Effect of γ-irradiation on the sheet resistance of two-dimensional island platinum films

Abstract

Four sets (A, B, C, and D) of two-dimensional island platinum films were prepared via the thermal evaporation technique. The mass thicknesses of the films of the different sets are 1, 5, 10, and 20 A, respectively. The sheet resistance of these films was found experimentally from knowing the d.c. resistance of the films. Before exposing the films to γ-rays, we monitored the increase in the sheet resistance in air with time (aging) till short-term stability for the films was achieved. The stabilized films were exposed to γ-rays such that the different doses are 100, 200, 300, 500, and 700 Gy using 137Cs (0.662 MeV) radiation source with dose rate 0.5 Gy/min. It was found that; (i) the sheet resistance of the investigated films decreases with the increase in the dose, (ii) for any particular mass thickness, the value of the fractional change in sheet resistance increases with the increase in dose, (iii) for any particular dose the increase in the fractional change in sheet resistance becomes more pronounced with the increase in mass thickness. Qualitative interpretation for our results was given on the ground that γ-rays changed the shape of islands from spherical to prolate.