PhD DEFENSE: Ruby Lai

Ph.D. Candidate: Ruby Lai
Research Advisor: Yi Cui

Date: Monday, June 4, 2018
Time: 1pm
Location: McCullough 335

Title: Thin Silicon and Metal-Assisted Chemical Etching for Photovoltaic and Electronic Devices

Abstract: Ultrathin silicon membranes, less than 20um thick, have extreme flexibility, lightness, and the superior materials quality and advantages for photovoltaic and electronic devices. There are two major roadblocks in developing ultrathin silicon membranes: the fabrication processing of the more delicate material in traditional CMOS fabrication, and the manufacturing of high quality, ultrathin sheets from bulk Si material. I present experiments tackling these issues and related device applications.  

First, I use alkaline silicon etching of silicon wafers to form ultrathin silicon sheets, supported by a thick ring of Si material on its edge, that enable facile processing of large 3" sheets in traditional CMOS apparatuses. Second, I explored the novel use of a "chemical wafer-saw" for silicon by using metal-assisted chemical etching, as a possible pathway to create thin silicon sheets. Next, I developed a new theoretical model for the mechanism of metal-assisted chemical etching of silicon, which explained for the first time the silicon doping dependence of the etch. Lastly, I present computational design and fabrication of a novel nanophotonic solar cell contact for a metal-insulator-semiconductor solar cell, as well as other nanostructures, fabricated using metal-assisted chemical etching