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15 Oct 2000

Volume 88, Issue 8, pp. 4469-4921

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Z-scan determination of the third-order optical nonlinearity of gold:silica nanocomposites

S. Debrus, J. Lafait, M. May, N. Pinçon, D. Prot, C. Sella, and J. Venturini

J. Appl. Phys. 88, 4469 (2000); http://dx.doi.org/10.1063/1.1290260 (7 pages) | Cited 47 times

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Third-order nonlinear optical properties of Au:SiO2 thin films were studied at the surface plasmon resonance wavelength by the z-scan technique using a nanosecond laser. Films were prepared by a multilayer deposition sputtering technique. They were composed of 2 nm mean diam gold particles, with a metal volume fraction of 20%. Z-scan measurements performed both with and without aperture showed a very large nonlinear absorption masking the nonlinear refraction. The nonlinear absorption coefficient β was found to be negative and equal to −1.1×10−2 cm/W. The different mechanisms contributing to this absorption are discussed and the large value of β is correlated to the duration of the laser pulses. Moreover, it is shown that a mean field theory is not appropriate to evaluate the effective susceptibility at high metal concentrations. © 2000 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Sq Composite materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Photochromic effect in near-stoichiometric LiNbO3 and two-color holographic recording

Myeongkyu Lee, Shunji Takekawa, Yasunori Furukawa, Yoshishige Uchida, Kenji Kitamura, Hideki Hatano, and Satoru Tanaka

J. Appl. Phys. 88, 4476 (2000); http://dx.doi.org/10.1063/1.1311807 (10 pages) | Cited 10 times

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We have observed that newly developed near-stoichiometric LiNbO3 crystals have three different types of energy levels: ultraviolet (UV) absorption centers just above the valence band, metastable shallow electron traps slightly below the conduction band, and deep traps located about 1.9 eV below the conduction band. Irradiation with UV light induced a stable absorption band extending from λ ≈650 nm to the absorption edge, which is caused by the photoinduced charge transfer from UV-sensitive absorption centers to deep traps via the conduction band. The electron lifetimes at shallow and deep traps could be controlled by doping elements and concentrations. Based on these favorable energy states, nonvolatile two-color holographic recording has been carried out by use of 852 nm recording beams and UV gating light. Nonvolatile readout by a single 852 nm beam was demonstrated for several hours. It was found that two-color recording from the pre-exposed, colored state can also be an attractive way of achieving nonvolatile readout. In this article, we investigate the photochromic effect observed in near-stoichiometric LiNbO3 and its use in two-color holographic recording. © 2000 American Institute of Physics.
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42.70.Ln Holographic recording materials; optical storage media
42.40.Ht Hologram recording and readout methods
71.55.Ht Other nonmetals
78.20.-e Optical properties of bulk materials and thin films
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators

Selective modification of the Er3+ 4I11/2 branching ratio by energy transfer to Eu3+

C. Strohhöfer, P. G. Kik, and A. Polman

J. Appl. Phys. 88, 4486 (2000); http://dx.doi.org/10.1063/1.1311824 (5 pages) | Cited 14 times

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We present an investigation of Er3+ photoluminescence in Y2O3 waveguides codoped with Eu3+. As a function of europium concentration we observe an increase in decay rate of the erbium 4I11/2 energy level and an increase of the ratio of photoluminescence emission from the 4I13/2 and 4I11/2 states. Using a rate equation model, we show that this is due to an energy transfer from the 4I11/2→4I13/2 transition in erbium to europium. This increases the branching ratio of the 4I11/2 state towards the 4I13/2 state and results in a higher steady state population of the first excited state of erbium. Absolute intensity enhancement of the 4I13/2 emission is obtained for europium concentrations between 0.1 and 0.3 at. %. In addition, the photoluminescence due to upconversion processes originating from the 4I11/2 state is reduced. Using such state-selective energy transfer the efficiency of erbium doped waveguide amplifiers can be increased. © 2000 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
42.65.Yj Optical parametric oscillators and amplifiers
42.65.Wi Nonlinear waveguides
42.79.Hp Optical processors, correlators, and modulators

