bluuebunny/crossref_metadata_2025 huggingface dataset:
An Examination of Mass Transport Paths in Conventional and Highly Textured AL-CU Interconnect Lines
Authors: Gleixner R. J. , Kanekof H. , Matsuot M. , Toyodat H. , Nix W. D.
Published: April 2011

The electromigration lifetime of aluminum interconnect lines shows a strong dependence on the quality of the texture in the metal. This observation has been explained in terms of a decreased diffusivity along the grain boundaries, generally the dominant path for diffusion and void growth. As the texture in the metal is strengthened, atomic order along the grain boundaries is increased, and diffusion is suppressed.

In this paper, we examine passivated A1–0.5wt%Cu interconnect lines having either TaAl underlayers or conventional Ti/TiN underlayers. Rocking curve measurements confirm that Al deposited on TaAl has a very strong (111) texture (FWHM ∼ 0.6°) compared to Al on Ti/TiN (FWHM ∼ 6°). Interconnect lines of both types were electrically stressed at 225°C and 250°C for 20 hours at a current density of 3 MA/cm2. The lines were then stripped of passivation, and the void numbers, sizes, and morphologies were determined.

Analysis of the void data gave a surprising result: the void volume in the highly-textured Al was greater than in the conventional Al. However, voids in the conventional Al were observed to follow grain boundaries across the width and sever the line, while such destructive void growth was not observed in the highly-textured Al. Instead, voids grew either with a faceted shape or along the line edge, never extending across the line width. Modeling electromigration in the surrounding microstructures shows that void locations in the highly-textured lines are often independent of the surrounding grain boundaries. In this case, the line sidewalls appear to be significant mass transport paths. Since these paths do not cross the line width, voids growth across the line is difficult. This resistance to fatal damage makes highly textured aluminum a promising interconnect material.
Microstructural Identification of SiNx Films by Real-Time Ellipsometry
Authors: Soto G. , Samano E. C. , Machorro R. , Avalos M. , Cota L.
Published: April 2011

Real-time ellipsometry has shown to be a powerful tool to analyze thin films during processing. It is non-disturbing and its sensitivity lies in the submonolayer range. In fact, a slight variation in the film microstructure might result in a significant change of the polarization state of the reflected beam from the sample surface. SiNx layers have been grown on glass, quartz, KC1 and Si substrates by laser ablating a Si3N4 sintered target in vacuum and N2 environment. The film growth was monitored by real time ellipsometry at a fixed wavelength, and a fixed incidence angle. Once the deposition process is completed, the refractive index was obtained by perfoming in situ spectroellipsometric measurements in the 1.5 to 5 eV photon-energy range. The best curve fitting of the experimental data is used to find the film composition: a mixture of Si3N4, polycrystalline Si, and amorphous Si. The films composition and micro structure inferred from ellipsometric data are compared to those obtained by in-situ surface techniques and TEM, respectively.
The Recrystallization Properties of Poly-GexSi1-xON SiO2/Si
Authors: Jiang N. , Ma J.R. , Wu M. , Huang X.D. , Gu S.L. , Yu S.D. , Hu L.Q. , Zheng Y.D.
Published: April 2011

In this paper, we have developed a new way to recrystallize the poly-GeSi on SiO2. 300nm poly-GeSi was grown by RTP/VLP-CVD on SiO2/Si, and then amorphized by 180 keV-Si+ ion implantation with dose of 2×10'4 cm'2. An amorphized region with the damage distribution was formed. After subsequent annealing process, the comparison between the XRD scans and Raman spectra of poly-GeSi and poly-Si indicated that the annealed poly-GeSi was more recrystallized than the poly-Si in the same conditions, this was the inducement of Ge in the annealing process. The segregation of Ge atoms in the heavy damaged region would enhance this inducement. The XTEM showed the longitudinal pattern of GeSi grains which meant the longitudinal sizes were much greater than the horizontal sizes. After annealing process, the final GeSi grain sizes were greater than the poly-Si grain sizes processed in SSIC with the same implantation conditions.
Ferroelectric Properties and Crystalline Structures of BaMgF4 Thin Films Grown on Pt(111)/SiO2/Si(100)
Authors: Moriwaki Masashi , Aizawa Koji , Tokumitsu Eisuke , Ishiwara Hiroshi
Published: April 2011

Crystalline quality and ferroelectric properties of (120)-oriented BaMgF^BMF) films grown on Pt(111)/SiO2/Si(100) and n-Si(111) substrates have been investigated. The BaMgF4 films grown on Pt(111) have large and flat grains, while the films on Si(111) have small grains. The C-V curve of BaMgF4/Pt(111)/SiO2/Si(100) diodes showed a hysteresis loop with a memory window of 3.8V.
Organic Contamination of Silicon Wafer in Clean Room Air and its
Impact to Gate Oxide Integrity
Authors: Imafuku D. , Mizubayashi W. , Miyazaki S. , Hirose M. , Wakayama Y. , Kobayashi S.
Published: April 2011

Organic adsorbates on silicon wafer surfaces exposed to superclean room air
were measured to evaluate organic contamination level of silicon wafers
stored in a clean bench up to 180min. Such Si wafers were thermally oxidized
and the dielectric degradation behavior were systematically investigated. It
is found that a carbon contamination level of half a monolayer influences
the charge to quasi-breakdown although the degradation mechanism itself
remains unchanged.
Study on the effect of Silicon surface cleaning processes on
Gate Oxide Integrity
Authors: Corradi A. , Borzoni E. , Godio P. , Borionetti G.
Published: April 2011

The effect of different silicon wafer surface preparation in modulating gate
oxide quality performance has been studied through an experimental design
which examines key phases of wafer cleaning and polishing processes. An
interpretation of the root causes of GOI degradation has been
proposed and discussed.
Understanding the Correlation of SurfaceSIMS and TXRF
Measurements of Surface Metal Contamination on Silicon
Wafers
Authors: Smith Stephen P. , Metz Jenny
Published: April 2011

