Preparation Of Two-Dimensional MnSe And Investigation Of Its Photoelectric Properties

The scientific research on traditional photoelectric functional materials（such as Silicon（Si）,Germanium（Ge）,etc.）has promoted the rapid development of electronics,optics and information technology which has greatly changed human life.However,with the development of the photoelectric technology industry,the preparation and processing techniques of various electronic devices have reached the microscopic scale and the requirements for photoelectric devices have become higher and higher.The next generation of photodetectors is moving to room temperature,wide-band,and ultra sensitive,ultra-small pixels and multi-dimensional optical information detection.The low-dimensional of the two-dimensional material allows it to obtain lower dark current and noise.Two-dimensional material is one of the hot spots for replacing traditional materials such as silicon.Mn Se has excellent photoelectric properties,a wide band gap（approximately 2.0 e V）and a non-layered structure.The two-dimensional Mn Se is expected to produce novel photoelectric properties which is suitable for constructing high-performance and high stability photodetectors.However,the properties of its non-layered structure increase the difficulty of preparing its two-dimensional structure.So far,the preparation of two-dimensional Mn Se structure has remained at the thin film stage.Aiming at the above-mentioned difficulties,this paper uses the method of space-confined chemical vapor deposition（CVD）to synthesize two-dimensionalα-Mn Se and summarizes its growth pattern by adjusting the growth parameters.At the same time,scanning electron microscope（SEM）,transmission electron microscope（TEM）,Raman and other characterization methods were used to confirm the composition,crystal phase and luminescence characteristics of the samples.We successfully constructed a two-dimensionalα-Mn Se based photodetector and measured its photoelectric performance.In addition,we extended the space-confined CVD method to the preparation of non-layered two-dimensional material Ga₂Se₃and used liquid metal to assist the growth of it.Ga₂Se₃is a kind of direct band gap semiconductors with high luminous efficiency.The main contents and conclusions are as follows:（1）Based on the space-confined CVD method,the best growth factors of two-dimensionalα-Mn Se were obtained by comparing and analyzing the influence of temperature,distance between precursor Se and furnace center,gas flow and the ratio of precursors.The surface morphology and thickness of the prepared samples were characterized by optical microscope（OM）,SEM,and atomic force microscope（AFM）.The results confirmed that the size of the samples we obtained was as long as 120μm and the thickness was as thin as1.8 nm（only about two atomic layer）.（2）To explore the impact of different transfer methods on samples,we used Wet transfer（hydrofluoric acid as etching solution）,deionized water transfer and dry transfer method to transfer the prepared two-dimensionalα-Mn Se samples.The advantages and disadvantages of the above three methods were compared.（3）The composition of the sample was analyzed by energy dispersive spectroscopy（EDS）,X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）,Raman spectra（Raman）and other characterization methods.The synthesized material was confirmed to be a two-dimensionalα-Mn Se single crystal.Then,photoluminescence spectroscopy（PL）was further adopted to test its luminous characteristics.（4）A photodetector based on two-dimensional Mn Se was constructed.Its maximum responsivity was measured to be 120 A/W,the maximum external quantum efficiency was2.8x10⁴%,and the maximum detection rate was 7.05x10¹¹Jones.Compared with the performance of photodetectors based on other two-dimensional materials,our photodetectors based onα-Mn Se nanosheets have ultra-high optical response,excellent external quantum efficiency and excellent photo-detection rate.As a new type of two-dimensional semiconductor,two-dimensional Mn Se is expected to be applied to photoelectric devices.（5）The space-confined CVD method is extended to the preparation of non-layered two-dimensional Ga₂Se₃and an attempt has been made to introduce liquid metal Gallium（Ga）to assist the preparation of two-dimensional Ga₂Se₃.At present,we have initially obtained the non-layered two-dimensional Ga₂Se₃.Furthermore,Raman characterization was used to determine the composition of the sample,but the crystalline quality of the sample is still not ideal and the preparation parameters need to be further optimized.