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1 Oct 2004

Volume 96, Issue 7, pp. 3601-4023

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Optical surface second harmonic measurements of isotropic thin-film metals: Gold, silver, copper, aluminum, and tantalum

Debra Krause, Charles W. Teplin, and Charles T. Rogers

J. Appl. Phys. 96, 3626 (2004); http://dx.doi.org/10.1063/1.1786341 (9 pages) | Cited 24 times

Online Publication Date: 23 September 2004

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We have studied optical surface second harmonic generation and have determined the magnitude and relative phase of the second-order susceptibility tensor elements for thermally evaporated gold, and sputtered silver, copper, aluminum, and tantalum. The second harmonic data are understood using an isotropic model of the surfaces. The measurements of the parameters from this nonlinear optical characterization, in conjunction with linear optical characterization of the samples, allow us to extract the elements of the tensors. The typical size of χ⊥(2), the tensor element that produces the surface current perpendicular to the surface and is the largest surface element, ranges from 3(±1)×10−12 cm2∕statvolt for an aluminum sample with 24(±4) math rms surface roughness to 1.1(±0.1)×10−13 cm2∕statvolt for a copper sample with 5(±1) math rms surface roughness. Film preparation and associated surface roughness can reproducibly change the values of χ(2); increasing sample roughness increases the magnitudes of the tensor elements. In agreement with previous aluminum measurements, we again find that the tensor elements associated with creating the second harmonic currents normal to the surface are of roughly the theoretically predicted magnitude, but that the elements associated with creating the second harmonic currents parallel to the surface and in the bulk are an order of magnitude smaller than expected.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Bz Metals and metallic alloys
42.25.Bs Wave propagation, transmission and absorption
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ch Permittivity (dielectric function)
42.65.An Optical susceptibility, hyperpolarizability
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.De Metallic surfaces

Systematic pump-probe terahertz wave emission spectroscopy of a photoconductive antenna fabricated on low-temperature grown GaAs

R. Yano, H. Gotoh, Y. Hirayama, and S. Miyashita

J. Appl. Phys. 96, 3635 (2004); http://dx.doi.org/10.1063/1.1786667 (4 pages) | Cited 4 times

Online Publication Date: 23 September 2004

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We performed pump-probe terahertz (THz) wave emission spectroscopy for a photoconductive antenna fabricated on low-temperature grown GaAs. When the pump pulse intensity was increased, the THz wave generated by the probe pulse showed an increase of the spectral amplitude in the low-frequency regime (<0.5 THz) and a decrease of the peak amplitude. The increase of the spectral amplitude and the decrease of the peak amplitude are related to the carrier density generated by the pump pulse, and are explained by the increase of the carrier trap time due to the saturation of the defect levels and by the carrier-carrier scattering process between carriers in the conduction band, respectively.
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84.40.Ba Antennas: theory, components and accessories
78.70.Gq Microwave and radio-frequency interactions
72.20.Fr Low-field transport and mobility; piezoresistance
72.40.+w Photoconduction and photovoltaic effects
85.60.-q Optoelectronic devices
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments

Optical properties of epitaxial lateral overgrowth GaN structures studied by Raman and cathodoluminescence spectroscopies

O. Martínez, M. Avella, J. Jiménez, B. Gérard, R. Cuscó, and L. Artús

J. Appl. Phys. 96, 3639 (2004); http://dx.doi.org/10.1063/1.1786670 (6 pages) | Cited 7 times

Online Publication Date: 23 September 2004

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The properties of epitaxial lateral overgrowth (ELO) GaN layers were studied by means of cathodoluminescence (CL), micro-Raman spectroscopies, and transmission electron microscopy (TEM). CL shows a strong enhancement of the luminescence emission in the ELO regions, where TEM showed the absence of dislocations. The CL enhancement observed is mostly due to the yellow luminescence (YL) band, which contrasts with the good crystal quality observed in the ELO regions by TEM and Raman spectroscopy. Local CL spectra in the ELO regions showed a different behavior of the near band edge emission in relation to the buffer layers and central part of the vertical growth region. Donor-acceptor pair recombination is enhanced in the ELO regions. The Raman spectra indicate a low strain level in the ELO regions. Plasmon-coupled modes are not observed in these areas, indicating the absence of free carriers. CL and Raman observations could thus be explained in terms of the good crystalline quality of the ELO regions, in which the incorporation of impurities is electrically compensated by the formation of deep acceptors, probably VGa, responsible as well for the enhancement of the YL band.
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81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
71.55.Eq III-V semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Thermoelastic waves in an anisotropic infinite plate

