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12 Jan 1998

Volume 72, Issue 2, pp. 135-266

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Lateral oxidation of InAlAs in InP-based heterostructures for long wavelength vertical cavity surface emitting laser applications

H. Gebretsadik, K. Kamath, W.-D. Zhou, P. Bhattacharya, C. Caneau, and R. Bhat

Appl. Phys. Lett. 72, 135 (1998); http://dx.doi.org/10.1063/1.121443 (3 pages) | Cited 18 times

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We have studied the wet thermal oxidation of In0.52Al0.48As and its potential application in current and optical confinement in vertical cavity surface emitting lasers (VCSELs). Two types of InP-based heterostructures were used to study the effect of adjacent layer compositions on the lateral oxidation behavior of the InAlAs. It was found that the oxidation of In0.52Al0.48As with InP adjacent layers, compared with In0.53Ga0.47As adjacent layers, proceeded faster, more uniformly and with minimal degradation of the surrounding layers making it ideal for optoelectronic applications. © 1998 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Ea III-V semiconductors
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

High-power near-resonant 1.55 μm emitting InGaAsP/InP antiguided diode laser arrays

A. Bhattacharya and D. Botez

Appl. Phys. Lett. 72, 138 (1998); http://dx.doi.org/10.1063/1.120667 (3 pages) | Cited 8 times

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We present high peak-pulsed coherent power results from large-aperture, 1.55 μm antiguided laser arrays. The InP-based devices have a compressively strained InGaAsP double-quantum-well active region and are fabricated by two-step self-aligned metalorganic chemical vapor deposition. We have obtained 2.5 W front-facet peak power in a 2.6° wide beam [6×diffraction limit (D.L.)], with 1.2 W in the central lobe, from 40-element, 250 μm aperture devices. The width of the central lobe remains constant from 4 to 15×threshold. Devices with improved temperature characteristics and of geometry closer to the resonance condition provide 1 W peak power in a beam 1.2° wide (2.7×D.L.), with 61% of the energy in the central lobe; and 1.75 W peak power in a 1.5° wide beam (3.5×D.L.) at heatsink temperatures between 15 and 45 °C. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Whispering-gallery-mode microring laser using a conjugated polymer

Y. Kawabe, Ch. Spiegelberg, A. Schülzgen, M. F. Nabor, B. Kippelen, E. A. Mash, P. M. Allemand, M. Kuwata-Gonokami, K. Takeda, and N. Peyghambarian

Appl. Phys. Lett. 72, 141 (1998); http://dx.doi.org/10.1063/1.120668 (3 pages) | Cited 39 times

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We observed laser emission in whispering gallery modes using a microring composed of a semiconducting polymer poly[2,5-bis-(2′-ethylhexyloxy)-p-phenylenevinylene coated on an etched fiber under transient and quasisteady-state pumping conditions. The threshold for laser oscillation was 1 mJ/cm2 (0.1 MW/cm2) and 30 μJ/cm2 (300 MW/cm2) for nanosecond and femtosecond excitation, respectively. The laser output showed superlinear dependence on the excitation energy above the threshold. The demonstration of lasing under quasisteady-state pumping shows the possibility to develop electrically pumped polymer lasers. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Wd Fiber lasers

Optically pumped blue organic semiconductor lasers

V. G. Kozlov, G. Parthasarathy, P. E. Burrows, S. R. Forrest, Y. You, and M. E. Thompson

Appl. Phys. Lett. 72, 144 (1998); http://dx.doi.org/10.1063/1.120669 (3 pages) | Cited 43 times

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Lasing at 460, 485, and 510 nm is demonstrated in optically pumped, vacuum-deposited amorphous thin films of a carbazole derivative doped with Coumarin 47, perylene, and Coumarin 30, respectively. Efficient, nonradiative Förster energy transfer between host and dopant organic molecules results in low lasing thresholds (5 μJ/cm2), high differential quantum efficiencies (15%), high peak output powers (20 W), and long operational lifetimes (>105 pulses at 100 times the threshold power). © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Noncollinearly phase-matched femtosecond optical parametric amplification with a 2000 cm−1 bandwidth

