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采用浓度调制光谱技术研究了连续交流放电产生的氮等离子体喷束。当放电峰峰电压VPP大于9.6kV时,氮离子以脉冲形式产生,每个放电电压周期产生一次。此时监测到交流放电电流上有一反向电流尖峰,该电流尖峰是等离子体喷束中氮离子惯性运动形成的,其强度与浓度调制光谱的强度成正比。根据浓度调制光谱的1f/2f检测结果,提出了一个理论模型,解释了上述现象。     

Observation of self-organized square lattice pattern formation in surface barrier discharge plasma

The experimental observation of a two-dimensional self-organized square lattice pattern in a planar surface barrier discharge is reported. The discharge was operated near atmospheric pressure in helium gas. The transition from irregular plasma spot pattern to a square lattice pattern is achieved by reducing the discharge driving frequency. On increasing the driving frequency the regular lattice pattern is destroyed and again transforms to an irregular plasma spot pattern. Dielectric degradation and powder formation is also observed after discharge process. Spatio-temporal behavior of observed plasma pattern is presented.     

Yet another contribution to the question of the stabilization of an extended glow discharge in a transverse gas flow

The instability of a discharge in a transverse gas flow is studied experimentally. It is shown that the characteristics of the source influence the stability. Zh. Tekh. Fiz. 69, 38–41 (December 1999)     

氩直流辉光放电等离子体中电子运动及能量的模拟

采用自动调节时间步长的蒙特卡罗模拟,对平行板放电系统中的氩气直流辉光放电系统中的等离子体区内电子的运动过程进行了跟踪和抽样。统计结果表明:在我们的实验条件下,等离子体中的电子在电场作用下出现明显的轴向漂移;在40000次抽样中,出现能量为E的电子数目随能量E增大呈下降趋势,场强增大将引起能量分布展宽和电子平均能量增加;即使场强达到15V·cm-1,等离子体激发和电离仍是很少的;场强和气压都能明显改变电子的平均自由程。     

Determination of the concentration of metastable helium atoms in an atmospheric-pressure glow discharge

The spatial distribution of the concentration of metastable helium atoms in the cathode region of an atmospheric-pressure glow discharge in helium is measured by the method of atomic-absorption spectroscopy. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 530–533, July–August, 2000.     

Impact of an ion-flux non-uniformity on the sputtering of a target with a surface relief in a glow discharge plasma

The distribution of the sputtering yield averaged over the ion energy and flux density of sputtered atoms in a glow discharge plasma on a surface with a small-amplitude periodic relief has been calculated. The average sputtering yield of the target has a minimum at tops of the relief due to the energy separation of ions within the near-electrode discharge layer, while the flux density of sputtered atoms in this case is maximized due to the higher density of the ion flux on these areas.     

Measurement of the gas temperature in a glow discharge by fluorescence spectroscopy

From the measurement of the distribution of sputtered iron atoms over the fine structure levels of the iron groundstate (a ⁵ D), the gas temperature of an argon glow discharge (p=1 Torr) has been derived under collision dominated conditions at distances larger than 30 mean free paths from the iron cathode.     

Modulation of the electronic properties of GaAs quantum wells induced by surface acoustic waves

We investigated the modulation of the optical properties of GaAs-based structures by a surface acoustic wave (SAW) by microscopic measurements of reflectance and photoluminescence. We demonstrate that for photon energies away from electronic resonances, the modulation of the optical properties is associated with the strain field of the SAW (elastooptical mechanism). Close to the E₀ resonance, the electrooptical modulation due to the SAW piezoelectric fields becomes important and leads to a spatial modulation of the photoluminescence intensity.     

