bluuebunny/crossref_metadata_2025 huggingface dataset:
LECs Made of m-Lppp
Authors: Wenzl F. P. , Tasch S. , Gao J. , Holzer L. , Scherf U. , Heeger A.J. , Leising G.
Published: April 2011

We report the application of the blue light emitting conjugated polymer m-LPPP (methyl substituted laddertype poly(paraphenylene) ) in light emitting electrochemical cells. The active layer of the LEC consists of a blend of m-LPPP with the ionically conductive polymer PEO and LiCF3SO3 as ionic salt. Investigations of different concentrations of PEO and salt showed that the best LECs made of m-LPPP up to now where realised with an active layer consisting of a blend of m-LPPP:PEO:salt in the range of 20:10:3. In this case we are able to realise LECs with response times in the range of 30 μs. The I/U characteristics show low turn on voltages both for current and electroluminescence, but only in the case of ITO biased as a cathode. The initial electroluminescence spectra are quite the same as those for LEDs made of m-LPPP but turn into green after some time of operation.
Second-Order Nonlinear Optical Polymer by Directed Lithiation of Polyethersulfone
Authors: McCarron Harold E. , Walsh Christopher J. , Sen Rajashree , Mandal Braja K.
Published: April 2011

Directed lithiation of a polyethersulfone and the reactions of the lithiated species have been investigated. This method provides a new route to second-order nonlinear optical polymers.
Magnetic Properties of a Binary Mixture of Paramagnetic Metallomesogens
Authors: Shimizu Y. , Tantrawong S. , Yoshida M. , Sugino T.
Published: April 2011

Magnetic properties of a binary mixture of mesogenic tetraphenylporphyrin Cu(II) and VO(IV) complexes are reported. These mesogens show two lamellar mesophases (DL and DLC) and a binary phase diagram revealed that each mesophase is miscible. The magnetic properties were investigated by magnetization measurements using SQUID. It was found that the magnetization of 1:1 mixture (mole% base) was larger than those of the pure compounds belowca. 190 K, whilst 1:3 and 3:1 mixtures showed the decrease of magnetization in the full range of temperature in which the measurements were carried out. It was shown that χ−1vs. T plots did not obey Curie-Weiss law. For the VO(IV) complex and 1:1 mixture, stepwise changes could be recognized at the temperatures corresponding to the phase transitions. 1:1 mixture as well as Cu(II) and VO(IV) complexes totally involve antiferromagnetic interaction. However, ferromagnetic behavior in χ−1vs. T plots was seen about DL- DLCphase transition.
New Luminescent PPV Derivatives for Led Applications
Authors: Chuah B.S. , Cacialli F. , Davies J. E. , Feeder N. , Friend R. H. , Holmes A. B. , Marseglia E. A. , Moratti S. C. , Brédas J.-L. , Santos D.A. dos
Published: April 2011

A new poly(phenylenevinylene) [PPV] derivative 8 with dialkoxy substituents at the 2,3- positions of the phenylene ring of the polymer backbone has been prepared. This exhibited significantly different properties compared with the typical 2,5-dialkoxy substituted PPV derivatives. The polymer is not only significantly blue-shifted in its optical and luminescence properties but also has high photoluminescence (PL) and electroluminescence (EL) efficiencies. Investigation of the model oligomer 11 offers insight into this interesting behavior.
Thin Film of Conjugated Schiff-Base as Ultrahigh Density Data Storage Material
Authors: Yang W. J. , Yang Q. C. , Lu H. G. , Chen H. Y. , Hou S. M. , Ma L. P. , Zhang H. X. , Xue Z. Q. , Pang S. J.
Published: April 2011

N-(3-nitrobenzylidene)-p-phenylenediamine (NBPDA) was used as ultrahigh density data storage medium by scanning tunneling microscope (STM) technique. Data marks of 1.4nm in diameter were written by applying voltage pulses between the STM tip and the substrate. Structures of single crystal and thin films were characterized by IR, UV–Vis, XRD, STM and verified by DFT quantum chemical calculation.
Polydomain Structure of Epitaxial PbTiO3 films on MgO
Authors: Alpay S. P. , Prakash A. S. , Aggarwal S. , Ramesh R. , Roytburd A. L. , Shuk P. , Greenblatt M.
Published: April 2011

A PbTiO3(001) film grown on MgO(001) by pulsed laser deposition is examined as an example to demonstrate the applications of the domain stability map for epitaxial perovskite films which shows regions of stable domains and fractions of domains in a polydomain structure. X-ray diffraction studies indicate that the film has a …c/a/c/a… domain structure in a temperature range of °C to 400°C with the fraction of c-domains decreasing with increasing temperature. These experimental results are in excellent agreement with theoretical predictions based on the stability map.
An Optimized Process and Characterization of Pb(Zr,Ti)O3 Ferroelectric Capacitor for 1T/1C Ferroelectric RAM
Authors: Shin Dong-Won , Shin Soo-Ho , Lee Jin-Woo , Park Hong-Bae , Chun Yoon-Soo , Lee Mi-Hyang , Jung Dong-Jin , Hwang Yoo-Sang , Koo Bon-Jae , Lee Sung-Young , Kim Kinam
Published: April 2011

An optimized process of Pb(Zr,Ti)O3(PZT) ferroelectric capacitor has been investigated in order to develop a highly scaleable 1T/1C ferroelectric random access memory. The PZT ferroelectric capacitor, Pt/PZT/Pt stack, was formed on the TiO2/SiO2/Si substrate. The PZT thin films were prepared by conventional sol-gel multi-coating method. Physical and electrical properties of the PZT ferroelectric capacitors were characterized by XRD, SEM, TEM and RT6000S, respectively.

