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1 Aug 1993

Volume 74, Issue 3, pp. 1469-2147

Page 1 of 5 Pages Next Page | Jump to Page

Distribution of barrier traversal times in numerical simulations

Mark J. Hagmann

J. Appl. Phys. 74, 1469 (1993); doi:10.1063/1.354844 (4 pages) | Cited 1 time

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Barrier penetration is attributed to energy fluctuations expected from the uncertainty principle. Numerical simulations are made by calculating the traversal time and action for a large number of possible velocity profiles. Distributions of traversal time are determined by assuming that the probability of each velocity profile decreases exponentially with the action of the fluctuation it requires. Distributions of traversal times are reported for rectangular barriers having different sizes. For large barriers the distributions are leptokurtic and centered at the semiclassical traversal time T0 = d√m/[2(V0−E)], where d and V0 are the length and height of the barrier and m and E are the mass and energy of the particle. The kurtosis decreases and the mode shifts to shorter durations with decreasing barrier size.
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03.65.-w Quantum mechanics
02.60.Cb Numerical simulation; solution of equations
73.40.Gk Tunneling

Fluid saturation‐dependent nuclear magnetic resonance spin‐lattice relaxation in porous media and pore structure analysis

Songhua Chen, Hsie‐Keng Liaw, and A. Ted Watson

J. Appl. Phys. 74, 1473 (1993); doi:10.1063/1.354845 (7 pages) | Cited 6 times

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Nuclear‐magnetic‐resonance spin‐lattice relaxation measurements were conducted in a Bentheimer sandstone sample for drainage experiments involving gas‐liquid fluid phases with ten different saturation levels ranging from complete water saturation (Sw=1) down to Sw=0.14. A monotonic decrease in relaxation times was observed as the water saturation was lowered over this broad saturation range. This phenomenon is explained by considering that for a drainage process the liquid (wetting) phase was drained from different‐sized pores at different saturations with larger pores being drained first. The relaxation decay curves corresponding to each saturation state were analyzed using both stretched exponential and discrete multiexponential functions. In particular, the effect due to bulk fluid relaxation was eliminated so that a more appropriate relationship between pore size distribution and the relaxation rate is obtained. From these analyses, the relative variation of pore size distributions corresponding to different saturation levels was obtained. A power‐law dependence of saturation with relaxation times is observed which indicates that the relaxation analysis can be used to characterize fluid saturations.
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76.60.Es Relaxation effects
47.56.+r Flows through porous media
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
51.90.+r Other topics in the physics of gases (restricted to new topics in section 51)

Selective excitation of GeF and GeF2 in glow discharges of GeF4

Shigeru Yagi, Tsuyoshi Ohta, Kazuhito Saito, and Kinich Obi

J. Appl. Phys. 74, 1480 (1993); doi:10.1063/1.354846 (4 pages)

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Intense ultraviolet emission bands around 340 nm were measured in microwave (MW) and rf glow discharges of GeF4. The bands are due to excited GeF2 and identical with the 340 nm bands in the rf discharges of GeH4‐CF4‐H2 mixtures which were published earlier. The emitting species drastically changed from GeF in matched MW discharges to GeF2 in rf discharges by way of an intermediate case in mismatched MW discharges. Selective excitation of GeF in MW plasma and GeF2 in rf plasma is discussed on the basis of a difference in electron energy between both plasmas and the energy is estimated in each case.
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33.50.Dq Fluorescence and phosphorescence spectra
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Pi High-frequency and RF discharges
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

Measurement of the optical properties of an asymmetric Einzel lens using the two‐grid method

R. A. Colman and G. J. F. Legge

J. Appl. Phys. 74, 1484 (1993); doi:10.1063/1.354847 (8 pages) | Cited 5 times

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A method is described by which the optical properties of asymmetric Einzel lenses may be measured. This method uses the technique of grid shadows. For the measurement of cardinal elements as well as spherical aberration coefficients, two independent measurements are required. For chromatic aberration coefficients, measurements are required as a function of lens voltage ratio. No extra lens is required for the measurements. An experiment is described in which the optical properties of an asymmetric lens are measured. Within the errors of the measurement, the technique is demonstrated to produce good agreement with theoretical calculations.
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41.85.Ne Electrostatic lenses, septa
42.79.Bh Lenses, prisms and mirrors