Dissociating the effect of different disturbances on the band gap of a two-dimensional photonic crystal

G. Guida, T. Brillat, A. Ammouche, F. Gadot, A. De Lustrac, and A. Priou

J. Appl. Phys. 88, 4491 (2000); http://dx.doi.org/10.1063/1.1290451 (7 pages) | Cited 6 times

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In this article, we dissociate the effect of the three generic disturbances on the band gap of a bidimensional metallic photonic crystal made of parallel rods. The disturbances are investigated separately. They are deviations from the perfectly periodic position, the angle between rods constituting the photonic crystal and different sizes in rod diameters. Numerical simulations and experimental measurements have been performed in the microwave region and the results compared. The effects of these disturbances on a localized state are discussed as well. When the disturbance level is weak (i.e., a few percent), the band structure is conserved: the slopes at the edge and the band-gap width are the same as for the perfect structure. By contrast, the bandpass is reduced by about −1 dB. For an important disturbance the crystal becomes practically unusable due to the deep random modifications of its band structure. In all cases when the band gap exists, the transmission peak associated with the localized state is present. © 2000 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics

Thickness-shear mode quartz crystal resonators in viscoelastic fluid media

A. Arnau, Y. Jiménez, and T. Sogorb

J. Appl. Phys. 88, 4498 (2000); http://dx.doi.org/10.1063/1.1309122 (9 pages) | Cited 5 times

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An extended Butterworth–Van Dyke (EBVD) model to characterize a thickness-shear mode quartz crystal resonator in a semi-infinite viscoelastic medium is derived by means of analysis of the lumped elements model described by Cernosek et al. [R. W. Cernosek, S. J. Martin, A. R. Hillman, and H. L. Bandey, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 45, 1399 (1998)]. The EBVD model parameters are related to the viscoelastic properties of the medium. A capacitance added to the motional branch of the EBVD model has to be included when the elastic properties of the fluid are considered. From this model, an explicit expression for the frequency shift of a quartz crystal sensor in viscoelastic media is obtained. By combining the expressions for shifts in the motional series resonant frequency and in the motional resistance, a simple equation that relates only one unknown (the loss factor of the fluid) to those measurable quantities, and two simple explicit expressions for determining the viscoelastic properties of semi-infinite fluid media have been derived. The proposed expression for the parameter Δf/ΔR is compared with the corresponding ratio obtained with data computed from the complete admittance model. Relative errors below 4.5%, 3%, and 1.2% (for the ratios of the load surface mechanical impedance to the quartz shear characteristic impedance of 0.3, 0.25, and 0.1, respectively), are obtained in the range of the cases analyzed. Experimental data from the literature are used to validate the model. © 2000 American Institute of Physics.
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77.65.Fs Electromechanical resonance; quartz resonators
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
07.10.-h Mechanical instruments and equipment
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Mass spectrometric characterization of BCl3/SF6 plasmas

Y.-S. Lee, J. F. Sia, and K. J. Nordheden

J. Appl. Phys. 88, 4507 (2000); http://dx.doi.org/10.1063/1.1309036 (3 pages) | Cited 1 time

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Significant increases in the etch rates of both GaAs and GaN have been observed with the addition of SF6 to BCl3 plasmas. Mass spectrometric characterization of neutrals in these gas mixtures shows that increasing the SF6 percentage in the flow enhances the dissociation of BCl3, resulting in nearly 100% dissociation at 70% SF6. This increased dissociation is believed to be due to electron attachment heating. Both Cl and Cl2 mass intensities also maximize at 70% SF6. The detection of BClF and BCl2F suggest the possibility of reactions occurring between BCl and BCl2 radicals and fluorine, which may inhibit the recombination of Cl. © 2000 American Institute of Physics.
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52.70.Nc Particle measurements
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
81.65.Cf Surface cleaning, etching, patterning
34.80.Lx Recombination, attachment, and positronium formation
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions

Time evolution of ion energy distributions and optical emission in pulsed inductively coupled radio frequency plasmas

Martin Misakian, Eric Benck, and Yicheng Wang

J. Appl. Phys. 88, 4510 (2000); http://dx.doi.org/10.1063/1.1311827 (8 pages)

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This article reports the results of time-resolved measurements of ion energy distributions (IEDs), relative ion densities, as well as optical emissions and electrical characteristics in pulsed inductively coupled plasmas for the simple gas mixture of oxygen and argon (50%Ar:50%O2). The peak radio frequency power, frequency, repetition rate, and duty cycle were 200 W, 13.56 MHz, 500 Hz, and 85%, respectively. Examination of the time evolution of the data over the pulse cycle indicates that when the plasma is energized, it begins in the dim (E) mode undergoing at first slow changes in certain plasma parameters. After about 1.2 ms, a sudden transition to the bright (H) mode occurs. The characteristics of the IEDs are consistent with an average plasma potential profile that has (a) a relatively large collisionless sheath and narrow presheath during the dim mode and (b) a very narrow sheath and greatly extended presheath during the bright mode; the ion mean free path influences the peak position of the IED during the bright mode. For most of the pulse cycle, the relative abundances of the ions Ar+, O2+, and O+ maintain the relation %O2+⩾%Ar+>%O+.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Pi High-frequency and RF discharges
52.25.-b Plasma properties
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Fi Transport properties

Predictive study of a plasma structure and function in reactive ion etcher driven by very high frequency: Validity of an extended two-dimensional relaxation continuum model

Kazunobu Maeshige, Masao Hasebe, Yukio Yamaguchi, and Toshiaki Makabe

J. Appl. Phys. 88, 4518 (2000); http://dx.doi.org/10.1063/1.1310180 (7 pages) | Cited 6 times

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The plasma structure and physical function of a narrow gap reactive ion etcher (RIE), consisting of capacitively coupled parallel plates driven at 100 MHz, have been predicted in a proper manner by an extended relaxation continuum model including gas flow and sputtered particle transport from the substrate. Monitoring the spatiotemporal excitation rate gives validity to the use of the continuum model even at 50 mTorr under higher power condition mainly maintained by an ionization multiplication of the secondary electrons ejected from the powered electrode by ion impacts. The plasma structures are testified by comparing the two-dimensional net excitation rate of Ar(3p5) with the experimental computerized tomography image. A nonvolatile particle transport successive to the physical etching on the substrate has been predicted in the RIE under a feed gas flow. © 2000 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.65.Cf Surface cleaning, etching, patterning
52.25.Fi Transport properties
52.80.Pi High-frequency and RF discharges
52.65.Cc Particle orbit and trajectory
52.40.Hf Plasma-material interactions; boundary layer effects
52.30.-q Plasma dynamics and flow

Formation and annihilation of H-point defect complexes in quenched Si doped with C

Naoki Fukata and Masashi Suezawa

J. Appl. Phys. 88, 4525 (2000); http://dx.doi.org/10.1063/1.1312841 (6 pages) | Cited 3 times

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We investigated the formation and annihilation of H-point defect complexes formed in C-doped Si by heating at high temperatures followed by quenching in hydrogen gas. Specimens of C-doped Si were sealed in quartz capsules together with hydrogen (H) gas, at pressure 0.8–1.5 atm at high temperature, and were heated at high temperature for 1 h followed by quenching in water. We measured their optical absorption spectra at about 7 K with an Fourier transform infrared spectrometer. We observed several optical absorption peaks due to H-point defect complexes. The optical absorption peaks observed at 2192 and 2203 cm−1 were assigned to the Si–H stretching mode of three hydrogen atoms bound to a vacancy (VH3 defect). The formation of the VH4 defect is due to the reaction between H and the VH3 defect. From isothermal annealing experiments, the activation energy for the dissociation of the VH4 defect was determined to be about 2.5 eV. © 2000 American Institute of Physics.
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71.55.Cn Elemental semiconductors
78.40.Fy Semiconductors
61.72.J- Point defects and defect clusters
61.72.Yx Interaction between different crystal defects; gettering effect