It was revealed that the microstructure of PZT thin film is strongly influenced by sol-gel coating process, especially depending on coating methods of the first PZT layer. The second phase was observed in the PZT thin films, which is found to be pyrochlore phase. The size and density of pyrochlore phase were significantly reduced by modifying the coating methods of first PZT layer. Microstructure of PZT thin film capacitors was evaluated in detail along with electrical properties such as remnant polarization, coercive electric field, and dielectric leakage. The sensing Pr window was also introduced for proper sensing margin in IT/1C ferroelectric random access memory. This concept is well verified by 64Kb 1T/1C ferroelectric random access memory.
The Influence of Film Thickness on the Magnitude and Aging Behavior of the Transverse Piezoelectric Coefficient (d31) of PZT Thin Films
Authors: Shepard J. F. , Chu F. , Moses P. J. , Trolier-McKinstry S.
Published: April 2011

The wafer flexure technique has been developed for the rapid measurement (less than 10 minutes) of the d31 coefficient of piezoelectric thin films. The technique is based upon the controlled bending of a clamped silicon substrate coated with a thin piezoelectric film. Flexure of the wafer results in the transfer of biaxial stress from the silicon to the film, and thus the production of an electric charge. The charge produced is used in conjunction with the applied principle stresses to determine the film's transverse piezoelectric coefficient (d31). For this study, the wafer flexure technique was modified from semi-ac operation to a mechanized ac measurement (i.e. electronic pressure oscillation and lock-in charge detection). Modifications made reduce electromagnetic noise and enhance both the resolution and precision of the device. The system was used to characterize the piezoelectric properties of lead zirconate titanate 52/48 thin films between 0.6 and 2.5 μm thick synthesized using a modified sol-gel technique. The transverse piezoelectric constants (d31) of the PZT films were found to range from −60 to −90 pC/N for the 0.6 and 2.5 μm films, respectively. Aging experiments of the d31; coefficients were also conducted and results showed values to be on the order of 4 to 8% per decade.
Electrical Properties of MFS-FETs using SrBi2 Ta2O9 Films Directly Grown on Si Substrates by Sol-Gel Method
Authors: Tokumitsu E , Fujii G. , Ishiwara H.
Published: April 2011

SrBi2Ta2O9(SBT) films have been prepared by the sol-gel technique on n-Si(100) substrates and nonvolatile memory operation of a metal-ferroelectric-semiconductor field effect transistor (MFSFET) using the SBT/Si structure has been demonstrated. Ploy-crystalline SBT films can be obtained on Si substrates and it is shown by the secondary ion mass spectrometry (SIMS) that the inter-diffusion between SBT and Si is suppressed even though high annealing temperature is required for the SBT film growth. Then the SBT/Si MFSFETs have been fabricated. Drain current - gate voltage characteristics clearly show hysteresis loops due to the ferroelectric nature of the SBT film. It is demonstrated that the drain current can be controlled by the “write” pulse, which was applied before the measurements, even at the same “read” gate voltage. Memory retention characteristics of SBT/Si MFSFETs are also presented.
Kinetics of Reactions Relevant to the Chemical Vapor Deposition of Indium Compounds
Authors: Allendorf M. D. , McDaniel A. H.
Published: April 2011

The kinetics of trimethylindium pyrolysis are investigated in a flow reactor equipped with a molecular-beam mass-spectrometric sampling system. Data are analyzed using a new computational approach that accounts for heat and mass transport in the reactor. The measured activation energy, 46.2 kcal mol−1, is in good agreement with previously reported values.
Effects of Reaction Conditions on Deposition of Ferrites from Alkaline Metal Hydroxide Gels
Authors: Schoch Karl F. , Vasilow Theodore R.
Published: April 2011

Formation of ferrites from aqueous solution of metal salts is a well known process involving precipitation of metal hydroxides followed by oxidation of the resulting gel. The purpose of the present work was to determine the effects oxygen flow rate on the progress of the reaction and on the structure and properties of the resulting precipitate. The reaction was carried out at 70°C with pH of 10.5 and oxygen flow rate of 2,4, or 8 standard liters per hour. The progress of the reaction was monitored by following the oxidation-reduction potential of the solution, which changes dramatically after the Fe(II) is consumed. The reaction rate increased with increasing oxygen flow rate. The Mg content of the precipitate was lower than that of the reaction mixture, possibly because of the pH of the reaction mixture. X-ray diffraction and infrared spectroscopy confirmed formation of a ferrite under these conditions.
Synthesis and Electro-Optical Properties of Potassium Titanyl Phosphate thin Films by Sol-Gel Method
Authors: Zhang Jianping , Lee Burtrand I. , Wang Feiling , Leitheiser Melvin A.
Published: April 2011

Potassium titanyl phosphate, KTiOPO4 (KTP), thin films were prepared by sol-gel process. The structural evolution of KTP thin films was investigated by means of DTA/TGA, XRD, and FT-IR. The electro-optical results show that KTP thin films have a refractive index of 1.8 and large quadratic electro-optical coefficient of R=2.50643*10−16 and have potential applications for electro-optical devices.
Removal of Titanium Oxide Grown on Titanium Nitride and Reduction of VIA Contact Resistance using a Modern Plasma Asher
Authors: Boumerzoug Mohamed , Xu Han , Bersin Richard , Mascher Peter , Balcaitis Ginutis
Published: April 2011

In making multi-level interconnects, a via layer is generally made of a dielectric layer grown on a TiN/AlSiCu/TiN metal stack. The via contact hole to the lower level metal is first etched after metal patterning and intermetal oxide deposition, then the resist mask for via etch is stripped in an oxygen plasma at high temperature before filling the via with tungsten or aluminum. However, during the resist stripping process, the titanium nitride (TiN) is exposed to oxygen radicals and becomes oxidized. This oxidized surface leads to high via resistance and may cause yield loss and poor adhesion of the subsequently deposited metal. Thus, the oxide layer must be removed completely before filling the via hole.