Raman investigation of the nonlinear optical phenomenon of polarization rotation in Ti:LiNbO3 channel waveguides

Uma B. Ramabadran, Howard E. Jackson, and Joseph T. Boyd

J. Appl. Phys. 74, 1492 (1993); doi:10.1063/1.354848 (9 pages) | Cited 11 times

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The nonlinear phenomenon of polarization rotation in Ti:LiNbO3 optical channel waveguides was investigated using Raman microprobe microscopy. Polarization sensitive Raman selection rules permitted the identification of polarization rotation of the propagating transverse electric or transverse magnetic waveguide mode. From an analysis of the Raman scattered light collected orthogonal to the waveguide surface the threshold power necessary to initiate the process of mode conversion could be determined. In addition, the Raman microprobe was used to determine waveguide loss coefficients by collecting inelastically scattered light. The values obtained by this method were compared to those measured by collecting the elastically scattered light. A value for the asymmetric component, β15, of the photovoltaic tensor was calculated to be 7.8×10−13 A/W for the X‐cut, Y‐propagating and 3.8×10−14 A/W and 1.2×10−14 A/W for the rapid thermally annealed Z‐cut, Y‐propagating channel waveguides, respectively.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics

Broadband tunability of a far‐infrared free‐electron laser

R. J. Bakker, C. A. J. van der Geer, D. A. Jaroszynski, A. F. G. van der Meer, D. Oepts, and P. W. van Amersfoort

J. Appl. Phys. 74, 1501 (1993); doi:10.1063/1.354849 (9 pages) | Cited 16 times

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A unique property of the free‐electron laser (FEL) is its capability to be tuned continuously over a wide spectral range. This is a major difference with all other high‐power lasers. However, the tunability of first‐generation FELs used to be quite poor (typically 10% or less), due to constraints imposed by the accelerator and the undulator. The free electron laser for infrared experiments (FELIX) uses an undulator with an adjustable gap, which permits wavelength scans over an octave in typically 2 min without the need for any readjustment of the electron beam. Results obtained in operation of the long‐wavelength FEL of the FELIX facility are presented. These involve measurements of the spectral range covered (16–110 μm), the output power, and the influence of the cavity desynchronism. The results are compared with numerical simulations.
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42.60.Fc Modulation, tuning, and mode locking
41.60.Cr Free-electron lasers

Semiconductor laser damage due to human-body-model electrostatic discharge

Y. Twu, L. S. Cheng, S. N. G. Chu, F. R. Nash, K. W. Wang, and P. Parayanthal

J. Appl. Phys. 74, 1510 (1993); doi:10.1063/1.354850 (11 pages) | Cited 15 times

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Various types of InP-based semiconductor lasers, Fabry–Perot (FP), and distributed feedback (DFB), in different wavelength regions of 1.3, 1.48, and 1.55 μm have been subjected to human-body-model electrostatic discharge (ESD) testing. The reverse V-I characteristics of these diode lasers were found to be generally most sensitive in detecting ESD damage than the forward characteristics (e.g., threshold current) of the laser. The laser ESD failure voltages were much lower for the reverse than the forward polarity and DFB lasers were found to be more vulnerable to ESD than FP lasers. The failure mechanism was found to be due to localized melting—a thermal effect—in both polarities of ESD testing. We also report the study of the latent ESD effects on the long-term aging rates of semiconductor lasers.  
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42.55.Px Semiconductor lasers; laser diodes
85.60.Jb Light-emitting devices
72.80.Ey III-V and II-VI semiconductors

Simulation and analysis of silicon electro‐optic modulators utilizing the carrier‐dispersion effect and impact‐ionization mechanism

