Focused ion beam doping for GaAs MBE growth

Maskless ion implantation by scanning a focused ion beam was applied to impurity doping for GaAs growth. The implanter was combined with the MBE growth chamber in an ultrahigh vacuum (UHV). Multilayered crystals with three-dimensional, arbitrary pattern-doped regions of submicron size are grown using computer software. The through process in UHV, which eliminates air exposure during the crystal growth process, prevents carbon contamination and deterioration of crystal quality at the growth-interrupted interface for ion implantation.     

A comparison of focused ion beam and electron beam induced deposition processes

Focused ion and electron beams are used for local deposition of conducting or insulating films. Major applications are integrated circuit design edit, prototype modification, repair of masks, and machining of microsystems. In this paper, the dependence of the deposition rates versus the beam parameters for both, ion beam and electron beam induced deposition were investigated and compared with each other. At the same time, a more precise consideration of the influence of secondary electrons on the deposition process was accomplished.     

Effect of swift heavy ion (SHI) irradiation on the structural and optical properties of N implanted CVT grown ZnSe single crystals

Present study reports the variation of structural and optical properties of N implanted ZnSe single crystals grown by a Chemical Vapor Transport (CVT) technique due to120 MeV Au ion irradiation. The grazing incidence X-ray diffraction (GIXRD) results show that the full width at half maximum (FWHM) increases on irradiation. The surface morphology of irradiated sample shows the pits and islands by AFM studies. The optical absorption cut off wavelength is 493 nm for as grown ZnSe whereas for the implanted and irradiated samples cut off wavelength shift towards red region. The photoluminescence spectrum shows the emission wavelength is at 592 nm whereas for the implanted-irradiated samples PL emission shift towards red region. The intensity of defect level emission decreases due to Au irradiation. The FT-Raman spectrum shows the peak at 252 cm⁻¹ due to LO mode of Zn–Se lattice vibrations. The X-ray absorption near edge structure (XANES) study was performed for the as grown and irradiated samples. The detailed investigation on the structural and optical properties of the N implanted and Au irradiated ZnSe single crystal was carried out.     

Changes in the opto-electronic properties of CuInSe2 following ion implantation

The development of efficient thin-film solar cells based on CuInSe₂ absorber layers has encouraged fundamental research on both thin films and single crystals of this chalcopyrite semiconducting compound. The resistance to radiation and ion bombardment is of technical importance particularly for a material which could find future applications in space photovoltaic power systems. In this paper results are described for an ion implantation study using CuInSe₂ single crystal substrates. Oxygen, helium and neon implantations have produced significant changes in surface resistivity and photoconductivity. Also the near-surface regions ofn-type crystals have been type-converted top-type following ion implantation. It is apparent that the ion implantation process creates defects which affect surface state densities and recombination probabilities. In the case of oxygen there is an additional doping effect caused either by the introduction of acceptor states or by the reduction of the existing donor state population. Following implantation there appears to be an overall decrease in carrier recombination at the surface which leads to an enhanced photoconductive response.     

The development of biaxial alignment in yttria-stabilized zirconia films fabricated by ion beam assisted deposition

Yttria-stabilized zirconia (YSZ) films were deposited using ion assisted, electron beam deposition (IBAD) on Pyrex, quartz, Hastelloy, and polycrystalline zirconia substrates. Film orientation was studied as a function of IBAD fabrication conditions. Film texture from several populations of biaxially aligned grains has been observed. The ion beam is shown to induce biaxial alignment of all grain orientations. Specifically, grains with (200), (311), and (111) normal to the substrate surface are biaxially aligned. The ion beam induces biaxial alignment at all angles of incidence, not just those corresponding to YSZ channeling directions. The development of (200) biaxial alignment on Pyrex is examined as a function of thickness. Biaxially aligned IBAD YSZ films were deposited on amorphous and polycrystalline substrates without active heating. Biaxial alignment development with IBAD is shown to be consistent with a previously proposed growth and extinction model.     

Validity of the Parabolic Effective Mass Approximation in Silicon and Germanium n-MOSFETs With Different Crystal Orientations

This paper investigates the validity of the parabolic effective mass approximation (EMA), which is almost universally used to describe the size and bias-induced quantization in n-MOSFETs. In particular, we compare the EMA results with a full-band quantization approach based on the linear combination of bulk bands (LCBB) and study the most relevant quantities for the modeling of the mobility and of the on-current of the devices, namely, the minima of the 2-D subbands, the transport masses, and the electron density of states. Our study deals with both silicon and germanium n-MOSFETs with different crystal orientations and shows that, in most cases, the validity of the EMA is quite satisfactory. The LCBB approach is then used to calculate the values of the effective masses that help improve the EMA accuracy. There are crystal orientations, however, where the 2-D energy dispersion obtained by the LCBB method exhibits features that are difficult to reproduce with the EMA model.     

