bluuebunny/crossref_metadata_2025 huggingface dataset:
Cleaning Technologies using Electrolytic Ionized Water and
Analysis Technology of Fine Structures for Next Generation Device
Manufacturing
Authors: Aoki Hidemitsu , Yamasaki Shinya , Nakamori Masaharu , Aoto Nahomi , Yamanaka Koji , Imaoka Takashi , Futatsuki Takashi
Published: April 2011

To reduce the consumption of chemicals and ultra pure water (UPW) in
cleaning processes used in device manufacturing, we have developed wet
processes that use electrolytic ionized water (EIW), which is generated by
the electrolysis of a diluted electrolyte solution or UPW. EIW can be
controlled for wide ranges of pH and oxidation-reduction potential. Anode
EIW with diluted electrolyte, which has high oxidation potential, can remove
metallic contamination such as Cu and Fe on Si surfaces. EIW contains less
than 1/100 of the amount of chemicals contained in conventional cleaning
solutions, thus drastically reduces chemical consumption in wet processes.
Moreover, electrolyzed UPW can be used as a substitute for conventional UPW
to achieve better rinsing characteristics. Electrolyzed UPW reduces the
level of residual SO42− ions after SPM cleaning more efficiently than conventional
UPW. Thus the amount of rinse water needed is reduce to 1/6 that of the
conventional UPW rinse.

We also developed a method for analyzing remaining metallic contamination
and residual ions in deep-submicron-diameter holes with high aspect ratios.
The method is based on conventional atomic absorption spectrometry (AAS),
and uses device patterns with high density contact holes. With this method,
metallic (Fe) contamination on the order of 1010
atoms/cm2 can be easily analyzed inside 0.1 μm-diameter holes
with an aspect ratio of 10. The residual ions in the fine holes can also be
detected by thermal desorption spectroscopy (TDS).
Low Thermal Conductivity Skutterudites
Authors: Fleurial J.-P. , Caillat T. , Borshchevsky A.
Published: April 2011

Recent experimental results on semiconductors with the skutterudite crystal structure show that these materials possess attractive transport properties and have a good potential for achieving ZT values substantially larger than for state-of-the-art thermoelectric materials. Both n-type and p-type conductivity samples have been obtained, using several preparation techniques. Associated with a low hole effective mass, very high carrier mobilities, low electrical resistivities and moderate Seebeck coefficients are obtained in p-type skutterudites. For a comparable doping level, the carrier mobilities of n-type samples are about an order of magnitude lower than the values achieved on p-type samples. However, the much larger electron effective masses and Seebeck coefficients make n-type skutterudites promising candidates as well. Unfortunately, the thermal conductivities of the binary skutterudite compounds are too large, particularly at low temperatures, to be useful for thermoelectric applications.

Several approaches to the reduction of the lattice thermal conductivity in skutterudites are being pursued: heavy doping, formation of solid solutions and alloys, study of novel ternary and filled skutterudite compounds. All those approaches have already resulted in skutterudite compositions with substantially lower thermal conductivity values in these materials. Recently, superior thermoelectric properties in the moderate to high temperature range were achieved for compositions combining alloying and “filling” of the skutterudite structure. Experimental results and mechanisms responsible for low thermal conductivity in skutterudites are discussed.
Materials for Mid-Infrared Semiconductor Lasers
Authors: Kost A. R.
Published: April 2011

A variety of semiconductor materials have been used to fabricate diode lasers for the midinfrared. Lasers using the lead salts (e.g. PbSnTe) have been commercially available for some time. Mid-infrared emitting III-V semiconductors (e.g. InGaAsSb) have superior thermal conductivity, and diode lasers fabricated from these materials offer higher powers. Of particular interest are the III-V semiconductor lasers based on type-II superlattices (e.g. InAs/GaInSb). Among the many unique properties attributed to type-Il superlattices are small hole mass, reduced Auger recombination, and less inter-valence band absorption - all important for better lasers. Recent results with Quantum Cascade-type lasers are also very encouraging. This paper summarizes the important semiconductor materials for mid-infrared lasers with emphasis on the type-II superlattices.
Raman and Photo-Luminescence Studies on Intrinsic and Cr-Doped Znse Single Crystals
Authors: Rai Brajesh K. , Bhaskar S. , Bist H. D. , Katiyar R. S. , Chen K.-T. , Burger A.
Published: April 2011

Single crystals of ZnSe, with varying amounts of Cr doping have been studied using Raman and photoluminescence(PL) spectroscopy. The Cr-doped samples show the existence of a coupling mechanism of longitudinal optical(LO) phonons of ZnSe with hole-plasmons. The dependence of intensity ratio of LO and transverse optical(TO) mode on temperature and excitation wavelength, has been attributed to the interaction of the field of LO phonons with the surface electric field in the depletion layer. The interaction of discreet phonons with the electronic continuum of conduction band in ZnSe is responsible for the shift of Raman peaks. The large electron capture cross-section of deep-level Cr2+ and Cr1+ impurities is inhibitive for the observation of band-to-band PL transition at ∼2.7eV in ZnSe:Cr.
Extracting Trap Parameters From Picts Spectra In Cadmium Zinc Telluride Radiation Detector Material
Authors: Toney J. E. , Brunett B. A. , Schlesinger T. E. , James R. B.
Published: April 2011

