光敏聚合物和UV光对外延石墨烯的封装及电子控制
Encapsulation and Electronic Control of Epitaxial Graphene by Photosensitive Polymers and UV light
摘要：
在碳化硅上使用外延石墨烯的电子器件需要封装，以避免在环境条件下沉积的杂质的不受控制的掺杂。另外，石墨烯单层与衬底的相互作用导致该材料中相对高水平的电子掺杂，这相当难以单独通过静电门控来改变。在这里，我们描述了这些问题的一种解决方案，允许在宽范围内封装和控制载流子浓度。我们描述了一种新的异质结构的基础上生长的外延石墨烯碳化硅结合两种聚合物：中性间隔和光敏层，提供了有效的电子受体在紫外光照射下。在未曝光的情况下，相同的双层聚合物很好地用作覆盖材料，提高了样品掺杂水平的时间稳定性和均匀性。通过对这种异质结构进行紫外曝光，我们以非侵入性、非挥发性和可逆的方式控制了石墨烯的电参数，将载流子浓度改变了50倍。暴露的SiC/石墨烯/聚合物异质结构的电子性质在室温下保持稳定许多天，但将聚合物加热到玻璃化转变温度以上会逆转光的作用。新开发的光化学选通已经帮助我们将石墨烯电阻标准的鲁棒性（大范围的量化磁场、显著更高的操作温度和由于显著增加的击穿电流而显著增强的信噪比）提高到这样的水平，使得其开始有利地与成熟的半导体异质结构标准竞争。[2，3]
英文摘要：
Electronic devices using epitaxial graphene on Silicon Carbide require encapsulation to avoid uncontrolled doping by impurities deposited in ambient conditions. Additionally, interaction of the graphene monolayer with the substrate causes relatively high level of electron doping in this material, which is rather difficult to change by electrostatic gating alone. Here we describe one solution to these problems, allowing both encapsulation and control of the carrier concentration in a wide range. We describe a novel heterostructure based on epitaxial graphene grown on silicon carbide combined with two polymers: a neutral spacer and a photoactive layer that provides potent electron acceptors under UV light exposure. Unexposed, the same double layer of polymers works well as capping material, improving the temporal stability and uniformity of the doping level of the sample. By UV exposure of this heterostructure we controlled electrical parameters of graphene in a non-invasive, non-volatile, and reversible way, changing the carrier concentration by a factor of 50. The electronic properties of the exposed SiC/ graphene/polymer heterostructures remained stable over many days at room temperature, but heating the polymers above the glass transition reversed the effect of light. The newly developed photochemical gating has already helped us to improve the robustness (large range of quantizing magnetic field, substantially higher opera- tion temperature and significantly enhanced signal-to-noise ratio due to significantly increased breakdown current) of a graphene resistance standard to such a level that it starts to compete favorably with mature semiconductor heterostructure standards. [2,3]
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