Physico-Chemical nanomaterials science

Mathematical model of mechanically stimulated changes of irradiated silicon crystals’ surface conductivity 

Lys R.M., Pavlyk B.V., Didyk R.I., Shykorjak J.A., Slobodzyan D.P., Kushlyk M.O.
Department of Sensor and Semiconductor Electronics, Ivan Franko National University of Lviv. Str. Tarnavskoho, 107, Lviv-79017, Ukraine. 
E-mail: lys_r@ukr.net

Mechanical properties of silicon, as well as, other semiconductors are mainly determined by the subsystem state of structural defects. Under the influence of irradiation, radiation defects play a major role in changing the characteristics. Monocrystals of p-Si were used to study the changes in the electrical conductivity of silicon in the course of the action of a single-acting elastic load and X-radiation. 
According to our previous studies, the formula for surface conductivity (λ = 1/R) can be written as follows:
 			(1)
where a, l – the size of the sample; D – absorbed dose; σ – mechanical load; µp(σ,D) – holes mobility; w – thickness of space-charge region.
 			(2)
p1(y,D) is a component that corresponds to a change in the concentration of charge carriers with a change in the distance from the surface of the semiconductor; p2(σ)  is a component that shows how much the concentration of holes decreases due to capturing them at dislocations during mechanical loads.
If we substitute in equation (1) the following expressions for a non-irradiated sample:
 	(3)
			(4)
we can get a theoretical curve that almost coincides with the experimental one. By reducing the mobility of holes by 5 %, the coefficient β2 – by 39 %, and by increasing β1 – by 4.34 %, the theoretical dependence of conductivity on the mechanical load can be obtained for irradiated specimens.