Nature of electronic states in atomically thin MoS₂ field-effect transistors.

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.

[1]  Arindam Ghosh,et al.  Microscopic mechanism of 1/f noise in graphene: role of energy band dispersion. , 2011, ACS nano.

[2]  Webb,et al.  Observation of resonant tunneling in silicon inversion layers. , 1986, Physical review letters.

[3]  Andre K. Geim,et al.  Two-dimensional atomic crystals. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[4]  Efros,et al.  Maximum low-temperature mobility of two-dimensional electrons in heterojunctions with a thick spacer layer. , 1990, Physical review. B, Condensed matter.

[5]  Arindam Ghosh,et al.  Resistance noise in electrically biased bilayer graphene. , 2008, Physical review letters.

[6]  Hugen Yan,et al.  Anomalous lattice vibrations of single- and few-layer MoS2. , 2010, ACS nano.

[7]  S. Sarma,et al.  Theory of charged impurity scattering in two-dimensional graphene , 2008, 0812.1795.

[8]  K. Klitzing,et al.  Observation of electron–hole puddles in graphene using a scanning single-electron transistor , 2007, 0705.2180.

[9]  N. Mott,et al.  Electronic Processes In Non-Crystalline Materials , 1940 .

[10]  Michael S. Fuhrer,et al.  Realization and electrical characterization of ultrathin crystals of layered transition-metal dichalcogenides , 2007 .

[11]  F. V. Keuls,et al.  Screening of the Coulomb interaction in two-dimensional variable-range hopping , 1997 .

[12]  S. Das Sarma,et al.  Boltzmann transport and residual conductivity in bilayer graphene , 2007, 0711.0003.

[13]  Andre K. Geim,et al.  Electric Field Effect in Atomically Thin Carbon Films , 2004, Science.

[14]  A. Splendiani,et al.  Emerging photoluminescence in monolayer MoS2. , 2010, Nano letters.

[15]  J. Shan,et al.  Atomically thin MoS₂: a new direct-gap semiconductor. , 2010, Physical review letters.

[16]  Charles G. Sodini,et al.  A 1/f noise technique to extract the oxide trap density near the conduction band edge of silicon , 1989 .

[17]  A. Radenović,et al.  Single-layer MoS2 transistors. , 2011, Nature nanotechnology.

[18]  M. Pepper,et al.  The spatial extent of localized state wavefunctions in silicon inversion layers , 1974 .

[19]  H. Beere,et al.  Density-dependent instabilities in correlated two?dimensional electron systems , 2004 .

[20]  E. Linfield,et al.  Electron Assisted Variable Range Hopping in Strongly Correlated 2D Electron Systems , 2002 .

[21]  G. Paasch,et al.  Variable range hopping as possible origin of a universal relation between conductivity and mobility in disordered organic semiconductors , 2002 .