Deposition Of ZnS Research Articles

Nonlinear optical properties due to the thermal effect in a prism-coupled ZnS thin film

Attenuated total reflection (ATR) and an optical nonlinear response were experimentally demonstrated in a prism-coupled ZnS thin film with a cw Ar+ laser. A high-index-glass-prism–Ag–ZnS–silica-glass configuration was fabricated by sequential deposition of ZnS and Ag thin films onto a silica glass substrate and with a high-index glass prism brought into contact with the films-coated substrate. Remarkable nonlinearity and hysteresis in relation to the incident power versus the reflected power were also realized because the reflectance near the ATR condition significantly depends on the refractive index of ZnS, which depends on the reflectance. By calculation of the optical and thermal properties of the configuration adopted in the experiment, the change in the refractive index of ZnS was confirmed to be due to the temperature rise resulting from the absorption of the incident light.

Deposition of manganese-doped zinc sulfide thin films by the successive ionic layer adsorption and reaction (SILAR) method

Manganese-doped zinc sulfide, ZnS: Mn, thin films were grown by the successive ionic layer adsorption and reaction method on glass, on ITO- and Al 2O 3-covered glass, and on quartz and CaF 2 using 0.1 M ZnCl 2, 0.05 M Na 2S and 0.01 M MnCl 2 as precursor solutions. The immersion time was 20 s and the rinsing time 100 s. The manganese was doped into the film by using separate ZnS and MnS deposition cycles. The desired Mn level (0.3–0.8 wt.%) in the ZnS film was achieved using a MnS ZnS cycle ratio of 1:100. The growth rate of the ZnS: Mn film was 0.09 nm cycle −1. The films were polycrystalline and presumably cubic. The appearance of the ZnS: Mn films, studied by scanning electron microscopy, was rougher than pure ZnS films but annealing for 3 h at 500 °C in a nitrogen atmosphere flattened the films. The refractive indices varied from 2.04 to 2.22 in films grown on glass and from 2.13 to 2.32 in those grown on ITO-covered glass. According to the Rutherford backscattering spectrometry and nuclear reaction analyses the ZnS: Mn films contained approx. 20 at.% oxygen and 3–15 at.% hydrogen, but their content was significantly reduced after annealing.

In-situ investigation of ZnS deposition on mica by successive ionic layer adsorption and reaction method as studied with atomic force microscopy

The growth of ZnS thin films on a mica substrate in a Successive Ionic Layer Adsorption and Reaction (SILAR) process has been studied. The films were deposited in-situ using the commercial AFM liquid cell as flow-through reactor. Reactants and rinsing water were exchanged in the cell continuously by a computer controlled valve system. In this way the film growth could be observed directly in a time resolved sequence of images taken after 1 up to 100 cycles. The results show that the stability of the films increases between 1 and 30 cycles and that a full coverage of the surface is reached after approximately 50 cycles.

Low temperature epitaxial deposition of ZnS onto (100) Si by RF magnetron sputtering and molecular beam epitaxy

Single-crystal ZnS is deposited epitaxially onto (100)Si for the first time by RF magnetron sputtering as well as by molecular beam epitaxy. This is achieved using a novel, non-chemical, Si surface cleaning method which involved growing and then removing a thin layer of ZnS to remove the native SiO 2layer found on Si surfaces. X-ray diffraction evaluation indicates epitaxial growth occurring for films grown above 220°C.

Electrophoretic Deposition of Phosphors

A study of the electrophoretic deposition of ZnS:Ag (P-11) phosphor particles from an isopropyl alcohol (IPA) bath containing magnesium nitrate is discussed. The process was analyzed by studying the deposition of magnesium hydroxide, formed via electrolysis of water present in the IPA, as well as the phosphor particles. A model was developed which predicts the deposition rates of both the hydroxide and phosphor, which agrees well with experimental results under conditions of varying applied voltages and deposition times. When the magnesium nitrate concentration was varied, the model predicted the deposition rate of the hydroxide, but failed to predict the low deposition rates of phosphor found experimentally at magnesium nitrate concentrations of 10-5 and 10-4M. The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was unable to account for the low deposition rates. The low phosphor deposition rates were explained by changes in zeta potential due to increased pH near the electrode surface and minimum amount of hydroxide required for adhesion of the particles.

