bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Amorphizing Implants on Boron Diffusion in Silicon
Authors: Chao H. S. , Griffin P. B. , Plummer J. D.
Published: April 2011

The transient enhanced diffusion behavior of B after ion implantation above the amorphization threshold is investigated. The experimental structure uses a layer of epitaxially grown Si, uniformly doped with B to act as a diffusion monitor. Wafers using this structure are implanted with amorphizing doses of Si, As, or P and annealed for various times at various temperatures. The experimental results show that upon annealing after Si implantation, there is a large amount of B pile-up that occurs at the amorphous/crystalline (A/C) interface while B is depleted from the region just beyond the A/C interface. This pile-up/depletion phenomenon can be attributed to the dislocation loops that form at the A/C interface. These loops act as sinks for interstitial point defects. There is also B pile-up/depletion behavior for As and P implants as well. However, this behavior may be explained by an electric field enhancement effect. While dislocation loops are known to form at the A/C interface for all of the investigated implant conditions, it appears that while they are necessary to simulate for Si amorphizing implants, they may not be necessary to simulate for As and P amorphizing implants.
Low Level Cu Contamination of Silicon During Wet Cleaning Studied by Transient Ion Drift
Authors: Heiser T. , Mchugo S. , Hieslmair H. , Weber E. R.
Published: April 2011

Interstitial copper (CUi) drift induced transient capacitance signals of a Schottky barrier are analysed after copper indiffusion at various temperatures and thermal quenching. Against the general expectation we show that most Cu impurities remain interstitially dissolved. Consequently, such transient ion drift analyses can be used to detect copper in silicon with a detection limit of the order of 1011cm−3. We applied the method to study Cu contamination of silicon samples after chemical cleaning and high temperature annealing. After a short dip into a copper contaminated aqueous solution and subsequent annealing at 1000C for 10 minutes, a strong correlation is found between the bulk copper concentration and the copper density in the solution. A density as low as 50 atomic parts per billion is found to be sufficient to induce a bulk copper concentration of about 5.1013cm−3.
Study of Point Defect Concentrations During the Fluorinated Oxidation of Silicon
Authors: Jaccodine R. J. , Kim U. S.
Published: April 2011

Some of our most important and quantitative insights on intrinsic point defects have been established as a result of the study of the influence of oxidation on their “excess” concentrations. From study of the growth and shrinkage of oxidation induced stacking faults (OSF) and from oxidation enhanced or retarded diffusion (OED-ORD) the fractional contribution of self-interstitials and vacancies can be assessed. The dominant influence on relatively thin dry or wet oxides is that of the injection of self-interstitials away from the oxidizing interface into the bulk crystal. These self-interstitials have been variously attributed to the incompleteness of oxidation or interracial stress and relaxation at the Si-SiO2 interface. We have studied the role of fluorine additives (ppm) to the dry oxidation process. This paper will discuss similar oxidation-related phenomena (OSF, OED, and ORD), confirming that under our experimental conditions with normally dry oxidation plus fluorine the active point defect injection consists mainly of “excess” vacancies. OSF anneal at lower temperatures than with nitridation processes and with a lower activation energy (1.7 eV). The study of P,B,As, Sb oxidation enhances-retarded diffusions validates the conclusion, with P,B yielding ORD instead of OED and Sb being enhanced rather than retarded as in normal oxidation. Oxidation-induced diffusion experiments not only explored the role of the specific impurity (P,B,As,Sb) but also utilized specimens with four adjacent active regions (bare Si, oxide covered Si, nitride covered Si, and the normal control oxide covered by nitride). The ratios of Ci/Ci* and Cv/Cv* for fluorine addition will be contrasted with those formed by dry oxidation.
Microstructure and Optoelectronic Properties of CdSe-Thin Films
Authors: Klement U. , Ernst F.
Published: April 2011

CdSe appears to be a promising material to replace amorphous hydrogenated silicon as the photosensitive part in the retina of the “Electronic Eye”, a camera based on thin film technique. We have investigated the influence of post-depositional annealing treatments with respect to the optimization of the photoconductive properties. TEM-, AFM- and XPS-measurements on CdSe thin films are reported. The formation of an oxide could not be detected by XPS-depth profiling of films annealed in air but chemisorption of oxygen is expected at the intergrain boundaries. Hence, high potential barriers for electron transport will be introduced. Under illumination, trapping of photo-generated holes will neutralize the charge at the intergrain boundaries leading to improved electric properties. However, the homogeneity of the photoconductive properties in CdSe is not yet satisfying. The formation of swellings and holes on the sample surface, found by AFM-measurements, can perhaps explain the inhomogeneity of the photoconductive properties. Using Si wafers as substrate material no improvement in texturing could be reached, since an amorphous CdSe-interlayer is formed.
Comparison of the Structure of Grain Boundaries in Silicon and Diamond by Molecular-Dynamics Simulations
Authors: Keblinski P. , Phillpot S. R. , Wolf D. , Gleiter H.
Published: April 2011