Growth of arc in high-pressure, pulsed glow discharge by gas density depletion

Go Imada, Kiyoshi Yatsui, and Wataru Masuda

J. Appl. Phys. 88, 4531 (2000); http://dx.doi.org/10.1063/1.1314328 (6 pages) | Cited 5 times

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Effects of gas density depletion on arc formation of high-pressure, pulsed glow discharge have been investigated by eliminating the other factors which may affect the discharge stability, such as shock waves, residual ions, electrode heating, and discharge products. The gas density depletion has been simulated by utilizing a subsonic gas flow between the curved electrodes combined with a convergent nozzle and a divergent diffuser. A comparison has been made on the discharge in the aerodynamically created gas density depletion with the second discharge in the double-pulse discharge within a stable gas. We have found that the large gas density depletion, Δρ/ρ0∼−3.6% corresponding to a pulse repetition rate (PRR) of ∼50 Hz, tends to cause an arc-like filament or an arc without the shocks, ions, electrode heating, and products. However, the second discharge in the double-pulse discharge becomes an arc in much smaller gas density depletion (Δρ/ρ0∼−1.2% corresponding to PRR ∼3 Hz). Therefore, the collapse of high-pressure, pulsed glow discharge is most likely caused by some factor other than the gas density depletion. © 2000 American Institute of Physics.
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52.80.Hc Glow; corona
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Loss kinetics of carbon atoms in low-pressure high density plasmas

Haruhiko Ito, Kungen Teii, Hikaru Funakoshi, Masaru Hori, Toshio Goto, Masafumi Ito, and Takashi Takeo

J. Appl. Phys. 88, 4537 (2000); http://dx.doi.org/10.1063/1.1314307 (5 pages) | Cited 7 times

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Vacuum ultraviolet absorption spectroscopy (VUVAS) with a carbon hollow cathode lamp was applied to the measurement of decay rate of C atom density in the afterglow of CO and CO/H2 inductively coupled plasmas. The transition line used for the measurement was 2p3s 3P2–2p2 3P2 at 165.7 nm. The influence of background absorption by the species in plasma other than C atoms on the transition line of C atoms was found to be negligible. This was clarified by measuring the absorption intensities around the center wavelength of C atoms in plasmas with VUVAS employing a xenon microhollow cathode lamp. Moreover, the dependence of the decay rate of C atom density on pressure revealed that C atoms were dominantly lost at the surface rather than in the gas phase in both CO and CO/H2 plasmas. However, in the case of CO/H2 plasma at higher pressures over about 5.0 Pa, C atoms were lost in the gas phase as well as at the surface. The diffusion constants of C atoms in both CO and CO/H2 plasmas were also determined to be 3.1×104 and 3.7×104 cm2 Pa s−1, respectively. © 2000 American Institute of Physics.
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52.80.Hc Glow; corona
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
32.30.Jc Visible and ultraviolet spectra
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Fi Transport properties
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Hydrogen dynamics in SiO2 triggered by electronic excitations

Ayumi Yokozawa and Yoshiyuki Miyamoto

J. Appl. Phys. 88, 4542 (2000); http://dx.doi.org/10.1063/1.1289815 (5 pages) | Cited 5 times

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Ab initio approaches have been used to study microscopic mechanisms of the dielectric degradation of SiO2 induced by electronic excitation. In this article, we focus on the possibility of H dissociation from H-terminated O vacancies in SiO2 induced by Si–H σ→σ∗ excitation. To take the finite lifetime of this excitation into account, real-time electron dynamics were treated by solving the time-dependent Schrödinger equation coupled with Newton’s equations for ions. We found that the decay-time constant of the Si–H σ→σ∗ excitation is on the order of 10 fs, which is too short to cause direct H dissociation. Therefore, not only the electronic excitation, but also thermal assistance and/or transport of the excited electron from SiO2 to the Si substrate appears responsible for the Si–H bond breaking and subsequent SiO2 degradation. © 2000 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.22.Jp Dielectric breakdown and space-charge effects
71.55.Ht Other nonmetals
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ng Insulators
77.55.-g Dielectric thin films
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
61.72.J- Point defects and defect clusters