A comparison of SurfaceSIMS measurements of surface metal contamination on
silicon wafers with TXRF analyses of the same wafers is presented. These two
important surface analysis techniques are characterized by differing
analytical areas and sampling depths. For Fe, agreement between SurfaceSIMS
and TXRF results is good (generally within a factor of two) for silicon
wafers from a variety of sources with contamination levels ranging from
8×109 to 2×1015 atoms/cm2. Differences
between SurfaceSIMS and TXRF results occur for other elements (such as W and
Cu) when the contamination is not uniform across the surface of the wafer
(particles are present), or extends a significant depth below the surface of
the wafer (as is frequently the case for ion-implanted wafers).
Acceleration of Organic Contaminant Adsorption Onto Silicon
Surfaces in the Presence of Residual Fluorine
Authors: Saga Koichiro , Hattori Takeshi
Published: April 2011

The influence of fluorine atoms remaining after HF treatment on the
adsorption of organic contaminants onto the surface of silicon wafers was
investigated by analyzing the organic contaminants with gas
chromatography-mass spectrometry following thermodesorption (TDGC/MS), and
the surface composition with X-ray photoelectron spectroscopy (XPS). It has
been found that residual fluorine on silicon surfaces after cleaning of the
silicon wafers with either aqueous HF or anhydrous HF accelerates the
adsorption of organic contamination onto the silicon surfaces. This would be
due to the electrostatic force of attraction between the polar groups of
organic compounds and the residual fluorine on the silicon surface.
Detection of Low-Level Copper-Contamination on Silicon Surfaces
by Drop Nucleation
Authors: Lee Thomas D. , Spaepen Frans , Golovchenko Jene A.
Published: April 2011

Nucleation and growth of liquid drops from the vapor can be used to locate
efficiently surface inhomogeneities such as topological defects, oxide
patches, metallic impurities, organic contamination, and particles. In this
study, nucleation of water drops was used to investigate the surfaces of
copper-contaminated silicon substrates. Hydrogen-terminated silicon (111)
substrates were dipped into copper-contaminated ultrapure water and exposed
to supersaturated water vapor. The amount of copper deposited was varied by
changing the strength of the solution. Nucleation occurred at vapor
pressures close to saturation. Higher densities of nucleated drops appeared
on areas with greater concentrations of copper. Using this technique, it was
possible to detect copper concentrations as low as 6×1011
atom/cm2. Below this concentration, treated and untreated
substrates could not be distinguished. The extreme sensitivity of the
technique to background nucleants shows its potential for efficient
screening of surfaces for a large range of inhomogeneities.
Improved Rinse Quench for a more Uniform Etch of Thermal Oxide
in Buffered Oxide Etch (BOE)
Authors: Parry T. B.
Published: April 2011

An improved method for quenching a Buffered Oxide Etch (BOE) process in a DI
water overflow rinse tank is shown. Many different factors were investigated
in several preliminary experiments. Most of these factors were thought to
influence etch uniformity yet proved not to be significant. The transfer
process from chemical to rinse was identified as contributing negatively to
etch uniformity. A chemical carryover layer formed during the transfer
process was identified as the most significant factor. The hydrodynamics of
liquids are outlined to help explain how the carryover layer is formed and
shaped. Several sensitivity analysis experiments show transfer speeds to
significantly affect carryover layer thickness and uniformity. Slow transfer
speeds are determined to produce consistent and improved uniformity. Results
of a follow up experiment quantify the uniformity improvement.
Impact of Metal Contamination of 7.0nm Gate Oxides on Various
Substrate Materials
Authors: Saito S. , Hamada K. , Eaglesham D. J. , Shiramizu Y. , Benton J. L. , Kitajima H. , Jacobson S. D. C. , Poate J. M.
Published: April 2011

Metal contamination level will be decreased in order to maintain a device
reliability according to device size reduction. Metal contamination from
various processes are surveyed. The influence of metal contamination for
7–15nm thick gate oxides is discussed in order to clarify the critical
concentration to gate oxides. NIG(Non Intrinsic Gettering) substrates are
used in a worst case for gettering. Fe contamination with 4×1010
cm−2 strongly affects the TDDM characteristics, although there
is no serious influence in the breakdown voltage even at the concentration
of 5×1011 cm−2. The same tendency is observed for Cu
contaminant and the critical concentration for TDDB characteristics is
around 3×1011 cm−2. High energy B implantation is
carried out to form gettering sites near device region. Breakdown voltage
and TDDB characteristics are almost the same as epitaxial substrates at Fe
concentration up to l×1012 Cm−2. Detailed examination
such as SIMS, C-t and DLTS measurements is also supported the effectiveness
in high energy gettering.
Thermoelectric Transport in Superlattices
Authors: Reinecke T. L. , Broido D. A.
Published: April 2011

The thermoelectric transport properties of superlattices have been studied using an exact solution of the Boltzmann equation. The role of heat transport along the barrier layers, of carrier tunneling through the barriers, of valley degeneracy and of the well width and energy dependences of the carrier-phonon scattering rates on the thermoelectric figure of merit are given. Calculations are given for Bi2Te3 and for PbTe, and the results of recent experiments are discussed.
Optimization of Materials for Thermomagnetic Cooling
Authors: Migliori A. , Darling T. W. , Freibert F. , Trugman S. A. , Moshopoulou E. , Sarrao J. L.
Published: April 2011

