A. N. Nigam

The X-ray K-absorption studies in glassy Se80Te20 and Se80Te10Sb10

Abstract X-ray K-absorption studies have been made in glassy Se 80 Te 20 and Se 80 Te 10 Sb 10 alloys and their amorphous films. It has been observed that the Se K-edge shifts towards the lower energy side in both alloys, shifting more in ternary alloy than in binary alloy. Our results are in agreement with the published work on infra-red and Raman spectroscopies.

X-ray spectroscopic studies in glassy semiconducting Ge20Se80 and Ge20Se80-xInx alloys

Abstract The shift of the K-absorption edge (ΔEK) is measured in ternary alloys of Ge20Se80-xInx with respect to the binary Se80Ge20 alloy. The results indicate that the K-edge of Se progressively shifts towards the lower energy side as the concentration increases from 0 to 10 at%. However at a higher concentration of In (χ > 15), the negative shift starts decreasing. The results are in accordance with Paulings concept of electronegativity and indicate that the nature of bonds is iono-covalent in character in these glasses, as found in many crystalline solids. The composition dependence of ΔEK is also discussed in terms of the structure of Ge-Se system.

X-ray spectroscopic studies of the glassy GexSe100−x system

Abstract X-ray K-absorption edges of germanium and selenium have been studied in glassy GexSe100−x (x=10, 15, 22 and 30). We find that the Ge K-absorption edge always shifts towards higher energies with respect to pure amorphous germanium whereas the Se K-absorption edge always shifts towards lower energies with respect to amorphous selenium. In both cases, the shift is found to be a minimum for the particular value x=22 which indicates some modifications in the structure at this composition.

Structural studies in Ge22Se68X10 (X=Bi, Sb) glasses and their amorphous films by X-ray spectroscopy

The X-ray K-absorption edges of Ge and Se in glassy Ge 22 Se 78 and Ge 22 Se 68 X 10 ( X = Bi, Sb) have been studied in bulk as well as in thin films. We find that the Ge K-edge shifts in bismuth-doped glassy alloy while the Se K-edge remains unchanged. However, in Sb-doped glassy alloy the Ge K-edge remains unchanged while the Se K-edge shifts towards the lower energy side. These results indicate that Bi-Ge bonding is favoured in Ge-Se-Bi and Se-Sb bonding in Ge-Se-Sb alloys.

The X-ray K absorption edges of Ge and Se in Ge22Se78−x Bi x glasses and amorphous films

Abstract The X-ray K absorption edges of Ge and Se in glassy Ge22Se78−x Bi x with x =0, 2 and 10 have been studied in bulk as well as in thin-film form. In both cases, we find that, at a low concentration of Bi (x =2), the Se K edge shifts while that of Ge remains unchanged. On the other hand, at a higher concentration of Bi (x = 10), the reverse happens. The results indicate different kinds of bonding at low and high concentrations of Bi. The results are in agreement with those of other workers who drew similar conclusions from the electrical properties.

X-ray K-absorption studies of glassy Ge22Se68M10 (M=Ag, Cd, In, Pb)

Abstract X-ray K-absorption studies of glassy Ge22Se78 and Ge22Se68M10 (M = Ag, Cd, In, Pb) have been made in order to understand the nature of bonding of metallic atoms in ternary alloys. The edge shift is found to be dependent on the difference in electronegativity between the metallic atoms and the Ge or Se atoms. The results are in agreement with Paulings concept of electronegativity and indicate that the nature of the bonds in these glasses is iono-covalent in character as found in many crystalline solids.

X-ray spectroscopic studies of photo-structural changes in glassy Se100-xTex

Recently it has been reported that reversible and irreversible photo-structural changes occur in amorphous chalcogenide glasses. The present paper reports an X-ray spectroscopic study of Se100-xTex (x=5 to 30) alloys before and after the light exposure. The results indicate that no change in Se K-edge occurs upto x=5 at%. However, at higher concentration of Te (x>5 at%), Se K-edge shifts towards higher energy side with respect to Se K-edge in unexposed sample. A high energy shift of the K-absorption edge of Se in the present case may, therefore, be related to photocrystallization due to light exposure. The results also indicate that the photocrystallization is highly composition dependent in Se100-xTex glassy system.

Radiation damping in an anharmonic oscillator

The effect of radiation damping in an anharmonic oscillator has been calculated using the technique of Kryloff and Bogolituboff. It is found that the intensity distribution of the emitted spectral line is asymmetric about its intensity maximum. The index of asymmetry agree with the experimental data on x-rayKa1,2lines.

Notizen: Sign Reversal of Thermo EMF on Hydrogen Diffusion in thin Nickel Foils

Abstract On cathodic hydrogen diffusion thin foils of nickel (6 micron thickness) show a sign reversal in their thermo electric power. The original value -17 μV/ °C changes to + 3μV/°C after diffusion. The results are interpreted in terms of a possible 4p band filling by the electrons donated by hydrogen. Annealed foils retain hydrogen longer than the unannealed ones.

Thermopower anisotropy in magnetic films of Co and Ni plated in presence of an external magnetic induction

Electroplated films of cobalt and nickel were grown on copper substrate both in absence and presence of external magnetic induction ranging from 25 to 72 gauss. The latter films showed a magnetic behaviour and an anisotropy in thermopower with respect to the direction of magnetisation.