Effect of temperature and discharge voltage on the properties of Co-doped ZnO thin films deposited by pulsed electron beam ablation

Abstract

Cobalt-doped ZnO (CZO) thin films have been deposited from CoxZn1-xO (x=0.20) target on Si (100) substrate by pulsed electron beam ablation (PEBA). The effects of process temperature (350°C–800°C) and electron beam acceleration voltage (15kV, 16kV) on the deposited films have been assessed. The films have been prepared at constant beam pulse frequency (2Hz) and Argon background pressure (∼3mTorr). The structure and surface morphology of CZO films have been investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). As per SEM data, the results show that the films consist of Co rich nano-sized globules (∼20nm–300nm). Energy dispersive x-ray (EDX) measurements reveal that Co content in the films seems to be unaffected by accelerating voltage while it increases with temperature in the range 350°C–450°C. At higher deposition temperatures (600°C & 800°C), the films exhibit faceted particles and are relatively rough. The films deposited at 800°C consist of a predominantly Co phase. X-ray photoelectron spectroscopy (XPS) data confirm the presence of metallic cobalt in the films, whose content increases with temperature but is practically unaffected by beam voltage. X-ray diffraction (XRD) analysis confirms the presence of herxagonal close-packed (hcp) metallic cobalt in the films.