H. C. Huang and T. C. Lo

J. Appl. Phys. 74, 1521 (1993); doi:10.1063/1.354851 (8 pages) | Cited 25 times

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A new type of Si guided‐wave electro‐optic modulator is proposed and analyzed. The modulator makes use of the impact‐ionization mechanism for carrier generation, and the carrier‐dispersion effect for electro‐optic conversion. Both electrical and wave propagation properties of the modulator were examined by a two‐dimensional device simulator and a three‐dimensional waveguide simulator, respectively. Numerical estimates of phase modulation due to refractive‐index change and intensity modulation due to optical absorption and radiation loss were obtained. One of important features of the prospected modulator is speed. The simulated turn‐on and turn‐off time of the modulator was less than 1 ns. GHz modulation is, therefore, possible for this class of modulators with device structure and doping profiles optimized for fiber coupling.
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42.82.Et Waveguides, couplers, and arrays
42.79.Hp Optical processors, correlators, and modulators
85.60.-q Optoelectronic devices

Loss characteristics of potassium and silver double‐ion‐exchanged glass waveguides

W. J. Wang, S. Honkanen, S. I. Najafi, and A. Tervonen

J. Appl. Phys. 74, 1529 (1993); doi:10.1063/1.354852 (5 pages) | Cited 9 times

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Loss characteristics of potassium and silver double‐ion‐exchanged glass waveguides are studied. Low propagation losses (less than 0.25 dB/cm) at 1.296 μm wavelength are measured, although aluminum as a mask and inexpensive multipurpose glass as a substrate are used in the fabrication process. The losses are compared to the losses of waveguides made by one‐step aluminum masked silver ion exchange and by silver ion exchange with ionic masking (dielectric mask). The reasons for the loss reduction in double‐ion‐exchanged waveguides compared to one‐step silver ion‐exchanged waveguides are discussed.
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42.82.Et Waveguides, couplers, and arrays
42.70.Ce Glasses, quartz

Photodeflection probing of the explosion of a liquid film in contact with a solid heated by pulsed excimer laser irradiation

Nhan Do, Leander Klees, Andrew C. Tam, P. T. Leung, and Wing P. Leung

J. Appl. Phys. 74, 1534 (1993); doi:10.1063/1.354853 (5 pages) | Cited 12 times

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The explosion or rapid vaporization of a liquid film on an opaque surface by a pulsed laser is studied experimentally. Using a probe‐beam deflection sensing (PDS) scheme, together with a previously developed transmission monitor, the distortion of the PDS signal due to the generation of shock waves by the exploding liquid is investigated. Various liquids, including alcohols and pure water in contact with substrates such as polyimide, amorphous carbon, and silicon, are studied for a wide range of excimer laser fluences. It is concluded that the present PDS technique is highly sensitive to the explosion threshold.
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79.20.Ds Laser-beam impact phenomena
62.60.+v Acoustical properties of liquids
82.40.Fp Shock wave initiated reactions, high-pressure chemistry
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Thermal diffusivity measurements on solids using collinear mirage detection

A. Salazar, A. Sánchez‐Lavega, and J. Fernández

J. Appl. Phys. 74, 1539 (1993); doi:10.1063/1.354854 (9 pages) | Cited 20 times

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A report on the adequacy of the collinear mirage technique for thermal diffusivity measurements on bulk homogeneous solids is presented. A 3D theoretical model for collinear deflection has been developed from which two simple linear relations between measurable parameters and the thermal diffusivity have been obtained. Two methods, the so‐called zero‐crossing and phase methods, are discussed in detail. The second one seems to be a promising tool for thermal diffusivity determination. It has been validated by means of experimental measurements on a set of samples with known thermal diffusivities. The technique is restricted to semitransparent solids but is also valid for materials with either high or low thermal diffusivities, being specially useful for this last group.
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05.70.Ce Thermodynamic functions and equations of state
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
66.20.-d Viscosity of liquids; diffusive momentum transport