Utilizing a modern asher and combining microwave downstream plasma and low damage RIE we have successfully developed an integral process to strip the resist and to remove any oxidized TiN film. This process also gives clean vias that are free of polymer residues from the etching process.

Samples were characterized using Auger electron spectroscopy (AES), scanning electron microscopy (SEM), ellipsometry and via resistance measurements. The AES depth profile measurements and ellipsometry show clearly that a titanium oxide has grown onto TiN during the oxygen downstream ashing and is completely removed when adding the RIE step. The electrical measurements show that the resistance of vias cleaned with this two step process in a single tool is comparable to that of vias cleaned with Ar sputtering using a separate tool after the oxygen ashing process.
Epitaxial ZnO Piezoelectric Films for RF Filters
Authors: Emanetoglu Nuri W. , Lu Yicheng , Gorla Chandrasekhar , Liu Ying , Liang Shaohua , Mayo William
Published: April 2011

ZnO has high piezoelectric coupling coefficient and acoustic velocity; therefore, it is an attractive material candidate for high frequency and low loss filters. Piezoelectric ZnO thin film based RF devices offer the advantages such as low power consumption, circuit miniaturization and cost reduction through integration with main stream MMIC technology. We report CVD growth of epitaxial ZnO thin films on R-sapphire substrates. X-ray diffraction techniques have been used to study the crystallinity and orientation of the films, as well as the epitaxial relationship between the films and the substrate. High-resolution cross-sectional TEM reveals the atomically sharp interface structure. As grown ZnO films exhibit dominant n-type conductivity due to the oxygen vacancies. Excellent piezoelectricity has been achieved through a multi-step Li diffusion under oxygen ambient. Surface Acoustic Wave (SAW) filters with 10-micron wavelength have been fabricated. Low insertion loss and high piezoelectric coupling coefficient have been observed.
Microstructural and Photoluminescence Studies on Europium Doped Yttrium Oxide Films Synthesized by Metallorganic Vapor Deposition
Authors: Hirata G. A. , McKittrick J. , Yi J. , Pattillo S. G. , Salazar K. V. , Trkula M.
Published: April 2011

The microstructural and luminescence properties of europium doped yttrium oxide (Y2O3:Eu) thin films deposited by metallorganic chemical vapor deposition are presented in this work. It was found that surface morphology, crystallinity and photoluminescent emission properties are strongly dependent on substrate temperature during deposition. The depositions were carried out in a stainless steel chamber using yttrium and europium 2,2,6,6,-tetramethyl–3,5-heptanedionates as volatile precursors and O2 as the reactant gas. Post-annealing increased the crystallite size and decreased the lattice parameter, resulting in an increased photoluminescent emission intensity.
Mechanically Alloyed Nickel-Zirconium as a Heterogeneous Catalyst and a Catalyst Precursor
Authors: Brower W. E. , Montes A. J. , Pradlow K. A. , Bakker H. , Moleman A. C. , Yang H.
Published: April 2011

NiZr powders produced by mechanical alloying become active NO decomposition catalysts after an activation period in reaction conditions. Although the initially glassy structure exhibits a high activity, the NiZr powder becomes temporarily inactive. After about 10 hours in reaction conditions at 673 K, the powder again becomes active with a lower, but still substantial turnover frequency for NO decomposition. Oxygen produced by the reaction appears to be consumed by the catalyst during this second period of activity.
Field Emission From Tetrahedrally Bonded Amorphous Carbon as a Function of Surface Treatment and Contact Material
Authors: Milne W. I. , Robertson J. , Satyanarayana B. S. , Hart A. , Kleinsorge B.
Published: April 2011

In order to test whether field emission from tetrahedrally bonded amorphous (ta-C) is affected by the back contact material we have carried out a series of emission experiments on Filtered Cathodic Vacuum Arc (FCVA) produced ta-C films. The measurements were made on identical films of approximately 25 nm thickness which have been grown simultaneously on various substrates of different work function. For these experiments the substrates used were p-type c-Si, n-type c-Si, SnO2, tungsten, gold, lead, aluminium, molybdenum, chromium and titanium. Threshold fields for emission were generally in the range of 5–15 V/micron and showed no direct dependence on back contact material work function. Films grown on Ti and W however had much higher threshold fields in the range 30–35 V/micron and this is thought to be associated with the native oxide which was present between the back contact and the ta-C film. As grown ta-C is also known to have a 1–2 nm thick sp2 rich layer on its surface and this layer may also have some effect on field emission. The layer was etched in either an O2 or H2 plasma and both etched surfaces led to improved emission efficiency.
Field Emission from Nitrogen-Doped Diamond Film
Authors: Park M. , Bergman L. , Choi W. B. , Sowers A. T. , Nemanich R. J. , Hren J. J. , Cuomo J. J.
Published: April 2011

