Synthesis And Color Center Research Of S(H) Doped Diamond Under High Pressure

Great achievements in research have been made for the elements nitrogen?N?and boron?B?in diamond.However,the elements sulfur?S?and hydrogen?H?less compared to N and B by researches.S has a much larger atomic radius than that of carbon?C?,especially because S is hardly incorporated into a diamond lattice.Recently,researchers found that a large gem diamond may be generated from the Fe-Ni-C-S melt in earth's deep mantle.There is still lack of evidence to certify the incorporation of S into the diamond lattice.H can also be found in the diamond lattice,and it can largely change the property of diamond when it is doped with other elements.Doping is an effective method for changing the physical and chemical property of diamond.The NV center was also found in synthesized S-doped diamond.It is reported that the single NV center is proven to be a promising system for solid state quantum information processing,nanoscale electromagnetic field sensing,plasmonics,and biolabeling.The typical way of creating the NV center was to irradiate the Ib-type diamond by electrons,protons,neutrons,ions,and gamma photons,and then resort it to HPHT treatment.Previous studies have not placed much emphasis on the effect of additives in the synthesis system for generating the NV center in a diamond lattice.Accordingly,it is significant for the synthesis diamond in the Fe-Ni-S?H?-C system.Besides,type Ia?containing aggregated N?diamonds make up about98%of natural diamonds and only 0.1%natural diamonds belong to type Ib?containing single substitutional N atoms?.One hypothesis suggested that the origin of natural diamonds was type Ib and then isolated C-center N soon aggregated into pairs of the nearest neighboring substitutional A-center N atoms?type IaA?.Annealing treatment is an effective method for a type Ib diamond changing into a type Ia diamond.HPHT annealing experiment is helpful for understanding the formation of natural diamonds.Based on the temperature gradient growth method,we successfully synthesized S?H?doped type IIa and type Ib single diamond crystals in a Fe-Ni-S?H?-C system by using a Chinese cubic-anvil high-pressure apparatus?CHPA?.The HPHT annealing research was conducted for the type Ib diamond synthesized in a Ni-based catalyst alloy,and the type Ia A diamond was successfully prepared under a lower pressure.To study the crystalline quality,content,distribution,and existence forms of impurity in larger single crystals diamond,the formation mechanism and rule of different center in HPHT annealing diamond lattice was clarified.The synthesized and annealed diamond will then be characterized by optical microscope?OM?,scanning electron microscope?SEM?,Raman spectra,Fourier transform infrared?FTIR?,X-ray photoelectron spectroscopy?XPS?,PL under room temperature or low temperature.The main content and achievements are as follows.1.It was discovered that the growth rate of the diamonds decreased according to synthesized type Ib diamond single crystal that grew by the{100}and{111}faces of seed crystal in a FeNi-S-C system.The color of the diamonds changed from yellow to light yellow with an increase in the S content.Compared to common type Ib diamonds synthesized in a FeNi-C system,the nitrogen concentration was higher in the synthesized diamonds when 0.1 wt.%S was added,but was lower when the amount of S was increased to 0.25 wt.%.Raman measurements indicated that the use of S had almost no effect on the diamond lattice structure.As a consequence,diamond crystals with a high-quality sp³structure were obtained.The photoluminescence?PL?spectra showed that the NV center were more likely to occur in diamond lattice growth along the{111}face.Compared to the NV^-center,the NV⁰ center could not be easily generated in the type Ib diamond lattice without the addition of S.Even if the NV⁰ and NV^-centers were simultaneously generated in the diamond lattice with the addition of 0.25 wt.%S,the intensity was higher for the NV^-peak than for the NV⁰ peak.2.The effect of S was investigated for the growth and property of diamond single crystal because of the synthesized type IIa diamond in a FeNi-S-C system.It was found that the synthetic diamond is mainly composed of the{111}faces and the growth rate decreases because of the addition of S in the synthesis system.In addition,the color of our produced diamond changed from white to light brown,and the shape of the diamond changed from Cub-Octahedron to Octahedron with an addition of S in the FeNi-C system.Furthermore,it was observed that a number of defects,such as stratiform defects,craters,and inverted pyramid defects,appeared on the surfaces of diamonds induced by the additive of S.The FTIR results show that the obtained diamond crystals are IIa-type diamonds,containing less than 1 ppm nitrogen.XPS measurement indicates that S was successfully incorporated into our produced diamond lattice in the S-C and C-S-O forms.Raman spectra revealed that the as-growth S-doped IIa-type diamond single crystals possess a high-quality sp³ structure.Photoluminescence?PL?spectra demonstrated that nitrogen-vacancy is formed during diamond growth and the intensity was higher for the NV⁰ peak than for the NV^-peak.3.When the content of CH₄N₂S in the synthesized system changed from 0.1 wt.%to0.15 wt.%,the growth rate of type Ib diamond is slowed.The H-related peak was founded in the FTIR spectra of synthesized type Ib and type IIa diamond,signifying that H was successfully into diamond lattice.4.The formation mechanism and rule of different center in type Ib diamond under HPHT annealing experiment was investigated.Under the lower pressure of 2.5 GPa,the color of the diamond changes from yellow to light yellow and the nitrogen?N?state changes from the isolate C-center to the aggregated A-center with the annealing temperature increasing.The NV⁰ center was detected when the annealing temperature was under1840°C but was undetected when the temperature was up to 1920°C.The NV^-center was more stable than the NV⁰ center under the annealing temperature of 1990°C.When the annealing temperature was up to the 1990°C,NE8 center appeared in diamond lattice.In addition,it could restrict the formation A-center N but was barely effective for the formation of NV^-in diamond lattice when the annealing pressure changed from 2.5 GPa to 5 GPa.Our experiment results could also be helpful for further understanding the formation of different centers in diamond lattice and provide data for distinguishing the annealed synthesized diamond from natural diamonds in jewelry market.