摘要:

This review encompasses the application of the scanning electron microscope to the study and characterization of semiconductor materials and devices by the Electron Beam Induced Conductivity (EBIC) method. In this technique, the charge carriers generated by the electron beam of the microscope are collected by an electric field within the material and sensed as a current in an external circuit. When employed as the video signal of the SEM, this collected current image reveals inhomogeneities in the electrical properties of the material. The technique has been used to determine carrier lifetime, diffusion length, defect energy levels, and surface recombination velocities. Charge collection images reveal the location ofp‐njunctions, recombination sites such as dislocations and precipitates, and the presence of doping level inhomogeneities. Both the theoretical foundation and the practical aspects of these effects are discussed in a tutorial fashion in this review.

ISSN:0021-8979    

DOI:10.1063/1.331667

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

We introduce the concept of the local wavenumber and frequency spectral density, which can be estimated using spatially fixed, point data sources (’’fixed probe pairs’’), and discuss the relationship of this spectral density to the conventional wavenumber and frequency spectral density and the cross‐power spectral density. The local wavenumber and frequency spectral density is shown to be equivalent to the conventional wavenumber and frequency spectral density when the fluctuation is stationary and homogeneous and consists of a superposition of wave packets; such a fluctuation is the basic model used in many turbulence theories. A digital method for estimating the local wavenumber spectrum is described and applied to the study of drift‐wave turbulence in an rf‐excited discharge. The statistical dispersion relation and wavenumber spectral width, computed from the local wavenumber and frequency spectrum of the drift‐wave turbulence, are compared with the conventional spectral moments computed using the correlation method of Iwama and Tsukishima; good agreement is found over a wide range of frequency. A frequency‐integrated wavenumber spectrum is computed; both frequency and wavenumber spectral indices are found independently. The local wavenumber and frequency spectrum is a completely new approach to the use of fixed‐probe data, and we believe it can greatly extend the quantity of information available from fixed probes, which are the principle tools in many, if not most, fluctuation experiments.

ISSN:0021-8979    

DOI:10.1063/1.331279

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

One of the leading problems in gravitational wave detection is the construction of an optimized transducer capable of reaching the predicted sensitivity limit set by the amplifier noise. Existing transducers, when used with ultra‐low noise amplifiers, are far from this limit. In this paper, electrical tuning is proposed to improve the match between the mechanical oscillator and the amplifier in the case of an inductively coupled electromechanical transducer. A detailed calculation of the sensitivity of this device is carried out. This calculation shows substantial improvement over the untuned system. The requirement on the tuning is shown to be noncritical. The most severe requirement is the one imposed by the electrical losses in the resonating capacitor.

ISSN:0021-8979    

DOI:10.1063/1.331280

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A new method of measuring the thermal diffusivity of thin layers has been developed and applied to the characterization of laminated structures. The thermal diffusivity is measured using pyroelectric detection of a laser generated thermal pulse propagating through the sample. The shape of this pulse is governed by the thermal properties of both the sample and the detector. However, the thermal diffusivity of the sample can be determined from the position of the peak in the pyroelectric signal and the sample thickness. This method can be applied to thermal diffusivity measurements of thin or thick films, laminates, and thermal greases.

ISSN:0021-8979    

DOI:10.1063/1.331281

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

With the aim of using it in mass spectrometry, we have tried to find an axisymmetric electrostatic system with very particular characteristics, viz. reduced spherical and chromatic aberrations. We chose a system made up of three coaxial cylinders of radius &rgr;. The inner electrode is 0.90 &rgr; long and is separated from the outer cylinders (which are taken to be of infinite length) by two identical gaps of 0.40 &rgr;. This system has been studied from both the mirror and the lens point of view. The mirror is studied using two electrostatic parameters. The potentials of the three cylinders are reffered to asV1,V2, andV3. The first parameter used isRd=100 (V1−V2)/(V1−V3) and the second isV3/V1. For six values ofRd, ranging from 100 to 74, we examine the paraxial characteristics and the coefficients of spherical and chromatic aberration as a function ofV3/V1. We only deal with the area where the mirrors are convergent and where the radii of curvature do not exceed 10&rgr;. For the values ofRdstudied, other than 100, we use a field of variation from −0.10 to −0.50 forV3/V1. When we study the lens, we deal with the area where the outer potentialsV1andV3are identical. There is thus only one variable, the ratioV2/V1of the potentials of the first two cylinders. We consider two cases:V2/V1≳1 andV2/V1<1. Among the results obtained, we have chosen two groups of mirrors for which the chromatic aberration coefficientCcis null and whose radii of curvature are greater than 6.60 &rgr;, a group of mirrors for which the spherical aberration coefficientCsis null and whereCcis greatly reduced (here the radii of curvature are greater than 4.00 &rgr;), and a mirror for which bothCcandCsare null and which has a radius of curvature of 7.28 &rgr;.