Charge transfer cross section of He+ in collisional helium plasma using the plasma immersion ion implantation technique

Shu Qin, Chung Chan, Jim Browning, and Steve Meassick

J. Appl. Phys. 74, 1548 (1993); doi:10.1063/1.354855 (5 pages) | Cited 3 times

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The charge transfer collision cross section of He+ ions in a collisional helium plasma has been determined based on the ion energy distribution at the target during the plasma immersion ion implantation (PIII) process. The ion energy distribution is obtained by inferring data from a secondary‐ion mass spectroscopy measurement and a simple collisional theory. The value of the charge transfer cross section in the collisional plasma was found to be higher than previously published values. The cross‐section value determined by the PIII technique was used in a plasma simulation and was found to agree with our experimental observations.
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52.40.Hf Plasma-material interactions; boundary layer effects
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
34.70.+e Charge transfer

Cathode sheath formation in a discharge‐sustained XeCl laser

A. Belasri, J. P. Boeuf, and L. C. Pitchford

J. Appl. Phys. 74, 1553 (1993); doi:10.1063/1.354856 (15 pages) | Cited 42 times

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A one‐dimensional longitudinal model of a XeCl discharge including the cathode region, the plasma, and the external circuit has been used for conditions close to experiments for 50–100 ns laser pulse durations and electron power deposition in the MW/cm3 range in a 300 cm3 chamber. This model provides the space and time variations of the electric field, electron and positive‐ion densities in the cathode region, as well as the time variations of the charged‐particle densities and excited species concentrations in the plasma obtained with a simplified kinetic model. Results show that under normal conditions of operation the cathode electric field can reach values as high as several 106 V/cm. The influence of photoemission and secondary emission due to ion impact on the cathode is discussed. A transition from capacitive to resistive behavior of the sheath is seen to occur rapidly due to the multiplication of cathode‐emitted electrons in the large sheath electric field, leading to a fast increase in the ion conduction current in this region. The possible mechanisms of streamer formation in the sheath are also discussed. Results are presented for different values of the secondary electron emission coefficient due to ion impact from the cathode and it is shown that under conditions of low secondary emission (on the order of 10−2 or less), the electrical and chemical behavior of the plasma can be strongly affected by the presence of the sheath. Finally, the possibility of discharge instabilities related to the sheath evolution is briefly discussed on the basis of the numerical results.
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52.40.Hf Plasma-material interactions; boundary layer effects
42.55.Ks Chemical lasers

Studies of electron‐beam penetration and free‐carrier generation in diamond films

R. P. Joshi, K. H. Schoenbach, C. Molina, and W. W. Hofer

J. Appl. Phys. 74, 1568 (1993); doi:10.1063/1.354829 (7 pages) | Cited 5 times

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Experimental observations of the energy‐dependent electron‐beam penetration in type II‐A natural diamond are reported. The experimental data are compared with results obtained from numerical Monte Carlo simulations, and the results are in very good agreement. The results also reveal that a threshold energy of about 125 keV is necessary for complete penetration for a 35 μm sample. It is found that over the 30–180 keV range, the energy dependence of the penetration depth and total path length exhibits a power‐law relation. Monte Carlo simulations have also been performed to investigate the excess carrier‐generation profiles within diamond for a set of incident e‐beam energy distributions. The simulation results demonstrate the feasibility of tailoring the internal source function, and hence influencing the diffusion currents, the internal electric fields, and charge injection through the contacts.
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61.85.+p Channeling phenomena (blocking, energy loss, etc.)
72.80.Cw Elemental semiconductors
78.70.-g Interactions of particles and radiation with matter

