Rapid growth of ultra thin SiO2 films by a large-area electron beam

Rapid growth of ultra thin oxide films (40–180Å) of silicon using a low-energy large-area electron beam has been performed with a pressure ratio of 31 (O₂/He) and a total pressure of 0.5–0.7 Torr. A higher oxidation rate of about 625Ų/s is found for shorter irradiation time of the e-beam in the e-beam dose range 0.75–3 Coulomb/cm² and at lower substrate temperature 540–740°C. AES and XPS demonstrated a rapid electron-stimulated oxidation process of the Si surface. For the grown ultra thin oxide films, C-V characteristics, dielectric strength, uniformity of the film over the entire Si wafer and its thickness as a function of the processing time of the e-beam are also presented.     

NiMnGa nanostructures produced by electron beam lithography and Ar-ion etching

The technologies of electron beam lithography, dry etching and systems integration are investigated to fabricate a series of Ni-Mn-Ga double-beam structures designed with decreasing critical dimensions of 10 μm, 1 μm and 400 nm. Ni-Mn-Ga thin films of 1 μm thickness are deposited by magnetron sputtering and heat-treated in free-standing condition after selective removal of the substrate. Differential scanning calorimetry and electrical resistance measurements on the films show the characteristic features of martensitic transformation above room temperature. First optical beam deflection experiments demonstrate the magnetic and thermal actuation performance of the double-beam structures.     

Effect of electron and optical factors on the beam extraction coefficient of large-area electron accelerators

A combined numerical-analytical model for the electron-optical system of a large-area accelerator is suggested. The model is used to analyze various electron and optical factors that affect the beam extraction coefficient. To find ways of improving the beam extraction coefficient, the spatial and angular characteristics of the beam are calculated in various cross sections. The effect of the magnetic field produced by the cathode filament current is studied in detail for the first time.     

Freestanding circular GaN grating fabricated by fast-atom beam etching

We report here a top-down process for fabricating a freestanding circular GaN grating. The circular gratings are defined by electron-beam lithography and realized by fast-atom beam (FAB) etching. The silicon substrate below the GaN grating region is completely removed to make the circular grating suspended in space. The optical responses of the fabricated GaN gratings are characterized in reflectance measurements. The polarization-independent responses of circular gratings are experimentally demonstrated, corresponding well with the theoretical prediction. This work represents an important step in combining GaN-based material with freestanding nanostructures.     

High-rate laser-direct-write dry etching of titanium

Titanium surfaces can be etched spatially selective in a chlorine atmosphere under 488 nm cw Ar⁺-laser irradiation focused to 3 m with well-controlled etch depth and high etch rate. By scanning the substrate, patterns can be generated by laser direct writing with high scan speed. The dependence of the etch rate on various parameters, such as laser power, scan speed and chlorine pressure, is described, and the impact on three-dimensional structuring of titanium is discussed.     

Development of dry polymer electrolyte based on polyethylene oxide with co-bridging agent crosslinked by electron beam

Polyethylene oxide (PEO)-based electrolytes were crosslinked using electron beam (EB) irradiation. The gel contents of a polymer film were increased after irradiation doses of 0, 140, 280, and 420 kGy, with ionic conductivities of 0.831, 1.55, 6.08, and 7.95 (× 10^? 5) S cm^? 1 at 40 °C, respectively. The slight decrease in conductivity at higher temperatures after irradiation is due to the retardation of polymer motion by crosslinking. The electrolyte with higher EB dose amount exhibits higher conductivity due to stabilization of the amorphous state. The EB crosslinking with a co-bridging agent shows enhanced conductivities of 4.71, 6.59, and 7.18 (× 10^? 5) S cm^? 1 at 40 °C, after irradiation with 140, 280, and 420 kGy. Addition of the co-bridging agent is effective for developing a crosslinked structure with a smaller EB dose. Tensile strength becomes two to three times higher with irradiation compared to the non-treated polymer. Combination of the EB technique with a co-bridging agent is a simple and effective method to prepare strong dry polymer electrolyte films with improved room temperature conductivity.     

