Professor Xiangfeng Duan and colleagues have come up with a new way to grow 2D-layered semiconductor heterostructures whose composition can be controlled by modulating the constituent vapour-phase reactants during growth.
Nanotechweb.org (by Belle Dume): Researchers at the University of California at Los Angeles in the US and Hunan University in Changsha, China, have come up with a new way to grow 2D-layered semiconductor heterostructures whose composition can be controlled by modulating the constituent vapour-phase reactants during growth. The structures produced are single crystals and might be used to make a host of electronics devices, ranging from complementary logic circuits, photovoltaics and photodetectors, to light-emitting diodes and laser diodes.
2D materials like molybdenite (MoS2) and tungstenite (WS2) are creating a flurry of interest in labs around the world because they have dramatically different electronic and mechanical properties from their 3D counterparts. This means that they could find use in novel device applications, such as low-power electronic circuits, low-cost or flexible displays, sensors and even flexible electronics that can be coated onto a wide variety of surfaces.
Growing a lateral heterostructure
The most well known 2D materials are graphene (which is a sheet of carbon just one atom thick) and the transition metal dichalcogenides (TMDs). These so-called van der Waals (vdW) structures have the chemical formula MX2, where M is a transition metal (such as Mo or W) and X is a chalcogen (such as S, Se and Te). TMDs have an added advantage in that they go from being indirect bandgap semiconductors in the bulk to direct bandgap semiconductors when scaled down to monolayers. These monolayers efficiently absorb and emit light and so could be ideal for making a variety of optoelectronics devices such as photodetectors and light-emitting diodes.
Creating well defined heterostructures
“To explore the full potential of these layered semiconductors, however, will require precisely modulating their chemical, structural and electronic properties to create well-defined heterostructures,” explains team leader Xiangfeng Duan. “These structures will be much like traditional semiconductor heterostructures, which make up all modern electronics and optoelectronics devices.”
The researchers say that they have now succeeded in laterally growing 2D-layered heterostructures consisting of tungstenite-tungsten selenide (WS2-WSe2) and molybdenite-molybdenum diselenide (MoS2-MoSe2). They have also proved that these structures can be used to create a series of functional devices, including p-n diodes, photodiodes and complementary inverters.
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The research findings were published in Nature Nanotechnology.