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CO Gas Sensor based on E-beam Evaporated ZnO, MgZnO and CdZnO Thin Films: A Comparative Study
摘要： This paper reports a comparative study of electron-beam evaporated ZnO, MgZnO and CdZnO thin film based gas sensor. At room temperature (RT), these semiconductive thin films were deposited on Si/SiO2 substrate and an interdigitated pattern of chromium electrode deposited on these films. Device properties such as structural, optical and electrical have been reported and analyzed. The sensors have been tested at different operating temperatures. At 250 ℃, the sensor shows the best response for CdZnO thin films. We have obtained sensor response 4.86 with response time 15 sec for 100 PPM carbon mono oxide (CO) gas concentration for CdZnO thin film. Based on experimental results, Cd-doped ZnO has been found most suitable among these semiconducting metal oxides, when used as a CO gas sensor. A correlation between structural, optical and electrical properties with these thin films has also been established.
关键词： Thin film,ZnO,MgZnO,CO Gas sensor,CdZnO,E-beam evaporation
更新于2025-09-23 15:23:52
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Structural, electrical, optical and thermoelectric properties of e-beam evaporated Bi-rich Bi2Te3 thin films
摘要： Bi-rich Bi2Te3 thin films are prepared at 300 K using e-beam evaporation technique. A source power of 45 W for e-beam was used. Post deposition, these as-deposited Bi-rich Bi2Te3 (Bi-BT-AD) films are annealed at 100 °C (Bi-BT-100), 200 °C (Bi-BT-200) and 300 °C (Bi-BT-300) for 1 h under a pressure of 3 × 10-4 Pa. X-ray diffraction measurements reveal the presence of Bi phase together with crystalline Bi2Te3 indicating the possible presence of Bi-rich Bi2Te3 phase in the Bi-BT-AD film. The broad peaks from Bi2Te3 (015) plane indicates nanocrystalline nature of particles. With annealing, no change in diffraction pattern is observed for Bi-BT-100. However, Bi-BT-200 and Bi-BT-300 films show the emergence of x-ray reflection from unknown phases around 2θ ~ 20° and 47°. This indicates Bi related secondary phase segregation and the thermodynamic instability for the presence of Bi in Bi2Te3 lattice. From Raman studies it is discerned that Bi secondary phase coexist along with the Bi-rich Bi2Te3 nanocrystalline grains. On vacuum annealing Bi-rich Bi2Te3 thin films prevails as evidenced from the p-type electrical characteristics, while excess Bi disappears and converts into an unknown minor phase. The resistivity of all the annealed films are ~ 0.9 × 10-4 Ωcm. The Seebeck coefficients also do not show any change and remain around 33 to 36 μV/K. Thermoelectric properties of Bi-BT-100 exhibit high power factors when measured at different ΔT with a maximum of ~ 17.5 × 10-4 W/K2m for ΔT=100 °C. Thus, unlike the near-stoichiometric thin films, Bi-rich thin films require low temperature annealing (~100 °C) to achieve optimized parameters. Bi-rich Bi2Te3 thin films also show higher power factor compared to the near-stoichiometric thin films. Thus, favourable thermoelectric properties can be achieved at 300 K for temperature sensitive device fabrication using Bi-rich Bi2Te3 thin films.
关键词： Bismuth-rich bismuth telluride,thin films,electron-beam evaporation,power factor.
更新于2025-09-23 15:23:52
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Impact of sulphurization environment on formation of $$\hbox {Cu}_{2}\hbox {ZnSnS}_{4}$$ Cu 2 ZnSnS 4 films using electron beam evaporated stacked metallic precursors
摘要： The superiority of copper zinc tin sulphide (Cu2ZnSnS4; CZTS) over the existing absorber layer materials is inevitable owing to its cheap, non-toxic and earth abundant constituents with high absorption coefficient value. In the present study, CZTS films are prepared by sulphurizing electron beam deposited precursors of glass/Cu/Zn/Sn/Cu and glass/Cu/Sn/Zn/Cu stacking sequences in two different environments i.e., elemental S powder and 5% H2S + N2 gas at different ramping rates. The effect of sulphurization environment and sulphurization ramping rate on the formation of CZTS is investigated using X-ray diffraction and Raman spectroscopy. The morphology and composition of the films are analysed respectively using field emission gun scanning electron microscopy and energy dispersive X-ray spectroscopy. It is observed that films prepared in elemental S powder at a low ramping rate exhibit better crystallinity with less impurity phases. The presence of ZnS is observed in all the films, while the presence of SnS is observed in films prepared with H2S gas alone, thus concluding that sulphurization in the presence of elemental S powder at a low ramping rate is highly favourable for CZTS film formation. CZTS films with minor ZnS impurity with a bandgap of 1.48 eV is successfully fabricated by using a glass/Cu/Zn/Sn/Cu precursor stack.
