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eng http://hdl.handle.net/2142/20448 Restriction data tranferred 2014-07-01T11:19:18-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9210808 (UMI)AAI9210808 Tucker, John R. Gammie, Gordon 2011-05-07T12:39:29Z 2011-05-07T12:39:29Z 10000-01-01 1991 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. Made available in DSpace on 2011-05-07T12:39:29Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9210808.pdf: 3231128 bytes, checksum: 6f5e9b4d44f13a14227743b637a2d996 (MD5) Previous issue date: 1991 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:43:58Z Item is restricted indefinitely. Copyright 1991 Gammie, Gordon Engineering, Electronics and Electrical Physics, Condensed Matter Engineering, Materials Science Scanning tunneling microscopy of quasi-one-dimensional charge-density wave materials text Electrical and Computer Engineering Electrical Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.