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1 May 2003

Volume 93, Issue 9, pp. 4955-5841

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Frontiers of silicon-on-insulator

G. K. Celler and Sorin Cristoloveanu

J. Appl. Phys. 93, 4955 (2003); http://dx.doi.org/10.1063/1.1558223 (24 pages) | Cited 183 times

Online Publication Date: 16 April 2003

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Silicon-on-insulator (SOI) wafers are precisely engineered multilayer semiconductor/dielectric structures that provide new functionality for advanced Si devices. After more than three decades of materials research and device studies, SOI wafers have entered into the mainstream of semiconductor electronics. SOI technology offers significant advantages in design, fabrication, and performance of many semiconductor circuits. It also improves prospects for extending Si devices into the nanometer region (<10 nm channel length). In this article, we discuss methods of forming SOI wafers, their physical properties, and the latest improvements in controlling the structure parameters. We also describe devices that take advantage of SOI, and consider their electrical characteristics. © 2003 American Institute of Physics.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
01.30.Rr Surveys and tutorial papers; resource letters
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Method of increasing spatial resolution of the scanning near-field microwave microscopy

R. Kantor and I. V. Shvets

J. Appl. Phys. 93, 4979 (2003); http://dx.doi.org/10.1063/1.1522486 (7 pages) | Cited 2 times

Online Publication Date: 16 April 2003

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In this article we propose methods for the measurement of electric intensity of a microwave field above the surface of microwave circuits. Using miniaturized coaxial antennas and a special probe positioning system, we measure both the amplitude and the phase of the induced field above the device under test. We introduce a position/signal difference method to further increase the spatial resolution down to about 30 μm—about one order better than contemporary microwave scanning devices utilizing coaxial antennas. The effect is theoretically analyzed and experimentally verified. The probes are calibrated in a well-defined field standard to allow quantitative characterization of the measured field. Performance of our scanning system utilizing these methods is demonstrated using a PCB finger capacitor. © 2003 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
84.40.Dc Microwave circuits
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.40.Ba Antennas: theory, components and accessories
06.20.F- Units and standards
84.32.Tt Capacitors

Comparison of three-dimensional photonic crystal slab waveguides with two-dimensional photonic crystal waveguides: Efficient butt coupling into these photonic crystal waveguides

N. Moll and G.-L. Bona

J. Appl. Phys. 93, 4986 (2003); http://dx.doi.org/10.1063/1.1564282 (6 pages) | Cited 12 times

Online Publication Date: 16 April 2003

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Butt coupling into photonic crystal waveguides is computationally investigated for a three-dimensional photonic crystal slab and a two-dimensional photonic crystal. The photonic crystal slab consists of a silicon-on-insulator substrate with a triangular array of holes, in which the silicon layer is the optical guiding layer. The transmission spectra of the two-dimensional system and the slab system differ significantly. The slab system supports only a small range of frequencies in which a guided mode exists. In this frequency range, the transmission is comparable with that of the two-dimensional system, and its value is around 0.8. For the other frequencies, where for the slab system only resonances exist, the transmission is much lower than that of the two-dimensional system because of losses in the photonic crystal waveguide. Therefore, we conclude that complete three-dimensional computations have to be performed to obtain quantitative results for photonic crystal slab systems. © 2003 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Simulation of blue InGaN quantum-well lasers

Jih-Yuan Chang and Yen-Kuang Kuo

J. Appl. Phys. 93, 4992 (2003); http://dx.doi.org/10.1063/1.1563818 (7 pages) | Cited 15 times

Online Publication Date: 16 April 2003

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For InGaN laser diodes with emission wavelengths longer than 435 nm, the threshold current density usually increases with the number of InGaN well layers. This phenomenon could be attributed to the dissociation of the high indium content InGaN well layer at a high growth temperature of 750 °C due to a high InGaN dissociation pressure. In this article, the laser performance of the blue InGaN laser diode structures have been numerically investigated with a laser technology integrated program simulation program. The simulation results suggest that the inhomogeneous hole distribution in the quantum wells also plays an important role in the laser performance as a function of the number of InGaN well layers. In addition to the inhomogeneous hole distribution in the quantum wells, the phenomenon and resolution of the electronic current overflow problem in the blue InGaN quantum-well lasers are also investigated. © 2003 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.30.De Semiconductor-device characterization, design, and modeling
78.67.De Quantum wells
73.63.Hs Quantum wells
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.07.St Quantum wells
81.05.Ea III-V semiconductors

