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Title: Ultraviolet laser crystallized ZnO:Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency

One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that UVLC dramatically improves the electron mobility, while the carrier concentration decreases which in turn simultaneously increases conductivity and transparency. AZO films under optimized UVLC achieve the highest electron mobility of 79 cm{sup 2}/V s at a low carrier concentration of 7.9 × 10{sup +19} cm{sup −3}. This is realized by a laser crystallization induced decrease of both grain boundary density and electron trap density at grain boundaries. The infrared (IR) to mid-IR range transmittance spectrum shows UVLC significantly enhances the AZO film transparency without compromising conductivity.
Authors:
;  [1] ;  [2] ;  [3] ;  [1] ;  [2] ;  [2]
  1. School of Industrial Engineering, Purdue University, 315N. Grant St, West Lafayette, Indiana 47907 (United States)
  2. (United States)
  3. Goodrich Corporation, UTC Aerospace Systems, 100 Wooster Heights Road, Danbury, Connecticut 06810 (United States)
Publication Date:
OSTI Identifier:
22300197
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ABSORPTION; ALUMINIUM ADDITIONS; CRYSTAL DEFECTS; CRYSTALLIZATION; DOPED MATERIALS; ELECTRIC CONDUCTIVITY; ELECTRON MOBILITY; ENERGY BEAM DEPOSITION; FILMS; GRAIN BOUNDARIES; LASER RADIATION; OPACITY; PULSED IRRADIATION; SAPPHIRE; SPECTRA; TRAPS; ULTRAVIOLET RADIATION; X-RAY DIFFRACTION; ZINC OXIDES