Selective area grown ZnTe nanowires as the basis for quasi-one-dimensional CdTe-HgTe multishell heterostructures

Selective area growth is employed in the vapor-liquid-solid molecular beam epitaxy of ZnTe nanowire arrays. Full control over the location of the individual nanowires is achieved by defined positioning of the growth catalyst. This study addresses the influence of substrate material and growth temperature on the yield of vertical nanowires. The optimized procedure provides arrays of single-crystalline free-standing nanowires with a high ensemble uniformity. The nanowires exhibit a uniform shape with a diameter of about 80 nm and reach a length of more than $3\mu \text{m}$, which makes them suitable as substrates for core-shell nanowires of the topological insulator material HgTe.

Figure 1

ZnTe nanowires are grown under similar conditions at 440 ${}^{\circ }\text{C}$ on diverse (111)B substrate materials: (a) GaAs, (b) InAs, (c) ZnSe, and (d) ZnTe. These materials cover the different possible options regarding lattice mismatch and type of interface to the nanowire.

Figure 2

ZnTe nanowires are grown under similar conditions at different substrate temperatures: (a) 440 ${}^{\circ }\text{C}$, (b) 445 ${}^{\circ }\text{C}$, and (c) 450 ${}^{\circ }\text{C}$. The top images show an electron micrograph of a single nanowire, images at the bottom give an overview at lower magnification.

Figure 3

A transmission electron micrograph of a ZnTe nanowire is shown in (a), the insets are higher resolution images recorded at different positions along the wire. (b) shows elemental maps of the nanowire's tip obtained by energy dispersive spectroscopy.

Figure 4

The images show CdTe-HgTe shells on ZnTe core nanowires with (a) trigonal and (b) more circular cross section at the nanowire base. The arrow in (a) points out a gap in the HgTe shell.

Figure 5

Scanning electron micrographs of a cleaved ZnTe-CdTe/HgTe core-shell nanowire grown at 450 ${}^{\circ }\text{C}$ are shown, simultaneously recorded with (a) EsB and (b) InLens detector. A qualitative cross section of the nanowire is sketched as an inset, highlighting the polarity of the prominent side facets of core and shell.