bluuebunny/crossref_metadata_2025_split huggingface dataset:
Industrial/Academic Internships at IBM-Almaden Under NSF Programs
Authors: Wade Charles G. , Miller Dolores , Pesek Joseph , Scharberg Maureen , Waller Brenda , Pauly Malinda , Goldman Marni 
Published: April 2011

ABSTRACTIndustrial experience can be a significant factor in materials science education, and internships at our laboratory under two NSF programs directly impact undergraduates and high school teachers. In these programs, the participants become a member of individual, existing research groups under a mentor on a technical project relevant to IBM. The research is publishable but closely related to a technical area important to IBM. During the summer the participants become members of the research group, attending departmental meetings and informal discussions. In addition, they attend a special seminar series on industrial research frontiers, receive career-training discussions, and participate in a variety of other programs sponsored for summer interns by IBM. Every participant presents a poster at an internal technical meeting at IBM or a technical meeting at Stanford (or both) at the end of the summer. One of the programs, an NSF MRSEC “Center for Polymer Interfaces and Macromolecular Interfaces” (CPIMA), involves a partnership with Stanford University and the University of California at Davis. The CPIMA program has an active group of postdoctoral scientists, graduate students, undergraduate (summer) students and (summer) high school teachers. In addition to IBM, summer students in CPIMA may work with other industrial firms who are industrial affiliates of CPIMA. In addition, CPIMA has a public science and K-12 component in materials science in educational outreach with the The Tech Museum of Innovation in San Jose. The other program, an NSF GOALI grant on “Surface and Analytical Chemistry of Materials” with San Jose State University, involves undergraduate and graduate (masters) San Jose State University students during the academic year who work on collaborative research projects between IBM scientists and San Jose State University professors. In addition, this project also has a large summer program with undergraduates from across the US and with high school teachers. The impact of the programs on the students, teachers, and institutions will be reviewed, with a special emphasis on the impact on the industrial partner.
Dealing With Variation In Measurements & Processes: Experiments For An Undergraduate Laboratory
Authors: Vanasupa Linda , Smith Heather , Gleixner Stacy , Young Greg , Allen Emily 
Published: April 2011

ABSTRACTBeing able to obtain and analyze quantitative data are an essential components of any undergraduate education in science or engineering. At the most basic level, this begins with characterizing the measurement system using proper statistical techniques. Although most undergraduates in the sciences and engineering are required to take a course in statistics, the knowledge gained in the statistics course does not always find its way into practice. In this paper we will present 4 experimental modules that will enable the student to: 1. Assess the precision of a measurement system; 2. Determine if the system is stable with respect to a number of variables; 3. Quantify the amount of variation that exists within a particular sample; 4. Quantify the amount of variation from sample to sample (i.e., process variation). Our modules were applied to the measurement of silicon dioxide thickness from an oxidation process. However, they generally apply to any process that involves measuring a physical quantity. Assessing these sources of variation in a process form the foundation for more advanced techniques such as process control and experimental design.
Incorporating Information Competence into Classes
Authors: Chen Katherine C. , Adalian Paul T. 
Published: April 2011

ABSTRACTEnabling students to become independent learners is a desirable goal for many educators. However, the task is not always easily addressed with the long lists of concrete, technical objectives that must usually be covered in classes. As a result, information often follows a oneway path from the instructor to the student, and students can develop a reliance on “packaged” knowledge and answers from only teachers and textbooks. In efforts to engage students in the learning process and to encourage the self-directed exploration of knowledge, “information competence” [1] has been incorporated into an upper-level materials course. Using current topics in materials science and engineering, students formulate questions to address specific issues and then locate pertinent information. A variety of resources, such as newspapers, web sites, and scholarly journals, are explored and evaluated. The instructor acts as a facilitator that assists with search strategies and evaluation of the information. Students develop the ability to process and reorganize the information into useful forms (e.g., reports, oral presentations). Providing the tools and instructions to function effectively in this Information Age will hopefully promote lifelong learning in today's students.
A Study of Charge Control and Gate Tunneling in a Ferroelectric-Oxide-Silicon Field Effect Transistor
Authors: Lin Yih-Yin , Zhang Yifei , Singh Jasprit 
Published: April 2011

