Laser-induced chemistry in silane-hexafluoroacetone mixtures for production of novel Si/C/F/O and C/F/O materials

Chemical reactions induced by CO₂-laser radiation in mixtures of silane and hexafluoroacetone afford various gaseous silicon- and carbon-containing compounds and result in deposition of microstructures of carbon, C/F/O and Si/C/O/F materials. These products are suggested to be formed by a variety of exothermic reactions initiated through SiH₄-photosensitized decomposition of hexafluoroacetone. Silane is shown to be a very potent reagent for the reduction of C-F bonds.     

基于密度泛函理论的外电场下C_3F_8微观特性的研究

全氟丙烷(C_3F_8)作为一种拥有较低温室效应的SF_6替代气体,被国内外学者广泛研究.为了从分子层面上揭示全氟丙烷在外电场作用下微观特性的变化情况,采用密度泛函理论中的M06-2X方法,在6-31G(d)基组水平上优化得到了C_3F_8的基态稳定构型.分析了不同外电场(0-0.020 a.u.)对C_3F_8分子的结构、Highest Occupied Molecular(HOMO)、Lowest Unoccupied Molecular(LUMO)、能隙、键级的影响,并研究了全氟丙烷分子的激发态能、波长、振子强度.结果表明,在所加电场范围内,随着电场强度的增大,C_3F_8分子最高占据轨道能级逐渐增大,最低空轨道能级逐渐减小,能隙E_G逐渐减小, C_3F_8分子的化学活性增强;C_3F_8分子中的C-C键的Mayer Bond Order (MBO)值随电场强度的增大均出现增大的情况,分子的稳定性降低;C_3F_8分子激发态的激发能总体上呈现出减小的趋势,激发态的波长总体上则呈现出增大的趋势,表明在外电场的作用下,全氟丙烷分子变得越来越容易激发.     

Dense-Kondo antiferromagnetism in (CePd3)8Ge

We report the existence of (CePd₃)₈Ge and (LaPd₃)₈Ge, and find them to have the same cubic superstructure as reported for (CePd₃)₈T (T=Ga, In, Sn, Sb, Pb and Bi) by Gordon and co-workers [1 and 2]. The cerium ions in (CePd₃)₈Ge are trivalent and undergo an antiferromagnetic transition below 5 K with a dense-Kondo-lattice behaviour.     

Structural and electrical properties of high-k HfO2 films modified by CHF3 and C4F8/O2 plasmas

As-deposited HfO₂ films were modified by CHF₃, C₄F₈, and mixed C₄F₈/O₂ plasmas in a dual-frequency capacitively coupled plasma chamber driven by radio frequency generators of 60 MHz as the high frequency (HF) source and 2 MHz as the low frequency source (60/2 MHz). The influences of various surface plasma treatments under CHF₃, C₄F₈, and C₄F₈/O₂ were investigated in order to understand the chemical and structural changes in thin-film systems, as well as their influence on the electrical properties. Fluorine atoms were incorporated into the HfO₂ films by either CHF₃ or C₄F₈ plasma treatment; meanwhile, the C/F films were formed on the surface of the HfO₂ films. The formation of C/F layers decreased the k value of the gate stacks because of its low dielectric constant. However, the addition of O₂ gas in the discharge gases suppressed the formation of C/F layers. After thermal annealing, tetragonal HfO₂ phase was investigated in both samples treated with CHF₃ and C₄F₈ plasmas. However, the samples treated with O-rich plasmas showed monoclinic phase, which indicated that the addition of O plasmas could influence the Hf/O ratio of the HfO₂ films. The mechanism of the t-HfO₂ formation was attributed to oxygen insufficiency generated by the incorporation of F atoms. The capacitors treated with C₄F₈/O₂ plasmas displayed the highest k value, which ascribed that the C/F layers were suppressed and the tetragonal phase of HfO₂ was formed. Good electrical properties, especially on the hysteresis voltage and frequency dispersion, were obtained because the bulk traps were passivated by the incorporation of F atoms. However, the H-related traps were generated during the CHF₃ plasma treatments, which caused the performance degradation. All the treated samples showed lower leakage current density than the as-deposited HfO₂ films at negative bias due to the reduced trap-assisted tunneling by the incorporation of F to block the electrons transferring from metal electrode to the trap level.     