Water vapor controlling selective reactive ion etching of SiO2/Si in NF3 plasma

M. Konuma and E. Bauser

J. Appl. Phys. 74, 1575 (1993); doi:10.1063/1.354830 (4 pages) | Cited 3 times

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Water vapor added to NF3 plasma during reactive ion etching controls the ratio of the etch rates of SiO2 and Si. Selectivity rises from a value of 0.14 at water‐free 100% NF3 to 1.99 for an initial gas composition of 35% H2O‐65% NF3. The results of mass and energy analysis of the plasma yield a basis for discussing the mechanisms which effect the selectivity. The NF3/H2O plasma removes native oxides from Si surfaces.
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52.40.Hf Plasma-material interactions; boundary layer effects
81.65.-b Surface treatments
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

A Monte Carlo simulation of resonance radiation transport in the rare‐gas–mercury positive column

Timothy J. Sommerer

J. Appl. Phys. 74, 1579 (1993); doi:10.1063/1.354831 (11 pages) | Cited 4 times

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A Monte Carlo simulation is presented for the transport of mercury 254 nm radiation in the cylindrical positive column of an argon‐mercury fluorescent lamp. Of particular interest are factors influencing the fraction f of photons which, once initially created by electron impact excitation in the volume of the lamp, actually escape to the outer wall of the lamp rather than being lost to nonresonant quenching. Increases in f of up to ≊6%, reported earlier from a similar model [Anderson et al., Phys. Rev. A 31, 2968 (1985)], are confirmed for artificial increases in the abundance of the 196Hg isotope to ≊10%. Other manipulations of the isotopic mercury content are investigated here, but none increase f by more than a few percent. Externally applied axial magnetic fields up to 0.15 T are found to increase f by up to 15%.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Hc Glow; corona
32.60.+i Zeeman and Stark effects

Annealing of silicon implanted by a high dose of cobalt ions investigated by in situ x‐ray diffraction

M. Müller, D. Bahr, W. Press, R. Jebasinski, and S. Mantl

J. Appl. Phys. 74, 1590 (1993); doi:10.1063/1.354832 (7 pages) | Cited 7 times

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A silicon wafer was implanted by a high dose of cobalt ions. Afterwards it was annealed in situ while grazing incidence x‐ray diffraction measurements in a temperature range up to 690 °C were carried out. The formation of cobalt disilicide (CoSi2) precipitates starts during implantation. The annealing dependence of the precipitate growth, of strain relaxation, and of improvements of the silicide crystallinity was determined. We got an activation energy of (0.47±0.08) eV for the observed annealing process. The result is a buried cobalt disilicide layer with very rough interfaces. The film quality can be improved by a subsequent annealing at about 1000 °C.
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61.72.uf Ge and Si
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Relaxation phenomena in the vicinity of the glass transition of poly (p‐phenylene sulfide)

Hiroshi Shimizu and Kazuo Nakayama

J. Appl. Phys. 74, 1597 (1993); doi:10.1063/1.354833 (9 pages) | Cited 11 times

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Thermally stimulated depolarization current (TSDC), thermal sampling (TS) TSDC, and dielectric spectra of poly(p‐phenylene sulfide) (PPS) were measured in the vicinity of the glass transition temperature Tg. The global TSDC spectra of amorphous PPS with varying the poling temperature revealed the presence of two TSDC peaks. Only a very intense peak associated with the α relaxation (the glass transition) was observed at 367 K in the global TSDC spectra poled at above 360 K, while an additional peak was observed at around 330 K in those spectra poled at below 355 K. This additional peak observed at below Tg was considered to be originated from the secondary sub‐Tg relaxation. Both the sub‐Tg and the α relaxations were analyzed from elementary TSDC spectra obtained by the TS technique. It was found that the temperature dependence of the relaxation times in both relaxations was ruled by the same compensation law. The physical meaning of the compensation temperature is discussed in relation to the thermal‐expansion coefficient. Moreover, the dielectric constant ϵ′ and dielectric loss factor ϵ″ of amorphous PPS are calculated using the relaxation parameters derived from the TS‐TSDC analysis. Numerical results of dielectric data are represented by three‐dimensional and/or two‐dimensional spectra and are compared with the available experimental data. The simulated dielectric spectra forecast that the sub‐Tg relaxation should appear as a peak or shoulder of ϵ″ at lower‐temperature and ultra‐low‐frequency regions in the ac measurements.
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77.22.Gm Dielectric loss and relaxation
61.43.Fs Glasses
77.84.Jd Polymers; organic compounds

