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27 Jul 1987

Volume 51, Issue 4, pp. 209-290

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Lasing wavelength of an asymmetric double quantum well laser diode

Yasunori Tokuda, Teruhito Matsui, Kenzo Fujiwara, Noriaki Tsukada, and Takashi Nakayama

Appl. Phys. Lett. 51, 209 (1987); http://dx.doi.org/10.1063/1.98477 (3 pages) | Cited 6 times

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It is demonstrated that in an asymmetric coupled GaAs double quantum well structure, we are able to choose a lasing wavelength out of at least four quantum state transitions by cavity loss control. The assignments of the observed lasing transitions are determined by photoluminescence measurement for the laser wafer, as well as by calculations using an isolated potential well model. We propose that one can realize wide‐range wavelength tuning and multistep wavelength switching functions by modifying the two‐dimensional density of states.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
78.55.Cr III-V semiconductors
42.55.Rz Doped-insulator lasers and other solid state lasers

Optoelectronic transmission and reception of ultrashort electrical pulses

Alfred P. DeFonzo and Charles R. Lutz

Appl. Phys. Lett. 51, 212 (1987); http://dx.doi.org/10.1063/1.98478 (3 pages) | Cited 28 times

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We report on the recent advances in using integrated planar antenna technology to photoconductively generate and detect picosecond radiation. Detection of a single pulse of picosecond duration has been achieved using a coplanar antenna structure fabricated on a radiation‐damaged silicon‐on‐sapphire substrate.
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84.40.Ba Antennas: theory, components and accessories
85.60.-q Optoelectronic devices
72.40.+w Photoconduction and photovoltaic effects
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

Continuous room‐temperature operation of an InGaAs‐GaAs‐AlGaAs strained‐layer laser

Y. J. Yang, K. Y. Hsieh, and R. M. Kolbas

Appl. Phys. Lett. 51, 215 (1987); http://dx.doi.org/10.1063/1.98479 (3 pages) | Cited 21 times

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We report the first continuous wave room‐temperature InGaAs‐GaAs‐AlGaAs strained‐layer semiconductor laser diode grown by molecular beam epitaxy. The laser is a multiple quantum well transverse junction stripe laser with a lateral heterojunction fabricated by zinc diffusion enhanced compositional disordering. The low‐threshold (20 mA) and single‐mode performance of the laser demonstrates that a high‐quality lateral p+‐p‐n junction and lateral heterobarrier can be formed by zinc diffusion compositional disordering of a strained‐layer InGaAs‐GaAs‐AlGaAs quantum well heterostructure.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
66.30.J- Diffusion of impurities
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Characteristics of an electron beam pumped KrF laser amplifier with an atmospheric‐pressure Kr‐rich mixture in a strongly saturated region

Akira Suda, Hiroshi Kumagai, and Minoru Obara

Appl. Phys. Lett. 51, 218 (1987); http://dx.doi.org/10.1063/1.98480 (3 pages) | Cited 14 times

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Amplifier characteristics of a KrF laser were investigated as a function of Kr concentration for a wide range of input intensity. The experiments were performed with atmospheric‐pressure mixtures excited by a 65‐ns (full width at half‐maximum), 160‐A/cm2 electron beam. The extracted intensity (output intensity minus input intensity) from a single‐pass (50 cm) amplifier was maximized at an input intensity around 5 MW/cm2 and then, the power efficiencies were 12.6, 13.7, 13.3, and 11.3% for Kr concentrations of 10, 20, 40, and 99.4%, respectively. The small‐signal gain, absorption coefficient, and saturation intensity were determined for each mixture by using an analysis due to Rigrod [J. Appl. Phys. 36, 2487 (1965)]. The KrF∗ formation efficiency and the extraction efficiency were also obtained as a function of Kr concentration.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Low‐threshold operation of AlGaAs/GaAs multiple quantum well lasers grown on Si substrates by molecular beam epitaxy

Tow C. Chong and Clifton G. Fonstad

Appl. Phys. Lett. 51, 221 (1987); http://dx.doi.org/10.1063/1.98481 (3 pages) | Cited 11 times

