Synthesis Of High-quality Magnesium Nitride Films By Reactive Magnetron Sputtering

Magnesium nitride?Mg₃N₂?is a typical alkaline earth metal nitride.The optical bandgap measured by experiments is more than 2.5 eV.It is also one of the third generation semiconductors in a broad sense.Mg₃N₂ also has potential applications in the field of optoelectronic functional materials and devices.However,limited by the preparation process,Mg₃N₂ currently produced in industry is a yellow-green powder,which contains some Mg or MgO impurities,the crystalline quality is relatively poor,and the stability is not good and easy to hydrolyze.In industry,Mg₃N₂ is widely used as a sintering aid or catalyst for the preparation of special ceramic materials,and is one of the common high-efficiency hydrogen storage materials.However,there are few researches on Mg₃N₂ as a photoelectric functional material.In this paper,a new method of reactive magnetron sputtering is used to prepare high-quality Mg₃N₂ thin films,and the applications of Mg₃N₂ thin films in the field of photoelectric detection were preliminarily explored.The main research results are as follows:1.A new method for preparing Mg₃N₂ thin films was proposed.Using high-purity magnesium?99.95%?as a target,high-purity nitrogen?99.9995%?as the working gas,high-quality Mg₃N₂ polycrystalline thin films were prepared by the reactive rf magnetron sputtering technology.The method has the advantages of simple operation,low cost,pollution-free and good repeatability.2.The effects of sputtering power,substrate temperature,working atmosphere and other process parameters on the quality of Mg₃N₂ thin films were studied respectively.The optimized process parameters included sputtering power of 200W,substrate temperature of 500?,and working atmosphere of pure nitrogen.Using these optimized parameters,high-quality?-Mg₃N₂ thin films were deposited on Si and sapphire substrate.The lattice constant of Mg₃N₂ is about 9.973?.The full width at half maximum of XRD diffraction peak of the Mg₃N₂?222?crystal plane is about 0.138°,the grain size of Mg₃N₂ is about 59 nm.The intense Raman characteristic peak locates at about 380 cm^-1,which is due to symmetrically streching of Mg-N bonds,and the full width at half maximum is only 8.3 cm^-1.3.The absorption and reflection spectra of Mg₃N₂ thin films were measured,which proved that Mg₃N₂ has a direct bandgap,and the optical bandgap is about 2.6 eV.The intrinsic absorption edge of the Mg₃N₂ thin film was about 480 nm,and the absorption coefficient was larger than10⁴cm^-1near the absorption edge.4.Using a buried MSM electrode structure and BN as the protective layer of Mg₃N₂ thin films,a prototype of Mg₃N₂ photodetector was prepared.The wavelength response range of this detector is mainly in the range of 300?500 nm,the peak response wavelength is about 380 nm,under 7V bias,the responsivity is about 2.0 mA/W,and the switching ratio is about 45.