Akira Shirakawa and Takayoshi Kobayashi

Appl. Phys. Lett. 72, 147 (1998); http://dx.doi.org/10.1063/1.120670 (3 pages) | Cited 59 times

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An optical parametric amplifier generating as short as 14 fs pulses in a visible region has been constructed in a noncollinear phase-matching configuration. The group-velocity matching between the signal and idler enormously broadens the gain bandwidth up to 2000 cm−1, which is mainly limited by the chirp of the seed pulses. Pulses shorter than 20 fs are tunable from 550 to 690 nm by scanning the delay-line of the pump beam. © 1998 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc Modulation, tuning, and mode locking

Failure of phase-matching concept in large-signal parametric frequency conversion

S. Trillo, G. Millot, E. Seve, and S. Wabnitz

Appl. Phys. Lett. 72, 150 (1998); http://dx.doi.org/10.1063/1.120671 (3 pages) | Cited 3 times

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Four-wave mixing experiments in a low-birefringence optical fiber reveal an unexpected sudden increase of the conversion efficiency as the signal power crosses a threshold value. In this regime, peak frequency conversion is achieved outside the small-signal parametric gain spectrum. A nonlinear model of wave mixing fits the measured data well. © 1998 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.81.Gs Birefringence, polarization

Electro-optic modulation using an organic single crystal film in a Fabry–Perot cavity

Jianjun Xu, Ligui Zhou, and M. Thakur

Appl. Phys. Lett. 72, 153 (1998); http://dx.doi.org/10.1063/1.120672 (2 pages) | Cited 12 times

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Electro-optic modulation has been demonstrated using single crystal film of an organic electro-optic material, [N-(4-nitrophenyl)-L-prolinol] (NPP), placed in a Fabry–Perot cavity. The transverse geometry was used for electro-optic modulation. The cavity used had a finesse of about 50. The modulation depth achieved was about 0.7% for a low ac field of 0.5 V/μm applied along the charge-transfer (polar) axis on the film. The results are promising for applications of such films in high speed optical signal processing. © 1998 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
07.60.Ly Interferometers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Spectral characteristics of an InP/InGaAs distributed absorbing Bragg reflector

Kensuke Ogawa, Yasuhiro Matsui, Taro Itatani, and Kiyoshi Ouchi

Appl. Phys. Lett. 72, 155 (1998); http://dx.doi.org/10.1063/1.120673 (3 pages) | Cited 3 times

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An InP/In0.53Ga0.47As distributed absorbing Bragg reflector is investigated by reflectance and group-delay-time spectroscopy. The measured reflectance is suppressed and shows a minimum at the low-wavelength side of the high-reflectance band. This suppression of reflectance is due to an enhancement of optical absorption. The enhancement of optical absorption originates from an increase in the overlap of the optical field with the absorbing InGaAs layers since an intense optical field is confined near the surface in the spectral range of the enhancement. © 1998 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Fd III-V semiconductors
78.40.Fy Semiconductors
42.79.Fm Reflectors, beam splitters, and deflectors
78.20.-e Optical properties of bulk materials and thin films

Green phosphor for low-voltage cathodoluminescent applications: SrGa2S4:Eu2+

S. Yang, C. Stoffers, F. Zhang, S. M. Jacobsen, B. K. Wagner, C. J. Summers, and Neil Yocom

Appl. Phys. Lett. 72, 158 (1998); http://dx.doi.org/10.1063/1.120674 (3 pages) | Cited 49 times

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The optical and physical properties of a low-voltage phosphor, SrGa2S4:Eu2+, are reviewed. This phosphor has excellent chromaticity and high luminous efficiency at excitation voltages <3 kV and at high drive current ( ∼ 100 μA/cm2). At high current densities this phosphor was found to have superior saturation properties compared to current phosphors. This is attributed to the fast decay time of this phosphor, which is expected to enhance its resistance to saturation. Recent studies show that this phosphor has good maintenance properties. © 1998 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence

