Studies of contact damage in polycrystalline zinc sulphide

Deformation processes within the grains and grain-boundary sliding are responsible for the formation of the porous zone and the various crack systems around plastic indentations in chemically vapour deposited (CVD) zinc sulphide. The porous zone is formed by gross grain-boundary displacements in the region directly beneath the indenter and all the cracks emanate from around the porous zone and are contained within an extensive plastic zone. For the particular grain orientation used, the material behaves in an ideal elastic/plastic manner with the development of shear flow lines within the porous zone; the interaction of the flow lines with each other or continued slip along the flow lines lead to preferential void nucleation. The porous zone forms at an average representative strain of about 2.5% and a corresponding pressure of 1.5GPa which is twice the yield stress.     

Sputtered zinc sulphide films on silicon

The design of a triode rf sputtering system for the deposit of high purity films of zinc sulphide is outlined. It is shown that a variety of dopants may be incorporated in the film over wide concentration ranges by means of this technique, and it is also shown that rare earth cathodoluminescent films may be formed. When deposited under suitable conditions a moderate degree of crystallographic orientation of the films has been achieved.     

The epitaxy of zinc sulphide on silicon

The epitaxy of zinc sulphide films on silicon has been studied by means of X-ray and electron diffraction and by scanning electron microscopy. Results have shown that due to the nature of the stacking of atoms, planar defects will predominate in such a sphalerite structure material; this is similar to the results of Pashley and Stowell on face centred cubic metals. Such defects have been shown to be more prevalent on (111) and (110) orientations, compared with the (100) orientation which gave the best epitaxial single crystal films. These results agree with other work from this laboratory on the epitaxy of zinc selenide on germanium and silicon.     

Direct synthesis of epitaxial zinc sulphide layers on zinc single-crystal substrates

Epitaxial thin zinc sulphide layers have been grown by direct synthesis on the basal face of zinc single crystals. Sulphur vapour reacted on the surface of the crystals, which were grown in sealed glass ampoules evacuated to 10^?6 torr. The thicknesses of the layers investigated varied from several hundred to 1000–1500 Å. The morphology, structure and epitaxy of the films were examined by electron microscope, electron and X-ray diffraction techniques. It was found that the film lattice had a sphalerite-type cubic structure, the perfection of the layer structure increasing with rise in both the substrate temperature and the sulphur vapour pressure. The layers were produced at substrate temperatures of 250°–400°C: polycrystalline ZnS films were obtained in the range 250°–300°C; at higher temperatures a definite texture gradually appeared and above 370°C, with a sulphur vapour pressure of 0.2–10 torr, the films became epitaxial. The following epitaxial relation was established:

$\text{{111} ZnS ∥ {0001} Zn}$

with

$\text{<110 > ZnS ∥ <11}\text{20}\text{> Zn}$

The zinc sulphide films reproduced the surface structure of the supporting zinc single crystals very well and could conveniently be used as electron microscope replicas.     

Heat treatment of electroluminescent zinc sulphide films

The temperature dependence of the conductivity and electroluminescent relative brightness in SnO₂/Cu_xS/ZnS:Mn, Cu/Al₂O₃/Al light-emitting structures was studied from room temperature to 250°C. The results obtained were interpreted in terms of an electroluminescence mechanism based on a resonant energy transfer. Consequently, electroluminescence was attributed to the contribution of local energy levels of the copper acceptor centre Cu²⁺ with two states ²E and ²T₂, the calculated separation of these levels from the valence band being 0.4 and 1.26 eV respectively.     

Properties of zinc sulphide nanoparticles stabilized in silica

Zinc sulphide nanoparticles have been synthesized in silica matrix using sol-gel method. It is observed that silica could be loaded with zinc sulphide over a very wide range of concentration without changing the nanoparticle size. A strongly luminescent zinc sulphide-silica composite, thermally stable even upto 700°C was thus obtained. Several techniques like UV absorption, photoluminescence, x-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetry and photoelectron spectroscopy have been performed to analyse the ZnS-silica composites.     

