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15 Jun 1996

Volume 79, Issue 12, pp. 8879-9403

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Single‐projection radiography for noncircular symmetries: Generalization of the Abel transform method

Shay Gueron and Moshe Deutsch

J. Appl. Phys. 79, 8879 (1996); http://dx.doi.org/10.1063/1.362665 (7 pages) | Cited 4 times

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We present a new method which extends the use of the single projection radiographic Abel method, hitherto applicable only to objects of circular and elliptical cross sections, to objects having general, noncircular symmetries. This is done by developing a new integral equation that is similar in applications to Abel’s equation, and includes it as a special case. The use of the new equation is discussed for objects having a smooth and convex cross‐section boundary (e.g., elliptic), a piecewise smooth convex boundary (e.g., bi‐parabolic), and a boundary with regions of zero curvature (e.g., polygons). Specific examples are given for each of these three classes, and analytic inverses are calculated for these cases. Also, numerical inversion of the integral equation is given, showing satisfactory results. We show that in contrast to Abel’s equation in many cases the kernel of the integral equation is non‐singular. Consequently, fairly simple inversion techniques are sufficient. Finally, the azimuthal variation of the transmitted intensity is employed to provide a convenient and fast nondestructive evaluation test of the deviation of the radiographed object from a prescribed symmetry. © 1996 American Institute of Physics.
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81.70.-q Methods of materials testing and analysis
07.85.-m X- and γ-ray instruments
87.59.B- Radiography

Cross section measurements of the 1H(3He,1H)3He reaction at 20° and 30° between 1.9 and 3.0 MeV

G. Terwagne, G. G. Ross, and L. Leblanc

J. Appl. Phys. 79, 8886 (1996); http://dx.doi.org/10.1063/1.362618 (6 pages)

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The cross sections of the 1H(3He,1H)3He reaction have been measured at two different angles (20° and 30°) for 3He particles incident energies between 1.9 and 3.0 MeV. This reaction offers an alternative to the classical 1H(4He,1H)4He elastic recoil reaction and can be more attractive because 3He incident particles induce nuclear reactions on light elements such as 12C, 14N, or 16O. The new technique has been applied to silicon implanted with low energy hydrogen as well as a CxHy/Cu/CuxHy/Si specimen. For this multilayer, carbon, hydrogen, and carbon can be analyzed together using three different charge particle detectors. © 1996 American Institute of Physics.
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25.55.Ci Elastic and inelastic scattering

A new technique for studying the Fano factor and the mean energy per ion pair in counting gases

A. Pansky, A. Breskin, and R. Chechik

J. Appl. Phys. 79, 8892 (1996); http://dx.doi.org/10.1063/1.362619 (7 pages) | Cited 4 times

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A new method is presented for deriving the Fano factor, F, and the mean energy per ion pair, Wi, in counting gases. It is based on the technique of individual counting of single ionization electrons induced in low‐pressure gas samples by soft x‐ray photons. A correlation of the experimental data with a detailed simulation of the electron deposition and counting process permits the extraction of the Fano factor and the mean energy per ion pair values. We present data of F and Wi for C2H6 and Ar/C2H6 over the energy range of 100–1500 eV. The energy dependence of these parameters reflects the atomic level structure of the gases. We discuss in detail the accuracy of this technique and its advantages and limitations. Ways are proposed for improving the technique and for broadening the energy range. © 1996 American Institute of Physics.
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51.70.+f Optical and dielectric properties
32.50.+d Fluorescence, phosphorescence (including quenching)
29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters

Mode interactions in chirowaveguides

E. O. Kamenetskii

J. Appl. Phys. 79, 8899 (1996); http://dx.doi.org/10.1063/1.362620 (7 pages) | Cited 1 time

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Chirality may provide the coupling, and hence the conversion, between two eigen polarization modes: TE and TM modes. In this paper an analysis of mode interaction in chirowaveguides is realized, taking into account longitudinal components of polarization currents. Special consideration is given to so‐called induced polarization effects which are caused by abrupt discontinuities of longitudinal polarization currents on the boundary of chiral–nonchiral media. Because of induced polarization effects, an asymmetry in mode coupling may take place. The method of investigation may be a powerful tool for the analysis of mode interactions due to both material and geometric effects. © 1996 American Institute of Physics.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.25.Bs Wave propagation, transmission and absorption