Hussain Al-Qahtani and Subhendu K. Datta

J. Appl. Phys. 96, 3645 (2004); http://dx.doi.org/10.1063/1.1776323 (14 pages) | Cited 16 times

Online Publication Date: 23 September 2004

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An analysis of the propogation of thermoelastic waves in a homogeneous, anisotropic, thermally conducting plate has been presented in the context of the generalized Lord-Shulman theory of thermoelasticity. Three different methods are used in this analysis: two of them are exact and the third is a semianalytic finite element method (SAFE). In our exact analysis, two different approaches are used. The first one, which is applicable to transversely isotropic plate, is based on introducing displacement potential functions, whereas in the second approach, which is applicable to any triclinic material, we rewrite the governing equations and boundary conditions in a matrix form. Finally, in the SAFE method, the plate is discretized along its thickness using N parallel, homogeneous layers, which are perfectly bonded together. Frequency spectrum and dispersion curves are obtained using the three methods and are shown to agree well with each other. The effects of thermal relaxation time and coupling term are also investigated. Numerical calculations have been presented for a silicon nitride (Si3N4) plate. However, the methods can be used for other materials as well.
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46.70.De Beams, plates, and shells
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
46.25.Hf Thermoelasticity and electromagnetic elasticity (electroelasticity, magnetoelasticity)

Thermal properties of the midinfrared nonlinear crystal LiInSe2

A. P. Yelisseyev, V. A. Drebushchak, A. S. Titov, L. I. Isaenko, S. I. Lobanov, K. M. Lyapunov, V. A. Gruzdev, S. G. Komarov, V. Petrov, and J.-J. Zondy

J. Appl. Phys. 96, 3659 (2004); http://dx.doi.org/10.1063/1.1784616 (7 pages) | Cited 6 times

Online Publication Date: 23 September 2004

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The thermal conductivity and thermal-expansion and thermo-optic coefficients, the knowledge of which is essential for nonlinear optical applications, are measured along the three crystallographic axes of the newly discovered orthorhombic crystal LiInSe2. The latter has a nonlinear susceptibility only a quarter lower than that for the commercially available AgGaS2, but its advantages include ∼4 times higher thermal conductivity, ∼2 times lower thermo-optic coefficients, and the lack of sign inversion in thermal-expansion coefficients.
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65.40.De Thermal expansion; thermomechanical effects
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.An Optical susceptibility, hyperpolarizability
78.30.Hv Other nonmetallic inorganics

Correlation of strain, wing tilt, dislocation density, and photoluminescence in epitaxial lateral overgrown GaN on SiC substrates

N. Gmeinwieser, K. Engl, P. Gottfriedsen, U. T. Schwarz, J. Zweck, W. Wegscheider, S. Miller, H.-J. Lugauer, A. Leber, A. Weimar, A. Lell, and V. Härle

J. Appl. Phys. 96, 3666 (2004); http://dx.doi.org/10.1063/1.1784617 (7 pages) | Cited 15 times

Online Publication Date: 23 September 2004

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Epitaxial lateral overgrown (ELOG) gallium nitride (GaN) on SiC is being studied as a possible substrate for blue laser diodes. A defect density below 2.2×107 cm−2 in the wings, compared to 2×109 cm−2 in the windows, was achieved. Interaction of the overgrown GaN with the SiO2 mask causes a few degree wing tilt and a transition region of high defect density between windows and wings. Diminished PL, strong tensile stress, and a defect correlated line at around 3.4 eV emerge in this up to two-micron-wide transition region. By changing the mask material from SiO2 to SiN we were able to reduce the wing tilt drastically to below 0.7°. This eliminates the defective transition region and extends the low strain and the low defect density area of the ELOG wings. The methods used to study strain, wing tilt, and threading dislocations in the ELOG samples are microphotoluminescence (μPL), transmission electron microscopy, x–ray diffraction, and scanning electron microscope. We also demonstrate the use of the first momentum of the μPL spectra as an effective means to measure strain distribution.
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81.05.Ea III-V semiconductors
68.47.Fg Semiconductor surfaces
78.55.Cr III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
68.60.Bs Mechanical and acoustical properties

