Search

Devices that rely on the manipulation of excitons--bound pairs of electrons and holes--hold great promise for realizing efficient interconnects between optical data transmission and electrical processing systems. Although exciton-based transistor actions have been demonstrated successfully in bulk semiconductor-based coupled quantum wells.sup.1-3, the low temperature required for their operation limits their practical application. The recent emergence of two-dimensional semiconductors with large exciton binding energies.sup.4,5 may lead to excitonic devices and circuits that operate at room temperature. Whereas individual two-dimensional materials have short exciton diffusion lengths, the spatial separation of electrons and holes in different layers in heterostructures could help to overcome this limitation and enable room-temperature operation of mesoscale devices.sup.6-8. Here we report excitonic devices made of MoS.sub.2-WSe.sub.2 van der Waals heterostructures encapsulated in hexagonal boron nitride that demonstrate electrically controlled transistor actions at room temperature. The long-lived nature of the interlayer excitons in our device results in them diffusing over a distance of five micrometres. Within our device, we further demonstrate the ability to manipulate exciton dynamics by creating electrically reconfigurable confining and repulsive potentials for the exciton flux. Our results make a strong case for integrating two-dimensional materials in future excitonic devices to enable operation at room temperature.Heterobilayer excitonic devices consisting of two different van der Waals materials, in which excitons are shared between the layers, exhibit electrically controlled switching actions at room temperature., Author(s): Dmitrii Unuchek [sup.1] [sup.2] , Alberto Ciarrocchi [sup.1] [sup.2] , Ahmet Avsar [sup.1] [sup.2] , Kenji Watanabe [sup.3] , Takashi Taniguchi [sup.3] , Andras Kis [sup.1] [sup.2] Author Affiliations:(1) [...]

Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as 'blue energy' (1-3). Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient (4) or by an osmotic potential resulting from a salt concentration gradient (5). For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness (5-7). Here we demonstrate the use of single-layer molybdenum disulfide (Mo[S.sub.2]) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to [10.sup.6] watts per square metre--a current that can be attributed mainly to the atomically thin membrane of Mo[S.sub.2]. Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment (8-11)--for example, a piezoelectric zinc oxide nanowire array (8) or single-layer Mo[S.sub.2] (ref. 12). We use our Mo[S.sub.2] nanopore generator to power a Mo[S.sub.2] transistor, thus demonstrating a self-powered nanosystem., Mo[S.sub.2] nanopores have already demonstrated better water-transport behaviour than graphene (13,14) owing to the enriched hydrophilic surface sites (provided by the molybdenum) that are produced following either irradiation with transmission [...]