Effects of spacer thickness on optical properties of stacked Ge/Si quantum dots grown by chemical vapor deposition

Wen-Hao Chang, Wen-Yen Chen, An-Tai Chou, Tzu-Min Hsu, Pan-Shiu Chen, Zingway Pei, and Li-Shyue Lai

J. Appl. Phys. 93, 4999 (2003); http://dx.doi.org/10.1063/1.1564883 (4 pages) | Cited 16 times

Online Publication Date: 16 April 2003

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Photoluminescence investigations on stacked Ge/Si dots with different spacer thicknesses are presented. According to the emission energy shift in the Ge dots, we found that a thinner spacer layer will lead to remarkable Ge–Si intermixing during the stacking of the Ge/Si dots. Such material intermixing not only shallows the dot potential depth, but also softens the sharpness of the dot/spacer interface. In addition, the temperature of photoluminescence quenching also varies with the spacer thickness. Finally, we point out some important factors that are relevant to the room-temperature luminescence efficiency of stacked Ge/Si quantum dots. © 2003 American Institute of Physics.
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78.67.Hc Quantum dots
68.65.Hb Quantum dots (patterned in quantum wells)
81.07.Ta Quantum dots
78.55.Ap Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Fx Diffusion; interface formation

Photoluminescence emission and Raman scattering polarization in birefringent organic microcavities in the strong coupling regime

D. N. Krizhanovskii, R. Butté, L. G. Connolly, A. I. Tartakovskii, D. G. Lidzey, M. S. Skolnick, and S. Walker

J. Appl. Phys. 93, 5003 (2003); http://dx.doi.org/10.1063/1.1563826 (5 pages) | Cited 5 times

Online Publication Date: 16 April 2003

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We have investigated the polarization properties of photoluminescence and Raman scattering in strongly coupled organic microcavities containing cyanine dye J aggregates. The birefringence of radially aligned J aggregates results in a large energy splitting of polariton modes when the electric field of the incoming laser light is perpendicular or parallel to the alignment direction. This splitting allows the degree of polarization of doubly resonant Raman processes involving the vibrational modes of J aggregates to be controlled, where the ingoing and outgoing channels are in resonance with the lower polariton branch. As well as providing insight into the properties of polaritons in organic microcavities, these experiments are a sensitive probe of alignment effects arising during the spin-coating deposition process. © 2003 American Institute of Physics.
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78.20.Fm Birefringence
78.30.Jw Organic compounds, polymers
78.55.Kz Solid organic materials
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
42.50.-p Quantum optics
42.70.Qs Photonic bandgap materials
63.50.-x Vibrational states in disordered systems
81.05.Qk Reinforced polymers and polymer-based composites

Cooperative upconversion as the gain-limiting factor in Er doped miniature Al2O3 optical waveguide amplifiers

P. G. Kik and A. Polman

J. Appl. Phys. 93, 5008 (2003); http://dx.doi.org/10.1063/1.1565697 (5 pages) | Cited 30 times

Online Publication Date: 16 April 2003

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Erbium doped Al2O3 waveguide amplifiers were fabricated using two different doping methods, namely Er ion implantation into sputter deposited Al2O3, and co-sputtering from an Er2O3/Al2O3 target. Although the Er concentration in both materials is almost identical (0.28 and 0.31 at. %), the amplifiers show a completely different behavior. Upon pumping with 1.48 μm, the co-sputtered waveguide shows a strong green luminescence from the 4S3/2 level, indicating efficient cooperative upconversion in this material. This is confirmed by pump power dependent measurements of the optical transmission at 1.53 μm and the spontaneous emission at 1.53 and 0.98 μm. All measurements can be accurately modeled using a set of rate equations that include first order and second order cooperative upconversion. The first order cooperative upconversion coefficient C24 is found to be 3.5×10−16 cm3 s−1 in the co-sputtered material, two orders of magnitude higher than the value obtained in Er implanted Al2O3 of 4.1×10−18 cm3 s−1. It is concluded that the co-sputtering process results in a strongly inhomogeneous atomic scale spatial distribution of the Er ions. As a result, the co-sputtered waveguides do not show optical gain, while the implanted waveguides do. © 2003 American Institute of Physics.
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42.65.Wi Nonlinear waveguides
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Yj Optical parametric oscillators and amplifiers
42.79.Gn Optical waveguides and couplers
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.15.Cd Deposition by sputtering
42.70.Mp Nonlinear optical crystals
61.72.up Other materials
78.55.Hx Other solid inorganic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.50.Nn Quantum optical phenomena in absorbing, amplifying, dispersive and conducting media; cooperative phenomena in quantum optical systems
78.45.+h Stimulated emission
61.72.S- Impurities in crystals
71.55.Ht Other nonmetals