We demonstrate that the regularization method due to Weese can resolve closely-spaced peaks in PICTS spectra for cadmium zinc telluride. We also show that electron and hole traps can be distinguished from each other by the bias dependence of the spectrum when using an excitation source that is primarily infrared but which contains a small component of visible light. Lastly we show that there are qualitative differences between PICTS spectra taken with infrared excitation and those taken with visible excitation. We attribute the surface-related levels to diffusion into the detector material of gold from electroless deposition of contacts.
Simulated and Associated Experimental Results of CdZnTe Radiation Detector Response for Gamma-Ray Imaging Applications
Authors: Verger L. , Bonnefoy J. P. , Gliere A. , Ouvrier-Buffet P. , Rosaz M.
Published: April 2011

Simulated and associated experimental results of a high efficiency CdZnTe (CZT) radiation detector response for gamma-ray imaging applications are presented. The model of a high efficiency semiconductor gamma ray detector takes into account several different physical phenomena involved in the detection and correction processes, namely the geometry of the irradiation, the gamma-ray's interaction with the crystal, the physics of the semiconductor's charge collection, the electric field distribution and the pulse height correction method. A few important decoupling assumptions allow us to use a one dimensional charge collection simulation with a two-dimensional field model and a full three dimensional Monte-Carlo calculation of the gamma ray interactions. The model allows calculation of charge collection and gamma ray spectra for non uniform electric field distribution in either planar, striped or pixellated detector.

The model takes also into account the new CZT fast pulse correction method and its associated noise by considering the pulse height and the rise time of electron signals (Bi-Parametric spectrum) for all gamma ray interactions. Specific simulated and experimental spectra at 122 keV are presented for CZT. First, basic spectral changes are calculated for variations in crystal and detector properties like mobility, trapping lifetime and electric field profiles

Second, new experimental results of the fast pulse correction method applied to different CZT detector grades are presented. This method allows to achieve a high detection efficiency (> 80 %) with a good energy resolution (< 6 % FWHM) at 122 keV for a 4×4×6 mm3 CZT detector. No specific contact geometry is needed and the unusual low applied bias voltage allows to limit the ageing and break voltage effects and also the dark current and its associated noise. This fast correction method is expected to be useful for medical imaging and other applications.

Finally, simulated Bi-Parametric (BP) spectra expected with the fast pulse correction method according to the detector properties (electric field profiles, electron lifetime) are simulated and a qualitative comparison is provided.
High Energy Flux Detector Using CdTe P-I-N Layers
Authors: Niraula Madan , Arakawa Tomonori , Aoki Toru , Nakanishi Yoichiro , Hatanaka Yoshinori , Kan Hirofumi
Published: April 2011

n-and p-type doping of CdTe grown heteroepitaxially on GaAs substrate by radical assisted metal organic chemical vapor deposition technique were studied. n-type doping was studied by the gas phase n-butyliodine doping during the film growth, whereas p-type doping was carried by treating the undoped layers with alkaline metal compound (Na2Te) and excimer laser radiation. Highly conductive n-and p-layers were thus obtained which formed good ohmic contact with aluminum and gold electrodes, respectively. Using this technique, n-and p- layers were formed on intrinsic CdTe substrate to form p-i-n diode. This p-i-n structure showed a good diode characteristics and good sensitivity to X-ray radiation with dark current in the order of nA/mm 2 at room temperature.
Characterization of X-Ray Imaging Properties of PbI2 Films
Authors: Shah K. S. , Bennett P. , Cirignano L. , Dmitriyev Y. , Klugerman M. , Mandal K. , Moy L. P. , Street R. A.
Published: April 2011

This paper describes our recent research in developing vacuum sublimed lead iodide films for X-ray imaging. Lead iodide films are promising for this application due to their low dark current, high stopping efficiency, reasonably good charge transport, low cost, and relatively easy scale-up. Lead iodide films (up to 5 × 5 cm2 area) have been grown and characterized by measuring their X-ray imaging properties such as spatial resolution, and contrast transfer function. Excellent spatial resolution (> 10 lp/mm with high CTF ≈50%) has been recorded with PbI2 films. Relevant detection properties such as signal amplitude for given X-ray energy has also been measured and was found to be about 10 times larger as compared to standard phosphor screens used for X-ray imaging. Charge transport and timing characteristics of these films have been measured and the results indicate that these films should be capable of real-time operation. Application of these films for X-ray imaging such as mammography, fluoroscopy, and X-ray diffraction is addressed.
Calorimetric and Spectroscopic Characterization of Zone Refined and Regrown Lead Lodide
Authors: Chen K.-T. , Burger A. , Chen H. , Chen Y.-F. , Hansen K. , Suber L. , Wilson S. , Henderson J. , Wright G. W. , Cole M. L.
Published: April 2011

Lead iodide starting materials have been purified by vertical zone refining process. The purest materials of the zone-refined ingot, middle zone, were used for single crystal growth by Bridgman method. Differential scanning calorimetry, current-voltage and low temperature photoluminescence measurements were employed to investigate the effectness of zone refining process and as-grown crystal. The results showed that the materials from the middle section of zone-refined ingot is the purest, followed by first-to-freeze and last-to-freeze materials. No second phase and deviation from stoichiometry have been observed after zone refining process and Bridgman crystal growth method. The resistivities increase as the purity and crystallinity of materials increases. Cleavage of as-grown crystal did damage the surface and caused additional emission at 2.0 eV. This emission band was not observed after a 10% NaI solution etching.
Compound Semiconductor Detectors for X-Ray Astronomy: Spectroscopic Measurements and Material Characteristics
Authors: Bavdaz M. , Kraft S. , Peacock A. , Scholze F. , Wedowski M. , Ulm G. , Nenonen S. , Gagliardi M. A. , Gagliardi T. , Tuomi T. , Hjelt K. T. , Juvonen M.
Published: April 2011

The use of some specific compound semiconductors in the fabrication of high energy X-ray detectors shows significant potential for X-ray astrophysics space missions. We are currently investigating three high purity crystals - CdZnTe, GaAs and TlBr - as the basis for future hard X-ray detectors (above 10 keV). In this paper we present the first results on CdZnTe and GaAs based detectors and evaluate the factors currently still constraining the performance.