Evolution of dislocation structure in the heat affected zone of a nickel-based single crystal

O. M. Barabash, J. A. Horton, S. S. Babu, J. M. Vitek, S. A. David, J. W. Park, G. E. Ice, and R. I. Barabash

J. Appl. Phys. 96, 3673 (2004); http://dx.doi.org/10.1063/1.1777393 (7 pages) | Cited 4 times

Online Publication Date: 23 September 2004

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Using polychromatic microbeam synchrotron diffraction together with electron and optical microscopy, we studied dislocation structure changes of Ni—based single crystal superalloy during impulse heating up to the melting temperature. It is shown that the distribution of the thermal gradient is not monotonic. The maximum value of the thermal gradient is observed in the heat affected zone near the fusion line. Depending on the temperature, the formation of dislocation is accompanied by the partial or complete dissolution of γ′ particles in the matrix. Dislocations form and multiply due to thermal gradients, and their arrangement correlates with temperature gradient field and with the dissolution and reprecipitation of γ′ particles.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
64.75.-g Phase equilibria

An analytical density of states and joint density of states analysis of amorphous semiconductors

Stephen Karrer O’Leary

J. Appl. Phys. 96, 3680 (2004); http://dx.doi.org/10.1063/1.1778478 (7 pages) | Cited 9 times

Online Publication Date: 23 September 2004

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We study the relationship between the density of states and joint density of states functions in amorphous semiconductors. Introducing an elementary empirical model for the density of states functions that captures the basic expected features, we determine analytical and asymptotic joint density of states results, relating the parameters characterizing the underlying density of states functions with the resultant joint density of states. Numerical joint density of states results, corresponding to the specific case of hydrogenated amorphous silicon, are also presented. It is suggested that this density of states and joint density of states analysis will prove of use to the experimentalist.
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71.23.Cq Amorphous semiconductors, metallic glasses, glasses
71.20.Mq Elemental semiconductors

Onset of implant-related recombination in self-ion implanted and annealed crystalline silicon

Daniel Macdonald, Prakash N. K. Deenapanray, and Stephan Diez

J. Appl. Phys. 96, 3687 (2004); http://dx.doi.org/10.1063/1.1789630 (5 pages) | Cited 13 times

Online Publication Date: 23 September 2004

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The impact of residual recombination centers after low-energy self-implantation of crystalline silicon wafers and annealing at 900 °C has been determined by bulk carrier lifetime measurements as a function of implant dose. Doses below 1013 cm−2 resulted in no measurable increase in recombination, while higher doses caused a linear increase in the recombination center density. This threshold value corresponds to the known critical dose required for the formation of relatively stable dislocation loops during high temperature annealing. Deep level transient spectroscopy revealed a decrease in the vacancy-related defect concentration in the high-dose samples, which we interpret as reflecting an increase in the silicon interstitial concentration. This suggests that silicon interstitials, arising from the slowly dissolving dislocation loops, may be responsible for the increased recombination deep within the samples.
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61.72.uf Ge and Si
71.55.Cn Elemental semiconductors
61.72.J- Point defects and defect clusters
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Evaluation of back-side secondary ion mass spectrometry for boron diffusion in silicon and silicon-on-insulator substrates

K. L. Yeo, A. T. S. Wee, and Y. F. Chong

J. Appl. Phys. 96, 3692 (2004); http://dx.doi.org/10.1063/1.1782959 (4 pages) | Cited 5 times

Online Publication Date: 23 September 2004

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We present a study on the redistribution of boron in (100) crystalline silicon and silicon-on-insulator (SOI) substrates after rapid thermal processing (RTP). The use of SOI back-side secondary ion mass spectrometry (SIMS) technique in obtaining an accurate diffusion profile is also investigated. Our results show that the boron diffusion profiles (using conventional frontside SIMS) do not deviate in any of the two types of substrates after RTP with a soak time of 30 sec, indicating that the insulating effect of SOI substrate does not enhance the diffusion of boron. Since the profile obtained by the back-side SIMS technique is always shallower than that of front-side SIMS, it is deduced that the back-side SIMS technique gives a better representation of the real profile.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
61.72.uf Ge and Si
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing

