Nanoscale paraffin layer fabricated using spin coating technique for on-demand removable passivation

Abstract

Passivation is an essential process in the research and application of reactive and air-sensitive materials, and there has been an increasing demand to develop materials for stable but readily removable temporary passivation layers. Paraffin coating has been suggested as a possible candidate for such applications, which, however, further requires the demonstration of thin paraffin coating with complete surface coverage as well as effective depassivation performance. In this study, we demonstrate on-demand removable passivation using nanoscale paraffin layers fabricated using a spin-coating technique. Based on the Emslie Bonner and Peck's and Mark-Houwink-Sakurada (MHS) equations, eicosane and hexane were selected as the solute and solvent, respectively, to ensure low viscosity for the fabrication of nanoscale paraffin layers, facilitating depassivation process under a vacuum. Optimizing the solution concentration and spin speed generates nanoscale paraffin layers with complete surface coverage, which is confirmed through optical microscopic images and subsequent image processing using Python. The simple removal of the nanoscale paraffin layer through vacuum treatment allows us to revisit a passivated surface underneath, and subsequent contact resistance and x-ray photoelectron spectroscopy measurements evince the suppressed surface oxidation of paraffin-coated silicon samples. These results further attest to the applicability of paraffin coating as an on-demand removable passivation technique.