Energy resolutions (FWHM) of 0.9 keV and 1.1 keV at 14 keV and 60 keV, respectively, have been obtained with an epitaxial GaAs detector, while 0.7 keV and 1.5 keV FWHM were measured at the same energies with a CdZnTe detector. Based on these results it is clear, that the next generation of X-ray astrophysics missions now in the planning phase may well consider extending the photon energy range up to ∼100 keV by use of efficient detectors with reasonable spectroscopic capabilities.
The Reduction of The Defect Density in CdTe Buffer Layers for The Growth of HgCdTe Infrared Photodiodes on Si (211) Substrates
Authors: Wei H.-Y. , Salamanca-Riba L. , Dhar N. K.
Published: April 2011

CdTe epilayers were grown by molecular beam epitaxy on As-passivated nominal (211) Si substrates using thin interfacial ZnTe layers. By using thin recrystallized (initially amorphous) ZnTe buffer layers, we utilized migration enhanced epitaxy (MEE) in the ZnTe layer and overcome the tendency toward three dimensional nucleation. The threading dislocation densities in 8–9 μm thick CdTe films deposited on the recrystallized amorphous ZnTe films were in the range of 2 to 5 × 105cm−2. In addition to the reduction of threading dislocation density, the interface between the ZnTe layers and the Si substrate is much smoother and the microtwin density is an order of magnitude lower than in regular MEE growth. In order to understand the initial nucleation mechanism of the ZnTe on the As precursor Si surface, we also grew ZnTe epilayers on Te precursor treated Si substrates. The growth mode, microtwin density, and threading dislocation density are compared for films grown on Si substrates with different surface precursors and grown by different growth methods.
Pbte(Ga) - New Multispectral Infrared Photodetector
Authors: Belogorokhov A. I. , Ivanchik I. I. , Khokhlov D. R.
Published: April 2011

Doping of the lead telluride - narrow-gap semiconductor - with gallium results under certain conditions in the Fermi level pinning in the gap thus providing the semiinsulating state of material. Besides that, the persistent photoconductivity effect is observed at a temperatures T < Tc = 80 K. The photoresponse kinetics consists of two parts: the slow one with the characteristic time tchar going up to 104 s at T = 4.2 K, and the fast part with tchar, of the order of 10 ms. We have measured the spectra of a fast part of the photoresponse using the Fouriertransform spectrometer “Bruker” IFS- 113v. The photoconductivity is observed in two spectral regions: in the middle- and far - infrared. Response in the middle-infrared consists of the ordinary fundamental band and a strong superimposed resonance-like structure just at the bandgap energy. The position of this spectral line may be tuned in a wide range (3.5–5.5) μm by variation of temperature and/or composition of a lead telluride-based alloy. This middle-infrared photoresponse becomes considerable already at T = 160 K. The photoresponse in the far-infrared may be depending on the excitation conditions an analogous resonance-like structure at a wavelength 70 μm, or a broad band with the cutoff wavelength at least higher than 500 μm, which is the highest cutoff wavelength for the photon detectors observed up to date.
Photoluminescence Investigation of Surface Oxidation of C0.9Zn0.1 Te Detectors
Authors: Chen H. , Hayes M. , Chattopadhyay K. , Chen K. T. , Burger A. , Heffelfinger J. , James R. B.
Published: April 2011

The effect of surface oxidation of Cd1−xZnxTe (x = 0.1) detectors by chemical etching in hydrogen peroxide aqueous solution (H2O2) at different concentrations and etching times was investigated by low temperature photoluminescence (PL). The treatment resulted in better surface condition evidenced by the larger I(D0, X)/Idef intensity ratio and the narrower full width at half maximum of the main peak (D0, X). Peak shifts in the PL spectra associated with bound exciton lines and free to bound transition were also observed and attributed to the oxide layer. These surface effects were found to be dependent on H2O2 concentration and etching time. The significance of this surface oxidation on device passivation and the subsequent improvements in the detector performance are also discussed.
Ac Susceptibility Studies of New and Familiar Magnetic Molecular Solids
Authors: Sommer Roger D. , Korte Brenda J. , Sellers Scott P. , Yee Gordon T.
Published: April 2011

ac Susceptometry has been used to study a number of magnetic molecular solids including a new compound, Mn(II) octaethyltetraazaporphyrin, α-MnOETAP, and decamethylmanganocenium tetracyanoethenide, Mn(Cp*)2•TCNE, a previously reported molecule-based ferromagnet. Both of these compounds exhibit signatures of ferromagnetism including significant hysteresis below 2 K and rapidly increasing χT (where χ is the molar susceptibility) with decreasing temperature. However, their ac susceptibility data show relatively strong dependence of χ′ and χ″ on the frequency of the applied field, indicating a spinglass state. Other molecular ferromagnetic solids examined show much less sensitivity. These studies indicate that the standard practice of characterization by dc and ac susceptometry at a single frequency are clearly insufficient for identifying the magnetic state of a molecular solid.
Fabrication of Polymer Light Emitting Diodes by Layer-by-Layer Complexation Technique
Authors: Kim Jaehyun , Chittibabu Kethinni G. , Cazeca Mario J. , Kim Woohong , Kumar Jayant , Tripathy Sukant K.
Published: April 2011

