Most of the current methods for the synthesis of two-dimensional materials (2DMs) require temperatures not compatible with traditional back-end-of-line (BEOL) processes in semiconductor industry (450 °C). Here, we report a general BiOCl-assisted chemical vapor deposition (CVD) approach for the low-temperature synthesis of 27 ultrathin 2DMs. In particular, by mixing BiOCl with selected metal powders to produce volatile intermediates, we show that ultrathin 2DMs can be produced at 280–500 °C, which are ~200–300 °C lower than the temperatures required for salt-assisted CVD processes. In-depth characterizations and theoretical calculations reveal the low-temperature processes promoting 2D growth and the oxygen-inhibited synthetic mechanism ensuring the formation of ultrathin nonlayered 2DMs. We demonstrate that the resulting 2DMs exhibit electrical, magnetic and optoelectronic properties comparable to those of 2DMs grown at much higher temperatures. The general low-temperature preparation of ultrathin 2DMs defines a rich material platform for exploring exotic physics and facile BEOL integration in semiconductor industry.

The limitation on the spintronic applications of van der Waals layered transition-metal dichalcogenide semiconductors is ascribed to the intrinsic nonmagnetic feature. Recent studies have proved that substitutional doping is an effective route to alter the magnetic properties of two-dimensional transition-metal dichalcogenides (TMDs). However, highly valid and repeatable substitutional doping of TMDs remains to be developed. Herein, we report group VIII magnetic transition metal-doped molybdenum diselenide (MoSe2) single crystals via a one-pot mixed-salt-intermediated chemical vapor deposition method with high controllability and reproducibility. The high-angle annular dark-field scanning transmission electron microscopy studies further confirm that the sites of Fe are indeed substitutionally incorporated into the MoSe2 monolayer. The Fe-doped MoSe2 monolayer with a concentration from 0.93% to 6.10% could be obtained by controlling the ratios of FeCl3/Na2MoO4. Moreover, this strategy can be extended to create Co­(Ni)-doped MoSe2 monolayers. The magnetic hysteresis (M–H) measurements demonstrate that group VIII magnetic transition-metal-doped MoSe2 samples exhibit room-temperature ferromagnetism. Additionally, the Fe-doped MoSe2 field effect transistor shows n-type semiconductor characteristics, indicating the obtainment of a room-temperature dilute magnetic semiconductor. Our approach is universal in magnetic transition-metal substitutional doping of TMDs, and it inspires further research interest in the study of related spintronic and magnetoelectric applications.

Numerous efforts have been made to synthesize 2D atomic semiconductor materials and their heterojunctions because of the diverse novel properties and potential applications in constructing next‐generation highly compact electronic and optoelectronic devices. However, intrinsic 2D p‐type semiconductor materials are still scarce. Herein, to enrich the p‐type 2D semiconductor family, epitaxial growth of a large‐area, ultrathin 2D nonlayered p‐type semiconductor α‐MnSe on mica with the thickness down to one unit crystal cell (0.9 nm) is reported. Moreover, the thickness of the α‐MnSe nanosheets can be systematically tailored from over 150 to 0.9 nm by increasing the flow rate of the carrier gas. X‐ray‐diffraction, transmission electron microscopy, and electron diffraction studies confirm that the resulting 2D nanosheets are high‐quality single crystals. The photodetector based on the p‐type α‐MnSe nanosheet shows a fast response time of 4 ms. Furthermore, α‐MnSe/WS2 heterojunctions are synthesized and a diode based on p‐type α‐MnSe and n‐type WS2 displays outstanding photodetectivity (1.00 × 1013 Jones), high photoresponsivity (49.1 A W−1), and an obvious rectification ratio (283). Together, the synthesis of α‐MnSe and the α‐MnSe/WS2 p–n heterojunction provides opportunities for next‐generation electronics and optoelectronics.

No abstract

No abstract