Thin films of nanocrystalline 3,4,9,10-perylene-tetracarboxylic-diimide (PTCDI) were prepared on quartz substrates by thermal evaporation technique. The structural properties were identified by transmission electron microscopy (TEM) and the X-ray diffraction (XRD). The optical properties for the films were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500 nm. The optical constants (refractive indexnand absorption indexk) were calculated and found to be independent on the film thickness in the measured film thickness range 117–163 nm. The dispersion energy (Ed), the oscillator energy (Eo), and the high-frequency dielectric constantε∞were obtained. The energy band model was applied, and the types of the optical transitions responsible for optical absorption were found to be indirect allowed transition. The onset and optical energy gaps were calculated, and the obtained results were also discussed.
Transparent and conducting SnO 2 thin film has been produced on quartz substrate using rapid thermal oxidation of pure Sn in air at different oxidation temperature and oxidation time. The transmittance T in the visible and NIR was investigated, the allowed direct energy gap was determined to be 3.18 eV at optimum condition of 600° and 90 s. The dependence of the resistivity on the film thickness and oxidation time has been studied. The optimum thickness of high transmittance and lowest resistivity is about 150 nm for SnO 2 were ρ = 2 × 10-2Ω cm and T = 88%.
Transparent and conducting SnO 2 thin film has been produced on (quartz, ITO, silicon and porous silicon) substrates using rapid photothermal oxidation of pure Sn in air at 600°C oxidation temperature and different oxidation time. The structural, optical, electrical properties, scan electron microscope and atomic force microscope of the prepared films were studied. The transmittance T in the visible and NIR was investigated; the allowed direct energy gap was determined to be 3.18 eV at optimum condition of 600°C and 90 s. The dependence of the resistivity on the film thickness and oxidation time has been studied. The optimum thickness of high transmittance and lowest resistivity is about 150 nm for SnO 2 , where q = 1.7 9 10 -3 X cm and T = 88 %. The sensitivity behaviors of the n-SnO 2 /p-PSi/c-Si-based gas sensor to H 2 and CO 2 gas were investigated. The film sensitivity dependence on the temperature and test gas concentration was tested and the optimum operation temperature was determined at around 250 and 300°C with an applied voltage was constant at 2.5 V.
Near-ideal n- SnO 2/n- Si heterojunction band edge lineup has been investigated with aid of I–V and C–V measurements. The heterojunction was manufactured by rapid thermal oxidation of Sn metal films prepared by thermal evaporation technique on monocrystalline n-type silicon. The experimental data of the conduction band offset ΔEc and valence band offset ΔEc were compared with theoretical values. The band offset ΔEc = 0.55 eV and ΔEv = 1.8 eV obtained at 300 K. The energy band diagram of n- SnO 2/n- Si HJ was constructed. C–V measurements depict that the junction was an abrupt type and the built-in voltage was determined from 1/C2–V plot.
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