Photoinduced surface deposition of Ag on Ag-rich Ag–Ge–S films: Optimal Ag content and film thickness for applications in optical recording devices

Takeshi Kawaguchi

Appl. Phys. Lett. 72, 161 (1998); http://dx.doi.org/10.1063/1.120706 (3 pages) | Cited 3 times

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The photosensitivity of the photosurface deposition (PSD) effect and the durability in air of Agx(Ge0.3S0.7)100−x films (40 ⩽ x ⩽ 83) with thicknesses of 50–700 nm have been studied. Films of 60–65 at. % Ag and 200–300 nm thick were found to be optimal for applications in optical recording devices. Crystallized samples have been examined to obtain structural information on the Ag-rich films. It is suggested that excess Ag+ ions, which contribute to the PSD, exist in a disordered Ag8GeS6 phase of the Ag-rich films. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.43.Fs Glasses
42.79.Vb Optical storage systems, optical disks
42.79.Wc Optical coatings
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X-ray generation in cryogenic targets irradiated by 1 μm pulse laser

Atsushi Shimoura, Sho Amano, Shuji Miyamoto, and Takayasu Mochizuki

Appl. Phys. Lett. 72, 164 (1998); http://dx.doi.org/10.1063/1.120708 (3 pages) | Cited 20 times

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Soft x-ray spectral radiations from Xe, H2O, and CO2 cryogenic targets irradiated by a 1 μm neodymium doped YAG-slab laser at pulse widths of 12–20 ns and at laser intensities of 5×1010–1012 W/cm2 have been observed. These targets radiate soft x-rays in a wavelength range of 10–13 nm which is useful for projection microlithography. We have found a strong x-ray spectral peak at λ = 10.8 nm with a Xe cryogenic target. The measured x-ray conversion efficiency with the Xe target was 0.8%/sr(λ=10.8±0.27 nm) at a laser intensity of 1×1012 W/cm2. This was ten times or more efficient than that with H2O and CO2 targets. © 1998 American Institute of Physics.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
07.85.-m X- and γ-ray instruments
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Influence of ambient gas on the temperature and density of laser produced carbon plasma

S. S. Harilal, C. V. Bindhu, V. P. N. Nampoori, and C. P. G. Vallabhan

Appl. Phys. Lett. 72, 167 (1998); http://dx.doi.org/10.1063/1.120602 (3 pages) | Cited 11 times

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The effect of ambient gas on the dynamics of the plasma generated by laser ablation of a carbon target using 1.06 μm radiation from a Q-switched Nd:YAG laser has been investigated using a spectroscopic technique. The emission characteristics of the carbon plasma produced in argon, helium and air atmospheres are found to depend strongly on the nature and pressure of the surrounding gas. It has been observed that hotter and denser plasmas are formed in an argon atmosphere rather than in helium or air as an ambient. © 1998 American Institute of Physics.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
79.20.Ds Laser-beam impact phenomena
52.25.-b Plasma properties
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Growth of b-axis rare earths on sapphire by molecular beam epitaxy

K. A. Ritley and C. P. Flynn

Appl. Phys. Lett. 72, 170 (1998); http://dx.doi.org/10.1063/1.120675 (3 pages) | Cited 2 times

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A process is described whereby hcp rare-earth metals can be grown heteroepitaxially as high-quality single-crystal films with the b axis normal to the growth plane. The growth employs molecular beam epitaxy, starting from available sapphire substrates. The results of characterization by several techniques are described. © 1998 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology

Elastic behavior of nanoparticle chain aggregates

Sheldon K. Friedlander, Hee Dong Jang, and Kevin H. Ryu

Appl. Phys. Lett. 72, 173 (1998); http://dx.doi.org/10.1063/1.120676 (3 pages) | Cited 27 times

