MARC 主機 00000nam  2200349   4500 
001    AAI3120286 
005    20050428085952.5 
008    050428s2003                        eng d 
020    0496676587 
035    (UnM)AAI3120286 
040    UnM|cUnM 
100 1  Doty, Richard Christopher 
245 10 Electron transport, self-assembly, and electroluminescence
       of nanocrystal superlattices 
300    174 p 
500    Source: Dissertation Abstracts International, Volume: 65-
       01, Section: B, page: 0321 
500    Supervisor: Brian A. Korgel 
502    Thesis (Ph.D.)--The University of Texas at Austin, 2003 
520    In order to assess the potential applications of 
       nanotechnology, the fundamental properties of nanocrystals
       and the self-assembled arrays they form must be studied in
       detail. The electrical conductivity of monodisperse and 
       polydisperse Ag nanocrystal superlattices was measured as 
       a function of temperature. A fundamental difference 
       between polydisperse and monodisperse nanocrystal 
       superlattices was found. Polydisperse superlattices 
       displayed insulating behavior throughout the entire 
       temperature range. Monodisperse superlattices displayed a 
       metal-insulator transition that shifted to lower 
       temperatures for larger Ag nanocrystals. At temperatures 
       above the metal-insulator transition, the monodisperse 
       superlattices exhibited a positive temperature coefficient
       of resistance, characteristic of a metal. Below the metal-
       insulator transition, the temperature coefficient of 
       resistance was negative, characteristic of an insulator 
520    The ability to control the formation of complex, self-
       assembled nanocrystal superlattices is very important for 
       potential electrical and optical applications. With the 
       correct concentration and size ratio, nanocrystals with a 
       bimodal size distribution can self-assemble into LmSn 
       structures. The formation of 2D monolayers of these 
       complex structures was studied by performing random 
       sequential adsorption (RSA) simulations of tethered hard 
       disks that are able to undergo limited Monte Carlo surface
       diffusion. Nanocrystal size ratios of 0.155, 0.414, and 
       0.533 were examined. Melting simulations of perfect LmSn 
       structures reveal that RSA kinetics frustrate superlattice
       ordering, creating a kinetic bottleneck to ordered LmSn 
520    One of the more promising applications for nanocrystals is
       light emitting diodes (LEDs). Si nanocrystals synthesized 
       by thermal decomposition of phenylsilane precursors in a 
       supercritical hexane solution with and without the 
       addition of octanol, which serves as a capping ligand, 
       were used as the emitting layer in an LED. 
       Electroluminescence from these Si nanocrystal LEDs was 
       reddish-orange or white depending on the reaction 
       conditions of the nanocrystal synthesis. The current-
       voltage behavior was characteristic of space-charge 
       limited current, and the devices exhibited relatively low 
       turn-on voltages (∼6--7 V). External quantum 
       efficiencies varied between 10-5 and 10-4% 
590    School code: 0227 
590    DDC 
650  4 Engineering, Chemical 
650  4 Engineering, Materials Science 
690    0542 
690    0794 
710 20 The University of Texas at Austin 
773 0  |tDissertation Abstracts International|g65-01B 
856 40 |u