We review thermoelectric transport in a magnetic field. The key physical effect for thermomagnetic cooling is the Ettingshausen effect. We describe the design principles, measurement difficulties and areas where more work can prove fruitful in an exploration of cryogenic refrigeration based on this effect. New principles are discussed to guide the search for new materials and their development.
unneling effects in InAs/GaInSb superlattice infrared photodiodes
Authors: Weimar U. , Fuchs F. , Ahlswede E. , Schmitz J. , Pletschen W. , Herres N. , Walther M.
Published: April 2011

The optical and electrical properties of InAs/GaInSb superlattice mesa photodiodes with a cutoff wavelength around 8 pim are investigated. The influence of the surface potential at the mesa sidewalls on the device properties was studied by fabricating gate-controlled diodes. At least two mechanisms determining the dark current in the reverse bias region can be identified. At high reverse biases bulk bandto- band tunneling dominates while the current at low reverse biases is most likely governed by surface effects. Bulk interband tunneling is further investigated by applying magnetic fields B up to 7 T parallel and perpendicular to the electric field E across the p-n junction.
Novel Piezoelectric Heterostructure for all-Optical Infrared Light Modulation
Authors: Ortiz V. , Pelekanos N. T. , Mula Guido
Published: April 2011

We present an innovative-design heterostructure based on the exploitation of in-the-barrier piezoelectric field for all-optical light modulation. The novel layout allows an efficient light modulation with low power densities (few tens of W/cm2), easily attainable with standard laser diodes. The modulation mechanism relies upon drastic photocarrier separation by the piezoelectric field in the barrier layers. We present room temperature results showing that an optical “control” power of 70 W/cm2 creates in the heart of the structure a space-charge field of about 30 kV/cm, inducing large spectral shifts (∼100 nm) in the photoluminescence spectra of a CdHgTe quantum well in the 1.5 μm range.
Er-Related Emission In Impurities (Nitrogen, Oxygen) Implanted Al0.7Ga0.3As
Authors: Uekusa S. , Wakutani M. , Saito M. , Kumagai M.
Published: April 2011

Erbium (Er) was co-implanted with ( i ) nitrogen (N), ( ii) oxygen (0) and (iii) N and 0 into Al0.7Ga0.3As substrates. Compared with the Al0.7Ga0.3As:Er sample, the 20 K Er3+ -related 1.54 μm integrated photoluminescence (PL) intensity from the Al0 7Ga0.3As:Er,N and Al0.7Ga0.3As:Er,N,O samples were enhanced approximately fifteen and ten times more, respectively. Thermal quenching of Er3+-related emission from Al0.7Ga0.3As:Er,N,O was smaller than that of Er3+-related emission from Al0.7.Ga0.3As-Er,N The 20 K Er3+-related 0.98 μm PL which was radiated by transition from the second excited state (4I1/2) to the ground state (4I1/2) was observed. The 0.98 μm PL intensity from Al0.7Ga0.3As:Er,N,O generally decreased with increasing 0 dosage from 1 × 1013 cm−2 to 1 × 1015 cm−2. These results suggest the formation of different complexes composed of Er and the impurities (N,O). This leads to the generation of complex related traps in the band-gap of Al0.7Ga0.3As as a result of the co-implantation of the impurities. It was found that the trap level of the Er-N complex center lay between 2.05 eV and 1.26 eV, and that of the Er-N-O complex center lay between 1.26 eV and 0.82 eV.
Study of the Homogeneity of Fe-Doped Semiinsulating InP Wafers
Authors: Jimenez J. , Fornar R. , Curti M. , de la Puente E. , Avella M. , Sanz L. F. , Gonzalez M. A. , Alvarez A.
Published: April 2011

The homogeneity of semiinsulating Fe-doped InP wafers is studied using mapping techniques, Scanning Photocurrent (SPC) and Scanning Photoluminescence (SPL). These techniques allow to map with a micrometric spatial resolution the distribution of electrically active levels, in particular substitutional iron levels, Fe2+ and Fe3+. The correlation between both measurements allows to obtain information about the local compensation in terms of the [Fe3++Fe2+]/[Fe2+] ratio. Samples thermally treated were studied in order to analyse the consequences of the annealing on the homogeneity.
γ-Ray Irradiation Effect on the Intersubband Transition in Ingaas/Aigaas Multiple Quantum Wells
Authors: Manasreh M. O. , Chavez J. R. , Kemp W. T. , Hoenshel K. , Missous M.
Published: April 2011

Intersubband transitions in n-type InGaAs/AlGaAs multiple quantum wells were studied as a function of 1.0 to 5.0 MRad γ-ray irradiation dose using the optical absorption technique. The spectra were recorded at both 295 and 77K. The results show that the total integrated area of the intersubband transition is decreased as the irradiation dose is increased. This could be explained as follows: The secondary electrons generated from the γ-ray irradiation cause lattice damages where traps and point defects are created. Some of the electrons in the quantum wells are trapped by these defects causing the two dimensional electron gas (2DEG) density to decrease. The reduction of the 2DEG density thus leads to the reduction of the total integrated area of the intersubband transitions.
1.95 μm Compressively Strained Ingaas/Ingaasp Quantum Well DFB Laser With Low Threshold
Authors: Dong Jie , Ubukata Akinoi , Matsumoto Koh
Published: April 2011

In this study, we demonstrate the growth of highly compressively strained InGaAs/JnGaAsP quantum well structures with large well thiclmess by low pressure metalorganic chemical vapor deposition for extending the emission wavelength of lasers. By comparing the photolumineswnce characteristics of quantum wells grown at different temperatures, it is clarified that a relatively high quality quantum well layer emittig at 2.0 μ, can be obtained at a growth temperature of 650°C. 1.95-μm-wavelength InGaAs/InGaAsP highly compressively strained quantum well DFB laser for laser spectroscopy monitors was also fabricated. Double quantum-well DFB laser operating at 1.95 μm exhibits threshold currents as low as 6 mA and 6.2 mW maximum output powers. 2.04-μm-wavelength DFB laser is also described.
Optical Absorption In Hg1−xCdxTe
Authors: Nathan Vaidya
Published: April 2011

