicknesses (20 and 50 nm) of lanthanum hexaboride (LaB6) on Si-NWs was obtained using electron beam evaporation technique. The thickness of LaB6 coating was estimated from ellipsometry measurement. Structural, morphological, and chemical properties of the LaB6 coated Si-NWs (LaB6@Si-NWs) arrays were revealed using x-ray diffraction, field emission scanning electron microscope, transmission electron microscope, Raman spectroscopy, and x-ray photoelectron spectroscopy. Field electron emission characteristics of pristine Si-NW array and LaB6 coated Si-NWs array emitters were studied in planar diode configuration at a base pressure of 1 × 10−8 mbar. The values of turn-on field (current density ∼1 μA/cm2) were observed as ∼2.2, 1.2, and 1.6 V/μm for pristine Si-NWs, LaB6@Si-NWs_20, and LaB6@Si-NWs_50 array emitters, respectively. Furthermore, maximum emission current densities of ∼1276.81, 2763.64, and 2231.81 μA/cm2 have been extracted from the pristine Si-NWs, LaB6@Si-NWS_20, and LaB6@Si-NWS_50 array emitters at an applied field of 3.1, 2.7, and 2.7 V/μm, respectively. The LaB6@Si-NWS_20 array emitter demonstrated superior FEE properties as compared to the pristine Si-NWs and LaB6@Si-NWS_50 emitters. Furthermore, LaB6@Si-NWS_20 emitter depicted very good emission current stability tested at a preset value of 1 μA over a duration of 3 h. The enhanced FEE performance exhibited by the LaB6@Si-NWs_20 array emitter is attributed to reduction in effective work function and enhanced electron tunneling probability across the LaB6–Si interface.

Thin films of solid electrolyte lithium sulfate deposited by e-beam evaporation

Fabrication of lithium sulfate (Li2SO4) thin films has been successfully attempted by the electron beam evaporation technique, and the deposition conditions were systematically optimized to get stable Li2SO4 thin films. The structural, optical, and electrical properties of the fabricated Li2SO4 thin films were investigated using X-ray diffraction, scanning electron microscope, vibrational spectroscopy techniques, optical transmission spectroscopy, and electrical conductivity measurements. The as-deposited Li2SO4 thin films were X-ray amorphous, although they exhibited Bragg peaks corresponding to Li2SO4 when annealed. The fundamental vibrational modes of sulfate anions in thin films were observed through FT-IR and Raman spectroscopy studies. The ionic conductivity value for the thin film was found to be 2.03 × 10-8 S cm−1 at 373 K, which is of three orders of magnitude higher than that of the bulk.

Bias dependent NDR in TiO2/NiO heterojunction diodes

TiO2/NiO thin film heterojunction diodes are fabricated using electron beam evaporation and DC sputtering techniques. Three different thicknesses of NiO (58, 82, and 160 nm) are combined with a TiO2 film of about 80 nm thick. The common device configuration is FTO/TiO2/NiO/Au with a 4 mm sq. device area. The thickness dependent diode I-V characteristics were analyzed; with the increase in thickness, the diode knee voltage, series resistance, and ideality factor have reduced. All the devices exhibit a high diode ideality factor, which means the diode currents are not limited by drift, diffusion, or recombination at the space charge region. The high ideality factor points to the presence of interface states, spatial inhomogeneities, or tunneling in the devices. Further, the bias dependent negative differential resistance (NDR) in I-V characteristics and the presence of an anomalous peak in C-V characteristics were analyzed, which claimed the presence of interfacial trap states, defects, or tunneling in the diodes. The Fowler-Nordheim tunnel model was applied to the devices and the field enhancement factors were calculated as −14.3, −9.3, and −9.2 for the diodes in the increasing order of thickness. The tunneling phenomenon was confirmed as trap-assisted indirect tunneling. Also, the temperature dependence of NDR was studied.

Growth and characterization of Cobalt Oxide thin films

Thin films of cobalt were deposited on glass substrates at room temperature using an electron beam evaporation technique. Formation of different cobalt nanostructures has been carried out by controlled thermal oxidation of the as-deposited Co films in controlled ambient condition. Oxidation temperature was varied within a range up to 700 °C. Structure and morphology of the oxide films along with their chemical and electrical properties have been investigated using various surface characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and I-V measurements. All results are in good correlation and suggest that the CoO phase is only stable for a lower oxidation temperature below 400 °C whereas Co3O4 phase usually appears at higher oxidation temperature. Moreover, the average crystallite size of the oxide nano-particles increases with the oxidation temperature and duration. Electrical measurement shows that resistance of cobalt oxide thin films decreases with an increase in oxidation temperature and duration. All these findings can be explained in terms of thermal diffusion related to different surface morphologies and grain size effects.

