用于大面积材料表面改性研究的微波等离子体源

介绍了环形狭缝波导天线等离子体源的原理和结构。采用微波单探针测量了无等离子体情况下环形波导狭缝天线内的电场分布，利用Langmuir双探针测量了该源的氩等离子体的特性，结果表明在微波功率为200～600W，运行气压为40～600Pa范围内，电子温度可达0.5～3eV，离子密度最高达6×1010cm-3在气压为100Pa，等离子体的直径为16cm范围内，其不均匀性不超过25％。     

利用电子回旋共振放电提高氢原子制备效率方法研究

基态氢原子的制备是氢原子钟工作的基础,提高氢原子的生成率极为重要.针对电离泡内氢等离子体中的原子成分不易直接被探测的情况,本文将软件仿真模拟与实验光谱诊断相结合,研究泡内原子成分.采用COMSOL软件建立射频感应耦合等离子体(ICP)和微波电子回旋共振(ECR)两种放电模型,模拟了一定输入功率、不同气压下氢等离子体中原子密度的分布规律.根据仿真模型,使用ICP和ECR两种电离源在通氢的石英制电离泡内形成等离子体,测量了一定输入功率、不同气压下的辐射光谱强度.结果表明,15 W输入功率、8 Pa~14 Pa气压时,微波ECR放电产生的原子密度明显高于射频ICP放电,可知此时微波ECR放电能更高效地产生氢原子.该研究显示出微波ECR放电在氢原子钟上的应用前景.     

细长石英管内直流放电等离子体研究

利用朗缪尔双探针等离子体诊断方法,研究了细长石英管内的低气压直流放电行为,探讨了细长管空间内的放电条件对等离子体参数的影响规律。结果表明:通过提高放电功率和增加阴极数目可以有效的提高等离子体密度,且当放电气压为100 Pa时,电子密度最大,本装置所测最大密度为1.03×10~(17)m~(-3);电子温度则随着放电功率和放电气压的增大而不断减小;放电距离越远,对击穿电压要求越高,分段式放电可以在较低的放电电压下,对较远的电极距离实现直流放电。     

介质阻挡放电等离子体中HO2自由基的红外光腔衰荡光谱原位诊断

建立了一套以可调谐半导体激光器做光源的连续波光腔衰荡光谱装置，简单介绍了连续波光腔衰荡光谱技术与脉冲光腔衰荡光谱技术的区别。将连续波光腔衰荡光谱技术与介质阻挡放电等离子体技术相结合，对等离子体中的HO2自由基进行了原位定量测量，同时考察了HO2自由基数密度随放电电压和体系中氧气含量变化情况。实验结果表明：随着放电电压和体系中氧气含量的增加而增加的HO2自由基数密度分别出现极大值。     

石英板夹层中窄电极结构与材料对直流放电的影响

研究了一种石英板夹层窄电极放电装置的低气压直流放电过程,重点探讨了电极结构与电极材料对等离子体参数的影响,其中电极要求宽高为4mm,间距大于40mm。实验采用朗缪尔双探针法诊断,通过改变气压、放电功率等条件分析了电极结构对自制的直流等离子体放电装置的电子密度分布及电子温度的影响。结果表明:通过增加电极表面积,采取特殊的电极结构都可以有效地提高等离子体密度。实验中还发现,随着气压降低,正柱区逐渐缩小、等离子体密度沿电场方向变化趋于平缓,阳极的直流等离子体密度逐渐升高,这时等离子体空间分布均匀度提高,且在16Pa时取得最大值。     

射频感应耦合等离子体朗缪双探针诊断分析

采用朗缪探针法对射频感应耦合等离子体进行了诊断分析,得到了圆柱形ICP放电装置的电子密度和电子温度。通过朗缪双探针研究了不同放电气压、不同射频功率、不同放电位置、不同气体组分对等离子体参数的影响。一定功率下,电子密度在30Pa-100Pa之间随气压的增加而增大,在100Pa-160Pa之间随气压的增加而减小,电子温度在30Pa-160Pa之间随气压的增加而减小;一定气压下,电子密度在50W-1900W之间随功率的增加逐渐增大,电子温度在50W-900W之间随功率的增加而减小,在900W-1900W之间随功率的增加而增大。等离子体辉光区域不同位置的电子密度和电子温度各不相同,电子密度大的位置具有较低的电子温度。氩氮混合气体的电子密度随着气压的增加而减小,氮气在混合气体中的比例越高混合气体的电子密度越小;氩氮混合气体相比纯氩有着更高的电子温度,且氮气含量越高混合气体的电子温度也越高。     

