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In this paper, Ge-doped large single crystal diamond was synthesized under high pressure and high temperature (HPHT) conditions in NiMnCo-C and NiMnCo-Ti-C systems. The effects of Ge additives on the diamond morphology, nitrogen impurity content, and internal inclusions were investigated, and the interaction mechanism among germanium (Ge), nitrogen (N), and titanium (Ti) during the diamond growth process was discussed. The results show that the number of inclusions in diamond increase with increases in Ge addition in both systems. The N content of diamond grown in NiMnCo-C systems decreases with increases in Ge addition. However, Ge can more easily be doped into the diamond in a NiMnCo-Ti-C growth system. The experimental results show that the N can inhibit the amount of Ge entering the diamond lattice under HPHT conditions. When Ti was introduced into the system, it effectively removed N by combining with it, such that more Ge atoms could enter the diamond lattice. • The Ge-doped diamonds large single crystal were synthesized in the NiMnCo-Ti-C systems. • The addition of Ge leads to the decrease of nitrogen content in diamond and the intensity of NV− center. • The introduction of Ti makes it easier for Ge atoms to be incorporated into diamond lattice. • Ge atoms enter the diamond lattice and bond with C, N and O atoms respectively. [ABSTRACT FROM AUTHOR]

Abstract Diamond crystals were successfully synthesized in a NiMnCo-C system by adding Malonic acid dihydrazide (C 3 H 8 N 4 O 2) as an organic additive. The synthesized conditions in a series of experiments were about at 1300 °C–1400 °C and 6.0 GPa–7.0 GPa. The color, morphology, and inclusions of the synthetic diamond crystals were characterized by optical microscopy, Fourier transform infrared (FTIR) spectroscope and Raman spectroscope, respectively. The color of the synthesized diamonds changes from light yellow to green with increasing amounts of C 3 H 8 N 4 O 2. The morphology of the synthesized diamonds exhibited triangular shape with abundant {111} faces. The FTIR spectra indicated that the nitrogen concentration increased whereas the hydrogen and oxygen concentration decreased with increasing concentration of the C 3 H 8 N 4 O 2 additive. The Raman peak positions exhibited a systematic downshift with increasing amounts of C 3 H 8 N 4 O 2 additive. According to the synthesized resultant, with increased the content of the C 3 H 8 N 4 O 2 additive, the quality of synthesized diamond gets worse. It is interesting that the diamond content more nitrogen and less hydrogen and oxygen with increasing the C 3 H 8 N 4 O 2 additive. By studying the effects of nitrogen, hydrogen and oxygen coexistence on the synthesis of diamond, it is would to speculate that the natural diamond nucleation and growth environment may be content more nitrogen source and less hydrogen and oxygen. Highlights • (C 3 H 8 N 4 O 2) was selected as an organic additive to synthesized diamond in the NiMnCo-C system under HPHT • Diamonds grown in the NiMnCo-C 3 H 8 N 4 O 2 -C system were characterized with FTIR and Raman techniques. • H-N-O co-exist in synthesized environment of diamond growth provide some reference data to study the nature diamond. [ABSTRACT FROM AUTHOR]

