bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of PZT Film Stress in Multilayer Structures for MEMS Devices
Authors: Zakar E. , Dubey M. , Polcawich R. , Piekarski B. , Piekarz R. , Conrad J. , Widuta R. 
Published: April 2011

AbstractResidual stress in the multilayer Si/Dielectric/Pt/PZT/Pt stack was measured as a function of annealing conditions, sol-gel derived PZT (Lead Zirconate Titanate -52/48) thickness, SiO2and/or Si3N4dielectric films thickness. Residual stress in the Si3N4layer varied from -201 to +1275 MPa and from -430 to + 511 MPa in the Si02layer. Furnace annealing of the bottom Pt film reduced the stress over rapid thermal annealing (RTA). Stress due to PZT films was the controlling factor for the final stress of the stack. Upon increasing PZT thickness, stress became less tensile for Si3N4dielectric and more tensile for Si02. The deposition of the top Pt on PZT followed by RTA at 300°C in nitrogen had a minimal effect on the final stress of the stack. The average tensile stress for the Si/Si02/Pt/PZT/Pt and Si/Si3N4/Pt/PZT/Pt stacks was 140 ± 25 and 476±235 MPa respectively.
Roughness Characterization of Si(110) Etched in TMAH by Atomic Force Microscopy
Authors: Moktadir Z. , Sato K. , Matsumuro A. , Kayukawa K. , Shikida M. 
Published: April 2011

AbstractWe have investigated the roughness of a silicon (110)-oriented surface after being etched with 20% TMAH (Tetra-methyl Ammonium Hydroxide). We have used an Atomic Force Microscope to determine the roughness exponent α using three different methods: fractal, power spectrum density and scaling analysis. The value of the parameter α was identified to be close to 1/2. This value is different from the KPZ value, which is 0.4 in 2+1 dimension
New Materials and New Processes for MEMS Applications
Authors: Schweitz J.-Å. , Larsson K. , Thornell G. , Björkman H. , Nikolajeff F. 
Published: April 2011

AbstractThe field of “non-silicon MEMS” is today rapidly expanding. The reasons are numerous: silicon has a limited functionality in many MEMS applications; the toolbox for micromaching of non-silicon materials is steadily growing in size and versatility; the price level of a variety of other advanced materials for MEMS has become more competitive etc. This development is here illustrated by a number of examples from a wide variety of materials classes, methods for synthesis and microprocessing, and fields of application. Among these examples are high-aspect ratio processing of different materials by ion track technology (MITE) and deep ion projection lithography (DIPL); laser microprocessing and free-space 3D laser writing; high-precision 3D diamond replicas from microstructured silicon masters; and microreplication in polymeric materials for microoptics and microsystems technology.
New Approaches to Chemical Bath Deposition of Chalcogenides
Authors: O’brien Paul , Heinrich Markus R. , Otway David J. , Robbe Odile , Bayer Alexander , Boyle David S. 
Published: April 2011

AbstractWe have been studying new approaches to conventional Chemical Bath Deposition (CBD) of chalcogenide containing materials, using continuous circulation and replenishment of CBD solution over a heated substrate. Crystalline thin films produced by this method offer potential for use in solar cell devices or other optoelectronic applications. Films of CdS, ZnS and the ternary material CdxZn1−xS have been deposited on TO-glass substrates. In this paper we demonstrate our approach for the deposition of CdS films. These have been characterized by XPS, SEM, XRD and UV/vis spectroscopy and shown to be good quality. The films have been used to fabricate Au/CdTe/CdS/TO-glass solar cells of efficiency 10.1% under AMl.5 illumination.
Fabrication of Crack-Free La0.2Sr0.8CoO3−x Membranes on Asymmetric and Porous Ceramic Supports—Effects of a Metallic Covering
Authors: Cao Z-D. , Hong L. , Chen X. 
Published: April 2011