Waveguide-surfatron型表面波等离子体源的特性研究

报道了所研制的Waveguide-surfatron型表面波等离子体源的特性,理论计算表明,激发表面波模式为m≥l模,在放电室中电磁场均匀性与等离子体的密度有关。实验结果指出,采用Ar气放电,在气压为10～1000Pa,微波功率800～1000W的范围内可形成大面(体)积(直径为160mm)等离子体,其电子温度为1～4eV,等离子体密度为10     

放电参量对射频容性耦合等离子体电子密度的影响

为了提高射频容性耦合等离子体电子密度,研究放电参量对其的影响。通过采用朗缪双探针法诊断分析了放电气压、气体组分、射频功率以及掺Hg等放电参量对圆柱形射频容性耦合等离子体放电装置的电子密度的影响。结果表明:随放电气压的增加,电子密度呈现出先增大后减小的变化,在30Pa-550Pa下,电子密度随气压的增大而增加,在550Pa-650Pa下,电子密度随气压的增大而减小;往Ar中通入一定体积分数的He,有增加等离子体电子密度的影响,且当He的体积分数为15%时,电子密度最大;等离子体电子密度随射频功率的增大而增加;向Ar中掺少量的Hg,有明显增加等离子体电子密度的效果。     

Waveguide—surfatron型表面波等离子体源的特性研究

报道了所研制的Waveguide-surfatron型表面波等离子体源的特性,理论计算表明,激发表面波模式为m≥1模,在放电室中电磁场均匀性与等离子体的密度有关。实验结果指出,采用Ar气放电,在气压为10-100Pa,微波功率800-1000W的范围内可形成大面（体）积（直径为160mm)等离子体,其电子温度为1-4eV,等离子体密度为10^10-10^11cm^-3量级,实测的等离子体密度与理论计算值基本吻合。     

表面波激发等离子体合成类金刚石薄膜的实验研究

用表面波等离子体装置进行了类金刚石薄膜的合成实验,研究了微波功率、基底负偏压和气体组成等条件对成膜的影响.用拉曼光谱和扫描电子显微镜对薄膜结构和表面形貌进行了分析,得出在100Pa的工作气压下,使用CH4放电,大功率和高偏压有利于生成质量较好的薄膜.     

Investigation of the properties of diamond-like carbon thin films deposited by single and dual-mode plasma enhanced chemical vapor deposition

In this study diamond-like carbon (DLC) films were deposited by a dual-mode (radio frequency/microwave) reactor. A mixture of hydrogen and methane was used for deposition of DLC films. The film structure, thickness, roughness, refractive index of the films and plasma elements were investigated as a function of the radio frequency (RF) and microwave (MW) power, gas ratio and substrate substance. It was shown that by increasing the H₂ content, the refractive index grows to 2.63, the growth rate decreases to 10 (nm/min) and the surface roughness drops to 0.824 nm. Taking into consideration the RF power it was found that, as the power increases, the growth rate increases to 11.6 (nm/min), the variations of the refractive index and the roughness were continuously increasing, up to a certain limit of RF power. The Raman G-band peak position was less dependent on RF power for the glass substrate than that of the Si substrate and a converse tendency exists with increasing the hydrogen content. Adding MW plasma to the RF discharge (dual-mode) leads to an increase of the thickness and roughness of the films, which is attributed to the density enhancement of ions and radicals. Also, optical emission spectroscopy is used to study the plasma elements.     

Deposition chemistry in the Cat-CVD processes of the SiH4/NH3 system

Laser spectroscopic as well as mass-spectrometric techniques were employed to examine the deposition chemistry in the catalytic chemical vapor deposition processes of the SiH₄/NH₃ system. The absolute densities of NH, NH₂ and SiH₃ radicals were measured under various conditions. The densities of the stable products, H₂ and N₂, as well as those of the reactants, NH₃ and SiH₄, were also measured. The NH₂ density is always higher than that of NH and both densities decrease by the addition of SiH₄. The SiH₃ density increases nonlinearly with the increase in the SiH₄ pressure. The SiH₃ density was found to be much higher than that of NH₂ under near practical deposition conditions to fabricate Si₃N₄ films (an NH₃ to SiH₄ flow-rate ratio of 50:1, a total pressure of 20 Pa and a catalyzer temperature of 2300 K). No aminosilane molecules were identified, suggesting that the contribution of aminosilyl radicals to the film deposition is minor. Thus, NH₂ and SiH₃ must be the major deposition species to form Si₃N₄.     