Boron-interstitial silicon clusters and their effects on transient enhanced diffusion of boron in silicon

S. Solmi, M. Bersani, M. Sbetti, J. Lundsgaard Hansen, and A. Nylandsted Larsen

J. Appl. Phys. 88, 4547 (2000); http://dx.doi.org/10.1063/1.1311826 (6 pages) | Cited 15 times

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The nature of ion-implantation induced clusters of boron and silicon-self interstitials (BICs), and their effects on transient enhanced diffusion (TED) of B in Si have been investigated in samples predoped with B at different concentrations. Excess Si interstitials have been introduced by Si+ implantation at 60 keV with doses of 1 and 5×1014 cm−2. The B diffusivity and the amount of B trapped in the clusters have been evaluated from the best fits of simulation-prediction profiles to experimental B profiles, after annealing at 740 and 800 °C for different times. Our results show that the BICs in the beginning act as a sink for interstitials, strongly reducing the TED in the early phases of the annealing. However, being more stable than the Si-interstitial clusters and the {113} defects, they dissolve slowly and can, therefore, sustain a moderate Si-interstitial supersaturation for longer annealing times, even when the Si-interstitial defects are completely dissolved. The data show that the amount of B in the BICs is higher than that of the interstitials; we estimate an average ratio between the B and interstitial concentrations to be about 1.5. © 2000 American Institute of Physics.
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66.30.J- Diffusion of impurities
81.05.Cy Elemental semiconductors
61.72.J- Point defects and defect clusters
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.uf Ge and Si
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
61.72.S- Impurities in crystals
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments

Determination of the direction of the “easy” axis at a twisted nematic liquid crystal-wall using half-leaky guided modes

F. Z. Yang, H. F. Cheng, H. J. Gao, and J. R. Sambles

J. Appl. Phys. 88, 4553 (2000); http://dx.doi.org/10.1063/1.1311812 (5 pages) | Cited 1 time

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Theoretical analysis and numerical modeling indicate that, under high fields, the director of a thin region of liquid crystal close to the wall of a twisted nematic cell returns to the “easy” axis on the interface. Polarization conversion reflectivity signals are recorded for half-leaky guided modes from a twisted nematic cell subject to high ac fields. By fitting model theory to reflectivities recorded for a particular region of incidence angles, the director twist at the cell walls is deduced. In the high-field limit, this then gives the original director alignment axis, the easy axis, at the wall of a twisted nematic cell. © 2000 American Institute of Physics.
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42.70.Df Liquid crystals
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures

A deep level transient spectroscopy study of beryllium implanted n-type 6H-SiC

X. D. Chen, S. Fung, C. D. Beling, M. Gong, T. Henkel, H. Tanoue, and N. Kobayashi

J. Appl. Phys. 88, 4558 (2000); http://dx.doi.org/10.1063/1.1287232 (5 pages) | Cited 5 times

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Beryllium implantation induced defects in 6H-SiC pn junctions have been investigated by deep level transient spectroscopy. Five defect centers labeled BE1, BE2, BE3, BE4, and BE5 have been detected in the temperature range 100–450 K. A comparative study has also been performed in low beryllium doped n-type 6H-SiC, which proved that the BE1, BE2, and BE3 centers are electron traps located at 0.34, 0.44, and 0.53 eV, respectively, below the conduction band edge. On the other hand, the BE4 and BE5 centers have been found to be hole traps which are situated at 0.64 and 0.73 eV, respectively, above the valence band edge. Possible defect configurations associated with these deep levels are discussed. © 2000 American Institute of Physics.
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71.55.Ht Other nonmetals
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Complete set of deep traps in semi-insulating GaAs