Accessing the optical limiting properties of metallo-dielectric photonic band gap structures

M. C. Larciprete, C. Sibilia, S. Paoloni, M. Bertolotti, F. Sarto, and M. Scalora

J. Appl. Phys. 93, 5013 (2003); http://dx.doi.org/10.1063/1.1564283 (5 pages) | Cited 34 times

Online Publication Date: 16 April 2003

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The optical limiting properties of a one-dimensional, transparent metallodielectric photonic band gap structure are studied. Due to light confinement in the structure that enhances the nonlinear response of the layers, a nonlinear transmission dependence on the incident light intensity is found. Experimental results are reported for a four period sample where the single period consists of ZnO and Ag layers 109 and 17 nm thick, respectively. The structure was designed to exhibit a transmission resonance at 532 nm. Under the action of a Q-switched frequency doubled Nd:yttrium–aluminum–garnet laser, a decrease in transmission of approximately 50% is obtained for a maximum incident light intensity of 2 GW/cm2. These results are explained in terms of a dynamic change of the absorption coefficient due to the enhancement of the two-photon absorption process. These results suggest that the structure is suitable for optical limiting applications in the visible range. © 2003 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency

Photoluminescence transitions in semiconductor superlattices. Theoretical calculations for InGaN blue laser device

A. Kunold and P. Pereyra

J. Appl. Phys. 93, 5018 (2003); http://dx.doi.org/10.1063/1.1565698 (7 pages) | Cited 10 times

Online Publication Date: 16 April 2003

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The optical response of an AlGaN/GaN/(InxGa1−xN)n/GaN/AlGaN heterostructure is obtained from precise, and comparatively simple, transition probability calculations. A comprehensive approach to evaluate these quantities from rigorous expressions of the heterostructure's energy eigenvalues and eigenfunctions is given. Taking full account of the longitudinal quantum wells and the lateral quantum dot confinement, quite precise intraband energy levels and wave functions have been obtained. Photoluminescence results for sectionally constant band-edge profile differ from the experimental measurements by approximately 45 meV. We show that the band-edge modulation arising from charge polarization, is responsible for this difference. © 2003 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Ah General laser theory
73.21.Cd Superlattices
42.55.Px Semiconductor lasers; laser diodes
85.30.De Semiconductor-device characterization, design, and modeling
78.66.Fd III-V semiconductors
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Particle-in-cell/Monte Carlo simulations of a low-pressure capacitively coupled radio-frequency discharge: Effect of adding H2 to an Ar discharge

E. Neyts, M. Yan, A. Bogaerts, and R. Gijbels

J. Appl. Phys. 93, 5025 (2003); http://dx.doi.org/10.1063/1.1563820 (9 pages) | Cited 9 times

Online Publication Date: 16 April 2003

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A one-dimensional particle-in-cell/Monte Carlo code with three velocity components is developed to simulate a capacitively coupled radio-frequency Ar/H2 discharge at low pressure, and to investigate the effect of adding hydrogen to an argon discharge. This self-consistent kinetic simulation technique allows one to study fundamental processes in the discharge at the molecular level. It is shown that the addition of small amounts of H2 to an Ar discharge has profound effects on the discharge behavior, i.e., a change in the electron energy probability function, an increase in the electron density at low H2 content and a decrease at higher H2 content, as well as a dip in the Ar+ ion density in the center of the discharge at higher pressure. These effects can be explained by the collision processes taking place in the discharge. The simulations were carried out in the pressure range 50–250 mTorr, at voltages of 300 and 800 V, while the H2 content was varied between 0% and 10%, at a constant driving frequency of 13.56 MHz. © 2003 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
52.65.-y Plasma simulation
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
52.25.Vy Impurities in plasmas

