Controllable Growth And Physical Properties Of Two-dimensional Gallium Selenide And Its Heterojunction

The remarkable properties of graphene have inspired great research interest in two-dimensional layered materials(2DLMs)with novel electronic and optical attributes.As a class of graphene-like 2DLMs,ultrathin group IIIA metal chalcogenide(metal=In,Ga;chalcogen=S,Se,Te)two-dimensional semiconductor materials have shown great potential in electronics and optoelectronics.Such materials with wide spectral response and flexible photodetectors have been developed.However,it is desired to prepare high-performance optoelectronic devices.In the follow-up research,there is still a need to develop new synthetic methods to obtain high-quality materials with large thickness,controllable thickness,high crystallinity and uniformity.In this work,we studied the preparation and physical properties of gallium selenide(Ga Se)and its heterojunction,focusing on the evolution of Ga Se morphology,controlled crystal growth mechanism,and the performance of Ga Se nanosheet-based photodetector devices.Some scientific research results in this paper are mainly reflected as follows:1.The large-size nanosheets were successfully prepared by vapor deposition,and the controllable preparation of the size and morphology of Ga Se nanosheets was achieved by controlling the crystal dynamics parameters.Morphology,thickness and composition of Ga Se nanosheets were analyzed by atomic force microscopy(AFM)and scanning electron microscopy(SEM).The results show that these nanosheets have good crystallinity and uniformity.In addition,the optical properties of Ga Se nanosheets were analyzed by transmission electron microscopy(TEM),Raman spectroscopy(Raman)and photoluminescence spectroscopy(PL),which further showed that the nanosheets have high crystal quality.This provides a material basis for the preparation of high-performance optoelectronic properties.2.Through the calculation of density functional theory and the dynamic Wulff structure theory,we explained the observed shape evolution of Ga Se nanosheets and proposed the growth process diagram.It was found that the bright micro-environment has an important determinant for the growth of Ga Se nanosheets.The growth process of the control material can be controlled by controlling the ratio of Ga/Se,thereby achieving the controlled growth of Ga Se crystals.3.Ga Se-based photodetectors are manufactured using photolithography techniques and electrode or sample transfer preparation methods.We tested the photoelectric detection performance of nanosheets with 405 nm as the light source.The results show that the device has excellent photoelectric performance,its responsivity is up to 3000 A/W,and the time response is less than 0.7 ms.4.A large area thin film heterojunction of Bi₂Se₃/Ga Se was prepared.The thickness uniformity and physical properties of the heterojunction morphology were analyzed by AFM and Raman,which showed that the large-area thin-film heterojunction had good uniformity and environmental stability.