Fabrication of an optical directional coupler of CdTe by electron beam lithography and ion etching

Various kinds of high resolution techniques such as ion etching, chemical etching, ion implantation, and electron beam lithography are studied for fabricating CdTe optical integrated circuits. It is found that the ion-etching rate of CdTe is high and has only a small dependence on crystal orientation. A special chemical etching solution for aluminum on CdTe that does not corrode CdTe and proton implanted CdTe is used for high resolution patterning of CdTe. The smooth patterns in PMMA resist produced by an electron beam exposure is replicated deep into 2.5 μm of CdTe face through the aluminum layer. Rib guides and a rib-type optical directional coupler are fabricated from planar guides by using proton implantation which makes refractive index change on CdTe face. The two-dimensional optical confinement is observed. A coupling coefficient ofk simeq 0.39mm^-1is observed in the rib-type optical directional coupler.     

镍基单晶高温合金水导激光钻孔工艺特性研究

为了探究不同激光功率及扫描速度下水导激光加工技术对镍基单晶高温合金加工微孔的影响规律及规律形成机理。使用自主研发的水导激光加工平台对镍基单晶高温合金CMSX-4在不同激光功率及扫描速度下进行1 mm微孔的加工。然后采用白光干涉仪、扫描电子显微镜和Vision64软件获得微孔加工时间、孔径、圆度、锥度及重铸层厚度随不同激光功率及扫描速度的变化规律,并研究变化规律的形成机理。结果表明,加工时间、锥度及重铸层厚度与激光能量强度有关。随着激光能量强度的增大,加工时间缩短,锥度变小,重铸层厚度变小。孔径和圆度受激光能量强度及其在材料表面分布的影响。仅当激光能量作用范围控制在水束直径范围下时,孔径及圆度相应获得较好的加工质量。     

Electron beam and ion beam fabricated microwave switch

A combination of electron beam and ion beam techniques were used in conjunction with conventional planar technology to fabricate a junction field-effect microwave switch. A digital tape-controlled scanning electron beam was used to expose mask patterns in polymethyl methacrylate resist whose line widths (≤1 um) are inaccessible to conventional photolithography; ion beam sputtering was used to remove a thin gold undercoat from within the exposed patterns, thereby maintaining the good edge resolution; and ion implantation was used to dope the closely spaced interdigitated source and drain regions thus exposed by the preceding process steps in the gold contact mask.     

Specimen preparation for high-resolution transmission electron microscopy using focused ion beam and Ar ion milling

We have developed a focused ion beam (FIB)-Ar ion-milling technique for high-resolution transmission electron microscopy. A micrometresized specimen was mounted on a cross section of metal foil of a few micrometres thick, using FIB microsampling. Following this, a 2 degrees wedgeshaped part was made in the specimen using FIB. Finally, the specimen was milled using an Ar ion beam to remove the FIB-damaged layers. We applied the FIB-Ar ion milling technique to a CeO(2)/Gd(2)Zr(2)O(7) multilayer specimen, resulting in the crystal lattice fringes of both layers being clearly observable in comparison to a specimen finished using a Ga ion beam at an accelerating voltage of 10 kV.     

Bulk single crystal growth of silicon-germanium

Si-Ge single crystals up to 68 mm diameter and up to 17 at.% germanium were grown using a modified Czochralski technique. Pre-grown large diameter single crystal silicon seeds with various crystallographic orientations were used as templates for solidification to reduce cap crystallization time and to ensure single crystallinity at desired crystal diameters. A discussion is presented of the influences of seed preparation, crystal growing parameters and post-growth processing on the Si-Ge bulk single crystals produced using this new technique. The modified Czochralski technique described in this paper is ultimately intended for the manufacture of 100–200 mm diameter Si-Ge substrates.     

The influence of ion beam parameters on pattern resolution

In nanofabrication the generation of phonons and secondary electrons by an incoming ion in a specimen gets important in limiting the resolution of the fabricated structures. A model is presented for calculating the effect of ion beam parameters (mass and energy) on the resolution and the production yield. In this model the phonon and secondary electron effect are calculated based on results for the scattering of the ions obtained with the Monte Carlo simulation program TRIM. The fabrication resolution is simulated for implantation, sputtering and beam induced etching and beam induced deposition.

Some preliminary results are given which show that the best resolution can be obtained for ions with high mass at low energy for all discussed fabrication techniques, while even the production yield is relatively high at these parameters.     