Optical emission patterns and microwave field distributions in a cylindrical microwave plasma source

A cylindrical high density (10¹² cm⁻³) large volume (32 cm in diameter and 50 cm in length) homogeneous argon plasma has been produced by a microwave with a frequency of 2.45 GHz and a power of 900 W without a magnetic field. The plasma source is based on a ring shaped rectangular waveguide with eight equally spaced slots in its inside wall. Several optical emission patterns are observed on different conditions and the microwave field is measured by a movable antenna, which showed a clear relationship between the optical emission patterns and the electron field distributions. A mode transition, from a TE_8j mode to a TE_16j mode, occurs when the gas pressure increases from 660 to 1000 Pa. And there is an optical emission pattern when the microwave power decreases from 900 to 300 W. All these phenomena are described in detail and analyzed according to the interactional theory of electrons in plasma with microwave.     

基于气动加热原理的火星大气密度传感器可行性研究

火星大气密度测量需要传感器灵敏度高、功耗低、响应时间短,为此提出了基于气动加热原理的新型传感器方案。通过对火星轨道气体流动状态进行判断、对分子与热敏器件碰撞产生的热功率密度和正压强的计算和对噪声及性能的分析,新型传感器可行性从理论上得到了论证。传感器测量火星轨道高度范围为90 km到400 km,理论热响应时间为122 ms,最小可探测压强为2.05×10-8Pa。     

PET纤维基AZO透明导电薄膜溅射工艺参数的优化

室温下,结合正交实验表,用射频磁控溅射在涤纶(PET)非织造布基材上生长AZO(Al2O3:ZnO)纳米结构薄膜.采用四探针测量仪测试AZO薄膜的方块电阻,用原子力显微镜(AFM)分析薄膜微结构;通过正交分析法对实验L9(33)AZO薄膜的性能指标进行分析.实验结果表明:溅射厚度对AZO薄膜导电性能起主导作用,其次为氩气压强和溅射功率;同时,得出制备AZO薄膜的最佳工艺为:溅射功率150W、厚度100m和气压0.2Pa,该参数下样品的方块电阻为1.633×103Ω,AZO纳米颗粒的平均直径约为69.4nm.     

Inductively coupled RF oxygen plasma characterization by optical emission spectroscopy

Optical emission spectroscopy was applied for the characterization of inductively coupled RF oxygen plasma at pressures between 10 and 300 Pa. The plasma was generated with an RF generator at a frequency of 27.12 MHz and output power of 300 W. Spectra were measured in the range 200-1100 nm by an optical spectrometer. At high pressure, the main spectral features observed were the wavelengths of the atomic oxygen transitions at 777.2 and 844.6 nm. Molecular oxygen band at 762 nm was observed as well. The atomic emission intensity showed a maximum when the pressure was about 75 Pa, while molecular band intensity increased monotonically as the total pressure increased. On decreasing the oxygen pressure, other atomic and molecular features appeared in spectra, such as H atomic lines, molecular OH band, and O₂⁺ band. The behavior of spectral features was explained by collision phenomena in the ionized gas.     

Uniform coating of CVD diamond on metallic wire substrates

Diamond was coated onto wire substrates of various transition metals (Mo, W or Ti) of 0.5 mm diameter by the microwave plasma CVD method from a gas mixture of the CO–H₂ system. The CVD conditions for a uniform diamond coating were microwave power, 750–1100 W; total pressure, 2000 Pa; total flow rate, 200 ml min-1; CO concentration, 5 vol%; treatment time, 5 h. The wire substrates were mounted vertically or horizontally on a pyrophyllite susceptor, which was placed parallel to the irradiation direction of microwave power. Homogeneous and fine-grained diamond film was prepared on the whole surface of horizontal W wire substrate with a wire height of 2 mm from the susceptor. To obtain a dense diamond coating, the height has to be as low as possible in the plasma region, where the plasma density is higher at lower substrate temperature. Low pressure and high microwave power were suited for fine-grained coating. Diamond deposition rate was found to be more dependent on pressure than substrate temperature. As the pressure increased, a glassy carbon film was formed instead of diamond. This revised version was published online in November 2006 with corrections to the Cover Date.     

LIF imaging of OH radicals in DC positive streamer coronas

In this study, the LIF detection of the hydroxyl (OH) radicals was performed in a nozzle-to-plane electrode system having an electrode gap of 30 mm during the steady-state positive streamer corona discharge at atmospheric pressure. For monitoring the ground-state OH radicals, OH transition [A² Σ⁺(v′ = 1) ← X²Π(v″ = 0)] at 282 nm was used. The time relationship between the regular streamer coronas, laser pulse, OH fluorescence and laser-induced streamer was measured. The time dependence of OH radicals between the successive streamers was measured for the evaluation of OH dynamics when the discharge was in a steady-state condition. The two-dimensional OH distribution in the DC streamer corona discharge was observed. The obtained results showed that the ground-state OH radicals were generated mainly in the filamentary part of the streamers. It was found that LIF detectable amount of ground-state OH radicals stayed in the region where streamers propagate during the steady-state DC positive streamer corona in open air.