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Nanoparticle chain aggregates (NCA) possess elastomeric properties including stretch under tension, and contraction when the tension is relaxed. Individual chain aggregates of 7 nm titania particles a few hundred nm long were observed in the electron microscope. The NCA were stretched across expanding holes in the carbon film on an electron micrograph grid. After stretching up to 90%, the NCA broke loose at one end and contracted to a tightly folded chain. This pattern was observed in repeated tests. Mechanisms for this behavior and reasons for its generality are proposed. Implications are discussed for the ductility of nanoparticle ceramics, and the increased tensile strength and elastic modulus of rubber due to nanoparticle additives. © 1998 American Institute of Physics.
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62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Manipulation of passivated gold clusters on graphite with the scanning tunneling microscope

P. J. Durston, R. E. Palmer, and J. P. Wilcoxon

Appl. Phys. Lett. 72, 176 (1998); http://dx.doi.org/10.1063/1.120677 (3 pages) | Cited 20 times

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Chemically passivated gold nanoclusters deposited on the surface of graphite have been manipulated with the scanning tunneling microscope (STM) in ultrahigh vacuum. The controlled clearing of a definite shape in a cluster layer is demonstrated. Clusters embedded in a close-packed array could not be removed from the surface, apparently because of the attractive interaction between neighboring ligand chains. A minority channel of cluster fragmentation has been identified and leads to the creation of platelets which can be further manipulated by the STM tip. © 1998 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.65.Rv Passivation

Strain-induced island scaling during Si1−xGex heteroepitaxy

W. Dorsch, H. P. Strunk, H. Wawra, G. Wagner, J. Groenen, and R. Carles

Appl. Phys. Lett. 72, 179 (1998); http://dx.doi.org/10.1063/1.120622 (3 pages) | Cited 51 times

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We investigated the composition-dependent size of pseudomorphic Si1−xGex islands on Si(001). Si1−xGex layers with 0.05 ⩽ x ⩽ 0.54 were deposited from metallic solution. The island growth occurs near thermodynamic equilibrium and facilitates a comparison of the results with predictions based on energetics. We find pseudomorphic islands with base widths ranging from several μm to a few nm. We show that it is possible to adjust the island size by simply choosing the appropriate layer composition. Varying deposition temperatures and growth velocities do not affect the scaling behavior. © 1998 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Hd Other semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Internal distortion in ZrO2–CeO2 solid solutions: Neutron and high-resolution synchrotron x-ray diffraction study

Masatomo Yashima, Satoshi Sasaki, Yasuo Yamaguchi, Masato Kakihana, Masahiro Yoshimura, and Takeharu Mori

Appl. Phys. Lett. 72, 182 (1998); http://dx.doi.org/10.1063/1.120678 (3 pages) | Cited 42 times

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Neutron and high-resolution synchrotron x-ray diffraction measurements have indicated a tetragonal zirconia phase with both an axial ratio of unity and internal shear deformation: The oxygen displacements from ideal fluorite positions of 0.088 and 0.078 Å are observed for 65 and 70 mol % CeO2–ZrO2 samples, respectively, although both c/a values are 1.000±0.001. The c/a ratio decreases with increasing of CeO2 content and decreases discontinuously to unity around a 60 mol % CeO2 composition, while the oxygen displacement decreases continuously up to about 90 mol % CeO2. © 1998 American Institute of Physics.
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64.70.K- Solid-solid transitions
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Superior two-dimensional electron gas on (511)A GaAs

Hadas Shtrikman, A. Soibel, and U. Meirav

Appl. Phys. Lett. 72, 185 (1998); http://dx.doi.org/10.1063/1.120679 (3 pages) | Cited 1 time

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We present a comparative study of two-dimensional electron gas structures, which were grown on (511)A GaAs substrates and on conventional (100) GaAs substrates. The study included both normal interface and inverted interface structures. The (511)A presents consistently and substantially improved transport properties, whose origin can be traced to the growth dynamics of these surfaces. We conclude that (511)A GaAs promises to serve as an alternative and superior platform for realizing various n-type GaAs structures. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
72.80.Ey III-V and II-VI semiconductors

Stress-induced fragmentation of multiwall carbon nanotubes in a polymer matrix

H. D. Wagner, O. Lourie, Y. Feldman, and R. Tenne

Appl. Phys. Lett. 72, 188 (1998); http://dx.doi.org/10.1063/1.120680 (3 pages) | Cited 314 times