Molecular-dynamics simulations were used to synthesize nanocrystalline silicon with a grain size of up to 75 Å by crystallization of randomly misoriented crystalline seeds from the melt. The structures of the highly-constrained interfaces in the nanocrystal were found to be essentially indistinguishable from those of high-energy bicrystalline grain boundaries (GBs) and similar to the structure of amorphous silicon. Despite disorder, these GBs exhibit predominantly four-coordinated (sp3-like) atoms and therefore have very few dangling bonds. By contrast, the majority of the atoms in high-energy bicrystalline GBs in diamond are three-coordinated (sp2-like). Despite the large fraction of three-coordinated GB carbon atoms, they are rather poorly connected amongst themselves, thus likely preventing any type of graphite-like electrical conduction through the GBs.
In-Plane Crystallographic Texture of Bcc Metal thin films on Amorphous Substrates
Authors: Harper J.M.E. , Rodbell K.P. , Colgan E.G. , Hammond R.H.
Published: April 2011

We show that dramatically different in-plane crystallographic textures can be produced in body centered cubic (bcc) metal thin films deposited under different conditions. The orientation distribution of polycrystalline bcc thin films on amorphous substrates often has a strong (110) fiber texture, and an in-plane texture may develop when deposition takes place with an off-normal incidence flux of energetic ions or atoms. Three orientations in Nb films have been observed in which the energetic particle flux coincides with crystal channeling directions. In-plane orientations in Mo films have also been obtained in magnetron sputtering systems. The selected orientations are reviewed, and examples are given in which the in-plane orientation of Mo deposited in two similar magnetron sputtering systems differs by a 90° rotation. The origins of in-plane texture in rectangular magnetron sputtering systems are discussed.
Analysis of Residual Stress in Polycrystalline Silver Thin Films by X-Ray Diffraction
Authors: Alford T. L. , Zeng Yuxiao , Zou Y. L. , Deng F. , Lau S. S. , Laursen T. , Manfred Ullrich B.
Published: April 2011

The stress state of evaporated Ag films prepared on Ti underlayers before and after encapsulation process has been studied by x-ray diffraction using a “sin2ψ” technique. A low tensile stress of approximately 61 MPa was measured in the as-deposited Ag films. The stress was caused by nonequilibrium growth during film deposition and resulted in a lattice tension state in the film plane and a lattice compression state along the film normal. Thermal mismatch stress was produced by the encapsulation process at 600 °C, but most of this stress relaxed during the cooling stage, and a residual tensile stress of ∼ 320 MPa in the film plane was determined.
Study on Relaxor Ferroelectric Thin Films of Tungsten Bronze Pb1-xBaxNb2O6 by RF Magnetron Sputtering
Authors: Xiao X. , Xu N. , Li L.
Published: April 2011

Ferroelectric thin films of tungsten bronze lead barium niobáte (PBN) were fabricated by radio frequency magnetron sputtering. Oriented growths of the thin films were observed along (001) in tetragonal phase and along (002) in orthorhombic phase. Excess amount of PbO (6 wt %) in the PBN targets were used to compensate Pb evaporation during sputtering deposition. Ferroelectric properties were investigated as a function of annealing temperatures. The thin film with high quality was annealed at 650 °C, while its remnant polarization (Pr) and coercive field (Ec) were equal to 47.9 μC/cm2 and 5.2 kV/cm, respectively.
Tensile Behavior of Free-Standing Gold Films
Authors: Emery R.D. , Lenshek D.X. , Behin B. , Gherasimova M. , Povirk G.L.
Published: April 2011

A method for tensile testing thin gold films is presented. Free-standing tensile specimens were prepared by evaporating 0.8 μm of gold onto a patterned oxidized silicon wafer. Using common microelectronic fabrication techniques, free-standing thin film specimens were produced that span rectangular windows in the wafer. The wafer was diced into individual tensile specimens composed of a thin film surrounded by a silicon frame. The final step before testing was to cleave the silicon frame so that the load was completely carried by the metal film. The ultimate tensile strength of the films was found to be approximately 150% greater than that of annealed bulk gold. In contrast, the measured elastic modulus for the thin film specimens was approximately the same as that documented for bulk gold.
Texture in films and Coatings
Authors: Szpunar J.A.
Published: April 2011

The field of films and coatings is very broad. In general, the structure of films may comprise several phases, each having a different micro-structure and composition. These phases may be built up from grains which have different sizes, shape, morphology and orientation. A description of those types of films is complex and a large number of structural parameters is needed to fully characterize them. It is therefore more convenient to use a statistical description of them and to specify the relative proportion of different phases, grain orientation distribution [1], the orientation correlation between neighbouring crystals [2] and grain shape and size distribution [3]. Such a description provides details of the microstructural geometry of films, thereby giving a frame of reference within which various properties of films and a microstructural transformation of film structure, can be analyzed. Such microstructural descriptions have to be often supplemented by information about the nature and distribution of lattice defects, dislocations, stacking faults and antiphase boundaries. All this information put together, helps to provide a better understanding of the behaviour and various physical, chemical, mechanical and other properties, of films and coatings.
The Electrical Properties of In-situ Doped Polycrystalline Silicon Thin Films Grown by Electron Cyclotron Resonance Chemical Vapor Deposition at 250°C
Authors: Jiang Yeu-Long , Wang Ruo-Yu , Hwang Huey-Liang , Yew Tri-Rung
Published: April 2011

