Toward nanoxerography on silicon oxide : tip induced oxidation, surface charge retention, and charge directed vapour phase deposition

Abstract

Nanoxerography is the method by which particles in the region 1-100nm can be selectively assembled on a surface through the use of a charge pattern, necessitating a substrate that can receive and hold a charge. Silicon oxide has such properties as well as being a material of significant interest within the electronics industry and in nanotechnological settings, but has not, as yet, been used for nanoxerography. Before an attempt at nanoxerography on silicon oxide, it was necessary to determine optimal parameters for charge storage on silicon oxide, the literature indicating oxide thickness to be key. Tip induced oxidation (TIO) was employed to locally vary oxide thickness after characterisation of physical and electrical properties.

Characterisation of TIO platforms was performed using atomic force microscopy showing that TIO produced oxides, while different from the native oxide, were sufficiently similar for nanoxerography. Growth parameters of TIO through an oxide layer were found to be similar to parameters of TIO on bare silicon. Through this investigation dielectric breakdown appeared to play a role in TIO, and the method of breakdown depends on whether AC or DC TIO is used.

Surface charge retention was investigated on ultrathin TIO oxide platforms revealing that lateral charge spreading was independent of oxide thickness, while diffusion through the oxide depended on thickness. The surface properties were shown to have a significant impact on the rate of surface charge diffusion; changing the substrate to sapphire, or applying a bilayer of didodecyldimethylammonium bromide (DDAB), significantly altered charge diffusion.

Nanoxerography was attempted in liquid environments using DDAB liposomes two different ‘developer’ solutions – water and ethanol – neither proving ideal. Vapour phase deposition of DDAB was shown to be a viable method for creating a bilayer of DDAB on silicon oxide and vapour phase nanoxerography using DDAB was shown to achieve partially selective deposition.