Abstract
Future one-dimensional electronics require single-crystalline semiconductor free-standing nanorods grown with uniform electrical properties. However, this is currently unrealistic as each crystallographic plane of a nanorod grows at unique incorporation rates of environmental dopants, which forms axial and lateral growth sectors with different carrier concentrations. Here we propose a series of techniques that micro-sample a free-standing nanorod of interest, fabricate its arbitrary cross-sections by controlling focused ion beam incidence orientation, and visualize its internal carrier concentration map. ZnO nanorods are grown by selective area homoepitaxy in precursor aqueous solution, each of which has a (0001):+c top-plane and six {1–100}:m side-planes. Near-band-edge cathodoluminescence nanospectroscopy evaluates carrier concentration map within a nanorod at high spatial resolution (60 nm) and high sensitivity. It also visualizes +c and m growth sectors at arbitrary nanorod cross-section and history of local transient growth events within each growth sector. Our technique paves the way for well-defined bottom-up nanoelectronics.
Highlights
Future one-dimensional electronics require single-crystalline semiconductor free-standing nanorods grown with uniform electrical properties
ZnO nanorod arrays of Dw 1⁄4 100 and 500 nm are investigated by Scanning electron microscopy (SEM) observation and near-band-edge (NBE)/visible (Visible) CL imaging at 3.0 keV from bird’s-eye view angles (Fig. 1a,b)
Eight spot-CL spectra at corresponding e-beam spot positions 1–8 are shown in Fig. 1c, which are correlated by the same colour: position 1 at top þ c plane, positions 2–7 at side m plane from top to the bottom and position 8 on the ZnO þ c substrate covered with transparent polymethyl methacrylate (PMMA) film
Summary
Future one-dimensional electronics require single-crystalline semiconductor free-standing nanorods grown with uniform electrical properties This is currently unrealistic as each crystallographic plane of a nanorod grows at unique incorporation rates of environmental dopants, which forms axial and lateral growth sectors with different carrier concentrations. Electrical properties of a bottom-up nanocrystal and its device properties are reported assuming electrical uniformities This is idealistic because each crystallographic plane surface has an atomic arrangement with unique chemical activity (for example, etching rate[12,13], host crystal growth rate[14,15] and incorporation rates of point-defects), as is reported on plane-dependent donor concentration in ZnO bulk crystal[13,16] and amphoteric Si-doping in GaAs substrates[17,18]. Cross-sectional CL technique is not applied to any semiconductor free-standing nanocrystal up to now
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