氮氢共掺杂金刚石中氢的典型红外特征峰的表征

所有天然Ia型金刚石红外光谱中都存在3107 cm-1特征峰,而在金属触媒直接合成的金刚石红外光谱中没有检测出3107 cm-1特征峰.本文在6.3 GPa,1500?C条件下,通过Fe70Ni30触媒中添加P3N5直接合成出具有3107 cm-1特征峰的氮氢共掺杂的金刚石.红外光谱分析表明,合成的金刚石中氢有两种存在形式:一种对应着乙烯基团C=CH2中C—H键的伸缩振动(3107 cm-1)和弯曲振动(1450 cm-1)的吸收峰,另一种对应着sp3杂化C—H键的对称伸缩振动(2850 cm-1)和反对称伸缩振动(2920 cm-1)的吸收峰.通过分析发现,3107 cm-1吸收峰与金刚石中聚集态的氮原子有关,当金刚石中没有聚集态的氮元素时,即使氮含量高也不会出现3107 cm-1峰;并且2850和2920 cm-1附近的吸收峰比3107 cm-1附近的吸收峰更为普遍存在.这说明sp3杂化C—H键比乙烯基团的C—H键更广泛存在于金刚石中,从两者的峰值看,天然金刚石中的氢杂质主要以乙烯基团C=CH2存在.3107 cm-1吸收峰与聚集态的氮原子的这种存在关系为天然金刚石形成机制的研究提供了一种新思路,同时较低的合成条件也可能为氢与其他元素共掺杂合成具有n型半导体特性的金刚石提供一个较理想的合成环境.     

添加Fe(C5H5)2合成氢掺杂金刚石大单晶及其表征

在Ni₇₀Mn₂₅Co₅-C体系中添加含氢化合物Fe(C₅H₅)₂作为新型氢源, 利用温度梯度法, 在压力为5.5-6.0 GPa、温度为1280-1400 ℃的条件下, 成功合成出氢掺杂的宝石级金刚石大单晶. 通过傅里叶显微红外光谱发现, 随着Fe(C₅H₅)₂添加量的增加, 合成晶体中与氢相关的对应于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2850和2920 cm^-1逐渐增强, 而晶体中氮含量却逐渐减少. 通过合成晶体的拉曼光谱分析发现, 金刚石的拉曼峰伴随Fe(C₅H₅)₂的添加向高频偏移, 这表明氢的进入在金刚石内部产生了压应力. 观察扫描电子显微镜图像发现, 在低含量Fe(C₅H₅)₂添加时晶体表面平滑, 而高含量添加时晶体表面缺陷增多, 且呈现出气孔状. 使用新的添加剂Fe(C₅H₅)₂作为氢源, 合成出含氢宝石级金刚石单晶, 丰富了金刚石单晶中对氢的研究内容, 也可为理解天然金刚石的形成机理提供帮助.     

Hydrogen incorporation behaviour and radiation damage in proton bombarded InP single crystals

Abstract

In proton bombarded InP single crystals the incorporation behaviour of different hydrogen isotopes is studied in relation to implantation induced radiation defects. Investigations of the fluence dependence (D = 10¹⁶-10¹⁸ cm^?2), of the depth profile and of the annealing behaviour (T _an = 300–1000 K) of hydrogen incorporation and of damage density indicate that only a small fraction of the implanted hydrogen is chemically bonded to host lattice atoms. These bonded hydrogen atoms saturate dangling bonds at defect sites.     

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.     

Synthesis of carbon nitride films by direct current plasma assisted pulsed laser deposition

Carbon nitride films were deposited by pulsed laser ablation of a graphite target under a nitrogen atmosphere at room temperature. A direct current discharge apparatus was used to supply active nitrogen species during the deposition of carbon nitride films. The composition and bonding structure of carbon nitride films were determined by Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy. The incorporation of nitrogen atoms in the films is greatly improved by the using of a dc glow discharge. The ratio N/C can reach 0.34 at the discharge voltage of 400 V. Six peaks centered at 1025 cm^-1, 1226 cm^-1, 1381 cm^-1, 1534 cm^-1, 1629 cm^-1, and 2200 cm^-1 can be clearly distinguished from the FTIR spectra of the deposited films, which indicates the existence of C–N, C=N, and C≡N bonds. The fraction of sp² C, C≡N bonds, and C=N bonds in the deposited films increases with increasing discharge voltage. Deconvolution results of C 1s and N 1s spectra also indicate that nitrogen atoms in the films are chemically bonded to sp¹ C, sp² C, and sp³ C atoms. Most of the nitrogen atoms are bonded to sp² C atoms. Increasing the discharge voltage leads to a decrease of the fraction of nitrogen atoms bonded to sp² C and the fraction of amorphous carbon; however, it leads to an increase of the fraction of nitrogen atoms bonded to sp³ C and the fraction of sp² C and sp³ C atoms bonded to nitrogen atoms. Received: 7 June 2000 / Accepted: 19 February 2001 / Published online: 27 June 2001     

