Preparation And Thermal Conductivity Research Of Hexagonal Boron Nitride-graphene Composites

Excess heat in electronic devices will retard the running speed of the process inside, and even destroy or burn the whole devices. To improve reliability and prevent premature failure of most electronic products, heat generated during the use of these electronic devices must be removed as quickly as possible. Hence, heat dissipation is one of most critical challenges in current high-density and high-power electronic products. To realize efficient heat dissipation, it requires that the thermal conductivity(TC) of the semiconductor materials or the outside packing films is high. However, the thermal conductivity of typical materials is far below the requirements for efficient heat dissipation. Thermal conductivities of conventional metals, ceramics are not high enough, which drives us to find new materials with high thermal conductivity.Graphene as a 2D hexagonal honeycomb structure material occupied by sp2 carbon atoms has many outstanding mechanical, thermal and electronic properties because of its unique planar structure,it is the first of the two-dimensional materials that is found to exist independently in the world. The suspending single-layer graphene have a super-high in-plane thermal conductivity of around 5300 W/(m.K) at room temperature,and the TC of graphene changes from ~2800 W/(m.K) to ~1300 W/(m.K) when the layer number of graphene increases from 2 to 4 due to the cross-plane coupling of the low-energy phonons and changes in the phonon Umklapp scattering. Boron nitride(BN) is a well-known non-oxide ceramics, the single-layer hexagonal boron nitride(h-BN) shares a similar honeycomb lattice structure with graphene and its structure has been confirmed in experiments. Especially, its high thermal conductivity has garnered widespread attention. The excellent thermal properties of h-BN has been reported and a high thermal conductivity up to 600 W/(m.K) at room temperatures has been measured. It can be a very promising high-performance thermal management material. Therefore, our mainly focuses on the characteristics of high thermal conductivity of graphene and boron nitride, and the thermal conductivity of the material was tested on different substrates. The research contents and results are as follows:1、we first prepare graphene and h-BN films on Si substrate through chemical vapor deposition(CVD) and radio frequency(RF) magnetron sputtering methods, respectively. Then we characterize the structures and morphologies of graphene and h-BN films on Si substrate though the AFM、SEM、FTIR and Raman spectroscopy. These results show that the condition of gas pressure is set 0.8Pa, and when the sputtering power is 120 W and the argon nitrogen ratio is 40:10, boron nitride thin film surface roughness is smaller, better crystalline performance, film growth is the best; And the surface of graphene grown on boron nitride is more smooth than that of graphene grown directly on the substrate, lower surface roughness, uniform grain distribution, good crystalline properties, and the growth of graphene was multilayer structure that observed through the cross section of SEM, such thin film growth characteristics contribute to the study of the thermal conductivity of materials.2、At the gas pressure of 0.8Pa, the sputtering power is 120 W, and the argon nitrogen ratio is 40:10,growing the h-BN thin films through the RF magnetron sputtering methods, detection by EDS that B and N atomic ratio close to 1:1, does not appeared the situation that lack of nitrogen, reduce the generation of impurities; And then the films were grown on Al N 、Al2O3、Zr O2, and characterized by AFM、SEM、FTIR and Raman spectroscopy. Determination of thermal conductivity by using LFA467 laser thermal conductivity meter. The results showed that the TEF of the h-BN film is 1.56% with silicon as the substrate and the graphene TEF is 3%; The TEF of graphene films grown on Al N substrate is 11.3%; The TEF of h-BN films grown on Zr O2 substrate is 11.3%, The growth of graphene TEF is 6.7%, and the TEF of the h-BN / graphene films is 6.7%. The films prepared by this way can improve the thermal conductivity of the whole material, it provides an effective basis for the study of the thermal conductivity of materials in the future.