Nitrogen-doped diamond films were prepared for the first time using melamine (C3H6N6) as the nitrogen source. To explore the differences in the films produced with different precursors, nitrogen-doped films were also produced using pure nitrogen gas as the source. Since melamine has a ring structure with pre-existing C-N bonds, the incorporation of nitrogen on substitutional sites of diamond lattice are expected. Relatively large amounts of substitutional nitrogen were successfully doped into diamond without degrading its quality. However, when pure nitrogen gas was used as a doping source, the quality of the diamond was not as high as the sample doped with nitrogen by melamine. Raman spectroscopy, photoluminescence spectroscopy (PL), and field emission measurements were carried out to characterize the samples. Nitrogen-doped diamond samples did not exhibit any significant reduction in turn-on fields. It is suggested that nitrogen doping has only a minor effect on the field emission properties of the diamond films.
Raman Spectroscopy of Amorphous Carbon
Authors: Tallant D. R. , Friedmann T. A. , Missert N. A. , Siegal M. P. , Sullivan J. P.
Published: April 2011

Amorphous carbon is an elemental form of carbon with low hydrogen content, which may be deposited in thin films by the impact of high energy carbon atoms or ions. It is structurally distinct from the more well-known elemental forms of carbon, diamond and graphite. It is distinct in physical and chemical properties from the material known as diamond-like carbon, a form which is also amorphous but which has a higher hydrogen content, typically near 40 atomic percent. Amorphous carbon also has distinctive Raman spectra, whose patterns depend, through resonance enhancement effects, not only on deposition conditions but also on the wavelength selected for Raman excitation. This paper provides an overview of the Raman spectroscopy of amorphous carbon and describes how Raman spectral patterns correlate to film deposition conditions, physical properties and molecular level structure.
Structural Characterization of the Thermal Evolution of Tetrahedrally Coordinated Amorphous Carbon Films
Authors: Martinez-Miranda L. J. , Sullivan J. P. , Friedmann T. A. , Siegal M. P. , DiNardo N. J.
Published: April 2011

We present the results of a post-deposition annealing structural study on amorphous tetrahedrally-coordinated carbon (a-tC) films on Si(100) prepared by pulsed-laser deposition. Films as-deposited and post-annealed at 200, 300, 400, 500 and 600 °C, respectively, are studied using combined x-ray reflectivity and low-angle scattering measurements. The scans are fit to the Fresnel equations to obtain values for average film density, film and interface thickness, and film and interface roughness. We observe a correlation between the evolution of film density, roughness and the spacing of quasi-periodic structures in the films as a function of annealing temperature. We relate the evolution of these structural features with previous measurements of the resistivity and the observed stress release in these films.
Lattice Strains in Gold and Rhenium Under Non-Hydrostatic Compression
Authors: Duffy T. S. , Shen G. , Heinz D. L. , Ma Y. , Hemley R. J. , Mao H. K. , Singh A. K.
Published: April 2011

Lattice strains have been measured as a function of the angle, ψ, from the diamond cell stress axis in a sample of gold and rhenium at pressures of 15–37 GPa. Experiments were conducted using X-ray transparent gaskets made from beryllium. The differential stresses supported by gold and rhenium have been characterized to 37 GPa. It is also shown that proper choice of the diffraction geometry allows recovery of a quasi-hydrostatic compression curve under these highly non-hydrostatic conditions. X-ray elastic moduli have also been determined, and while good agreement with previous data is achieved for gold, there is a large discrepancy between the present results and extrapolated ultrasonic data for rhenium.
Powder processing of ductile materials for high pressure studies: application to intermetallic alloys
Authors: Otto J. W. , Frommeyer G. , Vassiliou J. K.
Published: April 2011

Ductile materials are difficult to powderize for use in high pressure work. The potential of different techniques (gas-atomization, mechanical alloying, ball milling and subsequent annealing) for preparing suitable powders of some aluminides is investigated. Compression of Ti46Al54and NiAl prepared by these methods yields equation of state parameters in good agreement with determinations by other methods.
Effects of Pressure on Plastic Deformation of Polycrystalline Solids: Some Geological Applications
Authors: Karato S.
Published: April 2011

Experimental studies on the effects of pressure on plastic properties are reviewed with an emphasis on those on geological materials. High pressures may affect plastic properties through two different ways: (i) through the effects of pressure on plastic deformation of a material with a given crystal structure and (ii) through the effects of pressure-induced phase transformations on plastic deformation. It is emphasized that the manner in which pressure affects plastic properties of solids depends on the microscopic mechanisms of plastic deformation and therefore it is essential to identify the mechanisms of deformation involved in a particular experimental condition. Three mechanisms are considered: (i) the Peierls mechanism, (ii) dislocation creep (power-law creep) and (iii) diffusion creep (or superplasticity). Creep strength of materials changes with pressure through the change in shear modulus and in the activation enthalpy for the Peierls mechanism. Structural phase transformations can dramatically change the creep strength determined by the Peierls mechanism. Changes can be either positive (increase in strength in a high pressure phase) or negative (decrease in strength in a high pressure phase). Creep strength controlled by dislocation creep usually increases exponentially with pressure through the increase in the activation enthalpy with pressure. Phase transformations can change the creep strength either positively or negatively for this mechanism depending on the manner in which dislocation mobility changes with crystal structure. Creep strength corresponding to diffusion creep changes with pressure in a similar fashion as dislocation creep.