The influence of Fe 2 O 3 addition on the growth characteristics of synthetic diamonds under high-temperature and high-pressure conditions was systematically investigated in this work. Utilizing Fe 2 O 3 as an oxygen source within the Fe-Ni-C-O system, oxygen-containing diamond single crystals were synthesized. The role of the oxygen atoms during the growth of large-sized diamonds with the {111} face as the growth surface was also analyzed. In addition, the morphology, growth rate, internal nitrogen content, and crystal quality of the crystals were examined. From our analysis, it was demonstrated that an increase in Fe 2 O 3 addition leads to a reduction in the size of the synthetic crystals and a gradual decrease in the growth rate. The diamonds with complete crystal forms exhibited no significant change in color, and all appeared yellow. When the addition exceeded a threshold, cracks appeared around the seed crystal at about 0.3 mm, resulting in a cracked crystal phenomenon. A further increase in the Fe 2 O 3 addition resulted in the skeleton crystal, and the crystal color turned black. Fourier Transform Infrared Spectroscopy (FTIR) measurements were also conducted, indicating that the introduction of oxygen atoms increases the nitrogen content in the crystals, which in turn aggregates in the form of C-centered nitrogen. The Raman spectroscopy results showed that as Fe 2 O 3 addition in the crystals increases, more impurities are introduced, leading to an increase in the diamond stress and a shift in the diamond Raman peak, along with an increase in the full width at half maximum. The photoluminescence (PL) characterization results indicated that with the increase of the Fe 2 O 3 addition, the intensity of the photoluminescence peaks of NV− centers and W8 centers was enhanced, which is related to the increase in the internal C-centered nitrogen content of the crystals. From the acquired results, it was proven that Fe 2 O 3 addition has a significant impact on the synthesis of diamond single crystals. Our work provides valuable pieces of experimental evidence for exploring the formation mechanism of natural diamonds. • There is an upper limit of oxygen concentration in diamond synthesis by high-pressure and high-temperature conditions. • Excessive Fe 2 O 3 addition will lead to crystal cracking phenomenon. • When the C center nitrogen content is low, with the increase of Fe 2 O 3 addition, the strength of NV− color center is enhanced. • The introduction of Fe 2 O 3 addition will increase the residual stress on the crystal surface. [ABSTRACT FROM AUTHOR]

This study reports the successful synthesis of high‑nitrogen-content diamond (2723 ppm) within the Fe-Ni-C-N system, utilizing g-C 3 N 4 as a new nitrogen source via the temperature gradient method under high-pressure and high-temperature (HTHP) conditions. The study investigated the role of nitrogen atoms in facilitating the growth of large diamonds with {111} plane orientation. Analysis of crystal morphology, nitrogen defect content, and nitrogen incorporation forms were conducted. As the amount of g-C 3 N 4 increased, the crystal size decreased, the color changed from yellow to green with increasing depth, and the growth rate notably decreased. The Fourier transform microscopy infrared spectroscopy (FT-IR) characterization revealed increased nitrogen content within the crystal due to nitrogen atom introduction. Raman characterization indicated increased residual stress with higher nitrogen content, leading to shifts in Raman peak positions and broadening of half-peak widths of the diamond. Photoluminescence (PL) characterization indicated that g-C 3 N 4 addition increased, resulting in a fading state of NV− and W8 defects. The results indicated that g-C 3 N 4 , as a new nitrogen source, exhibited superior doping efficiency within the diamond lattice compared with traditional nitrogen sources. The study offered valuable insights into the preparation and potential applications of high‑nitrogen diamond single crystals. • Diamond single crystal with high nitrogen content using g-C 3 N 4 as nitrogen source was synthesized for the first time. • There is an upper limit for nitrogen impurities in diamond under certain pressure and temperature conditions. • Proper nitrogen content is conducive to the formation of NV− defects. • The introduction of N impurities will increase the residual stress on the crystal surface [ABSTRACT FROM AUTHOR]

The effect of nitrogen on the growth of boron-doped diamonds was investigated by removing or adding nitrogen impurities. Optical microscopy images showed that adding a small amount of boron to nitrogen-free diamond completely transformed the diamond into an opaque black color. In the presence of small amounts of boron, the addition of nitrogen diminished the chromogenic properties of boron impurities in diamond. The FTIR spectra showed a compensatory interaction between boron and nitrogen in diamond, causing a portion of the nitrogen to exist as N+ center. Raman spectroscopy confirmed that adding small amounts of nitrogen to diamond reduced the stresses in the diamond and improved its quality, whereas adding excessive amounts of nitrogen reduced the quality. The Hall effect measurements showed that adding nitrogen to boron-doped diamond reduced its p-conductivity, causing an increase in its resistivity and a decrease in its carrier concentration. • Diamonds with different additions were successfully synthesized at high pressure and high temperature. • The presence of boron and nitrogen affects the morphological characteristics of diamonds. • Part of nitrogen exists in the form of N+ center in boron and nitrogen co-doped diamonds. • The relative content of boron and nitrogen affects the quality of diamonds. [ABSTRACT FROM AUTHOR]

