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1 Oct 2005

Volume 98, Issue 7, Articles (07xxxx)

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Thermal-expansion anomaly and spontaneous magnetostriction of Nd2AlFe15Mn compound

Yanming Hao, Miao Zhao, and Yan Zhou

J. Appl. Phys. 98, 076101 (2005); http://dx.doi.org/10.1063/1.2071448 (3 pages) | Cited 4 times

Online Publication Date: 3 October 2005

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The structure and magnetic properties of Nd2AlFe15Mn compound have been investigated by means of x-ray diffraction and magnetization measurements. The Nd2AlFe15Mn compound has a rhombohedral Th2Zn17-type structure. The small thermal-expansion coefficient of Nd2AlFe15Mn compound was found by x-ray diffraction in temperature range of 103–342 K. Especially in the 282–342 K, the small thermal-expansion coefficient is nearly equal to zero. An anisotropic and strong positive spontaneous magnetostriction exists in Nd2AlFe15Mn compound. The magnetostrictive deformations were discussed.
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65.40.De Thermal expansion; thermomechanical effects
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Einstein relation for disordered semiconductors: A dimensionless analysis

Thanh H. Nguyen and Stephen K. O’Leary

J. Appl. Phys. 98, 076102 (2005); http://dx.doi.org/10.1063/1.2060961 (3 pages) | Cited 2 times

Online Publication Date: 3 October 2005

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We present a generalized Einstein relation analysis, applicable for disordered semiconductors with exponential distributions of tail states and square-root distributions of band states. The results of this analysis, a series of plots for the ratio between the diffusion coefficient and the mobility, are cast in a dimensionless form. This will allow the experimentalist to simply “look up” the required results without the need for further analysis.
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71.23.Cq Amorphous semiconductors, metallic glasses, glasses
72.20.Fr Low-field transport and mobility; piezoresistance
66.30.-h Diffusion in solids

Study of the hyperradiance from phase-locked soliton oscillators

Chang Lin and Xiu-lian Zhang

J. Appl. Phys. 98, 076103 (2005); http://dx.doi.org/10.1063/1.2076441 (3 pages) | Cited 4 times

Online Publication Date: 6 October 2005

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The hyperradiance from phase-locked soliton oscillators is investigated by using a family of solutions for the unperturbed sine-Gordon equation. Analytical descriptions for the emitted power from phase-locked soliton oscillators have been obtained for the two magnetically coupled long Josephson junctions operated in single-fluxon modes. We derive an intact mathematical expression and some simulation results of space-time action for the theory for superradiance from phase-locked oscillators.
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03.75.Lm Tunneling, Josephson effect, Bose-Einstein condensates in periodic potentials, solitons, vortices, and topological excitations
05.45.Yv Solitons

Nanoscale topography-capacitance correlation in high-K films: Interface heterogeneity related electrical properties

J. M. Sturm, A. I. Zinine, H. Wormeester, Bene Poelsema, R. G. Bankras, J. Holleman, and J. Schmitz

J. Appl. Phys. 98, 076104 (2005); http://dx.doi.org/10.1063/1.2077840 (3 pages) | Cited 2 times

Online Publication Date: 6 October 2005

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Kelvin probe force microscopy in ultrahigh vacuum was used to study inhomogeneities of the contact potential difference (CPD) and differential capacitance of thin atomic layer deposited Al2O3 films. CPD fluctuations correlate equally strongly with the surface topography for deposition on hydrogen-terminated Si and thermal SiO2. The correlation of the differential capacitance with the topography clearly distinguishes films based on the starting surface. The lateral electrical homogeneity of these thin oxides depends crucially on their initial nucleation.
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68.35.Ct Interface structure and roughness
68.55.−a

Dopant local bonding and electrical activity near Si(001)-oxide interfaces

Zhiyong Zhou, Michael L. Steigerwald, Richard A. Friesner, Louis Brus, and Mark S. Hybertsen

J. Appl. Phys. 98, 076105 (2005); http://dx.doi.org/10.1063/1.2071447 (3 pages) | Cited 3 times

Online Publication Date: 7 October 2005

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Electronic structure calculations based on a density-functional approach have been performed for P, As, B, and Al subsitutional dopants near the Si(001)-oxide interface. The structures are geometrically optimized for each charge state. P and As geometries show a strong distortion when neutral, and regain tetrahedral local bonding when ionized. This geometry change creates an activation barrier for the release of the electron. Distorted neutral dopants may react with hydrogen during the forming gas interface passivation. In contrast, B and Al show tetrahedral bonding for all charge states. All four neutral dopants show substantial energy gain upon formation of dimer complexes near the interface. Neutral B is significantly more stable when bonded to two O atoms at the interface, while neutral P is more stable bonded to four Si atoms adjacent to the interface.
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73.20.At Surface states, band structure, electron density of states
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.72.uf Ge and Si

Carbon nanotube quantum dots fabricated on a GaAs/AlGaAs two-dimensional electron gas substrate

T. Tsukamoto, S. Moriyama, D. Tsuya, M. Suzuki, T. Yamaguchi, Y. Aoyagi, and K. Ishibashi

J. Appl. Phys. 98, 076106 (2005); http://dx.doi.org/10.1063/1.2077841 (3 pages) | Cited 11 times

Online Publication Date: 7 October 2005

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Single-wall carbon nanotube (SWCNT) quantum dots have been fabricated on a GaAs/AlGaAs two-dimensional electron gas (2DEG) substrate, and the single electron transport measurements have been carried out at 2.8 K and 22 mK with the 2DEG used as a gate. It was demonstrated that the gating by the 2DEG could be switched on and off by controlling a quantum point contact fabricated between the dot and the Ohmic contact to the 2DEG gate. The unique combination of the SWCNT dot and the 2DEG may open a door to realize flexible hybrid devices.
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73.63.Fg Nanotubes
73.63.Kv Quantum dots
73.63.Rt Nanoscale contacts
73.40.Ns Metal-nonmetal contacts