Host‐dependent optical transitions of Er3+ ions in lead–germanate and lead‐tellurium‐germanate glasses

Zhengda Pan, Steven H. Morgan, Keith Dyer, Akira Ueda, and Huimin Liu

J. Appl. Phys. 79, 8906 (1996); http://dx.doi.org/10.1063/1.362621 (8 pages) | Cited 77 times

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Differential scanning calorimetry, Raman scattering, optical absorption, and upconversion of infrared to green luminescence have been studied for Er3+‐doped lead‐germanate glass 55GeO2⋅20PbO⋅10BaO⋅10ZnO⋅5K2O (GPBZK) and lead‐tellurium‐germanate glass 30GeO2⋅30PbO⋅30TeO2⋅10CaO (GPTC). Judd–Ofelt intensity parameters of Er3+ in the two host glasses were determined and used to calculate radiative transition rates and lifetimes. Values of the radiative quantum yield of the 4S3/2→4I15/2 transition and the infrared (797 nm) to green (547 nm) upconversion efficiency of Er3+ were obtained. It has been found that the 4S3/2→4I15/2 radiative transition rate of Er3+ in GPTC glass is about twice that in the GPBZK glass and the upconversion efficiency in the GPTC glass is about four times larger than that in the GPBZK glass. These host‐dependent properties are mainly attributed to the enhanced local field and the reduced multiphonon rate in lead‐tellurium‐germanate glass compared to lead‐germanate glass. © 1996 American Institute of Physics.
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42.70.Hj Laser materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

High resonance frequency of push‐pull distributed feedback lasers

Jianyao Chen, Roman Maciejko, and Toshihiko Makino

J. Appl. Phys. 79, 8914 (1996); http://dx.doi.org/10.1063/1.362622 (3 pages)

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Using spatially dependent multimode rate equations, we perform the small signal analysis of the push‐pull distributed feedback laser. A closed form expression for the amplitude modulation response has been obtained. It shows explicitly that the resonance frequency of push‐pull distributed feedback lasers is determined by the spacing between the lasing mode and its closest antisymmetric side mode which has design implications. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Polarization effects of a high‐power CO2 laser beam on aluminum alloy weldability

Shunichi Sato, Kunimitsu Takahashi, and Bülent Mehmetli

J. Appl. Phys. 79, 8917 (1996); http://dx.doi.org/10.1063/1.362623 (3 pages) | Cited 6 times

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Linearly polarized CO2 laser beams have been used to investigate the effects of polarization on aluminum alloy weldability. Bead‐on‐plate welding tests have been performed on A5083 (AlMg4.5Mn0.7) alloy plates with quasi‐TEM00‐mode beams whose polarization direction is parallel or perpendicular to the welding direction, referred to as the parallel or the perpendicular polarization beam, respectively. Comparison of the fusion zone shapes between the two cases shows that deeper penetration, and hence more efficient optical energy coupling to the work can be obtained with the parallel polarization beam. This effect can be interpreted as being due to the higher Fresnel absorption at the keyhole front wall for the parallel polarization beam than for the perpendicular polarization beam. It is also found that the polarization effect is much more evident in the case of He gas shielding than in the case of Ar gas shielding. The weaker polarization effects observed in the case of Ar may be due to more densely formed laser‐induced plume or plasma because of lower ionization potential and much smaller thermal conductivity of Ar when compared with those of He. Under such conditions the energy coupling may be dominated by plasma absorption (the inverse bremsstrahlung absorption). It has so far been considered that in aluminum welding, the energy coupling is dominated by the plasma absorption, because relatively strong plasma is observed in aluminum welding. But our results indicate that the Fresnel absorption process has an important role on the energy coupling mechanism under certain conditions. © 1996 American Institute of Physics.
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42.62.Cf Industrial applications
79.20.Ds Laser-beam impact phenomena
81.20.Vj Joining; welding

Photorefractive composite materials with bi‐functional charge transporting second‐order nonlinear optical chromophores

