Study On Preparation And Doping Of Orthorhombic Black Phosphorus

The emergence of graphene has set off a research upsurge on two-dimensional materials.Compared with bulk materials,most two-dimensional materials have the characteristics of ultra-thin limit channel thickness and high carrier mobility,which is expected to bring new light to the development of microelectronic devices in the post-Molar era.Among them,two-dimensional layered materials such as graphene and molybdenum disulfide have shown considerable application prospects in many fields.However,their inherent shortcomings hinder the extensive applications in semiconductor devices to a certain extent.By comparison,black phosphorus（BP）will be hoping to become one of the new generations of semiconductor materials,owing to its excellent properties such as adjustable direct bandgap,suitable carrier mobility,and switching ratio,obvious in-plane anisotropy,favorable mechanical flexibility,and biocompatibility,and so on.In recent years,low dimensional BP has attracted increasing attention due to its excellent and unique physical and chemical properties.Nevertheless,high-quality bulk BP is the prerequisite for exfoliating low-dimensional BP.At present,the process parameters for fabricating BP crystals by the chemical vapor transport（CVT）method still need to be further optimized.Besides,environmental degradation of thin-layer BP also partly impedes its application and development.Herein,the high yield orthorhombic BP and doped BP were prepared in one step by the constant-temperature CVT method,and their material properties and stability were discussed combined with relevant characterization.The main research contents and results are as follows:（1）Different mineralizers,different ratios of tin and iodine,different heating patterns,and temperatures were employed as research variables,and optimizing the process parameters of orthorhombic BP was prepared by the CVT method.The results indicate that it’s suitable for the synthesis of large-size bulk orthorhombic BP via the optimized process parameters such as microwave heating,nucleation temperature of about 515℃,and the ratio of 0.47 for the tin to iodine.Combined with the nucleation and growth mechanism of BP,it can be seen that both tin and iodine play a vital role in the growth of BP,while the mineralized effect of iodine is more obvious than tin.Iodine is the key to the nucleation and growth of BP,and the yield of BP increases with the increasing iodine content.The mineralized effect of tin can be replaced by other metals（like lead）,but the appropriate amount of tin is conducive to the formation of bulk BP without the temperature gradient.（2）A 96%yield of bulk BP was obtained by the constant-temperature CVT method with Sn and Sn I₄ as mineralizers.On this basis,the large-size doped BP was further fabricated,and the stability of the pristine BP and doped BP was studied combined with the change of surface morphology.The results show that the CVT method can be employed to prepare bulk doped BP with a yield of over 90%,which indicates other BP complexes can be promoted by the method.The introduction of stibium（Sb）and bismuth（Bi）into the BP lattice will not cause lattice distortion and destroy the orthorhombic structure of BP.In addition,the antioxidation of BP can be beneficial to heighten antioxidation by Sb doped,which is good for enhancing the stability of BP.