Effects of presheath dynamics on radio-frequency sheaths

N. Xiang and F. L. Waelbroeck

J. Appl. Phys. 93, 5034 (2003); http://dx.doi.org/10.1063/1.1563823 (9 pages) | Cited 5 times

Online Publication Date: 16 April 2003

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A common approach to the study of radio frequency (rf) sheaths is to separate the description of the sheaths from that of the bulk plasma. In order to solve the resulting set of equations, an appropriate boundary condition for the sheath model has to be specified at the sheath–plasma boundary. In the existing sheath models, this boundary condition is assumed to be stationary. In present article, we investigate the ion dynamics in both presheath region and sheath region by using numerical as well as analytical methods. It is found that the presheath introduces an additional time scale ωpre=VB/l (here, l is the characteristic scale of the presheath and VB is the Bohm velocity). If the rf frequency ω is low enough so that ω⩽ωpre, the boundary condition for the sheath depends on the ion dynamics in the presheath. In the very low-frequency regime ω≪VB/l, an analytical expression for the ion current is obtained which agrees well with the numerical result. © 2003 American Institute of Physics.
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52.40.Kh Plasma sheaths
52.25.Fi Transport properties

Evaluation of improved efficiency with a diamond coating for a plasma display panel electrode

Yasushi Matsunaga, Tomokazu Kato, Tadatsugu Hatori, and Seishiro Hashiguchi

J. Appl. Phys. 93, 5043 (2003); http://dx.doi.org/10.1063/1.1567034 (10 pages) | Cited 7 times

Online Publication Date: 16 April 2003

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Application of diamond to electrode coating of a plasma display panel (PDP) is evaluated, since we expect diamond to emit much secondary electron due to the Auger neutralization induced by Xe ions. In a conventional magnesium oxide-xenon (MgO/Xe) system, the most abundant Xe+ produced in the discharge does not effectively cause the secondary electron emission, because the condition of the Auger neutralization is not satisfied. In order to increase the efficiency of ultraviolet (UV) radiation, being especially important for engineering, we should avoid such inefficiency. Under suitable conditions in diamond/Xe system the Auger neutralization can occur. Further, if the electron affinity χ is negative, i.e., negative electron affinity (NEA), the condition of the Auger neutralization in diamond/Xe system is sufficiently satisfied. First, we calculate the coefficients of the secondary electron emission on diamond of clean surface or of hydrogenated surface where the dangling bonds are terminated, on the basis of the Hagstrum model. If the NEA with the electron affinity χ=−0.5 is realized, the high ion-induced secondary electron coefficients such as γXe=0.25 and γNe=0.32 are obtained. Next, we carry out a one-dimensional fluid simulation of the electric discharge in which the two secondary electron emission coefficients of Ne and Xe obtained theoretically are set. Results are presented with changing the sustaining voltage, the fraction of Xe, and the duration of the zero-voltage phase. For 10%Xe mixture, it is shown that the efficiency of UV radiation in the diamond coating increases two times higher than that in the MgO coating. An unnecessarily spontaneous breakdown during the zero-voltage phase, which is peculiar to high secondary electron emission materials, is observed. A mechanism of the breakdown is discussed and means to suppress it are proposed. Taking the zero-voltage phase short and increasing the fraction of Xe up to 50%, in comparison with MgO, a maximum improvement of 3.5 times in the efficiency of UV radiation can be performed. The high secondary electron emission due to Xe ion brings about a decrease in the sustaining voltage, and the sustaining voltage can be further lowered by shortening the duration of the zero-voltage phase. The operation with an increase of Xe fraction becomes attainable. The feasibility of the high performance operation on the ac type PDP by utilizing the materials including diamond with high secondary electron emission for Xe is quantitatively shown. © 2003 American Institute of Physics.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.75.-d Plasma devices
81.05.U- Carbon/carbon-based materials
85.60.Pg Display systems
52.80.-s Electric discharges

Fourier-transform infrared and optical emission spectroscopy of CF4/O2/Ar mixtures in an inductively coupled plasma

