Doctoral Dissertations

Abstract

"Single crystals of strontium titanate implanted with boron were found to have highly conductive surface layers. The effects of varying dose from 1016 to 1017 ions/cm2, implantation voltage from 50 to 75 keV, and annealing conditions on the room temperature surface resistance and Hall mobility are presented in this study. A major result is that, for the most part, variation of the implantation voltage did not have a major effect on the sheet resistances obtained by boron implantation of strontium titanate, while dose and annealing conditions have major effects.

Doses of 5 X 1016 ions/cm2 required annealing on the order of one hour at 5(X) K for maximum reduction of the roan temperature resistance in the implanted layer. Samples implanted with a dose of 1 X 1017 ions/crn2 required slightly higher temperatures (approximately 575 K) to obtain a minimum resistance at roan temperature.

Long term (several weeks) roan temperature annealing was found to occur in high dose samples. After one to t\\X> months at roan temperature followed by an anneal to 575 K, the surface resistances were found to be lower than those produced by the annealing of a freshly implanted sample to 575 K. 1he conductance was found to be semi-metallic with surface resistances of 200 ohms/square after such anneals.

The average Hall mobility at roan temperature was found to be on the order of 4.8 cm2/volt-sec after annealing. Variations of between 2.8 X 1014 and 1.1 X 1016 electrons/cm2 were determined for the density of surface carriers. These correspond to doping efficiencies of between 0.5 and 11 % for the 100 keV implants and 1.7 and 7% for the 50 keV implants.

Comparisons between samples from different boules were found to yield different results under some conditions but not under other con­ditions. When the annealing temperature was below 625 K, final room temperature resistances were found to be independent of boule differences ana implantation conditions. Above this temperature, the densities of surface carriers were lower and wide variations in surface resistances measured at room temperature were observed. These differences were prob­ably due to differences in initial impurity concentrations among the different boules.

Differences in crystallographic orientation relative to the ion beam produced no major differences in the surface resistance"--Abstract, pp. ii-iii

Advisor(s)

Gerson, Robert, 1923-2013

Committee Member(s)

Levenson, L. L., 1928-1998
Parks, William F.
Hale, Edward Boyd
James, William Joseph

Department(s)

Physics

Degree Name

Ph. D. in Physics

Publisher

University of Missouri--Rolla

Publication Date

Spring 1981

Pagination

xi, 109 pages

Note about bibliography

Includes bibliographical references (pages 91-96)

Rights

© 1981 Connie MacDonald Cooper, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 4649

Print OCLC #

8660642

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