Two-dimensional materials are attractive for use in next-generation nanoelectronic devices because, compared to one-dimensional materials, it is relatively easy to fabricate complex structures from them. The most widely studied two-dimensional material is graphene, both because of its rich physics and its high mobility. However, pristine graphene does not have a bandgap, a property that is essential for many applications, including transistors. Engineering a graphene bandgap increases fabrication complexity and either reduces mobilities to the level of strained silicon films or requires high voltages. Although single layers of MoS(2) have a large intrinsic bandgap of 1.8 eV (ref. 16), previously reported mobilities in the 0.5-3 cm(2) V(-1) s(-1) range are too low for practical devices. Here, we use a halfnium oxide gate dielectric to demonstrate a room-temperature single-layer MoS(2) mobility of at least 200 cm(2) V(-1) s(-1), similar to that of graphene nanoribbons, and demonstrate transistors with room-temperature current on/off ratios of 1 × 10(8) and ultralow standby power dissipation. Because monolayer MoS(2) has a direct bandgap, it can be used to construct interband tunnel FETs, which offer lower power consumption than classical transistors. Monolayer MoS(2) could also complement graphene in applications that require thin transparent semiconductors, such as optoelectronics and energy harvesting.

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Single-layer MoS2 transistors

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

Novel physical phenomena can emerge in low-dimensional nanomaterials. Bulk MoS2, a prototypical metal dichalcogenide, is an indirect bandgap semiconductor with negligible photoluminescence. When the MoS2 crystal is thinned to monolayer, however, a strong photoluminescence emerges, indicating an indirect to direct bandgap transition in this d-electron system. This observation shows that quantum confinement in layered d-electron materials like MoS2 provides new opportunities for engineering the electronic structure of matter at the nanoscale.

Emerging Photoluminescence in Monolayer MoS2

TiO2 photocatalysis and related surface phenomena

Neutron scattering results on the lattice dynamics and Peierls phase transition of (TaSe 4 ) 2 I are presented. The room temperature phonon dispersion curves reflect the stiffness of the (TaSe 4 )∞ chains and the comparatively weak transverse interchain interactions. The response of the [110] polarised TA mode, connected with the Peierls instability, is found to be weakly temperature-dependent. Correlation lengths associated with the diverging «central peak» are determined and are found to be nearly isotropic. We discuss the significance of these results from the point of view of electron-phonon theory and stress the importance of allowing for the interaction between optic and elastic degrees of freedom

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Neutron study of the Peierls transition and low-frequency excitations in (TaSe4)2I

Atomic Scale Investigations of Transition Metal Dichalcogenides by Scanning Tunneling Microscopy and Atomic Force Microscopy

High sensitivity ultrafast nanowire superconducting single photon detectors (SSPD) in the near infrared wavelength range have been fabricated with ultrathin (3.5nm) NbN films grown on R-plane sapphire substrates by dc reactive magnetron sputtering in Ar+N2 mixture. These results show for the first time that high performance NbN SSPDs can be realized on different substrates and at lower deposition temperature than previously reported, and opens the way to integration with advanced solid state optical structures. SSPDs have been fabricated by a two mask process using electron beam lithography and reactive ion etching on 3.5nm thick NbN films deposited under optimal conditions on MgO.

NbN nanowire superconducting single photon detectors fabricated on MgO substrates

The chemical transport reaction, known as a standard method for growth of transition metal dichalcogenides, was found to be a successful technique for the synthesis of MoS 2 and WS 2 inorganic nanotubes. While microtubes usually grow as single tubes, the nanotubes combine to build ropes formed by coaxial or side-by-side growth of primary nanotubes. The nanoropes also grow by self-assembly of the nanotube or by coalescence of single tubes. Association of nanotubes or narrow nanoropes reveals the effect of attractive long-range forces.

Francis Lévy

Papers

Neutron study of the Peierls transition and low-frequency excitations in (TaSe4)2I

Atomic Scale Investigations of Transition Metal Dichalcogenides by Scanning Tunneling Microscopy and Atomic Force Microscopy

NbN nanowire superconducting single photon detectors fabricated on MgO substrates

Self-assembly of Inorganic Nanotubes Synthesised by the Chemical Transport Reaction

Doping (TaSe4)2I with Manganese