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21 May 2001

Volume 78, Issue 21, pp. 3163-3363

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Nanometer-scale measurements of photoabsorption spectra of individual defects in semiconductors

Akira Hida, Yutaka Mera, and Koji Maeda

Appl. Phys. Lett. 78, 3190 (2001); http://dx.doi.org/10.1063/1.1371960 (3 pages) | Cited 8 times

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Photoabsorption measurements using scanning tunneling microscopy, in which a modulated component of the tunneling current induced by a wavelength-variable chopped light is detected, were conducted for a cleaved surface of GaAs to demonstrate that a simple scheme enables nanometer-scale imaging of individual subsurface defects isolated in the crystal with fingerprints of photoabsorption spectra associated with them. The origin of the signal modulation and the image contrast formation mechanism are discussed in terms of photothermal expansion caused by nonradiative recombinations at the defect, photoinduced defect transformation, and an electrostatic surface potential change due to a charge alteration of the defect. © 2001 American Institute of Physics.
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78.40.Ha Other nonmetallic inorganics
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.-y Defects and impurities in crystals; microstructure

Raman scattering test of single-wall carbon nanotube composites

V. G. Hadjiev, M. N. Iliev, S. Arepalli, P. Nikolaev, and B. S. Files

Appl. Phys. Lett. 78, 3193 (2001); http://dx.doi.org/10.1063/1.1373405 (3 pages) | Cited 60 times

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Raman spectroscopy is used to infer elastic properties of single-wall carbon nanotubes (SWNTs) in composites. This letter presents strain-induced frequency shift of tangential Raman active modes of SWNTs embedded in epoxy resin subjected to bending. Epoxy curing and sample extension in the tensile strength test are found to create residual strains on the SWNT ropes. We demonstrate that specimen compression in combination with the Raman microprobe technique provides a means for determining of these strains and hence load transfer effectiveness. © 2001 American Institute of Physics.
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62.25.-g Mechanical properties of nanoscale systems
81.70.Fy Nondestructive testing: optical methods
81.05.Qk Reinforced polymers and polymer-based composites
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
78.30.-j Infrared and Raman spectra
78.67.Ch Nanotubes
81.07.De Nanotubes
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Index and density changes induced by proton radiation in lanthanum crown glass

A. Gusarov, D. Doyle, A. Hermanne, and F. Berghmans

Appl. Phys. Lett. 78, 3196 (2001); http://dx.doi.org/10.1063/1.1373411 (3 pages) | Cited 1 time

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We studied the refractive index and density changes in cerium-doped lanthanum crown glass irradiated in air with 38.5 MeV protons. At a low proton fluence, the index change is linear with dose, and reaches 2.4×10−5 at 2.7×1012 p/cm2 (0.65 Mrad dose). The rate of index change decreases with the proton fluence, but at high total dose (1014 p/cm2) radiation-induced surface dilatation and birefringence start to appear. Our results show that the present concept of radiation-hard optical glass should be revised and that a high dose of proton radiation can produce index changes sufficient for the fabrication of integrated optical devices. © 2001 American Institute of Physics.
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42.70.Ce Glasses, quartz
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.80.Jh Ion radiation effects
61.82.Ms Insulators
78.20.Fm Birefringence
81.40.Wx Radiation treatment (particle and electromagnetic)
61.43.Fs Glasses

Enhanced band-gap blueshift due to group V intermixing in InGaAsP multiple quantum well laser structures induced by low temperature grown InP

A. S. W. Lee, M. MacKenzie, D. A. Thompson, J. Bursik, B. J. Robinson, and G. C. Weatherly

Appl. Phys. Lett. 78, 3199 (2001); http://dx.doi.org/10.1063/1.1374231 (3 pages) | Cited 16 times

