Modulation Of Electrical Property Of 2d Black Phosphorus And Fabrication And Characterization Of Its Logic Devices

Black phosphorus(BP)is a p-type semiconducting nanomaterial with sizeable band gap from ~0.3 eV in bulk form to ~1.8 eV in monolayer form,hole mobilities of ~200-1000 cm2V-1S-1 at room temperature,and anisotropic transport characteristics.Based on these superior properties,various BP devices,such as field-effect transistors(FET),phototransistors,heterojunctions,gas sensors,complementary logic inverters and so on,have been demonstrated since its discovery.However,black phosphorus tend to react with water and oxygen molecules in the air which will degrade its electrical properity badly.Besides,native black phosphorus is a P type semiconductor which means that researchers need a stable doping method to change P-type black phosphorus into N-type black phosphorus so that they can fully take advantages of black phosphorus.Therefore,in this thesis,we focus on the research of finding new methods to overcome the instability of black phosphorus and at the same time developing strategies to complementally dope black phosphorus thin flakes.Our main results are listed as below:1.We managed to protect black phosphorus devices with cross-linked PMMA, during which process,we found the doping effect of cross-linked PMMA on black phosphorus and fabricated a series of planar devices by using this effect.2.By systematically studying the doping effect of cross-linked PMMA,we put forward the doping mechanism,and successfully applied it to other two dimensional materials.3.By dual gate modulation,we achieved the function of bidirectional rectifier and polarity controllable transistor on one single device,which may do good to the design and integration of logic devices.4.By mechanical exfoliation method,we successfully transferred few layer black phosphorus thin flakes onto the surface of graphene which was grown onto the Si substrate with 300 nm Silicon oxide to form black phosphorus-graphene heterojunction,electrical characterization of this heterojunction revealed that the barrier formed at the interface can be neglected,meaning graphene can be a good contact to few layer black phosphorus devices.