AbstractIt is known that conventional metal-oxide-silicon field-effect transistor (MOSFET) devices will have gate tunneling related problems at very thin oxide thicknesses (dox ≤ 20 Å). In this paper we discuss the potential of polar and non-polar high-dielectric films for gate tunneling suppression and charge control. We also examine ferroelectric thickness effects in ferroelectricoxide- silicon field effect transistors (MFISFETs). Our formalism is based on a blocking-layer model for the ferroelectric film and a self-consistent solution of the Poisson and Schrodinger equations. We show that the polarization effects of ferroelectrics can allow greater controllability of the silicon interface (mobile) charge density and also the high dielectric constant effectively suppresses gate tunneling probability. In addition, the effects of ferroelectric film thickness are quite important in a MFISFET device and allow a small control of the threshold voltage. Results will be presented for the capacitance-voltage curve, tunneling probability, and leakage currents. As an example, we find for a sheet charge of 1013 cm−2, the gate tunneling probability in a MOS structure is 10−6 (dox = 13 Å), while that in a MFISFET is 10−14 with the same equivalent oxide thickness. Our studies also show that details of the blocking layer model (dead layer thickness, coercive field, and polar charge) can be estimated from C-V measurements.
Effect of Bottom Electrodes on Structural and Electrical Properties of Laser Ablated SrBi2Ta2O9 Thin Films
Authors: Das Rasmi R. , Pérez W. , Bhattacharya P. , Katiyar Ram. S. 
Published: April 2011

AbstractWe have grown SrBi2Ta2O9 (SBT) thin films on various bottom electrodes such as Pt/TiO2/SiO2/Si (Pt) and LaNiO3/Pt/TiO2/SiO2/Si (LNO) substrates. The substrate temperature and oxygen pressure for the SBT film was maintained at 500 °C and 200 mTorr. As-grown films were post-annealed at a temperature of 800 °C. X-ray diffraction studies revealed that as-grown films were amorphous and crystallized to single phase after annealing. The difficulty of obtaining lowest Raman modes of SBT on platinized silicon substrate was overcome by using conducting oxide electrodes. Films grown on platinized silicon showed maximum value of remanent polarization (2Pr ∼ 21.5 μC/cm2) with coercive field (Ec) of ∼ 67 kV/cm. The degradation of ferroelectric properties of the films was observed with the introduction of 50 nm conducting LaNiO3 electrode at the interface of Pt and SBT film, which was attributed to high resistivity of the oxide electrode layers. Leakage current density was studied with the consideration of the Schottky emission model. The barrier height of the films grown on Pt and LNO were estimated to be 1.27 eV and 1.12 eV, respectively. The reduction of barrier height was attributed to the lower work function of the LNO electrode.
Improvement of Surface Crystalline Quality of an Epitaxial (100)ZrN Film as a Bottom Electrode Diffusion Barrier for Ferroelectric Capacitors
Authors: Horita Susumu , Horii Sadayoshi , Toda Takeo 
Published: April 2011

AbstractWe fabricated the double epitaxial layers of Ir on barrier metal ZrN for Pb(ZrxTi1−x)O3 (PZT), using reactive sputtering. In order to remove the surface oxide layer of the ZrN film prior to depositing the Ir film, we used a new treatment method, in which the ZrN film is dipped into a 0.5% buffered HF solution for less than 30 seconds and then immediately dipped into a hydrazine (N2H4) monohydrate solution for 60 seconds. Also, in order to suppress the generation of twin boundaries and to improve crystalline quality, the ZrN film is deposited using a two-step method, which consists of an initial high temperature deposition step at 850s°C followed by a lower temperature step at 600°C. On the ZrN film prepared by these methods, we can obtain a mainly (110)-oriented epitaxial Ir film.
Characterization of (Ba,Sr)RuO3 Films Deposited by Metal-organic Chemical Vapor Deposition
Authors: Choi Duck-Kyun , Kang Joong-Seo , Kim Young-Bae , Hong Duck-Hwa , Kim Hyun-Chul , Kim Sung-Tae , Yoo Cha-Young 
Published: April 2011

AbstractThin film electrodes of the perovskite oxide (Ba,Sr)RuO3 (BSR) were deposited on 4 inch ptype Si wafers by metal organic chemical vapor deposition (MOCVD) for the practical (Ba,Sr)TiO3 (BST) capacitor application using a new single cocktail source. The source materials used for the MOCVD BSR process were Ba(METHD)2, Sr(METHD)2 and Ru(METHD)3 and these were dissolved in n-butyl acetate. The source-feeding rate was precisely controlled by liquid mass flow controllers (LMFC). As-deposited BSR films possessed a (110)-oriented structure, with good uniformity and adherence on bare Si wafer. The phase formation was strongly affected by the oxygen flow rate and the input source rate. As the oxygen flow rate increased, the Ru/(Ba+Sr) composition ratio in the film decreased, while the Ba/(Ba+Sr) ratio was almost independent of the oxygen flow rate. The dielectric constants of BST capacitors fabricated using these electrodes was greater than 500.
Origin of Lowered Crystallization Temperature in SBT-BTT Ferroelectric Thin Films
Authors: Kwak Woo-Chul , Kumar Gopinathan M. A. , Jung Se-Yon , Hwang Seung-Joon , Sung Yun-Mo 
Published: April 2011