AbstractCrack-free La0.2Sr0.8CoO3−x (LSCO) membranes have been fabricated on porous ceramic supports such as MgO and CeO2 through dip coating and sintering. To avoid cracks in a LSCO membrane during sintering, a silver coating on top of the LSCO powder-packed layer that is formed via dip coating was found successful. The cracks would be otherwise unavoidable due to the shrinkage mismatch between the membrane and the support during sintering. The silver can be readily removed from the sintered LSCO membrane chemically without causing damages in the membrane.
Group IVB Oxides as High Permittivity Gate Insulators
Authors: Campbell S. A. , He B. , Smith R. , Ma T. , Hoilien N. , Taylor C. , Gladfelter W. L. 
Published: April 2011

AbstractIncreasing MOSFET performance requires scaling, the systematic reduction in device dimensions. Tunneling leakage, however, provides an absolute scaling limit for SiO2of about 1.5 nm. Power limitations and device reliability are likely to pose softer limits slightly above 2 nm. We have investigated the use of high permittivity materials such as TiO2, ZrO2, and their silicates as potential replacements for SiO2. We have synthesized titanium nitrate (Ti(NO3)4or TN), zirconium nitrate (Zr(NO3)4or ZrN), and hafnium nitrate (Hf(NO3)4or HfN) as hydrogen and carbon free deposition precursors. Several problems arise in the use of these films including the formation of an amorphous low permittivity interfacial layer. For TiO2this layer is formed by silicon up diffusion. Surface nitridation retards the formation of the interfacial layer. We discuss the effects of both thermal and remote plasma surface nitridation treatments on the properties of the film stack. ZrO2and HfO2appear to form a thermal layer of silicon oxide between the high permittivity film and the silicon and have excess oxygen in the bulk of the film.
Chemical Synthesis of Pure and Doped LaGaO3 Powders of Oxide Fuel Cells by Amorphous Citrate/EG Method
Authors: Tas A.C. , Schluckwerder H. , Majewski P. , Aldinger F. 
Published: April 2011

AbstractPowders of LaGaO3, La0.9Sr0.1GaO2.95 and La0.8Sr0.2Ga0.83Mg0.17O2.815 were prepared by the amorphous citrate/EG method. The calcination behavior of the precursor powders of the above phases were studied in the temperature range of 200°-1400°C, in an air atmosphere. Characterization of the samples were performed by XRD, TG/DTA, FTLR, SEM, ICP-AES, and carbon and nitrogen analyses.
A Study of the Oxygen Surface Exchange Coefficient on La0.5Sr0.5CoO3−δ Thin Films
Authors: Chen X. , Wang S. , Yang Y.L. , Smith L. , Wu N.J. , Jacobson A.J. , Ignatiev A. 
Published: April 2011

AbstractLa0.5Sr0.5CoO3−δ (LSCO) can be used as a cathode material for low temperature solid oxide fuel cell applications. LSCO epitaxial thin films have been deposited on LaAlO3 substrates by pulsed laser deposition (PLD). The transient behavior of the thin film conductivity with the pressure changes was recorded as a function of temperature and partial oxygen pressure. The surface exchange coefficient k of the LSCO thin film was obtained from analysis of the electrical conductivity relaxation data. The measured surface exchange coefficient increases with temperature and with final pressure but is not sensitive to the initial pressure. After prolonged annealing at 900°C, the k value was found to have greatly increased. The mechanism of the dependence of the measured k on pressure is discussed.
Low Temperature Chemical Vapor Deposition of Titanium Nitride Thin Films With Hydrazine and Tetrakis-(dimethylamide)Titanium
Authors: Amato-Wierda Carmela , Norton Edward T. , Wierda Derk A. 
Published: April 2011