The theory of optical absorption due to interband transitions in direct-gap semiconductors is revisited. A new analytical expression for linear absorption coefficient in narrow-gap semiconductors is obtained by including the nonparabolic band structure due to Keldysh and Burstein-Moss shift. Numerical results are obtained for Hg1−xCdxTe for several values of x and temperature, and compared with recent experimental data. The agreement is found to be good.
An imaging CdZnTe detector with coplanar orthogonal anode strips
Authors: Hamel L. A. , Tousignant O. , Couillard M. , Courville J. F. , Jordanov V. T. , Macri J. R. , Larson K. , Mayer M. , McConnell M. L. , Ryan J. M.
Published: April 2011

A novel electrode configuration for CZT imaging devices is presented. It is made of focusing, non-collecting anode strips, in one dimension, and collecting anode pixels, interconnected in rows, in the orthogonal dimension. The simulation of such an imaging detector is presented. First, field lines in the detector are computed that show that electrons generated in γ-ray events are collected on the pixels. Charge signals, induced on the pixel and on the strip by drifting electrons, are calculated for several points of interaction inside the detector unit cell. These show that this new detector should retain the spectroscopic and detection efficiency advantages of single carrier (electrons) charge sensing devices such as pixel detectors or spectrometers with controlling electrodes. Furthermore, it retains the main advantage of conventional strip detectors, i.e. an N x N array of imaging pixels realized with only 2N electronic channels. An additional potential advantage is the measurement of the third coordinate, i.e. the depth of interaction in the detector.
Towards Imaging with Polycrystalline Mercuric Iodide Semiconductor Detectors
Authors: Schieber M. , Zuck A. , Braiman M. , Melekhov L. , Nissenbaum J. , Turchetta R. , Dulinski W. , Husson D. , Riester J. L. , Schlesinger T. E. , Toney J. , Sanguinetti S. , Montalti M. , Guzzi M.
Published: April 2011

Preparation of polycrystalline mercuric iodide very thin (1 μm) films using laser ablation and thick films (100–600μm), using hot pressing, hot wall vapor deposition and screen printing methods, fabricated as radiation detector plates are briefly described. X-ray diffraction, photoluminescence and optical microscopic measurements as well as response to nuclear radiation will be given. Finally, recent results obtained with a large area imaging pixel detector will be shown.
Analysis of Grain Boundaries, Twin Boundaries and Te Precipitates in Cd1−xZnxTe Grown bY High-Pressure Bridgman Method
Authors: Heffelfinger J. R. , Medlin D. L. , James R. B.
Published: April 2011

Grain boundaries and twin boundaries in commercial Cd1−xZnxTe, which is prepared by a high-pressure Bridgeman technique, have been investigated with transmission electron microscopy, scanning electron microscopy, infrared-light microscopy and visible-light microscopy. Boundaries inside these materials were found to be decorated with Te precipitates. The shape and local density of the precipitates were found to depend on the particular boundary. For precipitates that decorate grain boundaries, their microstructure was found to consist of a single, saucer-shaped grain of hexagonal Te (space group P3121). Analysis of a Te precipate by selected-area diffraction revealed the Te to be aligned with the surrounding Cd1−xZnxTe grains. This alignment was found to match the (111) Cd1−xZnxTe planes with the (0111) planes of hexagonal Te. Crystallographic alignments between the Cd1−xZnxTe grains were also observed for a high-angle grain boundary. The structures of the grain boundaries and the Te/C1−xZnxTe interface are discussed.
Amorphous Silicon Sensor Arrays for X-Ray and Document Imaging
Authors: Street R. A. , Apte R. B. , Ready S. E. , Weisfield R. L. , Nylen P.
Published: April 2011

Large area amorphous silicon image sensor arrays are important for x-ray medical imaging and document scanning as well as a variety of other applications where large sensor size is required. The paper first summarizes the present state of the flat panel x-ray imager technology, and compares the two main approaches for x-ray detection. We then describe the performance of a new, large area, high resolution, radiographic imager based on a single amorphous silicon array with 2304×3200 pixels, and an active area of 30×40 cm (12×1 6”).
Radiation Damage in Si Avalanche Photodiodes by 1-Mev Fast Neutrons and 220-Mev Carbon Particles
Authors: Ohyama H. , Hakata T. , Simoen E. , Claeys C. , Takami Y. , Hayama K. , Tokuyama J. , Shigaki K. , Kobayashi K. , Sunaga H. , Miyahara K. , Hososhima M.
Published: April 2011

Results are presented of a study on the degradation of the electrical and optical performance of n+p Si avalanche photodiodes, subjected to 1-MeV fast neutrons and to a 220-MeV carbon irradiation. The dark current increases after irradiation, while the photo current decreases. Two dominant hole capture levels, which are responsible for the degradation of performance, are after irradiation observed by DLTS (Deep Level Transient Spectroscopy). The degradation caused by neutron irradiation is smaller than that for carbon 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). The recovery behavior of the device performance by isochronal annealing is also reported.
Photoluminescence And The Optimum Growth Conditions Of High Quality ZnS Epitaxial Layers
Authors: Nam Sungun , Rhee Jongkwang , Yu Young-Moon , O Byungsung , Lee Ki-Seon , Choi Y. D. , Yun H. J. , Kim Chang Soo , Jung Yang-June
Published: April 2011

