On the redistribution of 10keV hydrogen in CuInSe₂

Abstract

20keV H⁺ ₂, corresponding to 10keV H, was implanted at room temperature into Bridgman-grown single crystalline CuInSe₂ at doses of 1 × 10¹⁵, 1 × 10¹⁶, and 1 × 10¹⁷H/ cm². Using the ¹⁵N nuclear reaction method, the hydrogen depth profile was studied in order to investigate the hydrogen diffusion mechanism and to estimate a diffusion coefficient. The hydrogen depth distribution in the as-implanted samples revealed considerable deviations from the expected ballistic range profiles. The H redistribution was simulated by a numerical computer calculation. The best fit between measurements and simulations was obtained by assuming that

(a) this material does not contain intrinsic deep traps for the mobile hydrogen implants

(b) this material contains a broad distribution of intrinsic shallow and additionally irradiation-induced surface-near traps

(c) the detrapping efficiency from these traps decreases with increasing dose, and

(d) the depth distribution of these shallow traps ranges from the surface down to about 400 nm depth, i.e. beyond the hydrogen range.

Subsequent thermal annealing up to 200°C for half an hour led to minor changes of the hydrogen profiles at the highest implantation dose, and to major changes at the intermediate dose of 10¹⁶ cm⁻². All the changes of the hydrogen depth distributions can be described by the same set of assumptions, though their numerical values differ somewhat from the as-implanted case, due to additional thermal hydrogen mobility.