Nitrogen-valent (NV) color centers exhibit unique quantum and physical properties, making them valuable in advanced scientific research and technical fields. Type IIa diamonds are ideal carriers for NV−color centers. Therefore, the development of methods for incorporating these centers into diamonds is a key research focus. To enhance the preparation techniques, this study introduces a donor impurity element doping method for the successful synthesis of type IIa diamonds containing only NV−color centers. Optical microscopy and scanning electron microscopy characterizations revealed that the introduction of H–S–O impurity elements hindered the synthesis of high-quality diamonds. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy analyses indicated that incorporating H–S–O into the diamond lattice led to the successful preparation of H–S–O multi-doped IIa diamonds. Photoluminescence results confirmed that these H–S–O multi-doped type IIa diamonds exhibited only NV− color centers. Additionally, the effects of H–S–O and Al on diamond properties and growth characteristics were thoroughly analyzed through Raman spectroscopy and residual stress analysis. This study provides valuable insights into the origins of natural IIa diamonds and introduces a vital method for preparing NV−color centers in functional IIa diamonds. • H–S–O will degrade the catalytic properties of Fe 58 Ni 42 and hinder the synthesis of high-quality crystals. • High-quality H–S–O multi-doped Ib diamond was synthesized. • High-quality IIa and H–S–O multi-doped IIa diamonds were synthesized. • Donor impurity doping method was proposed and IIa diamond containing only NV− was synthesized. • Al will degrade the catalytic performance of Fe 58 Ni 42 and increase the cavity pressure. [ABSTRACT FROM AUTHOR]

Nitrogen impurity remains a crucial focus in diamond impurity research. To address difficulties associated with excessive nitrogen impurities during the synthesis of high-quality diamonds under high-pressure and high-temperature conditions and to increase the proportion of aggregated nitrogen impurities in diamonds, we explored the multi-element growth environment of natural diamonds. In this study, we used N–H–S–O multi-component co-doping to increase the proportion of aggregated nitrogen impurities in diamond. Through Fourier-transform infrared spectroscopy characterization, we successfully used the synergistic mechanism of N–H–S–O co-doping to achieve a 47.9% proportion of aggregated nitrogen impurities in diamond in a single synthesis and successfully synthesized the type IaA + Ib diamond. Raman tests revealed a lower residual stress in the high-quality large single-crystal diamond synthesized. Moreover, we comprehensively analyzed the mechanism of N–H–S–O co-doping to increase the proportion of nitrogen impurities in diamond aggregates and proposed an optimal ratio principle based on the experimental results. This study presents a method for synthesizing diamonds with a high proportion of aggregated nitrogen impurities and provides valuable guidance for elucidating the origin of natural diamonds and synthesizing multi-doped functional diamonds. • H-S-O will cause defects in the crystal, and high nitrogen will cause the crystal surface to be dominated by {111}. • According to the influence of N-H-S-O impurities on the nitrogen ratio of A-center, the optimal ratio principle is proposed. • N-H-S-O doped high‑nitrogen diamond and IaA+Ib type diamond with A-center nitrogen of 47.9% were synthesized. • The method of introducing H-S-O impurity can regulate the NV color center in diamond. • The synergistic effect of N-H-S-O can effectively reduce the residual stress inside diamond. [ABSTRACT FROM AUTHOR]

Diamond, as a wide-bandgap semiconductor, is expected to enable miniaturized applications for high-frequency and high-power electronics. One of the problems affecting the application of boron-doped diamond (BDD) lies in the inhomogeneous distribution of their boron impurities. This article reports the synthesis of BDDs in the Fe-Ti-B-C system. The growth sectors as well as the depth distribution characteristics of boron impurities were focused on. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy demonstrated that the boron content decreases along the (111), (113), and (100) directions in the growth sectors. Raman and Hall effect measurements of the crystals before and after polishing showed a higher boron content on the surface of the BDD than that of in the interior. The results of X-ray Photoelectron Spectroscopy (XPS) depth profiling responded that the contents of both B C and B O bonds on its surface decreased with the increase of etching depth. This work is an important reference for predicting the distribution pattern of boron impurities, which will be of great significance for the modernization and implementation of BDDs. • Characteristics of boron impurities distribution in boron-doped diamonds synthesized by HPHT method were investigated • The distribution pattern of boron impurities in different growth sectors of boron-doped diamond has been analyzed • Boron-doped diamonds have higher boron concentrations on the surface than in the interior • Concentration of B C and B O bonds decrease with etching depth [ABSTRACT FROM AUTHOR]

