First-principles calculation of interface properties in diamond (100) and (111) faces/copper composite materials

ObjectivesWith the rapid development of microelectronics technology, the high power density and high integration of electronic devices have led to increasingly prominent heat dissipation problems, and it is necessary to develop composite materials with high thermal conductivity. Diamond/copper composite materials have become a research hotspot due to their excellent thermal conductivity, but the poor interfacial affinity between diamond and copper limits their performance. The aim of this study is to systematically analyze the properties of the interfaces between diamond (100) and (111) crystal faces/copper composite materials using first principles calculations, and to explore the improvement mechanism of titanium coating on the interface properties, providing a theoretical basis for optimizing composite material design.MethodsUsing the first-principle calculation method based on density functional theory (DFT), the CASTEP module of Materials Studio software is used to construct 4 interface models of diamond (100) and (111) crystal faces with copper and titanium (111) faces, respectively. Through structural optimization, energy calculation, electron state density analysis, Mallikan population analysis, and phonon density of states calculation, the binding energy, electronic structure, and heat conduction characteristics of the interfaces are studied. The calculation parameters include a truncation energy of 500 eV, a k-point grid of 14×14×2, and a vacuum layer of 15 Å to ensure calculation accuracy. At the same time, the interface adhesion work is determined by the universal binding energy relation (UBER), and the phonon thermal resistance is quantitatively analyzed by the atomic Green's function (AGF) method.ResultsThe diamond (100) interface has a stronger binding force, and the binding force of diamond (100)/titanium is significantly higher than that of diamond (100)/copper. The adhesion energy of the diamond (100)/titanium interface is 7.875 J/m2, which is approximately 88% higher than that of the diamond (100)/copper interface and 216% higher than that of the diamond (111)/copper interface. By analyzing the electronic state density and Marckensheimer occupation number of the 4 different interfaces, it is found that the diamond (100) interface exhibits a higher density of p-orbital electronic states near the Fermi level and stronger bonding, which are beneficial for electron conduction and chemical reactions. The electron distribution on the (111) crystal surface is more uniform, and the chemical stability is higher than that on the diamond (100) surface. At the same time, the charge change between the first-layer titanium atoms and the carbon atoms at the diamond (100) interface is more significant, while the charge redistribution at the diamond (111) interface is more uniform, and the interfacial stress is lower, which is conducive to the formation of uniform and stable bonds. In addition, the phonon spectrum matching of diamond (100)/copper and diamond (100)/titanium is better, and the interfacial thermal resistance is lower. The phonon spectra of diamond (111)/titanium and diamond (111)/copper overlap less, resulting in higher thermal resistance.ConclusionsOverall, the interface structure between diamond and titanium is superior to that between diamond and copper in terms of interfacial bonding performance, stability, and phonon coupling. The diamond/copper composite material prepared with a titanium coating shows better performance on the diamond (100) surface than on the diamond (111) surface. Therefore, when designing diamond/copper composite materials for thermal conductivity applications, adding a titanium coatings and selecting the diamond (100) crystal face are better choices.