M. Dongol

On the structure of As2Te3 glass

X-ray scattering has been used to investigate the structure of glassy As2Te3, prepared by quenching in liquid nitrogen. The result of the coherent scattered x-ray intensity proved that the medium-range order (MRO) is very weak, and this was attributed to the higher metallic nature of the glass. Analysis of the first two peaks in the curve of the total radial distribution function, T(r), revealed that the short-range order (SRO) in the glassy state is different from that in the crystalline state, and that the first coordination sphere includes As–As and Te–Te bonds in addition to the As–Te bonds.

Effects of copper content and heat treatment on the electrical properties of Ge15Te85-xCux thin films

Abstract The mechanism of incorporation of copper in amorphous films of Ge15Te85−x Cux (0≤x≤7 at.%) system and the effect of heat treatment are studied by measuring the dc conductivity in the temperature range (150–423 K). The results indicates that there are two conduction mechanisms. For temperature above 330 K, conductivity exhibits activated behaviour, while in low temperature range (T=150–300 K) conductivity exhibits non-activated behaviour. In the high temperature region, resistance and the activation energy have been calculated. The decrease in the activation energy on addition of Cu has been interpreted according to the Kastner model. In the low temperature region Motts parameters have been evaluated and they are decreased with Cu content; the results in this region are interpreted following Motts model.

Effect of composition on the electrical and structural properties of As–Te–Ga thin films

Abstract As30Te70−xGax (x=0.5, 1, 3, 6 and 10xa0at.%) chalcogenide thin films were studied. Specimens of thickness 2500xa0A were used for resistivity (ρ) measurements as a function of temperature (T) in the temperature range from 300 to 443xa0K. The resistivity (ρ) exhibits an activated temperature dependence in accordance with the relation ρ(T)=ρ 0 exp(Δ E / kT) . It was found that the activation energy for conduction (ΔE) and room temperature resistivity (ρ300) decrease with increasing Ga content up to 3xa0at.%. For x greater than 3xa0at.%, it was found that ΔE and ρ300 increase with increasing Ga content. The results were discussed according to the valence alternation pair (VAP) model and the alloying effect. Thermal annealing above Tg was found to decrease ρ and ΔE. The decrease of ρ and ΔE after annealing at T>Tg was attributed to the amorphous–crystalline transformation. XRD, SAED, TEM and DSC were used to study the structure of the as-deposited and annealed films.

Erratum to: The effect of long term aging on the structural and optical properties of nano metallo-tetraphenylporphine films

Thickness of 200 nm of NiTPP film is prepared by thermal evaporation technique under vacuum 10−6 torr as a candidate of nano metallo-tetraphenylporphine to study long aging. The prepared films are amorphous in nature while the aged samples were nano-structured with a crystallite size of 19 and 53 nm. An enhancement of crystallinity was seen after 6 months aging, while further aging showed structural stability. SEM micrograph confirms XRD results. Optical gap as well as optical constants and dispersion parameters are calculated; its values are increasing except the dispersion parameters are vice versa. The obtained changes are attributed to the enhancement of ordering because of aging time.