Ge nanostructuring by Sn ion implantation

The production of Ge_1-xSn_x alloy nano-structures through high fluence Sn ion implantation at room temperature and subsequent rapid thermal annealing was investigated. Implant energy was set at 45 keV, aiming to produce a <;100 nm thick nano-structured layer. Three high Sn implantation fluences were tested: 5×1015, 1×10¹⁵, 5×10¹⁴ at/cm². First ion implantation was carried out at liquid nitrogen temperature in order to avoid nanostructured Ge film formation and to test further processing in absence of nanostructures. An 11 nm thick SiN_x capping layer was deposited to prevent Sn out-diffusion. The samples were annealed in N₂ atmosphere at 300°C and at 600°C, resulting in the formation of a uniform layer of Ge_1-xSn_x alloy with a tin concentration of x=5.2% and a good degree of crystallinity. The best annealing recipes were then applied to the nano-structured sample in order to produce a Ge_1-xSn_x nanostructured layer. First results show that the same thermal budget used to form the uniform Ge_1-xSn_x alloy layer cannot be easily applied to anneal nano-structures since an early melting was observed.