Electroluminescent zinc sulphide devices produced by sol-gel processing

Zinc sulphide thin film electroluminescent devices doped with Mn or Tb have been produced on p-type Si substrates using a process in which doped zinc oxide films are deposited by a sol-gel drain coating method from a solution of zinc acetate containing a manganese or terbium dopant. The films are then converted to ZnS by heating them in an atmosphere containing hydrogen sulphide which replaces the oxygyn with sulphur. The composition, crystalline structure and optical properties of films have shown that complete conversion from the oxide to the sulphide takes place. The luminescent characteristics of the devices so produced have been measured as a function of the doping concentrations, film thickness, insulator thickness and driving voltage and frequency. It has been found that yellow or green luminescence can be obtained using Mn or Tb doping respectively.     

Pulse plated zinc sulphide films and their characteristics

Zinc sulphide thin films were deposited by the pulse plating technique using AR grade Zinc sulphate and sodium thiosulphate precursors. The pH of the deposition bath was adjusted to 2. The duty cycle was varied in the range of 20–60%. Total deposition time was kept constant as 60 min in all the cases. X-ray diffraction studies indicated the formation of single phase cubic zinc sulphide films. After heat treatment the crystal structure transformed to hexagonal structure. Optical absorption measurements indicated a band gap values in the range of 3.6–4.0 eV as the duty cycle decreased. EDAX studies yielded a composition of the films deposited at 50% duty cycle is Zn = 48%, S = 52%. XPS studies indicated the formation of ZnS. The Zn 2p and S 3p peaks are observed. AFM studies indicated a rms value of surface roughness of 55 nm for the films deposited at a duty cycle of 60%.     

高真空卷绕式硫化锌镀膜设备的研制

介绍了ZZLD-2000/1.1高真空连续卷绕式硫化锌镀膜设备的原理、组成、性能及工作过程,并对设计和调试过程中出现的一些问题,进行了讨论分析.     

Surface and bulk properties of mechanically activated zinc sulphide

BET, scanning electron microscopy, X-ray photoelectron, infrared, X-ray diffraction and Mössbauer spectroscopy methods were used to identify changes in surface, structural and spectroscopic properties of sphalerite produced by mechanical activation. Activated samples exhibit amorphization of crystallographic structure of the mineral, as well as of hyperfine structure of the accessory manganese. The presence of a new magnetic phase was disclosed in the samples activated for longer periods of time. Changes in structure are accompanied by mechanochemical oxidation of the surface layer of sphalerite.     

Diffusion of some impurities in zinc sulphide single crystals

Using a lapping and surface-counting method, the diffusion of Mn and Au are studied and compared with the self-diffusion of S in ZnS^c. In all three cases diffusion constants exhibit a distribution over the samples used; however, by considering a large number of sample batches, average activation energies of 3.15, 2.46 and 1.16 eV have been obtained, respectively, for sulphur, manganese and gold.On leave of absence from Department of Physics and Electronics, University of Ife, Ile-Ife, Nigeria.     

Description of transient photoelectric phenomena in zinc sulphide photocells

An aging process stabilizes the photoelectric properties of r.f. sputtered zinc sulphide films, giving symmetric Poole-Frenkel dark conduction and improving Poole-Frenkel photoexcitation. The coulombic centres model may be used to explain these transient phenomena when the position of the shallowest coulombic centre is taken into account.     

Structural and electrical conductivity studies on undoped and copper-doped nanocrystalline zinc sulphide

Zinc sulphide (ZnS) and copper-doped zinc sulphide nanocrystallites (ZnS:Cu) of average size 4 and 3 nm, respectively, have been synthesized by chemical precipitation method. Structural and morphological studies using X-ray and high resolution transmission electron microscopy (HRTEM) measurements have confirmed hexagonal structure for the samples. Using impedance spectroscopy, the effect of grain interior and grain boundary regions on the electrical conductivity have been studied at various temperatures. In the high temperature region, the grain boundary contribution to conduction is found to be larger than that of the grain interior region. Further, the activation energies of charge carriers in both the grain interior and grain boundary regions have been determined. The conduction mechanism of copper-doped zinc sulphide nanocrystallites have been studied at various temperatures and the results are reported.