AbstractHydrazine and tetrakis-(dimethylamido)titanium have been used as precursors for the low temperature chemical vapor deposition of TiN thin films between 50°C and 200°C at growth rates between 5 to 35 nm/min. At hydrazine to TDMAT ratios of 50:1 and 100:1 the resulting films show an increase in the Ti:N ratio with increasing deposition temperature. They contain 2% carbon, and varying amounts of oxygen up to 36% as a result of diffusion after air exposure. The low temperature growth is improved when hydrazine-ammonia mixtures containing as little as 1.9% hydrazine are used. Their Ti:N ratio is almost 1:1 and they contain no carbon or oxygen according to RBS. The TiN films grown from pure hydrazine or the hydrazine-ammonia mixture have some crystallinity according to x-ray diffraction and their resistivity is on the order of 104µω cm. The low temperature growth is attributed to the weak N–N bond in hydrazine and its strong reducing ability. In these films, the Ti:N ratio is approximately 1:1.
Electronic Bandgap and Refractive Index Dispersion of Single Crystalline Epitaxial ZnGeN2
Authors: Zhu L.D. , Norris P.E. , Bouthillette L.O. 
Published: April 2011

AbstractThe electronic band gap of single crystalline ZnGeN2 epitaxial layer grown on sapphire substrate by metal organic chemical vapor deposition has been measured by optical transmission and room temperature photoluminescence. The band gap energy is 2.99eV at room temperature, and the band gap is a direct transition type. The interference oscillations of the transmission spectra together with rutile prism coupling measurements have been used to determine the r fractive index and the dispersion characteristics of the single crystal ZnGeN2 below the band gap energy. The rutile prism coupling measurement displays the wave guide modes of the film at 6 2.8nm wavelength of the He-Ne laser, enabling determination of the film thickness and refractive index precisely at the wavelength. The refractive index of ZnGeN2 crystal is 2.35 at 6328Å wavelength. The measured refractive index dispersion curve can be fitted with the first-order Sellmeier equation n2(λ) = A + λ2/(λ2-B), using fitting parameters A=4.3 1, B=0.076.
Impurity-Induced Defect States in Pb1−xGexTe Alloys Doped With Gallium
Authors: Skipetrov E.P. , Zvereva E.A. , Belousov V.V. , Skipetrova L.A. 
Published: April 2011

AbstractGalvanomagnetic properties of n-Pb1−xGexTe<Ga>(O.04≤x≤O.08) single crystals have been investigated in the shielded from external background illumination chamber and under controlled illumination from infrared heat source. Low temperature activation range of the impurity conductivity on the dark curves of ρ(l/T) was revealed and attributed to the appearance of gallium-induced deep level EGa in the gap of the alloys. It was shown that the alloys possess high infrared photosensitivity at temperatures below Tc=50%60 K, and effect of the persistent photoconductivity at helium temperatures was revealed.
Anisotropy of Optical and Electron Transport Properties of Atomic Ordering in CdGeAs2
Authors: Bairamov B. H. , Fernelius N. , Irmer G. , Monecke J. , Polushina I. K. , Pandey R. , Rud' V.Yu. , Rud Yu. V. , Schunemann P.G. , Ohmer M.C. 
Published: April 2011

AbstractInelastic light scattering by optical phonons and the temperature dependent electrical conductivity, Hall constant and photosensitivity were studied in oriented CdGeAs2 crystals grown by ultra-low gradient freeze technique from near-stoichiometric melts. Observation of the clear polarization dependence of the inelastic light scattering spectra by optical phonons combined with the absence of any dependence of the intensity and frequency shift of the observed lines with mapping measurements in 300 μm steps indicated the high optical quality and homogeneity of these single crystals. It is shown that surface-barrier structures using these single crystals may be used as wide-band detectors for natural light, as well as selective photoanalyzers for linearly polarized radiation.
Thermal Admittance Studies of Electron-Irradiated CdGeAs2
Authors: Smith S.R. , Evwaraye A.O. , Ohmer M.C. , Drevinsky P. J. , Bliss D. F. 
Published: April 2011

