Photothermal examination of the heat diffusion inhomogeneity in diamond films of sub-micron thickness

Thermal conductivity of ultrathin nano-crystalline diamond films determined by Raman thermography assisted by silicon nanowires

“…These figures are in good agreement with those reported in Ref. 20 for similar c-NCD thin layers, for which, however, no cross-plane thermal conductivity values were reported. Given that the two samples were grown under the same conditions, the only difference between the two samples lies in their average lateral grain size; the grains of the thicker samples when measured from the top surface are a $25% larger than the ones for the thinner sample (160 nm vs 130 nm).…”

“…14 To determine the thermal characteristics in the near nucleation region, measuring the j of ultra-thin layers of columnar nano-crystalline diamond (c-NCD) is needed; however, this is a challenging task, which is mostly performed with transient measurements. [20][21][22][23][24][25] Nevertheless, these transient techniques are indirect methods having access only to the thermal diffusivity, which requires a complex data analysis for extracting the thermal conductivity. As a result, in-plane thermal conductivities ranging from 20 W/ mK (Refs.…”

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

“…A few inconsistent results are available in the literature about the in-plane thermal transport in the first microns of polycrystalline diamond showing values ranging from a few W/mK up to 800 W/mK for layers thicknesses below 2 µm. [13,14,15,16,17,18,19,20,21,22,23, 24] Also 25 a strong inhomogeneity of the in-plane thermal conductivity through the diamond films has been reported, [11,12,21,22,24] although mostly for films larger 2 than a few micrometer thickness, due to challenges in measuring the thermal properties of very thin diamond films. Therefore a clear description of the heat transport in the complex near nucleation region of polycrystalline diamond is 30 still lacking.…”

“…However, while the thermal conductivity of polycrystalline diamond may reach values close to that of the single crystal diamond, [11] the thermal transport near its near nucleation site may be much lower due the small grain size and the accumulation of defects in this region. [12,13] Two strategies for combining diamond with the devices using the direct growth approach have 15 emerged in the recent years, , namely, either by substituting the SiC or Si substrate, [1,3,4,5] or by growing the diamond films on top of the device passivation layer. [6,7,8,9, 10] However, in both strategies the heat has to diffuse across the nucleation region of the diamond film, and therefore knowing how the heat is spread in the first microns of the polycrystalline diamond is fundamental 20 in order to optimize their thermal resistance and thus improve their lifetime and reduce its energy consumption.…”

“…[70] Also low thermal conductivities due poor lattice quality has been correlated with theCH 4 /H 2 ratio; typically samples grown 310 with more than 1%CH 4 /H 2 show a strong reduction of the thermal conductivity with the CH 4 /H 2 ratio. [13,71,72,73] Since the samples analyzed here are grown with much lowerCH 4 /H 2 ratio than this limit, and their transparency and Raman spectra characteristics, nothing indicates the high point defects needed to impact the thermal conductivity in the grain size range shown by the herein 315 analyzed samples.…”