The amorphization of a-quartz by bombardment with light and medium ions was investigated by means of Rutherford back-scattering spectrometry channelling, resonant nuclear reaction analysis and mechanical surface profiling. Monocrystalline samples were bombarded with 10 to 100keV H+, N+, Ne+ or Na+ ions, at 77K, to fluences of up to 1016/cm2. Resultant disordering of the quartz was found to occur via the 3-dimensional nucleation and growth of defect agglomerates, and perhaps small spatially-separated amorphous zones in the surrounding crystalline material. The nucleation rate was related to the energy density which was deposited in elastic collisions. Above a critical energy density of 1.92eV/atom (corresponding to 0.04dpa), deposited by nuclear collisions, a coherent amorphous layer formed at the depth of maximum energy deposition. This then grew towards the surface, and towards greater depths, during continued bombardment. Mechanical surface profiling revealed the presence of large compressive stresses (of the order of 1.5GPa). These built up at low fluences and were then released at higher fluences when the amorphous layer extended as far as the surface. Such stress release was accompanied by a significant (about 19%) reduction in the atomic density.

F.Harbsmeier, W.Bolse: Journal of Applied Physics, 1998, 83[8], 4049-53