强流脉冲电子束辐照诱发纯钼表面的损伤效应及结构缺陷

利用强流脉冲电子束（HCPEB）装置对纯钼表面进行辐照处理,并利用X射线衍射仪,扫描电子显微镜（SEM）、透射电子显微镜（TEM）详细分析了辐照表面的微观结构和损伤效应. 1次HCPEB辐照后,纯钼表层积聚了极大的残余应力,多次辐照后表面未融化区域出现大量绝热剪切带,且局部区域发生开裂. 微观结构分析显示,辐照后材料表面形成发散状的位错组态和大量空位簇缺陷;绝热剪切带内部是尺寸为1 μm 左右等轴状的再结晶晶粒. 剪切带造成的材料表面局部软化以及间隙原子偏聚于晶界是材料发生开裂的主要原因. 另外,表面熔化区域可形成尺寸为20 nm左右的纳米晶. 关键词： 强流脉冲电子束 纯钼 绝热剪切带 空位簇缺陷     

气体放电中正柱区电场的光谱不介入诊断

基于速度调制分子离子光谱技术，提出并实现了分别通过研究分子离子光谱强度随母体分子气压变化以及光谱线宽随放电电流变化两条途径对气体放电等离子体中电场的两种光谱不介入诊断方法，两者所获得的电场吻合较好，表明速度调制分子离子光谱方法对等离子体诊断具有十分重要的意义。     

Optical magnetic resonances induced by the interference of reactive components in the near radiation-field zone of atoms in a glow discharge of a mixture of even neon isotopes

Four types of anomalous optical magnetic resonances shifted with respect to the zero magnetic field and with different shapes are found in radiation of a glow discharge in a mixture of even neon isotopes placed in a swept longitudinal magnetic field. This testifies to the manifestation of collective processes of synchronous light emission by oscillators belonging to isotopically different spatially separated atoms in discharge plasma. The origin of resonances is associated with nonstationary interference of reactive fields in the near radiation-field zones of emission of atoms, averaged over the lifetime of the fields (interference), while different types of resonances are associated with different methods of synchronization of the phases of the fields.     

等离子体针放电的振动温度和气体温度研究

大气压等离子体针空气放电产生的低温等离子体由于脱离了真空装置,在工业上具有广泛的应用前景。本文采用等离子体针装置在空气中产生了稳定的大气压等离子体羽,并利用光谱法对等离子体羽的振动温度和气体温度进行了研究。结果发现大气压空气等离子体羽的放电区域分为强光区和弱光区。放电发光信号是宽度为几个微秒的脉冲。研究结果表明等离子体振动温度随空间位置不同在2 500～3 000K范围变化。振动温度在强光区随着远离针尖距离的增大振动温度呈上升趋势,在5mm左右存在极大值,在弱光区随着远离针尖距离的增大振动温度呈下降趋势。与其相似,弱光区放电的气体温度随着远离针尖距离增大,从640K降低到540K。这些结果对大气压空气放电的工业应用具有重要意义。     

Quantitative analysis of the surface reconstruction induced band-gap in the Shockley state on monolayer systems on noble metals

One monolayer of Ag deposited on Cu(1 1 1) shows two kinds of characteristic reconstruction, depending on the conditions of the preparation: the incommensurate moiré structure appears for one monolayer prepared at 200 K whereas a monolayer deposited at room temperature (or higher) exhibits a quasi-commensurate triangular structure. By high-resolution ARUPS measurements on the triangular structure we find an opening of a gap in the Shockley state band, which is a signature of the super-lattice. On the other hand, no gap opening is observed on the moiré structure. In addition, we show that the Shockley state plays an important role in the adsorption process of rare gas atoms on these surfaces. ARUPS experiments on adsorbed Xe on 0.6 ML Ag/Cu(1 1 1) show clearly that the Xe atoms favor the adsorption on the Ag islands, before the Cu terraces will be covered at higher Xe exposure.     

Investigating gate metal induced reduction of surface donor density in GaN/AlGaN/GaN heterostructure by electroreflectance spectroscopy

The internal field of GaN/AlGaN/GaN heterostructure on Si-substrate was investigated by varying the thickness of an undoped-GaN capping layer using electroreflectance spectroscopy. The four samples investigated are AlGaN/GaN heterostructure without a GaN cap layer (reference sample) and three other samples with GaN/AlGaN/GaN heterostructures in which the different thickness of GaN cap layer (2.7 nm, 7.5 nm, and 12.4 nm) has been considered. The sheet carrier density (n_s) of a two-dimensional electron gas has decreased significantly from 4.66 × 10¹² cm⁻² to 2.15 × 10¹² cm⁻² upon deposition of a GaN capping layer (12.4 nm) over the reference structure. Through the analysis of internal fields in each GaN capping and AlGaN barrier layers, it has been concluded that the undiminished surface donor states (n_s) of a reference structure and the reduced n_s caused by the Au gate metal are approximately 5.66 × 10¹² cm⁻² and 1.08 × 10¹² cm⁻², respectively.     

