Metastable Ge_1–<i>x</i>C_<i>x</i> Alloy Nanowires

Carbon-containing alloy materials such as Ge_1–<i>x</i>C_<i>x</i> are attractive candidates for replacing silicon (Si) in the semiconductor industry. The addition of carbon to diamond lattice not only allows control over the lattice dimensions, but also enhances the electrical properties by enabling variations in strain and compositions. However, extremely low carbon solubility in bulk germanium (Ge) and thermodynamically unfavorable Ge–C bond have hampered the production of crystalline Ge_1–<i>x</i>C_<i>x</i> alloy materials in an equilibrium growth system. Here we successfully synthesized high-quality Ge_1–<i>x</i>C_<i>x</i> alloy nanowires (NWs) by a nonequilibrium vapor–liquid–solid (VLS) method. The carbon incorporation was controlled by NW growth conditions and the position of carbon atoms in the Ge matrix (at substitutional or interstitial sites) was determined by the carbon concentration. Furthermore, the shrinking of lattice spacing caused by substitutional carbon offered the promising possibility of band gap engineering for photovoltaic and optoelectronic applications