The investigation of structural, electrical, and optical properties of thermal evaporated AgGaS 2 thin films (original) (raw)
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Effects of Temperature on the Structural and Optical Preperties of AgGaSe2 Thin Films
Journal of Bangladesh Academy of Sciences, 2010
In this study, AgGaSe 2 (AGS) thin films were formed onto cleaned glass substrates by using the stacked elemental layer (SEL) deposition technique in vacuum. The films were prepared at the post-deposition annealing temperature from 100 to 350°C for 15 min duration. The atomic composition of the films was measured by energy dispersive analysis of X-ray (EDAX) method. The films ascertain the compositional uniformity. The X-ray diffraction (XRD) has been employed to study the structure of the films. The structures of the films are found to be polycrystalline in nature. The lattice parameters, grain size, strain and dislocation densities of the films were calculated. Optical characteristics of the films were ascertained by spectrophotometer in the photon wavelength ranging between 300 and 2500 nm. The transmittance was found to increase with the increase of annealing temperature. The transmittance falls steeply with decreasing wavelength. It revealed that AGS films have considerable absorption throughout the wavelength region from 400 to 800 nm. The optical band gap energy has been evaluated. Two possible direct allowed and direct forbidden transitions have been observed for all the AGS films in visible region. The former varied from 1.67 to 1.75 eV and the later from 2.05 to 2.08 eV, depending on the post-deposition annealing temperature of the films.
Annealing effect on structural and electrical properties of AgGaSe2 thin films
Indian Journal of Pure & …, 2011
Structural, thermo-electrical and electrical properties of AgGaSe 2 (AGS) thin films prepared in vacuum onto glass substrates by stacked elemental layer (SEL) deposition technique have been studied. The films were annealed at 100 to 350°C for 15 min. The atomic composition of the films has been measured by energy dispersive analysis of X-ray (EDAX) method. The structural and thermo-electrical properties of the films have been ascertained by X-ray diffraction (XRD) and the hot-probe method, respectively. The electrical properties of the films are measured by standard dc method using a liquid nitrogen cryostat. The structural, thermo-electrical and electrical properties have been investigated as a function of different annealing temperature. The X-ray diffraction (XRD) reveals that the films were polycrystalline in nature. The lattice parameters, grain size, strain and dislocation densities of the films have been calculated. The thermoelectric power indicates the presence of p-type majority carriers. The electrical conductivity of the films has been found to vary from 1.40×10 −5 to 2.18×10 −2 (Ω-cm) −1 as temperature varies between -173 and 100°C. The activation energies vary from 43.60 to 94.70 meV as annealing temperatures vary between 350 and 100°C. Probable identities of the origin of AGS films have been obtained by using these activation energies. The dominance of grain boundary effect has been ascertained by applying the Seto's model.
Applied Surface Science, 2009
Polycrystalline AgGaSe 2 thin films were deposited by using single crystalline powder of AgGaSe 2 grown by vertical Bridgman-Stockbarger technique. Post-annealing effect on the structural and morphological properties of the deposited films were studied by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDXA) measurements. XRD analysis showed that as-grown films were in amorphous structure, whereas annealing between 300 and 600 8C resulted in polycrystalline structure. At low annealing temperature, they were composed of Ag, Ga 2 Se 3 , GaSe, and AgGaSe 2 phases but with increasing annealing temperature AgGaSe 2 was becoming the dominant phase. In the as-grown form, the film surface had large agglomerations of Ag as determined by EDXA analysis and they disappeared because of the triggered segregation of constituent elements with increasing annealing temperature. Detail analyses of chemical composition and bonding nature of the films were carried out by XPS survey. The phases of AgO, Ag, Ag 2 Se, AgGaSe 2 , Ga, Ga 2 O 3 , Ga 2 Se 3 , Se and SeO 2 were identified at the surface (or near the surface) of AgGaSe 2 thin films depending on the annealing temperature, and considerable changes in the phases were observed. ß
Some physical investigations on Ag2S thin films prepared by sequential thermal evaporation
Synthetic Metals, 2005
Ag 2 S thin films have been prepared on glass substrates by the sequential thermal evaporation technique. X-ray diffraction analysis shows that the films annealed at Ta = 250 • C in argon atmosphere are well crystallised in the -Ag 2 S phase with crystallinity preferentially oriented towards (1 0 3) direction. Microprobe analysis shows that a nearly stoichiometric composition is obtained under such annealing temperature. The optical properties of the films are investigated using spectrophotometric measurements of transmittance T(λ) and reflectance R(λ) in the wavelength range 500-2000 nm. The refractive and absorption indexes, n and k, of Ag 2 S thin films are calculated from the values of the measured transmittance and reflectance. The study of the absorption coefficient of these films versus incident energy revealed that the value of the band gap energy is of the order of 1.1 eV. For the first time, a photovoltaic effect is reported using Ag 2 S as absorber.
