Fabrication of Uniformly Arrayed Single- and Multi-Directional Slanted Cu Nanorods

Abstract

Uniformly arrayed single-and multi-directional slanted Cu nanorods on a Si substrate were fabricated using a template of slanted channel structures. The single-directional slanted Cu nanorods were obtained using slanted channel structures oriented at an angle of 15 • with respect to the surface normal. Double-and quadruple-directional slanted Cu nanorods were obtained using double-and quadruple-directional slanted channel structures, respectively. The double-directional Cu nanorods were symmetrically slanted at 30 • , preserving the architecture of the slanted channel structures. The quadruple-directional slanted Cu nanorods had pyramidal structures, with slanted rods positioned at 30 • from the surface normal to the right, left, front, and back. and photocatalysts. Template-based electrochemical deposition is generally employed for the growth of Cu nanorods. Anodic aluminum oxide (AAO) templates have been widely used for fabricating Cu nanorods because the material typically possesses a relatively uniform pore distribution. 2,3,8,9,10 With the templating method, the diameter and periodicity of the Cu nanorods can be precisely controlled by adjusting the characteristics of pores in the templates. The method is relatively simple and inexpensive; however, the angles of the Cu nanorods are limited by the use of vertical structures, which are perpendicular to the substrate surface.Slanted Cu nanorods have been used in heat-transfer devices, 5,6 and have potential applications in the above-mentioned fields. Oblique angle deposition has been used exclusively for the fabrication of slanted Cu nanorods. 5,11,12 The oblique angle deposition technique is based on deposition at oblique anlges, where the trajectories of the incident vapor fluxes are directed off-normal (oblique) to the substrate. [13][14][15] Self-shadowing occurs in the initial nucleation stage, preventing film growth in these regions. The resulting film is inclined in the direction of the vapor source. By rotating the substrate properly, the angle and shape of the structures can be controlled. In oblique angle deposition, the control of the process parameters is relatively simple and various metallic sources can be used. However, extremely precise control over the surface angle is required and the deposited films are usually porous. Controlling the periodicity of the columnar structures in a large area is also difficult, because the columns easily aggregate with each other during deposition.6,11 Şeşen et al. reported that slanted Cu nanorods fabricated by oblique angle deposition were disadvantageous for heat-transfer devices because the denser Cu nanorods, which formed film-like rod structures, acted as thermal resistors.6 Therefore, it is important to control the periodicity and angle of slanted Cu nanorods for use in the above-mentioned applications.Recently, a slanted plasma etching technique for the fabrication of single-and multi-directional slanted channel structures was reported. 16 Because slanted plasma etching can be performed under practical p...