Anisotropic optical band gap of (102)- and (002)-oriented films of red HgI2 - art. no. 245315

The thermally evaporated stoichiometric films of HgI2 show a preferred orie ntation of (102) and (002) parallel to substrate plane for film thicknesses below and above 1450 nm, respectively. The band gap determined by optical absorption shows the anisotropic nature of the two orientations with an ani sotropic ratio E-g(102)/E-g(002) = 0.86. The change in band gap with him th ickness in either orientation is attributed to the residual stress in the f ilm. An increase in the band gap with residual stress is observed for the ( 102) orientation as opposed to a decreasing band gap with stress for the (0 02) orientation. The annealing experiment carried out on the (102)-oriented film shows a switch over to the (002) orientation at 110 degreesC. The res ults of the annealing experiment support well the results of thickness depe ndence, viz., the anisotropic nature of the band gap at two orientations an d the residual stress-induced band gap change.