Brett A. Cruden, M. V. V. S. Rao, Surendra P. Sharma, and M. Meyyappan

J. Appl. Phys. 93, 5053 (2003); http://dx.doi.org/10.1063/1.1563819 (10 pages) | Cited 8 times

Online Publication Date: 16 April 2003

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Characterization of CF4/O2/Ar inductively coupled plasmas by Fourier-transform infrared (FTIR) spectroscopy and optical emission spectroscopy (OES) in a Gaseous Electronics Conference reference cell has been carried out. Characterization was performed at three mixture compositions (80/10/10, 60/20/20, and 40/30/30), powers of 200 and 300 W and pressures between 10 and 50 mTorr. Quantitative estimates of CF4, CO, COF2, and SiF4 etch products are made via FTIR, while the OES combined with actinometry allows for qualitative characterization of conversion of CF4 to atomic C, CF, and C2, and molecular oxygen to atomic oxygen. Qualitative measurements of F density and etch products Si and SiF are also made by OES. Results are explained by a combination of electron-impact dissociation and recombination processes. In the absence of significant capacitive coupling, etch species are believed to be formed primarily by window interactions with atomic F. Rotational temperatures are estimated by both FTIR and analysis of emission spectra. The FTIR technique tends to estimate temperatures several hundred K lower than OES data due to the absorption of colder gas species outside of the plasma. © 2003 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
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Sub-picosecond shock interferometry of transparent thin films

S. D. McGrane, D. S. Moore, and D. J. Funk

J. Appl. Phys. 93, 5063 (2003); http://dx.doi.org/10.1063/1.1563034 (6 pages) | Cited 8 times

Online Publication Date: 16 April 2003

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Ultrafast spatial interferometric measurements of shock dynamics in transparent thin films exhibit phase shifts caused by both surface motion and the interference of multiple reflections off the moving shock wave interface. The interference effects are strong perturbations on the phase shift, which do not allow independent measurement of surface motion. Calculations of the time dependent phase shift that include reflective surface motion, shock wave transit through the transparent thin film, and thin film interference effects are shown to match experimental measurements in 625-nm-thick films of polymethylmethacrylate (PMMA) shocked to 19 GPa. Interferometric data obtained at two angles of incidence and two polarizations were sufficient to uniquely determine the PMMA shocked refractive index, shock speed, and particle velocity. Interferometric results as a function of shock strength, 2–20 GPa, suggest that submicron PMMA films have essentially the same material response to shock loading (Hugoniot) as macroscopic samples. © 2003 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
68.60.Bs Mechanical and acoustical properties
78.66.Qn Polymers; organic compounds
78.47.-p Spectroscopy of solid state dynamics
07.60.Ly Interferometers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Influence of a pre-deposited carbon submonolayer on the Ge island nucleation on Si(001)

D. Dentel, J. L. Bischoff, L. Kubler, M. Stoffel, and G. Castelein

J. Appl. Phys. 93, 5069 (2003); http://dx.doi.org/10.1063/1.1562747 (6 pages) | Cited 8 times

Online Publication Date: 16 April 2003

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Si surfaces manipulated by a carbon (C) pre-deposition have been used to modify the growth morphology of Ge islands. In situ reflection high-energy electron diffraction and x-ray photoelectron diffraction and ex situ atomic force microscopy studies have been conducted for constant C seeding and varying growth temperatures and Ge coverages, with the aim of deepening the understanding of the relevant Ge quantum dot formation. With temperatures ranging from 400 to 600 °C, well structured Ge islands grow in a Volmer–Weber mode as soon as 0.4 ML of C and 1 ML of Ge are deposited. Strongly modified behaviors are nevertheless observed by changing the Ge growth temperature from 500 to 600 °C. By increasing the Ge coverage from 1 to 6 ML at 500 °C, the island height increases at constant density, whereas, at 600 °C, a strong reduction of the density is observed, with a three-dimensional-two-dimensional transition probably due to a partial Ge intermixing in the Si matrix. These different nucleation schemes are connected with varying evolutions of the initial C-related c(4×4) reconstruction. © 2003 American Institute of Physics.
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81.07.Ta Quantum dots
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Fx Diffusion; interface formation
79.60.Jv Interfaces; heterostructures; nanostructures
68.37.Ps Atomic force microscopy (AFM)

Structural characterization using spectroscopic techniques of Yb films grown on W(110) under ultrahigh vacuum conditions

