Growth and annealing study of hydrogen-doped single diamond crystals under high pressure and high temperature

A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 C to 1350 C.It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization.Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp 3-CH 2-symmetric(2850 cm-1) and sp 3 CH 2-antisymmetric vibrations(2920 cm-1).The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst.The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm-1 to 1333.05 cm-1 and gives rise to some compressive stress in the diamond crystal lattice.Furthermore,hydrogen to carbon bonds are evident in the annealed diamond,indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm-1 have no observable shift.Therefore,we suggest that the sp 3 C-H bond is rather stable in diamond crystals.     

Synthesis and characterizations of boron and nitrogen co-doped high pressure and high temperature large single-crystal diamonds with increased mobility

We synthesized and investigated the boron-doped and boron/nitrogen co-doped large single-crystal diamonds grown under high pressure and high temperature (HPHT) conditions (5.9 GPa and 1290℃). The optical and electrical properties and surface characterization of the synthetic diamonds were observed and studied. Incorporation of nitrogen significantly changed the growth trace on surface of boron-containing diamonds. X-ray photoelectron spectroscopy (XPS) measurements showed good evident that nitrogen atoms successfully incorporate into the boron-rich diamond lattice and bond with carbon atoms. Raman spectra showed differences on the as-grown surfaces and interior between boron-doped and boron/nitrogen co-doped diamonds. Fourier transform infrared spectroscopy (FTIR) measurements indicated that the nitrogen incorporation significantly decreases the boron acceptor concentration in diamonds. Hall measurements at room temperature showed that the carriers concentration of the co-doped diamonds decreases, and the mobility increases obviously. The highest hole mobility of sample BNDD-1 reached 980 cm²·V^-1·s^-1, possible reasons were discussed in the paper.     

Growth of gem-grade nitrogen-doped diamond crystals heavily doped with the addition of Ba（N3）2

Additive Ba(N 3) 2 as a source of nitrogen is heavily doped into the graphite-Fe-based alloy system to grow nitrogendoped diamond crystals under a relatively high pressure (about 6.0 GPa) by employing the temperature gradient method.Gem-grade diamond crystal with a size of around 5 mm and a nitrogen concentration of about 1173 ppm is successfully synthesised for the first time under high pressure and high temperature in a China-type cubic anvil highpressure apparatus.The growth habit of diamond crystal under the environment with high degree of nitrogen doping is investigated.It is found that the morphologies of heavily nitrogen-doped diamond crystals are all of octahedral shape dominated by {111} facets.The effects of temperature and duration on nitrogen concentration and form are explored by infrared absorption spectra.The results indicate that nitrogen impurity is present in diamond predominantly in the dispersed form accompanied by aggregated form,and the aggregated nitrogen concentration in diamond increases with temperature and duration.In addition,it is indicated that nitrogen donors are more easily incorporated into growing crystals at higher temperature.Strains in nitrogen-doped diamond crystal are characterized by micro-Raman spectroscopy.Measurement results demonstrate that the undoped diamond crystals exhibit the compressive stress,whereas diamond crystals heavily doped with the addition of Ba(N 3) 2 display the tensile stress.     

Synthesis and characterization of a single diamond crystal with a high nitrogen concentration

In this paper,we explore diamond synthesis with a series of experiments using an Fe-Ni catalyst and a P3N5 additive in the temperature range of 1250-1550 ℃ and the pressure range of 5.0-6.3 GPa.We also investigate the influence of nitrogen on diamond crystallization.Our results show that the synthesis conditions(temperature and pressure) increase with the amount of P3N5 additive increasing.The nitrogen impurity can significantly influence the diamond morphology.The diamonds stably grow into strip and lamellar shapes in the nitrogen-rich environment.The Fourier-transform infrared spectrum shows that the nitrogen concentration increases rapidly with the content of P3N5 additive increasing.By spectrum analysis,we find that with the increase of the nitrogen concentration,the Ib-type nitrogen atoms can aggregate in the A-centre form.The highest A-centre nitrogen concentration is approximately 840 ppm.     