New controllable optical switching by the frequency modulation method in nematic liquid crystals

Akihiko Sugimura and Zhong‐can Ou‐Yang

J. Appl. Phys. 74, 1606 (1993); doi:10.1063/1.354808 (4 pages) | Cited 3 times

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A new type of sensitive electro‐optic effect in a nematic liquid‐crystal (4‐cyano‐4′‐5‐alkyl‐bipheneyl) cell with polymer thin films is reported. Optical switching in a transmitted intensity of light passing through a cell is experimentally observed by dual low‐frequency modulation method using a triangular wave application. Dielectric relaxation effects in the thin polymer layer as part of the cell serve to reduce the effective voltage acting on the liquid‐crystal layer for lower frequencies but not for higher frequencies. The mean effective applied voltage to a liquid‐crystal layer is efficiently controlled by changing only the frequency.  
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78.66.Qn Polymers; organic compounds
78.20.Jq Electro-optical effects
61.30.-v Liquid crystals

Ion implantation and dry etching characteristics of InGaAsP (λ=1.3 μm)

S. J. Pearton, C. R. Abernathy, P. W. Wisk, and F. Ren

J. Appl. Phys. 74, 1610 (1993); doi:10.1063/1.354809 (6 pages) | Cited 4 times

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The electrical activation characteristics of Si+ and Be+ ions implanted into InGaAsP (λ=1.3 μm) grown lattice matched to InP by metalorganic molecular beam epitaxy were studied as a function of ion dose (5×1012–5×1014 cm−2), annealing time (3–60 s) and annealing temperature (575–750 °C). Maximum doping concentrations of ∼2×1019 cm−3 were obtained for both Si+ and Be+, with activation energies for electrical activation of 0.58 and 0.39 eV, respectively. Multiple energy F+ or H+ implants can be used to produce high resistance layers for isolation purposes—maximum sheet resistances of ∼8×106 Ω/☒ or ∼106 Ω/☒ for initially p+ or n+ InGaAsP, respectively, were obtained for F+ implants followed by annealing near 450 °C. Smooth, anisotropic dry etching of the InGaAsP is obtained with electron cyclotron resonance CH4/H2/Ar discharges at low dc biases. The etch rates are the same for both n+ and p+ quaternary layers and are independent of the doping level.  
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.65.-b Surface treatments
61.72.uj III-V and II-VI semiconductors
73.61.Ey III-V semiconductors

Analysis of aluminum tungsten oxide ceramics synthesized by a high‐power cw CO2 laser

Xingjiao Li, Fang Zheng, Qiguang Zheng, Jiarong Li, Zaiguang Li, and Shaopin Li

J. Appl. Phys. 74, 1616 (1993); doi:10.1063/1.354810 (9 pages) | Cited 2 times

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Ceramics in the Al2O3‐WO3 system have been produced by laser irradiation. Examination of the products by scanning electron microscopy showed that a cell structure had formed in the specimens. A comparison of the properties of the samples synthesized by laser and by conventional sintering methods showed that the laser technique can produce new materials with some unique properties such as the linear decrease in resistivity of Al2O3‐50 mol % WO3 specimens with increasing temperature over the range of 10–150 °C. X‐ray photographic powder analysis indicated that the conducting phase in the specimen is a nonequilibrium product: AlxWO3 tungsten bronze.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.66.Fn Inorganic compounds
72.80.-r Conductivity of specific materials

Radiation damage behavior of LiNbO3 crystal by MeV F ion implantation

Bo‐Rong Shi, Ke‐Ming Wang, Zhong‐Lie Wang, Xiang‐Dong Liu, Tian‐Bing Xu, and Pei‐Ran Zhu

