| Recently,2D layered materials have attracted increasing attention and enthusiasm because of their exceptional electronic,optical and mechanical properties,such as graphene,transition metal dichalcogenides(TMDs)black phosphorus,etc.Orthorhombic SiP(o-SiP)is a novel 2D layered crystal.The growth and properties of novel orthorhombic SiP(o-SiP)are not only important to extend our current knowledge of 2D materials,but also may significant impact on future electronic technologies.In this paper,large-sized bulk o-SiP single crystals have been successfully grown by seeded flux method.The basic physical properties and in-plane anisotropy were researched in detail.Main contents and conclusions in this dissertation are as follows:?.Controllable flux growth and optic-electric properties of bulk o-SiP crystals.Large-sized bulk o-SiP single crystals have been grown successfully by flux method for the first time.The size and morphology of o-SiP crystals can be controlled by tuning the cooling rate.The energy band gap of bulk o-SiP is determined to be 1.71 eV and its mobility is 2.034 ×103 cm2·V-1·s-1 which is ten-fold of MoS2.DSC/TGA characterization indicates that o-SiP is thermodynamically stable up to 1045 ?.Fast laser responses indicate that o-SiP is a sensitive photodetector.Our experimental results indicated that o-SiP might be a promising 2D material for electronics and optoelectronics applications.?.Mechanical exfoliation few-layer o-SiP nanosheets with tunable band gap.Highly quality o-SiP nanosheets with large area were obtained by mechanical exfoliation technique with self-made o-SiP crystals.Morphology and microstructure of nanosheets were investigated by SEM and TEM.DFT calculations indicates that o-SiP,an indirect band gap material in bulk form,becomes a direct band gap semiconductor when thinned to a monolayer.?.Rearsch on in-plane anisotropy of o-SiP.We identify all the experimental Raman modes of o-SiP based on DFT calculation for the first time.Meanwhile,the polarized Raman spectra distinctly reveal the anisotropy of Raman intensity.As a simple and nondestructive method for identifying crystalline orientation,polarized Raman spectrum is of great benefit for the research on anisotropy of o-SiP.O-SiP based photodetectors show high photosensitivity,allowing them to act as high-quality photosensitive switches.More importantly,the results indicate high in-plane anisotropic photoresponse along a-and b-axis.A notably anisotropic on/off switching ratio indicates that o-SiP is a promising 2D material candidate for future optoelectronic applications,especially when the anisotropy is desirable.In addition,our results highlight the structural and optoelectronic anisotropy of o-SiP.It will provide useful guidelines for exploration of applications in electronic,optoelectronic devices based on IV-V group 2D layered semiconductors.?.Growth of CdSiP2 crystal.Ternary silicon diphosphide compound CdSiP2(CSP)crystal is an important mid-infrared non-linear optical crystal due to large nonlinear coefficient and high thermal conductivity.In addition,it can be pumped by commercially available laser such as Nd:YAG operating at wavelength around 1 ?m without TPA.However,it is difficult to grow large-sized,crack-free crystals directly from melt mainly due to the high melting point(1133 ?)and extremely high dissociation pressures at their melting temperature(22 atm at 1133 ?).This severely limits volume production and applications.Using experience growing o-SiP crystal,CSP crystals were grown by flux method to solve the explosion of quartz tube.Meanwhile,o-SiP crystals were grown by vertical-Bridgman method and try to help the growth of CSP crystal in the future. |
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