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     

Ohmic and Schottky contacts of hydrogenated and oxygenated boron-doped single-crystal diamond with hill-like polycrystalline grains

Hill-like polycrystalline diamond grains(HPDGs) randomly emerged on a heavy boron-doped p~+ single-crystal diamond(SCD) film by prolonging the growth duration of the chemical vapor deposition process.The Raman spectral results confirm that a relatively higher boron concentration(～1.1 × 10~(21) cm~(-3)) is detected on the HPDG with respect to the SCD region(～5.4 × 10~(20) cm~(-3)).It demonstrates that the Au/SCD interface can be modulated from ohmic to Schottky contact by varying the surface from hydrogen to oxygen termination.The current-voltage curve between two HPDGs is nearly linear with either oxygen or hydrogen termination,which means that the HPDGs provide a leakage path to form an ohmic contact.There are obvious rectification characteristics between oxygen-terminated HPDGs and SCD based on the difference in boron doping levels in those regions.The results reveal that the highly boron-doped HPDGs grown in SCD can be adopted as ohmic electrodes for Hall measurement and electronic devices.     

Dependence of nitrogen vacancy color centers on nitrogen concentration in synthetic diamond

Crystallization of diamond with different nitrogen concentrations was carried out with a FeNiCo-C system at pressure of 6.5 GPa. As the nitrogen concentration in diamond increased, the color of the synthesized diamond crystals changed from colorless to yellow and finally to atrovirens (a dark green). All the Raman peaks for the obtained crystals were located at about 1330 cm^-1 and contained only the sp³ hybrid diamond phase. Based on Fourier transform infrared results, the nitrogen concentration of the colorless diamond was < 1 ppm and absorption peaks corresponding to nitrogen impurities were not detected. However, the C-center nitrogen concentration of the atrovirens diamond reached 1030 ppm and the value of A-center nitrogen was approximately 180 ppm with a characteristic absorption peak at 1282 cm^-1. Furthermore, neither the NV⁰ nor the NV^- optical color center existed in diamond crystal with nitrogen impurities of less than 1 ppm by photoluminescence measurement. However, Ni-related centers located at 695 nm and 793.6 nm were observed in colorless diamond. The NE8 color center at 793.6 nm has more potential for application than the common NV centers. NV⁰ and NV^- optical color centers coexist in diamond without any additives in the synthesis system. Importantly, only the NV^- color center was noticed in diamond with a higher nitrogen concentration, which maximized optimization of the NV^-/NV⁰ ratio in the diamond structure. This study has provided a new way to prepare diamond containing only NV^- optical color centers.     

宽带腔增强吸收光谱技术应用于痕量气体探测及气溶胶消光系数测量

基于氙灯的非相干宽带腔增强吸收光谱系统, 并将其应用于痕量气体及气溶胶消光系数的测量. 该系统的探测灵敏度通过测量NO₂在520—560 nm波长范围内的吸收得到验证, 最小可探测灵敏度为1.8× 10^-7cm^-1 (1σ, 0.12 s积分时间, 50次平均), 对应的NO₂探测极限～33 nmol/mol. 结合标准气溶胶粒子发生系统, 测量了不同浓度的单分散硫酸铵气溶胶粒子在532 nm波长处的消光系数, 得到粒径为600 nm的硫酸铵气溶胶的消光截面为1.12× 10^-8cm², 与文献报道值1.167× 10^-8cm²相一致, 验证了气溶胶测量的可行性和准确性.     

PHOTO-ACOUSTIC MEASUREMENTS OF WATER VAPOR ABSORPTION COEFFICIENT IN UV SPECTRAL REGION

Data on the absorption coefficient of H₂O in binary mixture with N₂ in UV region of spectra are presented. With the use of the high sensitivity photoacoustic spectrometer, the following values of the absorption coefficient were found: 2.3×10^-9cm^-1·Pa^-1(λ=255 nm), 0.9×10^-9 cm^-1·Pa^-1(λ=271 nm), and 1.6×10^-9cm^-1 ·Pa^-1(λ=289 nm).     