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We report the observation of single nanotube fragmentation, under tensile stresses, using nanotube-containing thin polymeric films. Similar fragmentation tests with single fibers instead of nanotubes are routinely performed to study the fiber-matrix stress transfer ability in fiber composite materials, and thus the efficiency and quality of composite interfaces. The multiwall nanotube-matrix stress transfer efficiency is estimated to be at least one order of magnitude larger than in conventional fiber-based composites. © 1998 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.05.Ni Dispersion-, fiber-, and platelet-reinforced metal-based composites
83.80.Ab Solids: e.g., composites, glasses, semicrystalline polymers

Six-fold coordinated silicon at grain boundaries in sintered α-Al2O3

Kenji Kaneko, Isao Tanaka, and Masato Yoshiya

Appl. Phys. Lett. 72, 191 (1998); http://dx.doi.org/10.1063/1.120681 (3 pages) | Cited 4 times

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High-resolution transmission electron microscopy (HRTEM) and analytical electron microscopy (AEM) have been carried out on Si-doped sintered α-Al2O3. HRTEM shows that there is no amorphous phase at grain boundaries. The Si-segregated boundary is found to be much more sensitive to irradiation damage than undoped Al2O3 grain boundaries. AEM with energy dispersive x-ray spectroscopy (EDS) shows the significant segregation of Si at grain boundaries, and AEM with electron energy-loss spectroscopy (EELS) reveals the existence of six-fold coordinated Si at the grain boundaries. The theoretical calculations obtained by the molecular orbital method support the data obtained by EELS. © 1998 American Institute of Physics.
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61.72.Mm Grain and twin boundaries
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
79.20.Kz Other electron-impact emission phenomena
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Defect annealing in a II–VI laser diode structure under intense optical excitation

C. Jordan, D. T. Fewer, J. F. Donegan, E. M. McCabe, A. Huynh, F. P. Logue, S. Taniguchi, T. Hino, K. Nakano, and A. Ishibashi

Appl. Phys. Lett. 72, 194 (1998); http://dx.doi.org/10.1063/1.120682 (3 pages) | Cited 4 times

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Defect annealing under intense pulsed optical excitation has been observed in a II–VI laser diode structure at room temperature. More than one order of magnitude increase in photoluminescence intensity has been obtained when the annealed area is probed at low excitation intensity. High-resolution confocal photoluminescence images of the annealed region do not show any sign of degradation. Together, these results suggest that an initial density of intrinsic point defects present within the active region can be removed by the optical annealing. Recombination-enhanced defect reactions in the vicinity of the point defects are responsible for this nonthermal annealing effect. © 1998 American Institute of Physics.
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81.05.Dz II-VI semiconductors
42.55.Px Semiconductor lasers; laser diodes
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Homoepitaxy of 6H and 4H SiC on nonplanar substrates

N. Nordell, S. Karlsson, and A. O. Konstantinov

Appl. Phys. Lett. 72, 197 (1998); http://dx.doi.org/10.1063/1.120683 (3 pages) | Cited 4 times

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Growth by vapor phase epitaxy around stripe mesas and in trenches formed by reactive ion etch on 6H and 4H SiC substrates has been investigated. The mesas were aligned with the low index 〈1120〉 and 〈1100〉 directions, as well as with the high index 〈1,1+√,math,0〉 directions, in order to reveal and study the growth habit. It was found that a low C:Si ratio gave a smooth growth and small differences in growth rate between lattice planes. A larger C:Si ratio gave more faceted growth, both limited by surface kinetics and surface diffusion, and the growth rate was 10% lower in the [1100] direction and 10% higher in the [1120] direction, than on the substrate. Growth on mesas oriented parallel to the substrate off-orientation shows clear step-flow growth, while growth on mesas oriented perpendicular to the off-orientation reveals the singular (0001) plane, where islands are observed, which might indicate Stranski–Krastanov growth. © 1998 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase

