AVS 61st International Symposium & Exhibition
    Thin Film Thursday Sessions
       Session TF+PS-ThM

Paper TF+PS-ThM4
High-Quality ZnO Thin Films Grown by a New CVD Method using Catalytically-generated High-energy Precursors

Thursday, November 13, 2014, 9:00 am, Room 307

Session: Advanced CVD and Chemical Vapor Infiltration Methods
Presenter: Kanji Yasui, Nagaoka University of Technology, Japan
Authors: T. Nakamura, Nagaoka University of Technology, Japan
Y. Ohashi, Nagaoka University of Technology, Japan
N. Yamaguchi, Nagaoka University of Technology, Japan
E. Nagatomi, Nagaoka University of Technology, Japan
T. Kato, Nagaoka University of Technology, Japan
K. Yasui, Nagaoka University of Technology, Japan
Correspondent: Click to Email
ZnO is useful for many applications, and various growth techniques, including MBE [1-2], PLD [3, 4], and MOCVD [5], have been used to prepare ZnO films. Despite the advantages of MOCVD in industry, ZnO deposition by conventional MOCVD consumes a lot of electric power to react the source gases and raise the substrate temperature. To overcome this, a more efficient means of reacting oxygen and metalorganic source gases is needed.

In this paper, a new CVD method for ZnO film growth using the reaction between dimethylzinc (DMZn) and high-temperature H2O produced by a catalytic reaction on Pt nanoparticles is presented [6]. H2 and O2 gases were admitted into a catalyst cell containing a Pt-dispersed ZrO2 catalyst, whose temperature increased rapidly to over 1300 K due to the exothermic reaction of H2 and O2 on the catalyst. The resulting high-temperature H2O molecules were ejected from a fine nozzle into the reaction zone and allowed to collide with DMZn ejected from another fine nozzle. ZnO epitaxial films were grown directly on a-plane sapphire substrates at substrate temperatures of 773-873 K with no buffer layer. Growth rates were 0.02-0.13 μm min-1, and film thicknesses were 2-8 μm. X-ray diffraction patterns exhibited intense (0002) and (0004) peaks. The smallest FWHM value of the ω-rocking curve of ZnO(0002) was less than 0.1º (194 arcsec). The Hall mobility and residual carrier concentration of the epilayers were in the ranges 140-197 cm2V-1s-1 and 5.8×1016-6.0×1017 cm-3 at 300K, respectively. This Hall mobility is very large compared with ZnO films grown directly on sapphire by other deposition methods. PL spectra at 10 K showed a strong emission peak at 3.360 eV, attributed to the neutral donor-bound exciton Dox. The FWHM was as low as 0.9 meV, which is smaller than that previously reported for ZnO obtained by MBE (5.5 meV) [4], and by PLD on a sapphire(0001) substrate (1.7 meV at 2K) [3]. .

[1] M. Sano et al., Jpn. J. Appl. Phys., 42 (2003) L1050. [2] H. Tampo et al., Appl. Phys. Lett., 84 (2004) 4412. [3] E. M. Kaidashev et al., Appl. Phys. Lett., 82 (2003) 3901. [4] A. Ohtomo et al., Semicond. Sci. Technol., 20 (2005) S1. [5] J. Dai et al., J. Cryst. Growth, 290 (2006) 426. [6] K. Yasui et al., MRS Symp. Proc., 1494 (2013) 127