Cone-shaped structures of GeO2 fabricated by a thermal evaporation process

We have synthesized cone-like GeO2 structures via thermal heating of Ge powders.We have investigated the effects of substrate temperature on the sample morphology, revealing that cone-shaped structures are preferentially obtained at higher temperature. The cone-shaped structures, which gradually become thinner to form a sharp tip, appear to be a single-crystalline, hexagonal structure of GeO2. Room-temperature photoluminescence measurement revealed two emission peaks, at about 2.78 and 3.04 eV.