Abrupt Thermal Shock of (NH4)2Mo3S13 Leads to Ultrafast Synthesis of Porous Ensembles of MoS2 Nanocrystals for High Gain Photodetectors

作者：Islam, Saiful M.; Sangwan, Vinod K.; Li, Yuan; Kang, Joohoon; Zhang, Xiaomi; He, Yihui; Zhao, Jing; Murthy, Akshay; Ma, Shulan; Dravid, Vinayak P.; Hersam, Mark C.; Kanatzidis, Mercouri G.^*

来源：ACS Applied Materials & Interfaces, 2018, 10(44): 38193-38200.

DOI：10.1021/acsami.8b12406

• solid-state synthesis
• porous MoS2 nanocrystal
• thin films
• photodetector

Ultrafast synthesis of high-quality transition-metal dichalcogenide nano-crystals, such as molybdenum disulfide (MoS2), is technologically relevant for large-scale production of electronic and optoelectronic devices. Here, we report a rapid solid-state synthesis route for MoS2 using the chemically homogeneous molecular precursor, (NH4)(2)Mo3S13 center dot H2O, resulting in nanoparticles with estimated size down to 25 nm only in 10 s at 1000 degrees C. Despite the extreme nonequilibrium conditions, the resulting porous MoS2 nanoparticles remain aggregated to preserve the form of the original rod shape bulk morphology of the molecular precursor. This ultrafast synthesis proceeds through the rapid decomposition of the precursor and rearrangement of Mo and S atoms coupled with simultaneous efficient release of massive gaseous species, to create nanoscale porosity in the resulting isomorphic pseudocrystals, which are composed of the MoS2 nanoparticles. Despite the very rapid escape of massive amounts of NH3, H2O, H2S, and S gases from the (NH4)(2)Mo3S13 center dot H2O mm sized crystals, they retain their original shape as they convert to MoS2 rather than undergo explosive destruction from the rapid escape process of the gases. The obtained pseudocrystals are made of aggregated MoS2 nanocrystals exhibit a Brunauer-Emmett-Teller surface area of similar to 35 m(2)/g with an adsorption average pore width of similar to 160 angstrom. The nanoporous MoS2 crystals are solution processable by dispersing in ethanol and water and can be cast into large-area uniform composite films. Photodetectors fabricated from these films show more than 2 orders of magnitude higher conductivity similar to 6.25 x 10(-6) S/cm) and photoconductive gain (20 mA/W) than previous reports of MoS2 composite films. The optoelectronic properties of this nanoporous MoS2 imply that the shallow defects that originate from the ultrafast synthesis act as sensitizing centers that increase the photocurrent gain via two-level recombination kinetics.

• 出版日期2018-11-7
• 单位西北大学; 北京师范大学