Department of Physics, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
ACS Nano. 2017 Oct 24;11(10):9914-9919. doi: 10.1021/acsnano.7b03878. Epub 2017 Sep 14.
We measure drift velocity in monolayer graphene encapsulated by hexagonal boron nitride (hBN), probing its dependence on carrier density and temperature. Due to the high mobility (>5 × 10 cm/V/s) of our samples, the drift velocity begins to saturate at low electric fields (∼0.1 V/μm) at room temperature. Comparing results to a canonical drift velocity model, we extract room-temperature electron saturation velocities ranging from 6 × 10 cm/s at a low carrier density of 8 × 10 cm to 2.7 × 10 cm/s at a higher density of 4.4 × 10 cm. Such drift velocities are much higher than those in silicon (∼10 cm/s) and in graphene on SiO, likely due to reduced carrier scattering with surface optical phonons whose energy in hBN (>100 meV) is higher than that in other substrates.
我们测量了被六方氮化硼（hBN）包裹的单层石墨烯的漂移速度，研究了其对载流子密度和温度的依赖关系。由于我们样品的迁移率很高（>5×10^5 cm^2/V/s），在室温下，漂移速度在低电场（约 0.1 V/μm）下开始饱和。将结果与典型的漂移速度模型进行比较，我们提取出室温下电子饱和速度，在低载流子密度 8×10^11 cm^-2 时为 6×10^5 cm/s，在较高密度 4.4×10^11 cm^-2 时为 2.7×10^5 cm/s。这样的漂移速度远高于硅（~10^5 cm/s）和 SiO 上的石墨烯，可能是由于载流子与表面光学声子的散射减少，而 hBN 中的声子能量（>100 meV）高于其他衬底。
