Controllable Preparation And Performance Investigation Of The 2D Tin-based Sulfides Semiconductor Nanosheets

In recent years,two-dimensional（2D）tin-based sulfides semiconductor materials,becoming a very important class of 2D sulfides semiconductor materials due to their low cost,earth-abundance,environmentally friendly characteristics and intriguing electronic and optical properties,have a wide range of applications in field-effect transistors,sensors,photovoltaics,thermoelectric,photodetectors and flexible electronic devices.Among them,SnE（E=S,Se）are two typical 2D tin-based semiconductor layer materials.They interact with each other through covalent bonding and through van der Waals forces between layers.However,due to the large electron distribution and electron coupling of the lone pair of Snatoms between adjacent layers,the inter-layer interaction forces are strong,which makes the growth of single-layer or even few-layer 2D materials is an important challenge.Furthermore,the band gap is a very important parameter for semiconductor materials,which determines their potential application in optics and electronics.At present,doping is an effective way to controlthe band gap of semiconductor material,however,there is no suitable way to be found to dope SnE 2D materials.Based on this,this paper systematically investigates how to grow ultra-thin SnS nanosheets and how to effectively dope SnE nanosheets by the rapid vapor deposition method.The SnS nanosheets with a minimum thickness of two layers were grown using the S-rich atmosphere in SnS precursor during the vapor deposition process,and a mechanism with passivation effects of S on the SnS surface was proposed.Se doped SnS nanosheets or a S doped SnSe nanosheets were successfully synthesized by creating Se-rich atmosphere in SnS precursor or S-rich atmosphere in SnSe precursor,indicating that different sulfides elements can dope 2D tin-based sulfides semiconductor materials.The main contents are demonstrated below.（1）Ultra-thin SnS nanosheets were successfully grown by rapid physical vapor deposition（r PVD）method with SnS powder as precursor and sulfur powder as passivator and the related properties were successfully investigated.In the growth process of ultra-thin SnS nanosheets,the Sulfur powder was used to create a S-rich atmosphere,so that the upper surface of SnS nanosheet adsorbs excess sulfur atoms,and a layer of SnS₂ is generated on its upper surface,which blocks the vertical connection between the SnS layers,inhibits its longitudinal growth,and finally grows SnS nanosheet with only two layers in thickness.The results show that the same sulfides element in 2D tin-based sulfides semiconductor materials has the passivation effect,which may provides a new idea for the growth of ultra-thin 2D sulfides semiconductor materials.（2）The Se elements is able to be successfully doped into SnS to form Se doped SnS nanosheets by adding Se vapor in SnS precursor using the rapid chemical vapor deposition method.The Se element is observed in the sample characterized by the X-ray photoelectron spectroscopy（XPS）.The vibrational mode of the Sn-Se bond is present further characterized by the Raman spectroscopy.The diffraction peak positions of the XRD pattern shifts to a small angle,resulting from fact that the lattice parameters of the doped product become larger,which indicates that the Se atoms have successfully replaced some of the S atoms.The SnS:Se nanosheets were successfully grew by adding Se vapor in the growth process based on the triumphantly growth of SnS nanosheets.The results show that SnS can be successfully doped in Se-rich atmosphere.（3）S-doped SnSe（SnSe:S）nanosheets were successfully grown by introducing sulfur vapor into the growth source of SnS at high temperature.The results showed that the SnSe:S nanosheets became the circular shape compared with the quadrilateral structure of SnSe nanosheets.There was a strong vibrational mode of Sn-Se bond except the vibrational mode of Sn-S bond in the Raman spectroscopy.The diffraction peak positions of the XRD pattern shifts to a large angle compared to pure SnSe nanosheets,resulting from fact that the lattice parameters of the doped product become smaller,which indicates that the Se atoms have successfully replaced some of the S atoms.The results further show that different sulfides vapor has doping effect in the growth process of 2D tin-based sulfides semiconductor materials,which may provide a guidance for the growth of other doped 2D sulfides semiconductor materials.