FEATURES OF HEAT TRANSFER IN CARBON DIAMOND-LIKE THIN FILMS

10.25712/ASTU.1811-1416.2025.04.005

Abstract

Abstract
It is believed that the thermal conductivity of non-metallic materials, including diamonds, is carried out mainly by phonons. However, the situation is more complicated in carbon diamond-like films. It would seem that in single-phase diamond films the phonon mechanism of thermal conductivity is obvious. However, the multiplicity of interfaces and the presence of a high concentration of hydrogen reduce the thermal conductivity coefficient to 0.2 - 3.0 W / (mK) in diamond films, that is, by three to four orders of magnitude compared to the thermal conductivity of a diamond single crystal. Only in micron diamond films does the thermal conductivity coefficient approach the thermal conductivity of a diamond single crystal. The complexity of substantiating the mechanism of thermal conductivity in carbon thin (nanometer) films lies in the features of the structure, which is actually a thin-film composite of diamond-like and graphite-like clusters, the size of which is 0.5 - 1.0 nm. Thus, such a composite is a set of regions with different mechanisms of thermal conductivity - in diamond-like clusters, the phonon mechanism operates, in graphite-like clusters, the electronic mechanism of heat transfer prevails. That is, at the interface, a change in heat transfer from phonon to electronic is observed. However, in carbon diamond-like films, there are no interfaces, diamond-like and graphite-like clusters are linked by sp3- and sp2-bonds, which is accompanied by the appearance of localized electronic states in the forbidden zone of the diamond-like cluster until it is completely filled. In fact, the diamond-like cluster becomes an electrically conductive cluster. This effect significantly complicates the mechanism of thermal conductivity.