The Optical Property of CPD Prepared CdS Films

CdS films were prepared with chemical pyrolysis deposition (CPD) at 450℃ during film growth, and these CdS films were also annealed at different temperature from 200-500℃.The optical property of the CdS films before and after annealing was investigated at different measuring temperature from 10K to 300K. Optical absorption spectra show that the absorption edge is towards the shorter wavelengths, and the energy band gaps deduced from the plots of (α·hν) 2 vs. hν are increased when the measuring temperature is decreased. The optical behaviors of the CdS films annealed at a certain temperature seem to have the similar tendency at different measuring temperature. Based on dE- ex/dT curve dependent on annealing temperature, some phenomena related microstructure in CdS films could be found.

EFFECT OF ANNEALING TREATMENT ON THE STRUCTURE OF CdS FILMS

The effect of annealing treatment on the structure of CdS films was investigated. The cadmium sulfide thin films were prepared by chemical bath deposition, and were annealed at nitrogen atmosphere at different temperatures. The films were characterized by SEM and XPS (X-ray photoelectron spectroscopy). X-ray photoelectron spectroscopy was used to examine the chemical states on the CdS films surface. It was found that thermal annealing could produce large grains of CdS thin films, remove the air contamination and reduce the oxygen content on the CdS films surface. Therefore, the CdS films changed more uniform and smoother surface after thermal annealing.

CdS Thin Films Deposited by CBD Method on Glass

CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be dominant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron micro- scope results revealed that the morphology of the CdS film changed from pinholes to rough, inhomogeneous surface with increasing deposition time and deposition temperature. The X- ray diffraction results showed the film structure was a mixture of two phases： hexagonal and cubic, and it was very important to controll deposition time to the film＇s crystal phase. All films in depth of approxilnate 100 nm existed above 65% transmittance, the absorption edge became ＂red-shift＂ with temperature rising. At 60 and 70℃, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90℃ the energy band gap was less than 2.42 eV and increased little when the time changed from 10min to 15 nfin at 80℃.

Preparation and properties of CdS thin films grown by ILGAR method

CdS thin films were deposited by the ion layer gas reaction (TLGAR) method.Structural, chemical, topographical development as well as optical and electrical properties ofas-deposited and annealed thin films were investigated by XRD, SEM, XPS, AFM and UV-VIS. The resultsshowed that the thin films are uniform, compact and good in adhesion to the substrates, and thegrowth of the films is 2.8 nm/cycle. The evolution of structure undergoes from the cubic structureto the hexagonal one with a preferred orientation along the (002) plane after annealing at 673 K. Anamount of C, O and Cl impurities can be reduced by increasing the drying temperature or byannealing in N2 atmosphere. It was found that the band gap of the CdS films shifts to higherwavelength after annealing or increasing film thickness. The electrical resistivity decreases withincreasing annealing temperature and film thickness.

Low temperature ferromagnetic properties of CdS and CdTe thin films

The magnetic property in a material is induced by the unpaired electrons. This can occur due to defect states which can enhance the magnetic moment and the spin polarization. In this report, CdS and CdTe thin films are grown on FTO glass substrates by chemical bath deposition and close-spaced sublimation, respectively. The magnetic properties, which are introduced from oxygen states, are found in CdS and CdTe thin films. From the hysteresis loop of magnetic moment it is revealed that CdS and CdTe thin films have different kinds of magnetic moments at different temperatures. The M–H curves indicate that from 100 K to 350 K, CdS and CdTe thin films show paramagnetism and diamagnetism, respectively.A superparamagnetic or a weakly ferromagnetic response is found at 5 K. It is also observed from ZFC/FC curves that magnetic moments decrease with temperature increasing. Spin polarized density functional calculation for spin magnetic moment is also carried out.

