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18th International Symposium on Integrated Ferroelectrics (ISIF 2006)

作者： Wang, Longhai Yu, Jun Wang, Yunbo Gao, Junxiong Zhao, Suling Wang, Zhihong Zeng, Huizhong Department of Electronic Science and Technology Huazhong University of Science and Technology Wuhan 430074 China Center for Materials Research and Analysis Wuhan University of Technology Wuhan 430070 China School of Microelectronics and Solid State Electronics University of Electronic Science and Technology of China Chengdu 610054 China

The multilayer PbTiO3/PbZr0.3Ti0.7O3/PbTiO3(PT/PZT/PT) thin films were prepared by a Sol-Gel method on the Pt(111)/Ti/SiO2/Si(100) substrate for FeRAM application. The XRD patterns exhibits a perfect perovskite-phase with strong (111)-preferred orientation. The domain structures were investigated by scanning force microscopy. The out-of-plane polarization (OPP), in-plane polarization (IPP), the OPP amplitude and OPP phase images were obtained. The domain of the films has a complex structure with c-domain and deviated - c-domain which direction deviated from the vertical direction of surface of the film. The complex domain structure is related to the orientation of the crystal grains in the film. The results of ferroelectric, fatigue, dielectric and leakage current density indicate that the thin film has a better property. It has larger saturation polarization Pmax of 57.6 C/cm2 at an applied voltage of 10 V, higher remnant polarization Pr of 32.3 C/cm2 for a the conceive voltage (Vc) of 2.5 V. After 1010 cycles, it still has more than 80% remnant polarization. The dielectric constants decreased with the frequency increased, and the decrease became slightly up to 1 MHz. The dielectric loss increased with the frequency increased, and there are no abrupt changes in the scan region. The leakage current mechanism of the thin film can be modeled in terms of SCLC theory.

关键词： Thin films

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Developing an atomic-level understanding of the mechanisms that govern CO2 sequestration mineral carbonation reaction processes

Developing an atomic-level understanding of the mechanisms t...

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2005 TMS Annual Meeting

作者： McKelvy, Michael J. Chizmeshya, Andrew V. G. Diefenbacher, Jason Béarat, Hamdallah Carpenter, R.W. Wolf, George Gormley, Deirdre Center for Solid State Science Arizona State University Tempe AZ 85287 United States Science and Engineering of Materials Graduate Program Arizona State University Tempe AZ 85287 United States Department of Chemistry and Biochemistry Arizona State University Tempe AZ 85287 United States

Mineral carbonation is an emerging CO2 sequestration candidate technology, which produces environmentally benign and geologically stable materials. The primary challenge is economically viable process development. Serpentine and olivine minerals are candidate feedstock materials of interest, due to their wide availability, low-cost, and rapid mineral carbonation potential. Cost-effectively enhancing their carbonation reactivity is critical to reducing mineral sequestration process cost. We will discuss our recent research into the mechanisms that govern serpentine and olivine mineral carbonation reaction processes, including in situ observations of the mineral carbonation process and a novel mechanistic approach to enhance carbonation reactivity that avoids the cost of mineral activation. Our goal is to develop the necessary atomic-level understanding to engineer improved carbonation materials and processes to reduce process cost.

关键词： Chemical reactions

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solid-state lighting: Toward superior illumination

Solid-state lighting: Toward superior illumination

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作者： Shur, Michael S. Žukauskas, Arturas IIEE Japan Department of Electrical Computer and Systems Engineering and Physics Rensselaer Polytechnic Institute Troy NY 12180 United States Institute of Materials Science and Applied Research Vilnius University Vilnius 10222 Lithuania Department of Solid State Electronics United States Department of Physics Applied Physics and Astronomy United States Center for Broadband Data Transport Science and Technology Rensselaer Polytechnic Institute Troy NY United States American Physical Society United States Electrochemical Society United States World Innovation Foundation United States Eta Kappa Nu Electromagnetic Academy Materials Research Society United States American Society for Engineering Education United States SPIE United States American Association for the Advancement of Science United States IEEE Sensor Council United States Institute of Materials Science and Applied Research Lithuania Department of Semiconductor Physics Lithuania Lithuanian Physical Society Lithuania Lithuanian Materials Research Society Lithuania Lithuanian Academy of Sciences Lithuania

solid-state lighting technology is now emerging as a cost-competitive, energy-efficient alternative to conventional electrical lighting. We review the history of lighting, discuss the benefits and challenges of the solid-state lighting technologies, and compare two approaches for generating white light from solid-state sources based on phosphor LEDs (which could be considered as solid-state replacement of fluorescent tubes) and multichip LED lamps, which offer many advantages, such as chromaticity control, better light quality, and higher efficiency. © 2005 IEEE.

