NANOWIRE-BASED DEVICES FOR ELECTRONIC AND OPTICAL APPLICATIONS: SOLUTION-GATED SILICON NANOWIRE FIELD EFFECT TRANSISTORS AND ONE-DIMENSIONAL GOLD NANOPARTICLE ARRAYS

Open Access
Author:
Hu, Wenchong
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
July 19, 2010
Committee Members:
  • Theresa Stellwag Mayer, Dissertation Advisor
  • Theresa Stellwag Mayer, Committee Chair
  • Christine Dolan Keating, Committee Member
  • Joan Marie Redwing, Committee Member
  • Douglas Henry Werner, Committee Member
Keywords:
  • cumtomizable gold nanoparticle array
  • field effect transistor
  • silicon nanowire
  • pH sensor
  • stabililty
Abstract:
This thesis research investigated nanowire-based devices and structures for electronic and optical applications. Solution-gated silicon (Si) nanowire field effect transistors (NWFETs) were investigated to add new functionality to Si complementary metal oxide semiconductor integrated circuits. Axially doped n+-p--n+ Si nanowires grown by the vapor-liquid-solid technique were integrated and optimized for robust and reliable operation in a buffer solution. The stability of the electrical response at a constant pH value as well as the sensitivity to changes in pH were significantly improved by using a stack of thermal silicon dioxide (SiO2) and atomic layer deposited aluminum oxide (Al2O3) as the gate dielectric as compared to a SiO2 gate dielectric alone. These devices exhibited reproducible response, consistent threshold voltage, low subthreshold swing, long-term stability, high pH sensitivity, and gate voltage dependent dynamic range. The integration and measurement strategy described in this thesis lays the groundwork for future multiplexed nanobiosensor chips based on arrays of Si NWFETs. A new nanofabrication technique was developed to convert high-aspect-ratio Si nanowires into free-standing one dimensional (1D) arrays of Au nanoparticles encapsulated in a SiO2 shell. The diameter and the interparticle spacing of the Au nanoparticles in the array were defined by tailoring the sidewall profile of the starting Si nanowire to have a scalloped pattern with controllable peak-to-valley distances (or scalloping wavelength). During the thermal oxidation of Au-coated Si nanowires, the Au migrates to the core of the oxidized Si wire to form a Au wire with a diameter that follows the undulation of the original scalloped profile. With increasing thermal treatment, the Au wire breaks into separate teardrop-shaped segments in the regions of the wires having the smallest diameter, and is converted from a teardrop shape into a spherical particle to reduce the total surface area and thus the surface energy of the entire nanostructure. This powerful new synthesis method enables the fabrication of free-standing 1D Au nanoparticle array encapsulated in a uniform SiO2 shell with controlled Au particle diameter and interparticle spacing. This opens the door to many new plasmonic optical devices based on noble metal nanoparticle arrays.