Selective growth of Ge nanowires by low-temperature thermal evaporation

High-quality single-crystalline Ge nanowires with electrical properties comparable to those of bulk Ge have been synthesized by vapor-liquid-solid growth using Au growth seeds on SiO(2)/Si(100) substrates and evaporation from solid Ge powder in a low-temperature process at crucible temperatures down to 700 °C. High nanowire growth rates at these low source temperatures have been identified as being due to sublimation of GeO from substantial amounts of GeO(2) on the powder. The Ge nanowire synthesis from GeO is highly selective at our substrate temperatures (420-500 °C), i.e., occurs only on Au vapor-liquid-solid growth seeds. For growth of nanowires of 10-20 µm length on Au particles, an upper bound of 0.5 nm Ge deposition was determined in areas of bare SiO(2)/Si substrate without Au nanoparticles.