Processing of hafnium oxide thin films by 2 MeV Kr ion beam for opto-electronic applications

Abstract

The ion irradiation on 100 nm and 200 nm HfO2 films was performed using a 2 MeV Kr8+ beam at three different fluences viz. 1.5 × 1015 ions/cm2, 2 × 1015 ions/cm2 and 2.5 × 1015 ions/cm2 and various characterization techniques were employed to analyze the as-deposited and irradiated films. The AFM analysis showed that contrary to 200 nm films, the surface roughness of 100 nm films increases with increasing the ion fluence as also validated by FE-SEM. For 100 nm films, the phase analysis done by XRD indicated that the pristine films co-exist in dual phases of cubic and monoclinic; which also prevailed with post-irradiation. However, the pristine 200 nm films coexisted in dual monoclinic and orthorhombic phases and changed to sole orthorhombic phase with increasing ion fluences. The pristine 200 nm film showed more conductivity, which decreases with increasing ion fluences. Interestingly, the optical reflectivity of as-deposited 200 nm film was higher than that of 100 nm film and upon ion irradiation, both films showed inverse trend of reflectivity change; in 100 nm thin films, it decreases with increasing ion fluences. Thus, the ion irradiation seems to be a fascinating tool to tailor HfO2 thin films for their device applications.