Theoretical study of diamond-like carbons and nucleation of diamond

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7165973

Lee, Choon Heung

Different forms of amorphous carbon and hydrocarbons with varying elastic and optical properties, hardness, density and hydrogen content exist depending on the preparation technique. In order to study the properties of such materials, microscopic models must be developed. These studies include the modelling of crosslinked defective graphite, diamond nucleation along the graphite edges, and diamond-like carbons. Tamor's proposed structure for diamondlike carbon consists of crosslinked graphitic regions. The author studied a concrete realization of this model in which the cross-links are produced by shortening the interplanar bond lengths. The model study used has a semi-empirical potential that contains angular terms. It is enhanced by a long-range potential which describes the interplanar interactions. A significant enhancement of diamond nucleation on the graphite edge planes with the preferential orientation relationship: (0001)[sub g][parallel](111)[sub d], [r angle]1120[l angle][sub g][parallel][r angle]101[l angle][sub d] was observed. Two possible interface structures were studied. The models have comparable low interface energies even if they contain some dangling bonds. Lower interface energies were found when the dangling bonds of the nonbonded diamond layer were satisfied with hydrogen. Models of dense amorphous carbon is constructed. The WWW model was the starting structure. The effects of clustering of the three-fold coordinated atoms in pairs, chains, or graphitic were studied. The resulting models were relaxed and their electronic structures were studied using an empirical tight-binding scheme. Localized dangling bonds and [pi] - [pi][sup *] states were found within the wide gap of the WWW model consistent with optical gaps. Hydrogen atoms were introduced to remove some of the dangling bonds. The models were found to account for the essential features of ion-beam deposited amorphous carbon and hydrogenated amorphous carbon.

• Research Organization: Case Western Reserve Univ., Cleveland, OH (United States)
• OSTI ID: 7165973
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
CARBON
CHEMICAL BONDS
DATA
DIAMONDS
ELEMENTAL MINERALS
ELEMENTS
GRAPHITE
INFORMATION
INTERFACES
INTERMOLECULAR FORCES
MINERALS
NONMETALS
NUCLEATION
NUMERICAL DATA
THEORETICAL DATA