High quality ZnS epilayers were grown on GaAs and GaP substrates by hot wall epitaxy. The optimum temperature conditions for high quality ZnS epilayer were found. The photoluminescence(PL) spectrum of high quality ZnS epilayers showed sharp and narrow exciton peaks and no self-activated peaks. The room temperature energy gap of ZnS/GaAs was found to be 3.729 eV from the experimentally observed free exciton PL peaks. The temperature dependence of the PL intensity showed a two step quenching process and the temperature dependence of the PL linewidth broadening was tried to analyze in terms of exciton scattering process. From the splitting of the heavy hole and the light hole exciton peaks, the strain was identified.
Optical Studies of the Internal Electric Field Distributions of CdZnTe Detectors Under Bias Conditions
Authors: Yao H. W. , Anderson R. J. , James R. B. , Olsen R. W.
Published: April 2011

The internal electric field distributions of the CdZnTe (CZT) detectors under bias were characterized by optical polarized transmission at a 952 nm illumination utilizing the Pockels electro-optic effect. Two-dimensional (2D) images mapping the internal electrical field intensity changes were obtained to study the performance of CZT room-temperature radiation detectors. Planar and a P-I-N structured CZT detectors were investigated under different operating bias voltages. Analysis of optical profiles from a planar single crystal detector provides a quantitative nondestructive description of the electric field or voltage distributions inside a radiation detector. The P-I-N structured CZT detector showed a nearly uniform electric field in a width which varied with the operating bias voltage. An energyband model of a semiconductor junction with a depletion layer was employed to understand the results.
Reactive Ion Etching (RIE) Induced p- to n-Type Conversion in Extrinsically Doped P-Type hgcdte
Authors: Musca C. A. , Smith E. P. G. , Siliquini J. F. , Dell J. M. , Antoszewski J. , Piotrowski J. , Faraone L.
Published: April 2011

Mercury annealing of reactive ion etching (RIE) induced p- to n-type conversion in extrinsically doped p-type epitaxial layers of HgCdTe (x=0.31) has been used to reconvert n-type conversion sustained during RIE processing. For the RIE processing conditions used (400mT, CH4/H2, 90 W) p- to n-type conversion was observed using laser beam induced current (LBIC) measurements. After a sealed tube mercury anneal at 200°C for 17 hours, LBIC measurements clearly indicated no n-type converted region remained. Subsequent Hall measurements confirmed that the material consisted of a p-type layer, with electrical properties equivalent to that of the initial as-grown wafer (NA-ND=2× 1016 cm−3, μ=350 cm2.V−1.−1).
Direct Measurement of Electron Drift Parameters using Depth Sensing Single Carrier CdZnTe Detectors
Authors: He Z. , Knoll G. F. , Wehe D. K. , Du Y. F.
Published: April 2011

This paper describes some novel techniques developed for directly measuring the electron mobility μe and mean free drift time Te in wide band gap semiconductors. These methods are based on a newly-developed digital data analysis system, in conjunction with single carrier charge sensing and depth sensing techniques. Compared with conventional methods, the new techniques are easier to implement, do not involve curve fitting, allow the use of high energy γ-rays and are not sensitive to variations in pulse rise time.
Polymeric Zinc-Bisquinoline Based Self-Assembled Light Emitting Diodes
Authors: Papadimitrakopoulos F. , Thomsen D. L. , Higginson K. A.
Published: April 2011

Bifunctional 8,8'-dihydroxy-5,5'-biquinoline (bisquinoline) is reactively self-assembled with diethyl zinc to form a linear coordination polymer. The potential of this method to produce insoluble and intractable structures of controllable supramolecular architecture suitable for semiconducting applications has stimulated an in-depth investigation of the growth mechanism of these polymeric chelates. These films were characterized by FTIR, UV/VIS and photoluminescence spectroscopy. The film growth on glass or indium-tin oxide (ITO) coated substrates was monitored by UV/VIS spectroscopy and ellipsometry. FTIR spectroscopy indicates that the self-assembled films are polymeric in nature. Single layer light emitting diodes exhibited an orange electroluminescence, consistent with the corresponding photoluminescence spectrum
Modulation of the Electronic Properties in Polydithienotiiophene Materials
Authors: Arbizzani C. , Catellani M. , Luzzati S. , Mastragostino M.
Published: April 2011

Conjugated polymers with narrow band gap are promising candidates for symmetric electrochemical devices, such as electrochromics and redox supercapacitors, which involve the pand n-doped state of the polymer. Polydithienothiophene materials which are prepared from isomer monomers show this characteristic. The copolymerisation of two dithienothiophene isomers leads to materials whose electronic properties depend on the monomer ratio. Optical and electrochemical characterizations of different copolymers are reported and discussed.
Electronic Structure of the Organic Metals κ-Et2cu(SCN)2 and κ-Et2cu[N(Cn)2]Br Measured by Soft X-Ray Emission and Soft X-Ray Absorption
Authors: Stagarescu Cristian B. , Duda L.-C. , Smith Kevin E. , Guo J. H. , Nordgren J. , Haddon R. , Brooks J. S. , Jeromé D.
Published: April 2011

The electronic structure of the two organic, layered metals κ-ET2Cu(SCN)2 and K-ET 2Cu[N(CN)2]Br has been studied using a combination of soft X-ray emission (SXE) and soft X-ray absorption (SXA) spectroscopy. These techniques are powerful probes of the site and angular-momentum resolved partial density of states (PDOS) for both occupied and unoccupied states. Therefore these spectroscopies are particularly suited for an analysis of the density of states of multi-atomic, complex materials as the ET-based organic conductors, allowing site-specific electronic structure to be measured. Furthermore, for certain materials, the electronic structure of specific layers can be measured. We present a preliminary picture of the electronic structure of κ-ET 2Cu(SCN)2 and κ-ET 2Cu[N(CN)2]Br as measured by SXE and SXA performed at the C-Is and N- Is core levels.
Low Pressure Organic Vapor Phase Deposition of Small Molecular Weight Organic Device Structures
Authors: Baldo M. , Kozlov V. G. , Burrows P. E. , Forrest S. R. , Ban V. S. , Koene B. , Thompson M. E.
Published: April 2011