AbstractBrudnyi, et al., and Zwieback, et al., have shown that introducing damage by irradiation with MeV electrons can alter the electrical and optical properties of undoped p-type CdGeAs2(CGA) crystals. Brudnyi's studies of the electrical transport properties of isochronally annealed samples demonstrated type conversion and identified at least two new centers, one a stable donor. Zwieback used multi-MeV electrons to introduce compensating donors, thereby, significantly improving the optical transparency of CGA crystals. However, at the present little is known about these centers. Therefore, we have studied these centers by observing the properties of electron-irradiated specimens using Thermal Admittance Spectroscopy (TAS) and correlated the results of these measurements with capacitance-voltage measurements and Hall effect measurements. Measurements before an after irradiation are compared. The as-grown native acceptor concentrations in our samples varied from a low in the mid 1016 cm−3to nearly 1019 cm−3. Significant changes in the electrically active states in the band gap were seen as a result of a single irradiation with 2 MeV electrons to a total dose of 5 × 105cm−2. The samples appear to respond more strongly than Brudnyi's samples. The thermal activation energies have been determined using TAS and they will be reported.
Photoluminescence Measurements in Interband Transition in Fast Neutron Irradiated In0.07Ga0.93As/A10.4Ga0.6 As Multiple Quantum Wells
Authors: Manasreh M. O. , Subramanian S. 
Published: April 2011

AbstractInterband transitions in n-type InGaAs/AlGaAs multiple quantum wells were studied using a photoluminescence (PL) technique after the samples were irradiated with fast neutrons. It was observed that the PL intensity of the interband transition is reduced as the irradiation dose is increased. In Addition, the peak position energy of the interband transition was increased and then decreased as a function of irradiation dose. The results are explained in terms of electrons trapping, many-body effects, and irradiation-induced damages at the interfaces as well as in the well and barrier regions.
High-Temperature W Diode Lasers Emitting at 3.3µm
Authors: Olafsen L. J. , Bewley W. W. , Vurgaftman I. , Felix C. L. , Aifer E. H. , Stokes D. W. , Meyer J. R. , Lee H. , Menna R. J. , Martinelli R. U. , Garbuzov D. Z. , Maiorov M. , Connolly J. C. , Sugg A. R. , Olsen G. H. 
Published: April 2011

AbstractW lasers based on type-II antimonides were recently operated nearly to room temperature under the conditions of cw optical pumping. However, the development of electrically pumped mid-infrared lasers has not yet reached the same level of performance. This is largely related to the more challenging task of simultaneously optimizing the doping/transport and gain/optical properties of the devices. Here we report a demonstration of type-II mid-IR diode lasers employing W active quantum wells. Laser structures with 5 or 10 active periods sandwiched between broadened-waveguide separate confinement regions and quaternary optical cladding layers were processed into 100-µm-wide stripes, cleaved into 1-mm-long cavities, and mounted junction side down. For 0.5-1 µs pulses at a repetition rate of 200 Hz, lasing was obtained up to a maximum operating temperature of 310 K, where the emission wavelength was 3.27 µm. The threshold current densities were 110 A/cm2and 25 kA/cm2 at 78 and 310 K, respectively. The characteristic temperature, To, was 48 K for temperatures between 100 and 280 K. Operation in cw mode was obtained to 195 K, with threshold current densities of 63 A/cm2and 1.4 kA/cm2at 78 and 195 K, respectively, with To = 38 K between 78 and 195 K. Significant further improvements in the operating characteristics are expected once the optimization of the designs and fabrication procedures is complete.
Self-interstitials have never been observed in crystalline Si. How about amorphous Si?
Authors: Roorda Sjoerd 
Published: April 2011

