11 research outputs found
Effect of Plasma Irradiation on films
The effect of plasma irradiation is studied systematically on a 4H polytype
(002) oriented stoichiometric film having compressive residual
stress. Plasma irradiation was found to change the orientation to (110) of the
film at certain moderate irradiation distances. A linear decrease in grain size
and residual stress was observed with decreasing irradiation distance (or
increasing ion energy) consistent with both structural and morphological
observations. The direct optical energy gap was found to increase
linearly at the rate with the compressive stress. The
combined data of present compressive stress and from earlier reported tensile
stress show a consistent trend of change with stress. The
iodine-iodine distance in the unit cell could be responsible for the observed
change in with stress.Comment: 13 pages and 10 fi
Grain size dependent optical properties of CdI
The optical properties (refractive index and optical energy gap) were studied as a
function of film thickness, substrate temperature and heat-treatment temperature for
structurally, compositionally and morphologically well characterized CdI2 films grown
by thermal evaporation. The variation of residual stress in the film (determined by X-ray diffraction), grain size (D), refractive index (n) and optical energy gap (Eg) was
observed to be different in the above three cases. Combining the results of all three
experiments, the grain size dependence of n and Eg was derived. Variation of n with
grain size may be attributed to the changing packing density of crystallites with grain
size and its distribution consistent with SEM results. Eg was found to decrease with D
non-linearly and the data fits well with the equation of the type either or The variation of Eg with D could be attributed as due to the defect densities in the film
Flux trapping in hafnium-doped Y-Ba-Cu-O ceramics: the microwave-loss-signal analysis
Studies of microwave absorption at low fields in zero-field-cooled (ZFC) and field-cooled (FC) samples of Hf-doped Y-Ba-Cu-O are presented. Flux trapping during the FC process is clearly demonstrated. Results show that the superconducting glass phase appears in ceramics for fields greater than or equal to Hm (where Hm is the field at which the signal is maximum), where the difference between ZFC and FC signals starts. The results can be explained quite satisfactorily in terms of a percolation description and the superconducting cluster model