The phosphorus doped polycrystalline silicon thin films were grown by Electron Cyclotron Resonance Chemical Vapor Deposition (ECR-CVD) at 250°C. The doping gas PH3 was in-situ added with SiH4 gas during the films deposition. All films were deposited with 90% hydrogen dilution ratio. The resistivity of the films is varied from 0.2 to 7Ω-cm and decrease as the PH3/SiH4 gas ratio increase from (3/100 to 7/100). From the SIMS data, the doping concentration is all about 1020cm-3. The activation energy is decreased from 0.35 eV to 0.12 eV as the dopant concentration increased from 0.8×10 20cm-3 to 4.7×10 20cm-3. From the Hall measurements, the carrier mobility is about 2∼4 cm2/V. sec, and the carrier concentration is the 0.5∼1% of the dopant concentration. The gain boundary trap density predicted by the trapping model is about 4×l013cm” 2-2
Analyses of the Grain Boundary Misorientation and Oxygen Content of Bulk Processed YBa2Cu3O7-δ
Authors: Wang Jenn-Yue , King Alexander H. , Zhu Yimei , Wang Yuan-Liang , Suenaga Mas Aki
Published: April 2011

The grain boundary misorientation distribution of 203 grain boundaries in bulk processed high Tc superconductor YBa2Cu3O7-δ with five processing conditions, was studied. Two complementary analytical approaches, Grain Boundary Misorientation Distribution (GBMD) from the random description, using a hypothesis test and X2 analysis, and Grain Boundary Character Distribution (GBCD), using the Coincidence Site Lattice (CSL) model, were applied. The GBMD and GBCD both showed grain boundary evolution departing from a random distribution above 935°C processing temperature. The GBCD analyses indicated an approximately linear increase in the population of CSL-related boundaries, among which the tetragonal CSL (c/a ≠ 3) boundaries grew in the same trend while orthorombic boundaries (c/a = 3) became stagnated. The results from comparing the corresponding GBCD and volume averaged Jc for each batch indicated that the tetragonal CSL boundaries were oxygen deficient and accounted for, among other current limiting factors, lower current carrying ability.
SPFM Pre-Cleaning for formation of Silicon Interfaces by Wafer
Bonding
Authors: Bengtsson Stefan , Ljungberg Karin
Published: April 2011

The use of H2SO4:H2O2:HF (SPFM)
at low HF concentrations (10 to 1000 ppm) has been investigated as the
preparation procedure prior to formation of Si/Si interfaces by wafer
bonding. The SPFM cleaning process makes it possible to form a hydrophilic
(OH terminated) silicon surface, thereby achieving a spontaneous and strong
room temperature bond. Electrical characterization using current vs voltage
and spreading resistance measurements shows that this cleaning procedure can
be used to form Si/Si junctions with excellent electrical properties. Some
of the problems related to hydrophobic wafer bonding can thus be
circumvented by the proposed technique.
Oxidation Resistance of Ultrathin Silicon Nitride Passivation
Layers on Si(100)
Authors: Kamath A. , Kim B. Y. , Blass P. M. , Sun Y. M. , White J. M. , Kwong D. L.
Published: April 2011

The oxidation resistance of ultrathin (5–15Å) thermally grown silicon
nitride (Si3N4), in conditions relevant to the
deposition/annealing of Tantalum Pentoxide (Ta2O5) in
a Rapid Thermal Processing (RTP) environment, has been non destructively
examined using X-Ray Photoelectron Spectroscopy (XPS). This has been carried
out with a view to establishing a process window for the deposition of
Ta2O5 on a Rapid Thermally Nitrided (RTN) Si(100)
surface, with negligible oxidation of the Si(100) substrate. A physical
model of the oxidation process of these films is also proposed.
An Analysis of Infrared Spectroscopic Geometries
Authors: Merklin Gregory T. , Luo Huihong , Chidsey Christopher E. D.
Published: April 2011

The influence of experimental geometry on the signal strength and
signal-to-noise ratio of infrared spectrometry has been investigated. In
general, it was found that the choice of optimum experimental geometry
depended on the orientation of the vibrational mode being investigated. In
particular, it has been calculated that internal reflection spectrometry is
relatively insensitive to vibrational modes perpendicular to the surface
relative to transmission spectroscopy at Brewster's angle, and this has been
confirmed by experiment.
Ni Removal from Si Wafers by Low-Pressure UV-Chlorine
Cleaning
Authors: Courtney C. H. , Lamb H. H.
Published: April 2011

Ni removal from Si wafers by low-pressure UV/Cl2 chemical vapor
cleaning (CVC) was investigated at substrate temperatures of 150–200°C.
Sub-monolayer Ni coverages were applied to Si(100) by ultrahigh-vacuum
physical vapor deposition (UHV-PVD). The Ni surface concentration was
reduced to the Auger electron spectroscopy (AES) detection limit by a 2-min
UV/Cl2 exposure at 300 mTorr and 200°C. AES depth profiling
revealed that Ni was not contained within nor buried beneath the chlorosilyl
layer formed by UV/Cl2 CVC. In contrast, Ni was not removed under
similar conditions from Si surfaces covered by a thin UV/air oxide layer.
These results indicate that Ni removal from Si occurs by a photochemical
etching mechanism and not by direct volatilization of NiCl2.
Atomic force microscopy (AFM) of Si surfaces after UV/Cl2 CVC
indicated that Si etching was limited ˜20 å and that the surface was smooth
(RMS roughness = 1.6 å).
Water use Efficiency in Immersion Wafer Rinsing
Authors: Roche Thomas S. , Peterson Thomas W. , Hansen Eric
Published: April 2011

This work is an effort to determine if we can use less water effectively in
rinse processes. We have run experiments to examine our current usage and to
determine if we can use water more effectively.

