Radiation Damage and Amorphization Mechanisms in Xe⁺ Irradiated CuInSe₂ Single Crystals

Abstract

The damage evolution in ion bombarded CuInSe2 single crystal has been studied using the RBS/channelling analysis with 2MeV He+ ions. 40keV Xe+ ions were implanted with fluences in the range from 1013 to 1016 cm'2 and an ion current density of 1.9|iA/cm2 at room temperature. It was found that the radiation accumulation follows a linear function in a double logarithmic plot with slope m=1.5. The saturation level of the damage was achieved at a fluence of about 1015 cm'2 A heterogeneous mechanism of the damage accumulation in the CuInSe2 crystal irradiated with ions with mass equal to or greater than xenon mass is suggested.

Surface Composition of CIS Compound Affected by Xe⁺ Irradiation

“…Copper deficiency of the samples was determined by the depth increase. It could indicate the highly absorbing layers production [11]. At the depth ≈2.6 µm there could be seen elements redistribution in the surface composition: copper concentration increases, indium and selenium concentration decreases.…”

“…By the absorbing layer formation (both during film growth and by etching or surface annealing) [11] structure damage of sample near-surface, as can be seen in Fig. 3, there is a 65 nm thick layer with the structure defects which shade the true value of the elements concentration behind the damage layer.…”

“…One of the methods to determine the radiation resistance of products is to study influence of inert gases ions (with the mass equal to that of Xe or more) on the radiation damage accumulation and on the samples surface composition based on the CIS compound [11]. With that aim in view, the Rutherford backscattering/channelling (RBS/C) technique of helium ions with their channelling along 221 axis which helps to establish the localization of extrinsic and displaced atoms, to get radiation damage profiles, the depth and thickness of the damage layer was applied.…”

“…The energy detector resolution was 25 keV, the depth resolution was ≈35 nm. To study the fluence dependence on CIS system composition of the group B, samples were affected by the 40 keV Xe + ion irradiation with the fluences: 1 × 10 13 , 3 × 10 13 , 10 14 , 3 × 10 14 , 10 15 , 3 × 10 15 cm −2 [11]. To determine the composition of the subsurface layer samples (behind the damage layer, the analyzed depth was ≈65 nm), we used the iteration method [21].…”

“…Besides, defect formation in this layer by both deposition and operation can result in degradation as well as solar elements efficiency rise [10][11][12][13][14][15][16][17][18][19]. This indicates insufficient investigation of defect creation in the CuInSe 2 films system and poor knowledge of these processes that does not allow to realize CIS potential in full.…”