High pressures in the deep interior of Earth and other terrestrial planets could lead to a significant increase in viscosity with depth, resulting in high temperatures due to the feedback between viscosity and temperature. Also phase transformations in constituent minerals that occur in certain depth ranges can cause dramatic changes in plastic properties. Both of them are likely to have important influence on the style of convection in the mantle of terrestrial planets and thus affect their geological history and tectonic activities.
Surface-particle interactions in the chemical mechanical polishing process
Authors: Adler J. J. , Rabinovich Y. I. , Singh R. K. , Moudgil B. M.
Published: April 2011

Chemical mechanical polishing (CMP) is a critical step in the fabrication of integrated circuits. Each layer of deposited material must be planarized before the next layer of circuitry can be formed. In CMP, a chemically active solution is used to modify the substrate so that a particulate abrasive may polish more efficiently. Modification of the surface often requires high oxidizer concentrations or pH extremes. Under these circumstances the stability of the polishing slurry and prevention of particulate attachment to the substrate is a difficult problem. In this study, atomic force microscopy (AFM) has been used to directly measure the forces between surfaces that simulate those in CMP. Initial investigation has focused on modeling the polishing of tungsten interconnect material by alumina slurries at acidic pH and evaluating the role surfactants can play in the stabilization of the polishing slurry and CMP processes.
Dispersion of Metal Oxide Nanoparticles in Conjugated Polymers: Investigation of the Tio2/PPV Nanocomposite
Authors: Baraton M.-I. , Merhari L. , Wang J. , Gonsalves K. E.
Published: April 2011

It is well established that the dispersion of nanosized metal particles in a polymer matrix can induce non linear optical properties, yet very little is known about the effect of semiconducting transition metal oxide nanoparticles on both electrical and luminescence properties of conjugated polymers. In this paper, we report the synthesis of a nanostructured TiO2/poly(pphenylenevinylene) system and show by diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) that a stable conjugated nanocomposite is obtained. Investigation of the photoluminescence (PL) properties reveals both a broadening and a blue shift of the emission spectra. Adsorption of oxygen is found to be stronger on the nanocomposite than on PPV and to reversibly quench the PL emission, thus suggesting enhanced gas sensing properties. A tentative mechanism explaining the role of n-TiO2 is briefly discussed.
Radiation Damage Effects in Ferroelectric Litao3 Single Crystals
Authors: Wetteland C. J. , Sickafus K. E. , Gopalan V. , Mitchell J. N. , Hartmann T. , Nastasi M. , Maggiore C. J. , Tesmer J. R. , Mitchell T. E.
Published: April 2011

Z-cut lithium tantalate (LiTaO3) ferroelectric single crystals were irradiated with 200 keV Art++ ions. LiTaO3 possesses a structure that is a derivative of the corundum (A12O3) crystal structure. A systematic study of the radiation damage accumulation rate as a function of ion dose was performed using ion-beam channeling experiments. An ion fluence of 2.5•1018 Ar2+ ions/m2 was sufficient to amorphize the irradiated volume of a LiTaO3 crystal at an irradiation temperature of ∼120K. This represents a rather exceptional susceptibility to ion-induced amorphization, which may be related to a highly disparate rate of knock-on of constituent lattice ions, due to the large mass difference between the Li and Ta cations. We also observed that the c− end of the ferroelectric polarization exhibits slightly higher ion dechanneling along with an apparent greater susceptibility to radiation damage, as compared to the c+ end of the polarization.
Giant Magnetoresistance in Iron and Cobalt Implanted Silver Thin Films
Authors: De Jesus C. M. , Marques J. G. , Soares J. C. , Redondo L. M. , Silva M. F. Da , Pereira De Azevedo M. M. , Sousa J. B.
Published: April 2011

The magnetoresistive behavior of granular thin films prepared by Fe and Co implantation in Ag thin films is reported. Ag thin films (∼2000Å) were implanted with Fe or Co at fluences up to 8×1016 at./cm2. The magnetoresistive response obtained after implantation was found to increase with the implanted fluence. A further increase by a factor of 3–4 can be achieved annealing the films in a conventional furnace at 620 K under vacuum. The best value of the magnetoresistance obtained so far is 9% at 10 K for a film implanted with Co at a fluence of 8×1016 at./cm2.
Defect Evolution in Ion Implanted Si: from Point to Extended Defects
Authors: Libertino Sebania , Benton Janet L. , Coffa Salvatore , Eaglesham Dave J.
Published: April 2011

Several recent experiments assessing the role of impurities (C, O), dopants (P, B) and clustering on defect evolution in ion implanted Si are reviewed. Deep level transient spectroscopy measurements were used to analyze the defect structure in a wide range of ion implantation fluences (1×108–5×1013 cm−2) and annealing temperatures (100–800 °C). By using substrates with a different impurity content and comparing ion implanted and electron irradiated Si samples, many interesting features of defect evolution in Si have been elucidated. It is found that only a small percentage, 4–16 % depending on ion mass, of the Frenkel pairs generated by the beam escape direct recombination and is stored into an equal number of room temperature stable vacancy- (V-) and interstitial-type (I-) defect complexes. Identical defect structures and annealing behavior have been measured in ion implanted (1.2 MeV Si, 1×108–1×1010/cm2) and electron irradiated (9.2 MeV to fluences between 1 and 3×1015/cm2) samples in spite of the fact that denser collision cascades are produced by the ions. The O and C content of the substrate plays a major role in determining the point defect migration, the room temperature stable defect structures and their annealing behavior. Annealing at temperatures up to 300 °C produces a concomitant reduction of the I- and V-type defect complexes concentration, demonstrating that defect annihilation occurs preferentially in the bulk. At temperatures above 300 °C, when all V-type complexes have been annealed out, ion implanted samples present a residual I-type damage, storing 2–3 I per implanted ion. This unbalance is not observed in electron irradiated samples and it is a direct consequence of the extra implanted ion. The simple point defect structures produced at low ion fluence (1×108–1×1011 /cm2) anneal at ∼ 550 °C. At higher fluences (∼ 1012–1013/cm2) and for annealing temperatures above 500 °C the deep level spectrum is dominated by two signatures at Ev+0.33 eV and at Ev+0.52 eV that we have associated to Si interstitial clusters. Impurities (C, O and B) play a role in determining nucleation kinetics of these defects, but they are not their main constituents. The dissolution temperature of these clusters indicates that they might store the interstitials that drive transient enhanced diffusion phenomena occurring in the absence of extended defects. Finally, at higher implantation fluence, a signature of extended defects is observed and associated to the presence of {311} defects detected by transmission electron microscopy analyses.
Silver Nanocluster Formation In Implanted Silica
Authors: Mariotto G. , Freire F. L
Published: April 2011