Elastic constants of lotus-type porous magnesium: Comparison with effective-mean-field theory

Masakazu Tane, Tetsu Ichitsubo, Masahiko Hirao, Teruyuki Ikeda, and Hideo Nakajima

J. Appl. Phys. 96, 3696 (2004); http://dx.doi.org/10.1063/1.1776316 (6 pages) | Cited 6 times

Online Publication Date: 23 September 2004

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Lotus-type porous (LTP) metals possess a markedly anisotropic porous structure, in which long straight pores are homogeneously aligned unidirectionally. In this paper, we first describe a procedure for the determination of reliable elastic constants of LTP metals with high porosity, and next apply the technique to LTP magnesium, and finally compare the measurement results with those from the effective-mean-field (EMF) theory that has been recently proposed by Tane and Ichitsubo [Appl. Phys. Lett. 85, 197 (2004)]. Young’s modulus in the direction parallel to the longitudinal axis of pores decreases virtually linearly with porosity p, i.e., E∥≈45.3(1−p)1.33, whereas the normal Young’s modulus E⊥, falls rapidly, i.e., E⊥≈45.3(1−p)2.64. The Mori-Tanaka mean-field theory yields values that are close to the measured elastic constants in a wide porosity range, but cannot explain this power-law behavior. In contrast, the EMF theory gives more accurate values in the high-porosity range, and can reproduce the power-law behavior.
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62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Interdiffusion of Indium in piezoelectric InGaAs∕GaAs quantum wells grown by molecular beam epitaxy on (11n) substrates

C. M. Yee-Rendón, A. Pérez-Centeno, M. Meléndez-Lira, G. González de la Cruz, M. López-López, Kazuo Furuya, and Pablo O. Vaccaro

J. Appl. Phys. 96, 3702 (2004); http://dx.doi.org/10.1063/1.1783611 (7 pages) | Cited 4 times

Online Publication Date: 23 September 2004

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Pseudomorphic In0.2Ga0.8As∕GaAs quantum wells (QWs) were grown by molecular beam epitaxy on GaAs substrates oriented along (11n) directions, with n=1,2,3,4. The optical and structural properties of the heterostructures were studied by photoluminescence (PL), photoreflectance (PR) spectroscopy, and atomic force microscopy measurements. The energy transitions in the QWs have two contributions, a blueshift due to the compressive strain, and a redshift due to the quantum confined Stark effect produced by the piezoelectric field present in the QWs. A variational approach was employed to calculate the QWs ground energy transitions employing an ideal potential well with sharp interfaces. The theoretical energy transitions were fitted to the PL peaks energy to obtain the electric fields in the InGaAs QWs. The obtained electric fields show discrepancies with theoretical piezoelectric fields calculated from the strain present in the QWs. In order to overcome these discrepancies, we propose to include interdiffusion effects of In at the well interfaces. The matrix transfer method was implemented to numerically solve the Schrödinger equation taking into account In interdiffusion effects by including an asymmetric potential well with a profile depending on the details of the In incorporation. With interdiffusion effects included in the energy level calculations, and assuming the expected piezoelectric fields, the theoretical results reproduce very well the experimental values of PL and PR.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
77.65.Ly Strain-induced piezoelectric fields
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.07.St Quantum wells
78.67.De Quantum wells
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.37.Ps Atomic force microscopy (AFM)
68.60.Bs Mechanical and acoustical properties
78.20.Jq Electro-optical effects
71.20.Nr Semiconductor compounds

