Preparation Of 2D Novel Semiconductor Bi₂O₂Se And The Optoelectronic Properties Based On The Heterostructure

The current development of silicon-based chip technology is approaching the physical limit,when the channel length of silicon-based transistors is reduced to the nanometer scale,the leakage current introduced by the short-channel effect will seriously affect the performance of the device,the use of nanomaterials is a breakthrough to solve the problem.Benefiting from the flatness of two-dimensional（2D）materials at the nanometer scale,2D materials are expected to be potential materials for the continuation of"Moore’s Law"and the further integration of chips.To meet the needs of the new generation of electronic devices,novel 2D electronic materials should have suitable band gaps,good environmental stability and high carrier mobility.The widely studied 2D materials,however,have shortcomings such as low mobility,poor stability or no suitable band gap,which cannot meet the requirements of large-scale applications.Therefore,the growth of new 2D semiconductor materials,the development of large-scale preparation methods for two-dimensional semiconductor materials,and the exploration of the application of new two-dimensional semiconductor materials are of great significance for the development of chip technology and information technology.At present,a new type of 2D semiconductor material bismuth selenide oxide（Bi₂O₂Se）has received wide attention,Bi₂O₂Se hold the advantages of suitable band gap,high mobility,and environmental stability.Also,due to its excellent optoelectronic properties,the application of Bi₂O₂Se in the field of optoelectronics has been widely concerned.In this paper,we focus on the preparation of Bi₂O₂Se and the research of device based on Bi₂O₂Se as follows:（Ⅰ）High-quality Bi₂O₂Se nanosheets and large-sacle Bi₂O₂Se films were prepared by atomic layer deposition（ALD）-assisted chemical vapor deposition（CVD）method,and the effects of different factors in the growth process were investigated during the synthesis of Bi₂O_3-δfilms by ALD and those during the synthesis of Bi₂O₂Se by CVD.In this paper,Bi₂O₂Se thin film and nanosheet were prepared by ALD-assisted CVD method,and the chemical process of the reaction was discussed in detail.The Bi₂O_3-δfilms prepared by ALD were used as a bismuth source to participate in the growth of Bi₂O₂Se,and the preparation of different Bi₂O₂Se samples（thin films,nanosheets）was mainly achieved by controlling the substrate type and reaction temperature.Due to the lattice match between F-mica substrate and Bi₂O₂Se,F-mica substrate can induce the horizontal growth of Bi₂O₂Se during the growth process,so the mica substrate was chosen as the substrate to form the nanosheets.As a comparison,the Bi₂O₂Se films prepared on silicon substrate are in the form of three-dimensional growth.（Ⅱ）The preparation of digital and analog memristors based on the high mobility 2D semiconductor Bi₂O₂Se and its oxides was achieved.2D Bi₂O₂Se is the semiconductor with high carrier mobility,while its natural Bi₂SeO₅is the insulator material with a wide bandgap（～3.9 eV）,and the Au/Bi₂O₂Se/Bi₂SeO₅/Au can be formed naturally by introducing oxygen in the CVD process.To constructing this semiconductor/insulator heterojunction,the abrupt digital memristor can be constructed,which has a switching ratio of>10⁴with the data retention time>100 s.Thus,we demonstrate that the lateral heterostructure composed of Bi₂O₂Se and its oxides can be used for the non-volatile memory.In addition to this,the regions of incomplete oxidation contian a lot of defect,and these oxidation-generated defects can be used as charge capture sites for electronic.Base on the defect-trapping effect,the preparation of Au/Bi₂O₂Se/Bi₂O_xSe_y/Au analog memristors was achieved,whose resistive resistance can change tunably with the applied pulse voltage/light,and the change of resistance keeps good linearity within multiple pulses with the light pulses,which indicates that the device can be applied in neurosynthetic computing and also demonstrates that Bi₂O₂Se and its oxides can be used to construct artificial synaptic devices and simulating neurosynaptic behavior.