Abstract

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(2)/V s at a low carrier concentration of 7.9 x 10(+19) cm(-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. (C) 2014 AIP Publishing LLC.

Comments

This is the publisher PDF of Nian, Q, Zang, MY, Schwartx, BD, and Cheng, GJ. "Ultraviolet laser crystallized ZnO: Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency." Applied Physics Letters, 104, 201907 (2014). Copyright AIP, available at http://dx.doi.org/10.1063/1.4879643.

Keywords

OXIDE THIN-FILMS, POLYCRYSTALLINE SILICON FILMS, ATOMIC LAYER DEPOSITION, ELECTRICAL-PROPERTIES, OPTICAL-PROPERTIES, ROOM-TEMPERATURE, ELECTRODES, STABILITY, SUBSTRATE, COATINGS

DOI

10.1063/1.4879643

Date of this Version

5-19-2014

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