Electrical and microstructural properties of N+ ion-implanted ZnO and ZnO:Ag thin films

ZnO and Ag-doped ZnO films were grown on sapphire (0001) substrates by pulsed-laser deposition in vacuum both with and without oxygen at 700 degrees C. N+ ions were implanted in these films at room temperature and at 300 degrees C to a dose of 1 x 10(14) cm(-2) at 50 keV. Hall measurements indicate that ZnO films deposited in vacuum without oxygen and implanted with N+ at elevated temperatures are p-type with a hole-carrier concentration of 6 x 10(16) cm(-3), a mobility of 2.1 cm(2) V-1 s(-1), and a resistivity of 50 Omega cm. Both scanning-electron microscopy and transmission-electron microscopy studies on the implanted films reveal microstructural differences in grain size, surface roughness, and the nature of defects, which may impact the activation of N atoms as p-type carriers. Low-energy ion implantation at elevated temperatures is shown to be an effective method to introduce p-type N dopants into ZnO, which minimizes defect clustering and promotes defect annihilation during implantation. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3554836]