AbstractThe crystallization kinetics of SBT and SBT-BTT thin films formed by sol-gel technique on Pt substrate was studied. Phase formation and crystal growth are greatly affected by the film composition and crystallization temperature. Isothermal kinetics analysis was performed on x-ray diffraction (XRD) patterns of the thin films heated in the range 730 to 760° at 10° intervals. Activation energy and Avrami exponent values were determined for the fluorite to Aurivillus phase formation. A reduction of ∼55 kJ/mol in activation is observed for the SBT-BTT system. A comparison has been made and the possible crystallization mechanism is discussed.
Functional Behaviour of Thin Film Dielectric Superlattices
Authors: Gregg J. M. , Corbett M. H. , O'Neill D. , Catalan G. , Bowman R. M. 
Published: April 2011

AbstractPulsed laser deposition has been used to fabricate thin-film capacitor structures in which the dielectric layer is a superlattice. The properties of two superlattice systems were investigated as a function of superlattice wavelength (δ) – one based on barium strontium titanate and the other on lead-based relaxor electroceramics. In both systems the dielectric constant was significantly enhanced at stacking wavelengths of a few unit cells. However, the dielectric enhancement seen in the barium strontium titanate superlattices was found to be due to Maxwell-Wagner effects, whereas in the relaxor superlattices Maxwell-Wagner behaviour was not evident; rather, the dielectric enhancement was associated with the onset of polar coupling aroundδ ∼ 10nm.
Compositional Disorder Induced Relaxor Behavior of (PbLa)TiO3 Thin Films
Authors: Bhaskar S. , Majumder S. B. , Katiyar R. S. 
Published: April 2011

AbstractTemperature dependent dielectric behavior of sol-gel derived ferroelectric Pb1−xLaxTiO3 (PLT) (x = 0.05 to 0.30) thin films on Pt/Si substrates has been studied. The characteristics of the diffuse phase transition and possible relaxor behavior of PbTiO3 thin films doped with different amounts of La are investigated. Room temperature X-ray and micro Raman results indicate that the crystal structure of the PLT films was strongly influenced by the La content. The softening of the E(1TO) mode with increasing La content indicates that the incorporation of La in the PT lattice results in a structural disorder in the material. The dielectric permittivity and loss tangent of the PLT thin films were measured in the temperature range of 80 –700 K at frequencies between 1 kHz and 1 MHz. Transition temperatures (Tm) for PLT (x = 0.05, 0.20, and 0.30) are 640, 460, and 254 K respectively, and are higher in comparison to reported values of bulk ceramics. The permittivity maximum broadened, and showed relaxor- type frequency dependent permittivity characteristics for PLT (x = 0.30) films. The broadening parameter was significantly influenced by La doping and our results indicate that PLT thin films undergo a normal-to-relaxor ferroelectric transformation for La concentrations of 25 at% in PLT films.
Initial Growth Stages of Epitaxial BaTiO3 Films on Vicinal SrTiO3:Nb (001) Substrates
Authors: Visinoiu A. , Alexe M. , Lee H. N. , Zakharov D. N. , Pignolet A. , Hesse D. , Gösele U. 
Published: April 2011

AbstractThe growth mechanism of epitaxial BaTiO3 films on vicinal Nb-doped SrTiO3 (SrTiO3:Nb) (001) substrate surfaces was studied in terms of surface morphology, crystalline orientation, microstructure, and film/substrate interface. Well-oriented BaTiO3 thin films were grown on SrTiO3 substrates with well-defined terraces by pulsed laser deposition. The regularly terraced TiO2-terminated surfaces of vicinal SrTiO3:Nb (001) substrates were prepared by a definite chemical and thermal treatment. Under our conditions, BaTiO3 seems to grow with a layer-then-island (Stranski-Krastanov) growth mechanism. In order to investigate the orientation and crystallinity of the BaTiO3 films, x-ray diffraction and high-resolution transmission electron microscopy were performed. Ferroelectricity of the BaTiO3 films was proved by electrical measurements performed on Pt/BaTiO3/SrTiO3:Nb heterostructures.
Monopolar Spin Orientation and Determination of Spin Relaxation Times in Quantum Well Structures
Authors: Ganichev Sergey D. , Danilov Sergey N. , Sollinger Martin , Weiss Dieter , Wegscheider Werner , Prettl Wilhelm , Bel'kov Vasily V. , Ivchenko Eugenius L. 
Published: April 2011

