Doctoral Dissertations

Wentao Qin

Abstract

"This thesis focuses on direct space nanocrystallography in 3-dimension (3D) via high-resolution transmission electron microscopy (HRTEM). It comprises three topics, each of which is presented in a chapter. Chapter 2 describes the development and application of an analytical technique to determine the lattice parameters of a nanocrystal from direct space images taken at two tilts. The development mainly involves choosing two appropriate viewing directions to resolve the lattice structure in 3D. General principles for establishing data acquisition protocols as well as certain protocols for some simple and popular lattices are presented. In the application of one of the protocols, the lattice parameters of a 10 nm f.c.c. WC1-x crystal are determined. The significance of this technique lies in that it provides 3D crystal lattice structure information, and possesses the atomic-resolution of 1IRTEM. In Chapter 3. a semi-empirical model for predicting lattice fringe visibility after tilt is presented. It is based on studying the relative positions of the reciprocal lattice spots of the diffracting lattice plane set and the Ewald sphere in 3D. Modified versions of the model enable predicting the invisibility of the lattice fringes and quantifying the probability of such an invisibility after tilt. A new concept of visibility band of a set of lattice planes of a spherical crystal is introduced. The ensemble of visibility bands of a nanocrystal, the visibility band map, is like a roadmap to guide direct space nanocrystallographic analyses in 3D. In this sense, a visibility band map is much like a Kikuchi map. and in principle contains the solutions to all the problems encountered in the thesis. In Chapter 4. both the probability of success and the uncertainties of reciprocal lattice vectors in applying the stereo analysis technique described in Chapter 2 are quantified. The relationship to calculate the size of a reciprocal lattice spot was determined, and it is the key to obtaining numeric solutions to all the problems encountered in the thesis. Improvement of the probability of success and reduction of reciprocal lattice vector uncertainties are discussed"--Abstract, page iv.

Advisor(s)

Fraundorf, Philip B.
Hale, Edward Boyd

Committee Member(s)

James, William Joseph
Feldman, Bernard J.
Newkirk, Joseph William
Pringle, Oran Allan
Siriwardane, Haresh

Department(s)

Physics

Degree Name

Ph. D. in Physics

Comments

Dissertation completed as part of a cooperative degree program with the University of Missouri--Rolla and the University of Missouri--St. Louis.

Publisher

University of Missouri--Rolla

Publication Date

Fall 2000

Pagination

xxxii, 143 pages

Note about bibliography

Includes bibliographical references (pages 129-142).

Rights

© 2000 Wentao Qin, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type

text

Language

English

Thesis Number

T 7866

Print OCLC #

47153812

Download
Off-campus S&T users

Share My Dissertation If you are the author of this work and would like to grant permission to make it openly accessible to all, please click the button above.

Share

 
COinS