Samples of fused silica were implanted at room temperature with 300 keV-Ag+ for doses ranging from 0.8×1016 to 14×1016 ions/cm2. A multi-technique approach including Rutherford backscattering spectrometry (RBS), x-ray diffraction (XRD), optical absorption and Raman scattering spectroscopies has been used to characterize silver precipitate. The Ag-depth profiles of samples implanted with doses higher than 6×1016 Ag+/cm2 show a bi-modal distribution, with the appearance of a secondary maximum near the surface. XRD spectra indicated the formation of silver nanocrystals of ∼10 nm in size within the heavily implanted samples. Optical absorption has been used to monitor the effects of ion doses on the optical properties of the metal clusters in the UV-Vis region. A single broad absorption band, due to surface plasmon resonance, is peaked at about 400 nm for low implantation doses. For doses higher than 4.3×1016 Ag+/cm2, a second broad band originates at higher wavelengths, peaking at 625 nm for the highest dose. The evolution of optical spectra is tentatively discussed in terms of the formation of silver particle aggregates with no longer spherical shape. An estimate of the mean size of silver nanoclusters of about 5.5 nm is obtained from low-frequency Raman scattering due to acoustic vibrations localized at the cluster surface. The discrepancies in the metal particle size obtained from XRD and Raman scattering measurements are discussed with respect to optical absorption data.
Study of the Effects of MeV Ag, Cu, Au and Sn Implantation on the Optical Properties of LiNbO3
Authors: Williams E. K. , Ila D. , Sarkisov S. , Curley M. , Poker D. B. , Hensley D. K. , Borel C.
Published: April 2011

We present the results of characterization of linear absorption and nonlinear refractive index of Au, Ag, Cu and Sn ion implantation into LiNbO3. Silver was implanted at 1.5 MeV to fluences of 2 to 17 × 1016/cm2 at room temperature. Gold and copper were implanted to fluences of 5 to 20 × 1016/cm2 at an energy of 2.0 MeV. Tin was implanted to a fluence of 1.6 × 1017/cm2 at 160 kV. After heat treatment at 1000°C a strong optical absorption peak for the Au implanted samples appeared at ∼620 nm. The absorption peaks of the Ag implanted samples shifted from ∼450 nm before heat treatment to 550 nm after 500°C for lh. Heat treatment at 800°C returned the Ag implanted crystals to a clear state. Cu nanocluster absorption peaks disappears at 500°C. No Sn clusters were observed by optical absorption or XRD. The size of the Ag and Au clusters as a function of heat treatment were determined from the absorption peaks. The Ag clusters did not appreciably change in size with heat treatment. The Au clusters increased from 3 to 9 nm in diameter upon heat treatment at 1000°C. TEM analysis performed on a Au implanted crystal indicated the formation of Au nanocrystals with facets normal to the c-axis. Measurements of the nonlinear refractive indices made using the Z-scan method showed that Ag implantation changed the sign of the nonlinear index of LiNbO3 from negative to positive.
In-situ observation of atomic processes in Xe nanocrystals embedded in al
Authors: Mitsuishi K. , Song M. , Furuya K. , Birtcher R. C. , Allen C. W. , Donnelly S. E.
Published: April 2011

Self-organization processes in Xe nanocrystals embedded in Al are observed with in-situ high-resolution electron microscopy. Under electron irradiation, stacking fault type defects are produced in Xe nanocrystals. The defects recover in a layer by layer manner. Detailed analysis of the video reveals that the displacement of Xe atoms in the stacking fault was rather small for the Xe atoms at boundary between Xe and Al, suggesting the possibility of the stacking fault in Xe precipitate originating inside of precipitate, not at the Al/Xe interface.
Study of the effects of MeV Ions on PS and PES
Authors: Evelyn A. L. , Ila D. , Zimmerman R. L. , Bhat K. , Poker D. B. , Hensley D. K. , Just N.
Published: April 2011

The electronic and nuclear stopping effects produced by MeV ion bombardment in polyethylene (PE) and polyvinylidene chloride (PVDC) have been previously studied and reported. We have subsequently selected two other insulators: polystyrene (PS) and polyethersulfone (PES) which contains sulfur as a crosslinking agent, and irradiated them with MeV alpha particles. The electronic and nuclear effects of the incident ions were separated by stacking thin films of the polymers. A layered system was selected such that the first layers experienced most of the effects of the electronic energy deposited and the last layers received most of the effects of the nuclear stopping. The changes in the chemical structure were measured by residual gas analysis (RGA), Raman microprobe analysis, RBS and FTIR. The post-irradiation characterization resolved the effects of the stopping powers on the PS and PES and the results were compared with those from PE and PVDC.
Molecular Dynamics Simulation of Fullerene Cluster Ion Impact
Authors: Aoki Takaaki , Seki Toshio , Tanomura Masahiro , Matsuo Jiro , Insepov Zinetulla , Yamada Isao
Published: April 2011