ABSTRACTIn the early days of point defect studies in electron irradiated crystalline silicon, it was surmised that the Si self-interstitial is highly mobile even at 4 K and escapes direct detection. The existence of self-interstitials has of course been confirmed through the diffusion behaviour of a range of impurities and the direct observation of larger interstitial-type clusters. Against this background, the direct observation of self-interstitials in amorphous Si would seem next to impossible. Yet just such an observation may have been made recently, through a comparison of the high-resolution radial distribution function of pure amorphous Si before and after thermal anneal and that of crystalline Si.
Doping of amorphous and microcrystalline silicon films by hot-wire CVD and RFPECVD at low substrate temperatures on plastic substrates
Authors: Alpuim P. , Chu V. , Conde J.P. 
Published: April 2011

ABSTRACTDeposition of n and p-type amorphous (a-Si:H) and microcrystalline (µc-Si:H) silicon thin films on polyethylene terephthalate (PET) at substrate temperatures (Tsub) of 100°C and 25°C (RT) prepared by hot-wire (HW) chemical vapor deposition and radio-frequency (RF) plasma-enhanced chemical vapor deposition is studied as a function of hydrogen dilution. Doping is achieved by addition of phosphine (ntype) and diborane (p-type) to the gas phase reactive mixture. At Tsub=100°C, n-type a-Si:H is obtained by HW with dark conductivity σd10−4 ω−1cm−1 and by RF with σd~10−3 ω−1cm−1. P-type a-Si:H is obtained by HW with σd=8×10−7 ω−1cm−1 and by RF with σd=6×10−7 ω−1cm−1. Decreasing the temperature of deposition to 25°C decreases the sd of RF n-type amorphous samples to 5×10−5 ω−1cm−1 but the σd of p-type samples remains unchanged. RT HW a-Si:H films show a decrease of sd both for ntype film (σd=4×10−6 ω−1cm−1) and p-type film (σd=1.2×10−7 ω−1cm−1). N-type µc-Si:H was obtained by HW with σd=7×10−2 ω−1cm−1 and by RF with σd>10−2 ω−1cm−1 at 100°C. Using the same Tsub, p-type µc-Si:H was deposited by HW and by RF with σd~0.5 ω−1cm−1. At RT, only p-type µc-Si:H films could be prepared using HW (σd~1 ω−1cm−1) and RF (σd=4×10−3 ω−1cm−1). The structural properties of the films were studied using Raman spectroscopy. The structural and transport properties were correlated.
Electroreflectance Study of Light-Emitting Porous Silicon
Authors: Toyama Toshihiko , Shimode Akihito , Okamoto Hiroaki 
Published: April 2011

ABSTRACTElectroreflectance spectroscopy measurements have been performed on light-emitting porous Si (LEPSi). The transmission electron microscope measurements reveal that LEPSi includes Si nanocrystals with a mean crystal size of 1–2 nm. The ER features are observed at a transition energy of 3.4 eV in all of the samples, giving that LEPSi still keeps the threedimensional (3D) electronic structure. Changes in the transition energies are not found for LEPSi with the different mean crystal sizes. Furthermore, we directly observed interband transitions of quantized states due to quantum-confined electron-hole (e-h) pairs in LEPSi as two or three extra ER features being located between 1.2 and 3.1 eV which are never observed in bulk crystalline Si. Employing a simple effective mass approximation model, we have evaluated the reduced mass, the kinetic energies and the Coulomb attraction energies of the quantumconfined e-h pairs. We also found that the energy distance between the transition energies at the ground state and the photoluminescence (PL) peak energies basically corresponds to the Coulomb attraction energies. Finally, we propose a new luminescent model based on interband transitions involving the quantum-confined dense e-h plasma.
Temperature Dependent Transport in Microcrystalline PIN Diodes
Authors: Brammer T. , Stiebig H. , Lambertz A. , Reetz W. , Wagner H. 
Published: April 2011