Multilayer films were fabricated employing a new layer-by-layer complexation technique by alternatively dipping substrates in solutions of macromolecular ligands and Eu3+ ions. A luminescent poly[2-(3-thienyl)ethanol hydroxycarbonyl-methyl urethane] (H-PURET) was prepared by hydrolysis of thiophene polymer, poly[2-(3-thienyl)ethanol butoxycarbonyl-methyl urethane] (PURET), which was developed in our laboratory. H-PURET was used as macromolecular ligands. The multilayer deposition was monitored using UV-visible spectroscopy. As the number of bilayers increases, the absorption due to the polymer increases. The multilayer films were characterized by infrared and fluorescence spectroscopic techniques. Electroluminescence brightness easily obtained from the multilayer film of conjugated polymer-Eu3+ complex was measured to be about 40nW.
Light-Emitting Diodes with Voltage-Switchable Colors from Semiconducting Polymer/Polymer Heterojunctions
Authors: Zhang Xuejun , Jenekhe Samson A.
Published: April 2011

Reversible electroluminescence color changes with applied voltage have been observed in light-emitting diodes fabricated from semiconducting polymer heterojunctions consisting of an electron transporting polybenzobisthiazole and hole transporting poly(p-phenylene vinylene) when layer thicknesses are less than 60–100 nm. Enhanced device performances such as lower turn-on voltage and higher efficiency and luminance were also obtained compared to single-layer devices. The observed voltage-switchable emission colors in these nanoscale heterojunction light sources can be understood in terms of spatial confinement effects which are related to field-dependent charge transport and trapping processes in the materials. These results also demonstrate the use of new high temperature rigid-rod polymers as electron transport and emissive layers in electroluminescent devices.
Nanostructure of Electrically Conducting Polyaniline Prepared by a Novel Emulsion Polymerization Process
Authors: Liu J. , Kinlen P. J. , Graham C. R.
Published: April 2011

A soluble polyaniline (PANI) salt with moderate conductivity was synthesized by a novel emulsion polymerization process. The conductivity of the processed PANI films can be substantially increased by treating the polymer films with surfactants or with low molecular weight alcohols. Transmission electron microscopy (TEM) images of thin polymer films revealed the existence of small islands of conducting PANI embedded in a non-conducting, dopant matrix. The conductivity of the PANI films is affected by the spatial distribution and the connectivity of these small islands. The conductivity enhancement observed upon treatment with surfactants is due to self-assembly of conducting PANI molecules into an interconnected network morphology. In the case of alcohol treatment the film conductivity is enhanced due to extraction of excess dopant phase and the subsequent densification of PANI islands to form highly conducting pathways.
New Polydiacetylenes with Visible Chromophoric Side Groups
Authors: Foley James L. , Shivshankar Venkataramani , Sandman Daniel J.
Published: April 2011

In the interest of obtaining crystalline polydiacetylene with absorption at longer wavelengths, new derivatives of 2,4-hexadiyne with planar, visible absorbing aromatic chromophores have been designed, synthesized, and thermally polymerized. The resulting polymers have a red shifted maximum with absorption extending to the infrared. Their Raman spectra show the usual polydiacetylene ene-yne structure, and X-ray powder diffraction reveals that the new polymers are crystalline.
Temperature Dependence of the Electrical Conductivity of Poly(Benzo[1,2-b:4,5-b'] Dithiophene-4,8-Diyl Vinylene) and Poly(Dodecylthiophene)
Authors: Hyer R. C , Pethe R. G. , Yogi T. , Sharma S. C. , Wang J. , Meline R. L. , Elsenbaumer R. L. , McCullough R. C.
Published: April 2011

We present results for the electrical conductivity (σ) of thin films of poly(benzo[1,2-b:4,5- b']dithiophene-4,8-diyl vinylene) (PBDV) and poly (dodecylthiophene) (PDDT) as a function of temperature in the range 15-295K. The polymers were doped with FeC13 and PF6 which resulted in electrical conductivities differing by two orders of magnitude at room temperature. We examine three sets of σ(T)-data by using the variable-range hopping (VRH) model that predicts a linear relationship between ln(T1/2σ) and T1/4. We observe a change in the slope of the ln(T1/2σ) vs T14 relationship in all three samples at low temperatures. We also analyze the temperature dependence of the resistivity of PBDV by using the thermal fluctuation-induced tunneling model.
UV Photoemission Study of Interfaces Related to Organic EL Devices
Authors: Sugiyama Kiyoshi , Seki Kazuhiko , Ito Eisuke , Ouchi Yukio , ISHII Hisao
Published: April 2011

Interfacial electronic structures related to organic electroluminescent (EL) devices were studied by UV photoemission spectroscopy (UPS). The two classes of interfaces studied were: (1) interfaces in a typical multilayer device AI/AIq3TPD/ITO, where Alq3 is tris(8-hydroxyquinolino)- aluminum, TPD is N,N×-diphenyl-NN×-(3-methylphenyl)- 1, 1‘-biphenyl-4,4’-diamine, and ITO is indium tin oxide, and (2) TTN/metals and TCNQ/metals interfaces, where TTN is tetrathianaphthacene and TCNQ is tetracyanoquinodimethane. The UPS studies of the specimen formed by the successive deposition of TPD, Alq3, and Al on ITO revealed interfacial energy diagrams, with the vacuum level shift of - 0.25 eV (downward) and - 0.1 eV (downward) at the TPD / ITO and the Alq3 / TPD interfaces, respectively. The deposition of TTN and TCNQ on metals showed opposite direction of the shift of the vacuum level, with the positive and negative charge at the vacuum side. This can be explained by considering the chargetransfer between the metal and the organic molecule, with these directions being consistent with the electron donating and accepting ability of these molecules.
Control of Light-Emitting Polymer Devices Using Polymer/Polymer Interfaces
Authors: Epstein A. J. , Wang Y. Z. , Gebler D. D. , Fu D. K. , Swager T. M.
Published: April 2011