Light-output enhancement of GaN-based light-emitting diodes by using hole-patterned transparent indium tin oxide electrodes

Dong-Seok Leem, Jaehee Cho, Cheolsoo Sone, Yongjo Park, and Tae-Yeon Seong

J. Appl. Phys. 98, 076107 (2005); http://dx.doi.org/10.1063/1.2081117 (3 pages) | Cited 12 times

Online Publication Date: 7 October 2005

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We have demonstrated the improvement of the light-output power of GaN-based light-emitting diodes (LEDs) using hole-patterned indium tin oxide (ITO) p-type electrodes. Hole patterns were defined by a laser holographic lithography combined with a postlithography deposition process. It is shown that near-UV LEDs made with the patterned ITO with a hole period of 710 nm and a size of 320 nm give 23% and 67% higher light-output power (at 20 mA) than those of LEDs with unpatterned ITO and Ni/Au contacts, respectively. It is further shown that the reduction of the hole period results in an additional improvement of light-output power.
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85.60.Jb Light-emitting devices
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer

The role of the chemical nature of implanted species on quenching and recovery of photoluminescence in ion-irradiated porous silicon

L. G. Jacobsohn, D. W. Cooke, B. L. Bennett, R. E. Muenchausen, and M. Nastasi

J. Appl. Phys. 98, 076108 (2005); http://dx.doi.org/10.1063/1.2081118 (3 pages) | Cited 1 time

Online Publication Date: 10 October 2005

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The effects of ion irradiation on porous Si (po-Si) photoluminescence (PL) have been investigated. Specimens were progressively irradiated with H+ and He+ ions followed by PL measurements. After the final irradiation, which resulted in total PL quenching, PL recovery was monitored for more than 200 days. The behavior of both PL quenching and recovery was correlated to the amount of retained irradiation-induced damage, determined by channeling spectrometry measurements, and to the chemical nature of the implanted species. Quenching was attributed to the generation of defects that create nonradiative states within the gap, while recovery was attributed to the passivation of these defects by atmospheric exposure. H+ irradiation is approximately five times more efficient in quenching PL and leads to approximately four times lower recovery rate than He+ irradiation. This behavior is attributed to the formation of stable H-defect complexes.
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78.55.Ap Elemental semiconductors
61.80.Jh Ion radiation effects
61.43.Gt Powders, porous materials
81.65.Rv Passivation

Epitaxial growth mechanism of L10 FePt thin films on Pt/Cr bilayer with amorphous glass substrate

An-Cheng Sun, P. C. Kuo, Jen-Hwa Hsu, H. L. Huang, and Jui-Ming Sun

J. Appl. Phys. 98, 076109 (2005); http://dx.doi.org/10.1063/1.2073967 (3 pages) | Cited 20 times

Online Publication Date: 14 October 2005

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Ordered L10 FePt films with magnetic perpendicular anisotropy were fabricated with a Pt/Cr bilayer. The squareness of the L10 FePt film with a Cr underlayer and a Pt buffer was close to one when a magnetic field was applied perpendicular to the film’s plane, because a semicoherent epitaxial growth was initiated from the Cr (002) underlayer; continued through the Pt buffer layer, and extended into the L10 FePt (001) magnetic layer. Without the Pt buffer layer, the Cr atoms may diffuse directly into the FePt magnetic layer. Consequently, an epitaxial barrier of the Cr-rich FePtCr alloy formed between the Cr underlayer and the FePt magnetic layer, degrading the magnetic performance and epitaxial growth of the latter.
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68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy

Hysteresis in gadolinium oxide metal-oxide-semiconductor capacitors

Li-Zen Hsieh, Hong-Hsi Ko, Ping-Yu Kuei, Liann-Be Chang, and Ming-Jer Jeng

J. Appl. Phys. 98, 076110 (2005); http://dx.doi.org/10.1063/1.2084333 (3 pages) | Cited 4 times

Online Publication Date: 14 October 2005

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This investigation explores how oxidation affects the gadolinium oxide capacitor and the corresponding Gd2O3 hysteresis phenomenon. The current-voltage varied with Gd2O3 thickness and a charged capacitance voltage (C-V) curve with a left shift is also observed in experimental results. The breakdown voltages rise with increasing oxidation time, while the corresponding C-V hysteresis gaps decrease with increasing oxidation time.
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84.32.Tt Capacitors
77.80.Dj Domain structure; hysteresis
77.22.Jp Dielectric breakdown and space-charge effects

Magnetic tunnel transistor with a silicon hot-electron emitter

P. LeMinh, H. Gokcan, J. C. Lodder, and R. Jansen

J. Appl. Phys. 98, 076111 (2005); http://dx.doi.org/10.1063/1.2084335 (3 pages) | Cited 2 times

Online Publication Date: 14 October 2005

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We report on a modified magnetic tunnel transistor having a silicon tunnel emitter. The device has the structure Si/Al2O3/base/Si with a spin-valve metal base, a Schottky barrier collector, but a silicon emitter separated from the base by a thin tunnel oxide. The energy of the hot electrons injected from the Si emitter into the base can be tuned by the emitter bias, which drops partly over the Si depletion region. Compared to a magnetic tunnel transistor with a metal emitter, the voltage drop over the thin tunnel oxide is reduced, enabling stable device operation at higher biasing conditions. We fabricated devices with a magnetocurrent up to 166% and a steeply enhanced transfer ratio reaching 6×10−4 at an emitter current of 200 mA.
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85.30.Tv Field effect devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
73.30.+y Surface double layers, Schottky barriers, and work functions
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