M. Pavlović, U. V. Desnica, and J. Gladić

J. Appl. Phys. 88, 4563 (2000); http://dx.doi.org/10.1063/1.1308072 (8 pages) | Cited 14 times

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Reevaluation and recalculation of thermally stimulated current (TSC) data from semi-insulating (SI) GaAs, published by many different authors over a period of three decades were done by means of the new analytical method, simultaneous multiple peak analysis (SIMPA). The SIMPA procedure clearly resolved contributions from various overlapping TSC peaks and enabled the precise determination of signatures (activation energy, Ea and capture cross section, σ) of all observed deep traps. The analyzed TSC spectra refer to SI GaAs samples that have been grown/treated in quite different ways (various growth techniques, growth under As or Ga rich conditions, different annealing procedures, irradiation with neutrons, γ rays, etc.). Although the SIMPA procedure was applied to apparently quite different TSC spectra, in all cases excellent fits were achieved, with the unique set (or subset from it) of eleven different deep traps, the only difference being in relative and absolute concentrations of traps. Despite a broad variety of samples analyzed in this article, the set of deep traps obtained is the same as the one being previously seen in the narrow range of SI GaAs samples. This finding suggests that this set of traps is a finite and complete set of all defects with deep levels in SI GaAs. It was also concluded that these defects are primarily complexes containing simple native defects. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Vibrational density of states of nanocrystalline iron and nickel

Ennio Bonetti, Luca Pasquini, Euro Sampaolesi, Antonio Deriu, and Giovanna Cicognani

J. Appl. Phys. 88, 4571 (2000); http://dx.doi.org/10.1063/1.1311310 (5 pages) | Cited 17 times

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We present an experimental determination of the vibrational density of states in nanocrystalline Fe and Ni by inelastic neutron scattering. Nanocrystalline specimens with different grain size and microstrain have been prepared by ball milling and thermal annealing. The vibrational density of states has been extracted from neutron time-of-flight spectra obtained with the spectrometer IN6 at the Institute Laue–Langevin. In comparison with reference coarse-grained specimens measured in the same conditions the nanocrystalline specimens exhibit: (i) a modest increase in the population of low-frequency modes and (ii) a distinct broadening of the transverse and longitudinal phonon peaks. The former feature is related to the presence of interface modes and it is critically compared with other observations in pure nanocrystalline metals. The latter is discussed in terms of reduced phonon lifetime due to the nanometric size of the crystallites. © 2000 American Institute of Physics.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
68.35.Ja Surface and interface dynamics and vibrations
61.05.fg Neutron scattering (including small-angle scattering)
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.05.Bx Metals, semimetals, and alloys

Enhanced diffusion in laser-annealed nonstoichiometric AlAs/GaAs heterostructures

S. Balasubramanian, D. D. Nolte, and M. R. Melloch

J. Appl. Phys. 88, 4576 (2000); http://dx.doi.org/10.1063/1.1308104 (6 pages) | Cited 1 time

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Transient enhanced intermixing, induced by a focused laser beam, has been observed in arsenic-rich nonstoichiometric AlAs/GaAs quantum wells grown at a low substrate temperature around 300 °C. The intermixing is attributed to a supersaturated concentration of group-III vacancies incorporated into the crystal lattice by the low temperature growth conditions. The intermixing is enhanced by several orders of magnitude relative to diffusion in stoichiometric structures grown at ordinary substrate temperatures. Experimentally observed excitonic blueshifts in laser annealed quantum wells, and the diffusion lengths that are derived from them, are in agreement with those obtained by conventional rapid thermal annealing. Laser annealing provides the capability of spatially patterning integrated optical devices. © 2000 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.72.Cc Kinetics of defect formation and annealing
68.35.Fx Diffusion; interface formation
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.-y Excitons and related phenomena

Mapping the three-dimensional strain field around a microindentation on silicon using polishing and Raman spectroscopy