J. Appl. Phys. 74, 1625 (1993); doi:10.1063/1.354811 (4 pages) | Cited 3 times

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X, Y, and Z crystalline cut LiNbO3 crystals were implanted by 1.0 MeV F ions with a dose of 1×1015 ions/cm.2 The virgin and implanted LiNbO3 crystals were investigated using the Rutherford backscattering/channeling technique. The obtained minimum yields of virgin crystals were 4%, 8%, and 6% for X‐, Y‐, and Z‐cut LiNbO3 crystals, respectively, because of their different arrangements of lattice sites in channeling direction. The measured damage profiles are also influenced by the arrangement of lattice sites in channeling measurements. The damage profiles of X‐cut LiNbO3 crystal induced by 1.0 MeV F+ at a fluence range of 1×1014–3×1015 ions/cm2 have been studied and compared with the Transport of Ions in Matter, version 1990 calculation. It has been found that not only the nuclear energy deposition but also the electronic energy deposition influences the defect production.
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61.80.Jh Ion radiation effects
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Time dependence of radiation‐induced generation currents in irradiated InGaAs photodiodes

G. J. Shaw, R. J. Walters, S. R. Messenger, and G. P. Summers

J. Appl. Phys. 74, 1629 (1993); doi:10.1063/1.354812 (7 pages) | Cited 6 times

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The annealing behavior of the reverse bias current‐voltage curves of 1 MeV electron irradiated In0.53Ga0.47As photodiodes has been measured at 300 K. The observed decay is shown to be correlated with the reduction of the E2 peak height with time, as measured by deep level transient spectroscopy. The reverse current is found to decay with a logarithmic time dependence, which can be explained by a model in which the annealing of the E2 defects is controlled by a distribution of thermal energy barriers.
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61.80.Fe Electron and positron radiation effects
85.60.Dw Photodiodes; phototransistors; photoresistors
71.55.Eq III-V semiconductors

Defects in MeV Si‐implanted Si probed with positrons

Bent Nielsen, O. W. Holland, T. C. Leung, and K. G. Lynn

J. Appl. Phys. 74, 1636 (1993); doi:10.1063/1.354813 (4 pages) | Cited 64 times

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Vacancy‐type defects produced by implantation of MeV doses of Si ions (1011–1015 atoms/cm2) at room temperature have been probed using depth‐resolved positron annihilation spectroscopy. The defect (divacancy) concentration increases linearly with dose for low doses (<1012 Si/cm2). In situ isochronal annealing was followed for oxygen‐containing Si (10 ppm) and oxygen‐‘‘free’’ Si implanted to doses (5×1012 and 5×1014 Si/cm2). Two main annealing stages were observed at the same temperatures in the studied samples in spite of significant differences in doses and oxygen content. In the first stage (∼200 °C) a significant fraction of divacancies was observed to form large vacancy clusters. These clusters were removed in the second stage (∼675 °C) after which the oxygen‐free samples returned to pre‐irradiation conditions, whereas oxygen‐defect complexes were formed in the oxygen‐containing samples.
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61.72.uf Ge and Si
78.70.Bj Positron annihilation

Rate‐dependent ductile failure model

F. L. Addessio and J. N. Johnson

J. Appl. Phys. 74, 1640 (1993); doi:10.1063/1.354814 (9 pages) | Cited 17 times

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A rate‐dependent constitutive model for the dynamic deformation of ductile materials is developed. The model introduces a physical length scale into the equations governing the progressive failure of materials due to void growth. Consequently, mesh sensitivity or localization problems inherent to rate‐independent models are precluded. The model is implemented into an explicit, finite‐difference computer code. The insensitivity of the model to changes in the mesh size is demonstrated. Comparisons are provided between numerical simulations and data for uniaxial impact experiments. Excellent agreement is established between the final porosity levels and the width of the damage zone. Also, excellent agreement is provided for the stress histories, including the peak stress values and the spall signal.
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62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
83.10.Gr Constitutive relations
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