The determination of the FIR dielectric constant in a reststrahlenband by surface wave laser spectroscopy

The application of an optically pumped FIR laser to surface wave spectroscopy is described. The surface phonon polariton on CsBr was excited with a prism coupler. The optical constants of the prism material polyethylene and the sample CsBr are given for and 85.30 cm^–1.     

Stress modifications induced by dimer vacancies in the Si(0 0 1) surface: Monte Carlo simulations

By means of Monte Carlo simulations, we investigate the local stress modifications induced by dimer vacancies (DVs) in the Si(0 0 1) subsurface layers. In presence of n isolated compact DVs, the sites located below these defect rows are under clearly compressive stress in the third layer and under more and more tensile stress, as n increases, in the fourth layer. At higher DVs densities, analogous trends are observed, but the stress modifications are then slightly extended between the dimer rows. Applying our results to the Ge penetration in Si(0 0 1), we show how the knowledge of the local stress may allow predictions of a given impurity behaviour in the vicinity of the surface, provided that the impurity-defect and impurity-impurity interactions do not play a major role compared to the local stress modification induced by the presence of DVs.     

Electro-optical switching of liquid crystal diffraction gratings by using surface relief effect in the photopolymer

Surface relief patterns are one of the promising possibilities for the fabrication of liquid crystal (LC) electro-optical devices. Optically recorded surface relief gratings in an acrylamide based photopolymer were filled with the liquid crystal to fabricate liquid crystal diffraction gratings. E49 liquid crystals were used in this work. The switching behaviour of the diffraction grating was investigated by measuring the intensity in the first order when an electric field was applied.     

Experimental observation of a practical limit on enhancement of the spontaneous emission rate in blue GaN-LEDs by mediating surface plasmons

High modulation speed of light-emitting diodes (LEDs) is of primary importance for applications in optical communication. To this end, we experimentally investigated enhancement behaviors of the spontaneous emission rate (SER) of electron–hole pairs in blue InGaN/GaN LEDs by mediating surface plasmons (SPs). The coupling strength of the electron–hole recombination into SPs is controlled by etching the p-GaN layer between the active and metal layers to form thicknesses between 40 nm and 10 nm. While a tendency of increasing SER is theoretically expected for a smaller separation, the maximum value SER enhancement has a practical limit of about 2.5 at λ = 441 nm, and separation of 20 nm due to damage on the p-GaN layer caused by the etching process.     

Origin of the surface recombination centers in ZnO nanorods arrays by X-ray photoelectron spectroscopy

The surface composition of as-grown and annealed ZnO nanorods arrays (ZNAs) grown by a two-step chemical bath deposition method has been investigated by X-ray photoelectron spectroscopy (XPS). XPS confirms the presence of OH bonds and specific chemisorbed oxygen on the surface of ZNAs, as well as H bonds on surfaces which has been first time observed in the XPS spectra. The experimental results indicated that the OH and H bonds play the dominant role in facilitating surface recombination but specific chemisorbed oxygen also likely affect the surface recombination. Annealing can largely remove the OH and H bonds and transform the composition of the other chemisorbed oxygen at the surface to more closely resemble that of high temperature grown ZNAs, all of which suppresses surface recombination according to time-resolved photoluminescence measurements.     

Low frequency surface waves in the presence of an external high frequency electric field

The problem of surface sound propagation in the presence of external high frequency dipole electric field is investigated using Vlasov-Poisson equations. The structure of the electric field of these surface waves is also determined. It has been found that the ion sound waves that exist in the presence of external high frequency waves are true surface waves while those without the external field are quasi-surface waves as the former waves decay within one wavelength away from the surface.