关键词： solid state devices

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Optical Reflectance of Bulk AlN Crystals and AlN Epitaxial Films

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AIP Conference Proceedings 2005年第1期772卷 297-298页

作者： L. Chen B. J. Skromme C. Chen W. Sun J. Yang M. A. Khan M. L. Nakarmi J. Y. Lin H. X. Jiang Z. J. Reitmeyer R. F. Davis R. F. Dalmau R. Schlesser Z. Sitar *Department of Electrical Engineering Arizona State University Tempe AZ 85287‐5706 **Center for Solid State Electronics Research Arizona State University Tempe AZ 85287‐5706 †Department of Electrical Engineering University of South Carolina Columbia SC 29208 ¶Department of Physics Kansas State University Manhattan KS 66506‐2601 ‡Department of Materials Science & Engineering North Carolina State University Raleigh NC 27695

The A exciton feature at 6.025 eV is observed directly in the low temperature (1.8 K) reflectance spectra of AlN for the first time, using a bulk AlN single crystal which has a relatively flat m‐face that allows both σ and π configurations. Features involving unresolved B and C excitons are also observed around 6.25 eV from this sample and in three c‐oriented MOCVD AlN films. Transmission measurements on the thickest film reveal a clear but weak A excitonic absorption feature at 6.080 eV. The results are explained by theoretical calculations of exciton energies and oscillator strengths. The calculations suggest that AlGaN light‐emitting devices will emit light mainly in the π polarization for wavelengths shorter than 320 nm.

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Rapid Synthesis of Crystalline Spinel Tin Nitride by a solid-state Metathesis Reaction

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Journal of the American Ceramic Society 2004年第1期85卷 101-104页

作者： Michael P. Shemkunas George H. Wolf Kurt Leinenweber William T. Petuskey Science and Engineering of Materials Program Department of Chemistry and Biochemistry and Materials Research Science and Engineering Center Arizona State University Tempe Arizona 85287-1604 Member American Ceramic Society.

Spinel tin nitride (Sn 3 N 4 ) was prepared by high-pressure solid-state metathesis reactions. Tin tetraiodide was reacted with lithium nitride and ammonium chloride in a piston–cylinder apparatus at 623 K and 2.5 GPa. Powder X-ray diffraction combined with Rietveld refinement confirmed the spinel structure, with a lattice constant of a = 9.0144(1) Å. Raman spectroscopy revealed five active vibrational modes at 160, 252, 416, 524, and 622 cm −1 , which are consistent with the spinel structure. Mid-infrared spectroscopy exhibited only a Sn–N stretching mode at 547 cm −1 . Transmission electron microscopy was used to reveal particle size and morphology. Electron probe microanalysis was used to verify the elemental composition.

关键词： synthesis spinels tin/tin compounds nitrides

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Structural Defect-Related Photoluminescence in GaN

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MRS Online Proceedings Library 2004年第1期798卷 592-597页

作者： L. Chen B. J. Skromme M. K. Mikhov H. Yamane M. Aoki F. J. DiSalvo B. Wagner R. F. Davis P. A. Grudowski R. D. Dupuis Department of Electrical Engineering and Center for Solid State Electronics Research Arizona State University Tempe USA Tohoku University Sendai Japan Department of Chemistry and Chemical Biology Cornell University Ithaca USA Department of Materials Science and Engineering North Carolina State University Raleigh USA Microelectronics Research Center University of Texas Austin USA

Broad, low temperature photoluminescence (PL) peaks near 3.4–3.42 eV in GaN have previously been associated with basal-plane stacking faults. Recently, we observed unusually sharp and highly structured PL peaks in this region in high quality bulk GaN grown from a Na/Ga flux, some of which display characteristic shifts and narrowing as a function of excitation power. Here, we study these peaks as a function of excitation intensity and crystal polarity, and compare them to those observed in GaN grown on off-axis SiC or sapphire (0001) substrates by metalorganic chemical vapor deposition (MOCVD). In the off-axis material on either substrate, similar peaks are observed to those in the bulk samples. In addition, a low energy peak near 3.21 eV is observed, which does not occur in the bulk material.

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Theoretical and experimental study of barium zinc-cadmium tantalate-based microwave dielectrics

Theoretical and experimental study of barium zinc-cadmium ta...

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materials, Integration and Packaging Issues for High - Frequency Devices

作者： Liu, Shaojun Van Schilfgaarde, Mark Sun, Jian Badd, Louisa Smith, David Petrovixc, Novak S. Taylor, R. Newman, N. Chemical Engineering Department United States Sci./Eng. of Materials Program United States Center for Solid State Science Arizona State University Tempe AZ 85287-6006 United States Electrical Engineering Department Queens Land University Paddington 4064 Australia