ABSTRACTThe optoelectronic behavior of diodes deposited by plasma enhanced chemical vapor deposition was investigated for a series of different silane concentrations in the gas phase. The purpose of this work was to correlate device characteristics with inherent properties of microcrystalline silicon by experiments and numerical simulations. Dark diode characteristics and, therefore, the open circuit voltage behavior of this series were dominated by the bulk properties of the i-layer (equilibrium carrier concentration) as shown by numerical modeling. Measurement of the solar cell output parameters as a function of the temperature showed that the fill factor of solar cells with small silane concentrations is dominated by the dark diode characteristics. This is in contrast to the temperature dependent fill factor of solar cells with large silane concentration which is limited by the extraction efficiency of the photogenerated carriers. Interface effects dominated the temperature dependent blue response. The gain in blue response increased with temperature and silane concentration by up to 200 % which revealed transport limiting material properties in the vicinity of the p/i-interface. This behavior was attributed to the nucleation region.
Microstructural Control Of Thin Film Si Using Low Energy, High Flux Ions In Reactive Magnetron Sputter Deposition
Authors: Gerbi Jennifer E. , Abelson John R. 
Published: April 2011

ABSTRACTUsing plasma growth sources with concurrent particle bombardment, silicon thin films can be deposited with various phases and microstructures. DC Reactive Magnetron Sputtering (RMS), in particular, can produce amorphous, mixed-phase, nanocrystalline, polycrystalline, porous columnar, and epitaxial Si films. In particular, a large flux of low energy, heavy ions strongly affects the phase and microstructure, and therefore the resulting film qualities. Lowpressure (1.6 mTorr) RMS is particularly suited for this type of plasma manipulation: we bias the substrate to produce the ion energy of choice, and use an external magnetic field to control the ion/neutral flux ratio, therefore decoupling the parameters of bombardment energy and flux. In this work, we study the influence of slow (<40eV), heavy (Ar+), ions in RMS deposition on the formation kinetics and microstructures of microcrystalline, mixed-phase, and poly crystalline Si films. The analytical methods are ellipsometry, Raman scattering, and AFM. We will show how ion bombardment influences the direct nucleation of extremely smooth polycrystalline Si on glass at temperatures below 400°C, enhances the crystallinity of this polycrystalline Si in the bulk, and produces nanocrystalline Si with tailored grain sizes at temperatures below 200°C.
Comparison of Structural Properties and Solar Cell Performance of a-Si:H Films Prepared at Various Deposition Rates using 13.56 and 70 MHz PECVD Methods
Authors: Jones S.J. , Williamson D.L. , Liu T. , Deng X. , Izu M. 
Published: April 2011

ABSTRACTThe advantage of using very high frequencies for preparation of a-Si:H materials at high rates (above 5 Å/s) for intrinsic layers (i-layer) of solar cells has been well documented. In an effort to identify film properties which may be related to this superior device performance, a study of the structural, optical and electrical properties of films made at various deposition rates between 1 and 15 Å/s using rf frequencies of 13.56 and 70 MHz has been made. The films were characterized using a number of techniques including small-angle x-ray scattering, infrared absorption spectroscopy, and scanning electron microscopy. For the films made using the 70 MHz frequency, the amount of nanovoids with sizes of < 100Å increases systematically as the deposition rates increases beyond 5 Å/s. Accompanying the increase in void fraction in the films are increases in the hydrogen content and the amount of 2070 cm-1 mode in the infrared absorption spectra. In addition to an increase in the amount of nanovoids in the films as the deposition rate exceeds 5 Å/s, the films made using the 13.56 MHz and high deposition rates have large amounts of SAXS related to scattering features with sizes > 200 Å. This scattering is associated with large bulk density fluctuations and/or enhanced surface roughness. None of the films in the study displayed signs of having columnar-like microstructures. The nanovoids are not related to changes in the solar cells with increasing i-layer deposition rate for both fabrication processes, perhaps due to the relatively small volume fractions of less than 0.2% and/or good void-surface passivation. However, the larger-scale structures detected in the films made using the 13.56 MHz technique could cause poorer performance in cells prepared at high growth rates.