This work will describe the experiments which have been done relating the
amount of chemical remaining on the wafers to variables of the: rinse such
as flow rate, wafer spacing and the cycling of the rinse valves. We will
discuss the conclusions we have reached based on those experiments and the
directions we will be taking to improve rinsing efficiency.
Advanced Thermoelectric Materials and Systems for Automotive Applications in the Next Millennium
Authors: Morelli Donald T.
Published: April 2011

A combination of environmental, economic, and technological drivers has led to a reassessment of the potential for using thermoelectric devices in several automotive applications. In order for this technology to achieve its ultimate potential, new materials with enhanced thermoelectric properties are required. Experimental results on the fundamental physical properties of some new thermoelectric materials, including filled skutterudites and 1–1–1 intermetallic semiconductors, are presented.
Positive and Negative Luminescent Infrared Sources and Their Applications
Authors: Ashley T.
Published: April 2011

We describe uncooled mid-infrared light emitting and negative luminescent diodes made from indium antimonide based IlI-V compounds, and long wavelength devices made from mercury cadmium telluride. The techniques to produce large area positive and negative luminescent sources, and the application of these devices to gas sensing, improved thermal imagers and imager testing is discussed.
Recent Progress in the Growth of Mid-ir Emitters by Metalorganic Chemical Vapor Deposition
Authors: Biefeld R. M. , Allerman A. A. , Kurtz S. R. , Baucom K. C.
Published: April 2011

We report on recent progress and improvements in the metal-organic chemical vapor deposition (MOCVD) growth of mid-infrared lasers and using a high speed rotating disk reactor (RDR). The devices contain AlAsSb claddings and strained InAsSb active regions. These lasers have multi-stage, type I InAsSb/InAsP quantum well active regions. A semi-metal GaAsSb/InAs layer acts as an internal electron source for the multi-stage injection lasers and AlAsSb is an electron confinement layer. These structures are the first MOCVD multi-stage devices. Growth in an RDR was necessary to avoid the previously observed Al memory effects found in conventional horizontal reactors. A single stage, optically pumped laser yielded improved power (> 650 mW/facet) at 80 K and 3.8 μm. A multi-stage 3.8–3.9 μm laser structure operated up to T=170 K. At 80 K, peak power > 100 mW and a high slope-efficiency were observed in gain guided lasers.
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 buffei 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 tm thick CdTe films deposited on the recrystallized amorphous ZnTe films were in the range of 2 to 5 × 105 cm−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.
Theory of Critical Layer Thickness of Nonconstant Quantum-Well Width Produced by Interdiffusion and its Optoelectronics Consequence
Authors: Chan Michael C. Y. , Li E. Herbert
Published: April 2011

In this paper, the concept of critical layer thickness is applied to the interdiffused quantum well (DFQW) structure. For the as-grown InGaAs/LnP lattice matched quantum well, the interdiffusion process will induce in-plane strain into the DFQW forming a lattice mismatched system. The relation between the as-grown well width (Lz) and the diffusion length (Ld) for formation of dislocation is presented.
Analysis of AlGaAs/GaAs Multiple Quantum Well Dual Waveguides Defined by Ion Implantation Induced Intermixing
Authors: Lo Kai-Ming
Published: April 2011

A simple and accurate model is presented for the study of ion-implanted AlGaAs/GaAs multi-quantum well dual waveguides. The impurity induced disordering defined multiquantum well dual waveguides are shown to have similar optical properties as conventional dielectric rib waveguides. They also provide a more flexible control over the waveguiding and coupling characteristics by changing parameters such as diffusion time, ion implant energy, mask width, and waveguide separation.
Atomistic Calculations of Dopant Binding Energies in ZnGeP2
Authors: Pandey Ravindra , Ohmer Melvin C. , Costales A. , Recio J. M.
Published: April 2011

Atomistic model has been applied to study various cation dopants, namely Cu, Ag, B, Al, Ga and In in ZnGeP2. The pairwise interatomic potential terms representing the interaction of dopants with the host lattice ions are derived using first principle methods. Defect calculations based on Mott-Littleton methodology predict small binding energies for Cu and Ag substituting Zn in the lattice which are in agreement with the available experimental data. The group III dopants (i.e. B, Al, Ga and In) at the Ge site are predicted to have large binding energies for a hole except B which shows a distinct behavior. This may be due to large mismatch in atomic sizes of B and Ge. At the Zn site, the calculated binding energies of the group III dopants place donor levels in the middle of the band gap.
Operational Characteristics of GaSe Crystals for Mid-IR and Far-IR Applications
Authors: Fernelius N. C. , Hopkins F. K. , Singh N. B. , Suhre D. , Marable M. , Hopkins R. H. , Meyer R. , Mui P.
Published: April 2011

GaSe has a number of attractive properties for nonlinear optical applications including large birefringence for ease in phase matching. Its biggest drawback is its mechanical properties. GaSe has a strong tendency to cleave along the <100> plane which has made it difficult to grow and fabricate. We have developed a method to modify GaSe by structurally strengthening the material by doping. We have synthesized large boules of GaSe reacted mixtures and grown centimeter size single crystals by the Bridgman technique. Depending on the dopant and crystal quality, SHG measurements indicate a deff, of 51 to 76 pm/V. SHG power levels were theoretically calculated and appear to be in good agreement with the experimental data. The measured performance of crystals for the fourth harmonic generation and laser damage threshold are also reported in this paper. The damage threshold was greater than 2.8 J/cm2 and 85 KW/cm2 at the surface of the crystal.
High Efficiency, Spectroscopic CZT Array
Authors: Cirignano L. , Klugerman M. , Dmitriyev Y. , Bennett P. , Shah K. S. , Bloser P. , Narita T. , Grindlay J.
Published: April 2011

