Analysis And Formation Mechanism Of Internal Defects In Blue Diamonds

Due to their rarity and preciousness,blue diamond remain a symbol of wealth and prestige to this day,and it has repeatedly appeared in the world's auctions and sold at amazing prices.In addition to their appeal as gemstones,blue diamond has attracted much attention in the field of materials research because of its remarkable physical properties.As we all know,diamond is the hardest material know at present,with the highest thermal conductivity,the lowest compression rate,high chemical inertia and other excellent properties.Combined with the p-type semiconductor properties,the researchers believe that blue diamonds are likely to be the semiconductor material for the next generation of high-frequency,high-power and high-temperature electronic devices.So blue diamonds are playing an increasingly important role in materials science.A large number of studies have proved that the blue diamond show their color due to the internal doped boron,and the electrical properties of the blue diamond are mainly determined by its internal defects and the concentration of boron concentration.However,due to the rarity of the blue diamond,the research about the defects and boron content of blue diamonds is still facing great difficulties.In this paper,Raman spectroscopy was used to calibrate the boron concentration in the blue diamond.In addition we reveals the natural blue diamond internal real impurity defects by testing blue diamond.Meanwhile,high-temperature and high-pressure(HPHT)technology was used to analyze the defects of the blue diamond and study their formation mechanism.Firstly,impurity analysis of blue diamonds with different boron concentrations was carried out by Raman spectroscopy.Raman detection in the range of 300-1800 cm^-1 were firstly conducted.The special Raman patterns were found to include Raman peaks of both high boron content and low boron content samples.Then,ultra-low frequency Raman test in the range of-100-100 cm^-1 were carried out on the samples at normal temperature in turn.We found a special shoulder near 12.1 cm^-1 in the spectra of blue diamond,which is related to the Raman electron effect,and this peak gradually increased with higher boron concentration.We also accomplished ultra-low wavenumber Raman test at different temperatures by liquid nitrogen cooling.The peak near 12.1 cm^-1 exhibited a ascending tend with the lower temperature.These changes were analyzed and formula fitting was carried out on the collected data.A new method of calibrating boron concentration was successfully proposed.Our results show that Raman spectroscopy can be used as a nondestructive method to accurately calibrate boron concentration in diamond.Secondly,we successfully revealed that the real impurity defect in natural blue diamond is boron oxygen compound defect,rather than single boron atom,by testing the types and contents of internal elements in natural blue diamond and synthetic blue diamond.In addition,we selected representative blue diamonds with different boron concentrations to adjust the boron oxygen defects inside the blue diamonds and improve their electrical properties through annealing treatment.Representative blue diamonds with different boron concentrations were selected for annealing treatment,so that the defects in the diamond could be balanced again and the electrical properties of the blue diamonds could be improved.We employed the vacuum furnace the large volume press for high temperature and HPHT annealing respectively.After treatment,the samples were tested and analyzed by Raman spectroscopy,physical property measurement system and Hall test system.The main objective of this work is to improve the crystal quality and electrical conductivity of the blue diamond by improving the internal defects of the blue diamond.