A new technique for the deposition of amorphous organic thin films, low pressure organic vapor phase deposition (LP-OVPD), was used to fabricate organic light emitting devices (OLEDs) and optically pumped organic lasers. The OLED consisted of a film of aluminum tris- (8 hydroxyquinoline) (Alq3) grown on the surface of a film of N'-diphenyl-N,N'-bis(3- methylphenyl)1–l'biphenyl-4–4'diamine (TPD). Growth on both glass and polyester substrates was accomplished and the resulting heterojunction devices were found to have a performance similar to conventional, small molecular weight OLEDs grown using thermal evaporation in vacuum. The LP-OVPD grown OLED has an external quantum efficiency of 0.40 ± 0.05% and a turn-on voltage of approximately 6V. The optically pumped organic laser consisted of a film of Alq3 doped with the laser dye, benzoic acid, 2-[6-(ethylamino)-3-(ethylimino)-2,7-dimethyl-3Hxanthen- 9-yl]-ethyl ester, monohydrochloride (Rhodamine 6G). The laser output was centered at approximately 610nm and the lasing threshold was 30μJcm−2. The rapid throughput of LP-OVPD and its use of low vacuum in a horizontal reactor demonstrate its potential to facilitate low cost, roll-to-roll deposition of organic films for many photonic device applications.
Moisture Effect on Polythiophene Electroluminescence
Authors: Weng Tsu-Chien , Jin Bih-Yaw , Ding Ding-Kuo , Sakakibara Mitsuhiko
Published: April 2011

The moisture effect on the neutral and charged thiophene oligomers was investigated using ab initio methods. The influence of water molecules on the geometric relaxation of the neutral and charged tert-thiophenes is found to be important. The torsional distortion in neutral water/tert-thiophene complexes is larger than that of undoped or charged complexes. The relative orientation of the water molecule to thiophene changes dramatically upon the hole injection. The existence of water molecules in the polythiophene suppresses the hole mobility and, therefore, diminishes the efficiency of electroluminescence.
Electron Transfer at the n-InP | Poly(Pyrrole) Interface
Authors: Lonergan Mark C. , Cooney Christopher T. , Myers James A.
Published: April 2011

Measurements of the barrier height by capacitance-voltage techniques and of the equilibrium exchange current density by current-voltage techniques are performed on the rectifying interface between n-InP and poly(pyrrole) (chemically polymerized and characterized by an electrochemical potential of ≈0.2V vs. SCE). The current-voltage data yielded a quality factor of 1.2±0.1 and an equilibrium exchange current density of (1.2±0.6) x 10−9. A cm−2. The capacitance-voltage data yielded a barrier height of 0.73 ± 0.02 V and measured dopant densities within 15% of the expected value. These data, taken together, are inconsistent with thermionic emission theories developed to describe inorganic semiconductor I metal interfaces and often applied to inorganic semiconductor I doped conjugated polymer interfaces. In particular, the ratio of the rate constant for majority carrier electron capture (surface recombination velocity) at the n-InP | poly(pyrrole) interface to that at n-InP | metal interfaces is found to be (6 ± 5) × 10−3.
Nanocomposites of metallophthalocyanines and conjugated Polymers
Authors: Yi Shujian , Jenekhe Samson A.
Published: April 2011

Nanocomposites of phenoxy-substituted vanadyl phthalocyanine with a t-conjugated polymer, poly(benzimidazobenzophenanthroline ladder), have been prepared from their Lewis acid complexes in organic solvents. The resulting composite thin films obtained by spin-coating have excellent optical transparency and interesting composition-dependent morphology and photoelectronic properties. Enhanced photoconductivity, compared to the components, was observed in some composites with discrete nanoscale metallophthalocyanine aggregates.
Femtosecond Optical Nonlinearity in the Squarylium Dye J-Aggregates
Authors: Furuki M. , Pu L. S. , Sasaki F. , Kobayashi S. , Tani T.
Published: April 2011

Squarylium dye with two propyl and two hexyl groups forms a mono-molecular layer with domains of J-aggregates by spreading its chloroform solution at an air-water interface. Fluorescence microscopy and an absorbance evaluation which also considers the reflectance suggest that this Langmuir-film has a close packed two-dimensional structure with a complete Jaggregate formation of all dye molecules. Strong and ultrafast nonlinear optical responses, indicating delocalization of excitons over 30 molecules, have been observed at 5 °C from this ideal mono-molecular layer of J-aggregates.
Doping of Polyaniline by Corona Discharge
Authors: Job Aldo E. , Giacomett JosÉ A. , Mattoso Luiz H. C.
Published: April 2011

It is well known that conductive polyaniline (PANI) films are usually doped by immersing dedoped PANI films in HCI solution. This paper shows that a corona discharge can be successfully employed to dope thin films of polyaniline coated on poly (ethylene terephthalate) films. Similarly to the conventional doping with aqueous HCl the process is accompanied by a color change from blue to green and the conductivity can be tuned in the range from 10−10 up to 0.3 Scm−1. Such new doping method presents several advantages over the conventional one namely, dry process, use of no chemicals, rapidity and no dopant migration. Measurements also showed that the conductivity persists for a long time as observed for films prepared in chemical solution doping. It is believed that this novel technique could be employed in a continuous doping process aiming to produce films with large area for anti electrostatic packing applications.
Dielectric Properties of Sputtered BST on Ir Electrodes
Authors: White B. E. , Chu Peir Y. , Zafar Sufi , Balu V. , Gentile D. , Jones Robert E. , Jiang Bo , Melnick Bradley , Taylor Deborah , Zürcher Peter , Gillespie Sherry
Published: April 2011

