Preparation of p-type ZnO thin films by RF diode sputtering

A p-type ZnO thin film was prepared by RF diode sputtering and nitrogen doping. Deposition in plasma N
₂
gas source increases the N solubility and thus the incorporation of N
_o
acceptor that is responsible for p-type conductivity of the ZnO films. Raman analyses performed in back scattering configuration proved the incorporation of the nitrogen acceptor N
_o
into ZnO:N. Raman spectra show E
₂
mode and two nitrogen related local vibrational modes (LVMs) typical for N-doped ZnO. Minimum resistivity of 790 Omegacm, a Hall mobility of 22 cm
²
V
^-1
s
^-1
and the carrier concentration of 3.6 times 10
¹⁴
cm
^-3
were obtained at 75 %N
₂
in Ar/N
₂
sputtering gas. X-ray diffraction measurements (XRD) showed that ZnO:N films had the preferential orientation of (002) plane at 25 %N
₂
and of (100) plane for higher N
₂
concentrations. The average grain size was from 7 to 42 nm for all Ar/N
₂
ratios. ZnO:N films exhibit relatively high microstrains (10 times 10
_-3
)