Further study of the difference in nitrogen aggregation among (111) and (100) growth sectors of synthetic diamonds

Abstract

Single nitrogen atoms in synthetic diamond crystals aggregate in pairs by heat treatment under high pressure after electron irradiations. We find that the rate constants of nitrogen aggregation in the (111) growth sectors grown by the various solvents are about ten times greater than those of the (100) growth sectors. Furthermore the rate constant of nitrogen aggregation of the same sector is almost the same value. (shown Table-1). We have considered a few reasons for this fact. It may be accurate that a form of nitrogen atoms contained in (111) growth sectors of an as-grown diamond differs from that in (100) grown sectors and that the former accelerates nitrogen aggregation. Consequently we propose one nitrogen migration and aggregation model.     

高温高压下Fe-Ni-C系合成金刚石的研究

 以工业纯单质铁粉和单质镍粉为主要原料，采用粉末冶金方法制备了Fe-Ni-C系反应体系，在六面顶压机上进行了金刚石合成实验。Raman光谱和X射线衍射结果表明，采用这种方法获得的粒径为200~500 μm，呈六-八面体聚形的晶体为立方金刚石单晶。通过对常规力学性能的检测发现，金刚石的品位较高，超过SMD25级锯片级金刚石的要求。分析认为，高温高压下金刚石自Fe-Ni-C系形核是一个触媒不断溶解催化碳原子的过程。大量的实验结果可以证实，金刚石在Fe-Ni-C系长大所需的碳原子来自于在γ-(Fe，Ni)吸引作用下、从(Fe，Ni)₃C中不断脱溶的碳。金属包覆膜在这一过程中不但起到了输送碳原子的作用，还以独特的方式促成了碳原子由sp²π杂化态向sp³杂化态的转变。     

Synthesis and characterization of a single diamond crystal with a high nitrogen concentration

In this paper, we explore diamond synthesis with a series of experiments using an Fe-Ni catalyst and a P₃N₅ additive in the temperature range of 1250-1550 ℃ and the pressure range of 5.0-6.3 GPa. We also investigate the influence of nitrogen on diamond crystallization. Our results show that the synthesis conditions (temperature and pressure) increase with the amount of P₃N₅additive increasing. The nitrogen impurity can significantly influence the diamond morphology. The diamonds stably grow into strip and lamellar shapes in the nitrogen-rich environment. The Fourier-transform infrared spectrum shows that the nitrogen concentration increases rapidly with the content of P₃N₅additive increasing. By spectrum analysis, we find that with the increase of the nitrogen concentration, the Ib-type nitrogen atoms can aggregate in the A-centre form. The highest A-centre nitrogen concentration is approximately 840 ppm.     

高温高压下掺硼宝石级金刚石单晶生长特性的研究

本文在5.1—5.6 GPa,1230—1600℃的压力、温度条件下,以FeNiMnCo作为触媒,进行单质硼添加宝石级金刚石单晶的生长研究.借助于有限元法,对触媒内的温度场进行模拟.研究得到了FeNiMnCo-C-B体系下,金刚石单晶生长的P-T相图.该体系下合成金刚石单晶的最低压力、温度条件分别为5.1 GPa,1230℃左右.研究发现,在单晶同一{111}扇区内部,硼元素呈内多外少的分布规律.有限元模拟结果给出,该分布规律是由在晶体生长过程中,{111}扇区的增长速度逐渐减小所致.{111}晶向的晶体生长实验结果表明,硼元素优先从{111}次扇区进入晶体.研究发现,这是该扇区增长速度相对较快,硼元素扩散逃离可用时间短导致的.另外,同磨料级掺硼金刚石单晶生长相比,对于温度梯度法生长掺硼宝石级金刚石单晶,由于晶体的增厚速度较慢,即使硼添加量相对较高,也可以实现表面无凹坑缺陷的优质金刚石单晶的生长.     