The dielectric constant and dispersion of sputtered barium strontium titanate (BST) thin films deposited on Ir electrodes have been measured as a function of frequency and dielectric film thickness. Based on the measured variation in capacitance density with BST film thickness, an interfacial capacitance and thin film capacitance have been extracted. The variation of the interfacial capacitance density and the thin film capacitance density with frequency indicates that the majority of dispersion measured for BST deposited on Ir electrodes is due to the interfacial capacitance, in contrast to results found for Pt electrodes [1]. The temperature dependence of the interfacial capacitance and thin film capacitance has also been measured for these electrodes.
Surface Microstructures of Ferroelectric SrBi2Ta2O9, BaTiO3 and Metallic SrRuO3 Epitaxial Thin Films
Authors: Jiang Q. D. , Huang Z. J. , Chen C. L. , Brazdeikis A. , Jin P. , Feng H. H. , Benneker A. , Chu C. W.
Published: April 2011

We have made a comparative invetigation of the surface microstructures of epitaxially grown ferroelectric SrBi2Ta2O9, BaTiO3 films, and metallic SrRuO3 films, using scanning probe microscopy. Though their lattices (or pseudotetrogonal lattices) match closely with SrTiO3 (001) substrates, SPM results show very different surface microstructures. The surfaces of SrRuO3 films display atomically flat terraces of 90° oriented step edges. The size of steps is about 6 Å. The surface of BaTiO3 films deposited at various temperatures displays uniform rectangular islands. Different stages of SrBi2Ta2O9 epitaxial growth have been studied on thickness gradient films, which show clearly 2D nucleation and layer-by-layer growth, following a transition from 2D to 3D island growth. It finally develops into a surface exhibiting round hills consisting of curved terraces with size of steps ranging from 6 Å to 12.5 Å.
Seeded Epitaxial Growth of PbTiO3 Thin Films on (001) LaAlO3 using the Chemical Solution Deposition Method
Authors: Kim J. H. , Lange F. F.
Published: April 2011

Epitaxial PbTiO3(PTO) thin films were grown on (001) LaAlO3 (LAO) substrates by a two-step process from a mixed Pb-Ti double-alkoxide solution precursor. Scanning electron microscopy, x-ray diffraction, atomic force microscopy, and transmission electron microscopy were performed to characterize the microstructure of films and to evaluate the epitaxial phenomena. In the first step, very thin PTO films were deposited and then heat treated at 800 °C for lh. The films were broken up into isolated islands that have epitaxial relationship of [100](001)PTO∥[100](001)LAO. In the second step, another PTO thin films were deposited and then annealed at temperatures between 380 °C and 800 °C for 1h. In this seeded process, epitaxial PTO thin films, unobtainable when PTO thin films were deposited on the unseeded LAO substrates, could be grown. The islands formed in the first step act as seeds for the growth of epitaxial thin film in the second step.
Piezoelectric Properties of Sol-Gel Derived PZT Thin Films with Various Zr/Ti Ratios
Authors: Teqwee G. , McCarthy K. C. , McCarthy F. S. , Davis D. G. , Dawley J. T. , Zelinski B.J.J. , Uhlmann D. R.
Published: April 2011

Piezoelectric thin films are useful for application in microelectromechanical devices. A series of sol-gel derived PZT (lead zirconate titanate) thin films with various Zr/Ti ratios were prepared on platinized substrates. These films were fired to 650C - 700C to crystallize them into single-phase perovskite films, and their piezoelectric properties were measured using optical lever-based instrumentation. Large d33 piezoelectric coefficients up to 400 pm/V were obtained at the morphotropic phase boundary (PZT 53/47), making such films attractive in applications such as thin film transducers, microcanti levers and surface acoustic wave devices.
Structure and Physical Properties of Bi4Ti3O12Thin Films Prepared by APMOCVD and RTA
Authors: Wang H. , Wang Z. , Shang S. X. , Wang M.
Published: April 2011

Ferroelectric Bi4Ti3O12 thin films were grown by atmospheric pressure metal-organic chemical vapor deposition. After rapid thermal annealing (RTA), the films have a (001) preferred orientation, The I-V and C-V characteristics were studied, the resistivity were in the rang of 1010∼1013 ω. cm, at room temperature. The memory window is about 3V. These results snow that The Bi4Ti3O12 films prepared at present work are suitable for making ferroelectric FEFETs memories. By using planar silicon processing, the FEFET devices have been fabricated, which shows clearly memory effect under a applied ±5V gate voltage.
Novel Antimony Precursors for Low-Temperature CVD of Antimonide Thin Films
Authors: Todd Michael A. , Bhandari Gautam , Baum T. H.
Published: April 2011

Volatile antimony precursors were synthesized for the low temperature chemical vapor deposition (CVD) of antimony thin films. The molecules synthesized include tris (trifluoromethyl)stibine, Sb(CF3)3, Lewis base adducts of Sb(CF3)3, and antimony trihydride (stibine), SbH3. Isotopie substitution of stibine with deuterium leads to a more thermally stable, carbon-free antimony source. Similarly, deuterium substitution of trimethylsilylmethyl antimony dihydride leads to a stabilized liquid antimony precursor. The molecules were characterized using FTIR, NMR and DSC / TGA. Pure antimony films were deposited at temperatures below 300 °C with growth rates approaching 170 Å / min using a low pressure hot-wall CVD reactor. The films were characterized using XRD, EDS, SEM and AFM.
Investigation of Low Molecular Weight Carbosilanes as Potential Single-Source Precursors to Silicon Carbide
Authors: Lienhard M. A. , Interrante L. V. , Larkin D. J.
Published: April 2011