Compact, efficient, spectroscopic detector arrays which preferably operate without cooling have applications in the fields of x-ray astronomy, nuclear medicine and radioactive materials management. We have fabricated a 16 element CdZnTe detector array that provides a stopping efficiency of greater than 80%, a photopeak fraction of 44% and an energy resolution of 3.2 keV FWHM at 122 keV. The 4 × 4 array uses a pixel size of(1.5 mm)2 with 0.2 mm spacing on a 5 mm thick substrate. The variation in spectroscopic properties amongst pixels has been characterized in terms of energy resolution and detection efficiency. Operation in current (or flux) mode for transmission imaging has also been investigated.
Study of the Radiation Damage Induced by High Energy Gamma-Ray in CdTe Detectors
Authors: Chirco P. , Zanarini M. , Querzola E. , Zambelli G. , Dusi W. , Caroli E. , Cavallini A. , Fraboni B. , Siffert P. , Hage-Ali' M.
Published: April 2011

In recent years the performance of room-temperature semiconductor detectors such as CdTe are improved and they are now suitable candidates for several applications. However, some key parameters that can severely affect such perfomances have not been measured yet. Thus we have studied the damaging of a set of CdTe detectors irradiated in a 60Co gamma-cell in a wide range of doses and dose-rates. A full characterization of the performance of irradiated detectors has been obtained by means of spectroscopic, electrostatic, photo-induced current transient spectroscopy and photo-deep level transient spectroscopy measurements to quote the energy resolution, the leakage current, the activation energy and capture cross-section of deep level defects, respectively.
Converting Films for X-Ray Detectors, Applied to Amorphous Silicon Arrays.
Authors: Ross S. , Zentai G.
Published: April 2011

This paper presents results from our on-going efforts to characterize semiconductor thin films for direct x-ray conversion. We deposit these thin films onto an amorphous silicon (a-Si:H) readout array with the overall goal of developing a large area x-ray detector for protein crystallography, and for other x-ray imaging fields.
Degradation and Recovery of Si Diodes by 20-Mev Protons And 220-Mev Carbon Particles
Authors: Hakata T. , Ohyama H. , Simoen E. , Claeys C. , Sunaga H. , Kobayashi K. , Hososhima M.
Published: April 2011

Results are presented of a study on the degradation of the electrical performance of Fe contaminated n+p Si diodes, subjected to a 220-MeV carbon irradiation. The reverse current of the diodes increases after irradiation, while the capacitance and hence the doping concentration decreases. The areal and peripheral components of the leakage current are extracted from diodes with different area to perimeter ratios. Both the generation and the recombination lifetime calculated from I/V and C/V characteristics also decrease. The deep levels in the Si substrate induced by the irradiation are mainly responsible for the degradation of the diode performance. The radiation damage is also studied for 1 -MeV electrons and 1 -MeV fast neutrons. The performance degradation for carbon irradiation is three orders of magnitude larger than that for electron irradiation. The differences in the radiation damage are explained by the differences in the number of knock-on atoms and the nonionizing energy loss (NIEL), which is attributed to the difference of mass and the possibility of nuclear collision with target Si atoms
Influence Of Ti Related Centers On ZnSe Radiation Spectra
Authors: Bruk L.I. , Korotkov V. A. , Ketrush P. I. , Simashkevich A. V. , Sushkevich K. D. , Kulyuk L. L. , Popov S. M. , Malikova L. V.
Published: April 2011

ZnSe annealed in (Zn + 46 wt.% TI) vapors and in Zn melt with 5 wt.% TI addition was investigated. The radiation spectra in the regimes of stationary and pulsed photoluminescence (PL) with the time delaying at 77K were studied. By using coloured cathodoluminescence (CCL) combined with the crystal cleavage image in the secondary electrons reflection the impurities and defects volume distribution was evaluated. It was revealed that at the annealing of ZnSe crystals in TI vapors, the cleavage surface has light blue radiation on the red background with an homogeneous field distribution with the dimensions ˜ 1..10μm. On the edge of the cleavage on the depth of 10μm the region of yellow radiation is observed. At the annealing in the melt the irradiation became blue on a weak red background, the homogeneity enhances. At the room temperature PL spectra correspond with images of cleavage in CCL. In the PL (at 77K) spectra in the exciton region there were observed: bands at 445nm (blue radiation); edge radiation at 460nm, 485nm with the LO phonons replica (blue region) and in the impurity region: bands 500...570nm (yellow-green radiation); 600...700nm and 720...800nm (red radiation). The investigation of PL of the annealed samples surface allowed the suppose, that the bands at 2,76eV (450nm), are stipulated by the free-bound transition on the acceptor center (E + 40meV), including TI.

