Search for: All records

Lateral multiheterostructures with spatially modulated bandgaps have great potential for applications in high-performance electronic, optoelectronic and thermoelectric devices. Multiheterostructures based on transition metal tellurides are especially promising due to their tunable bandgap in a wide range and the rich variety of structural phases. However, the synthesis of telluride-based multiheterostructures remains a challenge due to the low activity of tellurium and the poor thermal stability of tellurium alloys. In this work, we synthesized monolayer WSe 2−2 x Te 2 x /WSe 2−2 y Te 2 y ( x > y ) multiheterostructures in situ using chemical vapor deposition (CVD). Photoluminescence analysis and Raman mapping confirm the spatial modulation of the bandgap in the radial direction. Furthermore, field-effect transistors with the channels parallel (type I) and perpendicular (type II) to the multiheterostructure rings were fabricated. Type I transistors exhibit enhanced ambipolar transport, due to the low energy bridges between the source and drain. Remarkably, the photocurrents in type I transistors are two orders of magnitude higher than those in type II transistors, which can be attributed to the fact that the photovoltaic photocurrents generated at the two heterojunctions are summed together in type I transistors, but they cancel each other in type II transistors. These multiheterostructures will provide a new platform for novel electronic/photonic devices with potential applications in broadband light sensing, highly sensitive imaging and ultrafast optoelectronic integrated circuits. 

Device engineering based on the tunable electronic properties of ternary transition metal dichalcogenides has recently gained widespread research interest. In this work, monolayer ternary telluride core/shell structures are synthesized using a one‐step chemical vapor deposition process with rapid cooling. The core region is the tellurium‐rich WSe_2−2xTe_2xalloy, while the shell is the tellurium‐poor WSe_2−2yTe_2yalloy. The bandgap of the material is ≈1.45 eV in the core region and ≈1.57 eV in the shell region. The lateral gradient of the bandgap across the monolayer heterostructure allows for the fabrication of heterogeneous transistors and photodetectors. The difference in work function between the core and shell regions leads to a built‐in electric field at the heterojunction. As a result, heterogeneous transistors demonstrate a unidirectional conduction and strong photovoltaic effect. The bandgap gradient and high mobility of the ternary telluride core/shell structures provide a unique material platform for novel electronic and photonic devices.