Hydrothermal Synthesis,Characterization And Photoluminescence Research Of Phase-pure And Cr-doped ?-Ga₂O₃ Nanostructured Materials

Gallium oxide(Ga2O3)is an important wide-bandgap semiconductor material with many excellent properties,which is widely used in many fields such as luminescence,gas sensing and bioimaging,etc.Because of its broad application prospects,it has attracted wide attention from researchers at home and abroad in recent years.Due to the simplicity and low energy consumption,the hydrothermal method has great advantages in synthesizing Ga2O3.However,there are few studies on the synthesis of gallium oxide by hydrothermal method.The main content of this paper is to synthesize phase-pure ?-Ga2O3 powder by hydrothermal method using Ga(NO3)3 as the gallium source,and doping it with trace Cr.Firstly,the GaOOH precursor was synthesized at a lower temperature.Subsequently,?-Ga2O3 submicron particles could be obtained after high temperature calcination using GaOOH as precursor.The ?-Ga2O3 was characterized and analyzed in detail.The phase and element composition were characterized by XRD,EDS and XPS;the reaction process of calcined GaOOH was analyzed by TG-DSC;the morphology and structure of ?-Ga2O3 were characterized by SEM and TEM;the lattice vibration of ?-Ga2O3 was studied by Infrared and Raman;the optical properties of the prepared ?-Ga2O3 powder were tested by photoluminescence.The effects of different hydrothermal conditions on the structure and properties of ?-Ga2O3 were investigated.1)Ammonia was used as precipitant:the samples obtained under different hydrothermal temperature conditions have different degrees of structural collapse after calcination;the ?-Ga2O3 particles with good crystallinity can be formed after sufficient time ageing;the pH value has a great influence on the morphology of the final ?-Ga2O3 particles.2)Urea was used as precipitant:?-Ga2O3 with rod-like morphology can be obtained;as the hydrothermal time and temperature increases,the length and width of the ?-Ga2O3 rod increases;in addition,cluster-like?-Ga2O3 micron flowers can be observed in the sample.3)NaOH was used as precipitant:the amount of surfactant added has a great influence on the morphology of the final ?-Ga2O3 particles;nano-sized ?-Ga2O3 particles can be synthesized by ethylene glycol-assisted hydrothermal method.The infrared vibration modes of ?-Ga2O3 are mainly in the range of 400?1000 cm-1.The Raman active mode can be divided into three groups(high frequency,medium frequency and low frequency),which are assigned to Ga-O4 tetrahedron,Ga-O6 octahedron and tetrahedron-octahedron chains respectively.The excitation wavelength of phase-pure ?-Ga2O3 were measured at about 250 nm,which is consistent with the theoretical value.The emission peaks are located in the blue-violet region(350?450 nm)and ultraviolet region due to the combination of an electron on donor formed by oxygen vacancies and a hole on an acceptor formed by gallium vacancies or gallium-oxygen vacancy pair,and the recombination of self-trapped excitons,respectively.The ?-Ga2O3:Cr has two broad excitation bands in the range of 400?500 nm(4A2-4T2(te2))and 550?600 nm(4A2-4T2(t2e)).Under excition of 450 nm,it has a wide emission band in the near-infrared region of 650?800 nm,which is due to the energy level transition(4T2-4A2)of Cr.