This article investigates the influence of different silicon carbide contents on the morphology and quality of diamond single crystals synthesized in the Fe-Ni-C-Si system under high temperature and pressure environments. It was found that silicon successfully entered the diamond lattice through bonding. As the doping concentration increases, the growth rate of diamond crystals decreases and defects appear on the crystal surface. The increase in internal stress in the lattice reduces the quality of diamond, as evidenced by the shift in Raman peak and half peak width of the diamond. Moreover, the infrared characterization results showed that the nitrogen element in the crystal exists as a single atom (C-center) in the diamond crystal, and the nitrogen content decreases with the increase of SiC content. This work provides insights for understanding the growth mechanism of natural diamonds and enriching the application of silicon doped diamond single crystals. • Synthesis of Ib-type silicon-doped slab diamonds using Fe/Ni catalysts at high temperature and pressure. • Detailed exploration of the behavior characteristics of impurities in silicon doped diamond. • Revealed the mechanism of the influence of silicon impurities on crystal growth in the synthesis process. • Discussed the influence of different silicon carbide contents in the synthesis system on the quality change of diamond. [ABSTRACT FROM AUTHOR]

This article investigates the effects of different iron based catalysts on the morphology and quality characteristics of diamond single crystals synthesized in high-temperature and high-pressure environments. The results indicated that incorporating silicon impurities led to defects in diamond crystals, increased internal stress in the lattice, and decreased crystal quality. In addition, there are also differences in the synthesis of silicon doped diamonds under different iron based catalyst systems. This manuscript uses optical microscopy, scanning electron microscopy and Raman spectroscopy to characterize diamond crystals, exploring the influence of catalyst differences on the structure of silicon-doped diamonds. At the same time, simulation analysis was conducted on the convective field of the catalyst in the diamond synthesis chamber, and the convective field characteristics of silicon doped diamond growth under different iron based catalysts were established. The simulation results are consistent with the synthesis experimental work. This work provides a new approach to improve the quality of silicon doped diamond single crystals. • Synthesis of Ib type diamond crystals using different iron based catalysts in high-temperature and high-pressure environments. • Revealed the influence mechanism of iron based catalysts with different viscosities on the growth of silicon doped diamond. • Analyze and discuss the impurity characteristics inside diamonds synthesized under different iron based catalyst systems • Discuss the differences in the quality changes of silicon doped diamond with different viscous iron based catalysts. [ABSTRACT FROM AUTHOR]

Nitrogen and hydrogen impurities play a vital role in the growth of diamonds. A series of nitrogen–hydrogen co-doped diamonds was synthesized through the temperature gradient growth method using melamine (C 3 H 6 N 6) and ferrocene (Fe(C 5 H 5) 2) as nitrogen and hydrogen sources at 6.0 GPa and 1368–1384 °C. NiMnCo alloy was used to catalyze the synthesis of the diamond, and Ni was used as a hydrogen storage material to facilitate the introduction of hydrogen into the diamond. The results showed that the introduction of hydrogen slightly affected the growth rate of the diamond crystal. In contrast, the introduction of nitrogen impurities decreased the growth rate of the diamond crystal. The PL spectra of the samples showed that the high‑nitrogen content in the diamond was not conducive to the formation of the NV color center, and the appropriate nitrogen content favored the formation of the NV color center. Fourier transform infrared spectra of the diamond revealed that the introduction of hydrogen promoted the aggregation of nitrogen atoms and increased the A-center nitrogen ratio in the diamond. Raman spectroscopy results showed that the introduction of hydrogen weakened the residual stress in the diamond. These findings help to understand the crystal quality of natural diamonds with hydrogen-rich and aggregated nitrogen impurities and also provide a solution for reducing the residual stress of diamonds. • There is an upper limit for nitrogen and hydrogen impurities in diamond under certain pressure and temperature conditions. • The introduction of hydrogen impurity is beneficial to promote that aggregation of nitrogen impurities in diamond. • Appropriate nitrogen content is a key factor in the formation of NV color centers. • The introduction of hydrogen impurities helps to weaken the residual stress in high‑nitrogen diamond. [ABSTRACT FROM AUTHOR]

