Study On Growth Of Single Crystal Boron Nitride By Flux Method

Hexagonal boron nitride（h-BN）,as a new type of ultra wide bandgap semiconductor,has a single-layer h-BN bandgap of over 6.0 e V and excellent physical and chemical properties such as high thermal stability,high mechanical strength,high thermal conductivity,and low dielectric constant.h-BN has high luminous efficiency in the ultraviolet range（204 nm-218 nm）and is an excellent material choice for deep ultraviolet devices such as ultraviolet light-emitting diodes and detectors.At present,chemical vapor deposition or physical vapor deposition can be used to grow h-BN,but the crystal thickness of the obtained h-BN is only at the nanoscale,or there is a problem of poor crystal quality.Therefore,the preparation of large size,high-quality h-BN single crystal has become a major difficulty.The main problems with the flux method as a method for h-BN single crystal growth are:the selection of flux system needs further exploration and exploration;Exploration of optimal crystal growth conditions and research on material properties.Therefore,this article uses the flux method to grow h-BN single crystals under atmospheric pressure and high temperature,using metal and alkali/alkaline earth metal ions,and a quaternary alloy system as the flux.The main research contents of this paper are as follows:（1）Explore the flux system and single crystal peeling method,select appropriate crucibles,temperature,and the effect of carbon addition on single crystal growth.（2）Conduct comparative experiments on single crystal growth between metal and alkali/alkaline earth metal systems(Fe and Ba²⁺,Ca²⁺,Li⁺;Ni and Li⁺)and commonly used binary systems（Cu-Cr,Ni-Cr,and Fe-Cr systems）.First single crystal growth with a size exceeding 400μm in Ni-Li⁺systems.The Raman half width at half height is only7.78 cm^-1,providing a new research direction for the subsequent growth of h-BN single crystals.（3）Conduct single crystal growth experiments on quaternary 50wt%Fe-50wt%（Ni+Mn+Cr）and 50wt%Ni-50wt%（Fe+Mn+Cr）systems.By characterization and comparative analysis,the latter system is superior,with a maximum single crystal size of6 mm and an average thickness of 52.77μm。（4）Explore the effect of holding time on the growth of h-BN single crystals,briefly describe the phenomenon of metal monocrystallization and"cracks",and discuss the growth mechanism.