A new study on the catalytic mechanism of Fe-based alloys in diamond formation by Mössbauer spectroscopy

M?ssbauer spectroscopy has been used to systemically study the catalytic mechanism of Fe-based alloys in diamond formation at high temperature–high pressure (HTHP) for the first time. M?ssbauer spectra reveal the magnetic state of the 3d electrons of a Fe atom in the Fe-based alloy catalyst during diamond formation at HTHP. During carburization at lower temperatures than that required for diamond formation and diamond formation in the diamond-stability region using Fe-based alloys as a catalyst, both the quadrupole splitting QS and the isomer shift IS change from negative to positive, especially reaching a state in which they are zero. It was indicated that the state of the 3d-shell electrons of the iron atom changes greatly during carburization and diamond formation and that the incomplete 3d sub-bands of Fe atoms in the catalyst alloys could be filled up in proper order by electrons of interstitial carbon atoms. During diamond formation, the unpaired 3d-shell electrons of an iron atom in the Fe-based alloy absorb and interact with 2P_z electrons of the carbon atoms. There exist a Fe–C bonding and an electron charge transfer stage. The 2P_z electrons of the carbon atoms could be dragged into the metal atoms in the catalyst alloy and would make a transition of triangular (sp²π) hybridization of valence electrons to tetrahedral (sp³) hybridization of valence electrons (a transition of sp²π bonds of graphite to sp³ bonds of diamond), resulting in a transition of graphite structure to diamond. Although the conclusion of this study is strictly applicable only to Fe-based alloy catalysts, it could be considered more general because of the chemical similarities between the transition elements used as solvent catalysts for diamond synthesis. Received: 2 March 2001 / Accepted: 20 August 2001 / Published online: 2 October 2001     

Phonon spectrum of a naphthalene crystal at a high pressure: Influence of shortened distances on the lattice and intramolecular vibrations

The Raman spectra of a naphthalene crystal have been measured at room temperature in the pressure range up to 20 GPa. The pressure shift and Grüneisen parameters for intermolecular and intramolecular phonons have been determined. The maximum rate of the pressure shift for intermolecular phonons is 44 cm^?1/GPa, and the rate of the pressure shift for intramolecular phonons lies in the range from 1 to 11 cm^?1/GPa for different modes. The pressure dependence of the phonon frequencies for direct and inverse pressure variations has a hysteresis in the pressure range from 2.5 to 16.5 GPa. It has been shown that the linear dependence of the intermolecular phonon frequency on the crystal density has a peculiarity, which indicates a possible phase transition at a pressure of 3.5 GPa. The pressure dependence of intramolecular phonons related to the stretching vibrations of hydrogen atoms exhibits features that are characteristic of intermolecular phonons, which is associated with the influence of shortened distances between the hydrogen atoms of the neighboring molecules on the intermolecular interaction potential.     

掺杂CVD金刚石薄膜的应力分析

在不同实验条件下，用微波等离子体化学气相沉积(MPCVD)技术在Si基体上制备了S掺杂和B-S共掺杂CVD金刚石薄膜，利用X射线衍射仪和拉曼光谱仪研究掺杂对CVD金刚石薄膜的应力影响.研究结果发现，随着S掺杂浓度的增加，薄膜中sp²杂化碳含量和缺陷增多，CVD金刚石薄膜压应力增加；小尺寸的B原子与大尺寸的S原子共掺杂时，微量B的加入改变了CVD金刚石薄膜的应力状态，共掺杂形成B-S复合体进入金刚石晶体后降低金刚石晶体的晶格畸变程度，减少S原子在晶界上偏聚数量和晶体中非金刚石结构相含量，降低由于杂质、缺陷及sp²杂化碳含量产生的晶格畸变和薄膜压应力，提高晶格完整性. 关键词： 金刚石薄膜 掺杂 应力     

Raman scattering in the submicrometer diamond membrane formed by the lift-off technique

Spectral characteristics of spontaneous Raman scattering in the submicrometer diamond membrane grown by the hydrogen implantation method are studied in comparison with the single-crystal diamond matrix. A shift in the main line of diamond one-photon excitation (sp ³-hybridization) at a frequency of 1324 cm^?1 is revealed in the diamond membrane. This fact indicates multiple internal strains (residual compression strains) due to residual defects and is a concequence of the use of the hydrogen implantation method (hydrogen is implanted into diamond to form a sacrificial layer.     