Pascal Puech, Stéphane Pinel, Renato G. Jasinevicius, and Paolo Sergio Pizani

J. Appl. Phys. 88, 4582 (2000); http://dx.doi.org/10.1063/1.1289817 (4 pages) | Cited 13 times

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The strain field around a Vickers microindentation of crystalline silicon (001) has been mapped using Raman spectroscopy. The nature of the three-dimensional strain field of the microindentation was determined by comparing the parallel and crossed scattering geometries and applying the relations between the optical phonon frequency shift and strain. A surface layer (2 μm) was then removed by abrasive chemical polishing. The strain is preserved by the polishing process and information on microindentation depth is obtained. The produced maps give a good idea of the strain field after unloading. We find a quasicircular zone of plastic deformation where the strain follows a 1/r law. © 2000 American Institute of Physics.
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62.20.M- Structural failure of materials
68.35.Gy Mechanical properties; surface strains
81.65.Ps Polishing, grinding, surface finishing
78.30.Am Elemental semiconductors and insulators
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
62.20.F- Deformation and plasticity
07.10.Pz Instruments for strain, force, and torque
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Relaxation model of coherent island formation in heteroepitaxial thin films

R. Arief Budiman and Harry E. Ruda

J. Appl. Phys. 88, 4586 (2000); http://dx.doi.org/10.1063/1.1311305 (9 pages) | Cited 18 times

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A model for coherent island formation in heteroepitaxial thin films is presented by focusing on the interplay between surface and strain relaxation energies. The resulting free energy is mapped onto the Landau free energy, and yields the local surface slope as the order parameter for island formation. Isotropic islands are found to exhibit second-order transitions. We argue that our model is appropriate for describing the nucleation and stability of island formation. The spinodal curve indicates that there exists an unstable regime where spinodal-like islands emerge as low-slope islands, even in a highly mismatched heteroepitaxial system. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Aa Theory and models of film growth
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Md Surface thermodynamics, surface energies
65.20.-w Thermal properties of liquids
65.40.gd Entropy
68.35.Rh Phase transitions and critical phenomena
64.60.Q- Nucleation

Monte Carlo study of kinetic smoothing during dissolution and etching of the Kossel (100) and silicon (111) surfaces

E. van Veenendaal, P. van Beurden, W. J. P. van Enckevort, E. Vlieg, J. van Suchtelen, and M. Elwenspoek

J. Appl. Phys. 88, 4595 (2000); http://dx.doi.org/10.1063/1.1289812 (10 pages) | Cited 7 times

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We have analyzed the asymmetry between growth and dissolution using Monte Carlo simulations of flat and vicinal (100) surfaces of a Kossel crystal. We find that at a high driving force dissolution is very anisotropic and nearly atomically flat surfaces are produced, if the nearest-neighbor bond strength is sufficiently large. This effect we call kinetic smoothing. For wet-chemical etching of the Si(111) surface, the chemical-etch reaction determines the annihilation rate constants. If the differences between the rate constants for removal of atoms from kink, step, and terrace sites are large enough, then we observe smooth surfaces and anisotropic etching, i.e., kinetic smoothing. If etching is anisotropic, knowledge of the annihilation rate constants suffices to find an analytical expression for the etch rate as a function of misorientation. This expression can be used to fit experimental etch rates for etching of vicinal Si(111) in potassium hydroxide. © 2000 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Cf Surface cleaning, etching, patterning
81.05.Cy Elemental semiconductors
02.70.Rr General statistical methods