The comparison of ion and tetrahedronical covalent radiuses of Zn, Se and TI, electronegativity, probability of Zni and Vse. formation at the annealing allowed to suppose that, TI fills Vse. and forms (Zni Tls) and (Vse. Tlse) complexes. The carried out theoretical calculations according to the model of two-atom molecule gives the energy of complexes occurrence (Ev + 0,04) eV and (Ev + 0,8) eV. The first value accordingly is in good agreement with the experimental data.
Low Temperature Processed Metal-Semiconductor-Metal Phtodetectors on ZnSe/SI-GaAs (100)
Authors: Hong Hyesook , Anderson Wayne A. , Lee Eunwha , Chang Huicheng , Na Myunghee , Luo Hong
Published: April 2011

Low temperature (LT) processed ZnSe MSM photodetectors can be used for detecting Gamma rays or X-rays using scintillation crystals in many space and medical applications. Metalsemiconductor-metal (MSM) photodetectors were fabricated on undoped ZnSe grown by molecular beam epitaxy (MBE) on semi-insulating (100) GaAs substrates. The MSM photodetectors consist of interdigitated metal fingers with 2 μm, 3 μm, and 4 μm spacing on one chip. Probimide and SiO2 thin films were deposited to aid the LT lift-off process before the pattern generation. An interdigitated structure was achieved by photolithography and reactive ion etching. Pd Schottky metal was deposited at a substrate temperature near 77 K using a lift-off technique. The LT metallization provides an improved interface between metal and semiconductor interface. Continuous wave signal to noise ratio (SNR) of 1.57×104 was obtained for 2 μm interdigitated photodetectors, operated under 180 nW optical power at a wavelength of 400 nm. The detectors showed good DC saturation characteristics indicating a low surface recombination. Saturation current without illumination remained at around less than 1 pA for a ± 10 V biasing. Detectors exhibited linearity with light intensity and DC bias voltage suggesting no gain mechanism involved, and showed a high spectral responsivity (0.6 (A/W)) at a wavelength of 450 nm at 5V applied bias.
Device Simulation of a Unipolar Gamma-Ray Detector
Authors: Lee E. Y. , Lund J. C. , Hilton N. R. , Brunett B. A. , James R. B.
Published: April 2011

The pulse height spectra from a new kind of unipolar gamma-ray detectors were predicted using a new three-dimensional simulation program developed at Sandia National Laboratories. The detectors were fabricated at Sandia and RMD Inc., and tested at Sandia. They were fabricated from Cd1-x.ZnxTe crystals and they were electron-transport-only devices. For the simulation, a successive overrelaxation method was used to determine the three-dimensional internal electric field within a detector, and to find the weighting potentials for the anode and the cathode. Uniform irradiation and ionization from a 137Cs source was assumed, and the charge transport and the signal induction within the detector were numerically computed using the appropriate materials and design parameters. The simulation gave excellent agreement with experimental pulse height spectra, and it demonstrated the power of such a simulation to correlate the materials parameters and the device design to the actual detector performance.
Growth and Characterization of Pbse and Pbl-Sn1 Se Layers on Si (100)
Authors: Sachar H. K. , Chao I. , Fang X. M. , McCann P. J.
Published: April 2011

Crack-free layers of PbSe were grown on Si (100) by a combination of liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE) techniques. The PbSe layer was grown by LPE on Si (100) using a MBE-grown PbSe/BaF2/CaF2 buffer layer structure. Pb1−xSnxSe layers with tin contents in the liquid growth solution equal to 3%, 5%, 6%, 7%, and 10%, respectively, were also grown by LPE on Si (100) substrates using similar buffer layer structures. The LPE-grown PbSe and Pb1−xSnxSe layers were characterized by optical Nomarski microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Optical Nomarski characterization of the layers revealed their excellent surface morphologies and good growth solution wipe-offs. FTIR transmission experiments showed that the absorption edge of the Pb1−xSnxSe layers shifted to lower energies with increasing tin contents. The PbSe epilayers were also lifted-off from the Si substrate by dissolving the MBE-grown BaF2 buffer layer. SEM micrographs of the cleaved edges revealed that the lifted-off layers formed structures suitable for laser fabrication.
Photoexcitations of Oligothiophenes with Reduced Conformational Mobility
Authors: Rossi L. , Bongiovanni G. , Botta C. , Cerullo G. , Lanzani G. , Mura A. , Sannicolo F. , Benincori T. , Tubino R.
Published: April 2011

We present a comprehensive study of the optical and electronic properties of a series of oligothiophenes in which one or two inter-ring torsional angles have been blocked by chemical bridging. These give us the possibility to investigate the role of the conformational mobility and of the coupling with the inter-ring torsion on the deactivation process of the singlet excited states. We find that both the radiative and the non-radiative deactivation channels are affected by the inter-ring bridging.
Advantages of Modal Dispersion Phase-Matching and Materials Requirements for Polymeric Devices Using Efficient Second Harmonic Generation at Telecommunication Wavelength
Authors: Jäger Matthias L. , Ricci Vincent , Cho Wook-Rae , Canva Michael T. G. , Stegeman George I.
Published: April 2011

Modal Dispersion Phase Matching appears to be currently much better adapted to parametric mixing in polymeric material waveguides than Quasi Phase Matching. For second harmonic generation at telecommunication wavelengths, using organic materials should allow better performance than with ferroelectric crystals. Promising results are expected in view of theoretical expectations and continuously improving experimental past and current results.
Conjugated Polymer Based Nanocomposites for Photonics Applications
Authors: Prasad P. N. , Kumar N. Deepak , Lal Manjari , Joshi Mukesh P.
Published: April 2011