We present the use of polymer/polymer interfaces to control light-emitting polymer devices. Bilayer devices utilizing poly(9-vinyl carbazole) (PVK) as a hole transporting/electron blocking polymer together with a pyridine containing electron transporting layer show dramatically improved efficiency and brightness as compared to single layer devices. This is attributed to charge confinement and exciplex emission at the PVK/emitting polymer interface. The introduction of emeraldine base (EB) form of polyaniline (PAN) on both side of the emitting layer enables the device to work under both forward and reverse bias, as well as in AC modes. Interfaces play an important role in the operation of these devices. Furthermore, when the EB is replaced by sulfonated polyaniline (SPAN) on the cathode side and the emitting layer is properly modified to balance electron and hole transport, the device generates different colors of light, red under forward bias and green under reverse bias.
New Base-Dopable Well-Defined Poly-2,7-Fluorene Derivatives
Authors: Ranger M. , Leclerc M.
Published: April 2011

Well-defined poly(2,7-fluorene) derivatives have been prepared through palladium-catalyzed couplings; using this versatile synthetic method, processable polyfluorenes have been obtained in good yields. In solution, these yellow polymers exhibit blue emission around 410 nm with high quantum yields. Moreover, novel acidic polyfluorene derivatives have been synthesized (e.g. poly(2,7'-(pentyl 9,9-dioctyl-7,2'-bifluorene-9'-carbonyl))) which show, upon base-doping, electrical conductivities of 10−2 − 10−3 S/cm. This new doping method for conjugated polymers could open the way to the preparation of air-stable electron-injecting electrodes. Polyfluorene derivatives show their potential to play a double function in the fabrication of LEDs, i.e. as ntype electrode and luminescent polymeric materials.
Electronic Properties of Poly(Para-Phenylenes) Under High Pressure
Authors: Graupner W. , Guha S. , Yang S. , Chandrasekhar M. , Chandrasekhar H. R. , Leising G. , Scherf U. , Müllen K.
Published: April 2011

We have studied the photoluminescence emission spectra of polycrystalline and amorphous powder samples of phenylene-type polymers and oligomers. In order to modulate both intrachain and interchain interactions these investigations were performed at hydrostatic pressures up to 70 kbar and in a tOmperature range of 20 to 300 K. We report characteristic changes of the emission spectrum which depend on both the molecular environment as well as the intramolecular bond configuration.
Structure and Physical Properties of EDT-TTF Salts
Authors: Kondo Tetsuo , Kushch Lyudmila A. , Yamochi Hideki , Saito Gunzi
Published: April 2011

Charge-transfer salts of EDT-TTF with tetrahedral anions MX4 (M=Fe, Ga ; X=Cl, Br) were prepared. They are isostructural to each other (monoclinic P21/m) with the stoichiometry of 2:1. All of them are semiconductors having the conductivity at room temperature of 5 to 9 Scm−1 and activation energy of 40 to 170 meV. Since the calculated band structure of them indicate that they should be quasi one-dimensional metals, they were discussed from the point of structural deformation and strong electron correlation.
The Effect of RuO2/Pt Hybrid Bottom Electrode Structure on The Microstructure and Ferroelectric Properties of Sol-Gel Derived PZT Thin Films
Authors: Kim Seung-Hyun , Hong J. G. , Gunter J. C. , Lee H. Y. , Streiffer S. K. , Kingon Angus I.
Published: April 2011

Ferroelectric PZT thin films on thin RuO2 (10, 30, 50nm)/Pt hybrid bottom electrodes were successfully prepared by using a modified chemical solution deposition method. It was observed that the use of a lOnm RuO2Pt bottom electrode reduced leakage current, and gave more reliable capacitors with good microstructure compare to the use of thicker RuO2/Pt bottom electrodes. Typical P-E hysteresis behavior was observed even at an applied voltage of 3V, demonstrating greatly improved remanence and coercivity. Fatigue and breakdown characteristics, measured at 5V, showed stable behavior, and only below 13-15% degradation was observed up to 1010 cycles. Thicker RuO2 layers resulted in high leakage current density due to conducting lead ruthenate or PZT pyrochlore-ruthenate and a rosette-type microstructure.
A Thickness Dependent Study of SrBi2Nb2O9 Thin Films
Authors: Pérez W. , Ching-Prado E. , Reynés-Figueroa A. , Katiyar R. S. , Ravichandran D. , Bhalla A. S.
Published: April 2011

Thin films of SrBi2Nb2O9 (SBN) with thickness of 0.1, 0.2, 0.3 and 0.4 μm were grown by sol-gel technique on platinum/silicon substrates, and annealed at 800°C. Raman spectra of the samples present bands around 170,210, 272, 300,430, 580, 717, and 839 cm−1 which correspond to the SBN formation. The prominent Raman band around 839 cm−1, which is the Alg mode of the orthorhombic symmetry, is assigned to the symmetric stretching of the NbO6 octahedrals. The frequency of this band is found to shift at different places in the same sample, as well as from sample to sample. The frequency and width variations of the Raman bands are discussed in term of ions in non-equilibrium positions, which seem to be related with the crystallization degree in the SBN samples. Also, the Raman study indicates the presence of foreign sharp peaks, which are associated with the coexistence of phases other than SBN. The thickness dependence of the Raman spectra and the X-ray diffraction are also discussed. Finally, the experimental results of the SBN/Pt/Si films grown at 800°C are compared with those obtained at 650°C.
Retention Studies on Ferroelectric Media for High Data Storage Application
Authors: Yoo I. K. , Kim B. M. , Kim D. S. , Park S. J.
Published: April 2011

