Improvement and Investigation of Silicon Nanowire "Grow-In-Place" Approach

Open Access
Author:
Winter, Christopher Aylwin
Graduate Program:
Engineering Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 18, 2011
Committee Members:
  • Stephen Fonash, Thesis Advisor
  • Stephen Joseph Fonash, Thesis Advisor
  • Jun Huang, Thesis Advisor
  • Jerzy Ruzyllo, Thesis Advisor
Keywords:
  • silicon nanowire
  • growth
Abstract:
For nearly a decade silicon nanowires have been the subject of intense research. Future integration of silicon nanowires into commercial devices requires the development and further refinement of methods for synthesizing and assembling these nanowires into densely packed rational structures with high accuracy and repeatability. Current methods have two broad classifications: “grow-and-place” and “grow-in-place”. The former procedure involves forming the nanowires away from their final orientation, harvesting them from this growth area, and finally placing them in desired positions. The latter procedure sidesteps the problems associated with the harvesting and placement steps of the “grow-and-place” method by forming the nanowires in their final preferred arrangement. In this thesis, we propose a novel self-assembling variation of the “grow-in-place” approach for SiNW growth where the interfacial area of the nanochannel template interface can be formed out of various materials. This research has improved on our group’s previous in-template “grow-in-place” approach by growing SiNWs with smooth morphology and good electrical properties upon partial exposure while still retaining the benefits of the original “grow-in-place” approach, including good control of the SiNW size, number, orientation, position, and shape. The SiNWs grown using this approach were found to be morphologically smooth, composed of crystalline silicon and exhibited good electrical characteristics. Additionally, in this thesis we explore the use of a metal adhesion layer as a means of controlling SiNW electrical characteristics. Specifically, this thesis compared iii electrical characteristics of SiNWs grown using aluminum or titanium as an adhesion layer versus SiNWs grown without an adhesion layer and found that the SiNWs grown with aluminum or titanium as an adhesion layer were, on average, 6 or 9 times, respectively, more conductive than the SiNWs grown without an adhesion layer. Finally, this thesis presents evidence that nanowires grown using built-in platinum contacts form in a dual-material structure. This evidence is in the form of high- magnification FESEM images. It is suggested that, in the inter-contact region, the platinum silicide grew as the “shell” of the nanowire structure and that the core remained silicon because of the physical configuration of the nanochannel.