Influence of the microstructure on the thermal properties of thin polycrystalline diamond films

Highly oriented and columnar grained diamond layers only a few microns thick, deposited at different substrate temperatures (500, 550, and 800 degrees C) on silicon using microwave-plasma-assisted chemical vapor deposition, are investigated by special photothermal techniques and high-resolution transmission electron microscopy (HRTEM). Small effective diamond-silicon boundary resistances of <4x10(-9) m(2)K/W are determined for thermal conduction normal to the interface. Thermal conductivities normal to the interface, k(p)erpendicular to, are found to be about an order of magnitude greater than the conductivities parallel to the interface, k(parallel to) (k(perpendicular to)/k(parallel to)=9-18). The boundary resistances measured are in good agreement with limits estimated from the interface structure observed by HRTEM, which indicate a low near-interfacial disorder for the layers. (C) 1997 American Institute of Physics.