Surface morphology and optical properties of MeV-energy heavy-ion irradiated crystalline Si and crystalline Ge: Possibility of formation of porous material

The effect of bombardment of crystalline Si (c-Si) and crystalline Ge (c-Ge) with 75MeV Ni+, Ge+ and Ag+ ions at room temperature and liquid-nitrogen temperature (LNT) at fluences in the range of 1 × 1013-1 × 1014 ions cm−2 has been investigated. The ion-induced damage brought about by electronic and nuclear energy losses on the surface and deep inside the bulk, has been monitored by scanning electron microscopy and optical spectroscopy. In an optical study, the effect has been studied by measuring the reflectivity R and transmittance T in the spectral range 200–2500 nm and by determining the optical constants, namely the absorption coefficient α and refractive index n. These studies indicate that the surface morphological changes depend strongly on the temperature of bombardment and the nature of the projectile ion. The most striking effect in both the crystals is seen with Ni + -ion bombardment at LNT, while no appreciable effect is observed with Ag+ ions. The possibility of the formation of electronic energy-loss-induced porous Si and Ge on the surface of the irradiated c-Si and c-Ge is revealed in this study.