bluuebunny/crossref_metadata_2025 huggingface dataset:
Tailoring the Work Function of Chalcopyrite Thin Films with Self-Assembled Monolayers of Thiols
Authors: Lehmann Sebastian , Fuertes Marrón David , Bär Marcus , Lauermann Iver , Mönig Harry , Lux-Steiner Martha Ch.
Published: April 2011

Self-assembled monolayers of fluorinated thiols have been used as a means of surface conditioning to modify the work function of polycrystalline, wide-gap, chalcopyrite thin films. The molecular dipole, characteristic of such polar molecules, could be transferred to the surface of the semiconductor. Self-arrangement and orientation of the molecules upon adsorption ensured a net dipole contribution that was observed by means of ultra-violet photoemission spectroscopy. Such an approach offers a simple way for interface engineering, with a potential impact on the design of compound-specific band alignments of chalcopyrite-based devices. Molecular mechanics calculations of the expected molecular geometries complemented this work.
Imaging Cellular and Viral Materials with Small Cantilevers Developed for High Speed Atomic Force Microscopy
Authors: Fantner Georg , Ivanov Tzvetan , Ivanova Katerina , Gray David , Rangelow Ivo W , Hansma Paul K , Belcher Angela M
Published: April 2011

High speed atomic force microscopy (AFM) holds the promise of investigating dynamic systems in real time with single molecule resolution. With the big push towards understanding more complex systems such as cell mechanics or cell-cell and cell-virus interactions, a tool is required that can extract information about these processes in real time in a physiological environment. Atomic force microscopy has been successfully used for investigations of many biological systems and materials in real life conditions, but taking AFM images takes too long to follow many biologically relevant processes. Therefore, attempts have been made to develop high speed AFM by reengineering all the components of an AFM system and much progress has been made. To be useful for investigations of biological systems however, it is often essential to keep imaging forces low in order to get good image quality and not to damage the sample. In this paper we will discuss new small AFM cantilevers we've developed to combine high resonance frequencies for faster imaging with low spring constants for gentle imaging.
Effect of Relative Humidity on Chemical Heterogeneity Imaging with Atomic Force Microscopy
Authors: Gu Xiaohong , Chen Lijiang , Xu Chang , Julthongpiput Duangrut , Fasolka Michael , Nguyen Tinh
Published: April 2011

In this study, a well-controlled humidity system is used to enhance the sensitivity of AFM for characterizing surface chemical heterogeneity of patterned self-assembled monolayers (SAMs) and hydrophilic-hydrophobic polymeric brush specimens. Dependence of the AFM friction contrasts on the surface energy differences between the hydrophilic regions and hydrophobic regions of the chemically heterogeneous samples has been investigated as a function of relative humidity (RH). Effects of RH and surface chemistry on tip-sample adhesion are also investigated. Both AFM image contrast and tip-sample adhesion forces between the hydrophilic and hydrophobic regions significantly depend on RH and follow the similar trend as a function of RH. The results clearly demonstrate that, by using proper RH at the tip-sample environment, chemically heterogeneous regions can be distinguished with the AFM.
The Effect of Composition on the Properties of Semiconducting Transition Metal Nitrides
Authors: Moreno-Armenta Maria G. , Armando Reyes-Serrato , Gerardo Soto H.
Published: April 2011

Using the full potential linearized augmented plane wave (FP-LAPW) method, we investigate the bulk structural and electronic properties in the scandium-, yttrium-, and copper-nitrides over a wide range of nitrogen concentrations. The N atom was gradually incorporated into metal matrix with and without metal vacancies. The ground state properties like densities of states (DOS) and formation energies are determined for each calculated alloy. We have found that the semi-conducting state in copper nitride have a tinny compositional margin. Any deviation of the ideal stoichiometry will produce a metallic character. What is more, the stabilities of the conductive phases are very close to the stability of the semi conducting phase, with a little margin favorable to the conducting phases. The calculations of scandium- and yttrium nitrides show, that for very low nitrogen incorporations, the hexagonal and fcc phases may coexist. However, for high nitrogen concentration the cubic phases are favored. For non-stoichiometric nitrogen content, the materials behave as metal, whereas at stoichiometric composition the DOS becomes zero at Fermi level (EF), confirming in this way the semiconductor character of these nitrides.
Structure of Isolated Oxygen Impurity States in InN
Authors: Alexandrov Dimiter , Butcher Scott , Dietz Nikolaus , Yu Hang
Published: April 2011

