Black phosphorus (BP) is a promising two-dimensional layered semiconductor material for next-generation electronics and optoelectronics, with a thickness-dependent tunable direct bandgap and high carrier mobility. Though great research advantages have been achieved on BP, lateral synthesis of high quality BP films still remains a great challenge. Here, we report the direct growth of large-scale crystalline BP films on insulating silicon substrates by a gas-phase growth strategy with an epitaxial nucleation design and a further lateral growth control. The optimized lateral size of the achieved BP films can reach up to millimeters, with the ability to modulate thickness from a few to hundreds of nanometers. The as-grown BP films exhibit excellent electrical properties, with a field-effect and Hall mobility of over 1200 cm2V−1s− 1 and 1400 cm2V−1s−1 at room temperature, respectively, comparable to those exfoliated from BP bulk crystals. Our work opens the door for broad applica tions with BP in scalable electronic and optoelectronic devices.
Black phosphorus (BP) is a promising two-dimensional (2D) layered semiconductor for next-generation electronics and optoelectronics, which owns high carrier mobility, thickness-dependent direct band gaps from 0.3 eV to ～ 1.5 eV as well as anisotropic nature1,2 , 3,4,5,6,7,8,9,10,11,12. To explore the full potential of BP, especially for various devices that can be integrated in silicon flows, it basically requires reliable synthesis of high-quality large-area BP films. Despite considerable efforts and some successful examples to date13,14,15, lateral growth of high-crystalline BP films, which hold promising electrical properties and meet the silicon device-scaling requirements, has not been realized. Here, for the first time, we report the direct growth of large-scale crystalline BP films on insulating silicon substrates by a newly developed gas-phase growth strategy with an epitaxial nucleation design and a further lateral growth control. The optimized lateral size of the achiev ed BP films can reach up to millimeters, with the thickness be modulated from few to hundreds of nanometers. The as-grown BP films exhibit excellent electrical properties with field-effect and Hall mobility of over 1000 cm2 V−1 s−1 and 1400 cm2 V−1 s−1 at room temperature, respectively, and current on / off ratio up to 106, comparable to those exfoliated from BP bulk crystals. In addition, extraordinary lamellar structure is explored with the synthesized BP films, which brings superior infrared optical characteristics with a strengthened infrared absorption and photoluminescence (PL). Our work demonstrates an important step forwards large-scale preparation of crystallized BP films and open the door for broad applications in scalable optoelectronic devices and compact integrated circuits.
Traditionally, BP can be prepared through the phase transfer of white or red phosphorus (RP) by high pressure and high-temperature route, mercury catalysis or by re-crystallization from a Bi-flux16,17,18. Making use of the phase change , recent progress on growing BP by a mineralizer-assisted gas-phase transformation method further improve the yield and crystallinity 1,19,20,21,22,23,24. However, to date, only BP in bulk crystals have been achieved in this way, whereas with no report on the success of growing crystalline BP thin films directly on wafers 25. Quite some efforts have been devoted to develop the direct growth of BP films on substrates recently. Lau et al. first report the growth of 2 nm-thick BP film on silicon using a pulsed laser deposition. However, the obtained film is amorphous, and the fabricated devices exhibit very low electronic performance 13. Xia's group synthesized a large-area (up to 4 mm) thin BP film on a flexible polyester substrate by converting RP film into BP film by pressurization in an anvil cell. But the grain size of the grown BP film is only 10 nm, bringing a very low mobility of only ~ 0.5 cm2 V−1 s−1, far from the practical applications 14. Further progress was made recently to improve the crystallinity of the BP films by a similar pressurization approach in transforming RP to BP at 1.5 GPa and 700 ° C on sapphire substrates. The mobility of the as-grown BP films can be improved to be ~ 160 cm2 V− 1 s−1 15. However, the extremely high-pressure might be a disadvantage to the choice of the growth substrates for BP. Thus, a milder growth conditions for high-quality BP films becomes necessary.
Further information please refer
https://www.nature.com/articles/s41467-020-14902-z