Improving the field-effect performance of Bi2S3 single nanowires by an asymmetric device fabrication.

High-quality Bi2 S3 nanowires are synthesized by chemical vapor deposition and their intrinsic photoresponsive and field-effect characteristics are explored in detail. Among the studied Au-Au, Ag-Ag, and Au-Ag electrode pairs, the device with stepwise band alignment of asymmetric Au-Ag electrodes has the highest mobility. Furthermore, it is shown that light can cause a sevenfold decrease of the on/off ratio. This can be explained by the photoexcited charge carriers that are more beneficial to the increase of Ioff than Ion . The photoresponsive properties of the asymmetric Au-Ag electrode devices were also explored, and the results show a photoconductive gain of seven with a rise time of 2.9 s and a decay time of 1.6 s.

Novel micro-rings of molybdenum disulfide (MoS2).

Recently, molybdenum disulfide (MoS(2)) has become a popular material due to its unique electrical and chemical properties, and its use as a potential substitute for graphene. Herein, we report a new two-step method by utilizing thermal evaporation-sulfurization to synthesize MoS(2) which possesses an innovative micro-ring structure. The average statistical values of the height, width and external diameter were 69 nm, 0.3 µm and 5.0 µm, respectively. Then the mechanism for the growth of such MoS(2) micro-rings was proposed. A device based on the MoS(2) micro-ring was prepared by electron beam lithography, and its electrical transport properties were determined at different temperatures.

Effect of electrical contact on the performance of Bi2S3 single nanowire photodetectors.

Bi2S3 single-crystalline nanowires are synthesized through a hydrothermal method and then fabricated into single nanowire photodetectors. Due to the different contact barrier between the gold electrode and Bi2S3 nanowires, two kinds of devices with different electrical contacts are obtained and their photoresponsive properties are investigated. The non-ohmic contact devices show larger photocurrent gains and shorter response times than those of ohmic contact devices. Furthermore, the influence of a focused laser on the barrier height between gold and Bi2S3 is explored in both kinds of devices and shows that laser illumination on the Au-Bi2S3 interface can greatly affect the barrier height in non-ohmic contact devices, while keeping it intact in ohmic contact devices. A model based on the surface photovoltage effect is used to explain this phenomenon.