Thermal analysis of submicron nanocrystalline diamond films

• A strategy to analyze NCD anisotropic thermal properties by SThM is proposed.
• We examine thermal conductivity variations with thickness in columnar NCD films.
• High thermal conductivities may be reached already in the submicron range.
• The columnar structure enhances vertical transport compared to the lateral.

The thermal properties of sub-μm nanocrystalline diamond films in the range of 0.37–1.1 μm grown by hot filament CVD, initiated by bias enhanced nucleation on a nm-thin Si-nucleation layer on various substrates, have been characterized by scanning thermal microscopy. After coalescence, the films have been outgrown with a columnar grain structure. The results indicate that even in the sub-μm range, the average thermal conductivity of these NCD films approaches 400 W m− 1 K− 1. By patterning the films into membranes and step-like mesas, the lateral component and the vertical component of the thermal conductivity, klateral and kvertical, have been isolated showing an anisotropy between vertical conduction along the columns, with kvertical ≈ 1000 W m− 1 K− 1, and a weaker lateral conduction across the columns, with klateral ≈ 300 W m− 1 K− 1.