Single-phase Ba(Cd1/3Ta2/3)O3 ceramics have been produced using conventional powder processing methods. In our initial investigations, 2wt% ZnO powder was added to act as a sintering aid since a high-density ceramic was not formed from solid-state diffusion alone. The resulting Ba(Cd0.327Zn0.006Ta2/3)O3 material sintered at 1550°C exhibits a dielectric constant of ∼33 and loss tangent of -5 at 2 GHz. In our more recent work, we have used boron as a sintering aid to facilitate sintering at temperatures as low as 1300°C, enhance the structural quality and improve the microwave properties of Ba(Cd1/3Ta2/3)O3 dielectrics. TEM results indicate that the liquid sintering mechanism is an important factor for boron concentrations exceeding 0.5wt%, while a point defect mechanism plays the dominant role at lower boron concentrations. The presence of superstructure peaks and splitting of the (220) and (214) peaks in X-ray diffraction spectra are direct evidence for the distortion from cubic symmetry as a result of Cd and Ta ordering on the B-site. Ab-initio electronic structure calculations within the local density functional approximation have been used to give insight into the unusual properties of this class of materials. In both Ba(Zn 1/3Ta2/3)O3 and Ba(Cd/3Ta 2/3)O3, the conduction band maximum and valence band minimum are composed of mostly weakly itinerant Ta 5d-and Zn-3d/Cd-4d levels, respectively. The covalent nature of the directional d-electron bonding in these high-Z oxides plays an important role in producing a more rigid lattice with higher melting points and enhanced phonon energies, and possibly inherently lower intrinsic microwave loss than comparable ionic materials.

关键词： Barium compounds

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Ordered structures in Ba(Cd1/3Ta2/3)O3 microwave ceramics: A transmission electron microscopy study

Ordered structures in Ba(Cd1/3Ta2/3)O3 microwave ceramics: A...

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materials, Integration and Packaging Issues for High - Frequency Devices

作者： Sun, J. Liu, S.J. Newman, N. Smith, David J. Center for Solid State Science Arizona State University Tempe AZ 85287 United States Department of Chemical Engineering Materials and Engineering Program Arizona State University Tempe AZ 85287 United States Department of Physics Arizona State University Tempe AZ 85287 United States Sch. of Mat. Science and Engineering Shanghai Jiao-Tong University Shanghai 20003 China

Ordered structures of Ba(Cd1/3Ta1/2)O3 ceramics with and without boron additive were investigated systemically by electron diffraction and high resolution transmission electron microscopy. The results showed a well-ordered structure of 1:2 with hexagonal symmetry for Ba(Cd1/3Ta1/2)O3 with boron additive. No significant changes in ordered structures were observed after long-period annealing. The 1:2 ordered domain structures (average domain size ∼ 18 nm) and high-density domain boundaries induced by ordering were observed for Ba(Cd1/3Ta1/2)O3 without boron additive sintered at relatively high temperature. The sintering process has a profound influence on the microstructure of Ba(Cd1/3Ta2/3)O 3 ceramics.

关键词： Barium compounds

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Quantum dot infrared detectors and sources

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International Journal of High Speed electronics and Systems 2002年第4期12卷 969-994页

作者： Bhattacharya, P. Stiff-Roberts, A.D. Krishna, Sanjay Kennerly, S. Solid State Electronics Laboratory Department of Electrical Engineering University of Michigan Ann Arbor MI 48109-2122 United States Center for High Technology Materials Department of Electrical Engineering University of New Mexico Albuquerque NM 87106 United States Sensors/Electron Devices Directorate US Army Research Laboratory Adelphi MD 20783 United States

InAs/GaAs quantum dot devices have the potential to be the leading technology for infrared detection and emission, which are necessary for many military and domestic applications. Quantum dot infrared photodetectors yield higher operating temperatures, lower dark currents, and more wavelength tunability. They also permit the detection of normal-incidence light. Quantum dot infrared sources are also expected to yield higher operating temperatures, in addition to lower threshold currents and higher modulation bandwidths. After a brief review of the history of infrared detection and emission, the optical and electrical characteristics of self-organized In(Ga)As/GaAs quantum dots grown by molecular beam epitaxy are discussed, followed by results for the quantum dot detectors and emitters that have been developed at the University of Michigan, Ann Arbor.

关键词： Semiconductor quantum dots

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Spin-orbital ordering and mesoscopic phase separation in the double perovskite Ca2FeReO6

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Physical Review B 2002年第6期66卷 064409-064409页

作者： E. Granado Q. Huang J. W. Lynn J. Gopalakrishnan R. L. Greene K. Ramesha NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899 Center for Superconductivity Research University of Maryland College Park Maryland 20742 Materials Engineering Program University of Maryland College Park Maryland 20742 Solid State and Structural Chemistry Unit Indian Institute of Science Bangalore 560012 India

Neutron powder diffraction measurements on Ca2FeReO6 reveal that this double perovskite orders ferrimagnetically and shows anomalous lattice parameter behavior below TC=521K. Below ∼300K and ∼160K we observe that the high-T monoclinic crystal structure separates into two and three monoclinic phases, respectively. A magnetic field suppresses the additional phases at low T in favor of the highest-T phase. These manifestations of the orbital degree of freedom of Re 5d electrons indicate that these electrons are strongly correlated and the title compound is a Mott insulator, with competing spin-orbitally ordered states.

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