Level inversion by excitation with a monoenergetic electron beam

The efficiency of level excitation with a monoenergetic electronic beam has been studied and compared with plasma excitation. The ratio of the 3s₂ and 2p₄ level populations of neon excited by a monokinetic beam was found to be three times higher than for plasma excitation. This result is in satisfactory agreement with theory.     

带状束高功率微波源宽通带收集极

设计了一种适用于带状电子束高功率微波源的宽通带收集极,在有效吸收束-波相互作用后的带状电子束的同时,保证了带状电子束高功率微波源的工作模式矩形波导TM11模式高效率地通过。研究结果表明：在13~27 GHz范围内,功率传输效率大于95%,这一宽通带特性使得该类型的收集极与带状电子束高功率微波源能够更好配合,显著提高了微波源的模拟优化和实验调试效率;TM11模式微波的传输效率对收集极厚度和长度等参数不敏感;该类型收集极结构具有良好的散热能力,在不加外部水冷装置的条件下,仅靠空气自然对流冷却和辐射冷却,可以承受电流3 kA、电压300 kV、脉冲宽度30 ns及重复频率50 Hz带状电子束的连续冲击。     

Wiggler磁场聚焦带状电子注

 带状电子注在螺线管磁场作用下传输时,易形成Diocotron不稳定性,导致电子注崩溃。采用Wiggler磁场聚焦带状电子注能防止Diocotron不稳定性。研究了Wiggler磁场聚焦带状注的作用机理,得出带状电子注在Wiggler场作用下的包络方程。结合理论分析,使用3维粒子模拟程序对带状电子注的Diocotron不稳定性和Wiggler磁场抑制不稳定性分别进行了模拟。研究表明:合适的选择磁场大小和周期能有效抑制Diocotron不稳定性,使得设计带状电子注行波管成为可能。     

Surface energy modification by electron beam

We observe a pronounced variation of wettability properties in solid state materials induced by a low-energy electron beam. The phenomenon occurs in several stages characterized by various mechanisms. We show that for low electron doses the irradiation leads to decrease in the wetting of a dielectric surface due to induced surface electric potential. The higher electron charge leads to formation of a chemical monolayer on material’s surface. It has been found that the electron irradiation strongly modifies the surface free energy of SiO₂ by decreasing its total surface free energy value, almost twice. However, electron-induced variations of dispersive and polar components of the surface free energy are quite different and depend of incident electron charge.     

Laser-induced dry etching of integrated InP microlenses

Received: 4 June 1997/Accepted: 13 June 1997     

Photoluminescence detection of impurities introduced in silicon by dry etching processes

We report on a photoluminescence study of silicon samples subjected to different dry etching processes. Several luminescence lines, known from defects produced by high-energy irradiation, manifest damage of the crystalline material. Noble gas ion beam etching (using Ne⁺, Ar⁺, Kr⁺, and Xe⁺) with ion energies as low as 400 eV produces characteristic luminescence lines which correspond to defects within a 200–300 Å thick surface layer. Incorporation of carbon during CF₄ reactive ion etching produces the familiar G-line defect. The G-line photoluminescence intensity in our samples is directly correlated with the substitutional carbon concentration, as determined by infrared absorption measurements before the etch process; we therefore suggest that a simple method to determine the substitutional carbon concentration in a crystalline silicon sample is a standard dry etching process and a comparison of the resulting G-line photoluminescence intensity to a calibrated sample. The sensitivity of this method seems to be better than 10¹⁴ carbon atoms/cm³.     

Parametric instabilities produced by a relativistic electron beam in a plasma

The parametric instability driven by the primary spectrum of the hydrodynamic two-stream instability produced by a relativistic electron beam in a plasma is investigated. The saturated level of the primary wave electric field is determined by electron trapping in the potential well of the wave or by the quasilinear beam relaxation process. After saturation, the primary wave collapses by way of the oscillating two-stream instability. The cases of the strong and weak primary electric field in comparison with the thermal energy of a plasma are considered. For a strong field the growth rates of the parametric instability and plasma heating due to the latter are found. Ion heating is not significant in comparison with electron heating (approximately as the cube root of the mass ratio). In a weak field the parametric oscillating two-stream spectrum of saturation is found. In the one-dimensional case this spectrum of electric field energy fluctuations varies as k⁻² if the fluctuation field exceeds the threshold pump electric field for the oscillating two-stream instability. For the weak field plasma heating rate is found. Since the energy transfer is via Landau damping, the particle heating is characterized by the formation of high-energy tails on the distribution function.     

