Semiconductive transition metal dichalcogenides (TMDs) have been considered as next generation semiconductors, but to date most device investigations are still based on microscale exfoliation with a low yield. Wafer scale growth of TMDs has been reported but effective doping approaches remain challenging due to their atomic thick nature. In this work, we report the synthesis of wafer-scale continuous few-layer PtSe 2 films with effective doping in a controllable manner. Chemical component analyses confirm that both n-and pdoping can be effectively modulated through the controlled selenization process. We systematically study the electrical properties of PtSe 2 films by fabricating top-gated field effect transistors (FETs). The device current on/off ratio is optimized in two-layer PtSe 2 FETs, and four-terminal configuration displays a reasonably high effective field effect mobility (14 and 15 cm 2 V -1 s -1 for p-and n-type FETs, respectively) with a nearly symmetric p-and n-type performance. Temperature dependent measurement reveals that the variable range hopping is dominant at low temperature. To further establish the feasible application based on controllable doping of PtSe 2 , a logic inverter and vertically stacked p-n junction arrays are demonstrated. These results validate that PtSe 2 is a promising candidate among the family of TMDs for future functional electronic applications.

Two‐dimensional (2D) materials have attracted increasing attention for their outstanding structural and electrical properties. However, for mass‐production of field effect transistors (FETs) and potential applications in integrated circuits, large‐area and uniform 2D thin films with high mobility, large on‐off ratio, and desired polarity are needed to synthesize firstly. Here, a transfer‐free growth method for platinum diselenide (PtSe2) films has been developed. The PtSe2 films have been synthesized with various thicknesses in centimeter‐sized scale. Typical FET made from a few layer PtSe2 show p‐type unipolar, with a high field‐effect hole mobility of 6.2 cm2 V−1 s−1 and an on‐off ratio of 5 × 103. The versatile semimetal‐unipolar‐ambipolar transition in synthesized PtSe2 films is also firstly observed as the thickness thinning. This work realizes the large‐scale preparation of PtSe2 with prominent electrical properties and provides a new strategy for polarity's modulation.

Monolayer hexagonal boron nitride (h-BN) possesses a wide bandgap of ~6 eV. Trimming down the bandgap is technically attractive, yet poses remarkable challenges in chemistry. One strategy is to topological reform the h-BN’s hexagonal structure, which involves defects or grain boundaries (GBs) engineering in the basal plane. The other way is to invite foreign atoms, such as carbon, to forge bizarre hybrid structures like hetero-junctions or semiconducting h-BNC materials. Here we successfully developed a general chemical method to synthesize these different h-BN derivatives, showcasing how the chemical structure can be manipulated with or without a graphene precursor, and the bandgap be tuned to ~2 eV, only one third of the pristine one’s.

Electrocatalytic reduction of N2 to NH3 under an ambient atmosphere is highly desirable and extremely critical for energy-efficient nitrogen utilization. Inspired by the natural MoFe protein-based enzyme, the nitrogenase, we exploited this electrochemical process with a unique two-dimensional catalyst, namely, molybdenum carbide (Mo2C). The catalyst is synthesized through a chemical vapor deposition method, with a highly orientated (200) facet of the α-Mo2C phase. A remarkable Faradaic efficiency as high as 40.2% has been achieved on the (200) faceted α-Mo2C during the nitrogen reduction reaction (NRR). Density functional theory calculations confirm that rate-determining steps *NNH2 → *NNH3 and *NH → *NH2 experience a low energy barrier on the (200) surface following the proton–electron coupled, distal associated mechanism. To protect Mo from leaching during the NRR process, we also grew layers of graphene on top of Mo2C, forming a chemically enduring two-dimensional heterostructured electrode.

2D transition metal dichalcogenides (TMDs) have presented outstanding potential for efficient hydrogen evolution reaction (HER) to replace traditional noble metal catalysts. Here, to achieve enhanced HER performance, specific areas of the few-layer 1T′-MoTe 2 film are precisely controlled with a focused ion beam to create particular active sites. Electrochemical measurements indicate that the HER performance, although inconspicuous in pristine 1T′-MoTe 2 ultrathin films prepared through the chemical vapor deposition method, can be greatly enhanced after patterning and precisely controlled by the morphologies as well as the amounts of the defects, reaching a small onset potential and a record-low Tafel slope of 44 mV per decade for few-layer TMDs. Conductivity tests, visualized copper electrodeposition, and density functional theory calculations also confirm that the enhancement of HER performance comes from the exposed edges by patterning. In this pioneering work, not only is the catalysis mechanism of the edge active sites of 1T′-MoTe 2 unveiled, but also a universal route to study the properties of 2D materials is demonstrated.