Controlled thinning and surface smoothening of silicon nanopillars

TL;DR

This paper presents a controlled method for thinning silicon nanopillars by forming an oxide shell and sacrificial coating, resulting in smooth, smaller-diameter pillars suitable for nanoscale electronic devices.

Contribution

A novel surface manipulation technique that precisely controls silicon nanopillar thinning and surface smoothness without altering original pillar dimensions.

Findings

Oxide shell thickness controlled from nanometers to hundreds of nanometers.

Produced smooth silicon pillars with less than 10 nm surface roughness.

Observed visible and infrared photoluminescence related to quantum confinement.

Abstract

A convenient method has been developed to thin electron beam fabricated Silicon nanopillars under controlled surface manipulation by transforming the surface of the pillars to an oxide shell layer followed by the growth of sacrificial ammonium silicon fluoride coating. The results show the formation of an oxide shell and a Silicon core without significantly changing the original length and shape of the pillars. The oxide shell layer thickness can be controlled from few nanometers up to few hundred nanometers. While down sizing in diameter, smooth Si pillar surfaces of less than 10 nm roughness within 2 {\mu}m were produced after exposure to vapors of HF and HNO3 mixture as evidenced by transmission electron microscopy (TEM) analysis. The attempt to expose for long durations leads to the growth of a thick oxide whose strain effect on pillars can be assessed by coupled LO-TO vibrational modes of Si-O bonds. Photoluminescence (PL) on the pillar structures which have been down sized exhibit visible and infrared emissions, which are attributable to microscopic pillars and to the confinement of excited carriers in Si core, respectively. The formation of a smooth core-shell structures while reducing the diameter of the Si pillars has a potential in fabricating nanoscale electronic devices and functional components.