F8BT∶P3HT共混薄膜放大自发辐射的温度效应

研究了温度对聚合物poly(9,9-dioctylfluorene-co-benzothiadiazole)(F8BT)和poly(3-hexylthiophene)(P3HT)共混薄膜的放大自发辐射(ASE)的影响。在80~320 K温度范围测试了不同P3HT质量比的共混聚合物薄膜和纯F8BT薄膜的ASE特性。在室温条件下,共混聚合物的阈值随着P3HT所占比例的增加先降低后升高。当P3HT比例约为20%时,阈值最低约为2.59×10~3W/cm~2。当温度从320 K下降到80 K时,纯F8BT薄膜的ASE阈值光功率由5.36×10~3W/cm~2下降到4.15×10~3W/cm~2,P3HT质量比为20%的共混薄膜的ASE阈值光功率由2.84×10~3W/cm~2下降到2.03×10~3W/cm~2。在一特定泵浦光功率(5.29×10~3W/cm~2)下,当温度由320 K下降至80 K时,ASE强度约提高4倍。随着温度的降低,混合物薄膜的ASE峰位红移,移动达12 nm。     

He/C3H8(60/40)气体增益的实验研究

利用正比计数管测量了氦基混合气体He/C3H8(60/40)在55Fe 5.9keV X射线下的气体增益，并对气体增益随高压、温度、气压及气体比分的变化作了研究. 作为比较还对He/CH4(60/40)及Ar/CO2/CH4(89/10/1)混合气体进行了相应的测量.     

Optical spectroscopy of Ce 3+ ions in BaY 2 F 8 single crystals

In the present work we report on the spectroscopic properties of the Ce 3+ ion in BaY 2 F 8 single crystals. The absorption and excitation spectra of the emission centered at 340 v nm have been measured in the temperature range 15-300 v K. The 340 v nm emission consists of two broad partially overlapping bands, peaking at 324 and 347 v nm (at 15 v K), respectively. The full width at half maximum is about 0.5 v eV at room temperature. The absorption spectrum of the lowest in energy component of the f M d transition of Ce 3+ reveals at low temperature a marked vibronic structure. High resolution (0.02 v cm m 1 ) Fourier transform infrared spectroscopy in the wave number range 500-5000 v cm m 1 and in the temperature range 9-300 v K has been exploited to monitor the f level splitting. The absorption transitions from the three Stark components of the 2 F 5/2 manifold to the four of the 2 F 7/2 one, have been monitored in the wave number range 2000-3400 v cm m 1 . The wave number separation at 9 v K between the lowest level of the ground 2 F 5/2 manifold and lowest one of the 2 F 7/2 manifold is found to be 2197.47 v cm m 1 in good agreement with the splitting detected between the two components of the d M f emission.     

Inter- and intraconfigurational luminescence of Er 3+ ions in BaY 2 F 8 under VUV excitation

Using energy- and time-resolved spectroscopy the luminescence properties of Er 3+ doped BaY 2 F 8 crystals were investigated at 10 v K under VUV synchrotron radiation excitation. Radiative intraconfigurational f - f and interconfigurational d - f transitions in Er 3+ ions were observed under f - d excitation. Whereas the onset of 4 S 3/2 population via f - d excitation starts at 59 900 v cm m 1 , efficient excitation of emissions arising from the 2 P 3/2 state begins only above 67 000 v cm m 1 in VUV region. Such behaviour can be explained by a cross-relaxation process of the type ( 2 F(2) 5/2 , 4 I 15/2 ) M ( 2 P 3/2 , 2 P 3/2 ) taking place within f -states of Er 3+ ions finally populating the emitting 2 P 3/2 state.     

超精细能级中~(133)Cs激发态|6~2P_(3/2)F〉(F=2,3,4,5)原子与理想金属表面间范德瓦尔斯作用系数C_3的估算

利用碱金属原子与理想金属表面间范德瓦尔斯(vd W)作用势和不可约张量方法,计算~(133)Cs激发态|6~2P_(3/2)F〉(F=2,3,4,5)原子超精细结构的C_3系数.数值分别为:4.338 5 k Hz·μm~3、4.361 9 k Hz·μm~3、4.368 0及4.346 7 k Hz·μm~3.与其它理论数据和实验数据比较,结果表明本文所得到的~(133)Cs激发态|6~2P_(3/2)F〉(F=2,3,4,5)原子的C_3数值是可靠的.     

F8BT：P3HT共混薄膜的放大自发辐射

研究了聚合物poly（9,9-dioctylfluorene-co-benzothiadiazole）（F8BT）和poly （3-hexylthiophene）（P3HT）共混薄膜的放大自发辐射（ASE）现象,对影响其阈值的两个因素--增益和损耗进行了详细的研究。结果显示,共混聚合物的发光效率随着P3HT所占比例的增加有所降低。当P3HT比例低于20%时,发光效率降低不多,而其损耗则随着P3HT的增加显著减小。F8BT和P3HT混合后,光损耗系数从7.8 cm^-1下降到4 cm^-1左右。这表明F8BT：P3HT共混聚合物光波导的ASE阈值降低主要是由于其损耗的降低而导致的。ASE阈值的降低预示该材料体系容易实现电泵浦激光。     