ABSTRACTIt is shown that monopolar optical spin orientation of free carriers in zinc-blende structure based quantum wells (QWs) causes an electric current which reverses its direction upon changing the helicity of the radiation from left to right circular polarization resulting in a circular photogalvanic effect. The monopolar non-equilibrium population of spin-up and spin-down states has been achieved by far-infrared optical excitation ofp- andn-type GaAs/AlGaAs QWs structures. Two methods are introduced allowing to determine spin relaxation times. One is based on the Hanle effect in magnetic field induced circular photogalvanic effect, the other is spin sensitive bleaching of absorption. In contrast to usually applied methods of optical spin orientation, in the present case of terahertz excitation only one kind of charge carriers is involved in spin orientation and relaxation processes.
Interdiffusion in Exchange Biased NiFe/IrMn/CoFe Electrode in Magnetic Tunnel Junctions
Authors: Lee Jay H. , Jeong Hee D. , Rho Il C. , Yoon Chong S. , Kim Chang K. 
Published: April 2011

ABSTRACTExtent of Mn diffusion to the plasma-oxidized AlOx tunnel barrier of magnetic tunnel junction was examined using Auger Electron Spectroscopy (AES) and X-Ray Photoelectron Spectroscopy (XPS). A magnetic film stack consisting of Ta/AlOx/CoFe/IrMn/NiFe/Ta was deposited with the AlOx layer treated under different plasma oxidation durations. AES depth profiles showed that Mn diffusion to the AlOx/CoFe interface increased with increasing oxidation after annealing at 300°C. XPS analysis indicated that Mn found at the CoFe/AlOx interface in the over-oxidized electrode was in the form of MnO2. Our research suggests that Mn diffusion was accelerated by preferential oxidation of Mn at the CoFe/AlOx interface.
Phase Separation at Interfaces in La2/3Ca1/3MnO3 Thin Films
Authors: Fontcuberta J. , Bibes M. , Wojcik M. , Jedryka E. , Nadolski S. , València S. , Balcells Ll. , Martínez B. 
Published: April 2011

ABSTRACTWe present an extensive physical characterization of La2/3Ca1/3MnO3 (LCMO) epitaxial films grown on SrTiO3 (STO), LaAlO3 (LAO) and NdGaO3 (NGO) substrates. The main difference among these substrates is that they have a different mismatch (∼ 1.2%, -1.8% and - 0.1%, respectively) with the manganite. The films can be coherently grown up to 180 nm for STO and NGO but partial relaxation is observed for LAO. The magnetotransport data indicate that very thin films (<27nm) display non-conventional magnetoresistive properties: a substantial magnetoresistance develops which can be progressively appreciated for STO and LAO films. 55Mn-Nuclear Magnetic Resonance experiments on all these films reveal the presence of non-homogeneous electronic states. These experiments in fact provide clear evidence of the presence of two distinguishable ferromagnetic Mn states and a non-ferromagnetic phase. The possible role of strain-induced charge localization is discussed. It turns out that electronic phase separation occurs in all films irrespectively of the particular substrate used; thus we conclude that strain is not the unique driving force for charge localization.
Spin-Valve Effect in Magnetic Resonant Tunneling Devices
Authors: Chantis A. N. , Demchenko D. O. , Petukhov A. G. 
Published: April 2011

ABSTRACTWe propose a new electronic device utilizing resonant tunneling between two magnetic materials. The device is comprised of a semiconductor quantum well sandwiched between two insulating barriers and two ferromagnetic electrodes. The situation in which a resonant level fits in the energy interval where the minority density of states of a ferromagnetic emitter is zero can be considered as an almost ideal spin valve and leads to a great enhancement of magnetoresistance. This situation can be achieved by tuning the width of the quantum well. As an example we will consider GaMnAs/AlAs/GaAs/AlAs/GaMnAs double-barrier heterostructure. We can demonstrate that at a certain thickness of the quantum well and the barriers this system can significantly outperform conventional tunneling junctions comprised of one insulating barrier sandwiched between two ferromagnetic electrodes.
Gas Source MBE Growth and Characterization of TlInGaAs/InP DH Structures for Temperature-independent Wavelength LD Application
Authors: Asahi Hajime , Lee Hwe-Jae , Mizobata Akiko , Konishi Kenta , Maeda Osamu , Asami Kumiko 
Published: April 2011