Yue Zhang, Saswati Ghosal, Martin K. Casstevens, and Ryszard Burzynski

J. Appl. Phys. 79, 8920 (1996); http://dx.doi.org/10.1063/1.362582 (10 pages) | Cited 6 times

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Two bi‐functional chromophores have been developed which possess second‐order nonlinear optical and charge transporting properties. The second‐order nonlinearity arises from conjugated structures terminated by donor and acceptor groups and the charge transporting property results from a triphenylamine moiety. The bi‐functionality of the chromophores is confirmed by the large electro‐optic coefficients and high photoconductivities of composites containing these chromophores. These chromophores have been incorporated into an inert polymer to form photorefractive composite materials when doped with a photocharge generation sensitizer. The electro‐optic coefficients and photoconductivity of these composites have been measured as a function of the applied electric field as well as of the chromophore concentration. The dependence of the four‐wave mixing diffraction efficiency, holographic grating writing rate, and two‐beam coupling gain on the applied electric field and on the chromophore concentration have been evaluated. A quantitative relationship between the chromophore concentration and a number of photorefractive parameters including electro‐optic coefficient, photoconductivity, four‐wave mixing diffraction efficiency, and grating writing rate has been established. © 1996 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
72.80.Tm Composite materials

A statistical mechanics approach to digital image processing: Image enhancement

R. Aldave‐Matar and M. Ley‐Koo

J. Appl. Phys. 79, 8930 (1996); http://dx.doi.org/10.1063/1.362617 (6 pages)

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An algorithm for the enhancement of digital images is described. The algorithm is based upon the analogy that may exist between the description of a macroscopic system composed of many particles, and a digital image composed of many pixels. The analogy assumes that the intensity in a digital image fluctuates, so that the algorithm takes into account that fluctuations must decrease to a minimum in such a way that an enhanced image may be thought of as an image in an equilibrium state, leading to a quantitative criterion to stop the enhancement process. This may be taken as the starting point of a computer aided vision system, the next step being the image segmentation leading to the identification of the various patterns forming the image and which is described in a forthcoming paper. © 1996 American Institute of Physics.
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89.20.Ff Computer science and technology
07.05.Pj Image processing
05.20.-y Classical statistical mechanics

Application of exceptional wave theory to materials used in surface acoustic wave devices

N. F. Naumenko

J. Appl. Phys. 79, 8936 (1996); http://dx.doi.org/10.1063/1.362624 (8 pages) | Cited 7 times

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The exceptional wave theory developed in the last two decades is applied to trigonal crystals, widely used in surface acoustic wave devices: quartz, lithium niobate, and lithium tantalate. For quartz all crystallographic orientations where one of bulk acoustic waves satisfies the stress‐free mechanical boundary conditions, have been found and plotted on the stereographic projection of a unit wave normal sphere as ‘‘exceptional wave lines.’’ The possibility of existence and the main features of pure shear, quasishear, and quasilongitudinal exceptional waves are examined in three cut families with Euler angles (0°,θ,0°), (90°,90°,ψ), and (0°,θ,90°). These orientations are analyzed both without and with piezoelectric effect by means of analytical and numerical techniques. The obligatory existence of undamped surface skimming bulk waves or leaky waves is proved for selected cuts of trigonal crystals, such as a well‐known 41°‐rotated Y cut of lithium niobate. The behavior of these waves is compared in three crystals. A simple relation between elastic moduli of trigonal crystals with point symmetry of 32 or 3m has been derived, which allows the existence of a longitudinal type of exceptional waves. Such waves have been discovered in quartz. They are similar to those found earlier in lithium tetraborate and in both crystals they give rise to piezoelectrically coupled high velocity leaky waves with small attenuation. © 1996 American Institute of Physics.
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43.35.Pt Surface waves in solids and liquids
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Analysis and experimental study of surface transverse wave resonators on quartz

E. Gavignet, S. Ballandras, E. Bigler, C. Bonjour, J.‐C. Renaud, and W. Daniau

J. Appl. Phys. 79, 8944 (1996); http://dx.doi.org/10.1063/1.362625 (7 pages) | Cited 1 time

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Since surface transverse wave resonators are becoming increasingly used in high‐frequency electrical component applications, there is a pressing need for reliable simulation tools in this field. We develop analytical techniques for prediction of the resonant peaks of practical devices and apply them to the results of experiments in this laboratory and in others. The devices investigated are three‐grating structures composed of three arrays of metal strips or grooves on quartz substrates, which support a shear horizontal surface wave polarization. The outer gratings act as mirrors for the cavity resonance. The influence of the main design parameters on the resonator response is studied. © 1996 American Institute of Physics.
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43.35.Pt Surface waves in solids and liquids
77.65.Fs Electromechanical resonance; quartz resonators

