Growth And Properties Of Doped Lithium Niobate Crystals And Aluminum Nitride Films

Inorganic non-metallic material plays an important role in the advanced technology as well as people's daily life.This paper conducted the research of inorganic non-metallic material in the application of nonlinear optics and the third generation semiconductor.Different methods were taken to grow the doped lithium niobate crystals and aluminum nitride thin films,and their structural properties were characterized.As a kind of nonlinear optical crystal,lithium niobate is an ideal frequency conversion crystal for quasi-parametric chirped pulse amplification(QPCPA)system,which has the characteristics of wide transmission range,high nonlinear coefficient and is easy to grow in large size.In QPCPA system,the conversion efficiency of ultra-short and ultra-strong pulse laser can be improved by absorbing idle light,transmitting pump light and signal light.In this paper,different concentrations of Pr ions were added to absorb the idle light at 1588nm,and different concentrations of Mg ions were added to improve the light damage threshold of doped lithium niobate crystals.At the same time,the structural characteristics,thermal properties and optical properties of doped lithium niobate crystals were also studied.It can be seen from the powder X-ray diffraction characterization,the doping ions have no effect on the crystal structure,and the segregation coefficient of Pr ion is close to 1,while that of Mg ions is low.It is found from Raman spectra that the Li/Nb ratio of doped lithium niobate crystals decreases obviously,which may be caused by the occupancy of the intrinsic defect of Mg element.The thermal conductivity of the doped crystals were calculated by the specific heat and thermal diffusion coefficient,which are greatly improved comparing with other QPCPA nonlinear crystals.The transmittance spectra and the Fourier transform infrared spectra of the grown crystals show that the transmittance of the doped crystals reached over 75%ranging from 1000 nm to 4355 nm apart from a strong absorption band around1588 nm.Moreover,the laser threshold of the crystal was measured,and results suggest that the threshold value of Pr³⁺(1 mol%)-Mg²⁺(5 mol%)co-doped Li Nb O₃crystal is as high as 1097.3 MW/cm²(@1064 nm,5 ns),which makes it suitable for ultra-short and ultra-strong laser system.Aluminium nitride is one of the representative semiconductor materials of the third generation.Aluminium nitride film has a wide range of applications in the fields of surface acoustic wave devices,photoelectric integrated circuits and ultraviolet detection.In this paper,metal organic chemical vapor deposition(MOCVD)technology was used for epitaxial growth of aluminum nitrite films on Si C substrates.Experiment was carried out on the structure design and growth parameter optimization of the films.The quality of the films was characterized by X-ray diffraction,atomic force microscopy,scanning electron microscopy and other testing methods respectively.(1)The quality of aluminum nitride film was optimized by using buffer layer structure.The low temperature MOCVD buffer layer and PEALD buffer layer of aluminum nitride were tried.The comparison results show that the crystallization quality of aluminum nitride epitaxial film on low temperature MOCVD buffer layer was higher than PEALD buffer.(2)On the basis of low temperature aluminum nitride buffer layer,it is found that the three-dimensional and two-dimensional growth of the film are influenced greatly by changing the growth temperature of buffer layer.(3)The effect of the precursor atomic surface mobility on the transverse and longitudinal growth trend of the film was studied by changing the precursor flow rate in the growth process(V/III ratio).The results show that low V/III ratio leads to the two-dimensional growth of AlN which improves the crystallization quality.