Scanning tunneling microscopy of quasi-one-dimensional charge-density wave materials
Gammie, Gordon
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/20448
Description
Title
Scanning tunneling microscopy of quasi-one-dimensional charge-density wave materials
Author(s)
Gammie, Gordon
Issue Date
1991
Doctoral Committee Chair(s)
Tucker, John R.
Department of Study
Electrical and Computer Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Physics, Condensed Matter
Engineering, Materials Science
Language
eng
Abstract
Scanning tunneling microscopy (STM) has been used to study the atomic and electronic structures of quasi-one-dimensional charge-density wave (CDW) materials. The two materials chosen for this study, NbSe$\sb3$ and o-TaS$\sb3$, exhibit numerous interesting characteristics associated with the formation and motion of the CDW. The purpose of these studies is to determine if the surface characteristics are sufficiently similar to the bulk characteristics to learn something about the microscopics of CDWs and their dynamics.
Room temperature studies of NbSe$\sb3$ show that at least two different surface structures are possible. The first is a slightly relaxed form of the bulk crystal structure, while the second suggests the presence of an additional atom on the type-I chains. The detailed structure of o-TaS$\sb3$ is not known, but STM studies show that it is more closely related to the ZrSe$\sb3$ structure than that of NbSe$\sb3$ and m-TaS$\sb3$, as had previously been assumed. The difference in the strength of the chalcogen pairing in the chains of o-TaS$\sb3$ is much less than that of m-TaS$\sb3$, with all chains exhibiting intermediate strength pairing.
Low temperature studies of the two surfaces of NbSe$\sb3$ show that the relaxed surface forms a faint CDW, while the adatom surface does not. One-dimensional fluctuations above the CDW transition temperature in o-TaS$\sb3$ can be seen in STM images. Below the transition, the CDW is imaged and agrees well with the known wavevector. There are two uniformly distributed CDW maxima per unit cell along the b$\sb{\rm o}$-axis which, in conjunction with the room temperature lattice images, explains some of the differences between the CDW characteristics of o-TaS$\sb3$ and m-TaS$\sb3$. All attempts to slide the CDW on the surfaces of these materials have been unsuccessful.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
