| Nanomaterials have been the hot point and have great potential in the research ofmaterial science and device applications, due to its excellent physical and chemicalperformance. In2Se3nanomaterials have been extensive studied, because of itsapplications in phase change memory, photodetector, solar cells and lithium ionicbattery. The research purposes of this thesis are to explore the synthetic conditions ofhigh quality In2Se3nanomaterials, do systematic characterization and photoelectricalapplication of the as-synthesized In2Se3nanomaterials. The detailed content asfollowing:1. High quality In2Se3nanowires and nanowires array have been synthesized by thetypical physical thermal vapor deposition method using gold nanoparticals as catalystand In2Se3powder as source. Through controlling the synthetic condition, the influenceof these factors on the synthesis of In2Se3nanowires have been systematic studiedwhich contain temperature, the flow rate of carrier gas, pressure, catalyst, growth timeand the positioned method of substrate. The morphology, chemical composition,crystal structure and optical performance of as-synthesized In2Se3nanowires have beenresearched systematically using scanning electron microscopy (SEM), X-ray powderdiffraction (XRD), high resolution transmisson electron microscopy (HRTEM),ultraviolet and visible spectrophotometer and so on. The research results indicated thatthe growth mechanism of In2Se3nanowire is VLS and the main growth direction is[1120], the crystalline structure of as-grown In2Se3nanowire is-phase hexagonalstructure, and it has wide absorbtion ranges from near ultroviolet light to visible light.2. The photodetector devices based on single In2Se3nanowire and In2Se3nanowiresthin films have been fabricated. It shows high and stable photoresponse performance ina wide wavelength (254nm–800nm) and work temperature ranges (7K–300K). And italso shows high photoresponsivity (150A/W) and external quantum efficiency (37000%), under the tested condtion of500nm and5V. In the meantime,photodetectors also show that the photocurrent has a linear relationship with theilluminated light intensity; this indicated that the work mode of these photodetectors istypical light-dependent resistant mode. And the photodetectors based on In2Se3nanowire thin films also show stable photoresponse performance.3. Single crystalline In2Se3nanosheets have been synthesized by physical thermalvapor deposition method through controlled the pressure, temperature and flow rate ofcarrier gas. The main thickness of the In2Se3nanosheets is about20nm-40nm andwhich has a minimum thickness about4nm. From the measurement of SEM and TEM,the chemical composition of as synthesized products is In and Se (In:Se=2:3) and thecrystalline structure is-phase hexagonal structure. The growth mechanism of theIn2Se3nanosheet is epitaxial growth. And from the Raman measurement, the peak ofA1(LO+TO) mode have a small shift as the thickness of the In2Se3nanosheet decrease，which indicated it have significant meaning in research work of Quantum effect abouttwo-dimensional materials.4. Devices based on single In2Se3nanosheet have been successfully fabricated, andthe photoelectric performance of these devices has been systematic studied. From theelectrical measurement of two-terminal In2Se3nanosheets devices and Conductive-AFMmeasurement of In2Se3nanosheets, they show distinguished anisotropic electricalproperties and photoresponse performance. In the measurement of In2Se3nanosheetsFET devices, they show typical n-typed semiconductor properties and the moblilty isabout0.12cm2V-1s-1. And in the photoresponse measurement, under5V appliedvoltage and5mW/cm2light illumination, the photo-responsitivity is about7.5A/W andthe On/Off ratio is about15times, also in the FET device performance, in negative gatevoltage, the On/Off ratio is about10times higher than in the zero gate voltage, underthe same measurement condition. For photoresponse test of the two-terminal devicesbased on In2Se3nanosheets, when under different light intensities, the light can play arole as the gate voltage, which implys that In2Se3nanosheets can be made asphototransistor. Finally some devices of In2Se3nanosheets which have two asymmetriccontact area between the electrode and In2Se3nanosheet, also show unique photovoltaicperformance, under the100mW/cm2light illumination, the short circuit current andopen circuit voltage are about50mV and10pA, the efficiency is about0.0015%. According the aboved research results, the In2Se3nanomaterials will show greatpotential in applications of optoelectronics. |
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