Data retention may be affected by depolarization, domain stabilization (ageing or imprint), and fuzzy electric field among neighboring bits in relation to microstructures of ferroelectric media. In this paper, the smearing effect due to electric field between two adjacent bits was demonstrated. In order to minimize the smearing effect, ferroelectric media with the top electrode is proposed by which fuzzy electric field can be screened by bound charges in the electrode. Bit on electrode (BOE) technique was suggested for “Write” (local polarization) and “Read” on ferroelectric media with the top electrode (ferroelectric capacitor). It is noticed that a highly sensitive device such as single electron transistor is indispensable for measuring potential variation in the top electrode of the ferroelectric capacitor media.
Frequency Spectra of Fatigue of PZT and other Ferroelectric Thin Films
Authors: Du Xiaofeng , Chen I-Wei
Published: April 2011

Polarization and polarization fatigue of PZT and other ferroelectric thin films have been studied via the frequency spectra of D-E hysteresis. The coercive field (Ec) of PZT thin films has been found strongly dependent on the measuring frequency, while a relatively flat frequency response is observed with SrBi2Nb2O9 thin films. The different fatigue behavior can be attributed to such a difference in the frequency response. Physical models have been suggested to for domain wall movement in PZT and SrBi2Nb2O9 thin films. Based on these observations, a methodology has been proposed to evaluate the high frequency and fatigue properties of ferroelectric thin films.
Deposition and Electrical Characterization of Epitaxial Pb(Mg1/3Nb2/3)O3-PbTiO3 (70/30) Thin Films
Authors: Maria J-P. , Hackenberger Wes , Trolier-McKinstry S.
Published: April 2011

(001)-oriented heterostructures consisting of LaAlCO3 substrates, SrRuO3 bottom electrodes, and Pb(Mg1/3Nb2/3) O3-PbTiO3 (PMN-PT) piezoelectric actuators were deposited by pulsed laser deposition (PLD). 4-circle x-ray diffraction analysis confirmed the epitaxial growth of each layer. In general, the electrical properties were found to be very sensitive to the processing conditions, in particular, the growth temperature. At growth temperatures below ∼620°C, the temperature dependence of the dielectric constant and the onset of a hysteritic polarization were found to be depressed by as much as 80 °C. When growth temperatures were increased above 660°C, electrical properties with temperature dependencies more consistent with those of single crystals were observed.
Structural Characterization of a Series of New Ternary η-Nitride Compounds
Authors: Weil K. S. , Kumta P. N.
Published: April 2011

The structures of four new tungsten based, ternary nitride compounds, Fe3W3N, Ni6W6N, Ni2W4N, and Fe4W2N, each prepared using a complexed precursor synthesis route, have been determined by Rietveld analyses of the respective powder x-ray diffraction (PXRD) data. Each compound crystallizes in a relatively complex cubic structure which is in general isostructural with the η-carbide structure. However, subtle structural differences which are compositionally dependent do exist between each nitride and these will be examined in detail in this paper.
A Comparison of Ferroelectric thin Films Prepared by Sol-Gel, Metalorganic Deposition and Photochemical Methods
Authors: Shi Y. , Blair S. L. , Yaroslavsky I. , Hill R. H.
Published: April 2011

The process for generating films of Ba0.5Sr0.5TiO3, and PbZr0.48Ti0.52O3 by photochemical deposition from metal-organic thin films has been investigated. Films have also been prepared by metal-organic and sol-gel deposition for comparison with the photochemical method. All three methods could produce crystalline films of the target materials. Studies of the heating of the amorphous films prepared by each of the methods indicated that similar crystalline films could be prepared by the different methods. Under some conditions the photochemical methods gave the highest degree of orientation of the crystalline films.
Effect of Precursors and Stacking Structures on Crystallization of Multi-Layered Lead Zirconate Tit Anate Thin Films by Sol-Gel Method
Authors: Suzuki H. , Kondo Y. , Kaneko S. , Tsutsumi T. , Miura T. , Hayashii T.
Published: April 2011

Ferroelectric tead zirconate titanate, Pb(Zrx Tibx)O3 (hereafter abbreviated as PZT), thin films were prepared by annealing precursor films of multilayered structures composed of alternating layers of PZT aiKL lead titanate (hereafter abbreviated as PT). This method (which we refer to as multi-seeding) was used in order to lower the processing temperature of PZT. The precursor films were prepared from alkoxide precursor solutions. Effects of zirconium to titanium ratios and stacking structures of the multi-layered precursor films on crystallization behavior were studied to improve the electrical properties of the resultant PZT thin films. Layers of PT were inserted between every PZT layer in order to seed the crystallization of the desired perovskite phase. PT has previously been shown to crystallize with a pure perovskite structure at temperatures as low as 450 °C. Precursor layers of PZT with different compositions, ranging from x = 1 to x = 0.53 were prepared. In this process, the compositions of the PZT precursors and/or the stacking structure, as well as the heating schedule, had a large effect on the crystallization behavior. Nucleation control of the PT seeding layer by changing the heating schedules played an important role in preparing perovskite PZT thin films at low temperatures. Dielectric properties of the resultant films depended on the compositions and annealing temperatures. It was demonstrated that the composition of the resultant PZT film was controllable in the multi-seeding process, and that dielectric properties of the resultant films were improved.
Electrodeposited CuInSe2 Thin Film Junctions
Authors: Raffaelle R. P. , Mantovani J. G. , Bailey S. G. , Hepp A. F. , Gordon E. M. , Haraway R.
Published: April 2011

