High-quality thickness-tunable InAs nanowire crosses grown by molecular-beam epitaxy

InAs nanowire crosses show great potential applications in detection and braiding of Majorana zero modes. Controlled growth of high-quality and diameter tunable InAs nanowire crosses is fundamental for these applications. However, it is still difficult to freely and conveniently adjust the diameter of the free-standing InAs nanowire crosses grown by the conventional growth methods. Here, we report a new technique to realize the growth of high-quality thickness-tunable InAs nanowire crosses by molecular-beam epitaxy. GaAs nanowire crosses were firstly grown on the Si (100) substrates spontaneously by merging the <111>-oriented GaAs nanowires. InAs nanowire crosses were then obtained by in situ growth of InAs shells on the facets of GaAs nanowire cross cores. Detailed scanning and transmission electron microscopic observations and energy dispersive spectrum analyses confirm that the InAs nanowire crosses grown by this manner have continuous and smooth morphology and they are high-quality zinc-blende crystals. More importantly, the InAs shell is grown with the vapor-solid growth mechanism and the thickness of the InAs nanowire crosses can be tuned by varying the InAs shell growth time. Our work provides a valuable method for the controlled growth of thickness-tunable semiconductor nanowire crosses.