Control of the in-plane thermal conductivity of ultra-thin nanocrystalline diamond films through the grain and grain boundary properties

Abstract

The in-plane thermal conductivity of polycrystalline diamond near its nucleation site, which is a key parameter to an efficient integration of diamond in modern high power AlGaN/GaN high electron mobility devices, has been studied. By controlling the lateral grain size evolution through the diamond growth conditions it has been possible to increase the in-plane thermal conductivity of the polycrystalline diamond film for a given thickness. Besides, the in-plane thermal conductivity has been found strongly inhomogeneous across the diamond films, being also possible to control this inhomogeneity by the growth conditions. The experimental results has been explained through a combined effect of the phonon mean free path confinement due the grain size and the quality of the grain/grain interfaces, showing that both effects evolve with the grain expansion and are dependant on the diamond growth conditions. This analysis shows how the thermal transport in the near nucleation region of polycrystalline diamond can be controlled, which ultimately opens the door to create ultra-thin layers with a engineered thermal conductivity, ranging from a few W/mK to a few hundreds of W/mK.

A Review of Raman Thermography for Electronic and Opto-Electronic Device Measurement With Submicron Spatial and Nanosecond Temporal Resolution

“…It is possible to determine material thermal properties by performing Raman thermography measurements on simple resistor test structures, such as metal line heaters or ring heaters deposited on top of the material of interest, or by monitoring temperature changes as function of laser power. This has been demonstrated for measuring the thermal conductivity of diamond [45], graphene [78] and other materials.…”

“…Therefore, this technique is limited to measuring device areas where optical access is not blocked by metal contacts, either in openings between contacts or alternatively measurements can be performed by focusing the laser through the substrate backside, as discussed above, since the measurement can be performed using a sub bandgap laser, in contrast to PL spectroscopy. Although metal surfaces cannot be measured directly using Raman thermography, the application of Raman active micro-thermometers can be used to sense the temperature of these surfaces, including, but not limited to, diamond nanoparticles, TiO 2 nanoparticles or silicon nanowires [44,45].…”

Electrolytic Treatment Characteristics of Boron-doped Nanocrystalline Diamond/Amorphous Carbon Composite Films Prepared by Coaxial Arc Plasma Deposition

“…Nanocrystalline diamond/hydrogenated amorphous carbon composite (NCD/a-C:H) films and NCD/nonhydrogenated amorphous carbon composite (NCD/a-C) films comprising diamond crystallites in matrices of a-C:H and a-C have attracted attention because of their unique characteristics, which include a low coefficient of friction, high thermal stability, and large optical absorption coefficient (10)(11)(12)(13) . Diamond crystallites with diameters less than 10 nm are called ultrananocrystalline diamond (UNCD).…”

“…The superior mechanical, physical, and chemical characteristics of these films are assumed to be a consequence of NCDs and UNCDs in an a-C or a-C:H matrix existing as diamond crystallites. Such films are fabricated by CVD (10,(12)(13)(14) . By contrast, reports of the fabrication of such films by physical vapor deposition (PVD) methods are scarce.…”

Enhanced Diamond Nucleation on Cemented Carbide Cutting Tools by Employing Electrostatic Self-Assembly Seeding

“…Its hardness in combination with other outstanding properties such as high stiffness, high wear resistance, high thermal conductivity, semi-conductivity, and chemical inertness, makes diamond an excellent material for a variety ofapplications, such as protective coatings, heat spreader, optical windows and biological platforms, and so forth. [1][2][3][4] Research activities on nanocrysatlline diamond thin films have increased rapidly. [5,6] For the application in high performance Micro and Nano Electro-Mechanical System, carbide tools in micro size with sharp cutting edge are highly needed.…”