Polytype transition of N-face GaN:Mg from wurtzite to zinc-blende

E. Monroy, M. Hermann, E. Sarigiannidou, T. Andreev, P. Holliger, S. Monnoye, H. Mank, B. Daudin, and M. Eickhoff

J. Appl. Phys. 96, 3709 (2004); http://dx.doi.org/10.1063/1.1787142 (7 pages) | Cited 9 times

Online Publication Date: 23 September 2004

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We have investigated the polytype conversion of a GaN film from N-face wurtzite (2H�) to zinc-blende (3C�) structure due to Mg doping during growth by plasma-assisted molecular-beam epitaxy. Structural analysis by high-resolution transmission electron microscopy and high-resolution x-ray diffraction measurement revealed alignment of the cubic phase with the [111] axis perpendicular to the substrate surface. The optical characteristics of GaN:Mg layers are shown to be very sensitive to the presence of the cubic polytype. For low Mg doping, photoluminescence is dominated by a phonon-replicated donor-acceptor pair at ∼3.25 eV, related to the shallow Mg acceptor level, accompanied by a narrow excitonic emission. For high Mg doping, the photoluminescence spectra are also dominated by a line around 3.25 eV, but this emission displays the behavior of excitonic luminescence from cubic GaN. A cubic-related donor-acceptor transition at ∼3.16 eV is also observed, together with a broad blue band around 2.9 eV, previously reported in heavily Mg-doped 3C-GaN(001).
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81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
64.70.K- Solid-solid transitions
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Dq Plasma-based ion implantation and deposition
61.72.uf Ge and Si
61.72.up Other materials
71.55.Eq III-V semiconductors
71.35.-y Excitons and related phenomena

In-plane refractive-index anisotropy in porous silicon layers induced by polarized illumination during electrochemical etching

Hideki Koyama

J. Appl. Phys. 96, 3716 (2004); http://dx.doi.org/10.1063/1.1784613 (5 pages) | Cited 3 times

Online Publication Date: 23 September 2004

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Porous silicon (PSi) layers have been anodically etched under polarized illumination, and the degree of linear polarization of their photoluminescence (PL) was measured. The etching conditions were chosen such that the resulting PSi layers were thin enough for interference fringes to appear in their PL spectra. Experimental results show a sinusoidal variation in the degree of linear polarization as a function of the emission photon energy. The amplitude and phase of the sinusoidal variation depend largely on the polarization direction of the excitation light. These observations give strong evidence that there is a significant in-plane anisotropy of the refractive indices for these PSi samples. Values ranging from 0.1% to 0.67% have been obtained for the magnitude of the birefringence. The maximum refractive index is obtained when the excitation-light polarization direction is perpendicular to that of the polarized illumination used during etching. This can be explained by assuming that the polarized photoelectrochemical etching causes the Si structures to be thinner in the polarization direction.
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78.66.Db Elemental semiconductors and insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Ap Elemental semiconductors
81.65.Cf Surface cleaning, etching, patterning

Fluorine-enhanced boron diffusion induced by fluorine postimplantation in silicon

Taiji Noda

J. Appl. Phys. 96, 3721 (2004); http://dx.doi.org/10.1063/1.1784618 (6 pages) | Cited 2 times

Online Publication Date: 23 September 2004

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In this article, the postimplanted fluorine effect on boron transient-enhanced diffusion (TED) and dose loss during a 750°C annealing is shown. 19F implants at 2 keV, after 11B implant at an energy of 1 keV,3×1014∕cm2, have been investigated in the dose range between 1×1013∕cm2 and 6×1014∕cm2 without a preamorphizing implant. Below a F-implant dose of 1×1014∕cm2, the reduction or non-enhancement of boron-TED effect is observed. In the case of a F-implant dose of 6×1014∕cm2, the enhanced boron TED (∼2.6×) in crystalline Si and the increased dose loss(∼2×) than that of a normal boron TED is shown, and this anomalous diffusivity enhancement persists for 120 min at 750°C. The B+F 6×1014∕cm2 consecutive implant damage is smaller than that of the BF2 5 keV implant. In the case of the B+F 6×1014∕cm2, a high content of fluorine is retained around the end-of-range (EOR) damage region within 120 min. These results indicate that the fluorine retained around the EOR region may affect the enhanced boron TED in crystalline Si at 750°C. Boron-diffusion model, which describes both the native interstitial fluorine and the boron-fluorine chemical effect, explains that the suppression of boron TED with a low F-implant dose is due to the reduction of the interstitial supersaturation.
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61.72.uf Ge and Si
61.72.J- Point defects and defect clusters
66.30.Lw Diffusion of other defects
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Lateral stress measurements and shear strength in shock loaded tungsten carbide