Effect of Annealing on Structural,Optical and Electrical Properties of CdS Thin Films Grown by ILGAR

CdS thin films were deposited by ILGAR （ ion lay gas reaction） method. The effect of annealing temperature under N2 atmosphere on the structural, chemical, topographical development and optical and electrical properties of CdS thin films was investigated by XRD, SEM, XPS, UV- VIS and two-probe technique. It is found that the cubic-phase of as-deposited CdS film transforms to hexagonal phase with a perfected orientation along （002） plane at 300 ℃ . The band gap decreases with increasing annealing temperature until 300 ℃ , which is consistent with the grain growth. The fall of dark and light resistivitiy is obvious with increasing annealing temperature, corresponding to the continuous grain growth and deviation of stoichiometry at higher temperature. The smooth and uniform surface of as-deposited films becomes rougher through thermal treatment, which is related to grain growth and sublimation of CdS at a higher annealing temperature.

Evaporated Thin Films of CdS and CdTe: Optimization for Photovoltaic Applications

Thin films of cadmium sulphide and cadmium telluride have been prepared by thermal evaporation under various conditions of deposition. These films have been characterized optically. electrically and for structure determination. The results of these characterizations along with the initial results of all thin film CdS/CdTe solar cells are presented in this paper

Deposition Methods and Properties of Polycrystalline CdS Thin Films

CdS thin film was used as a suitable window layer for CdS/Cd Te solar cell, and the properties of CdS thin films deposited by pulsed laser deposition（PLD）, chemical bath deposition（CBD） and magnetron sputtering（MS） were reported. The experimental results show that the transmittances of PLD-Cd S thin films are about 85% and the band gaps are about 2.38-2.42 e V. SEM results show that the surface of PLD-Cd S thin film is much more compact and uniform. PLD is more suitable to prepare the Cd S thin films than CBD and MS. Based on the thorough study, by using totally PLD technique, the FTO/PLD-Cd S（150 nm）/CSS-Cd Te solar cell（0.0707 cm^2） can be prepared with an efficiency of 10.475%.

In-situ growth of a CdS window layer by vacuum thermal evaporation for CIGS thin film solar cell applications

Highly crystalline and transparent CdS films are grown by utilizing the vacuum thermal evaporation （VTE） method. The structural, surface morphological, and optical properties of the films are studied and compared with those prepared by chemical bath deposition （CBD）. It is found that the films deposited at a high substrate temperature （200 ℃） have a preferential orientation along （002） which is consistent with CBD-grown films. Absorption spectra reveal that the films are highly transparent and the optical band gap values are found to be in a range of 2.44 eV-2.56 eV. Culnl_xGaxSe2 （CIGS） solar cells with in-situ VTE-grown CdS films exhibit higher values of Voc together with smaller values of Jsc than those from CBD. Eventually the conversion efficiency and fill factor become slightly better than those from the CBD method. Our work suggests that the in-situ thermal evaporation method can be a competitive alternative to the CBD method, particularly in the physical- and vacuum-based CIGS technology.

Mn doping effects on the gate-tunable transport properties of Cd3As2 films epitaxied on GaAs

The Mn doping effects on the gate-tunable transport properties of topological Dirac semimetal Cd3As2 films have been investigated.Mn-doped Cd3As2 films are directly grown on GaAs(111)B substrates by molecular-beam epitaxy,during which the single crystal phase can be obtained with Mn concentration less than 2%.Shubnikov-de Haas oscillation and quantum Hall effect are observed at low temperatures,and electrons are found to be the dominant carrier in the whole temperature range.Higher Mn content results in smaller lattice constant,lower electron mobility and larger effective band gap,while the carrier density seems to be unaffected by Mn-doping.Gating experiments show that Shubnikov-de Haas oscillation and quantum Hall effect are slightly modulated by electric field,which can be explained by the variation of electron density.Our results provide useful information for understanding the magnetic element doping effects on the transport properties of Cd3As2 films.

