Direct Atomic Scale Imaging of III−V Nanowire Surfaces

Abstract

We have succeeded in direct atomic scale imaging of the exterior surfaces of III-V nanowires by scanning tunneling microscopy (STM). By using atomic hydrogen, we expose the crystalline surfaces of InAs nanowires with regular InP segments in vacuum while retaining the wire morphology. We show images with atomic resolution of the two major types of InAs wurtzite nanowire surface facets and scanning tunneling spectroscopy (STS) data. Ab initio calculations of the lowest energy surface structures and simulated STM images, agree very well with experiments.

Growth, structure and phase transitions of epitaxial nanowires of III-V semiconductors

“…On the other hand, the nucleus-vapour interfaces that form during nucleation at the TPL are clearly different and the corresponding energy may be lower for the WZ nucleus position [26], as also suggested by calculations showing that the specific energies of some extended facets are lower for WZ than for ZB [17][18][19]. From Eq.…”

“…The difference in cohesive energy between ZB and WZ bulk III-V materials is typically of a few tens of meV per III-V pair (24 meV for GaAs). Several ab initio calculations have shown that the total energy of NWs can indeed be lower in the WZ structure than in the ZB structure because of a lower specific energy of some specific sidewall facets [17][18][19] or of their vertical edges [20]. However, for the contributions of these 2D or 1D features to compensate the difference in bulk cohesive energies, the NWs must be very thin: the calculated critical radii under which WZ might be favoured over ZB are only of a few nm, whereas WZ is observed in NWs up to radii of several 100 nm.…”

Atomic resolution imaging ofin situInAs nanowire dissolution at elevated temperature

“…The nanowires were examined at 300 kV in an image-aberration-corrected FEI Titan 80-300 TEM equipped with a differentially-pumped environmental cell. Motivated by recent reports that the surfaces of similar nanowires can be cleaned using atomic hydrogen [4], the nanowires were examined at elevated temperature in a H 2 atmosphere.…”

Doping profile of InP nanowires directly imaged by photoemission electron microscopy

“…For more details on the atomic hydrogen cleaning see Ref. 12. Spatially resolved x-ray photoelectron spectroscopy (l-XPS) data from individual cleaned NWs, obtained by XPEEM, were compared to spectra averaged over homogeneously doped NWs using the high-energyresolution XPS setup, in order to ensure similar surface conditions.…”