In order to interpret the projection range and to reveal the mechanism of damage formation by cluster ion impact, molecular dynamics simulations of a fullerene carbon cluster (C60) impacting on diamond (001) surfaces were performed. When the kinetic energy of C60 is as low as 200eV/atom, C60 implants into the substrate deeper than a monomer ion with the same energy per atom because of the clearing-way effect. The kinetic energy of the cluster disperses isotropically because of the multiple-collision effect, and then a large hemispherical damage region is formed. When the energy of the cluster is as high as 2keV/atom, the cluster dissociates in the substrate, and then cascade damage is formed like in a case of a monomer ion impact. The projection range of incident atoms becomes similar to that of the monomer with the same energy per atom. However, the number of displacements of C60 is larger than the summation of 60 monomer carbons. The displacement yield of fullerene is 4 to 7 times higher than that of monomer carbon. This result agrees with the measurement of the displacements made on sapphire substrates with C60 and C2 irradiation.
High Quality Oxide Film Formation by 02 Cluster Ion Assisted Deposition Technique
Authors: Matsuo J. , Qin W. , Akizuki M. , Yodoshi T. , Yamada I.
Published: April 2011

A new oxide film formation technique using gas-cluster ion beams has been developed. 02 cluster ions were used to irradiate during the evaporation of metal atoms, and PbOx and In203 films were grown. At the acceleration voltages above 5 kV, polycrystalline PbOx films preferentially oriented to (111) were obtained. A significant smoothing effect was observed with an acceleration voltage as low as 1 kV. An average surface roughness of 0.9 nm was obtained at 7 kV. Oxygen cluster ion beams are also utilized to grow In203 films, which are widely used as conductive-transparent films in flat panel display. In203 was deposited on glass or silicon substrates with simultaneous irradiation with an oxygen cluster ion beam. Highly transparent (80%) and low resistivity (<4×10−4 Ωcm) films were obtained with 7keV oxygen cluster ion beams. Kinetic energy of above 3keV is necessary to obtain low resistivity films. These results clearly indicate that the kinetic energy of the cluster is effectively used to enhance oxidation on the surface without radiation damage, in spite of the high acceleration voltages.
Discovery of Long Range Order in Thin (2-20 NM) SiO2 Films by Ion Beam Analysis
Authors: Herbots N. , Atluri V. , Hurst Q. B. , Shaw J. M. , Banerjee S. , Bradley J. D. , Culbertson R. J. , Smith D. J.
Published: April 2011

SiO2 films, 2-20 nm thick, were grown on passivated, ordered Si(100) to correlate electrical properties and oxidation rates with processing for ultra-thin gate oxides. Ordered Si(l 00) (1 × 1) stable in ambient air was obtained at room temperature by wet chemical cleaning. The thickest oxides were grown by Rapid Thermal Oxidation at 850°C, the thinnest at room temperature. O was detected by Ion Beam Analysis (IBA) using a combination of ion channeling with the 3.05 MeV 16O(α,α)16O nuclear resonance. It then becomes possible to measure order in thin SiO2 by comparing the total amount of O from rotating random spectra to disordered O detected by ion channeling, and detect the alignment of O with the atoms in Si(100)
Formation Energy of Interstitial Si in Au-Doped Si
Authors: Suezawa Masashi
Published: April 2011

In this report, we proposed that complexes responsible for optical absorption lines in Si grown in a hydrogen (H) atmsophere were composed of interstitial Si and H atoms and then determined the formation energy of interstitial Si in Au-doped Si from the measurements of optical absorption due to H bound to interstitial Si. In the first experiment, specimens were grown in a hydrogen atmosphere. In the second experiment, Si crystals were doped with Au by a vapor method; namely, specimens were sealed in quartz capsules together with a piece of Au wire and then annealed at high temperature followed by quenching in water. Then the specimens were doped with H by annealing them in hydrogen atmosphere of 1 atm. followed by quenching. We measured optical absorption of those specimens. From the effect of impurity on the optical absorption spectra of Si grown in a hydrogen atmosphere, we concluded that those optical absorption lines, including 2223 cm−1line, were due to complexes of interstitial Si and H. From the temperature dependence of the intensity of 2223 cm−1line, the formation energy of interstitial Si in Au-doped Si was determined to be about 2.1 eV
Damage in High Energy Light Ions Irradiated Silicon Carbide
Authors: Leveque P. , Godey S. , Renault P.O. , Ntsoenzok E. , Barbot J.F.
Published: April 2011

Commercial n-type 4H-SiC wafers were implanted with doses of MeV alpha particles, high enough to cause majority carrier modification. Analysis of infrared reflectivity spectra shows that the implanted crystals can be divided into three layers: a surface layer of about 30 nm followed by a compensation layer where the energy transfer of the incident particles is low and an overdoping layer in the region of maximum defect production, i.e. near the theoretical mean range of ions Rp
Peculiarities of Zn Diffusion from Polymer Spin-on Films in AlGaAs
Authors: Kamanin A.V. , Mintairov A.M. , Shmidt N.M.
Published: April 2011

Zn diffusion into AlxGa1−xAs from polymer spin-on films has been investigated. An increase in Zn diffusivity has been observed with increase in the content of Al in A1GaAs compounds. The effect has been related to more coefficient of self-diffusion for Al than for Ga. The availability of the near-surface layer enriched with Al in epitaxial AlGaAs wafers has been found to result in poor reproducible diffusion characteristics.
Plasma Chemistry Study of Plasma Ion Implantation Doping for Cmos Devices
Authors: Qin Shu , Zhou Yuanzhong , Chan Chung
Published: April 2011

