• 한국군사과학기술학회지
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• 제13권4호
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• pp.659-664
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• 2010

The ZnS/CdS thin films were made using 99.99% ZnS and CdS(Aldrich) powders in $7{\times}10^{-6}torr$. The ZnS layer was coated over the CdS layer on an AlOx membrane within a vacuum, at the average speed of $1{\AA}/sec$. After studying the ZnS/CdS and CdS thin films(both with the dimensions of 2.52nm), using fluorescence spectroscopy and comparing the respective results together, we found that although both of the resulting spectra peaked at 390nm, the ZnS/CdS thin films showed a narrower peak, and a higher intensity of photoluminescence than the CdS thin films. The particles of ZnS/CdS thin films also proved to be more homogeneous in size. In addition, the ZnS layer acted as a protective layer. Also, after studying the spectra of ZnS/CdS thin films taken 30 days after their preparation, we found no signs of aging. These results were verified through the scanning electron microscopy(SEM), EDX analysis, thin film X-ray diffraction, and luminescence spectroscopy.

• 한국군사과학기술학회지
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• 제15권4호
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• pp.502-506
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• 2012

In order to find the structural characteristics of the thin films of group II-VI semiconductor compounds compared with those of powder materials, films were made of 4 powders of ZnS, CdS, CdSe, and CdTe(Aldrich), each with 99.99 % purity. For the ZnS/CdS multi-layers, the ZnS layer was coated over the CdS layer on an $AlO_x$ membrane, which served as a protective layer within a vacuum at the average speed of 1 ${\AA}$/sec. After studying the structures of the group II-VI semiconductor thin films by using X-ray spectroscopy, we found that the ZnS, ZnS/CdS, CdS, and CdSe films were hexagonal and exhibited some degree of preferred orientation. Also, the particles of the thin films of II-VI semiconductor compounds proved to be more homogeneous in size compared to those of the powder materials. These results were further verified through scanning electron microscopy(SEM), EDX analysis, and powder and thin film X-ray diffraction.

• Transactions on Electrical and Electronic Materials
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• 제12권4호
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• pp.164-168
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• 2011

Nanocrystalline cadmium sulphide (CdS) thin films were prepared using chemical bath deposition (CBD), and the structural, optical and photoconductive properties were investigated. The crystal structure of CdS thin film was studied by X-ray diffraction. The crystallite size, dislocation density and lattice constant of CBD CdS thin films were investigated. The dislocation density of CdS thin films initially decreases with increasing film thickness, and it is nearly constant over the thickness of 2,500 ${\AA}$. The dislocation density decreases with increasing the crystallite size. The Urbach energies of CdS thin films are obtained by fitting the optical absorption coefficient. The optical band gap of CdS thin films increases and finally saturates with increasing the lattice constant. The Urbach energy and optical band gap of the 2,900 A-thick CdS thin film prepared for 60 minutes are 0.24 eV and 2.83 eV, respectively. The activation energies of the 2,900 ${\AA}$-thick CdS thin film at low and high temperature regions were 14 meV and 31 meV, respectively. It is considered that these activation energies correspond to donor levels associated with shallow traps or surface states of CdS thin film. Also, the value of ${\gamma}$ was obtained from the light transfer characteristic of CdS thin film. The value of ${\gamma}$ for the 2,900 A-thick CdS thin film was 1 at 10 V, and it saturates with increasing the applied voltage.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.239-242
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• 2004

A stoichiometric mixture of evaporating materials for $CdIn_2S_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdIn_2S_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by hot wall epitaxy(HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $420^{\circ}C$ respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of $CdIn_2S_4$ single crystal thin films measured from Hall effect by van der Pauw method are $9.01{\times}10^{16}\;cm^{-3}$ and $219\;cm^2/V{\cdot}s$ at 293 K, respectively. From the optical absorption measurement, the temperature dependence of energy band gap on $CdIn_2S_4$ single crystal thin films was found to be $E_g(T)\;=\;2.7116\;eV\;-\;(7.74{\times}10^{-4}\;eV)T^2/(T+434)$. After the as-grown $CdIn_2S_4$ single crystal thin films was annealed in Cd-, S-, and In-atmospheres, the origin of point defects of $CdIn_2S_4$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K.

• 한국표면공학회지
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• 제29권6호
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• pp.862-868
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• 1996