Kr离子注入SiC的拉曼光谱研究

应用拉曼光谱研究了5 MeV Kr离子（注量分别为5×1013,2×1014,1×1015 ions/cm2）室温注入6H SiC单晶及其高温退火处理后结构的变化。 研究表明, 注入样品的拉曼光谱中不仅出现了Si—C振动的散射峰, 还产生了同核Si—Si键和C—C键散射峰。 Si—C散射峰强度随退火温度升高而增强, 当退火温度高达1000 ℃时, 已接近未辐照SiC的散射峰强度。晶体Si—Si键散射峰强度随退火温度变化不大, 而非晶Si—Si键散射峰强度随退火温度的增加逐渐消失。相对拉曼强度（Relative Raman Intensity, 简称RRI）随注量的增加逐渐减小并趋于饱和, 且不同退火温度样品的饱和注量不相同; RRI随退火温度的增加逐渐升高, 这在低注量样品中表现得尤为明显。 低、中、高3种注量样品的RRI随退火温度的增加从重合逐渐分离, 并且退火温度越高, 分离越大。 Raman spectroscopy was used to study the structure changes of 6H SiC single crystal implanted with 5 MeV Kr (Krypton) at room temperature and subsequently annealed at high temperature. The Raman spectrum of the implanted SiC displays not only Si—C bonds vibration peaks, but also homonuclear Si—Si and C—C bond vibration peaks. Si—C bond vibration peaks gradually strengthen with increasing temperature. When annealing at 1000 ℃, the peak intensity of Raman spectrum is close to that of virgin specimen. It is found that crystal Si—Si bond vibration peaks do not change when annealing, but amorphous Si—Si bond vibration peaks disappear with increasing annealing temperature. The Relative Raman Intensity (RRI) values decrease with increasing fluence and tend to saturate, but the saturation fluences is different for various anneal temperature. The RRI values increases with raising annealing temperature, which is more obvious in low implanted specimens. At the same time, the RRI values separate gradually with increasing temperature and this phenomenon is strengthened by annealing temperature.     

高温高压下碳纳米管的相转变及金刚石的合成

 利用透射电子显微镜（TEM）和扫描电子显微镜（SEM）研究了碳纳米管在高压高温下的相转变。研究发现在高压高温条件下碳纳米管是不稳定的,在5.5 GPa压力下,770 ℃到950 ℃间退火时碳纳米管趋向形成碳纳米葱。在5 GPa、1 000 ℃条件下合成了金刚石。     

超临界流体触媒作用下石墨-金刚石转变

 研究了超临界流体CO₂在石墨-金刚石转变中的触媒作用。实验中，采用Ag₂O作为流体触媒的先驱材料，在7.7 GPa压力下，Ag₂O在1 200 ℃分解成Ag和O₂，O₂与石墨套管在高温高压下反应形成CO₂超临界流体。研究结果表明，在7.7 GPa和1 500 ℃以上温度条件下，石墨在CO₂流体触媒的作用下可转变为金刚石晶体，在1 500～1 700 ℃温度范围内合成出的金刚石具有完好的八面体形貌，与天然金刚石的生长特征非常相似。     

Effects of Mg on diamond growth and properties in Fe–C system under high pressure and high temperature condition

Diamond crystal crystallized in Fe–Mg–C system with Archimedes buoyancy as a driving force is established under high pressure and high temperature conditions. The experimental results indicate that the addition of the Mg element results in the nitrogen concentration increasing from 87 ppm to 271 ppm in the diamond structure. The occurrence of the {100}plane reveals that the surface character is remarkably changed due to the addition of Mg. Micro-Raman spectra indicate that the half width of full maximum is in a range of 3.01 cm~(-1)–3.26 cm~(-1), implying an extremely good quality of diamond specimens in crystallization.     

合成腔体尺寸对Ib型六面体金刚石单晶生长的影响

利用液压缸直径为550 mm的大缸径六面顶压机, 在5.6 GPa, 1200-1400 ℃的高压高温条件下, 分别采用单晶种法和多晶种法, 开展了Ib型六面体宝石级金刚石单晶的生长研究, 系统考察了合成腔体尺寸对Ib型六面体金刚石大单晶生长的影响. 首先, 阐述了合成腔体尺寸对合成设备油压传递效率的影响, 研究得到了设备油压与腔体内实际压力的关系曲线; 其次, 选择尺寸为Φ 14 mm的合成腔体, 分别采用单晶种法和多晶种法(5颗晶种), 进行Ib型六面体金刚石大单晶的生长实验, 研究阐述了Φ 14 mm合成腔体的晶体生长实验规律; 再次, 为了解决液压缸直径与合成腔体尺寸不匹配的问题, 将合成腔体尺寸扩大到26 mm, 并开展了多晶种法六面体金刚石大单晶的生长研究, 最多单次生长出14 颗优质3 mm级Ib型六面体金刚石单晶, 研究得到了Φ 26 mm合成腔体生长3 mm级Ib型六面体金刚石单晶的实验规律, 并就两种腔体合成金刚石单晶的总体生长速度与生长时间的关系进行了讨论; 最后, 借助于拉曼光谱, 将合成的优质六面体金刚石单晶与天然金刚石单晶进行对比测试, 对所合成晶体的结构及品质进行了表征.     