Photoacoustic thermal characterization of spark‐processed porous silicon

A. Cruz‐Orea, I. Delgadillo, H. Vargas, A. Gudiño‐Martínez, E. Marín, C. Vázquez‐López, A. Calderón, and J. J. Alvarado‐Gil

J. Appl. Phys. 79, 8951 (1996); http://dx.doi.org/10.1063/1.362626 (4 pages) | Cited 10 times

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A non‐separation approach to determine the spark‐processed porous silicon thermal parameters is presented. This thermal characterization was performed through application of the photoacoustic technique, in combination with compositional models for spark‐processed porous silicon samples. The thermal parameters obtained are in agreement with existing studies about the composition of this material. This approach opens the possibility of performing the thermal characterization of other porous semiconductors and analogous materials. © 1996 American Institute of Physics.
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05.70.Ce Thermodynamic functions and equations of state
78.55.Mb Porous materials
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Radiation patterns of acoustic phonons emitted by hot electrons in a quantum well

V. V. Mitin, G. Paulavičius, N. A. Bannov, and M. A. Stroscio

J. Appl. Phys. 79, 8955 (1996); http://dx.doi.org/10.1063/1.362627 (9 pages) | Cited 3 times

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The acoustic phonon radiation patterns and acoustic phonon spectra due to electron–acoustic‐ phonon interaction in a double barrier quantum well have been investigated by solving both the kinetic equations for electrons and phonons. The acoustic phonon radiation patterns have strongly pronounced maximum in the directions close to the perpendicular to the quantum well direction. The radiation pattern anisotropy is explained in terms of possible electron transitions, electron distribution function, and the Hamiltonian of electron–phonon interaction. It was shown that, the simple assumption that emitted phonons always have a perpendicular wave‐vector component of the order of 2π/a, where a is the width of the quantum well, cannot explain the strong anisotropy of the radiation patterns. More detailed analysis is required and has been carried out. The emitted acoustic phonon spectra have maxima at energies 2πℏu/a, where u is the sound velocity. © 1996 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Critical radius, size effects and inverse problems for composites with imperfect interface

Robert Lipton and Bogdan Vernescu

J. Appl. Phys. 79, 8964 (1996); http://dx.doi.org/10.1063/1.362628 (3 pages) | Cited 19 times

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We provide new bounds on the interfacial barrier conductivity for isotropic particulate composites based on measured values of effective properties, known values of component volume fractions, and the formation factor for the matrix phase. These bounds are found to be sharp. Our tool is a new set of variational principles and bounds on the effective properties of composites with imperfect interface obtained by us [see R. Lipton and B. Vernescu, Proc. R. Soc. London Ser. A 452, 329 (1996)]. We apply the bounds to solve inverse problems. For isotropic polydisperse suspensions of spheres we are able to characterize the size distribution of the spherical inclusions based on measured values of the effective conductivity. © 1996 American Institute of Physics.
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44.30.+v Heat flow in porous media
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

An electronegative inductive discharge instability

M. Tuszewski

J. Appl. Phys. 79, 8967 (1996); http://dx.doi.org/10.1063/1.362666 (9 pages) | Cited 54 times

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An instability has been observed with Langmuir probes in cylindrical inductive discharges operated with low electronegative gas pressures. The instability consists of ion density modulations that propagate axially and radially at the ion acoustic speed. Measurements and calculations of negative ion concentrations in oxygen discharges suggest that the radial distribution and the magnitude of the density drops are consistent with the negative ion population. The instability appears to be a periodic expulsion of most negative ions from the plasma core. The cause of the modulations remains to be clarified. The instability may provide valuable information on negative ion concentrations and temperatures in a low pressure regime where measurements of those parameters are difficult. © 1996 American Institute of Physics.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.80.-s Electric discharges

Sheath electric field oscillation and ion kinetics in radio‐frequency discharges

Majida Fadlallah, Jean‐Paul Booth, Jacques Derouard, Nader Sadeghi, and Philippe Belenguer