电子通量对ZnO/K2SiO3热控涂层光学性能的影响

 研究了电子通量对ZnO/K₂SiO₃热控涂层光学性能的影响。分别采用通量为5×10¹¹/cm²·s，8×10¹¹/cm²·s，1×10¹²/cm²·s 和5×10¹²/cm²·s的电子对试样进行辐照。电子辐照下涂层的光学性能发生了退化，并且发现了退化涂层在空气中的“漂白”现象。分析了ZnO/K₂SiO₃热控涂层光学性能的退化机制，同时讨论了电子通量对太阳光谱吸收系数的影响。实验结果发现，在5×10¹¹～1×10¹²/cm²·s的电子通量范围内，电子通量对ZnO/K₂SiO³热控涂层光学性能的影响相同。因此在这个电子通量范围内，采用加速地面试验来模拟空间的电子辐照效应是有效的。     

Thermal and Spectrophotometric Analysis of Liquid Crystal 8CB/8OCB Mixtures

The binary system of 4-octyl-4′-cyanobiphenyl (8CB) and 4-octyloxy-4′-cyanobiphenyl (8OCB) has been studied by means of differential scanning calorimetry (DSC) and ultraviolet absorption spectrophotometry (UV). The phase-transition temperatures, enthalpies, and entropies have been determined by using calorimetric methods on DSC. The results indicate clearly the existence of three-phase regions across the crystalline-to-smectic A, smectic A-to-nematic, and nematic-to-isotropic transitions in the 8CB/8OCB mixtures. The obtained phase-transition temperatures of the 8CB/8OCB mixtures are between the data for 8CB and 8OCB. A few of the phase transitions cannot be observed at high heating rates. The phase-transition temperatures of the 8CB/8OCB mixtures rise with the heating rate between 2°C/min and 15°C/min. The activation energies were calculated by the Ozawa method for the phase transitions of 25% 8CB and 75% 8OCB liquid crystal mixtures. UV experiments were carried out to characterize the absorptivity constants of liquid crystal and their mixtures. The molar absorptivity and maximum absorption wavelengths were measured in chloroform solution by UV spectrophotometry. The maximum absorption wavelength of the 8CB/8OCB mixtures increases with decreasing percent weight of 8CB in 8OCB, a result associated with the different lengths of the alkyl chain.     

F8BT薄膜表面形貌及与Al形成界面的电子结构和反应

基于共轭聚合物光电器件的性能与聚合物的表面形貌、分子取向、以及与金属电极形成的界面结构密切相关. 本文利用原子力显微镜(AFM)、同步辐射光电子能谱(SRPES)和近边X射线吸收精细结构谱(NEXAFS)等, 研究了聚(9, 9-二辛基芴并苯噻二唑)(F8BT)薄膜的表面形貌、分子取向及其与Al 电极形成界面过程的结构变化. 结果表明, 在略低于F8BT玻璃转变温度(T_g=130 ℃)条件下对F8BT薄膜进行退火, 可明显增加薄膜的表面粗糙度, 薄膜中F8BT 的分子取向角约为49°, 9, 9-二辛基芴单元(F8)与苯噻唑单元(BT)几乎在同一平面. 在Al/F8BT 界面形成过程中, Al与F8BT中的C, N和S均发生不同程度的化学反应, 并导致价带结构和未占据分子轨道(LUMO)态密度的变化. Al对F8BT进行n型掺杂引起F8BT能带弯曲的同时, 未占据能级被部分占据, 更多的电子将被注入到LUMO+1中. 通过考察价带电子结构、芯能级位移及二次截止边的变化, 绘制了清晰的Al/F8BT界面能级图.     

Photoabsorption spectra of CF3I and thermally dissociated CF3I near the C 1s, I 3d and F 1s ionisation thresholds

We report soft X-ray total ion yield and angular-resolved ion yield spectra of CF₃I in the C 1s, I 3d and F 1s ionisation regions, and tentatively assign the observed electronic states. Anisotropy in ion yield is observed only for the C transition, indicating that the dipole moment for this transition is parallel to the C_3v. The effusive source of CF₃I is heated to 800 K to produce a mixture of CF₃ and I, and the resulting spectra are compared to those recorded at room temperature.     