流延法制备高锂离子电导Li_(1.4)Al_(0.4)Ti_(1.6)(PO_4)_3固态电解质及其环氧树脂改性

以溶胶凝胶法合成的高纯Li_(1.4)Al_(0.4)Ti_(1.6)(PO_4)_3(LATP)纳米晶体粉末为原料,通过流延法成膜,在950℃下煅烧5 h合成LATP固态电解质片;对其进行环氧树脂改性后,能量色散X射线光谱元素图像表明环氧树脂完全浸入LATP内部,可以有效防止水渗透.研究发现流延法合成的LATP固态电解质在25℃?C时电导率高达8.70×10~(-4)S·cm~(-1)、活化能为0.36 eV、相对密度为89.5%.经过环氧树脂改性后电导率仍高达3.35×10-4S·cm-1、活化能为0.34 e V、相对密度为93.0%.高电导隔水的环氧树脂改性LATP固态电解质可作为锂金属保护薄膜用于新型高比容量电池.     

用Z-扫描技术研究卟啉铜偶合TiO2/SiO2有机-无机材料的非线性吸收特性

应用溶胶-凝胶技术, 成功地把5,10,15,20-四(4-磺酸苯基)卟啉铜掺杂到SiO₂/TiO₂无机凝胶中, 制备成有机-无机复合材料. 采用开孔Z-扫描技术, 使用波长532 nm、脉宽7ns的YAG脉冲激光为光源, 测定了不同浓度卟啉铜掺杂的SiO₂/TiO₂凝胶Z-扫描曲线. 应用Z扫描理论对获得的曲线进行分析与理论拟合, 得到复合材料的非线性吸收系数. 这些非线性吸收是由材料中卟啉铜的单聚体与二聚体的反饱和吸收所引起. 研究表明, 随着掺杂浓度的增大, 复合材料的非线性吸收明显增强. 掺杂浓度为1.11×10^-4 (A2), 1.48×10^-4 (A3)与3.01×10^-4 mol/L (A4)凝胶的非线性吸收系数分别为1.705×10^-11, 1.892×10^-11和4.854×10^-11 m/W. 讨论了单聚体与二聚体的浓度变化对非线性吸收的影响. 随着掺杂浓度的增加, 凝胶中二聚体与多聚体含量的增加, 导致非线性吸收系数的增大. 同时测定了无机材料对该光源的抗激光损伤阈值为～5 J/cm².     

Er~(3+)掺杂Na_5Lu_9F_(32)单晶体的红外光学特性

采用坩埚下降法成功地生长了Er~(3+)离子掺杂的Na_5Lu_9F_(32)(NLF)单晶体。测定了单晶体在400~2 500nm波段的吸收光谱与2.5~25μm红外波段的透过光谱。Na_5Lu_9F_(32)单晶体在400~7 150 nm宽波段范围具有好的光学透过性,在该波段的透过率达到90%。在透过光谱中几乎观察不到2.7μm中红外波段的吸收,说明单晶体中OH~-离子的含量极低。根据测定的吸收光谱,通过Judd-Ofelt理论计算了Er~(3+)在单晶体中的光学强度参数Ω_t(Ω_2=2.08,Ω_4=2.07,Ω_6=0.75),以及相应的辐射跃迁速率、荧光分支比和荧光寿命。根据Futchbauer-Ladenburg公式估算了样品的发射截面大约分别为1.42×10~(-20)cm~2(~4I_(13/2)→~4I_(15/2))和1.66×10~(-20)cm~2(~4I_(11/2)→~4I_(13/2))。在980 nm半导体激光器(LD)激发下,研究了单晶体的近红外1.5μm与中红外2.7μm的发射光谱特性。     

Near-infrared absorptions of monomethylhydrazine

The peak absorption coefficients for two near-infrared absorptions of monomethylhydrazine, CH₃-N₂H₃, (MMH) were measured. Absorption bands located at 1.524 μm (6560 cm^-1), 1.557 μm (6423 cm^-1), and 1.583 μm (6316 cm^-1) are assigned to the υ = 2 overtones of the infrared N-H stretching fundamentals at 3317, 3245 and 3177 cm^-1. An absorption band located at 1.04 μm (9620±100 cm^-1) is assigned to the υ = 3 overtone of one of these fundamentals. The peak absorption coefficients (₁₀) at 1.524 μm (6560±20 cm^-1) and 1.04 μm (9620±100 cm^-1) are 31 × 10^-3 and 0.97 × 10^-3 (cm atm)^-1, respectively. Uncertainties in these coefficients were estimated to be less than ±20% due primarily to uncertainties in the partial vapor pressure of MMH.     