J. C. F. Millett, N. K. Bourne, and D. P. Dandekar

J. Appl. Phys. 96, 3727 (2004); http://dx.doi.org/10.1063/1.1787617 (6 pages) | Cited 5 times

Online Publication Date: 23 September 2004

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The shear strength of a monolithic tungsten carbide has been measured as a function of impact stress. Results show that it increases with stress, in agreement with the work of others. Interestingly, it has also been shown that lateral stress increases, and thus shear strength decreases behind the shock front. Potential mechanisms are discussed, including cracking within the shock front itself, and stress relaxation due to high velocity dislocation motion within the shock front, followed by dislocation multiplication behind it.
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62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.M- Structural failure of materials

Surface-emitting stimulated emission in high-quality ZnO thin films

X. Q. Zhang, Ikuo Suemune, H. Kumano, J. Wang, and S. H. Huang

J. Appl. Phys. 96, 3733 (2004); http://dx.doi.org/10.1063/1.1778216 (4 pages) | Cited 18 times

Online Publication Date: 23 September 2004

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High-quality ZnO thin films were grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates. Three excitonic transitions associated with the valence bands A, B, and C were clearly revealed in the reflectance spectrum measured at 33 K. This result indicates that the ZnO thin films have the wurtzite crystalline structure. The emission spectra were measured with backscattering geometry at room temperature. When the excitation exceeded a certain value, linewidth narrowing, nonlinear rise of emission intensity, and the shortening of the carrier lifetime were clearly observed and these demonstrate the onset of stimulated emission. Together with the ZnO thickness dependence, we conclude that the observation of a stimulated emission in a direction perpendicular to the film surface is predominantly due to scattering of the in-plane stimulated emission by slightly remaining surface undulations in the ZnO films.
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78.66.Hf II-VI semiconductors
71.20.Nr Semiconductor compounds
78.45.+h Stimulated emission
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
81.05.Dz II-VI semiconductors
68.55.A- Nucleation and growth
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
52.77.Dq Plasma-based ion implantation and deposition

Photoluminescence of silver in glassy matrices

M. A. García, M. García-Heras, E. Cano, J. M. Bastidas, M. A. Villegas, E. Montero, J. Llopis, C. Sada, G. De Marchi, G. Battaglin, and P. Mazzoldi

J. Appl. Phys. 96, 3737 (2004); http://dx.doi.org/10.1063/1.1778473 (5 pages) | Cited 16 times

Online Publication Date: 23 September 2004

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This work studies the behavior of Ag+ ions incorporated in different silica-based glassy matrices. To this end, Ag-doped silica coatings, prepared via sol-gel and deposited on pure silica and soda-lime glasses, are investigated by means of structural and optical spectroscopy techniques. Silver tends to segregate towards the interface during the annealing process, but in the case of soda-lime glassy substrates the exchange process favors its diffusion into the substrate. The environment of Ag+ ions during the annealing process determines their final oxidation state. In the pure silica matrix, Ag+ ions are found to be unstable and tend to reduce to Ag0, with the subsequent formation of metallic nanoparticles. However, the presence of network formers and modifiers gives rise to the appearance of nonbridging oxygen, which allows the stabilization of Ag+ ions in the matrix.
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81.07.Wx Nanopowders
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Hx Other solid inorganic materials
61.46.-w Structure of nanoscale materials
61.43.Fs Glasses
81.40.Gh Other heat and thermomechanical treatments
81.65.Mq Oxidation
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.35.Dv Composition, segregation; defects and impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Homoepitaxial diamond growth for the control of surface conductive carrier transport properties

Oliver A Williams and Richard B Jackman

J. Appl. Phys. 96, 3742 (2004); http://dx.doi.org/10.1063/1.1789275 (6 pages) | Cited 4 times

Online Publication Date: 23 September 2004

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Growth of high quality diamond for surface conductive device applications is demonstrated. Mobility values higher than 140 cm2 V−1 s−1 at sheet carrier concentrations of 2.5×1012 cm−2 were achieved using a high growth rate process. Furthermore, control over the carrier transport statistics is demonstrated on both single crystal and polycrystalline diamond. This process allows the production of high quality electronic grade diamond with ability to tune carrier transport statistics. The mechanism behind this process is discussed.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Cw Elemental semiconductors
81.05.Cy Elemental semiconductors
73.25.+i Surface conductivity and carrier phenomena
72.20.Fr Low-field transport and mobility; piezoresistance
73.50.Dn Low-field transport and mobility; piezoresistance
68.55.A- Nucleation and growth
52.77.Dq Plasma-based ion implantation and deposition
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

