Structural and optical studies of the discontinuous behaviour of Te thin films subjected to He implantation

Electron microscopy investigations of tellurium thin films implanted with singly ionized He ions have revealed the appearance of a large number of surface structures when N_s, the number of implanted ions per unit area within the films, exceeds 0.2×10¹⁵ ions/cm² at a beam energy of 32 keV. This coincides with an observed discontinuity in the optical properties of the Te thin films and with a sudden decrease in the degree of orientation of the thin films as measured by X-ray diffraction. The same type of behaviour is observed for implantations with variable ion-beam energies and a fixed N_s of 0.5×10¹⁵ He ions/cm², with a discontinuity apparent near a value of 30 keV.