We have investigated thin films and junctions based on copper indium diselenide (CIS) which have been grown by electrochemical deposition. CIS is a leading candidate for use in polycrystalline thin film photovoltaic solar cells. Electrodeposition is a cost-effective method for producing thin-film CIS. We have produced both p and n type CIS thin films from the same aqueous solution by simply varying the deposition potential. A CIS pn junction was deposited using a step-function potential. Stoichiometry of the single layer films was determined by energy dispersive spectroscopy. Carrier densities of these films increased with deviation from stoichiometry, as determined by the capacitance versus voltage dependence of Schottky contacts. Optical bandgaps for the single layer films as determined by transmission spectrocopy were also found to increase with deviation from stoichiometry. Rectifying current versus voltage characteristics were demonstrated for the Schottky barriers and for the pn junction.
Microstructures in thin BaTiO3 Films by Hydrothermal Method
Authors: Hoffmann T. , Fuenzalida V. M.
Published: April 2011

Barium titanate microstructures are fabricated on silicon(100)/platinum substrates coated with photoresist and titanium by a combination of hydrothermal and lift-off techniques. The microstructures of 10μm width are well defined. The barium titanate films grow in its cubic phase. Analysis by means of x-ray diffraction and scanning electron microscopy shows that only a part of the titanium layer is affected by the hydrothermal reaction. This limitation may be overcome by application of electrochemistry.
Investigation on the Growth Mechanism of Zinc Oxide Film Prepared by Electrochemical Method
Authors: Lee Jaeyoung , Tak Yongsug
Published: April 2011

ZnO thin films were potentiostatically deposited on ITO electrode in 0.1 M Zn(NO3)2 and the film growth mechanism was investigated by using FTIR and electrochemical quartz crystal microbalance(EQCM). Intermediates formed in the initial stage were identified as soluble zinc hydroxides and a critical concentration of OH was required for the ZnO to be deposited. A rapid growth rate of ZnO film observed in the presence of O2 was attributed to the higher cathodic current which produces OH
Relationship Between Catalytic Activity and Electrical Conductivity in the Nonstoichiometric Nickel Manganite Spinels
Authors: Laberty Christel , Alphonse Pierre , Rousset Abel
Published: April 2011

Nonstoichiometric nickel manganite spinels NixMn3-x □3δ/4O4+δ, have been synthesised by calcination of mixed oxalates in air at 350°C. The variation of the electrical conductivity σ with partial pressure of O2 shows that these oxides are n-type semiconductors; σ also varies with the nickel content and has a maximum at x = 0.6. The intrinsic catalytic activity of these oxides for CO/CO2 conversion varies with nickel content and the most active catalyst is at x=0.6 where the conversion starts at room temperature. The variation of the catalytic activity and the electrical conductivity and the nickel amount are correlated. Apparent activation energies are very low (less than 20 kJ/mol) and remain the same for all these mixed oxides. Similarly, the reaction order with respect to O2 and CO does not depend on the nickel content (order/O2 ≈ 0; order/CO ≈ 0.6). A reaction mechanism involving formation of oxygen ions adsorbed and carbonate species is discussed.
A Field Emission Study of the Critical Parameters of Amorphous Carbon Films Deposited on a Variety of Carbonaceous Substrates
Authors: Burden A. P. , Forrest R. , Silva S.R.P. , Sealy B. J. , Amaratunga G.A.J.
Published: April 2011

The field emission properties of a variety of nitrogen-containing hydrogenated amorphous carbon films have been characterised as a function of film thickness and substrate type. Identified trends have been discussed in terms of the optical band-gap and refractive index of the films, and the surface roughness of the substrates. In addition, carbon-based materials have been considered as inexpensive film-compatible substrates, and an in-situ oxygen plasma pre-treatment has been investigated as a means of changing the field enhancement factor of the system. We have achieved field emission with threshold voltages as low as 8 V μm−1, and we present data that supports the view that the electron emission from amorphous carbon is dependent on the nature of the back contact, and possibly the ease at which the film can be fully depleted, i.e. film thickness.
LCVD of CNx Layers from NH3,/CCI4. Mixture using CuBr Vapor Laser
Authors: Ivanov B. , Popov C. , Dimitrov D. , Shanov Y , Zambov L. , Georgiev M. , Peev G.
Published: April 2011

Amorphous CNx films were obtained on monocrystalline silicon substrates by direct writing laser induced chemical vapor deposition from CCI4 and NH3 using CuBr vapor laser. The main process parameters (scanning speed, laser power, background temperature) were varied in wide ranges. The deposition rates in the laser spot were in the range of 1 – 10 μm/s. Scanning electron microscopy showed that the layers had rather rough surface. The deposited films were composed of carbon, nitrogen, silicon and oxygen, as detected by AES and EDX analyses. Chemical bonding structure was investigated by FTIR and showed absorption bands corresponding to different chemical groups - CH, CH2, CH3, C=C, C=N, C=O, Si-O, Si-C, Si-N and C-N. The electrical measurements of the deposited films showed that their resistivity varied from 0.15 to 1.40 MΩ.cm and it was very sensitive to the deposition conditions.
Quantitative Studies of Tetrahedral Bonding in Amorphous Carbon Films Using Ultraviolet Raman Spectroscopy
Authors: Gilkes K. W. R. , Prawer S. , Robertson J. , Sands H. S.
Published: April 2011