Carbon-induced undersaturation of silicon self-interstitials

R. Scholz, U. Gösele, J.-Y. Huh, and T. Y. Tan

Appl. Phys. Lett. 72, 200 (1998); http://dx.doi.org/10.1063/1.120684 (3 pages) | Cited 39 times

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Carbon diffusion into silicon is well behaved and does not generate any nonequilibrium point defects. We show that, in contrast, the diffusion of carbon incorporated in silicon well above its solid solubility will cause an undersaturation of silicon self-interstitials, which in turn may cause retarded diffusion of boron. In addition, we predict that due to this undersaturation, the diffusion of built-in carbon spikes will lead to strongly non-Gaussian concentration profiles. © 1998 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.J- Point defects and defect clusters
64.75.-g Phase equilibria

Low-noise YBa2Cu3O7−x single layer dc superconducting quantum interference device (SQUID) magnetometer based on bicrystal junctions with 30° misorientation angle

J. Beyer, D. Drung, F. Ludwig, T. Minotani, and K. Enpuku

Appl. Phys. Lett. 72, 203 (1998); http://dx.doi.org/10.1063/1.120685 (3 pages) | Cited 35 times

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We have fabricated and characterized a low-noise direct-coupled magnetometer based on a 100 pH YBa2Cu3O7−x dc superconducting quantum interference device (SQUID) on a 10 mm×10 mm SrTiO3 bicrystal substrate with 30° misorientation angle. The thin films were deposited by hollow cathode discharge sputtering and patterned using conventional photolithography and Ar ion beam etching. The SQUID magnetometer was operated using direct-coupled flux-locked-loop electronics with bias reversal. The sensor had a usable voltage swing of 39 μV and a white magnetic field noise of 32 fTHz−1/2 with a 1/f corner at 2 Hz, including electronics and environmental noise. The voltage versus flux (V−Φ) characteristic showed a pronounced distortion on the negative slope. Numerical simulations were performed to explain the distorted V−Φ characteristic. Measurements of magnetocardiograms demonstrate the suitability of this sensor for biomagnetic applications. © 1998 American Institute of Physics.
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07.55.Ge Magnetometers for magnetic field measurements
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.72.-h Cuprate superconductors
87.50.C- Static and low-frequency electric and magnetic fields effects
74.78.-w Superconducting films and low-dimensional structures
07.50.Hp Electrical noise and shielding equipment
81.15.Cd Deposition by sputtering
81.65.Cf Surface cleaning, etching, patterning
87.63.Hg Thermography

Channels of Cd diffusion and stoichiometry in CdTe grown by molecular beam epitaxy

A. Barcz, G. Karczewski, T. Wojtowicz, M. Sadlo, and J. Kossut

Appl. Phys. Lett. 72, 206 (1998); http://dx.doi.org/10.1063/1.120686 (3 pages) | Cited 5 times

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By studying the diffusion of specially incorporated thin Mn markers in molecular beam epitaxy-grown CdTe, we can investigate quantitatively deviations from stoichiometry as well as the details of Cd diffusion in the crystal. In CdTe layers deficient in Cd, the diffusion proceeds through VCd vacancies, with the activation energy of 2.1 eV, characteristic for bulk CdTe. In CdTe grown in excess Cd flux, the evaluated activation energy of 1.4 eV for Cd self-diffusion is characteristic to Te self-diffusion in bulk CdTe, which implies that the flow of Cd atoms is mediated by VTe vacancies with formation of a virtual CdTe antisite defect. A striking correlation of the occurrence of the minimum of electrical resistivity in In-doped CdTe with nearly perfect stoichiometry with the minimum of the diffusivity of Mn provides further support of this interpretation. © 1998 American Institute of Physics.
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66.30.H- Self-diffusion and ionic conduction in nonmetals
66.30.J- Diffusion of impurities
61.66.Bi Elemental solids
61.66.Dk Alloys
61.72.J- Point defects and defect clusters
73.61.Ga II-VI semiconductors
68.60.Wm Other nonelectronic physical properties
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