Electronic transport in heterostructures of chemical vapor deposited graphene and hexagonal boron nitride.
Electronic transport in heterostructures of chemical vapor deposited graphene and hexagonal boron nitride.
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化学气相沉积石墨烯和六方氮化硼异质结构中的电子传输。
DOI：
10.1002/smll.201402543
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Johnson,ATCharlie
中科院分区：
文献类型：
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作者：
Qi,ZhengqingJohn;Hong,SungJu;Rodríguez-Manzo,JulioA;Kybert,NicholasJ;Gudibande,Rajatesh;Drndić,Marija;Park,YungWoo;Johnson,ATCharlie
郑清John Qi， Sung Ju Hong, Julio A. Rodríguez-Manzo, Nicholas J. Kybert, Rajatesh Gudibande, Marija Drndic ', Yung Woo Park, AT Charlie Johnson* 14000 cm 2 V−1 s−1。[20,21]然而，剥离并不是一个可扩展的过程，因此仍然需要引入一个平台，允许在晶圆尺度上进行基板工程。最近，hBN的CVD生长已经得到证实，[22-25]为可扩展的、大面积制造石墨烯-hBN异质结构器件提供了一条途径。在这项工作中，我们提供了一个系统的研究，为hBN集成的实际设计考虑提供信息，并报告了cvd生长的石墨烯-hBN异质结构器件中记录的低场和高场输运。采用了一种新的方法来最大限度地减少石墨烯-hBN堆叠层之间污染物的存在，允许连续的cvd单层hBN片连续堆叠在cvd单层石墨烯下，保持密切接触。二维材料之间的晶体取向也是可控的，允许明确的堆叠方向和材料厚度，超越了以前的方法。[23,24]利用高真空电流退火技术降低了CVD石墨烯ehbn异质结构制造过程中的接触电阻率并蒸发了表面污染物，导致空穴和电子迁移率值超过8,000 cm 2 V−1 s−1，是之前报道的两倍多。[23,24]最后，在石墨烯-hBN异质结构中观察到改善的高温（功耗）和高偏置（击穿电流密度）性能，这归因于与二氧化硅衬底[26]相比，五层hBN的热导率提高了200倍，并且具有更高能量的光学声子模式[19]图1是制造过程的示意图，它是基于单层材料的转移和堆叠，使用单个PMMA抗支架来减少污染，类似于最近的一份报告器件制造开始时，使用PMMA层作为机械支撑，将单层石墨烯从铜生长衬底中分离出来。[28-30]利用鼓泡转移法避免了生长衬底蚀刻过程中引入的金属纳米颗粒污染。[28,31] pmma -石墨烯堆叠随后在多个去离子水浴中清洗，并直接转移到通过CVD在催化铜衬底上生长的单层hBN样品上，目的是防止在石墨烯和hBN之间引入不需要的污染物（例如，抗性残留物）。这一过程一直重复，直到石墨烯被五个hBN层支撑。我们注意到，这种转移过程允许对异质结构厚度进行逐层控制，并且可以通过取向已知的边缘结构（晶体取向）来定义结晶二维材料之间的扭转角。
Zhengqing John Qi, Sung Ju Hong, Julio A. Rodríguez-Manzo, Nicholas J. Kybert, Rajatesh Gudibande, Marija Drndic′, Yung Woo Park, and AT Charlie Johnson*14,000 cm 2 V− 1 s− 1.[20, 21] However, exfoliation is not a scalable process, so there remains a need to introduce a platform that allows for substrate engineering at the wafer-scale. Recently, CVD growth of hBN has been demonstrated,[22–25] providing a route towards scalable, large-area fabrication of graphene-hBN heterostructure devices. In this work, we provide a systematic study to inform practical design considerations for hBN integration and report record low-and high-field transport in CVD-grown graphene-hBN heterostructure devices. A novel methodology was used to minimize the presence of contaminants in between layers of the graphene-hBN stack, allowing for continuous sheets of CVD-grown monolayer hBN to be consecutively stacked beneath CVD-grown monolayer graphene in intimate contact. The crystallographic orientation between the 2D materials is also controllable, allowing for well-defined stacking orientation and material thickness, advancing beyond previous methods.[23, 24] High-vacuum current-annealing was utilized to lower the contact resistivity and vaporize surface contaminants from the fabrication process of CVD graphenehBN heterostructures, resulting in hole and electron mobility values in excess of 8,000 cm 2 V− 1 s− 1, more than twice that of previous reports.[23, 24] Finally, improved high-temperature (power dissipation) and high-bias (breakdown current density) performance were observed in graphene-hBN heterostructures and attributed to the effect of the 200 times greater thermal conductivity of five-layer hBN as compared to a SiO 2 substrate [26] and the higher energy optical phonon modes.[19] Figure 1 is a schematic of the fabrication process, which is based on transferring and stacking of monolayer materials using a single PMMA resist scaffold to minimize contamination, similar to a recent report.[27] Device fabrication began with separating monolayer graphene from its copper growth substrate using a PMMA layer for mechanical support.[28–30] Metal nanoparticle contamination introduced during etching of the growth substrate was avoided by utilizing the bubbling transfer method.[28, 31] The PMMA-graphene stack was subsequently cleaned in multiple deionized water baths and transferred directly onto a sample of monolayer hBN grown by CVD on a catalytic copper substrate, with the goal of preventing the introduction of unwanted contaminants (eg, resist residue) between the graphene and hBN. This process was repeated until the graphene was supported by five hBN layers. We note that this transfer process allows for layer-bylayer control of the heterostructure thickness and could be utilized to define twist angles between crystalline 2D materials by orienting known edge structures (crystallographic orientation)