Ion irradiation induced effects on the surface characteristics and electrical properties of Ge-Bi-Se thin films

In this study, the fabricated amorphous chalcogenide Ge10Se70Bi20 thin films were irradiated by nitrogen (N+), argon (Ar+), hydrogen (H+) and oxygen (O+) ion beams. The compositions of the pure and irradiated films were investigated using X-ray diffraction (XRD), which confirming the amorphous structures of the pristine and the irradiated Ge10Se70Bi20 thin films. The optical parameters such as optical bandgap, absorption edge, Urbach energy, Tauc parameter, and extinction coefficient of the un-irradiated and irradiated films were determined using UV/Vis spectroscopy. The energy gap is found to reduce from 1.355 eV for un-irradiated Ge10Se70Bi20 to 1.02 eV, 0.73 eV, 0.60 eV and 0.51 eV after irradiation by N+, Ar+, H+ and O+ beam respectively. While, the band tail is 0.12 eV of Ge10Se70Bi20, increased to 0.16 eV, 0.40 eV, 0.45 eV and 0.48 eV after irradiation by N,+ Ar+, H+and O+ respectively. In particular, the conductivity increased by two orders after the pristine film was exposed to oxygen beam. The dc electrical conductivity of the pristine film was increased from 1.5x10−7 to 1.4x10−5 Ω−1.cm−1 after irradiation by oxygen ion beam. Besides, the activation energy and Mott’s parameters for the original and irradiated Ge10Se70Bi20 films were deduced. The reported modifications on the optical and electrical parameters, propose that the irradiated Ge10Se70B20 thin films to be used in important applications, e.g., optical data storage and optoelectronic devices.