Sulfur Annealing Research Articles

Interaction of S with W(001)

Sulfur chemisorbed on W(001) has been studied by soft X-ray and ultraviolet photoelectron spectroscopy (UPS), Auger electron spectroscopy and work function measurements. Two distinct S 2p photoemission states have been identified as a function of sulfur coverage and sample annealing temperature. Below 0.5 ML, virtually all of the sulfur exists in a single state. Above 0.5 ML, a second state emerges at a lower binding energy. At 1 ML of sulfur, the two states have comparable intensity if the sample is annealed to 600 K. However, if the sample is annealed to 900 K nearly all of the sulfur resides in the low binding energy state. The high and low binding energy states have been associated with sulfur adsorbed in hollow and bridge sites, respectively. Possible reasons for the change in binding energy for sulfur adsorbed in the two different sites include an initial state (charge transfer) effect and a change in reference potential due to a change in height above the surface in the two types of adsorption site. The UPS, work function change and S(LMM) Auger lineshape results all indicate a change in S-W bonding at sulfur coverages above 0.5 ML.

Electroluminescence of Schottky diodes rare-earth-doped zinc sulphide

Trivalent impurities substituting for divalent host atoms in insulators are normally charge-compensated by other impurities or defects. In semiconductors they behave as donors with charge compensation by electrons. The rare earths in ZnS have an intermediate behaviour. Absorption and luminescence show the trivalent configuration even in n-type material, except for Eu2+ with its half-filled shell. This is in contrast to 3dn impurities, where the d-shell occupancy can, other than for Mn, be changed. The authors show that the luminescence fine structure of ZnS:Sm is different after zinc and sulphur annealing, indicating local charge compensation. However, it is easy to make conducting n-type ZnS with rare-earth doping and zinc treatment, which suggests that at least some rare-earth atoms act as donors. Such material shows, in addition to 4fn lines, broad green and red bands in photoluminescence. In electroluminescence at a Schottky barrier for conducting ZnS:Re a broad band with fast decay is observed. This is attributed to transitions between different parts of the conduction band. In addition there is a green band similar to that seen in photoluminescence, but any 4fn lines are below the noise background. The results show that the presence of luminescent rare-earth centres and hot electrons is not sufficient for rare-earth emission in electroluminescence.

Synthesis and photoelectrochemistry of In 2S 3

In 2S 3 was prepared by chemical vapor phase transport and gradient freeze techniques. A variety of differently doped samples were also synthesized. Both n, and n plus p photoresponses were observed depending on the dopant, quantity of excess sulfur, or sulfur atmosphere annealing. Photoetching significantly increased the photocurrent density at short circuit. In a polysulfide couple, the maximum power efficiency obtained with white light was 0.3% and the quantum efficiency of carrier collection at short circuit was 43%. Photocurrent onset occured near - 1.1 V which was shifted significantly positive in nonsulfide-sulfur containing couples. Band gap determinations were made. Stability studies as measured by In 3+ in solution indicate a high (to 100%) stabilization which appears to be in conflict with visual observations. The behavior of photocurrent with time varies depending upon whether a negative or positive value of applied potential is involved.

Photoconductivity and photosensitivity of a CdIn2S4 monocrystal

Photoconductivity spectra for a CdIn2S4 halogen transport-grown crystal were recorded at RT with different levels of sulphur annealing, in order to understand the remarkable differences obtained by previous workers. Comparing our results with recent theoretical calculations of band structure and recent absorption studies, we conclude that excess sulphur plays a prominent role on the photosensitivity of this material and that it probably was the main cause of the different reported values of band gap transition.

Electron Paramagnetic Resonance of Two Stoichiometry‐Induced Intrinsic Defect Centres in CuGaS2

AbstractRelated to the sulphur annealing conditions, two different EPR signals are observed in CuGaSg2 With liquid sulphur, an isotropic photosensitive line is observed at g = 2.024 ± 0.002. With gaseous sulphur, an anisotropic spectrum, independent of light excitation, is recorded with g∥[001] = 2.114 ± 0.005 and g ⊥ [001] = 2.005 ± 0.005. The suggested models for the intrinsic centres correspond respectively to a hole trapped on a copper vacancy and to a S molecule ion. The formation of both centres, important for the electrical compensation processes in CuGaS, is justified by the molecular composition of sulphur as a function of its physical state.

Effects of temperature upon the thermophysical properties of materials for sintered guides of internal combustion engine valves

1. It has been established that the thermal conductivity of alloys sulfidized by the addition of sulfur in powder form to starting powder mixtures is higher, by 7–14% at 100°C and 30–40% at 600°C, than that of the same alloys sulfidized by a process consisting of impregnation in molten sulfur and subsequent annealing. 2. The specific heats and coefficients of linear expansion of alloys sulfidized by these two methods are approximately equal. 3. Comparison of the two methods of sulfidizing of iron-copper-carbon bearing alloys (see Paragraph 1) reveals the superiority of the method involving the addition of powdered sulfur to starting powder mixtures, which enables higher thermophysical properties to be attained and does not necessitate an additional operation in the manufacture of parts.