J. Appl. Phys. 79, 8976 (1996); http://dx.doi.org/10.1063/1.362629 (6 pages) | Cited 7 times

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Time resolved maps of the electric field magnitude in the sheath of discharges in pure H2 have been determined as a function of pressure (0.6 and 1 Torr) and excitation frequency (30 kHz, 1, and 2.78 MHz). The electric field was determined from the Stark splitting of the n=6 level of atomic hydrogen using 2+1 photon laser‐induced fluorescence of ground state hydrogen atoms. The sheath electric field oscillations throughout the rf cycle were observed for different values of the rf driving frequency, corresponding to different regimes. We observe a ‘‘low’’ frequency regime at 30 kHz, a ‘‘high’’ frequency regime at 2.78 MHz, and an intermediate regime at 1 MHz, depending on whether the ion density profile is modulated during the rf cycle. This is the first observation of an intermediate regime where the ion transit time across the sheath is comparable to the rf period. Fluid model simulations were carried out and are in good agreement with our experimental observations. © 1996 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
52.40.Hf Plasma-material interactions; boundary layer effects
32.60.+i Zeeman and Stark effects
52.65.Kj Magnetohydrodynamic and fluid equation

Mass‐resolved ion energy measurements at both electrodes of a 13.56 MHz plasma in CF4

R. J. M. M. Snijkers, M. J. M. van Sambeek, M. B. Hoppenbrouwers, G. M. W. Kroesen, and F. J. de Hoog

J. Appl. Phys. 79, 8982 (1996); http://dx.doi.org/10.1063/1.362630 (11 pages) | Cited 19 times

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The ion energy distributions (IEDs) at the electrodes in a capacitively coupled 13.56 MHz plasma in CF4 have been measured mass resolved with a Balzers quadrupole in combination with a home‐built energy analyzer. Mass‐resolved determination offers the possibility to compare the IED of different ions achieved in the same sheath. The IEDs have been determined at both the largest and the smallest electrode. Apart from the IEDs of the CF4 species, the IEDs of ionic species in plasmas in argon and nitrogen also were determined. Apart from the CF4 ionic species CF+3, CF+2, CF+, and F+, CHF+2 ions also are present in the CF4 plasma due to residual water in the reactor. Because the CHF+2 ions are not produced in the sheath and because we do not detect elastically scattered ions, the IEDs of these ions show the typical bimodal distribution for rf plasmas which corresponds to an IED of ions which have not collided in the sheath. From these IEDs we can obtain the sheath characteristics, such as the averaged sheath potential. From the IEDs of CF+n ions one can conclude that, in the sheath of the CF4 plasma, a large number of chemical reactions takes place between the CF+n ions and the neutrals. © 1996 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.70.Nc Particle measurements
52.80.Pi High-frequency and RF discharges

Electrical conductivity in high‐frequency plasmas

G. G. Lister, Y.‐M. Li, and V. A. Godyak

J. Appl. Phys. 79, 8993 (1996); http://dx.doi.org/10.1063/1.362631 (5 pages) | Cited 34 times

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The electrical conductivity is an important parameter in understanding the mechanism by which power is coupled to a radio‐frequency (rf) discharge plasma, as well as in determining the external electrical characteristics of the discharge. We present the results of computations of the resistive and reactive components of the collisional impedance of an argon plasma at 13.56 MHz. The plasma conductivity is computed from the two‐term solution to the Boltzmann equation, and includes the velocity dependence of the electron collision frequency, as well as non‐Maxwellian electron energy distribution functions. We compare these results with those obtained from the widely used classical expression for plasma impedance, in which the electron collision frequency is computed either in the dc or high frequency limit. Our results show that neither of the classical limiting expressions are adequate for discharge pressures in the range of few mTorr to a few Torr, which includes the region of operation for many rf discharges used in many applications of plasma technology. Further, the classical formula assumes that in the high‐frequency limit the plasma reactance is due entirely to electron inertia. We demonstrate that the plasma reactance may be strongly influenced, and in some cases dominated, by electron collisions. Results are presented in graphical form, which are useful in evaluating the importance of these effects on the interpretation of experimental results and the modeling of rf discharges. © 1996 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
52.25.Fi Transport properties

