K. Ait Aissa

Thermal properties of carbon nanowall layers measured by a pulsed photothermal technique

We report the thermal properties of carbon nanowall layers produced by expanding beam radio-frequency plasma. The thermal properties of carbon nanowalls, grown at 600 °C on aluminium nitride thin-film sputtered on fused silica, were measured with a pulsed photo-thermal technique. The apparent thermal conductivity of the carbon at room temperature was found to increase from 20 to 80 Wm−1 K−1 while the thickness varied from 700 to 4300 nm, respectively. The intrinsic thermal conductivity of the carbon nanowalls attained 300 Wm−1 K−1 while the boundary thermal resistance with the aluminium nitride was 3.6 × 10−8 Km2 W−1. These results identify carbon nanowalls as promising material for thermal management applications.

Achieving high thermal conductivity from AlN films deposited by high-power impulse magnetron sputtering

We report on thermal conductivity measurements of aluminum nitride (AlN) films using the fast pulsed photo-thermal technique. The films were deposited by high-power impulse magnetron sputtering with different thicknesses ranging from 1000 to 8000 nm on (1 0 0) oriented silicon substrates. The films were characterized by x-ray diffraction (XRD), Raman spectroscopy, profilometry, scanning electron microscopy and atomic force microscopy. The XRD measurements showed that AlN films were textured along the (0 0 2) direction. Moreover, x-ray rocking curve measurements indicated that the crystalline quality of AlN was improved with the increase in film thickness. The thermal conductivities of the samples were found to rapidly increase when the film thickness increased up to 3300 nm and then showed a tendency to remain constant. A thermal boundary resistance as low as 8 × 10−9 W−1 K m2 and a thermal conductivity as high as 250 ± 50 W K−1 m−1 were obtained for the AlN films, at room temperature. This high thermal conductivity value is close to that of an AlN single crystal and highlights the potential of these films as a dielectric material for thermal management.

Thermal conductivity measurement of AlN films by fast photothermal method

Aluminum nitride (AlN) films were deposited by reactive direct current Magnetron Sputtering (dcMS) on Si (100) substrates, with different thicknesses, in Ar-N2 gas mixture. The films were characterized by X-ray diffraction (XRD), profilometry, scanning electron microscopy and UV-Visible Ellipsometry. The effect of the thickness on the thermal conductivity of AlN films was investigated using a fast IR pyrometry device. The XRD measurements show that AlN films are texturated along (002) direction. Moreover, X-ray rocking curve measurements indicate that the crystalline quality of the AlN is improved with the increase of film thickness. Optical analyses by IR spectroscopy and UV-Visible Ellipsometry demonstrate a high optical band gap of pure AlN films with semi-transparent behaviour in the IR range (1 to 7 μm). The effective thermal conductivity of the AlN films is strongly dependent on the film thickness. An effective thermal conductivities between (80 ± 05) and (175 ± 15) W.m−1.K−1 were measured for 260 and 8000 nm thick AlN film.