Controlled Synthesis Of Novel Indium Oxide Nanomaterials And Their Photoelectric Properties

Indium oxide（In₂O₃）,an n-type semiconductor material,has been widely used in many fields due to its wide band gap,low resistance,good catalytic properties,high surface-to-volume ratio,high electrical conductivity,low electron affinity,high chemical inertness,high optical transparency and easily controllable morphology,making it one of the most popular materials for contemporary materials science research.However,its high work function（～5 e V）and wide forbidden band width（3.6 e V）make it a great challenge for applications such as field emission.In this thesis,new indium oxide nanostructures have been prepared to investigate the field emission effects of indium oxide nanomaterials,and indium oxide nanorod-flowers with low turn-on electric field,high field enhancement factor and high emission current stability have been designed and prepared.In addition,the effect of the distance between two flat plates on the field emission performance parameters in the field emission test device was investigated,and the monotonicity of the turn-on electric field and field enhancement factor with distance was found.（1）In this work,indium hydroxide nanomaterials with various morphologies were synthesised by a simple one-step hydrothermal method using indium chloride,urea and glucose as reactants,followed by a high-temperature calcination method to obtain new structural indium oxide nanomaterials.The morphology,structure and band structure of the samples were characterised by X-ray diffraction（XRD）,swept surface electron microscopy（SEM and EDS）,transmission electron microscopy（TEM）,Raman spectroscopy and X-ray photoelectron spectroscopy（XPS）,and the crystal growth mechanism was investigated.It was found that the morphology of indium oxide nanomaterials was controlled by the addition of urea and glucose,and four morphologies of indium oxide nanocubes,nano-rods,nanomaces and nanorod-flowers were obtained.（2）By systematically studying the morphology,structure and field emission properties of the new indium oxide nanomaterials,it is hypothesised that the indium oxide nanorods have better field emission properties than the nanorods and nanorod-flowers when used as field emission cathode emitting materials.The lower turn-on electric field（0.97 V/μm）and the higher field enhancement factor（1053）depend mainly on the smaller radius of the emitting tip,it is means that the higher aspect ratio,and the crystallinity of materials also has an effect on it.A reasonable explanation is also given for the non-uniform field enhancement factor that appears in the experimental data.（3）The field emission effect is a phenomenon that strongly depends on the distance between the emission tip and the electric field source.The effect of the distance between the two plates in the field emission test device on the turn-on electric field and the field enhancement factor of the field emission effect parameters was investigated,based on the In₂O₃nanorod-flowers structure with the best field emission performance among the four indium oxide morphologies prepared.From the measured data we found that the turn-on electric field increases monotonically with distance as the separation distance between the cathode and anode plates increases gradually in the range 300μm<d<1200μm,while the field enhancement factorβhas a non-monotonic correlation with the separation distance d.We explain the appearance of this phenomenon in terms of the effect that the presence of the surface state of the cathode-emitting material affects the field emission performance.This work provides new ideas for the controlled synthesis of nanomaterials with good field emission properties.（4）The novel indium oxide nanostructures possess good photoluminescence properties,with the strongest near-sideband emission peaks at 468 nm,which may be of use in blue light emission;at the same time,the indium oxide nanorod-flowers exhibit high UV absorption in the band from340 nm to 380 nm.