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Photoluminescence and cross-sectional transmission electron microscopy, combined with x-ray compositional analysis, have been used to study quantum well intermixing in an InGaAsP quantum well laser structure. Quantum well intermixing is induced by capping the samples with a layer of InP grown at low temperature (300 °C) and subjecting them to rapid thermal anneal treatments in the temperature range 600–800 °C. The presence of the low temperature InP layer, which contains an abundance of nonequilibrium point defects, significantly enhances the intermixing on annealing, producing a large band-gap blueshift. The microscopy results show good broadening with smeared interfaces, and the compositional analysis suggests this can be attributed to the intermixing of group V atoms. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
68.65.Fg Quantum wells
73.21.Fg Quantum wells
78.67.De Quantum wells
78.55.Cr III-V semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Catalytic synthesis and photoluminescence of β-Ga2O3 nanowires

C. H. Liang, G. W. Meng, G. Z. Wang, Y. W. Wang, L. D. Zhang, and S. Y. Zhang

Appl. Phys. Lett. 78, 3202 (2001); http://dx.doi.org/10.1063/1.1374498 (3 pages) | Cited 107 times

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Monoclinic gallium oxide (β-Ga2O3) nanowires were synthesized by heat treating a composite material of GaAs and pre-evaporated Au at 1240 °C in dry oxygen atmosphere. The catalytic Au metal generated liquid nanoclusters that serve as reactive sites confining and directing the growth of β-Ga2O3 nanowires during the vapor-liquid-solid growth process. The β-Ga2O3 nanowires have diameters ranging from 20 to 50 nm and lengths of several micrometers. Photoluminescence measurement under excitation at 250 nm shows that the bulk β-Ga2O3 nanowires have a stable blue emission at 475 nm and an ultraviolet emission at 330 nm, which may be related to the defects such as the oxygen vacancy and the gallium–oxygen vacancy pair. © 2001 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Stress engineering during metalorganic chemical vapor deposition of AlGaN/GaN distributed Bragg reflectors

K. E. Waldrip, J. Han, J. J. Figiel, H. Zhou, E. Makarona, and A. V. Nurmikko

Appl. Phys. Lett. 78, 3205 (2001); http://dx.doi.org/10.1063/1.1371240 (3 pages) | Cited 58 times

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In situ stress monitoring has been employed during metalorganic chemical vapor deposition of AlGaN/GaN distributed Bragg reflectors (DBRs). It was found that the insertion of multiple AlN interlayers is effective in converting the tensile growth stress typically observed in this system into compression, thus alleviating the problem of crack generation. Crack-free growth of a 60 pair Al0.20Ga0.80N/GaN quarter-wavelength DBR was obtained over the entire 2 in. wafer; an accompanying reflectivity of at least 99% was observed near the peak wavelength around 380 nm. © 2001 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.60.Bs Mechanical and acoustical properties
42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes

Melting of indium at high pressure determined by monochromatic x-ray diffraction in an externally-heated diamond anvil cell

Guoyin Shen, Nagayoshi Sata, Mark L. Rivers, and Stephen R. Sutton

Appl. Phys. Lett. 78, 3208 (2001); http://dx.doi.org/10.1063/1.1374497 (3 pages) | Cited 6 times

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The melting behavior of indium at high pressure has been studied in an externally heated diamond anvil cell (DAC) using x-ray diffraction measurements. Melting at high pressure was identified by the appearance of diffuse scattering from the melt with the simultaneous disappearance of crystalline diffraction signals. The observed melting curve is in good agreement with previous determinations based on resistivity measurements in a piston cylinder apparatus. These results demonstrate the successful melting experiments in a DAC using the x-ray diffuse scattering as the melting criterion. © 2001 American Institute of Physics.
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64.70.D- Solid-liquid transitions
62.50.-p High-pressure effects in solids and liquids
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
61.05.cf X-ray scattering (including small-angle scattering)

Influence of electronic temperature and distribution on the second-order surface nonlinear susceptibility of metals

