Residual Stress Dependent Optical Properties of ZnI2 Films

Abstract

The optical absorption measurements are reported for stoichiometic, tetragonally structured ZnI 2 films. The optical band gap was found to be of the direct type. Structural analysis shows a random orientation of crystallites and the presence of internal residual stress in the film. Non-uniform compressive residual stress shows an initial increase followed by saturation with film thickness and a linear increase with treatment temperature. Both these behaviors correlate well with the variation of packing density and size distribution of crystallites as a function of film thickness and treatment temperature as seen by morphological studies. The decreasing optical band gap (E g ) with either film thickness or treatment temperature can be explained by residual compressive stress. The thickness and treatment temperature data dependences together show quite a good linear relationship between E g and the residual stress yielding a band gap of 4.75 eV for a stress free perfect crystal.

Synthesis and Crystal Structure of Zinc Iodide in the Sodalite Cavities of Zeolite A (LTA)

“…10,11 In recent decades, the optical and structural properties of ZnI2 films have also been studied using optical-absorption measurement. 10,11 The optical band gap of ZnI2 films is the direct-type and shows thickness dependence related packing density and size distribution of crystallite grains. 10,11 A large decrease in band gap has been attributed to the large c/a and this result indicates the optical properties of group IIb iodides are changed by their crystal structures.…”

“…6 Group IIb iodides, ZnI2, CdI2, and HgI2, have been studied for their optical properties. 10,11 Specifically, HgI2 has been studied because of its optical properties and its utility as radiation detector and CdI2 has also been extensively researched due to its polytypism. 10,11 In recent decades, the optical and structural properties of ZnI2 films have also been studied using optical-absorption measurement.…”

“…10,11 Specifically, HgI2 has been studied because of its optical properties and its utility as radiation detector and CdI2 has also been extensively researched due to its polytypism. 10,11 In recent decades, the optical and structural properties of ZnI2 films have also been studied using optical-absorption measurement. 10,11 The optical band gap of ZnI2 films is the direct-type and shows thickness dependence related packing density and size distribution of crystallite grains.…”

“…10,11 The optical band gap of ZnI2 films is the direct-type and shows thickness dependence related packing density and size distribution of crystallite grains. 10,11 A large decrease in band gap has been attributed to the large c/a and this result indicates the optical properties of group IIb iodides are changed by their crystal structures. 10,11 In this work, we have attempted to synthesize ZnI2 clusters in a single crystal of zeolite A and to determine its structure.…”

“…10,11 A large decrease in band gap has been attributed to the large c/a and this result indicates the optical properties of group IIb iodides are changed by their crystal structures. 10,11 In this work, we have attempted to synthesize ZnI2 clusters in a single crystal of zeolite A and to determine its structure. This was done because the ZnI2 clusters in the unique-sized and regular three-dimensionally orientated cavities of zeolites are predicted to be advanced catalytic and optical materials.…”