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We report the first AlGaAs‐GaAs multiple quantum well (MQW) lasers fabricated on (001)Si substrates by molecular beam epitaxy (MBE) with relatively thin buffer layers. The lasers have broad‐area (170×240 μm) pulsed threshold current density of 3.2 kA/cm2 at room temperature, the lowest ever reported for GaAs lasers grown by MBE on Si. Stripe lasers exhibit external differential quantum efficiencies comparable to those of GaAs lasers grown on GaAs substrates. Clean single longitudinal mode oscillations are observed, with transverse electric field the dominant polarization. The lasers also exhibit well‐behaved fast pulse response, with a measured carrier lifetime of ∼2.2 ns in the active region. The improved performance is attributed to the employment of graded‐index MQW structures and improved growth techniques.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Single longitudinal mode operation of semiconductor laser arrays with étalon feedback

H. Hemmati

Appl. Phys. Lett. 51, 224 (1987); http://dx.doi.org/10.1063/1.98455 (2 pages) | Cited 6 times

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The multiple longitudinal mode output of high‐power diode‐laser arrays is converted into single mode with 97% efficiency by optical feedback from a thin (<200 μm thick) étalon external to the laser. The coupled cavities formed by addition of the étalon favor a single longitudinal mode. Single‐mode operation is retained at 0.1 MHz pulsed rates. Both the near‐field and the far‐field patterns of the laser array remain nearly unchanged while the array operates in a single longitudinal mode.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Carrier trapping in single quantum wells with different confinement structures

J. Feldmann, G. Peter, E. O. Göbel, K. Leo, H.‐J. Polland, K. Ploog, K. Fujiwara, and T. Nakayama

Appl. Phys. Lett. 51, 226 (1987); http://dx.doi.org/10.1063/1.98456 (3 pages) | Cited 51 times

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The trapping efficiency and trapping dynamics of photoexcited carriers in GaAs/AlGaAs single quantum wells with different confinement structures are examined at low temperature by means of picosecond luminescence as well as photoluminescence excitation spectroscopy. The trapping efficiency is 100% only in graded‐index separate confinement heterostructures with a linear band‐gap profile. The lower trapping efficiency of other confinement structures is due to radiative and nonradiative recombination in the confinement layers.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Cr III-V semiconductors

On‐line plasma diagnostic by neutral atom time of flight analysis

V. Dose and H. Verbeek

Appl. Phys. Lett. 51, 229 (1987); http://dx.doi.org/10.1063/1.98457 (3 pages) | Cited 3 times

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Elementary procedures of linear algebra and numerical integration are combined for processing neutral atom time of flight spectra from a tokamak plasma. The method presented provides for on‐line information about total neutral particle flux, mean energy, wall erosion rates, etc. at a time resolution of a single time of flight cycle.
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52.70.Nc Particle measurements
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation
52.55.Fa Tokamaks, spherical tokamaks

Unlubricated friction and wear of an ion beam mixed, nitrogen‐implanted Fe50Ti50 surface alloy on AISI 304 stainless steel

J‐P. Hirvonen, M. Nastasi, and J. W. Mayer

Appl. Phys. Lett. 51, 232 (1987); http://dx.doi.org/10.1063/1.98458 (3 pages) | Cited 12 times

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Nitrogen implantation was observed to significantly improve the dry sliding properties of an ion beam mixed Fe50Ti50 surface alloy on AISI 304 stainless steel. Implantation to the fluence of 1.7×1017 N/cm2 at 50 keV increased the wear resistance but a decreased friction coefficient was obtained only after few hundred cycles at the beginning of the pin‐on‐disk test. When nitrogen was implanted to the fluence of 3×1017 N/cm2 an improved wear resistance and decreased friction were detected throughout the test of 1000 cycles. In addition, good sliding properties were also found at higher loads in the high fluence, nitrogen‐implanted samples. These results differ from those obtained following a nitrogen implantation into Ti‐implanted iron or iron‐based alloys and are attributed to higher titanium and nitrogen concentrations.
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62.20.Qp Friction, tribology, and hardness
68.35.Gy Mechanical properties; surface strains
68.60.Bs Mechanical and acoustical properties
81.40.Pq Friction, lubrication, and wear

New type cryogenic thermometer using sputtered Zr‐N films

Tsutom Yotsuya, Masaaki Yoshitake, and Junya Yamamoto

Appl. Phys. Lett. 51, 235 (1987); http://dx.doi.org/10.1063/1.98459 (3 pages) | Cited 13 times

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A new type thin‐film thermometer using sputtered Zr‐N films especially for cryogenic temperature range has been developed. Zr‐N thermometers have high sensitivity in a wide temperature region from 300 to 2 K or even lower, and have a response quick enough to detect the second sound in superfluid helium. It is found that the developed thermometers are insensitive to magnetic field. Temperature error induced by application of magnetic field up to 6 T is only less than 4.5 mK at 4.2 K.
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07.20.Dt Thermometers
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
73.61.Ng Insulators