The bonding in a series of unhydrogenated amorphous carbon films has been analysed quantitatively using Raman spectroscopy with ultraviolet excitation. The Raman spectra exhibit two broad Raman peaks at 1650 cm−1 and 1100 cm−1, due to sp2 and sp3 vibrational modes respectively. The former is a resonance feature associated with a large proportion of paired sp2 sites, while the latter is a weighted vibrational density-of-states for the distorted random network of sp3 sites. The position and relative intensity of the two peaks are shown to be strongly correlated with the percentage of sp3 sites in the films, providing a reliable measure of sp3 bonding which is both quantitative and non-destructive.
High-Pressure Chemistry of Carbon Nitride Materials
Authors: Stevens Andrew J. , Agee Carl B. , Lieber Charles M.
Published: April 2011

The composition and properties of the sp2-bonded carbon nitride precursor paracyanogen (pCN) has been studied at high pressures and temperatures. Paracyanogen decomposes to carbon and molecular nitrogen with the decomposition temperature increasing with pressure over the range of 3 to 19 GPa. Prior to decomposition, pCN can be transformed to an atmospheric-pressure quenchable phase that is more than 25% higher in density and over an order of magnitude harder than the starting material. Structural analysis of this quenchable phase shows, however, that it consists of a sp2-bonded network. In addition, the decomposition kinetics of paracyanogen have been studied in detail. Rapid, self-propagating decomposition occurs above a threshold temperature. Below this, decomposition rates exhibit an Arrhenius behavior with activation energy and volume of 2.7 eV and 3.9 Å3, respectively The decomposition rates depend on the nitrogen density and decrease significantly with lower nitrogen concentration. Kinetic effects favoring a graphite-like, sp2-bonded structure may preclude the high-pressure synthesis of superhard, sp3-bonded carbon nitride solids below their thermodynamic stability limit, unless an optimally designed precursor is employed.
High Pressure and High Temperature Equation-of-State of Gamma and Liquid Iron
Authors: Chen George Q. , Ahrens Thomas J.
Published: April 2011

Shock-wave experiments on pure iron preheated to 1573 K were conducted in the 17–73 GPa range. The shock-wave equation of state of γ-iron at an initial temperature of 1573 K can be fit with us = 4.102 (0.015) km/s + 1.610(0.014) up with ρo = 7.413±0.012 Mg/m3 We obtain for γ-iron's bulk modulus and pressure derivative the values: 124.7±1.1 GPa and 5.44±0.06, respectively.

We present new data for sound velocities in the γ- and liquid-phases. In the γ-phase, to a first approximation, the longitudinal sound velocity is linear with respect to density: Vp = −3.13 (0.72) + 1.119(0.084) p(units for Vp and p are km/s and Mg/m3, respectively). Melting was observed in the highest pressure (about 70–73 GPa) experiments at a calculated shock temperature of 2775±160 K. This result is consistent with a previously calculated melting curve (for ε-iron) which is close to those measured by Boehler [1] and Saxena et al. [2]. The liquid iron sound velocity data yields a Grüneisen parameter value of 1.63±0.28 at 9.37±0.02 Mg/m3 at 71.6 GPa. The quantity γρ is 15.2±2.6 Mg/m3, which agrees with the uncertainty bounds of Brown and McQueen [3] (13.3–19.6 Mg/m3). Based on upward pressure and temperature extrapolation of the melting curve of γ-iron, the estimated inner core-outer core boundary temperature is 5500±400 K, the temperature at the core-mantle boundary on the outer core side is 3930±630 K.
Stabilization and transformation of the phases in nanostructured irconia prepared by wet chemical synthesis route
Authors: Xiaol T. D. , Bokhimi X. , Garcia-Ruiz A. , Morales A. , Wang D. M. , Chen H. , Struttl P. R.
Published: April 2011

Nanostructured yttrium stabilized zirconia powders with yttria concentrations between 0.0 and 10.0 mol % were prepared via an aqueous chemical synthesis route. This synthesis involved the spray atomization of the aqueous solution mixture of zirconyl chloride and yttrium chloride into a reaction vessel that contained a diluted ammonium hydroxide, followed by ultrasonication, separation and heat treatment. These powders were characterized using SEM, TEM, XRD, and chemical analysis. The crystalline structure was refined using the Rietveld technique. At temperatures below 200 °C, the powders were amorphous solid solutions with an structure independent of yttria concentration, where yttrium atoms occupied the zirconium positions in the zirconyl group, e.g., (Zr4(1-x) Y4x(OH)8(OH2)16)(8-4x)+. Annealing the sample at 400 °C, the amorphous phases crystallized into monoclinic, tetragonal or cubic nanocrystalline zirconia, depending on yttria concentration, where the non-doped samples had a mixture of monoclinic and tetragonal phases.
Mechanisms of Energy Transfer in Solids Irradiated with Swift Heavy Ions
Authors: Szenes G.
Published: April 2011

The damage cross section velocity effect is studied in LiNbO3, Y3Fe5O12 and SiO2 α-quartz. The application of our thermal spike model reveals that the efficiency of track formation varies by a factor of two in the range of 2–4 MeV/nucleon. The effect is explained by the varying fraction of energy deposition to the lattice involving lattice ions.
Ion Beam Mixing and Thermal Demixing of Co/Cu Multilayers
Authors: Cai M. , Veres T. , Cochrane R. W. , Roorda S. , Abdouche R. , Sutton M.
Published: April 2011

X-ray reflectivity and magnetotransport studies have been used to probe the effects of ion-beam irradiation and subsequent thermal annealing on the structure and giant magnetoresistance (GMR) in Co/Cu multilayers. Low-dose ion bombardment produces interfacial mixing which is accompanied by a systematic suppression of the anti ferromagnetic (AF) coupling and the GMR. For ion doses not exceeding 5 × 1014 ions/cm2, subsequent thermal annealing restores the abrupt interlayer structure as well as the GMR. The combination of low-dose ion bombardment and thermal annealing provides an ex situ technique to modify interface structure reversibly over a gnificant range.