关键词： ramping rate,Electron beam evaporation,CZTS
更新于2025-09-23 15:22:29
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The effects of thermal annealing on the structural and electrical properties of Zinc Tin oxide thin films for transparent conducting electrode applications
摘要： The as-deposited and annealed Zinc tin oxide (Zn2SnO4) thin films were deposited by electron beam evaporation technique and were characterized for the structural, optical and electrical properties. The x-ray diffraction technique revealed the amorphous nature of as-deposited thin film while the films annealed at 400, 500 and 6000C in air were found to be polycrystalline. The phase change from amorphous to crystalline Zn2SnO4 results in the higher resistance as revealed by resistance versus temperature measurements. From the Hall Effect, the as deposited film shows the electron mobility and carrier concentrations (electron) equal to 33cm2/V.s and 8.361x 1017cm-3 respectively. The agglomeration of grains in annealed thin films are observed by Atomic Force Microscopy (AFM) technique.The peaks in Optical transmission spectra, observed by using the UV-Vis spectroscopy confirm the creation of sub levels between conduction band minimum and valence band maximum after annealing. The band gaps calculated by Tauc plot explore the possibility of shifting the Fermi level towards valence band maximum after thermal annealing.
关键词： Annealing temperature,Zn2SnO4,Band gap,Oxygen vacancies,Electron beam evaporation,TCOs
更新于2025-09-23 15:22:29
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Deposition of ZnS thin films by electron beam evaporation technique, effect of thickness on the crystallographic and optical properties
摘要： Deposition of Zinc sulfide (ZnS) thin films on Si (100) and glass substrates has been performed using electron beam evaporation (EBE) method without annealing. Film structure has been analyzed by XRD, while SEM and AFM have been used to explore the films morphology. Raman spectroscopy has been used to confirm film composition. The stoichiometry has been verified by EDX and XPS techniques. XRD patterns indicated that the films possess a polycrystalline cubic structure with orientations along (111) and (220) planes. The crystallinity has been better with film thickness in the 350–1700 nm range while the RMS roughness increases. Optical properties of the grown films were characterized by optical transmittance measurements (UV–Vis). The deduced energy band gap of the films shows a clear reduction from 3.45 eV to 3.36 eV with increasing film thickness. The evolution of refractive index, extinction coefficient, and dielectric constants with thickness has been investigated from transmittance spectra in the 500–1000 nm wavelength range.
关键词： ZnS,optical characteristics,Thin films,electron beam evaporation
更新于2025-09-23 15:22:29
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Investigation on annealing temperature-dependent optical properties of electron beam evaporated ZnSe thin films
摘要： This research work is devoted to studying optical properties of zinc selenide (ZnSe) thin films deposited by electron beam evaporation technique and annealed at different temperatures in a nitrogen environment. The structural analysis by X-ray diffraction confirmed that the obtained ZnSe films had cubic zinc-blende structure with preferred orientation along plane (111). Based on Swanepoel's envelope method, some important optical parameters such as absorption coefficient, extinction coefficient, refractive index and optical band gap, were evaluated through the transmission spectrum ranging from 300 to 1500 nm at room temperature. The optical band gap increased from 2.52 to 2.65 eV with the increasing annealing temperature. However, both the thickness and refractive index of the films decreased. In addition, the dispersion parameters of the refractive index and energy were also studied by using Wemple-DiDomenico single oscillator model.
关键词： Optical properties,Thin films,Electron beam evaporation,Zinc selenide,Thermal annealing
更新于2025-09-23 15:21:21
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Study on Needles and Cracks of Tin-doped Indium Oxide Tablets for Electron Beam Evaporation Process
摘要： Tin-doped indium oxide (ITO) tablets were used to deposit ITO films on p-GaN layer of light-emitting diodes. Needles and cracks in ITO tablets generated during electron beam evaporation process were deeply investigated. The formation of needles is predominantly resulted from the scanning trace, which is controlled by x and y axes scanning singles. The needles can be eliminated by controlling electron beam scanning trace. The loose microstructure with uniform grains and pores in the ITO tablets results in weak bonding strength, which leads to cracks under the thermal shock of high energy electron beam. A three-dimensional reticulated skeleton structure with strong bonding strength can restrain these cracks.
