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Title: Transitions of bandgap and built-in stress for sputtered HfZnO thin films after thermal treatments

HfZnO thin films with various Hf contents are sputter-deposited on glass substrates from Hf{sub x}Zn{sub 1−x}O (x = 0, 2.5, 5, 7.5, and 10 at. %) targets at room temperature. The incorporation of Hf in the ZnO film leads to the amorphorization of the materials. The amorphous structures of high-Hf-content films remain after annealing at 600 °C for 30 min. The built-in stresses of as-deposited films are compressive. As the annealing temperature increases, the stresses are relaxed and even become tensile. The films exhibit a high transmission of 80% in the visible region. The optical bandgap increases with the Hf content, but it decreases with the annealing temperature. This can be attributed to the alteration of strain (stress) status in the films and atomic substitution. The reduction of bandgap partly results from the grain growth, which is due to the quantum confinement effect of the small grains. Hf doping increases the resistivity of ZnO owing to the disorder of the material structure and the higher bandgap, which result in more carrier traps and less thermally excited carriers in the conduction bands.
Authors:
;  [1] ;  [2]
  1. Institute of Applied Mechanics, National Taiwan University, Taipei City 10617, Taiwan (China)
  2. Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei City 10617, Taiwan (China)
Publication Date:
OSTI Identifier:
22218104
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 8; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; COMPRESSION STRENGTH; ELECTRIC CONDUCTIVITY; GRAIN GROWTH; HAFNIUM COMPOUNDS; SEMICONDUCTOR MATERIALS; SPUTTERING; STRAINS; STRESS RELAXATION; STRESSES; TEMPERATURE RANGE 0273-0400 K; TENSILE PROPERTIES; THIN FILMS; TRAPS; ULTRAVIOLET SPECTRA; ZINC OXIDES