Annealing of ion implanted CdZnO

Abstract

We have studied the effect of the Cd content on the recovery of ion-induced damage in wurtzite CdxZn1−xO (x ⩽ 0.05) films and compared with that in pure wurtzite ZnO and rock-salt CdO. 200 keV Au+ and 55 keV Ar+ ion implants were performed at room temperature in the dose range of 5 × 1014–6.5 × 1015 cm−2. Rutherford backscattering/channelling spectrometry was used to characterize the damage evolution in the course of annealing (600–900 °C in air). A complex defect annealing behaviour is revealed in CdZnO as a function of annealing temperature, Cd content and ion dose. In particular, defects in the low dose implanted CdZnO films can be effectively removed at 800 °C, while the high dose implantation results in the formation of defects stable at least up to 900 °C. Moreover, annealing of the CdZnO films is accompanied by Cd loss at the surface for temperatures exceeding 800 °C. In contrast, CdO exhibits a typical damage accumulation behaviour for metals and semiconductors with high degree of ionicity, resulting in saturation and extended defect formation at high ion doses. These extended defects in pure ZnO and CdO, formed either directly during implantation or by reconstruction during post-implant annealing, are substantially more stable compared with small defects which can be efficiently removed at 700 °C and 600 °C for ZnO and CdO, respectively.