Substrate temperature measured by a film-on-plate thermocouple during diamond growth using the combustion flame technique

Abstract

Substrate temperature was monitored during combustion flame-assisted diamond growth. A platinum-coated copper plate was fabricated as not only the substrate for diamond growth but also the thermocouple to measure the substrate temperature. The Pt-Cu thermocouple demonstrated stable thermoelectric characteristics in a high-temperature argon atmosphere. The thermal electromotive force reached 15.9–16.0 mV at the initial heating to 970 °C. This was independent of the Pt film thickness. In addition, the thermoelectric characteristic of a 2 μm-thick sample was unchanged after second and third heatings. Diamond was deposited on the Pt-Cu thermocouple, having > 2 μm in Pt thickness, by a combustion flame technique using an oxyacetylene torch. A linear least-squares fit inserted in the relation between the substrate temperature and the growth rate suggests that the apparent activation energy for this experiment is 23 kcal mol−1.