Date of Award

1-1-2014

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Nanoscale Science and Engineering

Program

Nanoscale Sciences

Content Description

1 online resource (xi, 72 pages) : color illustrations.

Dissertation/Thesis Chair

Vincent P LaBella

Committee Members

James Lloyd, Kathleen Dunn, Carl Ventrice Jr., Christian Witt

Keywords

Interfaces (Physical sciences), Emission spectroscopy, Scanning tunneling microscopy, Surfaces (Physics), Semiconductors, Diodes, Schottky-barrier

Subject Categories

Nanoscience and Nanotechnology

Abstract

A fundamental understanding of charge transport across metal/semiconductor interfaces is of great technological and scientific importance. Metal/semiconductor, or Schottky barrier devices are widely utilized in sensing applications and power electronics. Additionally, Schottky barriers appear in resistive memory technology and current transistor technology. Although Schottky interfaces are ubiquitous, the effects of spatially variant interfaces on the measured Schottky barrier height (SBH) are not entirely understood. For these reasons it is necessary to explore the spatial variation at Schottky interfaces at the nanoscale. Ballistic electron emission microscopy (BEEM) is a three terminal scanning tunneling microscopy (STM) technique used to measure hot carrier transport through materials and across interfaces. BEEM has been used to directly measure the SBH with nanoscale spatial resolution, displaying the natural SBH inhomogeneity. This work explores the utility of SBH mapping with BEEM in identifying interface composition with electrostatic measurements. In the context of the band gap of the semiconductor, a self-consistent test of SBH measurement is presented for Cu/Si(001), Ag/Si(001), and Au/Si(001) diodes. This was accomplished by comparing the sum of the measured SBHs of p-type and n-type samples to the band gap of Si. These measurements are taken at 80 K and verify agreement with the Bell-Kaiser (BK) t to the SBH. Additional 11.7 nm resolution SBH mapping was performed on Au/Ag/Si(001) diodes at 80 K. It was found that the SBH in regions rich in Ag surrounded by Au was raised due to pinch-off effects. Pinch-off is treated in the context of an electrostatic perturbation and is shown to have considerable impact on the samples in this study. By analyzing the statistical distribution of the local SBH, the interface chemical composition is approximated from the relative SBH contribution. The ballistic electron emission microscopy (BEEM) data agreed with Rutherford backscattering spectrometry (RBS) and x-ray photo-emission spectroscopy (XPS) depth profile measurements.

Download

Share

COinS