Fabrication of high aspect-ratio metallic nanotube array with highly-ordered periodicity using HiPIMS

Abstract

Metal alloys are increasingly being used in the synthesis of nanostructures, such as nanotubes. This study was an attempt to expand the applicability of metallic nanotube arrays (MeNTAs) by fabricating structures with a high aspect ratio with the aim of increasing the active surface area. MeNTAs comprising thin-film metallic glass (TFMG) and bronze were fabricated via high-power impulse magnetron sputtering (HiPIMS) over a contact-hole array created using photoresist. MeNTAs were designed with 2 aspect ratios (2 and 4). MeNTAs with an AR of 2 were fabricated via single-layer deposition using both alloys. When fabricating MeNTA with an AR of 4, the resulting single-layer structures were unable to withstand the photoresist removal process, thereby necessitating the inclusion of a WNiB TFMG as the buffer layer for reinforcement. The percentage of intact AR 4 bronze MeNTA was far higher under multilayer deposition (98.4%) than under single-layer deposition (74%). Plasma diagnostic methods involving a Langmuir probe were used to monitor plasma properties (e.g., plasma potential, plasma density, electron temperature, and ion flux) during the deposition process. These results provide valuable reference for trench filling and the manufacture of nanostructures with a high aspect ratio using HiPIMS.