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Effect of high temperature annealing on optical and thermal properties of CVD diamond
Ist Teil von
Diamond and related materials, 2001-03, Vol.10 (3), p.546-551
Ort / Verlag
Elsevier B.V
Erscheinungsjahr
2001
Link zum Volltext
Quelle
Access via ScienceDirect (Elsevier)
Beschreibungen/Notizen
Structural changes in diamond films of different qualities caused by annealing in vacuum up to 1600°C have been studied by IR and UV-visible optical absorption, Raman and photoluminescence spectroscopy. An internal degradation of the diamond films and a strong optical absorption enhancement in the whole UV-vis-IR range take place at
T>1300°C, and correlate with the loss of bonded hydrogen. At least 25% of the total amount of hydrogen is found to be in the unbound state in some of the as-grown (untreated) films. The diamond darkening is ascribed to appearance of graphite-like phases presumably at grain boundaries. Activation energy of GB transformation process is much lower (250–530 kJ/mol) compared to surface graphitization of single crystal diamond. No evidence of charge transfer altering the concentration of substitutional nitrogen N
0
S and N
A−N
D (in B-doped films) upon annealing was found. Thermal conductivity measured by laser flash technique remains almost constant (20 W/cmK) even after annealing to 1575°C, then catastrophically drops because of crack development in the film.