High density electron-hole plasma in Si induced by femtosecond pulses

High electron and hole (e-h) densities of about 10²² cm^-3 have been produced in silicon, using 620 nm wavelength laser pulses of 100 fs duration. These density values are determined by measuring the dependence of the pulse self-reflectivity on its energy. By comparison with a fully non-linear model of light propagation, we show that dissipation processes inside the plasma are dominated by e-h collisions, with a characteristic time of 3 × 10^-16s. The onset of melting within 100 fs and its nature, considering the high plasma density, are also discussed in view of scattered light measurements.     

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.     

Neutral copper vapor density and electric recovery after forcedextinction of vacuum arcs

Dielectric recovery data were obtained for vacuum arcs between chromium copper butt contacts 30 mm in diameter and 2 mm apart. The 50-Hz arc current was forced to zero at its maximum of 200 A in about 1 μs. Following current zero, high-voltage pulses of a sufficient amplitude to always cause breakdown were applied to the gap. Gap recovery is characterized by the measured breakdown voltage as a function of time. Dielectric strength of the gap rises sharply within the first few microseconds after current zero, reaching its final value in about 10 μs. Neutral copper concentration in the center of the gap was measured by laser-induced fluorescence under conditions very similar to those of the recovery measurements. In contrast to the fast gap recovery, the copper vapor concentration does not change substantially during the first 100 μs from its value of 1.4×10¹⁸ m ^-3 near current zero. It is concluded that the neutral copper vapor concentration does not play a decisive role in gap recovery under these experimental conditions. This is corroborated by the fact that the mean free path for electron-impact ionization of copper atoms exceeds the gap length by four orders of magnitude     

LaTiO高k栅介质Ge MOS电容电特性及Ti含量优化

采用共反应溅射法将Ti添加到La_2O_3中,制备了LaTiO/Ge金属-氧化物-半导体电容,并就Ti含量对器件电特性的影响进行了仔细研究.由于Ti-基氧化物具有极高的介电常数,LaTiO栅介质能够获得高k值;然而由于界面/近界面缺陷随着Ti含量的升高而增加,添加Ti使界面质量恶化,进而使栅极漏电流增大、器件可靠性降低.因此,为了在器件电特性之间实现协调,对Ti含量进行优化显得尤为重要.就所研究的Ti/La_2O_3比率而言,18.4%的Ti/La_2O_3比率最合适.该比率导致器件呈现出高k值(22.7)、低D_(it)(5.5×10~(11)eV~(-1)·cm~(-2))、可接受的J_g(V_g=1V,J_g=7.1×10~(-3)A·cm~(-2))和良好的器件可靠性.     

Nonlinear Optical Properties of Semiconductor-Doped Sol-Gel Waveguides

Thin silica-titania films doped with CdS and PbS nanocrystals have been prepared by the sol-gel route. Their nonlinear properties have been studied using the techniques of degenerated four-wave mixing and m-lines with picosecond (ps) and nanosecond laser pulses. Depending on wavelength, doping level, and laser pulse duration, high negative nonlinearity was found for CdS-doped (n₂ = -2 x 10^-8 cm² per kW) and PbS-doped films (-10^-10 to -2 x 10^-7 cm² per kW). The response time of the nonlinearity was below 35 ps. Saturation of the nonlinearity was observed. Straight, monomode channel waveguides have been fabricated on these films. The influence of MIE-scattering due to the nanoparticles is investigated.     

不同织构CVD金刚石膜的Hall效应特性

采用热丝化学气相沉积法在p型硅衬底上制备了不同织构的多晶金刚石膜,使用XRD表征了CVD金刚石膜的结构特征, 研究了退火后不同织构金刚石膜的电流特性, 使用Hall效应检测仪研究了金刚石膜的霍尔效应特性及随温度变化的规律, 结果表明所制备的金刚石膜是p型材料, 载流子浓度随着温度的降低而增加, 迁移率随着温度的降低而减小. 室温下[100]织构金刚石薄膜的载流子浓度和迁移率分别为4.3×10⁴ cm^-3和76.5 cm²/V·s.     

Carrier relaxation in InGaAs

A modelocked Nd: YAG pumped optical parametric amplifier providing 35 ps pulses in the wavelength range λ = 1.45−2.1 μm has been used to study photoexcited carrier recombination in InGaAs. At carrier densities in excess of 10¹⁸ cm^-3 Auger processes are found to dominate the carrier recombination. An Auger rate of 2.5±0.5×10^-28 cm⁶ s^-1 is determined.     