Pressure is a vital condition in the synthesis of diamond crystals via the temperature gradient method. Exploring the effect of pressure on the growth of diamond crystals is vital. In this study, we investigated the synthesis of diamond crystals using iron–nickel alloy catalysts and analyzed the properties of the synthesized diamonds in the pressure gradient using a China-type large-volume cubic high-pressure apparatus. The synthesis temperature of 1600 K and pressure range of 5.5–6.5 GPa were used. The results of Raman spectra showed that increasing the pressure would increase the crystallinity of diamond crystals. The FTIR spectra of diamond samples featured peaks at 1332 (N+ ions), 1130, and 1344 cm−1, indicating that with increasing pressure, the concentration of nitrogen atoms and ions in diamonds significantly decreased. The photoluminescence spectra of nitrogen ions in diamond samples displayed a peak at 40–100 ppm. The 692 and 694 nm peaks and the phonon bands of NV-chromophores gradually weakened with increasing pressure, indicating that the 692 and 694 nm peaks are attributable to the NV-color center and phonon displacement energy of 165 meV occurred. The Electron paramagnetic resonance spectra displayed a phonon bands of the NV-color center phonon are expressed in EPR through the g-value of NV-.These test results indicated that the pressure featured a significant effect on the nitrogen concentration and the nitrogen-related defects in diamonds. • It is proved that pressure cannot effectively improve the quality of the surface morphology of diamond crystals. • The residual stress and half-peak width by Raman spectroscopy verified that pressure can improve the crystal quality of diamond crystals. • It was demonstrated that the increase in pressure can reduce the growth rate of diamond crystals and thus the nitrogen content and related defects, and N+ ions were found in diamond crystals with lower nitrogen content. • PL spectra and EPR spectra illustrate that phonon boundaries of NV-color centers are produced at 40–100 ppm of nitrogen in diamond crystals. [ABSTRACT FROM AUTHOR]

In this study, single crystal diamonds were successfully synthesized in a FeNi-S-C system under the constant conditions of 5.5 GPa and 1400 °C. The growth rate of the diamonds decreased due to the existence of sulfur (S) in the synthesis 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, thus diamond crystals with a high-quality sp 3 structure were obtained. The photoluminescence (PL) spectra showed that the nitrogen-vacancy (NV) center occurred more likely in diamond lattice growth along the {111} face. Compared to the NV − center, the NV 0 center could not be easily generated in the type Ib diamond lattice without the addition of S. Even if the NV 0 and NV − centers were generated simultaneously in the diamond lattice with the addition of 0.25 wt% S, the intensity was higher for the NV − peak than for the NV 0 peak. The results of this study improve our understanding of the formation mechanisms of natural diamonds and represent an effective method for controlling the NV center in the diamond lattice. [ABSTRACT FROM AUTHOR]

Negatively charged silicon-vacancy (SiV−) colour centres are considered to be promising room-temperature single-photon sources. The controlled preparation of high-grade industrial diamonds containing a certain amount of SiV− colour centres remains a significant technical challenge. Herein, micron-sized industrial-grade diamonds containing different concentrations of SiV− colour centres were prepared by adjusting the doping amount of Si powder under the pressure conditions of 5.0–5.2 GPa and temperatures of 1420–1500 °C. Al was used as the nitrogen getter in FeNiCo−C systems through the diamond film growth method (FGM). The results show that the intensity of the SiV− colour centres in synthesized diamond increases with increases in the Si doping amount. It has also been proved that nitrogen impurities inhibit the formation of SiV− colour centres in diamond. In addition, the diamond Raman peak positions exhibit a redshift (from 1330.88 cm−1 to 1329.55 cm−1), and an increase in the Raman full width at half maximum (FWHM) (from 4.78 cm−1 to 5.17 cm−1), indicating that Si enters the diamond lattice, but the diamond crystals still have a single sp3 structure. Our research provides a fast, efficient and low-cost method for the controlled batch preparation of industrial-grade diamond containing SiV− colour centres. [Display omitted] • Micron-sized diamond single crystals with SiV− colour centres were prepared in bulk under relatively low conditions. • The intensity of SiV− colour centres in diamond crystals can be regulated by the amount of Si doping. • Our experimental results prove that the presence of nitrogen can significantly hinder the formation of SiV− colour centres. [ABSTRACT FROM AUTHOR]