Composition-structure correlations in strained FexMn1−x/Ir superlattices

E. Snoeck, H. Ardhuin, M. J. Casanove, H. Fischer, S. Andrieu, M. Piecuch, K. Suenaga, and C. Colliex

J. Appl. Phys. 88, 4605 (2000); http://dx.doi.org/10.1063/1.1311301 (7 pages)

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The structural and chemical characteristics of FexMn1−x alloys in [FexMn1−x/Ir(001)] superlattices with iron contents of x=0.3, 0.5 and 0.9 are investigated at the nanometer scale by high resolution transmission electron microscopy and electron energy loss spectroscopy techniques. The transmission electron microscopy experiments show that pseudomorphic growth of the alloy on Ir is only achieved for x⩾0.5. Layers with iron content x=0.5 display, however, structural inhomogeneities and a weak Mn segregation effect. Layers with a high iron content, Fe0.9Mn0.1 are seen to present a quasiperiodic lattice modulation. We suggest that this modulation is associated with spinodal decomposition. All these structural investigations indicate that, in epitaxial strained thin layers, the FexMn1−x alloy reproduces almost all of the complex FexMn1−x phase diagram with, however, a marked shift towards the low Fe content regions. © 2000 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Ct Interface structure and roughness
79.20.Kz Other electron-impact emission phenomena
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
81.30.Bx Phase diagrams of metals, alloys, and oxides

Thermally detected optical absorption, reflectance, and photoreflectance of In(As,P)/InP quantum wells grown by gas source molecular beam epitaxy

P. Disseix, C. Payen, J. Leymarie, A. Vasson, and F. Mollot

J. Appl. Phys. 88, 4612 (2000); http://dx.doi.org/10.1063/1.1309050 (7 pages) | Cited 4 times

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This work reports an extensive optical study of a series of In(As,P)/InP strained quantum wells grown by gas source molecular beam epitaxy with various thicknesses and compositions. Thermally detected optical absorption, reflectance, and photoreflectance measurements have been performed in order to determine all the exciton energies. An envelope function model including band nonparabolicity, intervalence band coupling, and also possible group V element exchange at the interfaces, is used to interpret the experimental data. The fit of the optical transition energies leads to an accurate determination of the crucial structural and optical parameters. The arsenic concentration inside the wells is evaluated and the conduction band offset ratio (Qc=0.70) as well as the bowing parameter of In(As,P) (C=0.14 eV) are determined. These studies also provide useful information about the nanometer-scale P–As interface mixing. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.40.Ha Other nonmetallic inorganics
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
78.20.-e Optical properties of bulk materials and thin films
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Selective control of self-organized In0.5Ga0.5As/GaAs quantum dot properties: Quantum dot intermixing

D. Bhattacharyya, A. Saher Helmy, A. C. Bryce, E. A. Avrutin, and J. H. Marsh

J. Appl. Phys. 88, 4619 (2000); http://dx.doi.org/10.1063/1.1311828 (4 pages) | Cited 4 times

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Selective postgrowth control of the photoluminescence (PL) wavelength has been demonstrated for a single layer self-organized In0.5Ga0.5As/GaAs quantum dot (QD) structure. This was achieved by rapid thermal processing of dots using different dielectric caps. Selective band gap shifts of over 100 meV were obtained between samples capped with sputtered and plasma enhanced silica deposition, with the band gap shift under regions covered with plasma enhanced chemical vapor deposition SiO2 less than 70 meV. The effects of different caps on the PL linewidth were also observed. The differential band gap shift will enable the integration of passive and active devices in QD systems. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Ct Interface structure and roughness
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Electronic transport in thin film electroluminescence of SrS:Ce

Chunxiang Xu, Yiping Cui, and Xurong Xu

J. Appl. Phys. 88, 4623 (2000); http://dx.doi.org/10.1063/1.1309124 (5 pages) | Cited 3 times

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Thin film electroluminescent (TFEL) devices based on the scheme of SiO2/SrS:Ce/SiO2/SiO were fabricated, and blue–green emission was observed in the devices. The electronic transport process is strongly affected by the mixing interaction between the conduction band of SrS and the excited state of Ce3+. The photoluminescent excitation and the wave forms of time-dependent electroluminescent emission show that recombinant luminescence is the main process in SrS:Ce TFEL. The experimental results reveal that the excitation mechanism is related to the sulfur vacancies. © 2000 American Institute of Physics.
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78.60.Fi Electroluminescence
71.55.Ht Other nonmetals
73.61.Ng Insulators
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
78.66.Nk Insulators
85.60.Jb Light-emitting devices
78.47.-p Spectroscopy of solid state dynamics
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Hx Other solid inorganic materials
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