关键词： needle,crack,ITO,electron beam evaporation
更新于2025-09-23 15:21:01
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Effect of deposition angle on fabrication of plasmonic gold nanocones and nanodiscs
摘要： Metal nanocones can exhibit several strong plasmonic resonances, which are associated with intense and accessible electromagnetic hot spots. They can thus be used to enhance light–matter interactions or to facilitate location-specific sensing while enabling separation of some non-specific contributions towards the sensing signal. Nanocones and similar 3D structures are often fabricated with the use of the so-called self-shading effect, which occurs during the evaporation of a metal film into circular nanowells. Unfortunately, a full description of a successful deposition process with all the essential details is currently missing in literature. Here we present a detailed view of the fabrication of ordered arrays of conical gold nanostructures using electron beam lithography and gold electron beam evaporation. We show that the symmetry of the fabricated nanostructures is influenced by the lateral position of the substrate on the sample holder during the deposition. Off-axis deposition or tilt of the sample leads to asymmetric nanostructures. When the deposited film is thick enough, or the nanowells narrow enough, the entrance aperture is clogged, and nanocones with sharp tips are formed. In contrast, flat-top truncated cones are produced for thinner films or wider nanowells. All these findings help to identify inherent limits for the production of wafer-scale arrays of such non-planar nanostructures. On the other hand, they also suggest new fabrication possibilities for more complicated structures such as mutually connected nanocones for electrically addressable chips.
关键词： Plasmonics,Optical antenna,Nanodisc,Nanocone,Electron beam evaporation,Electron beam lithography
更新于2025-09-23 15:19:57
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Impact of Hydrogen flow rate on physical properties of ZnS thin films: As potential buffer layer in solar cells
摘要： The exceptional need of potential Cd-free buffer layer in thin film solar cell devices motivated us to study the role of post-deposition Hydrogen annealing for the optimization of physical properties of ZnS thin films. The deposited films of thickness 200 nm were hydrogenated within the flow rate range of 50.0–150.0 sccm at 200°C. XRD analysis revealed transformation of amorphous into cubic phase with maximum crystallinity at 150.0 sccm for films deposited on glass substrate while into wurtzite structure for films on ITO substrate with enhanced crystallinity. A mixed phase (cubic and hexagonal) at 150.0 sccm also appeared. Electrical behaviour (I–V) exhibits ohmic nature with maximum carrier concentration at 100.0 sccm. The blue shift in absorption edge and maximum of 95% transmittance were recorded in the visible region with optical energy band gap of 3.41 eV at 150.0 sccm. The reduction in surface roughness is observed in surface topographical analysis while the photoluminescence (PL) study indicated a sharp peak at 2.95 eV with strongest emission for 150.0 sccm attributed to reduction of defects at interstitial sites and passivation of grain boundaries. These results are useful to understand the Hydrogen related impurities in ZnS films and the improvement caused by hydrogenation to physical properties suited for buffer layer in solar cells.
关键词： Buffer layer,ZnS thin films,Hydrogenation,Physical properties,e-beam evaporation
更新于2025-09-23 15:19:57
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Impact of Bi doping on CdTe thin films: Thermal annealing evolution of physical properties for solar cell absorber layer applications
摘要： To mitigate probability of instability and device degradation associated with traditional Cu doping and to tune required band gap as well as to reduce open circuit voltage loss to solar cell device, a study on evolution to the physical properties of Bi-doped CdTe films is reported. Thin films of CdTe:Bi 2% alloy are developed employing electron-beam deposition followed by air annealing. Structural studies reveal that films have preferred crystal growth along (111) plane and with annealing, films turned out to be polycrystalline. Absorbance of films is found to be affected with annealing where 450 °C annealed films show maximum absorbance. The current-voltage measurements show linear relationship reveal to ohmic contacts between the films and transparent conducting oxide substrate and conductivity is observed to be varied with annealing. The atomic force microscopy study indicates an increase in surface roughness with annealing (except for 300 °C). Our findings warrant that the optimized physical properties of CdTe:Bi 2% films annealed at 450 °C may play important role to enhance the solar cell device performance concerned.
关键词： Bismuth doping,Absorber layer,Air-annealing,Thin films,Cadmium telluride,Electron beam evaporation
更新于2025-09-23 15:19:57