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

Journal Article · Mon May 19 04:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4879643· OSTI ID:22300197

Nian, Qiong; Zhang, Martin Y. ^[1]; Schwartz, Bradley D. ^[2]

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1. School of Industrial Engineering, Purdue University, 315N. Grant St, West Lafayette, Indiana 47907 (United States)
2. Goodrich Corporation, UTC Aerospace Systems, 100 Wooster Heights Road, Danbury, Connecticut 06810 (United States)

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.

• OSTI ID: 22300197
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 20 Vol. 104; ISSN APPLAB; ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

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