Surface energy-mediated construction of anisotropic semiconductor wires with selective crystallographic polarity

Abstract

ZnO is a wide band-gap semiconductor with piezoelectric properties suitable for opto-electronics, sensors, and as an electrode material. Controlling the shape and crystallography of any semiconducting nanomaterial is a key step towards extending their use in applications. Whilst anisotropic ZnO wires have been routinely fabricated, precise control over the specific surface facets and tailoring of polar and non-polar growth directions still requires significant refinement. Manipulating the surface energy of crystal facets is a generic approach for the rational design and growth of one-dimensional (1D) building blocks(1- 4). Although the surface energy is one basic factor for governing crystal nucleation and growth of anisotropic 1D structures, structural control based on surface energy minimization has not been yet demonstrated(5-9). Here, we report an electronic configuration scheme to rationally modulate surface electrostatic energies for crystallographic-selective growth of ZnO wires. The facets and orientations of ZnO wires are transformed between hexagonal and rectangular/diamond cross-sections with polar and non-polar growth directions, exhibiting different optical and piezoelectrical properties. Our novel synthetic route for ZnO wire fabrication provides new opportunities for future opto-electronics, piezoelectronics, and electronics, with new topological properties.