Hardening of steel by alloying in a relativistic electron beam

The possibility was demonstrated of hardening a steel surface layer by alloying it using the energy of relativistic electrons. Investigations were made of how the structure, hardness, and depth of the hardened layer depend on the processing regime and on the initial temperature of the steel in the case of alloying with boron carbide and with Cr+C and Cr+B₄C mixtures. The greatest hardening was achieved by alloying with a mixture of Cr and B₄C powders. This was due to a higher volume fraction of the second phase in the layer and to the precipitation of chromium carboborides. Several types of alloying utilizing Cr+B₄C and containing additional agents and modifiers were developed on the basis of the data obtained.Institute of Hardening Physics and Materials Research, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 57–63, March, 1993.     

Generating a quasiellipsoidal electron beam by 3D laser-pulse shaping

A generic 3D laser-pulse-shaping scheme is proposed towards the generation of a uniform ellipsoidal particle distribution, an ideal distribution due to the linear dependence of the space-charge force on the particle position. The shaping is accomplished via spatiotemporal coupling of the laser dynamics via chromatic aberration in an optical lens. Particle tracking simulations show that the electron beam initiated by such a laser pulse in a high-gradient radio-frequency photoinjector delivers very low emittance, ideal for beam-based light sources such as the x-ray free-electron laser.     

Generating a uniform transverse distributed electron beam along a beam line

It has been reported that transverse distribution shaping can help to further enhance the energy extraction efficiency in a terawatt, tapered X-ray free-electron laser. Thus, methods of creating and keeping an almost uniform transverse distributed(UTD) beam within undulators are required. This study shows that a UTD electron beam can be generated within evenly distributed drift sections where undulators can be placed, by means of octupoles and particular optics. A specific design is presented, and numerical simulations are performed to verify the proposed method.     

Determination of ion beam etching damage on InP by spectroscopic ellipsometry

N₂/H₂O RIBE is a new successful technique for structuring waveguides in InGaAsP/InP [B. Kempf, R. Göbel, H.W. Dinges and H. Burkhard, in: Proc. Int. Conf. on Solid State Devices and Materials, Sendai, Japan, 1990 (SSDM, Sendai, Japan, 1990) p. 477], but surface damage cannot completely be avoided. Ellipsometry offers an accurate and nondestructive tool to analyze this surface damage. The altered optical and electrical properties of the damaged layer on InP after the etching process and after the consecutive preheat process under an H₂/PH₃ gas stream prior to the epitaxial regrowth of InP in an InP VPE system are investigated by spectroscopic ellipsometry and C-V profiler measurements. ψ, Δ curves show that the preheat process leads to a complete recovery of the surface properties.     

摆动刻蚀法制作高衍射效率凸面闪耀光栅

通过摆动离子束刻蚀方法,制作了用于短波红外高光谱成像光谱仪的凸面闪耀光栅。该方法通过在光栅子午方向上进行摆动刻蚀,解决了凸面光栅子午方向的闪耀角一致性问题。建立了摆动刻蚀模型来分析摆动速度、束缝宽度等工艺参数对槽型演化的影响,并计算了优化的刻蚀工艺参数。制备了基底尺寸为67 mm,曲率半径为156.88 mm,刻线密度为45.5 gr/mm,闪耀角为2.2°的凸面闪耀光栅,并对其表面形貌及衍射效率进行了测量。实验结果表明,摆动刻蚀法能够制作出闪耀角一致性好、衍射效率高的小闪耀角凸面光栅,满足成像光谱仪对光谱分辨率和便携性的使用要求。