Nanoscale synthesis and processing provides a novel approach for making a new generation of nanocomposite materials with exceptional optical and electrical properties that are needed for the development of new technologies. This presentation will focus on the preparation of nanocomposites made of Poly (para-phenylene vinylene) (PPV) with other polymers, inorganic glasses and semiconductors. We will present a new approach of nanoscale polymerization for making processable monodispersed oligomeric species of PPV which uses the base catalyzed polymerization of PPV monomer within the cavity of a reverse micelle nanoreactor. Application of this approach of fabricating novel materials for a variety of applications in photonics will also be discussed. In addition, we will discuss fabrication of bulk nanocomposites of PPV and silica by insitu polymerization of monomer within a porous glass and their lasing properties.
Electronic Structure and Optical Response of Electroluminescent Conjugated Polymers
Authors: Bredas J. L. , Cornil J. , Beljonne D. , Santos D. A. Dos , Shuaiv Z. , Silbey R.
Published: April 2011

In this contribution, we investigate by means of correlated quantum-chemical calculations the influence of intermolecular interactions on the absorption and emission properties of conjugated chains. Various strategies are suggested to avoid a substantial decrease in fluorescence quantum yield in condensed media. Finally, the reliability of our theoretical approach is validated by showing the remarkable agreement obtained between the experimental data and the calculated optical properties of clusters formed by sexithienyl molecules.
Characterization of Polyparaphenylene Subjected to Different Heat Treatment Temperatures
Authors: Brown S. D. M. , Matthews M. J. , Marucci A. , Pimenta M. A. , Dresselhaus M. S. , Endo M. , Hiraoka T.
Published: April 2011

We investigated the structural and electronic properties of samples of polyparaphenylene (PPP), derived from two synthesis methods (the Kovacic and Yamamoto methods). These samples have been subjected to different heat-treatment temperatures (650 °C ≤ THT ≤ 2000°C) and their properties are compared to the polymer prior to heat-treatment (THT=0°C). The photoluminescence (PL) spectra of heat-treated PPP based on the two synthesis methods reflects the differences in electronic structure of the starting polymers. The PL emission from the heat-treated Yamamoto polymer is quenched at much lower THT than from the Kovacic material. However, Raman spectra taken of the material resulting from heat-treatment of the polymer (using both preparation methods) indicate the presence of phonon modes for PPP in samples at THT up to 650°C.
Optical Properties of Distyrylbenzene Chromophores and their Segmented Copolymers
Authors: Benfaremo Nicholas , Sandman Daniel J. , Tripathy Sukant , Kumar Jayant , Yang Ke , Rubner Michael F. , Lyons Cormac
Published: April 2011

A new segmented polymer (3) consisting of a distyrylbenzene chromophore separated by polyethylene glycol segments has been prepared by two independent methods: a novel, polymer analogous Mitsunobu reaction and conventional double displacement reaction. The polymer is soluble in a variety of organic solvents, forms excellent, optically clear films and exhibits strong fluorescence. The properties of the chromophore and the polymer, as well as the scope and limitations of the novel Mitsonobu polymerization are presented. Attempts to use polymer (3) in electroluminescent devices are also discussed.
Concentration Dependence of Photoluminescence and Electroluminescence in 2,5 Bis[2'-(4”-Hydroxyhexanol Benzyl)-l'-Ethyl]3,4-Dibutyl Thiophenes
Authors: Blumstengel S. , Sokolik I. , Dorsinville R. , Voloschenko D. , He M. , Chien L.-C. , Lavrentovich O.
Published: April 2011

A new thiophene-based compound 2,5 bis[2'-(4”-hydroxyhexanol benzyl)-l'-ethyl]3,4-dibutyl thiophene (HBDT) as well as a copolymer (HBDT-PU) consisting of alternating HBDT and urethane spacer units were synthesized. Absorption and luminescence properties of both compounds were studied in solution and in different polymer matrices. Absorption and luminescence spectra of HBDT and HBDT-PU coincide indicating that emission in HBDT-PU occurs from the thiopene containing unit. Photoluminescence (PL) is emitted in the blue-green region of the visible spectrum with a maximum at 460 nm. The PL efficiency of both compounds is strongly enhanced when dispersed in a PVK or PMMA matrix indicating that concentration quenching occurs in the pure material. Light emitting devices were fabricated utilizing a PVK/PBD blend doped with HBDT and HBDT-PU at different concentrations as emitter material. The electroluminescence (EL) spectra coincided with the PL spectra of HBDT indicating that EL emission originates from the dopant molecules. The dependence of the EL efficiency on the doping concentration was measured and found to be close to the concentration dependence of the PL quantum yield.
Control of Emissive Layer Interfaces with Inorganic Thin Layer Between 8-Hydroxyquinoline Aluminum and Diamine Layers in Organic El Diode
Authors: Ohmori Yutaka , Kurosaka Yoshitaka , Tada Norio , Fujii Akihiko , Yoshino Katsumi
Published: April 2011

Control of organic interfaces by insertion of a thin inorganic film (SiO) has been investigated for an organic electroluminescent (EL) diode which consists of 8-hydroxyquinoline aluminum (Alq3) and diamine derivative (TPD). In order to evaluate optical quality of the emissive layer at the interface, thin film of emissive marker layer was inserted into the emissive layer at the interface between the emissive layer and the carrier transport layer. The EL emission spectrum and the optical characteristics have been discussed for the EL diode with and without inorganic film.
Latex-Like Water-Borne Polyaniline for Coating Applications
Authors: Liu Huaibing , Clark Robert , Yang Sze C.
Published: April 2011