M. E. Dávila, S. L. Molodtsov, J. Avila, C. Laubschat, and M. C. Asensio

J. Appl. Phys. 93, 5075 (2003); http://dx.doi.org/10.1063/1.1561588 (5 pages)

Online Publication Date: 16 April 2003

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Forward scattering photoelectron diffraction has been used to study the structure of Yb(111) films epitaxially deposited onto W(110) single crystals. The measurements have been carried out recording the intensity modulations of the Yb 4f photoemission core levels throughout a complete set of polar and azimuthal scans. We observe the coexistence of two domains with a characteristic face-centered-cubic (fcc) structure. Both domains appear to be rotated 60° toward each other. The possible presence of a hexagonal-close-packed (hcp) phase or a mixture of fcc and hcp phases, which could be stabilized by the presence of oxygen, has been particularly investigated. However, these two possibilities have been disregarded due to the clear disagreement observed between the scattering simulations and the experimental data. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
79.60.Dp Adsorbed layers and thin films
73.20.At Surface states, band structure, electron density of states
61.66.Bi Elemental solids

Analysis of multijunction solar cell degradation in space and irradiation induced recombination centers

M. Zazoui, M. Mbarki, A. Zin Aldin, J. C. Bourgoin, O. Gilard, and G. Strobl

J. Appl. Phys. 93, 5080 (2003); http://dx.doi.org/10.1063/1.1561999 (5 pages) | Cited 10 times

Online Publication Date: 16 April 2003

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We demonstrate how, using electroluminescence, the parameters characterizing the recombination center induced by irradiation in a solar cell can be measured. Because electroluminescence is able to provide information on an individual cell in a multijunction (MJ) cell device, independently of the others, we apply this technique to measure these parameters in InGaP/GaAs/Ge MJ cells. We then calculate the variations of the open-circuit voltage and short-circuit current of such cells versus fluence. The results are compared with experimental data obtained for 1 MeV electron irradiations. © 2003 American Institute of Physics.
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84.60.Jt Photoelectric conversion
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors
78.60.Fi Electroluminescence
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Decay mechanism of fracture induced electromagnetic pulses

A. Rabinovitch, V. Frid, D. Bahat, and J. Goldbaum

J. Appl. Phys. 93, 5085 (2003); http://dx.doi.org/10.1063/1.1562752 (6 pages) | Cited 6 times

Online Publication Date: 16 April 2003

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In this article we consider the rise and fall time (which were earlier shown experimentally to be the same) of electromagnetic radiation (EMR) from propagating cracks. This feature is shown theoretically to be inversely proportional to the pulse frequency ω and to the fourth degree of the absolute temperature. It is shown experimentally that in glass and in glass ceramics, which are not porous, and in granite, whose porosity is of the order of 5%, τ is indeed inversely proportional to ω. In chalk, whose porosity is as high as 40%, however, this relation is not observed. We argue that the latter result is due to the interaction between the cracks which emit the EMR and the pores of the material and specifically to the spread of ensuing temperatures of the cracks caused by this interaction. © 2003 American Institute of Physics.
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78.60.Mq Sonoluminescence, triboluminescence
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Dynamic mechanisms in photoluminescence of gallium-doped ZnSe grown by molecular-beam epitaxy

S. Z. Wang and S. F. Yoon

J. Appl. Phys. 93, 5091 (2003); http://dx.doi.org/10.1063/1.1563822 (4 pages) | Cited 4 times

Online Publication Date: 16 April 2003

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Reported are the temperature-dependent photoluminescence (PL) results of molecular-beam epitaxy-grown gallium-doped zinc selenide (ZnSe:Ga) sample with the sample temperature varied from 10 to 300 K. The physical origins of a twin PL structure peaked at 2.794 and 2.733 eV, respectively, that overwhelm the whole PL spectrum are discussed, and the dynamic processes behind these temperature-dependent PL results are also investigated. © 2003 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
71.55.Gs II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Dz II-VI semiconductors

Comparison of luminescent efficiency of InGaAs quantum well structures grown on Si, GaAs, Ge, and SiGe virtual substrate

