2 research outputs found
Guided Growth of Horizontal GaN Nanowires on Spinel with Orientation-Controlled Morphologies
We report the guided growth of horizontal
GaN nanowires (NWs) on
spinel (MgAl<sub>2</sub>O<sub>4</sub>) substrates with three different
orientations: (111), (100), and (110). The NWs form ordered arrays
with distinct morphologies on the surface of the substrates, controlled
by the interaction with the substrate. The geometry of the NWs matches
the symmetry of the spinel surfaces: on MgAl<sub>2</sub>O<sub>4</sub>(111), (100), and (110) the NWs grow in six, four, and two directions,
respectively. The epitaxial relations and morphologies of the NW–substrate
interface were characterized by cross-sectional transmission electron
microscopy. The substrate was found to be mobilized during the growth
and either climb up or recede on/under one or two sides of the NW,
depending on the substrate orientation. Possible reasons for the similarity
and differences between the orientations of the NWs and thin GaN films
grown on MgAl<sub>2</sub>O<sub>4</sub> are proposed. These results
demonstrate the generality and flexibility of the guided growth phenomenon
in NWs and specifically show that MgAl<sub>2</sub>O<sub>4</sub>(111)
could be a low-mismatch substrate for the growth of high-quality GaN
layers and NWs
Guided Growth of Horizontal GaN Nanowires on Quartz and Their Transfer to Other Substrates
The guided growth of horizontal nanowires has so far been demonstrated on a limited number of substrates. In most cases, the nanowires are covalently bonded to the substrate where they grow and cannot be transferred to other substrates. Here we demonstrate the guided growth of well-aligned horizontal GaN nanowires on quartz and their subsequent transfer to silicon wafers by selective etching of the quartz while maintaining their alignment. The guided growth was observed on different planes of quartz with varying degrees of alignment. We characterized the crystallographic orientations of the nanowires and proposed a new mechanism of “dynamic graphoepitaxy” for their guided growth on quartz. The transfer of the guided nanowires enabled the fabrication of back-gated field-effect transistors from aligned nanowire arrays on oxidized silicon wafers and the production of crossbar arrays. The guided growth of transferrable nanowires opens up the possibility of massively parallel integration of nanowires into functional systems on virtually any desired substrate