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Title: Residual stress dependant anisotropic band gap of various (hkl) oriented BaI{sub 2} films

The thermally evaporated layer structured BaI{sub 2} grows in various completely preferred (hkl) film orientations with different growth parameters like film thickness, deposition rate, substrate temperature, etc. which were characterized by structural, morphological, and optical absorption measurements. Structural analysis reveals the strain in the films and the optical absorption shows a direct type band gap. The varying band gaps of these films were found to scale linearly with their strain. The elastic moduli and other constants were also calculated using Density Functional Theory (DFT) formalism implemented in WIEN2K code for converting the strain into residual stress. Films of different six (hkl) orientations show stress free anisotropic band gaps (2.48–3.43 eV) and both positive and negative pressure coefficients. The negative and positive pressure coefficients of band gap are attributed to the strain in I-I (or Ba-Ba or both) and Ba-I distances along [hkl], respectively. The calculated band gaps are also compared with those experimentally determined. The average pressure coefficient of band gap of all six orientations (−0.071 eV/GPa) found to be significantly higher than that calculated (−0.047 eV/GPa) by volumetric pressure dependence. Various these issues have been discussed with consistent arguments. The electron effective mass m{sub e}{sup *}=0.66m{sub 0} and the hole effective massmore » m{sub h}{sup *}=0.53m{sub 0} have been determined from the calculated band structure.« less
Authors:
; ;  [1]
  1. Thin Film Laboratory, Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India)
Publication Date:
OSTI Identifier:
22258764
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 19; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ANISOTROPY; DENSITY FUNCTIONAL METHOD; DEPOSITION; EFFECTIVE MASS; FILMS; LAYERS; ORIENTATION; PRESSURE COEFFICIENT; PRESSURE DEPENDENCE; RESIDUAL STRESSES; STRAINS; SUBSTRATES; THICKNESS