V. K. Yang, S. M. Ting, M. E. Groenert, M. T. Bulsara, M. T. Currie, C. W. Leitz, and E. A. Fitzgerald

J. Appl. Phys. 93, 5095 (2003); http://dx.doi.org/10.1063/1.1563031 (8 pages) | Cited 6 times

Online Publication Date: 16 April 2003

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In order to study the luminescent efficiency of InGaAs quantum wells on Si via SiGe interlayers, identical In0.2Ga0.8As quantum well structures with GaAs and Al0.25Ga0.75As cladding layers were grown on several substrates by an atmospheric metalorganic vapor deposition system. The substrates used include GaAs, Si, Ge, and SiGe virtual substrates. The SiGe virtual substrates were graded from Si substrates to 100% Ge content. Because of the small lattice mismatch between GaAs and Ge (0.07%), high-quality GaAs-based thin films with threading dislocation densities <3×106 cm−2 were realized on these SiGe substrates. Quantitative cathodoluminescence was used to compare the luminescent efficiency of the quantum well structure on the different substrates and cross-sectional transmission electron microscopy was used to characterize dislocation densities. Our results show that the InGaAs quantum wells grown on the GaAs substrates have the highest luminescent efficiencies due to the lowest dislocation densities. Interestingly, InGaAs quantum wells grown on the SiGe virtual substrates outperform those on Ge substrates, both in terms of luminescent efficiency and dislocation density. This difference is attributed to the variation in thermal expansion coefficient (α) and its impact on defect structure during the process cycle. The SiGe virtual substrate has a smaller α compared to a Ge substrate because of the smaller α of the Si substrate, which helps minimize compressive strain in the quantum well layer during the temperature decrease from the growth temperature. Consequently, fewer misfit dislocations are created between the quantum well and cladding interfaces. These misfits can greatly affect the luminescent efficiency since they can act as recombination sites. In general, the efficiencies of the quantum wells on the SiGe and Ge substrates were affected only by higher misfit dislocation densities, whereas the quantum wells on the Si substrate had low efficiency due to high threading dislocation density. © 2003 American Institute of Physics.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.66.Fd III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
65.40.De Thermal expansion; thermomechanical effects

Effect of ion implantation on surface energy of ultrahigh molecular weight polyethylene

J. S. Chen, Z. Sun, P. S. Guo, Z. B. Zhang, D. Z. Zhu, and H. J. Xu

J. Appl. Phys. 93, 5103 (2003); http://dx.doi.org/10.1063/1.1559943 (6 pages) | Cited 12 times

Online Publication Date: 16 April 2003

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The effect of ion implantation including ion species (N2+ and C3H8+) and the fluences (1×1014–5×1015 ions/cm2) on the surface energy of ultrahigh molecular weight polyethylene (UHMWPE) were investigated. The total surface energy increases significantly after implanting with the fluence of 1×1014 ions/cm2 regardless of ion species, then, the total surface energy slightly increases for N2+ implanted UHMWPE and decreases slightly for C3H8+ implanted UHMWPE with a further increase of fluence. The structural changes of UHMWPE with different fluence for different ion species are very similar. The linear chains of UHMWPE are damaged and cross linking is generated after implantation. As the fluence increases, the polymer surface becomes more disordered, and the surface becomes hydrogenated amorphous carbon when the fluence exceeds 1×1015 ions/cm2. The surface roughness increases with the increase of the fluence regardless of ion implantation species. © 2003 American Institute of Physics.
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68.35.Md Surface thermodynamics, surface energies
61.80.Jh Ion radiation effects
61.82.Pv Polymers, organic compounds
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.30.Jw Organic compounds, polymers

Precipitation-induced photostimulated luminescence in CsBr:Eu2+

P. Hackenschmied, G. Schierning, M. Batentschuk, and A. Winnacker

J. Appl. Phys. 93, 5109 (2003); http://dx.doi.org/10.1063/1.1563303 (4 pages) | Cited 24 times

Online Publication Date: 16 April 2003

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This article concerns the unusual storage mechanism in the x-ray storage phosphor CsBr:Eu2+. Data are presented and discussed regarding the identification of x-ray diffraction patterns and the photostimulated luminescence (PSL) intensity as a function of the annealing temperature for various Eu concentrations of CsBr:Eu2+ powder crystals and the spatial correlation of trapped electrons and holes. These results together with an analysis of previous literature data enable us to propose a model explaining the formation of phases which are active in the PSL-process of the CsBr:Eu2+ storage phosphor. © 2003 American Institute of Physics.
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78.55.Fv Solid alkali halides
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
64.75.-g Phase equilibria

Determination of nanostructures and mechanical properties on the surface of molybdenum dithiocarbamate and zinc dialkyl-dithiophosphate tribochemical reacted films using atomic force microscope phase imaging technique