Thermally stable hydrogen compounds obtained under high pressure on the basis of carbon nanotubes and nanofibers

Compounds containing 6.3–6.5 wt % H and thermally stable in vacuum up to 500°C were obtained by annealing graphite nanofibers and single-walled carbon nanotubes in hydrogen atmosphere under a pressure of 9 GPa at temperatures up to 45°C. A change in the X-ray diffraction patterns indicates that the crystal lattice of graphite nanofibers swells upon hydrogenation and that the structure is recovered after the removal of hydrogen. It was established by IR spectroscopy that hydrogenation enhances light transmission by nanomaterials in the energy range studied (400–5000 cm^?1) and results in the appearance of absorption bands at 2860–2920 cm^?1 that are characteristic of the C–H stretching vibrations. The removal of about 40% of hydrogen absorbed under pressure fully suppresses the C–H vibrational peaks. The experimental results are evidence of two hydrogen states in the materials at room temperature; a noticeable portion of hydrogen forms C–H bonds, but the most of the hydrogen is situated between the graphene layers or inside the nanotubes.     

Influence of annealing treatment on as-grown Ib-type diamond crystal at a high temperature and high pressure

In this paper,we report on the influence of annealing treatment on as-grown Ib-type diamond crystal under high pressure and high temperature in a china-type cubic anvil high-pressure apparatus.Experiments are carried out at a pressure of 7.0 GPa and temperatures ranging from 1700 C to 1900 C for 1 h.Annealing treatment of the diamond crystal shows that the aggregation rate constant of nitrogen atoms in the as-grown Ib-type diamond crystal strongly depends on diamond morphology and annealing temperature.The aggregation rate constant of nitrogen remarkably increases with the increase of annealing temperature and its value in octahedral diamond is much higher than that in cubic diamond annealed at the same temperature.The colour of octahedral diamond crystal is obviously reduced from yellow to nearly colorless after annealing treatment for 1 h at 1900 C,which is induced by nitrogen aggregation in a diamond lattice.The extent of nitrogen aggregation in an annealed diamond could approach approximately 98% indicated from the infrared absorption spectra.The micro-Raman spectrum reveals that the annealing treatment can improve the crystalline quality of Ib-type diamond characterized by a half width at full maximum at first order Raman peak,and therefore the annealed diamond crystals exhibit nearly the same properties as the natural IaA-type diamond stones of high quality in the Raman measurements.     

Raman spectra of potassium, rubidium, and thallium hydrogen phthalates

The polarized Fourier-transform Raman spectra of oriented single crystals of K, Rb, and Tl hydrogen phthalates, as well as of deuterated potassium hydrogen phthalate, are studied in the range 50–3300 cm^?1 in different scattering geometries. The frequencies of internal vibrations in the spectra of these compounds are assigned to vibrations of the orthophenylene and carboxyl groups. The replacement of K with Rb or Tl leads to an insignificant low-frequency shift of vibrations. A multiband structure of OH(D) stretching vibrations is observed in the range 1900–2800 cm^?1 in the spectra of all hydrogen phthalates, which is caused by Fermi-resonance interactions. A number of additional bands are observed in the spectrum of deuterated potassium hydrogen phthalate, which indicates that deuterium atoms partially replace hydrogen atoms in both the orthophenylene and the carboxyl groups.     

Studying the effect of hydrogen on diamond growth by adding C10H10Fe under high pressures and high temperatures

In this paper, hydrogen-doped industrial diamonds and gem diamonds were synthesized in the Fe–Ni–C system with C₁₀H₁₀Fe additive, high pressures and high temperatures range of 5.2–6.2?GPa and 1250–1460°C. Experimental results indicate similar effect of hydrogen on these two types of diamonds: with the increasing content of C₁₀H₁₀Fe added in diamond growth environment, temperature is a crucial factor that sensitively affects the hydrogen-doped diamond crystallization. The temperature region for high-quality diamond growth becomes higher and the morphology of diamond crystal changes from cube-octahedral to octahedral. The defects on the {100} surfaces of diamond are more than those on the {111} surfaces. Fourier transform infrared spectroscopy (FTIR) results indicate that the hydrogen atoms enter into the diamond crystal lattice from {100} faces more easily. Most interestingly, under low temperature, nitrogen atoms can also easily enter into the diamond crystal lattice from {100} faces cooperated with hydrogen atoms.     