High-pressure Raman spectroscopy of diamond anvils to 250 GPa:  Method for pressure determination in the multimegabar pressure range

Yuichi Akahama and Haruki Kawamura

J. Appl. Phys. 96, 3748 (2004); http://dx.doi.org/10.1063/1.1778482 (4 pages) | Cited 57 times

Online Publication Date: 23 September 2004

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The first-order Raman spectra of diamond anvils used in a gasketed high-pressure cell have been measured at pressure up to 250 GPa. The high-frequency edge of the Raman band, which corresponds to the Raman shift of the culet face, is represented by a function of pressure in the sample chamber up to 250 GPa. The dependence is almost independent on loading conditions. The application of the pressure dependence for pressure determination up to the multimegabars pressure region is proposed.
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07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
78.30.Na Fullerenes and related materials
62.50.-p High-pressure effects in solids and liquids
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

The influence of surface segregation on the optical properties of quantum wells

G. Gonzalez de la Cruz

J. Appl. Phys. 96, 3752 (2004); http://dx.doi.org/10.1063/1.1789628 (4 pages) | Cited 7 times

Online Publication Date: 23 September 2004

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Segregation of column III atoms during molecular beam epitaxy of III-V semiconductor compounds result in nonabrupt interfaces and surface compositions different from the bulk. This effect modifies the electronic states in the quantum well and the emission energy in the photoluminescence spectrum. In this work, we have solved analytically the Schrödinger equation taking into account the shape changes in the quantum well due to the segregation of atoms during the growth process of the semiconductor heterostructures. We apply this model to the case of indium segregation in the InGaAs/GaAs system. The transition energy calculations between the confined electron and hole states as function of the well width for different In composition and growth temperature are in agreement with the measured photoluminescence energy peaks.
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81.07.St Quantum wells
81.05.Ea III-V semiconductors
73.21.Fg Quantum wells
78.67.De Quantum wells
68.47.Fg Semiconductor surfaces
68.35.Dv Composition, segregation; defects and impurities
78.55.Cr III-V semiconductors

Photothermal Radiometry with Solid Cylindrical Samples

Chinhua Wang, Andreas Mandelis, and Yue Liu

J. Appl. Phys. 96, 3756 (2004); http://dx.doi.org/10.1063/1.1779973 (7 pages) | Cited 25 times

Online Publication Date: 23 September 2004

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We extend the applications of the photothermal diagnostics by means of laser-infrared photothermal radiometry (PTR) to samples with curved surfaces. Specifically, we present both the theoretical and experimental PTR studies on solid cylindrical samples (surfaces). Based on the Green function method, the thermal-wave field distribution of a cylindrical surface that is under the excitation of a periodically modulated uniform beam is obtained. The laser beam, which is of a cylindrical symmetry, impinges uniformly, partially or fully, on the cylindrical surface, which is practically infinitely long along the axial direction. The characteristics of the thermal-wave field with respect to the thermal diffusivity of the material, the diameter of the sample, the size of the incident beam, and the measurement of the angle are discussed. Experimental results are in good agreement with the theory.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.60.Dq Photometers, radiometers, and colorimeters
02.30.-f Function theory, analysis

Characteristics of dislocations in ZnO layers grown by plasma-assisted molecular beam epitaxy under different Zn∕O flux ratios

Agus Setiawan, Zahra Vashaei, Meoung Whan Cho, Takafumi Yao, Hiroyuki Kato, Michihiro Sano, Kazuhiro Miyamoto, I. Yonenaga, and Hang Ju Ko

