Synthesis And Photoelectric Properties Of Novel 2D Semiconductor Materials And Devices

Whenever the advent of a new generation of CPU,people will be keen to discuss it uses much of micron or nanometer by semiconductor technology process.Every time the progress of process technology for chip manufacturing industry produced significant influence,and deduce a classic legend.With semiconductor industry technology progress,human's demand is higher and higher for the performance of small volume,excellent semiconductor devices.A two-dimensional crystal materials because of its thin atoms geometric structure,unique electrical and optical properties has attracted great interest.As the discovery of the most typical two-dimensional layered materials firstly,graphene has excellent electronic,mechanical and optical properties,thus caused a research upsurge,is considered the most likely to replace silicon semiconductor materials.However,as electronic material,zero band gap is the lack of its graphene.Despite efforts by forming belt or nano modified to make graphene synthesis of band gap,band gap value is less than 360 meV.This is reamin could not reach the requirements of conversion rate and will lead to great attenuation of carrier mobility.Therefore,materials experts from all over the world have been exploring other two-dimensional layered materials,especially looking for improve reaction rate,conversion rate and other atomic layer semiconductor photoelectric performance.After scientists explore unceasingly,more and more two-dimensional material was found,these materials have their own characteristics,the transmittance of graphene,the direct band gap of molybdenum disulfide,the insulation of boron nitride,the semiconductor characteristics of black phosphate.These features can make 2 d materials play to their respective specialty materials in different fields,but these materials are remain facing the same trouble.In this paper,we reports about we have prepared a variety of semiconductor nanostructures film,including the WO3,VS2,SnS2 thin film materials by the traditional chemical vapor deposition and hydrothermal method and study the morphology,composition and structure.We also have prepared the many semiconductor devices using photolithography,evaporation and other semiconductor technology route,such as:crystal field effect tube,detectors,lithium battery,optical switch,etc.and using semiconductor parameter meter to test the electrical properties of nano device;In this paper,several research results are as follows:(1)Chemical vapor deposition method is used to synthesize high quality thin layers of W03 nanometer film,nanometer thickness 12 nm(16 layers).W03 is a kind of important high heat stability and chemical stability of broadband gap(?3.3 eV)semiconductor materials.By lithography and electron beam deposition and stripping process,we prepared a uv-photodetectors device,whose channel width of 13?m.And we studied the electrical characteristics of this device by the wavelength of 365 nm monochromatic light vertical irradiation.The experimental results show that this device has high sensitivity excellent photoelectric properties,spectral responsivity for 293 A/W,response time is about 40 ms,switch rate more than 2000,the external quantum efficiency is 997%.And the device performance is stable,and reversible.These results indicate that the two-dimensional WO3 nanometer film as the photoelectric sensor has a good application prospect,also in order to make the layered multi-function of semiconductor materials and high-performance photo detector to pave the way.(2)The flower-like VS2 nanosheets were synthesized by a one-step solvothermal method.The X-ray diffraction,Raman,SEM,and TEM studies have been shown the growth mechanism of VS2 flowers in detail.These experimental results indicate that the reaction temperature and time have the direct effect in the formation of VS2 nanosheets.As anode material for Li-ion batteries,the VS2 nanosheets exhibited an initial discharge and charge capacity is 195.4 and 90.6 mAh/g at current density of 200mA/g.High Coulombic efficiency over 98%and improved rate capacity were achieved for the VS2 nanosheets.So our results suggest that the VS2 nanosheets can be utilized as a promising anode material for Li-ion batteries with high power density and fast charge/discharge rates.In addition,experimental results show that VS2 nanostructures have ferromagnetism in low temperature.The Curie temperature Tcstronglydepends on the thicknesses of the samples,and Tcof VS2 nano-flowers and ultrathin VS2 nanosheets are 10 K and 72 K respectively.The experimental results are explained theoretically by first-principles total energy calculations based on the density functional theory.This work might offer a new route to explore the spintronics applications in primitive ultrathin VS2 nanosheets without doping any transition metal atoms.(3)Synthetic SnS2 powder by chemical vapor deposition method,and then,by using the method of mechanical stripping can be obtained from a mass of layered SnS2 SnS2 thin layer,the thickness of the nanosheet is 36 nm.We characterized the film crystal quality by TEM and Raman spectroscopy.The data reality the SnS2 thin film for monoclinic system,crystal quality is good.Based on a thin layer of SnS2 nano film,we using the gold mask mobile technology manufactured high photosensitive field effect transistor,channel width is 20 ?m.By the monochromatic light(530 nm)vertical irradiation on the device,we tested the device performance of optoelectronics,with up to 103 switch rate,light responsivity and the external quantum efficiency(EQE)reached 8.5 A/W and 1.2 x 103%respectively.Finally,in order to explore the more basic physical properties of SnS2,we adopt spin-polarized density functional theory(DFT),the band structure of two-dimensional materials and local density of states of SnS2 are studied by using VASP.Therefore,the excellent properties of 2D SnS2 films will have broad prospect of application in functional optoelectronic devices or systems(4)Pattern sapphire substrate(PSS)as the GaN based LED epitaxial substrate have been widely used in recent years.Dry etching technique as a method for preparing PSS generally used in the world and become the research hotspot of PSS.In this paper,using inductively coupled plasma(ICP)etching on the sapphire substrate covered by the photoresist mask,we studied the effects of different process parameters on the pattern size,morphology after ICP etching,and optical properties of LED chips,which is epi-InGaN/GaN multiple-quantum well on these different morphology PSS.Here we show that the Light Output and the FWHM of Donmiant Wave using pyramid type PSS is better than dome type.We think that the pyramid type PSS can be more effective to increase the light extraction efficiency of LED and improve the crystal quality,because that would be reduced the lattice mismatch defect when the GaN epi-layer grown.In addition,we make the LED chips by AIN films base PSS.The forward voltage and dominant wavelength of the LED chips is no different with brfore.And the brightness and ESD yield advantage obviously,respectively 4%,3%;and the epitaxial growth time reduced by almost 20%.