Several volatile, low molecular weight, linear and cyclic carbosilanes containing a 1:1 Si:C ratio were studied as single-source CVD precursors to SiC. A comparison of methylsilane, 1,3-disilacyclobutane, 1,3-disila-n-butane, and 1,3,5-trisilacyclohexane in terms of both their pyrolysis chemistry (decomposition onset temperatures and gaseous by-products) and resulting film characterization (growth rate, stoichiometry, crystallinity and morphology) is presented. Polycrystalline β-SiC films were deposited by LPCVD on Si (100) substrates at temperatures ranging from 800°C to 1100°C by using each of these single-source precursors.
Spray Chemical Vapor Deposition of CuInS2 Thin Films for Application in Solar Cell Devices
Authors: Hollingsworth Jennifer A. , Buhro William E. , Hepp Aloysius F. , Jenkins Philip P. , Stan Mark A.
Published: April 2011

Chalcopyrite CuInS2 is a direct band gap semiconductor (1.5 eV) that has potential applications in photovoltaic thin film and photoelectrochemical devices. We have successfully employed spray chemical vapor deposition using the previously known, single-source, metalorganic precursor, (Ph3P)2CuIn(SEt)4, to deposit CuInS2 thin films. Stoichiometric, polycrystalline films were deposited onto fused silica over a range of temperatures (300–400 °C). Morphology was observed to vary with temperature: spheroidal features were obtained at lower temperatures and angular features at 400 °C. At even higher temperatures (500 °C), a Cu-deficient phase, CuIn5S8, was obtained as a single phase. The CuInS2 films were determined to have a direct band gap of ca. 1.4 eV.
Morphology and Electron Emission Properties of Nanocrystalline CVD Diamond Thin Films
Authors: Krauss Alan R. , Gruen Dieter M. , Zhou Daniel , Mccauley Thomas G. , Qin Lu Chang , Corrigan Timothy , Auciello Orlando , Chang R. P. H.
Published: April 2011

Nanocrystalline diamond thin films have been produced by microwave plasma-enhanced chemical vapor deposition (MPECVD) using C60/Ar/H2 or CH4/Ar/H2 plasmas. Films grown with H2 concentration ≤ 20% are nanocrystalline, with atomically abrupt grain boundaries and without observable graphitic or amorphous carbon phases. The growth and morphology of these films are controlled via a high nucleation rate resulting from low hydrogen concentration in the plasma. Initial growth is in the form of diamond, which is the thermodynamic equilibrium phase for grains < 5 nm in diameter. Once formed, the diamond phase persists for grains up to at least 15–20 nm in diameter. The renucleation rate in the near-absence of atomic hydrogen is very high (∼1010 cm2sec−1), limiting the average grain size to a nearly constant value as the film thickness increases, although the average grain size increases as hydrogen is added to the plasma. For hydrogen concentrations less than ∼20%, the growth species is believed to be the carbon dimer, C2, rather than the CH3* growth species associated with diamond film growth at higher hydrogen concentrations. For very thin films grown from the C60 precursor, the threshold field (2 to ∼60 volts/micron) for cold cathode electron emission depends on the electrical conductivity and on the surface topography, which in turn depends on the hydrogen concentration in the plasma. A model of electron emission, based on quantum well effects at the grain boundaries is presented. This model predicts promotion of the electrons at the grain boundary to the conduction band of diamond for a grain boundary width ∼3–4 Å, a value within the range observed by TEM.
MOCVD of Field Emission Phosphors using a Liquid Delivery System
Authors: Moss T. S. , Espinoza B. F. , Salazar K. V. , Dye R. C.
Published: April 2011

Thin film phosphors for field emission displays show the potential to overcome the life-limiting problems that traditional powders face because of their high surface areas. By depositing a fully dense thin film, the surface area can be dramatically reduced, while the electrical and thermal conductivity is increased. Metal organic chemical vapor deposition offers the ability to deposit high quality, dense films that are crystalline-as-deposited and at temperatures low enough to allow for inexpensive glass. Deposition has been produced from mixtures of Y(tmhd)3, TEOS, Tb(tmhd)3, and O2 using a liquid delivery system. Coatings were shown to be composed of Y, Si, and Tb by x-ray fluorescence, but x-ray diffraction did not show any crystallinity. Excitation using radioluminescence produced a peak in the visible green at approximately 540 nm, indicative of the excitation of Tb3+. The morphology of the deposition was smooth, with surface features on the order of one micron and below. Some limited microcracking was also observed in the morphology because of the thermal expansion mismatch.
Materials Chemistry and Bulk Crystal Growth of Group III Nitrides in Supercritical Ammonia
Authors: Kolis Joseph W. , Wilcenski Steven , Laudise Robert A.
Published: April 2011

Reasonably sized crystals of aluminum and gallium nitrides can be grown in supercritical ammonia using chloride and amide as the mineralizer. Best growth was achieved at 380°C in ammonia at 40,000 psi (270 MPa). Under these conditions crystals as large as 0.4 mm could be grown over several days. Attempts to optimize the identity and concentration of the mineralizer, and the acidity of the solution, led to several new products including A1F3(NH3)2.
Surface Characterization of Calcium-Stabilized Zirconia Film by X-Ray Photoelectron Spectroscopy
Authors: Bensadon E. O. , Nascente P. A. P. , Bulhões L.O.S. , Pereira E. C.
Published: April 2011

A new methodology was developed to stabilized zirconia films at room temperature. The zirconium oxide films were prepared electrochemically by anodic oxidation of metallic zirconium at constant curcent density. X-ray diffraction (XRD) revealed the partial stabilization of the cubic phase in the ZrO2 films obtained in the presence of calcium. On the other hand, the films obtained in H3PO4 presented monoclinic phase. Scanning electron microscopy (SEM) showed that the oxide films obtained in calcium medium were porous, while the films obtained in H3PO4 were compact. X-ray photoelectron spectroscopy (XPS) identified ZrO2 and the intercalation of Na, N, P and CaO, as well as adventitious carbon. Using depth profiling, we observed that the concentrations of ZrO2, P and CaO increased with sputtering time.