Plasma ion implantation (PII) doping processes utilizing PH3/He and B2H6/He plasmas to fabricate CMOS devices are presented. The impact of plasma chemistry of PH on device structure and characteristics are studied. By using an optimized process condition, low contamination levels and good device characteristics have been achieved.
Edge Effects of Nitride Film Patterning on Dislocation Generation in Local Oxidation of Silicon
Authors: Peidous I. V. , Sundaresan R. , Quek E. , Lau C. K.
Published: April 2011

Extensive monitoring of device characteristics in the manufacturing of ULSI with advanced LOCOS isolation revealed the strong dependence of device leakage currents on the process of patterning of silicon nitride films applied as a hard mask for local oxidation of silicon wafers. At the same time, the level of the leakage currents strongly correlated to stress-induced dislocation density in the device structures. Formation of microtrenches on the wafer surface at the nitride film edges was identified to have a major impact on the leakage currents. Surprisingly, structures having nitride film edge profiles with feet were consistently dislocation-free after the local oxidation. This showed that nitride etching process created surface damage that provided effective sites for crystal defect nucleation in silicon at the film edges. Computer simulations demonstrated that the feet at nitride edges substantially suppress stress growth during local oxidation.
The Incorporation and Complex Formation of Ag Acceptors in CdTe
Authors: Wolf H. , Filz T. , Hamann J. , Ostheimer V. , Lany S. , Wichert Th. , Deicher M. , Burchard A.
Published: April 2011

Using the radioactive isotope 111Ag, the incorporation of Ag into CdTe is investigated by photoluminescence spectroscopy (PL) and the perturbed yy-angular correlation technique (PAC). PL is used to demonstrate the incorporation as a substitutional acceptor (AgCd) by monitoring the intensity of the donor-acceptor transition, corresponding to an acceptor level of EV + 108 meV, which decreases just with the half life of the radioactive decay of the 111Ag isotope. Since the isotope 111Ag also serves as a probe atom for PAC experiments, it is possible to confirm the incorporation of Ag atoms on lattice sites with cubic symmetry. Additionally, in CdTe a defect complex is detected, which is assigned to a AgCd-VTe pair. A second defect complex is observed in CdTe doped with In, which is assigned to an InCd-AgCd pair. By PAC experiments with the probe 111In that are performed in Ag doped CdTe, the formation of the InCd-AgCd pair is confirmed besides the well known formation of the InCd-VCd pair. The migration energy of the cation vacancy is estimated on the basis of an isothermal annealing sequence.
Studies of the Microscopic Nature of Cu-Pairs in Silicon
Authors: Istratov A.A. , Heiser T. , Hieslmair H. , Flink C. , Weber E.R.
Published: April 2011

Studies of the thermal dissociation kinetics of Cu-pairs in p-type silicon revealed that the dissociation energy of the pairs is 1.02±0.07 eV, which is twice as large as the binding energy of a coulombically bound donor-acceptor pairs formed by singly charged ions placed on nearest neighbor <111> sites. The dependence of the hole emission rate from the center versus electric field in the depletion region was found to be much weaker than predicted by the Pool-Frenkel law. On the other hand, the polarization potential describing emission from a neutral impurity gave a satisfactory fit to the experimental data. It is concluded that the Cu-pair is a donor with either covalent or mixed type of bonding of interstitial and substitutional copper atoms.
Solutions to Gate Oxide Integrity on TFSOI Substrates Caused by PMOS Threshold-Voltage Implant
Authors: Hong S. Q. , Wetteroth T. , Wilson S. R. , Steele B. , Schroder D. K.
Published: April 2011

Due to the lack of effective gettering, gate oxide on thin-film-silicon-on-insulator (TFSOI) substrates is much more sensitive than its bulk Si counterpart to process damage during device fabrication, especially prior to gate oxide growth. Presented in this paper as a typical example is the severe oxide degradation caused by PMOS threshold-voltage implant. Several approaches to circumvent this problem are explored, such as Vt implant without sacrificial oxide (sacox), low temperature anneal before sacox removal, or implementation of lateral gettering. As a result of these efforts, a significant improvement in gate oxide integrity is achieved with increased oxide breakdown voltages and charge-to-breakdowns, as well as a reduction in oxide charge trapping. This work also demonstrates the feasibility of achieving bulk-comparable gate oxide on TFSOI substrates.
Effect of Oxygen on the Formation of Dryetching Damage Introduced into Si-Substrate
Authors: Hamada Koji , Kitano Tomohisa
Published: April 2011

This paper reports the effects of oxygen in a Si substrate on dryetching damage during gate-electrode formation and side-wall formation. Different types of deep level traps were created in Czochralsi (CZ) and in p/p+-epitaxial wafers during side-wall formation. In comparison to the CZ wafers, a deep energy state and large hole capture cross section for the electrically active trap appears in the p/p+-epitaxial wafers. The depth profile of the deep trap in CZ wafers is shallower than that in p/p+-epitaxial wafers. This result indicates that the trap diffusivity in a CZ wafer is smaller than that in a p/p+-epitaxial wafer. Therefore, it suggests that creation of the trap in CZ wafers is influenced by the oxygen within the silicon. From results, the origin of the trap was identified to be carbon-oxygen complexes in the CZ wafer and carbon complexes in the p/p+-epitaxial wafer. Thus, the oxygen in the Si substrate plays a role in the formation of carbon-oxygen complexes and in suppressing the trap introduced into the Si substrate during SiO2 etching.