Volume 16, Issue 3
June 1993, pages 159-241
pp 159-170 June 1993
Thin films of (Pb1 −xSnx)1 −yTey have been deposited by vacuum evaporation onto glass, mica, CaF2 and NaCl substrates heated to various temperatures at low deposition rates. Transmission HEED, TEM and SEM studies have been carried out for as-grown films. HEED photographs show that (i) the degree of crystallinity of the films improves at higher substrate temperatures and (ii) the crystallites have smaller dimensions on CaF2 than on NaCl, mica and even glass, under identical conditions of deposition. SEM studies reveal that with increasingTsub, grains tend to form clusters through mobility coalescence. Needleshaped grains are formed when the deposition rate exceeds a certain critical value. Formation of needle-like grains has been attributed to the excess Te atoms possessing trigonal structure so that such grains can be observed only inp-type PbSnTe films.
pp 171-175 June 1993
In this communication, we report the single crystal growth of selenium by the solution method. We have observed a new mesh-like growth pattern in hexagonal selenium for the first time. Crystals having hexagonal morphology are packed together like hay stick bunches.
pp 177-186 June 1993
CuInS2 is a promising chalcopyrite semiconducting material for solar cell fabrication. Using aqueous solutions of cupric chloride, indium trichloride and thiourea, we deposited thin CuInS2 films on glass at 350°C and studied their structural, optical and electrical properties. From the XRD pattern the chalcopyrite structure of these films was confirmed. The films were polycrystalline. The grain size estimated from scanning electron micrographs was found to be of the order of 1µm. Resistivity of the film was measured for temperatures ranging from 77 to 473 K. Band gap values were determined from optical transmission data. Hall mobility and carrier concentration at room temperature were calculated using Van der Pauw-Hall method.
pp 187-191 June 1993
Infrared spectra of vacuum-deposited molybdenum trioxide thin films have been studied. The variation of electrical conductivity with temperature for different thicknesses of films has been investigated. Electrical conductivity of the films as a function of time of UV irradiation was found to increase initially, then decreased rapidly and reached a steady value. It increased and reached a steady value with time when irradiation was cut-off.
pp 193-204 June 1993
The surface topography development on a Cu sheet and a Si(111) wafer was studied after being sputtered in a Penning ionization gauge (PIG) ion source using Ar gas. In the case of Cu, a high density of conical structure was developed on the surface. The most striking feature was that the individual cones, relatively large in size, were often coated with impurity layers. Some cones were decorated with concentric ring-like patterns on their surfaces. The overlying coating was thought to be responsible for the initial growth of the cones and subsequent evolution of secondary protuberances on the surfaces of the cones. In the case of Si, though a few impurity-induced conical protrusions were formed, the dominant morphology was in the form of etch pits. In addition to usual single cones, Si surface developed cones of dimeric structure and cluster of cones.
pp 205-211 June 1993
Adsorption of basic dye methylene blue by some Indian clays has been studied. BET plotting of the adsorption isotherms was applied to determine the specific surfaces of clays and heat of adsorption. About 10–20% lower values of specific surfaces were obtained when compared with the most accurate gas-adsorption BET results and its probable reasons discussed. The calculated heat of adsorption values confirm the physical adsorption.
pp 213-227 June 1993
Experimental investigations have been carried out on electro-discharge machining of titanium in respect of surface finish, out-of-roundness and overcut using rotating copper-tungsten tool electrode. An attempt has also been made to compare the results with stationary electrode.
It is concluded that rotation of electrode improves out-of-roundness, surface roughness, overcut and out-of-roundness increase with increase of current with both rotating and stationary electrodes.
pp 229-237 June 1993
Chlorite occurring in tremolite-chlorite schist rock of Byrapur chromite deposit of southern India has been investigated by57Fe Mössbauer spectroscopy along with XRD, IR and EPMA analyses. From XRD and EPMA results the chlorite is identified as clinochlore. The fit of Mössbauer spectrum (at room temperature) shows five symmetric doublets for iron. Based on hyperfine parameters three doublets are assigned to Fe2+ attrans andcis positions of talc layers, and Fe2+ at brucite layer. The remaining two doublets are attributed to Fe3+ attrans position and Fe3+ at tetrahedral site. The Mössbauer result suggests that the Fe3+ in octahedral sites of this chlorite was caused by oxidation after chloritization. The chlorite of Byrapur area was less oxidized compared to the chlorite of Sukinda chromite deposit of eastern India.
pp 239-241 June 1993
We report the first operation of light emittingp-n junction diode in porous silicon fabricated by diffusion.
Volume 42 | Issue 6
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