We report the synthesis of a polymeric complex of polyaniline that is dispersed in water as a stable suspension. The polymer, PAN:PVME-MLA, is a molecular complex of polyaniline and poly(vinylmethylether-co-maleic acid). The synthetic process leads to a stable latex-like suspension in water. The water-borne conducting polymer, once dried as a thin film on a substrate, is not dissolvable by water or other solvents. An example of piece-dyeing process is presented to show its potential for electrostatic dissipation of textile products. Another example illustrates that the material may be used as electroactive thin-films for electrochromic windows and for rechargeable battery applications.
Structural Properties Of Hexaphenyl Powder Under High Pressure
Authors: Guha S. , Graupner W. , Resel R. , Chandrasekhar M. , Chandrasekhar H. R. , Leising G.
Published: April 2011

We present X-ray and Raman studies of the conjugated oligomer, hexaphenyl, which forms polycrystalline layers. The Raman studies have been carried out under hydrostatic pressures up to 70 kbar. The relative intensity of the two modes at 1220 cm−1 and 1280 cm−1 shows the influence of planarization under hydrostatic pressure. These results are interpreted within the framework of theoretical calculations and compared with X-ray studies.
Electrical and Microwave Properties of Mn Implanted (Ba,Sr)TiO3 Thin Films
Authors: Baniecki J. D. , Laibowitz R. B. , Shaw T. M. , Duncombe P. R. , Neumayer D. A. , Cope M. , Kotecki D.E , Shen H. , Ma Q. Y.
Published: April 2011

We have used ion implantation to dope polycrystalline BaxSr(1−x)TiO3 (BST) thin films with Mn. Dopant concentrations were varied in the range of 0.1 at % to 2 at % Mn. X-ray diffraction and TEM studies show that the implantation process significantly damages the film leaving only short range order, but subsequent rapid thermal annealing heals the damage. The effect of the different Mn dopant concentrations on the electrical properties of the complex capacitance, relaxation currents, leakage, C-V, and resistance degradation was investigated. Our initial results show that the implanted films have significantly lower leakage (up to a factor of 10 lower) than the as deposited films for small (<0.5 at % Mn) implantation doses. The capacitance decreased with increasing Mn concentration while the relaxation currents and loss tangents increased.
Study of KTN Thin Films of Variable Composition grown by Pulsed Laser Deposition
Authors: Fernandez F. E. , Pumarol M. , Marrero P. , Rodriguez E. , Mourad H. A.
Published: April 2011

Potassium niobate tantalate (KTN) thin films of a range of compositions were grown by pulsed laser deposition onto (100) MgO substrates. Three-segment targets were used including KTaO3, KNbO3, and KNO3. Resulting films were well oriented with the substrates, with the “cubic” (h00) peaks positions shifting with Nb content to that of the (hh0) orthorhombic KNbO3 peak.
Thickness Mode Resonance of PZT Coatings on a Substrate
Authors: Lukacs M. , Olding T. , Sayer M. , Sherrit S.
Published: April 2011

The analytical solution of the wave equation for a piezoelectric layer supported by a substrate is presented. Using the appropriate boundary conditions, the impedance for a piezoelectric layer driven in the thickness axis is derived and expressed in terms of the mechanical, electrical and piezoelectrical properties of the two materials. This solution allows for the extension of the free resonator IEEE impedance techniques and provides a nondestructive method for determining the material parameters of a piezoelectric film with mechanical support. The validity and universality of the model is demonstrated by measurements on composite sol gel PZT coatings within the thickness range of 15-70μm on aluminum substrates of varying thickness, and by simulating the mass loading of a quartz thickness resonator.
Properties of PTO/YBCO Heterostructure on Bare SiC Substrates
Authors: Duan M. , Linnros J. , Petersson C. S. , Rao K. V.
Published: April 2011

The lead titanium oxide PbTiO3 (PTO) and High Tc Superconductor YBa2Cu3O7-x (YBCO) capacitor hetero structures have been fabricated by pulsed laser ablation directly on 3C-SiC substrates. X-ray diffraction analysis indicates that both PTO layer and YBCO layer are polycrystalline with a perovskite phase. The zero-field cooling (ZFC) curve of YBCO shows a transition temperature Tc around 60 K with a ΔTc ≈ 10 K in a dc SQUID measurement. The ferroelectric properties of the capacitors were characterized by a RT66A apparatus.
High-Resolution Optical Microscopy Of BaXSr1−xTio3 Films
Authors: Hubert C. , Levy J. , Carter A. C. , Chang W. , Pond J. M. , Horwitz J. S. , Chrisey D. B.
Published: April 2011

The ferroelectric polarization of thin films of BaxSr1−xTiO3 is imaged using confocal scanning optical microscopy (CSOM). The thin films are grown by pulsed laser deposition (PLD) on SrTiO3 substrates. Ferroelectric domain structure is imaged by applying a small ac electric field across interdigitated electrodes, and measuring induced reflectivity changes in the film, which are directly related to the polarization. Domain re-orientation is observed by acquiring CSOM images as a function of the dc electric field. Local hysteresis loops are obtained by sweeping the dc electric field at fixed positions on the sample. Micrometer-sized regions exhibit both ferroelectric and paraelectric response, indicating that thermal broadening of the phase transition is largely due to inhomogeneities in the thin films.