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Effects of Sn doping on the optoelectronic properties of reactively evaporated In4Se3 thin films
摘要： Polycrystalline In4Se3: Sn thin films are prepared on glass substrate by reactive evaporation under a vacuum of 10?5 mbar. The characterizations of the samples are done using XRD, FESEM, XPS and UV-Vis-NIR spectrophotometer. The optical band gap shift of the sample, above the carrier concentration of 1.833 × 1017 cm?3, is well described by Burstein-Moss model. The resistivity of the samples is found to decrease as a result of Sn incorporation. Our results show that in all samples, impurity scattering and lattice vibration scattering are the main factors affecting the electrical properties. Photoconductivity studies at room temperature show that visible photoresponsivity of the films increases with increase in Sn concentration. These improvements in optoelectronic properties facilitate the usefulness of such films in device applications.
关键词： Sn doped In4Se3 thin films,Reactive evaporation,Burstein-moss effect
更新于2025-11-21 11:01:37
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Effect of Na doping on structural and optical properties in Cu2ZnSnS4 thin films synthesized by thermal evaporation method
摘要： Quaternary chalcogenide Cu2ZnSnS4 (CZTS) compound, a potential material for application as absorber layer in thin film solar cells, is synthesized by direct melting of the constituent elements taken in stoichiometry compositions. Alkali element Na was incorporated into CZTS thin films synthesized by thermal evaporation method, in order to further improve the structural and optical properties. X-Ray diffraction (XRD), Raman spectroscopy, Energy dispersive spectrometry and optical spectrophotometry were used to characterise the phase purity and optical properties. It showed that the diffusion of Na ions is uniform in the films after annealing. XRD analysis showed that CZTS films possess polycrystalline structure with [221] preferred orientation. Na ions incorporation in CZTS thin films could improve the cristallinity, the graine size and the absorption coefficient. For CZTS: Na 5%, optical results revealed higher absorption coefficient (>105 cm-1) and direct optical band gap of 1.56 eV with p-type conductivity.
关键词： Semiconductors,Sodium doping,Structural properties,Optical properties,Copper zinc tin sulfide,Thin films,Thermal evaporation
更新于2025-09-23 15:23:52
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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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Investigation of gamma irradiation effects on the properties of CdS/p-Si heterostructure
摘要： Cadmium sulfide (CdS) thin films were deposited on p-type Si substrate by thermal evaporation to fabricate the CdS/p-Si heterojunction. Gamma irradiation has been used to modify the microstructural, optical and electrical characteristics of CdS/p-Si heterojunction of various doses in the range (0–80 kGy). X-ray diffraction measurements of the gamma irradiated show the reduction in crystallinity of the CdS thin films. While scanning electron microscope images depicted the average CdS particle size was found to be increased with increasing the gamma irradiation dose. Photoluminescence results revealed that at the specific dose of gamma irradiation was found to create the yellow emission in interstitial sites to the valence band. The I–V characteristics showed the current transport properties effected by the different gamma doses. The values of barrier height, saturation current and ideality factor for the CdS/p-Si heterostructure varied due to the causes like inhomogeneities in the interfacial, defect density, charge distribution on interfacial and interfacial layer thickness after gamma irradiation. The gamma irradiation induced effects and the possible mechanism in CdS/p-Si heterojunction is discussed.
关键词： Heterostructure,Diffuse reflectance,Photoluminescence,Gamma irradiation,Thermal evaporation
更新于2025-09-23 15:23:52
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Effect of thickness and post deposition annealing temperature on the structural and optical properties of thermally evaporated molybdenum oxide films
摘要： In this paper, the influence of thickness and post deposition annealing temperature on thermally evaporated molybdenum oxide films has been studied. The X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) are used for crystal structural and surface morphological characterization of the films, respectively. The XRD analysis showed that the presence of α-MoO3 and MoO2 crystalline phase of the films annealed at elevated temperature ~ 250 °C after deposition. The optical constants are determined from UV–Vis transmission spectra. The optical band gap and Urbach energy is found to be temperature dependent. The refractive index of the films is estimated by the optical method as well as cross-sectional SEM image analysis. It is found that the refractive index of the films increases from ~ 1.70 to 2.03 with the decrease in film thickness from ~ 2.9 to 1.7 μm. It is also observed that the refractive index decreased from ~ 2.03 to 1.61 with the increase in post deposition annealing temperature from room temperature (RT) to ~ 250 °C. Moreover, extinction coefficient, optical conductivity, porosity, and film density are investigated as a function of source-substrate distance and post deposition annealing temperature. The Photoluminescence (PL) properties of the films are also investigated by recording spectra under the excitation wavelength at 250 nm.
关键词： Optical constants,Molybdenum oxide,X-ray diffraction,Thermal evaporation,Scanning electron microscope
更新于2025-09-23 15:22:29
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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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A New, Specular Reflection-Based, Precorneal Tear Film Stability Measurement Technique in a Rabbit Model: Viscoelastic Increases Tear Film Stability
摘要： PURPOSE. To develop a safe, noninvasive, noncontact, continuous in vivo method to measure the dehydration rate of the precorneal tear film and to compare the effectiveness of a viscoelastic agent in maintaining the precorneal tear film to that of a balanced salt solution. METHODS. Software was designed to analyze the corneal reflection produced by the operating microscope’s coaxial illumination. The software characterized the shape of the reflection, which became distorted as the precorneal tear film evaporated; characterization was accomplished by fitting an ellipse to the reflection and measuring its projected surface area. Balanced salt solution Plus (BSS+) and a 2% hydroxypropylmethylcellulose viscoelastic were used as the test agents. The tear film evaporation rate was characterized and compared over a period of 20 minutes in 20 eyes from 10 New Zealand white rabbits. RESULTS. The ellipse axes ratio and surface area were found to decrease initially after each application of either viscoelastic or BSS+ and then to increase linearly as the tear film began to evaporate (P < 0.001) for eyes treated with BSS+ only. Eyes treated with BSS+ required 7.5 ± 2.7 applications to maintain sufficient corneal hydration during the 20-minute test period, whereas eyes treated with viscoelastic required 1.4 ± 0.5 applications. The rates of evaporation differed significantly (P < 0.043) between viscoelastic and BSS+. CONCLUSIONS. The shape and surface area of the corneal reflection are strongly correlated with the state of the tear film. Rabbits’ corneas treated with viscoelastic remained hydrated significantly longer than corneas treated with BSS+.
关键词： evaporation,corneal hydration,precorneal tear film stability,viscoelastic,balanced salt solution
更新于2025-09-23 15:22:29