AbstractTlInGaAs/InP double-hetero (DH) structures were grown on (100) InP substrates by gas source MBE. The photoluminescence (PL) peak energy variation with temperature decreased with increasing Tl composition. For the DH with a Tl composition of 13%, the PL peak energy varied only slightly with temperature (−0.03 meV/K). This value corresponds to a wavelength variation of 0.04 nm/K and is much smaller than that of the lasing wavelength of InGaAsP/InP distributed feedback laser diodes (0.1 nm/K). TlInGaAs/InP light emitting diodes with 6% Tl composition were fabricated and the small temperature variation of the electroluminescence peak energy (−0.09 meV/K) was observed at the wavelength around 1.58 μm. The results are promising to realize the temperature-independent wavelength laser diodes, which are important in the wavelength division multiplexing (WDM) optical fiber communication systems.
Luminescent Characteristics of InGaAsP/InP Multiple Quantum Well Structures by Impurity-Free Vacancy Disordering
Authors: Zhao J. , Zhang X. D. , Feng Z. C. , Deng J. C. , Jin P. , Wang Y. C. , Xu G. 
Published: April 2011

AbstractInGaAsP/InP multiple quantum wells have been prepared by Impurity-Free Vacancy Disordering (IFVD). The luminescent characteristics was investigated using photoluminescence (PL) and photoreflectance (PR), from which the band gap blue shift was observed. Si3N4, SiO2 and SOG were used for the dielectric layer to create the vacancies. All samples were annealed by rapid thermal anne aling (RTA). The results indicate that the band gap blue shift varies with the dielectric layers and annealing temperature. The SiO2 capping was successfully used with an InGaAs cladding layer to cause larger band tuning effect in the InGaAs/InP MQWs than the Si3N4 capping with an InGaAs cladding layer. On the other hand, samples with the Si3N4-InP cap layer combination also show larger energy shifts than that with SiO2-InP cap layer combination.
Airplane and Drop Experiments on Crystallization of InxGa1−xSb Semiconductor under Different Gravity Conditions
Authors: Balakrishnan Krishnan , Hayakawa Yasuhiro , Komatsu Hideki , Murakami Noriaki , Nakamura Tetsuo , Kimura Tadashi , Ozawa Tetsuo , Okano Yasunori , Miyazawa Masafumi , Dost Sadik , Dao Le. H. , Kumagawa Masashi 
Published: April 2011

AbstractMelting and crystallization experiments of InGaSb were done under the reduced gravity condition (10−2G) in an airplane and at the normal gravity condition (1G) in the laboratory. Crystallized InGaSb was found to contain many needle crystals in both the cases. Reduced gravity condition was found to be more conducive for crystal growth than the normal gravity condition. Formation of spherical projections on the surface of InGaSb during its crystallization was in-situ observed using a high speed CCD camera in the drop experiment. Spherical projections showed dependence of gravity during its growth. Indium compositions in the spherical projections were found to vary depending on the temperature.
InP Self Assembled Quantum Dot Lasers Grown on GaAs Substrates by Metalorganic Chemical Vapor Deposition
Authors: Dupuis R. D. , Ryou J. H. , Heller R. D. , Walter G. , Kellogg D. A. , Holonyak N. , Reddy C. V. , Narayanamurti V. , Mathes D. T. , Hull R. 
Published: April 2011

AbstractWe describe the operation of lasers having active regions composed of InP selfassembled quantum dots embedded in In0.5Al0.3Ga0.2P grown on GaAs (100) substrates by MOCVD. InP quantum dots grown on In0.5Al0.3Ga0.2P have a high density on the order of about 1–2×10 cm−2 with a dominant size of about 10–15 nm for 7.5 ML growth.[1] These In0.5Al0.3Ga0.2P/InP quantum dots have previously been characterized by atomic-force microscopy, high-resolution transmission electron microscopy, and photoluminescence.[2] We report here the 300K operation of optically pumped red-emitting quantum dots using both double quantum-dot active regions and quantum-dot coupled with InGaP quantum-well active regions. Optically and electrically pumped 300K lasers have been obtained using this active region design; these lasers show improved operation compared to the lasers having QD-based active regions with threshold current densities as low as Jth ∼ 0.5 KA/cm2.