Equilibrium concentrations of defects in pure and B‐doped silicon

Paul B. Rasband, Paulette Clancy, and Michael O. Thompson

J. Appl. Phys. 79, 8998 (1996); http://dx.doi.org/10.1063/1.362632 (14 pages) | Cited 25 times

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Empirical tight‐binding (ETB) calculations have been used in extensive searches for new point defect structures in pure silicon as well as silicon doped with boron. In general, these searches, which use a steepest‐descents energy minimization from random starting structures, have produced the same set of simple defects in pure silicon (tetrahedral interstitials, split interstitials, and simple vacancies) which have been widely studied. However, a variety of boron interstitials, and several new di‐interstitials (with and without boron) have been discovered. Similarities between these defects and defects found in ab initio and classical studies are discussed, as well as the accuracy of the theoretical results in general. A Stillinger–Weber (SW) model for Si–B interactions has been developed in order to obtain vibrational entropies for simple point defects. Using the SW potential, concentration prefactors have been obtained, and traditional Arrhenius plots for concentration have been produced. The theoretical equilibrium concentrations of self‐interstitials are consistent with results obtained from Pt and Au In‐diffusion experiments, and contrast with oxidation‐enhanced diffusion/oxidation‐retarded diffusion (OED/ORD)‐derived results. The theoretical results for point defect concentrations and binding energies are used to examine the assumptions of several diffusion models. © 1996 American Institute of Physics.
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61.72.Bb Theories and models of crystal defects
71.55.Cn Elemental semiconductors
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Lifetime control in silicon devices by voids induced by He ion implantation

V. Raineri, G. Fallica, and S. Libertino

J. Appl. Phys. 79, 9012 (1996); http://dx.doi.org/10.1063/1.362633 (5 pages) | Cited 33 times

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A method to control carrier lifetime in silicon locally and efficiently is presented. Voids, formed by high dose He implants, have been characterized by transmission electron microscopy demonstrating they are well localized in depth within layers thinner than 100 nm while their lateral extent is limited only by the masking capability during He implantation. Deep level transient spectroscopy measurements, performed on diodes containing different void densities, revealed the presence of two well defined trap levels, independent of void characteristics, at Ev+0.53 for holes and Ec−0.55 for electrons. These characteristics make them ideal for lifetime control in reducing parasitic transistor gain. Gummel plots on transistors have shown that when voids are formed the gain decreases from 1 to 10−3. The other transistor characteristics are only slightly influenced by the presence of voids. © 1996 American Institute of Physics.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
85.30.De Semiconductor-device characterization, design, and modeling
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Characterization of defects in self‐ion implanted Si using positron annihilation spectroscopy and Rutherford backscattering spectroscopy

M. Fujinami, A. Tsuge, and K. Tanaka

J. Appl. Phys. 79, 9017 (1996); http://dx.doi.org/10.1063/1.362634 (5 pages) | Cited 19 times

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The behavior of vacancy‐type defects and displaced Si atoms in Si(100) caused by self‐ion implantation has been investigated by variable‐energy positron annihilation spectroscopy and Rutherford backscattering spectroscopy/channeling. It is found that the recovery process of the defects strongly depends on the morphology of the implanted region. The divacancies produced by an implantation of 2×1014Si+⋅cm−2, which is less than the critical value required for amorphization, aggregate into large vacancy clusters by annealing at 300 °C. These vacancy clusters diffuse towards the surface at temperatures above 600 °C and anneal out at around 800 °C. The specimen implanted with 2×1015Si+⋅cm−2, in which a complete amorphization takes place in the damaged region, shows a different annealing characteristic. In the first stage (∼600 °C), the amorphous zone is transformed into crystalline material by solid phase epitaxial growth, although large vacancy clusters still remain. These agglomerate clusters continue to grow in a second annealing stage which takes place at around 700 °C. Annealing at 900 °C is required to eliminate these vacancy‐type defects. © 1996 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
61.05.Np Atom, molecule, and ion scattering (for structure determination only)
78.70.Bj Positron annihilation

Si ion implantation‐induced damage in fused silica probed by variable‐energy positrons