Structural, Optical and Electrical Studies on Spray Deposited Manganese Doped Cadmium Sulphide Thin Films

CdS （cadmium sulphide） thin films have been prepared on glass substrate at 400 ℃ using home built spray pyrolysis apparatus. Aqueous solutions of cadmium chloride and thiourea were used for the cadmium sulphide films and different proportions by weight/volume of MnCl2·4H2O was used for doping Cd1-xMnxS （Mn onto cadmium sulphide） films. The films obtained are having continuous, smooth surface with good transmittance. The thickness of CdS film is of the order of 300 nm. Determination of the crystalline nature ＆ calculation of average grain size have been done using XRD pattern. The effect of Mn on the surface morphology of CdS film has been studied by scanning electron microscopy. The optical band gap has been calculated using the data from transmission spectra. Resistance before and after doping with Mn is also presented in the paper.

Effect of Pre-heating Temperature on Structural and Optical Properties of Sol-gel Derived Zn_(0.8)Cd_(0.2)O Thin Films

Zn_（0.8）Cd_（0.2）O thin films prepared using the spin-coating method were investigated. X-ray diffraction, scanning electron microscopy, and UV-Vis spectrophotometry were employed to illustrate the effects of the pre-heating temperature on the crystalline structure, surface morphology and transmission spectra of Zn_（0.8）Cd_（0.2）O thin films. When the thin films were pre-heated at 150 ℃, polycrystalline Zn O thin films were obtained. When the thin films were pre-heated at temperatures of 200 ℃ or higher, preferential growth of Zn O nanocrystals along the c-axis was observed. Transmission spectra showed that thin films with high transmission in the visible light range were prepared and effective bandgap energies of these thin films decreased from 3.19 e V to 3.08 e V when the pre-heating temperature increased from 150 ℃ to 300 ℃.

Substrate Evolution to Microstructural and Optoelectrical Properties of Evaporated CdS Thin Films Correlated with Elemental Composition

A typical high-e fficiency solar cell device needs the best lattice matching between different constituent layers to mitigate the open-circuit voltage loss. In the present work, the physical properties of CdS thin films are investigated where films with 100 nm thickness were fabricated on the different types of substrates viz. soda–lime glass, indium-doped tin oxide(ITO)-and fl uorine-doped tin oxide(FTO)-coated glass substrates, and silicon wafer using electron beam evaporation. The X-ray diffraction patterns confirmed that deposited thin films showed cubic phase and had(111) as predominant orientation where the structural parameters were observed to be varied with nature of substrates. The ohmic behaviour of the CdS films was disclosed by current–voltage characteristics, whereas the scanning electron microscopy micrograph revealed the uniform deposition of the CdS films with the presence of round-shaped grains. The elemental analysis confirmed the CdS films deposition where the Cd/S weight percentage ratio was changed with nature of substrates. The direct energy band gap was observed in the 1.63–2.50 eV range for the films grown on different substrates. The investigated properties of thin CdS layers demonstrated that the selection of substrate(in terms of nature) during device fabrication plays a crucial role.

Construction of immobilized films photocatalysts with CdS clusters decorated by metal Cd and BiOCl for photocatalytic degradation of tetracycline antibiotics

A kind of CdS/Cd-BiOCl immobilized films photocatalyst was prepared.The optical and physicochemical properties of the CdS/Cd-BiOCl photocatalysts were analysed,and the detailed characterization revealed CdS/Cd-BiOCl films photocatalyst with good charge carrier separation effect.The reusabilities and photocatalytic properties of the samples were studied.The 15%Cd S/Cd-Bi OCl photocatalyst exhibited superior performance in photocatalytic degradation of tetracycline(TC)and favorable stability under visible light irradiation.As for the photodegradation rate of TC,15%CdS/Cd-BiOCl exhibited an excellent photodegradation activity,which is 4.06 and 9.53 times higher than that of Cd S/Cd and Bi OCl,respectively.The results showed that dominant active species are·O_(2)^(-)and·OH radicals during photodegradation.The charge transfer in Z-scheme CdS/Cd-BiOCl films photocatalyst could synchronously generate conduct band(CB)electrons in BiOCl and valence band(VB)holes in CdS,and metal Cd served as electron mediator.This work can be a reference for the design of film photocatalysts and new insight for photodegradating towards contaminants.