ISSN:0021-8979    

DOI:10.1063/1.331282

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The elastic scattering of beam ions is shown to cause a potentially damaging flux of penetrating secondary knock‐on particles. These secondary particles will be more penetrating than the primary ions if the atomic mass of the primary is larger than the secondary. A calculation, using the specific example of helium ions incident on an absorbing material containing hydrogen, reveals that the knock‐on protons have a range greater than five times the range of the primary helium ions, and can cause a preheat problem. Thus, this effect is shown to be an important design consideration.

ISSN:0021-8979    

DOI:10.1063/1.331283

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A concept is considered for storing 10–100 MJ of electrical energy in a relatively lightweight and compact device. Energy is stored as electron kinetic energy confined in the vertical betatron field of a toroidal ring. Electrons are injected into a ring at full voltage but low current and low power. The stored electron energy is released on a fast time scale. Synchrotron radiation, wall fields, and instabilities constrain the energy that can be stored in each ring.

ISSN:0021-8979    

DOI:10.1063/1.331206

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Side‐band resonances were investigated in the radio‐frequency (rf) spectrum of free ions stored in a radio‐frequency quadrupole ion trap. The magnetic resonance signals occur at the center frequency and at the center frequency plus or minus integral multiples of the characteristic ion macromotion frequencies. The experiment was performed on3He+using the ion storage exchange collision technique. Contributions of the side‐band intensity arose predominantly from the standing microwave field inside the cavity. The effect of a small traveling wave component was also included. The microwave field was fed into the trap structure which, in addition to being used for trapping, was also employed as a broad band cavity in the TE013mode. The dependence of the intensity distribution of the side‐band spectrum on different ion motion temperatures and energy distributions of the ions was studied numerically. It was demonstrated experimentally that initially the stored ions have a uniform energy distribution. Since the stored ion cloud samples different microwave fields at different times, the induced perturbation of the microwave field is spread out in frequency and a correlation function approach is suitable to interpret the side‐band spectra. The present experiment was carried out in the microwave region where narrow‐band coherent radiation fields are readily available. However, the same side bands should also occur in the optical spectrum of stored ions and are of interest to laser cooling experiments.

ISSN:0021-8979    

DOI:10.1063/1.331284

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The classical and quantum motion of ions in a Kingdon trap (Orbitron) is studied for nearly circular orbits. The frequencies of small axial and radial oscillations are derived for both the logarithmic potential and the actual potential. A numerical comparison with the asymptotic approximation and with exact energy eigenvalues shows that the small oscillation method is adequate for most purposes.

ISSN:0021-8979    

DOI:10.1063/1.331285

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The method of separation of variables has been applied to derive the magnetic fields of four magnetostatic field problems. Three problems consist of infinitesimally thin spherical current bands and a ferromagnetic spherical shell. Two of these configurations have a magnetic spherical shell with an internal or external current band and the third has a spherical shell with both internal and external current bands. A fourth problem consists of a magnetic sphere with an external current band of finite width. Calculations of the magnetic field for sample problems are presented. The solutions are intended for analysis of the magnetizing behavior of ferromagnetic substances and have applicability in electrical machinery and magnet design.

ISSN:0021-8979    

DOI:10.1063/1.331286

出版商:AIP    

年代:1982

数据来源: AIP