Lamellar twinning in semiconductor nanowires

Multiple lamellar {111} twins are observed in GaAs, GaP, and InAs nanowires synthesized by supercritical fluid-liquid-solid (SFLS) and solution-liquid-solid (SLS) approaches. All of these nanowires have zinc blende (cubic) crystal structure and grow predominantly in the < 111 > direction. The twins bisect the nanowires perpendicular to their growth direction to give them a "bamboo"-like appearance in TEM images. In contrast, Si and Ge nanowires with < 111 > growth direction do not exhibit {111} twins, even though this is a common twin plane with relatively low twin energy in diamond cubic Ge and Si. However, Si and Ge nanowires with < 112 > growth directions typically have several {111} twins extending down the length of the nanowires. Here, we present a semi quantitative model that explains the observed twinning in III-V and IV nanowires.