金属催化非晶碳转变石墨烯的晶化调控及生长机理研究

发布时间：2018-08-11 11:00

【摘要】：石墨烯因其高电子迁移率、室温量子霍尔效应、高导热率、高强韧等优异性能,在传感器、储能、半导体材料等领域应用前景广阔。然而,石墨烯的产业化受限于制备方法。金属催化非晶碳转变石墨烯作为一种新的石墨烯制备方法,具有高质量、大面积、层数精确可控的优点,目前国内外相关研究刚刚起步,工艺尚不成熟,生长机理尚不明确。为了探索这种新制备方法,本文构筑基体(Si)/非晶碳(a-C)/催化金属(Cu/Ni)三层结构,其中,采用磁过滤阴极真空电弧复合磁控溅射设备制备了a-C膜和Cu膜,电子束蒸镀设备制备了Ni膜,经快速热处理方法在金属催化剂表面制备石墨烯,结合Raman、XPS、TEM、SEM、XRD等检测手段,重点研究了a-C种类及厚度、金属催化剂种类及厚度、退火温度、退火气氛、退火时间对a-C转变石墨烯过程的影响,并初步探讨了其生长机理。本文前期通过Raman和SEM检测结果,快速优化出四面体非晶碳(ta-C)/Ni体系。研究结果表明,Si/ta-C/Ni体系在高温(750°C~1000°C)退火时,退火气氛显著影响生成石墨烯的质量。Ar气氛下Ni易发生熟化形成颗粒状团簇,非晶碳出现石墨化,但未形成石墨烯。真空条件下,生成多层石墨烯,且缺陷多。改变温度和ta-C/Ni厚度比,得出Si/ta-C10nm/Ni100nm退火900°C,保温5min时,制备的石墨烯质量最佳。高温生长过程遵循溶解-析出机理。低温(200°C~600°C)退火时,退火气氛及温度显著影响生成石墨烯的质量。不同气氛下,Ni薄膜表面均连续完整,有助于石墨烯的大面积生长。Ar条件下,非晶碳出现石墨化,但未形成石墨烯。真空条件下,退火400°C时开始生成石墨烯,其中Si/taC40nm/Ni100nm退火500°C,保温15min制备的石墨烯质量最佳,但层数约35层且缺陷多。究其原因,一方面由于金属催化剂Ni的多晶性为石墨烯提供过多形核位点,促使沿Ni晶界和缺陷处扩散至表面的碳过多;另一方面由于ta-C/Ni复合结构中的碳膜厚度大,提供了富余的扩散碳量,导致石墨烯层数多且质量下降。低温时C在Ni中的固溶度降低,碳的扩散行为占主导地位,因此生长机理由溶解-析出和金属诱导协同作用决定。此研究为低温、大面积、可控制备石墨烯提供了一种新思路。
[Abstract]:Because of its high electron mobility, room temperature quantum Hall effect, high thermal conductivity, high strength and toughness, graphene has a wide application prospect in sensor, energy storage, semiconductor materials and other fields. However, the industrialization of graphene is limited by the preparation method. As a new preparation method of graphene, metal-catalyzed amorphous carbon transition graphene has the advantages of high quality, large area and accurate control of layers. At present, the related research at home and abroad is just beginning, the technology is not mature, and the growth mechanism is not clear. In order to explore this new preparation method, a three-layer structure of (Si) / amorphous carbon (a-C) / catalytic metal (Cu/Ni) was constructed, in which a-C film and Cu film were prepared by magnetic filter cathode vacuum arc composite magnetron sputtering equipment, and Ni film was prepared by electron beam evaporation equipment. Graphene was prepared on the surface of the metal catalyst by rapid heat treatment. The type and thickness of a-C, the type and thickness of metal catalyst, the annealing temperature, the annealing atmosphere and so on were studied by means of Ramande XPSX TEMSEMU XRD and so on. The effect of annealing time on the process of a-C transition of graphene was investigated and the growth mechanism of a-C was discussed. The tetrahedral amorphous carbon (ta-C) / Ni system was rapidly optimized by Raman and SEM. The results show that the annealing temperature (750 掳C ~ 1 000 掳C) of Si-Si / ta-C- / Ni system has a significant effect on the formation of graphene in the atmosphere of Ni. Ar atmosphere, Ni is easy to mature to form granular clusters, amorphous carbon appears graphitization, but no graphene is formed. Under vacuum condition, multilayer graphene is formed, and there are many defects. By changing the ratio of temperature to thickness of ta-C/Ni, the best quality of graphene was obtained when Si/ta-C10nm/Ni100nm was annealed at 900 掳C and kept in 5min. The high temperature growth process follows the dissolution-precipitation mechanism. When annealed at low temperature (200 掳C) (600 掳C), the annealing atmosphere and temperature have a significant effect on the quality of graphene. The surface of Ni thin film is continuous and complete in different atmosphere, which is helpful to the graphitization of amorphous carbon under the condition of large area growth of graphene, but no graphene is formed. In vacuum condition, graphene was formed after annealing at 400 掳C, in which Si/taC40nm/Ni100nm annealed at 500 掳C, the quality of graphene prepared by 15min was the best, but the number of layers was about 35 layers and the defects were many. The reason is that, on the one hand, the polycrystalline nature of the metal catalyst Ni provides many nucleation sites for graphene, which promotes the diffusion of carbon to the surface along the grain boundaries and defects of Ni; on the other hand, the thickness of carbon film in the composite structure of ta-C/Ni is large. A surplus amount of diffused carbon is provided, which leads to a large number of graphene layers and a decrease in mass. At low temperature, the solubility of C in Ni decreases, and the diffusion behavior of carbon dominates. Therefore, the reason of solution-precipitation and metal-induced synergism is determined by the growth mechanism. This study provides a new idea for the preparation of graphene at low temperature, large area and controllable preparation.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11

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