J. Appl. Phys. 96, 3763 (2004); http://dx.doi.org/10.1063/1.1785852 (6 pages) | Cited 28 times

Online Publication Date: 23 September 2004

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We have investigated the characteristic of the dislocations in the ZnO layers grown on c sapphire by the plasma-assisted molecular beam epitaxy under the different Zn∕O flux ratios. The ZnO layers were characterized by the transmission electron microscopy (TEM) and the high-resolution x-ray diffraction (HRXRD). The TEM and HRXRD experiments revealed that the major threading dislocations (TDs) in the ZnO layers are the edge dislocations running along the c axis with Burgers vector of 1∕3〈11–20〉. The TD densities are determined to be 6.9×109, 2.8×109, and 2.7×109 cm−2, for O-rich, stoichiometric, and Zn-rich grown ZnO, respectively. Different from the O-rich grown ZnO where the dislocations run along the c-axis, several dislocations in the stoichiometric and the Zn-rich grown ZnO are inclined to 20°∼30° from the c-axis. By considering the slip system in the wurtzite-structure ZnO, the glide planes of the dislocations are close to (10-10) for the O-rich grown ZnO and close to (10-11) for the stoichiometric and Zn-rich grown ZnO. Furthermore, the thickness of the interface dislocations in the O-rich grown ZnO is much thinner than in the stoichiometric and Zn-rich grown ZnO. In addition, the most probable origin of the inclined dislocations including c∕a ratios, growth rate, and initial growth stage of high temperature (HT)-ZnO layers are also discussed.
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81.05.Dz II-VI semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.66.Bi Elemental solids
61.66.Dk Alloys
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Damage and recovery in arsenic doped silicon after high energy Si+ implantation

S. Solmi, M. Ferri, D. Nobili, and M. Bianconi

J. Appl. Phys. 96, 3769 (2004); http://dx.doi.org/10.1063/1.1787140 (6 pages) | Cited 3 times

Online Publication Date: 23 September 2004

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Electrical measurements were used to study the irradiation effects and the annealing behavior of heavily As doped silicon on insulator samples implanted with 2 MeV Si+ ions. It is found that implantation induces a strong reduction of the carrier density, which markedly depends on the concentration of As. Annealing at temperatures in the range 600–800 °C, by rapid thermal treatments or heating in furnace, showed that recovery takes place in two stages. The kinetics of the former, which should involve point defect-dopant complexes or small defect clusters, is rapid, while more stable defects demanding prolonged heating recover in the latter stage. It is concluded that these more stable defects should originate by the aggregation with an Ostwald ripening mechanism of the dopant-defect complexes and small point defect clusters, a phenomenon which competes with their annihilation. These processes, which ultimately determine the carrier density trapped in the stable defects, can also partially take place under the Si+ implantation. The effects of irradiation dose, temperature of the samples in the course of the irradiation, dopant concentration, and annealing temperature on defect structure and carrier concentration are reported and discussed.
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61.72.uj III-V and II-VI semiconductors
61.72.up Other materials
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
61.72.S- Impurities in crystals
61.72.J- Point defects and defect clusters
61.72.Yx Interaction between different crystal defects; gettering effect
73.61.-r Electrical properties of specific thin films

Determination of absolute bond strength from hydroxyl groups at oxidized aluminum-epoxy interfaces by angle beam ultrasonic spectroscopy

John H. Cantrell

J. Appl. Phys. 96, 3775 (2004); http://dx.doi.org/10.1063/1.1787144 (7 pages) | Cited 5 times

Online Publication Date: 23 September 2004

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The hydrogen bonding (H-bond) contribution to the adhesive strength of oxidized aluminum-epoxy interfaces is calculated from the Morse potential for the interaction of hydroxyl groups formed on the Al2O3 surface with epoxy receptors. A strength parameter called the normal spring constant flux KN is defined and calculated to be 3.8×1017 N m−3, corresponding to a tensile strength of 26 MPa, for values of the H-bond parameters and bond densities typical of moderate strength epoxies. The KN value is in very good agreement with values determined experimentally from an inversion of ultrasonic spectral data [A. I. Laverntyev and S. I. Rokhlin, J. Appl. Phys. 76, 4643 (1994); J. Acoust. Soc. Am. 102, 3467 (1997)]. It is also in agreement with the value KN=3.6×1017 N m−3 obtained by a reinterpretation of the periodic crack model [F. J. Margetan et al., J. Nondestr. Eval. 7, 131 (1988)] when applied to adhesive interfaces. The agreement between theory and experiment establishes KN as a quantitative nondestructive measure of adhesive strength. The relationship between the normal and transverse (shear) spring constant fluxes is derived and the effects of thermal fluctuations are addressed.
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81.70.Cv Nondestructive testing: ultrasonic testing, photoacoustic testing
68.35.Np Adhesion
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
82.30.Rs Hydrogen bonding, hydrophilic effects
62.20.F- Deformation and plasticity
62.20.M- Structural failure of materials
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