Due to its unique properties,graphene is a promising two-dimensional material in optoelectronic and energy applications.While the mobility of single layer graphene is extremely high,it has a zero bandgap.This feature restricts various applications of graphene in the field of semiconductor devices.Bilayer graphene,despite the nature of zero bandgap in its pristine form,can be tuned to open bandgap via a dual-gated vertical electrical field in a controlled manner.However,the size and layer number of mechanically exfoliated and liquid phase exfoliated graphene are poorly controlled.Controllable synthesis of large-sized bilayer graphene is an important research direction.This review summarizes a series of work including the controlled synthesis of bilayer graphene by chemical vapor deposition method and bilayer graphene devices.Specifically,growth mechanism of bilayer graphene is dependent on the type of supporting substrate and experimental condition.In the case of Ni substrate,bilayer graphene is grown along the segregation route.On the other hand,graphene growth on Cu is a surface-mediated process due to the extremely low solubility of C in Cu bulk.Depending on the concentration ratio between CH4 and H2,the growth mode of bilayer graphene can be tuned to be similar to Volmer-Weber or Stranski-Krastanov mode,in which the second layer is either grown under or above the first graphene layer.The dynamic growth of bilayer graphene can be further understood by a "chemical gate" effect and the process in a confined space.Moreover,here in this paper we present several approaches to realize the better control of bilayer graphene growth by modulating the experimental conditions.In terms of device applications for bilayer graphene,in this review we mention two typical applications including field-effect-transistors and hot-electron bolometers.Compared with conventional silicon-based hot-electron bolometer,the bilayer graphene based hot-electron bolometer has a small heat capacity and weak electron-phonon coupling,leading to high sensitivity,fast response,and small thermal noise-equivalent power.Such a bilayer graphene bolometer shows an exceptionally low noise-equivalent power and intrinsic speed three to five orders of magnitude higher than commercial silicon bolometers and superconducting transition-edge sensors at similar temperatures.Finally,the outlook and challenge for future research are also given.While significant progress has been made in the past several years,the controlled growth of bilayer or multi-layer graphene is still a key challenge,and the growth mechanism of bilayer graphene is not yet understood clearly.There is still much room for controlling graphene layer numbers,twisted angles,size,quality,and yield by optimizing the conditions.On the other hand,for the device applications of bilayer graphene,it is highly desired to develop high-performance bilayer graphene-based electronic devices.%石墨烯是一种具有优异性质,在光电及能源领域具有巨大应用前景的二维材料.尽管单层石墨烯具有超高的迁移率,但是它的能带结构具有狄拉克锥(K点),即价带和导带并未有明显分离,所以在半导体器件方面的应用受到一定的限制.由双层石墨烯搭建而成的双门器件,在施加外加电场的情况下,它的带隙可以打开,并在一定范围内可调,这种性质赋予了双层石墨烯在半导体器件应用方面的前景.然而机械或者液相剥离石墨烯,在层数和大小方面可控性较差.如何通过化学气相沉积法可控制备双层石墨烯是目前研究的核心问题之一.本文主要综述了如何通过化学气相沉积法制备双层石墨烯和制备双层石墨烯器件的一系列工作,其中包括最新的研究进展,对生长机理的研究做了详细的介绍和讨论,并对该领域的发展进行了展望.
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