Effect of neutron irradiation on the structural, electrical and optical properties evolution of RPLD VO2 films

Madiba IG, Émond N, Chaker M, Khanyile BS, Tadadjeu SI, Zolliker P, Izerrouken M, Matinise N, Braun A, Nkosi M & Maaza M

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 443, 25-30.

https://doi.org/10.1016/j.nimb.2019.01.039

Abstract

This study reports on the effect of neutron irradiation at different fluences on the properties of VO2 thin films. The irradiations were performed at NUR research reactor, Algiers at a temperature of about 40 °C, with fast neutron fluence (En > 1 MeV) up to 1.9 × 1018 n.cm−2. The induced defects have been investigated using structural, optical and electrical measurements. Both bulk sensitive characterization techniques, Raman and grazing incident angle X-ray diffraction (GIXRD) analysis, show that no structural transformation is induced by neutron irradiation, although strain induced defect production are generated throughout the films while surface sensitive techniques, X-ray photoelectron spectroscopy (XPS) and work function measurements, show that the charge carrier (electron) concentration at room temperature decreases after irradiation. Potentially due to fast neutron irradiation induced defects, mainly in the form of Frenkel pairs, swelling and color center formation occurs in VO2 thin films without amorphization. This is further corroborated by an increase of the room temperature resistivity through the irradiated films. Temperature-dependent electrical and optical transmission measurements confirm that the characteristic semiconductor-to-metal transition of the VO2 films is preserved upon irradiation. We therefore conclude that VO2 is an excellent candidate for thermal shielding and thermal management of small satellites.