Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Nanotechnology. 2012 Oct 5;23(39):395203. doi: 10.1088/0957-4484/23/39/395203. Epub 2012 Sep 12.
In this paper we investigate the influence of material and device properties on the ballistic transport in epitaxial monolayer graphene and epitaxial quasi-free-standing monolayer graphene. Our studies comprise (a) magneto-transport in two-dimensional (2D) Hall bars, (b) temperature- and magnetic-field-dependent bend resistance of unaligned and step-edge-aligned orthogonal cross junctions, and (c) the influence of the lead width of the cross junctions on ballistic transport. We found that ballistic transport is highly sensitive to scattering at the step edges of the silicon carbide substrate. A suppression of the ballistic transport is observed if the lead width of the cross junction is reduced from 50 nm to 30 nm. In a 50 nm wide device prepared on quasi-free-standing graphene we observe a gradual transition from the ballistic into the diffusive transport regime if the temperature is increased from 4.2 to about 50 K, although 2D Hall bars show a temperature-independent mobility. Thus, in 1D devices additional temperature-dependent scattering mechanisms play a pivotal role.
本文研究了材料和器件性质对外延单层石墨烯和外延准自由-standing 单层石墨烯中弹道输运的影响。我们的研究包括：（a）二维（2D）霍尔条中的磁输运，（b）未对准和台阶边缘对准的正交十字结的温度和磁场相关弯曲电阻，以及（c）十字结引线宽度对弹道输运的影响。我们发现，弹道输运对碳化硅衬底台阶边缘的散射非常敏感。如果将十字结的引线宽度从 50nm 减小到 30nm，弹道输运将受到抑制。在准自由-standing 石墨烯上制备的 50nm 宽器件中，尽管 2D 霍尔条表现出与温度无关的迁移率，但如果温度从 4.2 升高到约 50K，我们观察到从弹道输运到扩散输运的逐渐转变。因此，在 1D 器件中，额外的温度相关散射机制起着关键作用。