Raman scattering studies on phase transition in barium sodium niobate at high pressure

Phase transition in barium sodium niobate at high pressure is investigated by Raman scattering experiments. Polarized Raman spectra from polished single domain crystal plates of definite orientation are obtained under pressure produced by a diamond anvil device. Anomalous hardening and intensity decrease of 32 cm^-1B₂ mode are found with increasing pressure. A remarkable pressure dependence of the frequencies of the bending modes of NbO₆ octahedrons is observed.     

新型激光晶体Yb:KY(WO4)2的结构与光谱

采用顶部籽晶提拉法，以K₂W₂O₇为助溶剂，生长了Yb:KY(WO₄)₂新型激光晶体.经热重-差热分析，确定晶体熔点为1045℃，相变温度为1010℃.X射线粉末衍射测试，验证所生长的晶体为β-Yb:KY(WO₄)₂.晶体结构分析确定Yb:KY(WO₄)₂晶体由WO₆八面体连接而成，WO₆八面体是由双氧桥(WOOW)及单氧桥(WOW)构成.晶体粉末样品室温下的红外及拉曼光谱测试，确定WO₆原子基团、双氧桥及单氧桥的振动频率.晶体的吸收峰位于940nm，980nm，发射峰位于989nm—1030nm. 关键词： 晶体结构 光谱 晶体生长     

Raman scattering in TlInS2xSe2(1−x) layered mixed crystals (0.25≤x≤1): Compositional dependence of the mode frequencies and line widths

The Raman spectra of TlInS_2xSe_2(1−x) layered mixed crystals were studied for a wide composition range (0.25≤x≤1) in the frequency region 10-360 cm⁻¹ at room temperature. The shift of Raman-active phonon frequencies versus mixed crystals composition x were established. The effect of crystal disorder on the line width broadening of three high-frequency Raman-active modes is reported.     

退火对B掺杂纳米金刚石薄膜微结构和电化学性能的影响

采用热丝化学气相沉积法制备B掺杂纳米金刚石薄膜,并对薄膜进行真空退火处理,系统研究了不同退火温度对B掺杂纳米金刚石薄膜的微结构和电化学性能的影响.结果表明,当退火温度升高到800 ℃后,薄膜的Raman谱图中由未退火时在1157,1346,1470,1555 cm^-1处的4个峰转变为只有D峰和G峰,说明晶界上的氢大量解吸附量减少,并且D峰和G峰的积分强度比I_D/I_G值变为最小,即sp²相团簇     

Possibilities of C 1s XPS and N(E) C KVV Auger spectroscopy for identification of inherent peculiarities of diamond growth

The interaction of C-atoms and CH_n-radicals with uncleaned and argon cleaned silicon substrate and with diamond surface after H-treatment have been studied in situ by XPS and Auger spectroscopy. It was found the formation of a new chemical surface state of carbon atoms in the case of carbon atoms and radicals interaction with cleaned silicon. The same chemical state was revealed on the H-treated diamond surface. Graphite-like structure of carbon atoms was observed on the surface of unlearned silicon and H-treated diamond after interaction with carbon atoms and radicals. N(E) C KVV Auger spectrum for the new chemical state of carbon atoms significantly differs from typical spectra for sp²- and sp³-bonded carbon materials. The high energy part of this spectrum was interpreted under the hypothesis of sp³-bonded carbon atoms but with shifted fermi level position.     

Vibrational spectrum of Li2B4O7 crystals

Polarized IR reflection spectra of Li₂B₄O₇ crystals are studied in a spectral range of 80–1600 cm^?1 and compared with their Raman spectra. Based on the results of the dispersion analysis of the spectra, the frequencies, damping constants, and oscillator strengths of all vibrations are determined. The inversion of frequencies of the longitudinal and transverse vibrations of the A ₁ and E symmetry in a range of 900–1150 cm^?1 is found. Based on the data thus obtained, the effective charges are calculated and the types of chemical bonds are analyzed for structural groups of the Li₂B₄O₇ crystal.     

Optical absorption spectra of synthetic CoCO3 single crystal

New results have been obtained on absorption spectra of synthetic CoCO₃ single crystal in the spectral range from the 11,500 to 34,500 cm^-1. Some vibration frequencies of the (CO₃)^2- ions have deduced from the absorption spectrum and zero-phonon lines have been identified. In the regions 22,900 and 24,500 cm^-1, a shift is observed of absorption frequencies with antiferromagnetic order for temperatures increasing from 4.2 to 20°K.