Investigation On The Controllable Growth And Carrier Regulation Of Black Phosphorus

In the past decades,two-dimensional materials have attracted great attentions in the field of materials,and black phosphorus is a new star member of two-dimensional materials due to its excellent properties.Black phosphorus has a layer-dependent direct band gap(bulk 0.3～single layer 2.0 eV),which fills the gap between graphene and transition metal dichalcogenides.Black phosphorus also exhibits strong in-plane anisotropy and high field-effect mobility(hole mobility is 1000 cm2V-1s-1 at room temperature,6000 cm2V-1s-1 at low temperature),which make black phosphorus attractive for widely applications.However,there are still many problems and challenges in the research of black phosphorus:controllable growth of low-cost,high-quality black phosphorus single crystals;stability and passivation of black phosphorus;controllable doping and physical property adjustment of black phosphorus.The solution of the above-mentioned problems is related to the in-depth research and the application of black phosphorus.Based on this,the article will take an in-depth reaserch on the following issues:(1)We grow high-quality black phosphorus single crystals by selecting suitable mineralizers and using chemical vapor transport.The experimental results show that the quality of black phosphorus single crystal grown with lead as a mineralizer is better.The field effect transistor performance test based on black phosphorus flakes shows that black phosphorus with lead(Pb-BP)has significantly higher hole mobility than black phosphorus with tin(Sn-BP).At the same time,the Pb-BP field-effect transistor exhibits good bipolarity.The highest hole mobility at room temperature reachs 523 cm2V-1s-1,and the highest electron mobility is 28 cm2V-1s-1.(2)The single crystal black phosphorous nanoribbons are successfully grown by controlling the growth conditions.Microstructure analysis shows that the zigzag direction is the preferential growth direction of the nanoribbons.The performance of the field-effect transistor based on black phosphorous nanoribbons shows that it has good electrical properties.(3)Carrier control of black phosphorus is carried out through element doping and surface charge transfer doping.Te doping of high-quality black phosphorous single crystals has synthesized successfully.XPS and EDX show that the atomic percentage of Te doping is 0.1%.A field effect transistor based on Te-doped black phosphorus was fabricated,showing obvious bipolarity.The statistical results show that the black phosphorus doped with Te has significantly higher hole mobility than the undoped black phosphorus.The highest hole mobility at room temperature reachs 719 cm2V-1s-1,and the electron mobility can reach 63 cm2V-1s-1.In addition,we deposit platinum to modify the black phosphorous field effect transistor,and control the deposition time to adjust the carriers.The p-type black phosphorous field effect transistor can be adjusted to be bipolar or even single n-type,with a maximum electron mobility of 240 cm2V-1s-1.(4)Use CaH2 to anneal the black phosphorus to improve its performance.The black phosphorus sample does not contact CaH2.The H2 decomposed by CaH2 will reverse the degraded black phosphorus and improve its electrical properties.It can be adjusted to be obviously bipolar by controlling the annealing time;the black phosphorus sample contact CaH2,which can increase carrier concentration of the black phosphorus.In summary,we have researched systematically on the controlled growth,doping,and carrier regulation of high-quality single crystal black phosphorus,and have gotten a series of valuable research results.It has proved the foundation for the in-depth research and practical application of black phosphorus.