Influence of deposition temperature on CdS thin films by polyol method

CdS thin films were successfully deposited onto glass substrates for the first time by the polyol method using cadmium acetate, thiourea and diethylene glycol as the raw materials. The effects of the deposition tempera- ture from 120 to 200 ℃ in steps of 20 ℃on the structure, morphology and optical properties of the resultant films were investigated. It was found that the crystallinity was improved and the value of the surface average roughness was decreased with increasing the deposition temperature. The average grain sizes of the CdS thin films were 77.16 and 76.61 nm at 140 and 180 ℃, respectively. All samples showed excellent transmittance and the band gaps were found to reduce from 2.55 to 2.45 eV with the increase of the deposition temperature, which was attributed to the improvement of crystallinity.

Structural and optical properties of polycrystalline CdS thin films deposited by electron beam evaporation

Highly crystalline and transparent cadmium sulphide （CdS） films were deposited on glass substrate by electron beam evaporation technique. The structural and optical properties of the films were investigated. The X-ray diffraction analysis revealed that the CdS films have a hexagonal structure and exhibit preferred orientation along the （002） plane. Meanwhile, the crystalline quality of samples increased first and then decreased as the substrate temperature improved, which is attributed to the variation in film thickness. UV-vis spectra of CdS films indicate that the absorption edge becomes steeper and the band gap present fluctuation changes in the range of 2.389-2.448 eV as the substrate temperature increased. The photoluminescence peak of the CdS films was found to be broadened seriously and there only emerges a red emission band at 1.60 eV. The above results were analyzed and discussed.

Temperature dependence of surface and structure properties of ZnCdO film

Zn1-xCdx O films are grown on c-sapphire substrates by laser molecular beam epitaxy（LMBE） at different temperatures. Their crystallographic structures, compositions, surface electronic structures are investigated. The a-axis lattice constant of Zn0.95Cd0.05 O is 3.20. Moreover, the epitaxial relationship shows a 30°-in-plane rotation of the film with respect to the c-sapphire substrate. When the substrate temperatures arrives at 500℃, the in situ reflection high-energy electron diffraction（RHEED） pattern of Zn Cd O film shows sharp streaky pattern. The maximum Cd content of Zn Cd O film grown at low substrate temperatures increases up to about 29.6 at.%, which is close to that of the ceramic target. In situ ultraviolet photoelectron spectroscopy（UPS） measurements demonstrate that Zn Cd O film exhibits intense peaks at 4.7 e V and 10.7 e V below the Fermi level, which are assigned to the O 2p and Zn 3p states. Energetic distance between Zn 3d and Cd 4d is 0.60 e V. Above 470 nm, the thin film shows excellent optical transmission.

Substrate temperature dependent studies on properties of chemical spray pyrolysis deposited CdS thin films for solar cell applications

Thin films of CdS have been prepared by chemical spray pyrolysis by spraying precursor solution directly onto soda lime glass（SLG） substrates. Influence of substrate temperature on structural, optical, morphological and electrical properties have been investigated by using various techniques such as low angle X-ray diffraction（XRD）, Raman spectroscopy, X-ray photoelectron spectroscopy（XPS）, field emission scanning electron microscopy（FESEM）, atomic force microscopy（AFM）, transmission electron microscopy（TEM）, UV–visible spectroscopy photoluminescence（PL） spectroscopy etc. Formation of CdS has been confirmed by low angle XRD,Raman spectroscopy and XPS analysis. XRD pattern showed that CdS films are polycrystalline, have hexagonal structure and prefer orientation of crystallites shifts from（101） to（002） with increase in substrate temperature.Raman spectroscopy revealed that exciton-phonon coupling depends on substrate temperature and hence on crystallite size. Optical band gap increased from 2.43 to 2.99 eV when substrate temperature increased from 325 to 475 ℃. Transmittance of the film also showed an increasing trend from 52% to 80% with increase in substrate temperature. Such high band gap and transmittance values of CdS films prepared at 475℃ make it a useful window material in CdS/CdTe and CdS/Cu_2S heterojunction solar cells.