Comparison of Sputtered and Evaporated Vanadium Pentoxide Thin Films for Resistive Microbolometer Application

V2O5 thin films have made impressive progress in the development of resistive microbolometers. The challenging parameters for microbolometers are the active material selection and the deposition methods. It might be a more promising way to achieve a good performance of the devices. The present work deals with the V2O5 thin films fabricated on soda lime glass substrates by using e-beam evaporation and magnetron sputtering techniques at a substrate temperature of 200 °C. Afterward, samples were annealed at 300 and 400 °C for 1 h to obtain uniform and stoichiometric thin films. X-ray Diffraction (XRD) showed that the thin films deposited by magnetron sputtering were amorphous in nature, even after annealing at elevated temperatures; however, the thin films fabricated by the electron beam evaporation technique show crystalline nature, which was improved by annealing. XRD also revealed various mixed phases of VOx in electron beam-deposited films. Optical properties were determined using UV-Visible spectroscopy, which showed a decrease in transmittance from 81% down to 57% by increasing the annealing temperature. Similarly, the band gap calculated for electron beam evaporated and magnetron sputtered V2O5 thin films was observed in the range of 1.41 to 2.25 eV. Rutherford backscattering (RBS) was performed to determine the thickness and composition of the films. Slight variations have been observed in intended and deposited thicknesses of films fabricated by e-beam and sputtering techniques. Structural properties revealed by Field Emission Scanning Electron Microscope (FESEM) were found to be the uniform, compact and dense surface of the as-deposited and 300 °C annealed samples. However, annealing at 400 °C changed the surface morphology into nanorods in e-beam and plate-like structures in the sputtered film. EDS proved the elemental concentration of vanadium and oxygen in these V2O5 thin films. Electrical properties were investigated using the Hall measurement technique which showed better conductivity of sputtered films than e-beam deposited films. It can be concluded that the cost-effective and reliable microbolometers infrared (IR) sensors can be fabricated using annealed sputtered films.

Curvature modulated structural and magnetic properties of CoO/Co thin films deposited onto 2-D nanosphere array

The importance and applications of nanoscale magnetic storage devices has been of current interest owing to the extensive research interest in magnetic nanocaps. Continuing their research trend, we have attempted to synthesize and characterize an important isolated magnetic nanocaps system constituting Co and its oxide. CoO/Co thin films were deposited onto self-assembled arrays of polystyrene (PS) nanospheres (∼600 nm diameter) under ultra-high vacuum environment using electron beam evaporation technique. The magnetic and structural properties of these nanostructures were then compared with those of simultaneously deposited films on bare Si substrate (referred to as reference film). The studied film and the reference film were grown in polycrystalline manner as observed from X-ray diffraction measurements while their roughnesses as observed from X- ray reflectivity were quite different. X- ray reflectivity showed that for the reference films well defined Kiessig oscillations appeared suggesting low roughness in the deposited films, while the films on PS followed the curvature of underlying nanospheres and thus have very high roughness resulting in the disappearance of Kiessig oscillations. Magnetic measurements exhibited a drastically high coercivity when the substrate was changed from flat (Si) to curved one (PS). As the film thickness was increased, the coercivity first showed a slight decrement (4.92 kA/m) and beyond 40 nm film thickness, it showed some enhancement (14.2 kA/m). The exchange bias measurements also showed interesting results with variation in film thickness. Co 10 nm film deposited on PS showed negative exchange bias of −127 kA/m which decreased to −26 kA/m in 100 nm film. The overall results were explained by correlating the magnetic and microstructural properties of the thin films as a function of thickness.

The morphology and magnetic properties of iron nanoclusters decorated multiwall carbon nanotubes

Vapor phase growth of magnetic nanoclusters on different substrates alters their physical, chemical, and magnetic properties. In this work, DC magnetron sputtering with inert gas condensation (IGC) technique was used to produce iron (Fe) based nanoclusters on multiwall carbon nanotubes (MWCNTs) and silicon (Si) substrates. For comparison, simple electron beam evaporation technique was used to deposit Fe on the same type of substrates. We observed that surface of the electron beam evaporation sample was oxidized from Fe to γ-Fe2O3 when exposed to air. IGC growth Fe/Si sample exhibited a magnetic negative exchange bias. Core level binding energy (BE) and the valance band maximum (VBM) shifts were affirmed the formation of a semi-metallic phase. There was substantial enhancement in the saturation magnetization in the IGC sample up to five times compared to the evaporated sample which can be applied to the magnetic applications.

PbS and PbO Thin Films via E-Beam Evaporation: Morphology, Structure, and Electrical Properties.