氧离子注入微晶金刚石薄膜的微结构与光电性能研究

本文系统研究了氧离子注入剂量和退火温度对含有Si-V发光中 心的微晶金刚石薄膜的微结构和光电性能的影响. 结果表明, 氧离子注入并在较高温度退火有利于提高薄膜中Si-V中心的发光强度. 当氧离子注入剂量从10¹⁴ cm^-2增加到10¹⁵ cm^-2时, 薄膜中Si-V发光强度增强. Hall效应测试结果表明退火后薄膜的面电阻率降低. 不同温度退火时, 氧离子注入薄膜的Si-V发光强度较强时, 薄膜的面电阻率增加, 说明Si-V发光中心不利于提高薄膜的导电性能. Raman光谱测试结果表明, 薄膜中缺陷数量的增多会增强Si-V的发光强度, 而降低薄膜的导电性能. 关键词： 金刚石薄膜 氧离子注入 电学性能 Si-V缺陷     

电离辐射对部分耗尽绝缘体上硅器件低频噪声特性的影响

本文针对辐射前后部分耗尽结构绝缘体上硅(SOI)器件的电学特性与低频噪声特性开展试验研究. 受辐射诱生埋氧化层固定电荷与界面态的影响, 当辐射总剂量达到1 M rad(Si) (1 rad = 10^-2 Gy)条件下, SOI器件背栅阈值电压从44.72 V 减小至12.88 V、表面电子有效迁移率从473.7 cm²/V·s降低至419.8 cm²/V· s、亚阈斜率从2.47 V/dec增加至3.93 V/dec; 基于辐射前后亚阈斜率及阈值电压的变化, 可提取得到辐射诱生界面态与氧化层固定电荷密度分别为5.33×10¹¹ cm^{- 2}与2.36×10¹² cm^-2. 受辐射在埋氧化层-硅界面处诱生边界陷阱、氧化层固定电荷与界面态的影响, 辐射后埋氧化层-硅界面处电子被陷阱俘获/释放的行为加剧, 造成SOI 器件背栅平带电压噪声功率谱密度由7×10^{- 10} V²·Hz^-1增加至1.8×10^-9 V² ·Hz^-1; 基于载流子数随机涨落模型可提取得到辐射前后SOI器件埋氧化层界面附近缺陷态密度之和约为1.42×10¹⁷ cm^-3·eV^-1和3.66×10¹⁷ cm^-3·eV^-1. 考虑隧穿削弱因子、隧穿距离与时间常数之间关系, 本文计算得到辐射前后埋氧化层内陷阱电荷密度随空间分布的变化.     

Spectral broadening induced by intense ultra-short pulse in 4H–SiC crystals

We report the observation of spectral broadening induced by 200 femtosecond laser pulses with the repetition rate of 1 kHz at the wavelength of 532 nm in semi-insulating 4H–SiC single crystals.It is demonstrated that the full width at half maximum of output spectrum increases linearly with the light propagation length and the peak power density,reaching a maximum 870 cm~(-1)on a crystal of 19 mm long under an incident laser with a peak power density of 60.1 GW/cm~2.Such spectral broadening can be well explained by the self-phase modulation model which correlates time-dependent phase change of pulses to intensity-dependent refractive index.The nonlinear refractive index n_2 is estimated to be1.88×10~(-15)cm~2/W.The intensity-dependent refractive index is probably due to both the nonlinear optical polarizability of the bound electrons and the increase of free electrons induced by the two-photon absorption process.Super continuum spectra could arise as crystals are long enough to induce the self-focusing effect.The results show that SiC crystals may find applications in spectral broadening of high power lasers.     

Ag纳米颗粒增强的Ho~(3+)/Tm~(3+)共掺铋锗酸盐玻璃的2μm发光研究

采用基于传统熔融淬冷技术的热化学还原法制备了系列Ag纳米颗粒复合Ho3+/Tm3+共掺铋锗酸盐玻璃样品,研究了Ag纳米颗粒含量对玻璃2μm发光特性的影响.结果表明,Ag纳米颗粒的表面等离子体共振带位于500—900 nm,峰值位于650 nm,透射电子显微镜图像中观察到均匀分布的Ag纳米颗粒,尺寸约为5—10 nm.通过测试玻璃样品在1.7—2.3μm波段的荧光光谱发现,Ag掺杂后Ho3+离子2μm处的荧光强度得到了极大的提高,其中AgCl掺杂质量分数为0.3%时的荧光强度比未掺杂时的荧光强度增强10倍,这归因于Ag纳米颗粒的局域场增强作用.计算得到Ho3+离子的吸收截面为0.491×10-20cm-2,发射截面为1.03×10-20cm-2,当增益系数为0.2时即可实现正的增益.