Effect of γ-irradiation on the temperature coefficient of surface resistivity of two-dimensional island platinum films

Three sets (A, B and C) of two-dimensional island platinum films (2D-I(Pt)Fs) were prepared via the thermal evaporation technique, where the substrates are corning 7059 glass slides. The mass thickness (dm) of the films of different sets is 5, 10 and 20 A, respectively. The Pt films were exposed to γ-rays from 137Cs (0.662 MeV) radiation source of dose rate 0.5 Gy/min. and the different doses are 100, 200, 300, 500 and 700 Gy. The dependence of the surface resistivity (ρ) on temperature over the range of 100-300 K was undertaken at different dm and doses then the temperature coefficient of surface resistivity (α) was deduced. It was found that; (i) for particular dm and T, the absolute value of α decreases as the dose increases (ii) for particular dose and T, the absolute value of α decreases as dm increases (iii) for particular dose and dm, the absolute value of α decreases as T increases. Qualitative interpretation for the results was offered on the ground that the electrons transfer among islands takes place by the activated tunneling mechanism and the γ-irradiation has changed the shape of islands from spherical to prolate spheroid.