A. P. Knights, P. J. Simpson, L. B. Allard, J. L. Brebner, and J. Albert

J. Appl. Phys. 79, 9022 (1996); http://dx.doi.org/10.1063/1.362579 (7 pages) | Cited 12 times

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Samples of synthetic fused silica have been implanted at room temperature with silicon ions of energy 1.5 MeV. Fluences ranged from 1011 to 1013 cm−2. Samples were probed using variable‐energy positron annihilation spectroscopy. The Doppler‐broadening S parameter corresponding to the implanted region decreased with increasing fluence and saturated at a fluence of 1013 cm−2. It is shown that the decrease in the S parameter is due to the suppression of positronium (Ps) which is formed in the preimplanted material, due to the competing process of implantation‐induced trapping of positrons. In order to satisfactorily model the positron data it was necessary to account for positron trapping due to defects created by both electronic and nuclear stopping of the implanted ions. Annealing of the 1013 cm−2 sample resulted in measurable recovery of the preimplanted S parameter spectrum at 350 °C and complete recovery to the preimplanted condition at 600 °C. Volume compaction was also observed after implantation. Upon annealing, the compaction was seen to decrease by 75%. © 1996 American Institute of Physics.
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42.70.Gi Light-sensitive materials
61.80.Fe Electron and positron radiation effects
78.70.Bj Positron annihilation

Analysis of positron beam data by the combined use of the shape‐ and wing‐parameters

M. Clement, J. M. M. de Nijs, P. Balk, H. Schut, and A. van Veen

J. Appl. Phys. 79, 9029 (1996); http://dx.doi.org/10.1063/1.362635 (8 pages) | Cited 28 times

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An improved approach is presented for the analysis of positron beam Doppler broadening data. Instead of analyzing the energy‐dependent shape parameter, the so‐called S(E) data, we combined the shape S(E) and wing W(E) data by plotting them as a trajectory in the S–W plane, using the implantation energy as a running parameter. It is shown that this plot is of particular interest for the qualitative interpretation of the data. Furthermore, it allows the independent determination of the characteristic shape and wing parameters of the different positron trapping layers without the use of a numerical simulation and fitting program. The method and its advantages and limitations are illustrated for three cases: a silicon sample implanted with helium, a metal–oxide–silicon system subjected to a bias voltage and a bare oxide layer on silicon. © 1996 American Institute of Physics.
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78.70.Bj Positron annihilation

High‐temperature annealings of Sb and Sb/B heavily implanted silicon wafers studied by near grazing incidence fluorescence extended x‐ray absorption fine structure

C. Revenant‐Brizard, J. R. Regnard, S. Solmi, A. Armigliato, S. Valmorri, C. Cellini, and F. Romanato

J. Appl. Phys. 79, 9037 (1996); http://dx.doi.org/10.1063/1.362636 (6 pages) | Cited 12 times

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The local atomic environment of the Sb dopant in 2 and 5×1016 ions/cm2 implanted Si samples has been studied by near grazing incidence fluorescence extended x‐ray absorption fine structure at different stages of the Sb deactivation process. The annealings were performed at high temperature (900–1000 °C) during various periods: 30 s–4 h. The Sb out‐diffusion and the high percentage of Sb precipitates are put into evidence especially for Sb‐only implanted samples. The comparison of the Sb and B codiffusion data with the corresponding ones obtained by the diffusion of Sb alone revealed several anomalous effects due to dopant interaction. Moreover, a simulation program including dopant precipitation and donor–acceptor pairing allows us to foresee most of the anomalous phenomena occurring in high‐concentration codiffusion experiments. © 1996 American Institute of Physics.
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61.72.uf Ge and Si
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Positron lifetime measurements on neutron‐irradiated InP crystals

F. J. Navarro, L. C. Damonte, B. Marí, and J. L. Ferrero

J. Appl. Phys. 79, 9043 (1996); http://dx.doi.org/10.1063/1.362637 (4 pages) | Cited 4 times

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Neutron‐irradiated InP single crystals have been investigated by positron‐lifetime measurements. The samples were irradiated with thermal neutrons at different fluences yielding concentrations for Sn‐transmuted atoms between 2×1015 and 2×1018 cm−3. The lifetime spectra have been analyzed into one exponential decay component. The mean lifetimes show a monotonous increase with the irradiation dose from 246 to 282 ps. The increase in the lifetime has been associated to a defect containing an Indium vacancy. Thermal annealing at 550 °C reduces the lifetime until values closed to those obtained for the as‐grown and conventionally doped InP crystals. © 1996 American Institute of Physics.
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61.80.Hg Neutron radiation effects
78.70.Bj Positron annihilation
61.82.Fk Semiconductors
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