Effects of catalyst height on diamond crystal morphology under high pressure and high temperature

The effect of the catalyst height on the morphology of diamond crystal is investigated by means of temperature gradient growth(TGG) under high pressure and high temperature(HPHT) conditions with using a Ni-based catalyst in this article. The experimental results show that the morphology of diamond changes from an octahedral shape to a cuboctahedral shape as the catalyst height rises. Moreover, the finite element method(FEM) is used to simulate the temperature field of the melted catalyst/solvent. The results show that the temperature at the location of the seed diamond continues to decrease with the increase of catalyst height, which is conducive to changing the morphology of diamond. This work provides a new way to change the diamond crystal morphology.     

磷离子注入纳米金刚石薄膜的n型导电性能与微结构研究

系统研究了磷离子注入并在不同温度退火后的纳米金刚石薄膜的微结构和电学性能.研究表明,当退火温度达到800 ℃以上时,薄膜呈良好的n型电导.Raman光谱和电子顺磁共振谱的结果表明,薄膜中金刚石相含量越高和完整性越好,薄膜电阻率越低. 这说明纳米金刚石晶粒为薄膜提供了电导.1000 ℃退火后,薄膜晶界中的非晶石墨相有序度提高,碳悬键数量降低,薄膜电阻率升高.薄膜导电机理为磷离子注入的纳米金刚石晶粒提供了n型电导,非晶碳晶界为其电导提供了传输路径. 关键词： 纳米金刚石薄膜 n型 磷离子注入     

高温高压下氮氢协同掺杂对{100}晶面生长宝石级金刚石的影响

在压力为5.5–6.2 GPa, 温度为1280–1450 ℃的条件下, 利用温度梯度法详细考察了氮氢协同掺杂对100晶面生长宝石级金刚石的影响. 实验结果表明伴随合成腔体内氮、氢浓度的升高, 合成条件明显升高, 金刚石生长V形区间上移; 晶体的红外光谱中与氮相关的吸收峰急剧增强, 氮含量可达2000 ppm, 同时位于2850 cm^-1和2920 cm^-1对应于 sp³杂化 C–H 键的对称伸缩振动和反对称伸缩振动的红外特征峰逐渐增强, 表明晶体中既有高的氮含量, 同时又含有氢. 对晶体进行电镜扫描发现, 氮氢协同掺杂对晶体形貌影响明显, 出现拉长的{111}面, 且晶体表面上有三角形生长纹理. 拉曼测试表明, 晶体的峰位向高频偏移、半峰宽变大, 说明氮、氢杂质的进入对晶体内部产生了应力. 本文成功地以{100}晶面为生长面合成出高氮含氢宝石级金刚石单晶, 在探究氮氢共存环境下金刚石生长特性的同时, 也可为理解天然金刚石的形成机理提供帮助.     

氮气氛中高温退火对NaYF4:Yb3+,Er3+纳米粒子上转换发光的影响

以柠檬酸三钠为螯合剂,采用共沉淀和水热相结合的方法成功制备出尺寸为40 nm的NaYF4:Yb3+Er3+纳米粒子.将得到的部分样晶在300℃氮气保护下退火2h.退火前后的样品晶体结构都属于立方相,尺寸保持在40 nm左右.在980 nm光激发下,退火后样品的上转换发光整体强度和绿光相对发射强度明显增强.分析认为高温退...     

