Novel chemical vapor deposition process of ZnO films using nonequilibrium N2 plasma generated near atmospheric pressure with small amount of O2 below 1%

We propose a novel chemical vapor deposition (CVD) process of ZnO films involving a nonequilibrium N-2 plasma generated near atmospheric pressure with small O-2 concentration (O-2%) below 1%. In the optical emission (OE) spectra of the plasma, OE lines corresponding to the NO-c system (A(2)Sigma(+) -> X-2 Pi(+)(gamma)) were observed, despite the only introduced gases being N-2 and O-2; these vanish at an O-2% of more than 1%. ZnO films were grown on a glass substrate placed in the plasma at a growth temperature of as low as 200 degrees C and at an O-2% of below 1% in the presence of the NO-c system. This plasma yielded almost the same growth rate for ZnO films as O-2 plasma including atomic O radicals that are often observed in low-pressure O-2 plasma, suggesting that some highly reactive oxidant was sufficiently generated in such a small O-2%. ZnO films synthesized using this plasma exhibited excellent (0001) preferred orientation without other diffractions such as 10 (1) over bar1 diffraction, and with an optical bandgap of 3.30 eV. Based on the analyses of the plasma and the exhaust gases, the coexistence state of NO-gamma and O-3 should be essential and useful for the decomposition and oxidation of Zn source material in the proposed CVD process. Published by AIP Publishing.