EuCl3.6H2O中Eu^3＋的^5D0—^7F0跃迁的“反常”温度效应及其跃迁机制研究

研究了ＥｕＣｌ３．６Ｈ２Ｏ的Ｅｕ＾３＋的＾５Ｄ０－＾６Ｆ０“禁戒”跃迁的机制有其“反常”温度效应。通过比较没温度下荧光光谱中＾５Ｄ０－＾６跃迁和＾５Ｄ０－＾７Ｆ０跃迁第一条谱线的强度比，发现由于晶格振动，＾７Ｆ２态通过四个频率为２４５ｃｍ－１的声子与＾７Ｆ０态耦合，使＾７Ｆ０态成为混合态，因而使＾５Ｄ０－＾７Ｆ－的跃迁成为可能，并且其振子强度随温度的变化而变化。     

Ionization and Breakdown in SF6-Air and Freon-Nitrogen Mixtures

The sparking potentials and swarm coefficients (ionization and attachment coefficients) have been measured in sulphurhexafluoride- air and freon-nitrogen mixtures over the range of 110 ? E/p ? 240 V cm-1 torr-l and gas pressures varying between 1 and 20 torr, at 20°C. Addition of strongly attaching salphur-hexafluoride and freon gases increased the sparking potentials and the rate of increase of the attachment coefficient with increasing percentage of the strongly attaching gases in the mixtures was much larger than the rate of change of the first ionization coefficient.     

Hyperfine structure measurements in the ground states4 F 3/2,4 F 5/2 and4 F 7/2 of Ta181 with the atomic beam magnetic resonance method

Applying a recently developed evaporation technique for refractory elements the following results have been obtained for Ta¹⁸¹ in an atomic beam magnetic resonance experiment studying the hyperfine structure of 3 levels of the ground state multiplet⁴ F: $$\begin{gathered} g_J (^4 F_{3/2} ) = 0.45024 (4) \hfill \\ \Delta v (^4 F_{3/2} ;F = 5 \leftrightarrow F = 4) = 1822.389 (6) MHz \hfill \\ \Delta v (^4 F_{3/2} ;F = 4 \leftrightarrow F = 3) = 2325.537 (2) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 6 \leftrightarrow F = 5) = 1451.476 (7) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 5 \leftrightarrow F = 4) = 1537.530 (8) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 4 \leftrightarrow F = 3) = 1444.685 (2) MHz \hfill \\ \Delta v (^4 F_{7/2} ;F = 4 \leftrightarrow F = 3) = 1218.372 (2) MHz. \hfill \\ \end{gathered}$$ From these measurements the following constants of the magnetic dipole interaction (A) and the electric quadrupole interaction (B) have been derived: $$\begin{gathered} A (^4 F_{3/2} ) = 509.0801 (8) MHz \hfill \\ B (^4 F_{3/2} ) = - 1012.251 (8) MHz \hfill \\ A (^4 F_{5/2} ) = 313.4681 (8) MHz \hfill \\ B (^4 F_{5/2} ) = - 834.820 (12) MHz. \hfill \\ \end{gathered}$$      

State of and prospects for XeF(C−A) optically pumped lasers

Experimental and theoretical results are presented on an XeF(C?A) blue-green laser driven by 5-kJ energy. The laser was pumped by a ferrite-induced discharge of 90 cm in length. The output energy of 0.22 J was obtained with a plane-parallel resonator. A program to simulate laser operation has been developed. Numerical results for a wide range of conditions are compared with experiments performed by us and by other authors. It is found that intracavity refractive losses limit laser operation for XeF pressures above 3 torr. The laser efficiency strongly depends on the discharge-to-cavity length ratio. Possible ways to increase the laser power and efficiency are discussed.     

KAlF4：Ce,Tb磷光体的发光特性及Ce^3＋对Tb^3＋的敏化作用

采用溶液反应法和高温固相反应法合成了ＫＡ１Ｆ４基质化合物及ＫＡ１Ｆ：Ｃｅ，Ｔｂ磷光体，测定了磷光体的激发光谱和发射光谱，研究了在碱金属氟铝酸盐基质中Ｃｅ＾３＋对Ｔｂ＾３＋的能量传递，根据Ｃｅ＾３＋，Ｔｂ＾３＋在ＫＡｌＦ４中的能级关系，分析了其发光特性和Ｃｅ＾３＋对Ｔｂ＾３＋能量传递过程。     

New far infrared laser lines in optically pumped CD3F

Summary Using a high pressure CO₂-laser we have studied laser action in¹²CD₃F stimulated by R-branch pumping. We used an arrangement with low-feedback mirrors as suitable for Raman laser action. However, no Raman laser action has been observed in¹²CD₃F though similar experimental conditions were met as for¹²CH₃F and¹³CH₃F. The reason for the different behavior of the gases is not yet clear.Instead of Raman laser action we found 15 FIR resonant laser lines with 13 of them unknown up to now in the frequency range from 50 cm^–1 to 68 cm^–1. We reached FIR pulse energies up to 900 J, corresponding to a photon conversion efficiency of 12%. For our arrangement the optimum operation pressure varied from 40 torr at low J values (J=36) to 70 torr at high J values (J=49).