Chemical vapor deposition of ZnS : Tb electroluminescent films in a bypass-HCl flow system

Green-emitting ZnS : Tb electroluminescent films have been successfully grown by low-pressure chemical vapor deposition, in which a Tb source is transported as gaseous halide by using a HCl carrier gas. A secondary HCl flow, bypassing the source material, is additionally supplied to the growth ambience. It is shown that the ZnS : Tb film changes from the cubic structure to the hexagonal structure with increasing the bypass-HCl flow rate, whereas the Tb concentration is basically determined by the mass transfer of the Tb-halide. The film growth rate decreases significantly in the presence of the HCl flow, and simultaneously the crystal quality is much improved by the incorporation of the Tb-dopant. Such growth behaviors are explained by supposing two kinds of competetive relations; one is a surface migration process competing between ZnCl 2 and an isolated Zn atom, the other is a hexagonal nucleation process competing between TbCl 3 and ZnCl 2. The critical HCl flow rates to control the crystal structure are completely determined. The growth kinetics and the roles of Tb 3+ and Cl - ions are discussed on the basis of the competitive adsorption model.

MBE-grown ZnTe-ZnS strained-layer superlattices

RHEED pattern of ZnTe-ZnS strained-layer superlattices showed streaks and reconstruction after only five periods of deposition. The surface lattice constant obtained from RHEED streak separation showed different values during ZnTe or ZnS deposition beyond a certain thickness of the superlattice. X-ray diffraction data showed satellite peaks around the central peak, indicating good superlattice structure.

Selective Area Deposition of Passivants, Insulators, and Epitaxial Films of II-VI Compound Semiconductors

ABSTRACTII-VI semiconductor surface passivants, insulators, and epitaxial films have been deposited onto selective surface areas by employing a new masking and lift-off technique. The II-VI layers were grown by either conventional or photoassisted molecular beam epitaxy (MBE). CdTe has been selectively deposited onto HgCdTe epitaxial layers as a surface passivant. Selective-area deposition of ZnS has been used in metal-insulator-semiconductor (MIS) structures. Low resistance ohmic contacts to p-type CdTe:As have also been realized through the use of selectively-placed thin films of the semi-metal HgTe followed by a thermal evaporation of In. Epitaxial layers of HgTe, HgCdTe, and HgTe-CdTe superlattices have also been grown in selective areas on CdZnTe substrates, exhibiting specular morphologies and double-crystal x-ray diffraction rocking curves (DCXD) with full widths at half maximum (FWHMs) as narrow as 140 arcseconds.

A novel atmospheric pressure technique for the deposition of ZnS by atomic layer epitaxy using dimethylzinc

We report on the results of a novel atomic layer epitaxy (ALE) deposition system which performs deposition at atmospheric pressure. Polycrystalline thin films of ZnS have been deposited using the gaseous sources dimethylzinc and hydrogen sulphide. Depositions were carried out at substrate temperatures in the range 25 to 500 ° C. The results of several bulk and surface analytical techniques are presented which suggest that the films are stoichiometric and of high purity and crystal quality. The methodology of system operation is discussed as is the dependence of film quality upon process parameters.

