Department of Physics, Indian Institute of Science, Bangalore 560 012, India.
ACS Nano. 2011 Oct 25;5(10):7707-12. doi: 10.1021/nn202852j. Epub 2011 Sep 19.
We present low-temperature electrical transport experiments in five field-effect transistor devices consisting of monolayer, bilayer, and trilayer MoS(2) films, mechanically exfoliated onto Si/SiO(2) substrate. Our experiments reveal that the electronic states in all films are localized well up to room temperature over the experimentally accessible range of gate voltage. This manifests in two-dimensional (2D) variable range hopping (VRH) at high temperatures, while below ∼30 K, the conductivity displays oscillatory structures in gate voltage arising from resonant tunneling at the localized sites. From the correlation energy (T(0)) of VRH and gate voltage dependence of conductivity, we suggest that Coulomb potential from trapped charges in the substrate is the dominant source of disorder in MoS(2) field-effect devices, which leads to carrier localization, as well.
我们呈现了五个由单层、双层和三层 MoS(2) 薄膜组成的场效应晶体管器件的低温输运实验，这些薄膜是通过机械剥离在 Si/SiO(2) 衬底上形成的。我们的实验表明，在实验可访问的栅极电压范围内，所有薄膜中的电子状态在室温下都很好地被局域化。这表现在高温下的二维（2D）变程跳跃（VRH），而在约 30 K 以下，电导率在栅极电压中显示出由局域化点的共振隧穿引起的振荡结构。从 VRH 的关联能量（T(0)）和电导率对栅极电压的依赖性，我们提出，来自衬底中被俘获电荷的库仑势是 MoS(2) 场效应器件中无序的主要来源，这也导致了载流子的局域化。