Slip dislocation propagation in In‐doped liquid encapsulated Czochralski GaAs during crystal growth

Haruhiko Ono, Tomohisa Kitano, and Junji Matsui

Appl. Phys. Lett. 51, 238 (1987); http://dx.doi.org/10.1063/1.98991 (3 pages) | Cited 1 time

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A propagation rule was studied for two types of slip dislocations arising during crystal growth. In order to specify the dislocation distribution revealed by x‐ray topography, we considered the relationship among the slip system, thermal gradient, and stress field. One type of slip dislocation was found to propagate on slip systems having a maximum Schmid factor in a uniform radial stress field, while another well known type occurred in a tangential stress field. It was concluded that different slip systems can be activated by specific stress fields caused by different thermal gradients under various growth conditions.
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61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Bb Theories and models of crystal defects
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation
81.10.Fq Growth from melts; zone melting and refining

Microfabricated structures for the in situ measurement of residual stress, Young’s modulus, and ultimate strain of thin films

Mark G. Allen, Mehran Mehregany, Roger T. Howe, and Stephen D. Senturia

Appl. Phys. Lett. 51, 241 (1987); http://dx.doi.org/10.1063/1.98460 (3 pages) | Cited 92 times

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Two microfabricated structures for the in situ measurement of mechanical properties of thin films, a suspended membrane, and an asymmetric ‘‘released structure,’’ are reported. For a polyimide film on silicon dioxide, the membrane measurements yield a residual tensile stress of 30 MPa and a Young’s modulus of 3 GPa. The released structures measure the ratio of residual stress to Young’s modulus, and yield 0.011 at strains comparable to the suspended membranes, and 0.015 at larger strains. The ultimate strain as measured by both structures is approximately 4%.
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68.60.Bs Mechanical and acoustical properties
46.80.+j Measurement methods and techniques in continuum mechanics of solids

Nanometer scale structure fabrication with the scanning tunneling microscope

U. Staufer, R. Wiesendanger, L. Eng, L. Rosenthaler, H. R. Hidber, H.‐J. Güntherodt, and N. Garcia

Appl. Phys. Lett. 51, 244 (1987); http://dx.doi.org/10.1063/1.98461 (3 pages) | Cited 42 times

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Nanometer scale structures have been produced on atomically flat surfaces of metallic glasses using the scanning tunneling microscope in the tunneling mode with enhanced local current densities and strong electric fields. Depending on the current and the electric field enhanced diffusion, local crystallization of the glassy state or Taylor cone formation of the locally molten surface can occur. These structures provide a potential means of studying the behavior of matter at nanometer dimensions.
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81.05.Kf Glasses (including metallic glasses)
81.65.-b Surface treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Direct writing of submicron metallic features with a scanning tunneling microscope

R. M. Silver, E. E. Ehrichs, and A. L. de Lozanne

Appl. Phys. Lett. 51, 247 (1987); http://dx.doi.org/10.1063/1.98462 (3 pages) | Cited 56 times

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We demonstrate for the first time that the scanning tunneling microscope can be used to write metallic features on a surface without further process steps. Using organometallic gases we have obtained features down to 20 nm in size.
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81.05.Bx Metals, semimetals, and alloys
85.40.Bh Computer-aided design of microcircuits; layout and modeling
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
73.40.Gk Tunneling

Roughening of Si (111) surface under high‐temperature thermal cycling

J.‐K. Zuo, R. A. Harper, and G.‐C. Wang

Appl. Phys. Lett. 51, 250 (1987); http://dx.doi.org/10.1063/1.98463 (3 pages) | Cited 26 times

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High‐resolution low‐energy electron diffraction has been used to study the generation of defects on the surface of commercial Si (111) wafers under high‐temperature thermal cycling in ultrahigh vacuum. We observed a gradual increase of single‐atomic step density from 0.15 to 0.30% after several thermal annealings at ∼1200 °C. However, a reduction of step density, accompanied by a change of step height from single‐atomic to double‐atomic step height, was observed after the sample was annealed to near melting temperature (∼1400 °C). At the same time, the surface was broken into micrograins having a small mosaic orientation. Due to the limited instrumental resolution, these low‐density step structures and the small‐angle mosaic structures cannot be resolved by using the conventional low‐energy electron diffraction technique.
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68.35.Dv Composition, segregation; defects and impurities
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.40.Gh Other heat and thermomechanical treatments
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Phosphorus doping for hydrogenated amorphous silicon films by a low‐energy ion doping technique