Optical properties of polycrystalline AgxGa2−xSe2 (0.4⩽x⩽1.6) thin films
Solar Energy Materials and Solar Cells, 2007
Polycrystalline thin films of Ag x Ga 2Àx Se 2 (0.4pxp1.6) were prepared onto cleaned glass substrates by the stacked elemental layer (SEL) deposition technique. All the films were annealed in situ at 300 1C for 15 min. The compositions of the films were measured by energy-dispersive analysis of X-ray (EDAX) method. The structural and optical properties of the films were ascertained by X-ray diffraction (XRD) and UV-VIS-NIR spectrophotometry (photon wavelength ranging from 300 to 2500 nm), respectively. The influence of the composition on the optical properties of the material has been investigated. Microstructural perfection is quite evident from the abrupt descent around specific energy of photons in the transmittance spectra. Stoichiometric or slightly silver-deficient films show optimum electron transition energy and minimum sub-band gap absorption.
Deposition and characterization of layer-by-layer sputtered AgGaSe 2 thin films
Applied Surface Science, 2011
Sputtering technique has been used for the deposition of AgGaSe 2 thin films onto soda-lime glass substrates using sequential layer-by-layer deposition of GaSe and Ag thin films. The analysis of energy dispersive analysis of X-ray (EDXA) indicated a Ga-rich composition for as-grown samples and there was a pronounce effect of post-annealing on chemical composition of AgGaSe 2 thin film. X-ray diffraction (XRD) measurements revealed that Ag metallic phase exists in the amorphous AgGaSe 2 structure up to annealing temperature 450 • C and then the structure turned to the single phase AgGaSe 2 with the preferred orientation along (1 1 2) direction with the annealing temperature at 600 • C. The surface morphology of the samples was analyzed by scanning electron microscopy (SEM) measurements. The structural parameters related to chalcopyrite compounds have been calculated. Optical properties of AgGaSe 2 thin films were studied by carrying out transmittance and reflectance measurements in the wavelength range of 325-1100 nm at room temperature. The absorption coefficient and the band gap values for as-grown and annealed samples were evaluated as 1.55 and 1.77 eV, respectively. The crystalfield and spin-orbit splitting levels were resolved. These levels (2.03 and 2.30 eV) were also detected from the photoresponse measurements almost at the same energy values. As a result of the temperature dependent resistivity and mobility measurements in the temperature range of 100-430 K, it was found that the decrease in mobility and the increase in carrier concentration following to the increasing annealing temperature attributed to the structural defects (tetragonal distortion, vacancies and interstitials).