环状平顶光束在单轴晶体中垂直于光轴的传输特性

基于光束在各向异性介质中的傍轴矢量传输理论,对环状平顶光束在单轴晶体中垂直于光轴的传输作了研究,导出了偏振场的慢变振幅表达式,并通过数值计算分析了光束的传输特性。结果表明,环状平顶光束在单轴晶体中垂直于光轴传输时,晶体的各向异性对其光强分布有较大影响,在正单轴晶体远场处ne/no值越大,光强越小,光束在xy平面内扩散越小;在负单轴晶体中传输性质则相反;随传输距离z的增加,中心光强逐渐加强,光强分布不再保持原来暗中空分布的特性。     

Experimental determination of ion density trapped by electron beam

A new probing technique has been employed to determine the ion density trapped by the potential well of an electron beam as used in microwave tubes, and unexpectedly high values of ionic charge have been found on the axis, the strong space-charge fields of which are neutralised by slow secondary electrons.     

Electron beam induced current investigations of active electrical defects in silicon due to reactive ion etching and reactive ion beam etching processes

Reactive ion etching and reactive ion beam etching are common tools for anisotropic etch processes in silicon microdevice fabrication; but, unfortunately, they also create radiation damage in the etched surface. We have studied the electrically active defects by measuring the recombination of carriers with the help of the electron beam induced current (EBIC) mode of a secondary electron microscope. We have measured the temperature behavior of the samples by annealing studies and the temperature dependent EBIC signal for several p-doped silicon wafers and obtained different shaped curves. Theoretical EBIC models developed with the assumption of a reduced net carrier concentration in the etched areas agree with our experimental results.     

Inverse‐Woodpile Photonic Band Gap Crystals with a Cubic Diamond‐like Structure Made from Single‐Crystalline Silicon

Three dimensional photonic band gap crystals with a cubic diamond‐like symmetry are fabricated. These so‐called inverse‐woodpile nanostructures consist of two perpendicular sets of pores in single‐crystal silicon wafers and are made by means of complementary metal oxide–semiconductor (CMOS)‐compatible methods. Both sets of pores have high aspect ratios and are made by deep reactive‐ion etching. The mask for the first set of pores is defined in chromium by means of deep UV scan‐and‐step technology. The mask for the second set of pores is patterned using an ion beam and carefully placed at an angle of 90° with an alignment precision of better than 30 nm. Crystals are made with pore radii between 135–186 nm with lattice parameters a = 686 and c = 488 nm such that a/c = √2; hence the structure is cubic. The crystals are characterized using scanning electron microscopy and X‐ray diffraction. By milling away slices of crystal, the pores are analyzed in detail in both directions regarding depth, radius, tapering, shape, and alignment. Using optical reflectivity it is demonstrated that the crystals have broad reflectivity peaks in the near‐infrared frequency range, which includes the telecommunication range. The strong reflectivity confirms the high quality of the photonic crystals. Furthermore the width of the reflectivity peaks agrees well with gaps in calculated photonic band structures.     

Electron channelling contrast imaging for III-nitride thin film structures

Electron channelling contrast imaging (ECCI) performed in a scanning electron microscope (SEM) is a rapid and non-destructive structural characterisation technique for imaging, identifying and quantifying extended defects in crystalline materials. In this review, we will demonstrate the application of ECCI to the characterisation of III-nitride semiconductor thin films grown on different substrates and with different crystal orientations. We will briefly describe the history and the theory behind electron channelling and the experimental setup and conditions required to perform ECCI. We will discuss the advantages of using ECCI, especially in combination with other SEM based techniques, such as cathodoluminescence imaging. The challenges in using ECCI are also briefly discussed.     

无热致静态位相延迟、单块晶体结构的KNbO3和KTP电光开关

分析表明,当光在双轴晶体中波矢沿着某些特定方向传播时,不会表现出一阶热致静态位相延迟,这个方向暂时被称为晶体的无热致静态位相延迟光传播方向（ＮＴＳＰＲ方向）。根据前人发表的相关数据,采用适当近似,求得ＫＮｂＯ３的ＮＴＳＰＲ方向是（９０°,９０°±５０．１９°,５０．１９°）,ＫＴＰ的ＮＴＳＰＲ方向是（９０°±３０．７８°,９０°,３０．７８°）,并分别讨论了这两种晶体在这些方向的电光品质因数ηｅ,结果表明,利用某些双轴晶体ＮＴＳＰＲ方向大的电光品质因数制成的新型、单块晶体结构电光开关,不需要温控,而且,器件本身的通光长度可以做得更短。     

Computer simulation of ion trapping and detrapping in a PPM focusedtraveling wave tube

This paper presents results from a time-dependent, electrostatic electron gun simulation code, simulating ion trapping and detrapping in a traveling wave tube (TWT) focused by periodic permanent magnets (PPM). The simulations described indicate that ion loss is primarily radial through the beam tunnel walls, rather than axial through the gun or collector. The electrostatic potential well formed by the electron beam is constantly being filled by ionization of a background neutral gas. This effect constitutes the primary ion loss mechanism. Filling of the potential well is made possible by loss of the low energy electrons produced by ionization (secondary electrons) through periodic nulls in the magnetic field