论文标题
AFM裂解光刻绘制的狭窄石墨烯收缩的稳健量子接触操作
Robust quantum point contact operation of narrow graphene constrictions patterned by AFM cleavage lithography
论文作者
论文摘要
在石墨烯纳米结构中检测电导量化的质量比预期的更具挑战性。到目前为止，通过石墨烯纳米收缩对明确定义的电导高原观察只有在最高质量的悬浮或H-BN封装的设备中才能访问。但是，即使使用如此高的移动设备，在零磁场中达到低电导量的量子也是一项微妙的任务。在这里，我们演示了一种简单的基于AFM的纳米图案技术，用于定义高精度（宽度为10 nm）和降低的边缘 - 粗糙度（+/- 1 nm）的石墨烯收缩。图案过程基于AFM尖端的平面机械裂解，沿其高对称的晶体学方向。具有改进的边缘质量的最终定义，狭窄的石墨烯限制可以实现前所未有的QPC操作，即使在标准$ sio_2/si $底物上也可以观察到电导量化，从而降低电导率量子。在没有外部磁场的情况下，在$ ne^2/h $中观察到电导高原，在$ NE^2/h $中，均匀间隔为$ 2E^2/h $（对应于N = 3、5、7、9、11），而间隔为$ e^2/h $（n = 1、2、2、3、4、5、6）。
Detecting conductance quantization in graphene nanostructures turned out more challenging than expected. The observation of well-defined conductance plateaus through graphene nanoconstrictions so far has only been accessible in the highest quality suspended or h-BN encapsulated devices. However, reaching low conductance quanta in zero magnetic field, is a delicate task even with such ultra-high mobility devices. Here, we demonstrate a simple AFM-based nanopatterning technique for defining graphene constrictions with high precision (down to 10 nm width) and reduced edge-roughness (+/- 1 nm). The patterning process is based on the in-plane mechanical cleavage of graphene by the AFM tip, along its high symmetry crystallographic directions. As-defined, narrow graphene constrictions with improved edge quality enable an unprecedentedly robust QPC operation, allowing the observation of conductance quantization even on standard $SiO_2/Si$ substrates, down to low conductance quanta. Conductance plateaus, were observed at $ne^2/h$, evenly spaced by $2e^2/h$ (corresponding to n = 3, 5, 7, 9, 11) in the absence of an external magnetic field, while spaced by $e^2/h$ (n = 1, 2, 3, 4, 5, 6) in 8T magnetic field.
