School of Electrical and Computer Engineering, Cornell University , Ithaca, New York 14853, United States.
Nano Lett. 2014 Aug 13;14(8):4511-6. doi: 10.1021/nl5015316. Epub 2014 Jul 9.
The electrical properties of multilayer MoS2/graphene heterojunction transistors are investigated. Temperature-dependent I-V measurements indicate the concentration of unintentional donors in exfoliated MoS2 to be 3.57 × 10(11) cm(-2), while the ionized donor concentration is determined as 3.61 × 10(10) cm(-2). The temperature-dependent measurements also reveal two dominant donor levels, one at 0.27 eV below the conduction band and another located at 0.05 eV below the conduction band. The I-V characteristics are asymmetric with drain bias voltage and dependent on the junction used for the source or drain contact. I-V characteristics of the device are consistent with a long channel one-dimensional field-effect transistor model with Schottky contact. Utilizing devices, which have both graphene/MoS2 and Ti/MoS2 contacts, the Schottky barrier heights of both interfaces are measured. The charge transport mechanism in both junctions was determined to be either thermionic-field emission or field emission depending on bias voltage and temperature. On the basis of a thermionic field emission model, the barrier height at the graphene/MoS2 interface was determined to be 0.23 eV, while the barrier height at the Ti/MoS2 interface was 0.40 eV. The value of Ti/MoS2 barrier is higher than previously reported values, which did not include the effects of thermionic field emission.
研究了多层 MoS2/石墨烯异质结晶体管的电学性质。温度相关的 I-V 测量表明，剥离的 MoS2 中的非故意施主浓度为 3.57×10(11)cm(-2)，而离化施主浓度则确定为 3.61×10(10)cm(-2)。温度相关的测量还揭示了两个主要的施主能级，一个位于导带以下 0.27 eV，另一个位于导带以下 0.05 eV。I-V 特性随漏极偏压而不对称，并取决于用作源极或漏极接触的结。该器件的 I-V 特性与具有肖特基接触的长沟道一维场效应晶体管模型一致。利用具有石墨烯/MoS2 和 Ti/MoS2 接触的器件，测量了两个界面的肖特基势垒高度。根据热电子场发射模型，确定石墨烯/MoS2 界面的势垒高度为 0.23 eV，而 Ti/MoS2 界面的势垒高度为 0.40 eV。Ti/MoS2 势垒的价值高于以前的报告值，因为以前的报告值不包括热电子场发射的影响。
