Influence of thickness and annealing temperature on structural and electrical properties of Te/Si heterojunction

Abstract Heterojunctions are fabricated by depositing tellurium films on n-type single (n-Si) wafers by the method of vacuum evaporation.Te thin films were prepared on glass substrate to study the X-ray diffraction.The X-Ray Diffraction and measurement of the electrical properties of the Te films at room temperature with rate of deposition equal to 80 nm/sec for different thicknesses (400-800) nm and different annealing temperatures (373and 423) K were also studies . The A.C conductivity a.c() of Te films with different thicknesses and annealing temperatures has been investigated as a function of frequency and temperatures. The type of charge carriers, carrier concentration (nH) and Hall mobility (H) have been estimated from Hall measurements. The current –voltage and capacitance–voltage measurements in the dark as well as illumination was done for Te thin films. We can observe that the depletion layer width (W) increases with increasing of the annealing temperature which is due to the decreasing in the carrier concentration which leads to a decrease of the capacitance. The variation of built-in potential (Vbi) may be due to the improvement in the structure of the film. The ideality factor and tunneling constant for Te/Si Heterojunction were also studies as a function of thickness and annealing temperatures

Effect of annealing temperature on structural and optical properties of Cr2O3 thin films by PLD

In the present work, pulsed laser deposition (PLD) technique was applied to a pellet of Chromium Oxide (99.999% pure) with 2.5 cm diameter and 3 mm thickness at a pressure of 5 Tons using a Hydraulic piston. The films were deposited using Nd: YAG laser λ= (4664) nm at 600 mJ and 400 number of shot on a glass substrate, The thickness of the film was (107 nm). Structural and morphological analysis showed that the films started to crystallize at annealing temperature greater than 400 oC. Absorbance and transmittance spectra were recorded in the wavelength range (300- 4400) nm before and after annealing. The effects of annealing temperature on absorption coefficient, refractive index, extinction coefficient, real and imaginary parts of dielectric constant were also study. It was found that all these parameters decrease as the annealing temperature increased to 500 °C, while the energy gap after annealing increase from 3.4 eV to 3.85 eV

Preparation and characterization of mixed SnO2:CdO thin films as gas sensor

In this study, tin oxide (SnO2) and mixed with cadmium oxide (CdO) with concentration ratio of (5, 10, 15, 20)% films were deposited by spray pyrolysis technique onto glass substrates at 300ºC temperature. The structure of the SnO2:CdO mixed films have polycrystalline structure with (110) and (101) preferential orientations. Atomic force microscopy (AFM) show the films are displayed granular structure. It was found that the grain size increases with increasing of mixed concentration ratio. The transmittance in visible and NIR region was estimated for SnO2:CdO mixed films. Direct optical band gap was estimated for SnO2 and SnO2 mixed CdO and show a decrease in the energy gap with increasing mixing ratio. From Hall measurement, it was found that all the films prepared possess n-type carriers of the charge. The maximum sensitivity of SnO2:CdO mixed films toward NO2 gas was achieved at (10) mixed concentration ratio of CdO at the optimal operating temperature 200°C and maximum sensitivity is equal to (101.75%) with response time (14.6 s) and recovery time (57.0 s)

STRUCTURAL AND OPTICAL PROPERTEIS OF ZnS, PbS, ZnxPb1-xS AND PbZnxS1-x THIN FILMS

In this work we used the chemical spray pyrolysis technique to prepare ZnS, PbS, PbZn1-xSx, and PbxZn1-xS, thin films with (x = 0.01, 0.02) at glass substrate at 280˚C, 230˚C, 270˚C and 270˚C respectively. And also study the optical and structural properties.The result of X-ray diffraction obtained that the films are polycrystalline and have cubic with hkl (111) and wurtize with hkl (100) phases for ZnS films, the phase for PbS films is cubic with hkl (200) and the phases for PbxZn1-xS and PbZn1-xSx. are cubic with hkl (200)The lattice constants (a) which were calculated 5.939A˚, for PbS films, 3.36 A˚ and 5.44 A˚ for wurtize and cubic of ZnS films respectively, 5.92A˚for ZnxPb1-xS films with x = 0.02, and 5.921A˚for PbZnxS1-x films with x = 0.01Also the absorption spectra used in the range (200 nm – 1100 nm) to calculate the optical energy gap which is decrease with increase the film thickness for all the films prepared by this technique.The values of energy gap were determined between (1.58 – 1.78 eV) for PbS films, (2.9 – 3.1eV) for ZnS films, The energy gap of ZnxPb1-xS films in the range (2.4 – 2.9(eV and (2.38– 2.75 eV for x = 0.02 and x = 0.01 respectively and The energy gap of PbZnxS1-x (1.57 – 1.8( eV and (1.4 – 1.6( eV for x = 0.02 and x = 0.01 respectively.The optical constants, such as refractive index (n) increase with increase the film thickness, while the extinction coefficient (k) decrease with increase the thickness for all the films except ZnS films which are inversely. And the dielectric constants (εr, εi) have the same behavior of refractive index (n) and extinction coefficient (k) respectively

Effect of CuI concentration on structural and optical properties of PVA: CuI nanocomposites