ZnS:Mn in polycrystalline electroluminescence thin film display

The AC driven electroluminescence (EL) display consisting of an ZnS:Mn film sandwiched between dielectric films has entered industrial production and there is a sound understanding of its physics. Recent progress reported here concerns (a) the proof of loss-free acceleration of electrons and avalanche breakdown of the ZnS film, maintained reversible by a voltage transfer to the sandwiching insulator films proportional to the transferred charge, and (b) the dependence of efficiency upon ZnS film thickness and/or deposition technology (e-beam, CVD, ALE). The relation of the positive features to basic properties of II–VI compounds (wide-gap) is emphasized. However, limits are imposed for other colors: low solubility of RE3+ in ZnS; high (intrinsic?) defect densities in SrS:RE, CaS:RE giving rise to inherently low efficiency processes.

A solution growth technique for the preparation of zinc sulfide thin film

A method has been developed for the chemical deposition of ZnS thin films on glass substrate at room temperature (30°C) using Zn 2+-salt solution, triethanolamine (TEA), sodium hydroxide, hydrazine hydrate and thiourea as reacting agents. X-ray characterization, optical absorption and photocurrent measurement have been performed to confirm the deposition of ZnS. The films are found to be n-type in nature with a band gap of 3.68 eV.

The organometallic chemical vapour deposition of ZnS and ZnSe at atmospheric pressure

It is shown that thin film single crystal layers of ZnS, ZnSe and ZnS x Se 1- x can be grown on to a variety of substrates by direct reaction at atmospheric pressure, of dimethyl zinc, hydrogen sulphide and/or hydrogen selenide, using hydrogen as the carrier gas. Growth has been observed between 350 and 750°C at growth rates within the range 0.5 to 10 μm h -1. The layers exhibit a uniformly high standard of surface morphology and perfection.

Growth and structure of electron-beam evaporated ZnS films

Recent developments in the preparation of compound films have attained some degrees of success. In this attempt, experiments of ZnS deposition were performed in a vacuum system by the electron beam evaporation. The deposited films were analyzed as being stoichiometric by using an energy dispersive X-ray system. Columnar structures have also been observed in these ZnS films. The film growth depends upon the accommodation coefficient, substrate temperature, and deposition rate of the vapor species arriving at the surface. It is suggested that the equilibrated temperature may be considered as a normalizing parameter in characterizing these films.

The Reaction between Hydrogen Sulfide and Spherical Pellets of Zinc Oxide

The reaction between hydrogen sulfide and spherical pellets of zinc oxide was studied in a microbalance reactor at 375/sup 0/-800/sup 0/C. The gaseous mixture contained 1-6% H/sub 2/S diluted with hydrogen (added to stabilize H/sub 2/S) and nitrogen, with a 5:1 H/sub 2//H/sub 2/S molar ratio. Rapid and almost complete reaction occurred at 600/sup 0/-700/sup 0/C. Near 800/sup 0/C, slow decomposition of ZnO led to a vapor-phase reaction and deposition of nonporous ZnS on the pellet surface, which prevented further reaction. At below 600/sup 0/C, the reaction stopped well before total ZnO conversion was obtained. Experimental time-conversion results for the 600/sup 0/-700/sup 0/C range, where pore diffusion was the controlling resistance, were in good accord with values predicted by the Szekely et al. grain model. The strong deviation from the model predictions at lower temperatures were attributed to the dominant role of grain diffusion resistance. The H/sub 2/S-ZnO reaction is currently used in the desulfurization of hydrocarbon gases for synthesis of ammonia and has been suggested for sulfur removal in SNG processing.

Leaky waves in a heteroepitaxial film

Theoretical as well as experimental investigations were carried out for the propagation of leaky waves along an important class of optical thin-film waveguides. For this type of guiding structure which may consist of heteroepitaxial deposition of ZnS or ZnSe on GaAs, the dielectric constant of the thin film is less than that of the substrate. Consequently, only the leaky type of guided waves may exist. Theoretical results show that the attenuation constants of leaky modes, which may be TE or TM, are inversely proportional to (thickness of layer)3 and directly proportional to (wavelength)2, and that TM modes are more lossy than TE modes. The existence of these leaky modes has also been demonstrated for three different thicknesses.