Jiping Ye, Makoto Kano, and Yoshiteru Yasuda

J. Appl. Phys. 93, 5113 (2003); http://dx.doi.org/10.1063/1.1563040 (5 pages) | Cited 5 times

Online Publication Date: 16 April 2003

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Nanostructures and mechanical properties on the surface of two kinds of tribofilm formed from zinc dialkyl-dithiophosphate (ZDDP) and molybdenum dithiocarbamate (MoDTC) additives, which exhibited obviously different friction coefficients in a pin-on-disc test, were determined by using an atomic force microscopy (AFM) phase imaging technique. The level of interactive force between the tip and sample was modulated for distinguishing well-defined structures and mechanical properties of individual components not only on the uppermost surface but also in the underlying area near the surface in the AFM tapping mode. It was found that the MoDTC/ZDDP tribofilm possessed a lower surface modulus than the ZDDP film in the elastic deformation range. Most importantly, nanostrips oriented in the sliding direction were found in the MoDTC/ZDDP tribofilm at a depth of around 10 nm from the surface. These nanostrips possessed lower shearing stress than the surface matrix and formed the inner skin layer, which exhibited lower friction behavior than that of the ZDDP tribofilm. These results agreed with our recent nanoindentation and nanoscratch measurements for estimating the mechanical and frictional properties of MoDTC/ZDDP and ZDDP tribofilms. These findings and previous surface analytical results suggest that the nanostrips act as a type of solid lubricant, such as MoS2 single sheets, to lower the boundary friction coefficient. © 2003 American Institute of Physics.
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81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness
62.25.-g Mechanical properties of nanoscale systems
68.60.Bs Mechanical and acoustical properties
81.07.Bc Nanocrystalline materials
68.37.Ps Atomic force microscopy (AFM)
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

High resolution electrical studies of vacancy-rich and interstitial-rich regions in ion-implanted silicon

N. Abdelgader and J. H. Evans-Freeman

J. Appl. Phys. 93, 5118 (2003); http://dx.doi.org/10.1063/1.1564286 (7 pages) | Cited 12 times

Online Publication Date: 16 April 2003

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A combination of high resolution Laplace deep level transient spectroscopy (LDLTS) and direct capture cross-section measurements has been used to investigate whether deep electronic states related to interstitial-type defects introduced by ion implantation originated from point or extended defects, prior to any annealing. n-type silicon was implanted with doses of 1×109 cm−2 of silicon, germanium, or erbium, and comparison was made with proton- and electron-irradiated material. When measured by LDLTS at 225 K, the region of the implant thought to contain mostly vacancy-type defects exhibited a complex spectrum with five closely spaced defect-related energy levels, with energies close to EC-400 meV. The region nearer the tail of the implant, which should be dominated by interstitial-type defects, exhibited a simpler LDLTS spectrum with three closely spaced levels being recorded, again with energies centered on EC-400 meV. Annealing at 180 °C did not completely remove any of the defect peaks, suggesting that the energy levels were not due to the simple vacancy-phosphorus center. Direct electron capture cross-section measurements revealed that the defects in the tail of the implanted volume, prior to any annealing, were not simple point defects, as they exhibited nonexponential capture properties. This is attributed to the presence of extended defects in this region. By contrast, defects with the same activation energy in proton- and electron-irradiated silicon exhibited point-defect-like exponential capture. © 2003 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.J- Point defects and defect clusters
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing

Effect of hydrogen-related impurities on the thermal behavior of mechanical stress in silicon oxides suitable for integrated optics

C. Domínguez, J. A. Rodríguez, M. Riera, A. Llobera, and B. Díaz

J. Appl. Phys. 93, 5125 (2003); http://dx.doi.org/10.1063/1.1563297 (6 pages) | Cited 8 times

Online Publication Date: 16 April 2003

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Silicon oxide films were deposited by plasma enhanced chemical vapor deposition on crystalline silicon substrates from a mixture of silane and nitrous oxide. Substrate temperature and [N2O]/[SiH4] precursor gas flow ratio were varied between 200–350 °C and 5.5–110, respectively. Rapid thermal annealing at 900 °C to achieve impurity effusion led to significant changes in the dependence of the mechanical stress with the gas flow ratio R. In situ stress measurements during thermal cycles up to 300 °C as well as measurements of transmission infrared spectra for the as-deposited and annealed samples were performed. The changes in the stress behavior were explained considering the layer shrinkage resulting from the effusion of the different impurities present and the network rearrangement taking place during rapid thermal annealing, for different ranges of flow ratios. © 2003 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.66.Nk Insulators
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.79.Wc Optical coatings
42.70.Km Infrared transmitting materials
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
78.30.Hv Other nonmetallic inorganics
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