Thin films of lead sulfide (PbS) are being extensively used for the fabrication of optoelectronic devices for commercial and military applications. In the present work, PbS films were fabricated onto a soda lime glass substrate by using an electron beam (e-beam) evaporation technique at a substrate temperature of 300 °C. Samples were annealed in an open atmosphere at a temperature range of 200–450 °C for 2 h. The deposited films were characterized for structural, optical, and electrical properties. Structural properties of PbS have been studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and Rutherford backscattering spectrometry (RBS). The results of XRD showed that the PbS thin film was crystalline in nature at room temperature with cubic crystal structure (galena) and preferential (111) and orientation (022). The morphology of the thin films was studied by FESEM, which also showed uniform and continuous deposition without any peel-off and patches. EDS analysis was performed to confirm the presence of lead and sulfur in as-deposited and annealed films. The thickness of the PbS film was found to be 172 nm, which is slightly greater than the intended thickness of 150 nm, determined by RBS. Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) spectroscopy revealed the maximum transmittance of ~25% for as-deposited films, with an increase of 74% in annealed films. The band gap of PbS was found in the range of 2.12–2.78 eV for as-deposited and annealed films. Hall measurement confirmed the carriers are p-type in nature. Carrier concentration, mobility of the carriers, conductivity, and sheet resistance are directly determined by Hall-effect measurement. The as-deposited sample showed a conductivity of 5.45 × 10−4 S/m, which gradually reduced to 1.21 × 10−5 S/m due to the composite nature of films (lead sulfide along with lead oxide). Furthermore, the present work also reflects the control of properties by controlling the amount of PbO present in the PbS films which are suitable for various applications (such as IR sensors).

Growth and characterization of electron beam evaporated NiO thin films for room temperature formaldehyde sensing

Herein, we report the formaldehyde gas sensing performance of NiO thin films deposited by the electron beam evaporation technique. NiO thin films were grown over glass substrates by the variation of deposition temperature from room temperature (RT) to 500⁰C. The structure, chemical composition and morphological studies were conducted by XRD, FESEM, EDS, AFM, XPS, RBS and HRTEM techniques. The XRD characterization revealed the formation of NiO in the polycrystalline phase with the face-centered cubic structure without impurity phases. The surface and morphological characterization confirmed the growth of the NiO thin layer and the homogeneous distribution of Ni and O elements on the surface of the films. The optical transmittance increased with the rise in deposition temperature. The optical band gap was estimated using Tauc relation and it was shown a decreasing trend with the rise in deposition temperature. The electrical characteristics of thin films were carried out using Hall measurements and presented. The developed gas sensors tested at room temperature have displayed good selectivity towards formaldehyde with a low detection limit of 10 ppm. The NiO thin film sensor prepared at a deposition temperature of 400⁰C has exhibited a short response and recovery time of 25 s and 9 s respectively towards 50 ppm concentration of formaldehyde. The detailed formaldehyde sensing mechanism for p-type NiO thin films was discussed. • E-beam evaporated NiO thin films were deposited by varying the substrate temperature. • The developed NiO films were tested to detect various VOCs at room temperature. • NiO sensor (400⁰C) has exhibited enhanced formaldehyde sensing performance. • The response and recovery times were determined to be 25 s and 9 s towards 50 ppm. • The sensing mechanism involved in redox reactions was projected.

Growth and Characterization of Al (111) Thin Film on Piezoelectric Wafers for SAW Device Fabrication for Space Applications

Surface Acoustic Wave (SAW) filters provide precise frequency filtering in RF and IF range with a tiny footprint. Metallic thin films are the essence of such modern SAW filter technology. However, SAW filters realized using NiCr/Al thin films are limited to power levels of ~5 dBm at RF frequencies. This limitation on power level is due to the acousto-migration phenomenon in thin films at higher power levels. In order to enhance the power durability of SAW filters, the preferred oriented growth of Al along (111) crystallographic direction is one of the methods to reduce acousto-migration. This paper explores the growth and characterization of different metallization schemes (NiCr/Al &amp; Ti/Al) on different piezoelectric wafers to achieve oriented Al (111) film growth. Metallic thin films were deposited using electron beam evaporation technique. High Resolution X-Ray Diffraction (HR-XRD) and Four Point Probe Method were used for crystallographic characterization and Sheet Resistance (SR) measurement, respectively. Atomic Force Microscopy (AFM) and surface profiler were used to characterize the surface morphology of the deposited films. FWHM of 4.12 degree of rocking curve on Al (111) peak has been achieved for Ti/Al metal film deposited on ST-X Quartz piezoelectric wafer along with low sheet resistance of 124 mΩ/sq. A deposition rate of 1 Å/s for Ti and 7 Å/s for Al at a deposition temperature of 100 °C gave the best FWHM value for Al (111) orientation on ST-X Quartz wafer. Space qualification tests were also successfully performed on Ti/Al metalized wafers under extreme environmental conditions. The results obtained in this work demonstrate the suitability of Ti as an under layer to grow preferred oriented Al film along (111) orientation and thus to be used in the fabrication of high-power SAW devices for space applications.