Architectured van der Waals epitaxy of ZnO nanostructures on hexagonal BN

Abstract

Heteroepitaxy of semiconductors on two-dimensional (2-d) atomic layered materials enables the use of flexible and transferable inorganic electronic and optoelectronic devices in various applications. Herein, we report the shape-and morphology-controlled van der Waals (vdW) epitaxy of ZnO nanostructures on hexagonal boron nitride (hBN) insulating layers for an architectured semiconductor integration on the 2-d layered materials. The vdW surface feature of the 2-d nanomaterials, because of the surface free of dangling bonds, typically results in low-density random nucleation-growth in the vdW epitaxy. The difficulty in controlling the nucleation sites was resolved by artificially formed atomic ledges prepared on hBN substrates, which promoted the preferential vdW nucleation-growth of ZnO specifically along the designed ledges. Electron microscopy revealed crystallographically domain-aligned incommensurate vdW heteroepitaxial relationships, even though ZnO/hBN is highly latticemismatched. First-principles theoretical calculations confirmed the weakly bound, noncovalent binding feature of the ZnO/hBN heterostructure. Electrical characterizations of the ZnO nanowall networks grown on hBN revealed the excellent electrical insulation properties of hBN substrates. An ultraviolet photoconductor device using the vdW epitaxial ZnO nanowall networks/ hBN heterostructure was further demonstrated as an example of hBN substrate-based device applications. The architectured heteroepitaxy of semiconductors on hBN is thus expected to create many other device arrays that can be integrated on a piece of substrate with good electrical insulation for use in individual device operation.

Transferable single-crystal GaN thin films grown on chemical vapor-deposited hexagonal BN sheets

“…The position controls of one-dimensional semiconductor nanostructures on h-BN and graphene have also previously been examined using this preferable growth feature on plasma-treated 2D films. 18,19 More importantly, as confirmed by our TEM measurements, the GaN layers exhibited identical crystal orientations to those of the h-BN substrate, indicating GaN heteroepitaxy on h-BN (see Supplementary Figure S2). This semiconductor growth on CVD-grown and plasma-treated 2D films suggests that the problems of low growth yields on 2D substrates can eventually be solved when 2D substrates exhibit a high number of atomic cliffs.…”

In-situ pull-off of ZnO nanowire from carbon fiber and improvement of interlaminar toughness of hierarchical ZnO nanowire/carbon fiber hydrid composite laminates

“…Equilibrium separation D0 ≈ 4.0 Å, which is slightly larger than one diameter of carbon atom (3.851 Å) [34], will be used in evaluating the contribution of vdW attraction to the interfacial force at equilibrium. Calculations from recent density functional theory (DFT) also support this assumption albeit it is based on another but similar system (i.e., ZnO-BN system) [35]. It is well known that the functional groups, such as −NH2 and -OH, in PDA can covalently or non-covalently interact with various kinds of surfaces.…”

Centimeter-sized epitaxial h-BN films

“…[1][2][3][4] Furthermore, its remarkable mechanical strength makes it possible to use few-layered h-BN as a flexible and transparent substrate, which is ideal for next-generation electronics and optoelectronics in applications such as flexible and transparent transistors or light-emitting devices. [5][6][7][8][9] However, the difficulty of preparing high-quality large-area h-BN films has hindered their widespread use. While exceptionally clean and ordered h-BN layers can be prepared from bulk crystals by mechanical cleavage methods, 10,11 their limited sizes and random thicknesses and orientations are not suitable for practical device applications.…”