The nanocomposite on the base of synthesis Copper iodide nanoparticles and polyvinyl alcohol (PVA/CuI) with different concentration of CuI were obtained using casting technique. PVA/CuI polymer composite samples have been prepared and subjected to characterizations using FTIR spectroscopy, The FTIR spectral analysis shows remarkable variation of the absorption peak positions with increasing CuI concentration. The obtained results by X-ray diffraction indicated the formation of cubic CuI particles. The effects of CuI concentrations on the optical properties of the PVA films were studied in the region of wavelength, (190-1100) nm. From the derivation of Tauc's relation it was found that the direct allowed transitions was more probable in PVA/ CuI nanocomposite. The results indicate that the obtained values of optical absorption edge, and energies band gap decreases from 4.05 to3.89 eV for direct transitions with the increasing salt contents

Structural and optical properties of ZnS, PbS, Zn₁_-xPb_xS, Zn_xPb₁_-xS and PbZn_xS₁_-xthin films

380-386The chemical spray pyrolysis technique (CSPT) to prepare ZnS, PbS, PbxZn1-xS, (x=0 to 1), PbZn1-xSx and PbxZn1-xS, thin films with (x = 0.01, 0.02) at glass substrate, has been used. The result of X-ray diffraction obtained that the films are polycrystalline and have cubic with hkl (111) and wurtize with hkl (100) phases for ZnS films, the phase for PbS films is cubic with hkl (200) and the phases for PbxZn1-xS, Pb1-xZnxS and PbZnxS1-x are cubic with hkl (200). The lattice constants (a) have been calculated as 5.939Å for PbS films, 3.36Å and 5.44Å for wurtize and cubic of ZnS films, respectively, 5.91 to 6.2Å as x varied from 0 to 1 for Zn1-xPbxS,5.92Å for ZnxPb1-xS films with x = 0.02, and 5.921Å for PbZnxS1-x films with x = 0.01. The absorption spectra used in the wavelength range 200-1100 nm to calculate the optical energy gap which is found to decrease with increase in the film thickness for all the films prepared by this technique. The values of energy gap have been determined and it was between (1.58-1.78 eV) for PbS films, (2.9-3.1eV) for ZnS films. The energy gap of ZnxPb1-xS films in the range (2.4-2.9) eV and (2.38-2.75) eV and of PbZnxS1-x it was (1.57-1.8) eV and (1.4-1.6) eV for x = 0.02 and x = 0.01, respectively as the thickness increases. The optical constants, such as refractive index (n) and extinction coefficient (k) increase and decrease with increase in the film thickness, respectively for all the films except ZnS films which are having inverse properties. The dielectric constants (εr, εi) have the same behaviour of refractive index (n) and extinction coefficient (k), respectively

Some electrical properties of PVA:PEG/MnCl2 thin film composites

PVA:PEG/MnCl2 composites have been prepared by adding (MnCl2) to the mixture of the poly vinyl alcohol (PVA) and poly ethylene glycol (PEG) with different weight percentages (0, 2, 4, 6, 8 and 10) wt.% by using casting method. The type of charge carriers, concentration (nH) and Hall mobility (μH) have been estimated from Hall measurements and show that the films of all concentration have a negative Hall coefficient. In D.C measurement increase temperature leads to decrease the electrical resistance. The D.C conductivity of the composites increases with the increasing of the concentration of additive particles and temperature. The activation energy decreases for all composites with increasing the concentration of the additive particles. The A.C conductivity increases with increasing of the frequency and the concentration of MnCl2 particles. The A.C electrical properties show that the dielectric constant and dielectric loss of the composites decrease with increasing of the frequency

Structural and optical properties for PVA- PEG-MnCl2 composites

Polymer films of PEG and PVA and their blend with different concentrations of MnCl2 (0, 2, 4, 6 and 10 %.wt) were study using casting technique. The X-ray spectra of pure PEG, PVA and PVA:PEG films and with addition of 2% concentrations from (MnCl2) show amorphous structures. The results for FTIR show the interaction between the filler and polymer blend results in decreasing crystallinity with rich amorphous phase. This amorphous nature confirms the complexation between the filler and the polymer blend. The optical properties of (PVA:PEG/MnCl2) contain the recording of absorbance (A) and explain that the absorption coefficient (α), refractive index (n), extinction coefficient (ko) and the dielectric constants (real and imaginary part) increase with increasing the concentration of Composite (PVA:PEG/MnCl2). The optical energy gap for electrons transitions both are direct and indirect allowed

Hydrogen sulfide sensors based on PANI/f-SWCNT polymer nanocomposite thin films prepared by electrochemical polymerization

Hydrogen sulfide (H2S) gas sensors in the form of thin films based on polyaniline (PAN) incorporated with various concentrations of functionalized single wall carbon nanotubes (f-SWCNT) were prepared by electrochemical polymerization of Aniline monomer with sulfuric acid in an aqueous solution. Surface morphology of the thin film nanocomposites was investigated by Field Emission Scanning Electron Microscopy (FE-SEM) and revealed that the f-SWCNTs were almost uniformly distributed on the surface of the host PANI matrix. The X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Hall effect measurements were used to characterize the synthesized PANI/f-SWCNT nanocomposites. The Hall measurements reveal the p-type conductivity. The grown FTIR band at 1145 cm−1 with the increase of the f-SWCNT content evidence a formation of charge transfers due to a remarkable interaction between PANI and f-SWCNTs. The response of this nanocomposite film towards the H2S gas was investigated by monitoring the change in the electrical resistance with the time in the presence of 30% H2S at different operating temperatures. The sensing analysis showed that the sensitivity increased with f-SWCNT content in the PANI matrix. The rapid response/recovery times toward the H2S gas, at 50 °C, was achieved for a PANI/0.01% f-SWCNT nanocomposite sample. Keywords: Conductive polymer, PANI, Nanocomposites, f-SWCNT, H2S gas senso