Chunlei Guo, George Rodriguez, Mark Hoffbauer, and Antoinette J. Taylor

Appl. Phys. Lett. 78, 3211 (2001); http://dx.doi.org/10.1063/1.1374517 (3 pages) | Cited 3 times

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We performed ultrafast, optical pump and second-harmonic-generation (SHG) probe measurements to study the effects of electronic temperature (Te) and distribution on the second-order nonlinear susceptibility [χ(2)] for a gold surface. These measurements clarify the physical origin of the recently observed power-law deviation of the SHG signal at high illuminating intensities. The study of SHG is extended to the high Te regime, and the results agree with a model calculation presented in this letter. The consistency between the experimental and theoretical results in this letter provides a uniform picture of the effects of the electronic temperature and distribution on χ(2). © 2001 American Institute of Physics.
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42.65.An Optical susceptibility, hyperpolarizability
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.68.+m Optical properties of surfaces
78.66.Bz Metals and metallic alloys
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.47.-p Spectroscopy of solid state dynamics

Staircase-like spectral dependence of ground-state luminescence time constants in high-density InAs/GaAs quantum dots

Yu. I. Mazur, J. W. Tomm, V. Petrov, G. G. Tarasov, H. Kissel, C. Walther, Z. Ya. Zhuchenko, and W. T. Masselink

Appl. Phys. Lett. 78, 3214 (2001); http://dx.doi.org/10.1063/1.1371965 (3 pages) | Cited 23 times

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Time-resolved photoluminescence (PL) from InAs/GaAs quantum dots with a bimodal size distribution is used to investigate the dynamic carrier-transfer processes which couple transfer between similarly sized quantum dots and between quantum dots in different size categories. The relationship between the decay time and the emission energy appears staircaselike and the energetic positions of the steps as well as the shape can be correlated to the shape of the steady-state PL emission through a rate-equation theory. These results show how transient PL can be used to investigate the dynamics of carrier transfer in quantum-dot systems. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.21.La Quantum dots
78.67.Hc Quantum dots
81.07.Ta Quantum dots
78.47.-p Spectroscopy of solid state dynamics

Direct evidence for implanted Fe on substitutional Ga sites in GaN

U. Wahl, A. Vantomme, G. Langouche, J. G. Correia, and L. Peralta

Appl. Phys. Lett. 78, 3217 (2001); http://dx.doi.org/10.1063/1.1372201 (3 pages) | Cited 10 times

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The lattice location of iron in thin-film, single-crystalline hexagonal GaN was studied by means of the emission channeling technique. Following 60 keV room temperature implantation of the precursor isotope 59Mn at a dose of 1.0×1013 cm−2 and annealing up to 900 °C, the angular distribution of β− particles emitted by the radioactive isotope 59Fe was measured by a position-sensitive electron detector. The β− emission patterns around the [0001], [math102], [math101], and [math113] directions give direct evidence that the majority of Fe (80%) occupies substitutional Ga sites. © 2001 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.S- Impurities in crystals
71.55.Eq III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing

Multiwavelength thermal lens determination of fluorescence quantum efficiency of solids: Application to Nd3+-doped fluoride glass

S. M. Lima, A. A. Andrade, R. Lebullenger, A. C. Hernandes, T. Catunda, and M. L. Baesso

Appl. Phys. Lett. 78, 3220 (2001); http://dx.doi.org/10.1063/1.1375000 (3 pages) | Cited 31 times

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A multiwavelength thermal lens (TL) method was developed to determine the fluorescence quantum efficiency of solids. The experiments have been performed in Nd3+-doped fluoride glasses, using five different excitation wavelengths: 514, 576, 741, 796, and 867 nm. In this work, the absolute value of fluorescence quantum efficiency can be obtained by the linear dependence of the TL signal with the excitation wavelength. Our results suggest that the method can be applied to study a wide range of fluorescent materials, with a special ability to be used for measurements of highly transparent materials with very low TL effect. © 2001 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
42.70.Ce Glasses, quartz
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
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