Growth and Transfer of Monolithic Horizontal ZnO Nanowire Superstructures onto Flexible Substrates

Abstract

A method of fabricating horizontally aligned ZnO nanowire (NW) arrays with full control over the width and length is demonstrated. A cross‐sectional view of the NWs by transmission electron microscopy shows a “mushroom‐like” structure. Novel monolithic multisegment superstructures are fabricated by making use of the lateral overgrowth. Ultralong horizontal ZnO NWs of an aspect ratio on the order of ten thousand are also demonstrated. These horizontal NWs are lifted off and transferred onto a flexible polymer substrate, which may have many great applications in horizontal ZnO NW‐based nanosensor arrays, light‐emitting diodes, optical gratings, integrated circuit interconnects, and high‐output‐power alternating‐current nanogenerators.

One-dimensional ZnO nanostructures: Solution growth and functional properties

“…Chemical reactions in aqueous systems are usually considered to be in a reversible equilibrium, and the driving force is the minimization of the free energy of the entire reaction system, which is the intrinsic nature of wet chemical methods [56]. Wurtzite structured ZnO grown along the c axis has high energy polar surfaces such as ± (0001) surfaces with alternating Zn 2+ -terminated and O 2--terminated surfaces [28].…”

“…This configuration has normally been observed using gas phase synthesis approaches [14,31,[164][165][166], and is not favorable using aqueous approaches because-as discussed previously-wet chemical methods are usually considered to be under thermodynamic equilibrium, and the driving force is the minimization of the free energy of the entire reaction system [56]. However, there have been several reports of the synthesis of rectangular cross-sectional ZnO nanobelts by wet chemical methods, even though they were not necessarily growing along the non-polar directions.…”

“…Also, to make use of the lateral expansion, multi-segment monolithic ZnO superstructures were demonstrated, as shown in Fig. 31(c) [56]. Figure 31 (a) From a crystal structure point of view, wurtzite structure ZnO has a six-fold symmetry at its basal surfaces and a two-fold symmetry at its side surfaces.…”

“…The final morphology and dimension of the nanostructures are determined by a competition between adsorption and desorption of the precursor molecules, or in other words crystal growth and dissolution processes [56,184]. At the initial stage, the growth rate is relatively high because of the high supersaturation degree of growth nutrient.…”

“…(b) A 60° tilt view of thick (top row) and thin (bottom row) ZnO nanowire arrays growing out of 2 μm by 400 nm and 2 μm by 200 nm openings, respectively [280]. (c) A 30° tilted view of the horizontal nanowire-array-based five-segment monolithic superstructures [56]. Reproduced with permission An electron beam could also be used to directly generate ZnO nanowires by writing on a zinc naphthenate resist [287].…”