Growth of Large-Area and Highly Crystalline MoS₂ Thin Layers on Insulating Substrates

The two-dimensional layer of molybdenum disulfide (MoS₂) has recently attracted much interest due to its direct-gap property and potential applications in optoelectronics and energy harvesting. However, the synthetic approach to obtain high-quality and large-area MoS₂ atomic thin layers is still rare. Here we report that the high-temperature annealing of a thermally decomposed ammonium thiomolybdate layer in the presence of sulfur can produce large-area MoS₂ thin layers with superior electrical performance on insulating substrates. Spectroscopic and microscopic results reveal that the synthesized MoS₂ sheets are highly crystalline. The electron mobility of the bottom-gate transistor devices made of the synthesized MoS₂ layer is comparable with those of the micromechanically exfoliated thin sheets from MoS₂ crystals. This synthetic approach is simple, scalable, and applicable to other transition metal dichalcogenides. Meanwhile, the obtained MoS₂ films are transferable to arbitrary substrates, providing great opportunities to make layered composites by stacking various atomically thin layers

Single CuO_<i>x</i> Nanowire Memristor: Forming-Free Resistive Switching Behavior

CuO_<i>x</i> nanowires were synthesized by a low-cost and large-scale electrochemical process with AAO membranes at room temperature and its resistive switching has been demonstrated. The switching characteristic exhibits forming-free and low electric-field switching operation due to coexistence of significant amount of defects and Cu nanocrystals in the partially oxidized nanowires. The detailed resistive switching characteristics of CuO_<i>x</i> nanowire systems have been investigated and possible switching mechanisms are systematically proposed based on the microstructural and chemical analysis via transmission electron microscopy

Synthesis and Transfer of Single-Layer Transition Metal Disulfides on Diverse Surfaces

Recently, monolayers of layered transition metal dichalcogenides (LTMD), such as MX₂ (M = Mo, W and X = S, Se), have been reported to exhibit significant spin-valley coupling and optoelectronic performances because of the unique structural symmetry and band structures. Monolayers in this class of materials offered a burgeoning field in fundamental physics, energy harvesting, electronics, and optoelectronics. However, most studies to date are hindered by great challenges on the synthesis and transfer of high-quality LTMD monolayers. Hence, a feasible synthetic process to overcome the challenges is essential. Here, we demonstrate the growth of high-quality MS₂ (M = Mo, W) monolayers using ambient-pressure chemical vapor deposition (APCVD) with the seeding of perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS). The growth of a MS₂ monolayer is achieved on various surfaces with a significant flexibility to surface corrugation. Electronic transport and optical performances of the as-grown MS₂ monolayers are comparable to those of exfoliated MS₂ monolayers. We also demonstrate a robust technique in transferring the MS₂ monolayer samples to diverse surfaces, which may stimulate the progress on the class of materials and open a new route toward the synthesis of various novel hybrid structures with LTMD monolayer and functional materials