Accession Number : AD0666073

Title :   INVESTIGATION OF EVAPORATION AND CONDENSATION MECHANISM.

Descriptive Note : Final rept. 15 May 66-31 Aug 67,

Corporate Author : TYCO LABS INC WALTHAM MASS

Personal Author(s) : Cocks,F. H. ; Das,B. N. ; Lamport,C. B. ; Menna,A. A. ; Trickett,E. A.

Report Date : DEC 1967

Pagination or Media Count : 149

Abstract : For most materials the condensation coefficient alpha is available and provides a fair estimate of the rate of evaporation and vapor-phase growth of thin films or bulk crystals. However, little information exists on the detailed kinetics of the evaporation or condensation itself. Also, little attention has been paid to the fact that alpha may assume different values for different planes of the same crystal. Instead of attempting to obtain and interpret the mean value of alpha, a new approach is followed here which utilizes the changes in the growth or solution rates of specific crystal planes as a function of varying growth or evaporation conditions. Since a given crystal plane is made up of easily identifiable atomic surface sites (representing the kinetically rate-determining participants in the atomic process taking place on this plane), the type of observed crystal morphology then serves to identify these processes. The evaporation and growth (both directly from the vapor and by chemical decomposition) of ZnO has been selected for study as a model process. Guidelines for the evaluation of experimental morphology data and the derivation of theoretical crystal morphology are described. It was found that habits of various crystal structures can be expressed by a structure factor type formula. (Author)

Descriptors :   (*EPITAXIAL GROWTH, *ZINC COMPOUNDS), OXIDES, EVAPORATION, CONDENSATION, FILMS, SINGLE CRYSTALS, PHASE STUDIES, SURFACES, ETCHED CRYSTALS, TEMPERATURE, NUMERICAL METHODS AND PROCEDURES, SOLVENT EXTRACTION, LASERS, POLARIZATION, TEST METHODS

Subject Categories : Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE