Yukinori Nose

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 N2 plasma generated near atmospheric pressure with small O2 concentration (O2%) below 1%. In the optical emission (OE) spectra of the plasma, OE lines corresponding to the NO-γ system ( A2Σ+→X2Πγ+) were observed, despite the only introduced gases being N2 and O2; these vanish at an O2% 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 °C and at an O2% of below 1% in the presence of the NO-γ system. This plasma yielded almost the same growth rate for ZnO films as O2 plasma including atomic O radicals that are often observed in low-pressure O2 plasma, suggesting that some highly reactive oxidant was sufficiently generated in such a small O2%. ZnO films synthesized using this plasma exhibited excellent (0001) preferred orientation without other diffractions such as 101¯1 diffraction, and with an optical bandgap of 3.30 eV. Based on the analy...

Orientation Control of ZnO Films Deposited Using Nonequilibrium Atmospheric Pressure N2/O2 Plasma

Nonequilibrium atmospheric pressure N2/O2 plasma was applied to the chemical vapor deposition (CVD) of zinc oxide (ZnO) films on glass substrates at the substrate temperature of 200 °C. Although the deposition temperature is very low, the ZnO films showed (0001) preferred orientation including a small amount of diffraction from the (1011) plane. We attempted to improve the (0001) preferred orientation for ZnO films without increasing the substrate temperature. After systematic experiments, we found that adjusting the ratio of the oxygen flow rate in the total gas flow rate [O2/(O2+ N2) ratio] was effective for orientation control of the ZnO films. This result indicates the potential of nonequilibrium atmospheric pressure N2/O2 plasma for the low-temperature CVD process of ZnO films used in piezoelectric devices and transparent thin-film transistors on a flexible substrate.