锌添加对大尺寸金刚石生长的影响

利用温度梯度法,在6.2—6.4 GPa,1270—1400℃条件下,通过在NiMnCo-C体系中添加不同比例的锌粉成功合成出3 mm左右的大尺寸金刚石单晶.研究了锌添加对金刚石颜色、形貌、内部氮杂质以及晶体结晶度的影响.结果表明:随着锌添加量逐渐增加,晶体的颜色逐渐变浅,晶体的透光性增强;当锌添加比例达到3 wt.%时,晶体表面出现大量不规则的凹坑;晶体内氮杂质主要以C心形式存在,随着锌添加量的增多晶体内氮含量逐渐降低,基于锌的除氮能力总结出两种可能的除氮机制;拉曼光谱测试结果表明,在锌添加量小于3.0 wt.%的研究范围内,锌的添加有利于提高晶体的结晶度.本研究不仅有助于天然金刚石形成机制的探究,而且对丰富金刚石的种类以及扩展人工合成金刚石的应用领域都有着重要意义.     

高压退火对0.65PMN-0.35PT薄膜结构、形貌及电学性能的影响

利用射频磁控溅射技术在LaNiO₃/SiO₂/Si(100)基底上制备了厚 度约为250 nm的0.65PMN-0.35PT(PMN-PT)薄膜. 研究高压氧氛围退火方式对PMN-PT薄膜晶体结构、形貌以及电学性能的影响. 经过XRD测试发现,在高压氧气氛围中, 温度为400℃下退火后的PMN-PT薄膜具有纯的钙钛矿相结构, 具有完全的(100)择优取向, 且衍射峰尖锐, 表明经过高压退火后的薄膜结晶极为充分. SEM表面形貌测试结果显示, 经高压退火处理的PMN-PT薄膜表面呈现出棒状或泡状的形貌. 铁电性能测试表明: 氧气氛围压强4 MPa, 退火时间4h的PMN-PT薄膜样品具有较好的铁电性能, 其剩余极化强度P_r达到10.544 μC/cm², 且电滞回线形状较好, 但漏电流较大, 这可能是由于其微结构所导致.同时介电测试发现: PMN-PT薄膜样品具有极好的介电性能, 其在1 kHz下测试的介电常数ε_r达到913, 介电损耗tgδ 较小, 仅为0.065. 关键词： 射频磁控溅射 高压退火 0.65PMN-0.35PT 介电     

退火温度对硼掺杂纳米金刚石薄膜微结构和p型导电性能的影响

采用热丝化学气相沉积法制备硼掺杂纳米金刚石 (BDND) 薄膜, 并对薄膜进行真空退火处理, 系统研究退火温度对BDND薄膜微结构和电学性能的影响. Hall效应测试结果表明掺B浓度为5000 ppm (NHB) 的样品的电阻率较掺B浓度为500 ppm (NLB) 的样品的低, 载流子浓度高, Hall迁移率下降. 1000 ℃退火后, NLB和NHB 样品的迁移率分别为53.3和39.3 cm²·V^-1·s^-1, 薄膜的迁移率较未退火样品提高, 电阻率降低. 高分辨透射电镜、紫外和可见光拉曼光谱测试结果表明, NLB样品的金刚石相含量较NHB样品高, 高的硼掺杂浓度使薄膜中的金刚石晶粒产生较大的晶格畸变. 经1000 ℃退火后, NLB和NHB薄膜中纳米金刚石相含量较未退火时增大, 说明薄膜中部分非晶碳转变为金刚石相, 为晶界上B扩散到纳米金刚石晶粒中提供了机会, 使得纳米金刚石晶粒中B浓度提高, 增强纳米金刚石晶粒的导电能力, 提高薄膜电学性能. 1000 ℃退火能够恢复纳米金刚石晶粒的晶格完整性, 减小由掺杂引起的内应力, 从而提高薄膜的电学性能. 可见光Raman光谱测试结果表明, 1000℃退火后, Raman谱图中反式聚乙炔 (TPA) 的1140 cm^-1峰消失, 此时薄膜电学性能较好, 说明TPA减少有利于提高薄膜的电学性能. 退火后金刚石相含量的增大、金刚石晶粒的完整性提高及TPA含量的大量减少有利于提高薄膜的电学性能. 关键词： 硼掺杂纳米金刚石薄膜 退火 微结构 电学性能