A. Yoshida, K. Setsune, and T. Hirao

Appl. Phys. Lett. 51, 253 (1987); http://dx.doi.org/10.1063/1.98464 (3 pages) | Cited 11 times

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A heated film of hydrogenated amorphous silicon was doped with phosphorus and hydrogen by a 6.0‐kV diffused and accelerated beam of ions from rf discharge in a magnetic field, which produced a plasma from phosphine gas containing hydrogen. This doping technique achieved a dark conductivity of 8.7×10−4 (Ω cm−1) at room temperature. The conductivity activation energy was 0.17 eV.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
73.50.Pz Photoconduction and photovoltaic effects

Interstitial defect reactions in silicon

M. T. Asom, J. L. Benton, R. Sauer, and L. C. Kimerling

Appl. Phys. Lett. 51, 256 (1987); http://dx.doi.org/10.1063/1.98465 (3 pages) | Cited 78 times

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Deep level transient spectroscopy has been employed in a study of impurity‐interstitial defect reactions in silicon following room‐temperature electron irradiation. Three defects have been isolated and identified from their reactions and electrical properties as Cs‐Ci, Ci‐Oi, and Ps‐Ci. The Cs‐Ci, ME[(0.10), (0.17)] and Ps‐Ci, ME[(0.21), (0.23), (0.27), (0.30)] defects exhibit metastable structural transformations. Our results reveal the multistructural nature and chemical reactivity of the silicon self‐interstitial.
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78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys
61.72.jd Vacancies
61.72.jj Interstitials
61.80.Fe Electron and positron radiation effects
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Electron beam recrystallization of plasma‐sprayed silicon substrates

R. Suryanarayanan, M. Akani, R. Gauthier, R. M’Ghaieth, and P. Pinard

Appl. Phys. Lett. 51, 259 (1987); http://dx.doi.org/10.1063/1.98466 (2 pages) | Cited 3 times

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Polycrystalline silicon substrates of 5–8 cm2 area and 0.5–3 mm thickness have been recrystallized by electron beam glazing. The grain size as well as the Hall mobility increases dramatically from 50 μm to 1 mm or more and from 5 to 320 cm2/V s, respectively.
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81.40.Rs Electrical and magnetic properties related to treatment conditions
61.80.Fe Electron and positron radiation effects
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.Mm Grain and twin boundaries

Molecular beam epitaxial growth and luminescence of InxGa1−xAs/InxAl1−xAs multiquantum wells on GaAs

Kevin H. Chang, Paul R. Berger, Jasprit Singh, and Pallab K. Bhattacharya

Appl. Phys. Lett. 51, 261 (1987); http://dx.doi.org/10.1063/1.98467 (3 pages) | Cited 2 times

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This letter reports the successful molecular beam epitaxial growth of high‐quality InxGa1−xAs/InxAl1−xAs directly on GaAs. In situ observation of dynamic high‐energy electron diffraction oscillations during growth of InxGa1−xAs on GaAs indicates that the average cation migration rates are reduced due to the surface strain. By raising the growth temperature to enhance the migration rate and by using misoriented epitaxy to limit the propagation of threading and screw dislocations, we have grown device‐quality In0.15Ga0.85As/In0.15Al0.85As multiquantum wells on GaAs with a 0.5–1.0 μm In0.15Ga0.85As buffer layer. The luminescence efficiency of the bound exciton peak increases with misorientation and its linewidth varies from 11 to 15 meV.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Quantum shift of the optical absorption edge in ultrathin amorphous hydrogenated germanium

L. Yang and B. Abeles

Appl. Phys. Lett. 51, 264 (1987); http://dx.doi.org/10.1063/1.98468 (3 pages) | Cited 6 times

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The optical absorption coefficient in ultrathin (∼10 Å) hydrogenated amorphous germanium (a‐Ge:H) layers deposited on hydrogenated amorphous silicon layers was determined by in situ reflectivity measurements. The decrease in the absorption coefficient in the ultrathin a‐Ge:H layers, compared to that of thick films, is explained by an upward shift in the conduction band edge due to quantum confinement of electrons with effective mass of 0.4m0.
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78.66.-w Optical properties of specific thin films

Novel high quantum efficiency Si‐TaSi2 eutectic photodiodes

B. M. Ditchek, B. G. Yacobi, and M. Levinson

Appl. Phys. Lett. 51, 267 (1987); http://dx.doi.org/10.1063/1.98469 (3 pages) | Cited 8 times