Cadmium sulfide is commonly used as the window material for thin film solar cells, and can be prepared by several techniques such as sputtering, spray pyrolysis, close spaced sublimation (CSS), thermal evaporation, solution growth methods, etc. In this study, CdS films were deposited by thermal evaporation, close spaced sublimation, and solution growth methods, respectively, and the effects of the methods on physical properties of polycrystalline CdS deposited on ITO/glass were investigated. Also, the effects of variously prepared CdS thin films on the physical properties of CdTe deposited on the CdS were investigated. The thickness of polycrystalline CdS films was maintained at $0.3\mu\textrm{m}$ except for the solution grown CdS when $0.2\mu\textrm{m}$ thick CdS was deposited. After the deposition, all the samples were annealed at $400^{\circ}C$ or $500^{\circ}C$ in H2 atmosphere. To investigate physical properties of the deposited and annealed CdS thin films, UV-VIS spectro-photometry, X-ray diffractometry (XRD), and Auger electron spectroscopy (AES), and cross sectional transmission electron microscopy(XTEM) were used to analyze grain size, crystal structure, preferred orientation, optical properties, etc. The annealed CdS showed the bandedge transition at 510nm and the optical transmittance high than 80% for all of the variously deposited films. XRD results showed that CdS thin films variously deposited and annealed had the same hexagonal structures, however, showed different preferred orientations. CSS grown CdS had [103] preferred orientation, thermally evaporated CdS had [002], and CdS grown by the solution growth had no preferred orientation. The largest grain size was obtained for the CSS grown CdS while the least grain size was obtained for the solution grown CdS. Some of the physical properties of CdTe deposited on the CdS thin film such as grain size at the junction and grain orientation were affected by the physical properties of CdS thin films.

• 한국표면공학회지
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• 제41권1호
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• pp.28-32
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• 2008

In this paper CdS thin films, which were widely used window layer of the CdS/CdTe and the CdS/$CuInSe_2$ heterojunction solar cell, were grown by chemical bath deposition, which is a very attractive method for low-cost and large-area solar cells, and the structural, optical and electrical properties of the films was studied. As the thiourea/$CdAc_2$ mole ratio was increased, the deposition rate of CdS films prepared by CBD was increased due to increasing reaction velocity in solution and the optical bandgap was increased at higher thiourea/$CdAc_2$ mole ratio due to larger grain size and continuous microstructure. The minimum resistivity of the films was at thiourea/$CdAc_2$ mole ratio of 3.

• 한국전기전자재료학회논문지
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• 제18권3호
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• pp.199-205
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• 2005

Polycrystalline cadmium sulfide(CdS) thin films were deposited on glass substrate by chemical bath deposition(CBD) and vacuum evaporation (VE) techniques. VE-CdS films consisted primarily of hexagonal phase, whereas CBD CdS films containing primarily the cubic form. VE-grown films were shown to have better crystallinity than CBD-grown films. The grain size of the CBD films is smaller than the ones of VE films. VE-CdS films exhibited relatively high transmittance in the above-gap region and band gap compared with CBD films. However, CdTe solar cells with these low quality CBD-CdS layers yield higher and more stable characteristics. Current-voltage-temperature measurements showed that the current transport for both cells was controlled by both tunneling and interface recombination but the cells with CBD-CdS displayed less tunneling.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.129-130
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• 2006

A stoichiometric mixture of evaporating materials for $CdIn_2S_4$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CdIn_2S_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by hot wall epitaxy(HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $420^{\circ}C$, respectively. After the as-grown $CdIn_2S_4$ single crystal thin films was annealed in Cd-, S-, and In-atmospheres, the origin of point defects of $CdIn_2S_4$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of $V_{cd}$, $V_s$, $Cd_{int}$, and $S_{int}$, obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment m the S-atmosphere converted $CdIn_2S_4$ single crystal thin films to an optical p-type. Also. we confirmed that In in $CdIn_2S_4$/GaAs did not form the native defects because In in $CdIn_2S_4$ single crystal thin films existed in the form of stable bonds.

• 한국결정학회지
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• 제19권1호
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• pp.25-30
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• 2008

In order to characterize the optical properties of CdS thin films and CdS powders, the following experiments were performed: CdS wurtzite thin films were made using 99.99% CdS (Aldrich) powder and the $AlO_x$ membranes in $7{\times}10^{-6}$ torr(here, the average vacuum coating speed is $1{\AA}/sec$.). The surface states of CdS nano-particles with dimensions of 3.87 nm were studied through the fluorescence spectroscopy. From the resulting spectra exhibited, we can see a sharp fluorescence at 451 nm arising from the excitons on the CdS thin films, compared with the 448nm peak of the CdS powders.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1645-1647
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• 1996

Polycrystalline CdTe thin films -have been studied for photovoltaic application because of their high absorption coefficient and optimal band gap energy (1.54 eV) for solar energy conversion. In this study, we prepared CdTe films using RF-magnetron sputtering method and investigated structural, optical and electrical properties with spectrophotometer, XRD, EDX, and resistivity meter. CdTe films at $200\;^{\circ}C$ showed a mixture of zinc blend (Cubic) and wurtzite (hexagonal) phase. On the other hand, the films at $400\;^{\circ}C$ showed highly oriented structure having hexagonal structure. The resistivity of CdTe films deposited on $SiO_2$ substrates was about $10_7\;{\Omega}cm$. The value of resistivity decreased with the increase of the substrate temperature. CdTe were sputtered on CdS thin films prepared by chemical bath deposition for the formation of the heterojunction. I-V characteristics of these cells were measured at a light density of $100mw/cm^2$, AM. 1.0. The present thin film solar cells showed a conversion efficiency of about 5%.