Influence of He-ion irradiation of ceramic AlN

Abstract

The paper presents results of studying the effect of irradiation of low-energy helium ions on structural properties and morphology of AlN polycrystalline ceramics. On the basis of X-ray diffraction patterns, dependences of the change in stresses in the structures of types I and II, as well as the magnitude of atoms displacements from lattice sites as a result of irradiation, were determined. According to the data obtained, with small irradiation fluences, characteristic of a low concentration of implanted helium ions and defects in the structure, the change in the magnitude of displacements and stresses is insignificant. An increase in fluence above 1017 ion/cm2 leads to a drastic change in distortions and deformations in the structure, as well as to an increase in the value of rms displacement of atoms from the lattice sites. It has been established that the greatest decrease in microhardness and resistance to stress is observed for samples irradiated with fluences above 1017 ions/cm2, which are characterized by the formation of a large concentration of defects and impurity inclusions. The decrease in microhardness is due to the formation of regions of disorder and helium bubbles, as well as a decrease in the density of ceramics and the degree of crystallinity.