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A high quantum efficiency photodiode has been fabricated using the in situ junctions in a Si‐TaSi2 eutectic composite. Due to the three‐dimensional distribution of junctions in this photodiode, it yields a nearly constant quantum efficiency of about 50% between 450 and 1000 nm. In addition, the average lateral distance between junctions of only 8 μm gives this novel photodiode an inherently good spatial resolution for photodiode array applications.
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85.60.Dw Photodiodes; phototransistors; photoresistors

Two distinct interface trap peaks in radiation‐damaged metal/SiO2/Si structures

Eronides F. da Silva, Yasushiro Nishioka, and T.‐P. Ma

Appl. Phys. Lett. 51, 270 (1987); http://dx.doi.org/10.1063/1.98470 (3 pages) | Cited 27 times

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Two distinct peaks in the interface trap distribution on (100) Si, one above and the other below the Si midgap energy, have been observed in a wide selection of metal/SiO2/Si capacitors after they are exposed to ionizing radiation. The samples tested cover a wide range of gate electrode materials (Al, polycrystalline Si, Mo, and TiSi2) and oxidation environments [dry O2, steam, dry O2+TCA (trichloroethane), and dry O2+HCl at various temperatures]. Among all the samples tested, the peak above midgap (∼Ev+0.75 eV) appeared immediately after irradiation, and for most samples the peak below midgap (∼Ev+0.35 eV) only appeared at long times (up to a few months) after irradiation. The evolution of the two peaks as a function of time has been found to depend strongly on the gate electrode, oxidation environment, sample storage temperature, and gate bias during storage. Detailed studies of these two peaks should lead to a better understanding of the defect formation process at the SiO2/Si interface.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
61.80.Jh Ion radiation effects

Low‐threshold 1.55‐μm InGaAsP/InP buried heterostructure distributed feedback lasers

K. Chinen, K. Gen‐ei, H. Suhara, A. Tanaka, T. Matsuyama, K. Konno, and Y. Muto

Appl. Phys. Lett. 51, 273 (1987); http://dx.doi.org/10.1063/1.98471 (3 pages) | Cited 2 times

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An extremely low‐threshold current of 6 mA in cw mode at 22 °C was achieved in 1.55‐μm InGaAsP/InP buried heterostructure distributed feedback lasers with a first‐order grating and a normal cavity length of 300 μm. These lasers exhibited an average differential efficiency of 30% total at 4 mW without any coating on the facets, and a T0 (25–70 °C) value of 55 K. A spectral linewidth as low as 8 MHz at cw mode was obtained. The lasers showed high‐speed pulse modulation response to 2.4 Gb/s (NRZ).
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

New resonant tunneling superlattice avalanche photodiode device structure for long‐wavelength infrared detection

C. J. Summers and K. F. Brennan

Appl. Phys. Lett. 51, 276 (1987); http://dx.doi.org/10.1063/1.98992 (3 pages) | Cited 2 times

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A new device structure useful in detecting long‐wavelength radiation which uses a variably spaced superlattice both to inject photogenerated electrons into a wider band‐gap semiconductor and to promote efficient impact ionization and gain at low bias voltages is proposed. Both of these properties result directly from the unique property of the superlattice structure to create a near monoenergetic stream of electrons and inject them at high energy into an adjacent semiconducting layer. Thus for the first time it should be possible to obtain long‐wavelength sensors with high gain (∼103), ultralow noise, and high detectivity.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Superconductivity in YBa2−xSrxCu3O7−δ

B. W. Veal, W. K. Kwok, A. Umezawa, G. W. Crabtree, J. D. Jorgensen, J. W. Downey, L. J. Nowicki, A. W. Mitchell, A. P. Paulikas, and C. H. Sowers

Appl. Phys. Lett. 51, 279 (1987); http://dx.doi.org/10.1063/1.98472 (3 pages) | Cited 91 times

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We report structure, resistivity, and Meissner effect measurements on YBa2−xSrxCu3O7−δ for 0<x<2.0. We find a region of solid solubility extending at least to x=1.0 and a monotonic depression of Tc with x. Using arguments based on structural changes with Sr doping, we speculate that the depression of Tc is due to the local distortion of the lattice in the neighborhood of the Sr site and the introduction of additional oxygen vacancies.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.70.-b Superconducting materials other than cuprates
61.66.Fn Inorganic compounds
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