Optical and electrical characterization of AgInS2 thin films deposited by spray pyrolysis
Materials Science and Engineering: B, 2010
Silver indium sulfide (AgInS 2) thin films have been prepared by spray pyrolysis (SP) technique using silver acetate, indium acetate, and N, N-dimethylthiourea as precursor compounds. Films were deposited onto glass substrates at different substrate temperatures (T s) and Ag:In:S ratios in the starting solutions. Optical transmission and reflection as well as electrical measurements were performed in order to study the effect of deposition parameters on the optical and electrical properties of AgInS 2 thin films. X-ray diffraction measurements were used to identify the deposited compounds. It was found that different compounds such as AgInS 2 , Ag 2 S, In 2 O 3 , and In 2 S 3 can be grown only by changing the Ag:In:S ratio in the starting solution and T s. So that, by carefully selecting the deposition parameters, single phase AgInS 2 thin films can be easily grown. Thin films obtained using a molar ratio of Ag:In:S = 1:1:2 and T s = 400 • C, have an optical band gap of 1.9 eV and n-type electrical conductivity with a value of 0.3 −1 cm −1 in the dark.
Photoconductive response of polycrystalline p-AgGaSe2 thin films
Solid State Communications, 1991
Photoconductivity response spectra of polycrystalline p-AgGaSe2 thin films are reported. The peak and shoulders observed in the photoconductivity spectra are attributed to transitions from valence sub-bands to the conduction band. From the room temperature spectra, the band gap energies, spin-orbit and crystal-field parameters are determined. The variation of photocurrent with applied bias voltage, illumination intensity and temperature are also studied.
Physico-Chemical Characterization of Sprayed ?-Ag2S Thin Films
physica status solidi (a), 2000
Silver sulfide Ag 2 S thin films have been prepared on pyrex and on SnO 2 /pyrex substrates by the spray pyrolysis technique (Dlala et al., Europ. Phys. J. A 2, 13 (1998)) using silver acetate and thiourea as precursors. The depositions were carried out at 200 and 250 C. The X-ray diffraction spectra show that a substrate temperature T s = 250 C with a concentration ratio x = [S]/[Ag] = 2 in the solution allows to obtain well crystallized thin films with a preferential orientation along ( 103) direction. Microprobe analysis as well as X-ray photoelectron spectroscopy (XPS) show that a nearly stoichiometric composition is obtained under these conditions. Moreover, we noticed by the same technique the presence of oxygen and carbon components particularly on the surface, due to a contamination effect. Indeed, it can be seen after etching that the intensity peaks decrease strongly, which indicated the weak proportion of these elements in the bulk of the films.
Semiconductor Science and Technology, 2008
AgGaS 2 (AGS) single crystals grown by chemical vapor transport (CVT) method were irradiated with Ag 9+ ions (120 MeV) with various ion fluences. The irradiation was carried out at room temperature (RT) and at liquid nitrogen temperature (LNT). A glancing angle x-ray diffraction (GAXRD) analysis reveals a huge lattice disorder at RT irradiation. This is observed from an increase in the full width at half maximum (FWHM) and a decrease in the intensity of the AGS (1 1 2) peak. However, there is no change in the FWHM of the (1 1 2) peak but the intensity slightly decreases at LNT irradiation. Also, AGS (3 0 3) peak is not observed for the samples irradiated with the fluences of 5 × 10 13 and 1 × 10 13 ions cm −2 at RT conditions. The GAXRD results show the decrease in degree of crystallinity upon ion irradiation at RT while there is not much degradation in crystallinity upon ion irradiation at LNT. But the LNT irradiation on AGS has its own effects. Atomic force microscope (AFM) studies show that the roughness of AGS increases on increasing the ion fluences at LNT and at RT. Also, it is found that there is an increase in the surface defects with fluences of Ag 9+ ion irradiation when compared to pristine AGS. UV-visible transmission spectra show that the percentage of transmission and bandgap energy decrease with increasing ion fluences and also that the peaks are broadened at LNT and at RT. The photoluminescence (PL) spectra were analyzed as a function of irradiation ion fluences in the AGS crystals at RT. It has been found that the emission intensities of band-to-band transition decrease with increase of ion fluences at LNT and at RT.