The electron state structure of isolated interstitial O atoms in real InN (containing clusters of InN, clusters of InON and clusters of non-stoichiometric InN:In) is the subject of investigation in this paper. It is shown that for the interstitial O atoms the corresponding symmetry is equivalent to that of an O atom in vacuum if the dielectric permittivity of InN is considered, and therefore the hydrogen like impurity atom analysis can be applied for isolated interstitial O atoms hosted in a real InN lattice. It is found that: i) If the O atom is interstitially incorporated in a cluster of pure InN the impurity state has an energy of -5.11 eV, which acts as a donor level with ionization energy +0.06 eV, and also this state is a donor level with an ionization energy of -0.02 eV for a cluster of InON if this cluster occurs at a distance of less than 30 Angstroms; ii) The impurity state has energy -5.15 eV if the O atom is interstitially incorporated in a cluster of InON, which acts as a donor level with ionization energy +0.02 eV, and also this state is a donor level with ionization energy +0.10 eV for a cluster of InN if this cluster occurs on a distance less than 60 Angstroms from the O atom. iii) If the O atom is interstitially incorporated in cluster of non-stoichiometric InN:In the impurity state has energy -5.38 eV, which is in the valence band of this cluster. However this state acts as donor level for both cluster of InN and cluster of InON if they are on distance less that 59 Angstroms from the O atom. The donor ionization energy for the first cluster is +0.33 eV, and for the second cluster it is +0.25 eV.
Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications
Authors: Rodak L. E. , Kuchibhatla Sridhar , Famouri P. , Liu Ting , Korakakis D.
Published: April 2011

Aluminum nitride (AlN) is a promising material for a number of applications due to its temperature and chemical stability. Furthermore, AlN maintains its piezoelectric properties at higher temperatures than more commonly used materials, such as Lead Zirconate Titanate (PZT) [1, 2], making AlN attractive for high temperature micro and nano-electromechanical (MEMs and NEMs) applications including, but not limited to, high temperature sensors and actuators, micro- channels for fuel cell applications, and micromechanical resonators.

This work presents a novel AlN micro-channel fabrication technique using Metal Organic Vapor Phase Epitaxy (MOVPE). AlN easily nucleates on dielectric surfaces due to the large sticking coefficient and short diffusion length of the aluminum species resulting in a high quality polycrystalline growth on typical mask materials, such as silicon dioxide and silicon nitride [3,4]. The fabrication process introduced involves partially masking a substrate with a silicon dioxide striped pattern and then growing AlN via MOVPE simultaneously on the dielectric mask and exposed substrate. A buffered oxide etch is then used to remove the underlying silicon dioxide and leave a free standing AlN micro-channel. The width of the channel has been varied from 5 ìm to 110 ìm and the height of the air gap from 130 nm to 800 nm indicating the stability of the structure. Furthermore, this versatile process has been performed on (111) silicon, c-plane sapphire, and gallium nitride epilayers on sapphire substrates. Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and Raman measurements have been taken on channels grown on each substrate and indicate that the substrate is influencing the growth of the AlN micro-channels on the SiO2 sacrificial layer.
Application of XRF and AMS Techniques to Textiles in the Mongol Empire
Authors: Katayama Tomoko , Ide-Ektessabi Ari , Funahashi Kazuki , Nishimura Ryoichi
Published: April 2011

X-ray fluorescence (XRF) and Accelerator Mass Spectrometry (AMS) techniques were applied to four pieces of ancient Mongolian textiles in order to assist cultural studies of the most significant era of medieval western Asian culture. Radiocarbon dating using Accelerator Mass Spectrometry (AMS) was performed in order to determine the historical age of these pieces. Then, X-ray fluorescence analysis using Synchrotron Radiation (SR-XRF) was carried out in order to obtain elemental maps as well as investigate their constituent elements. Results showed that the textiles were produced between13th and 14th century, and possessed elements such as Au, Cu, Fe and Ti were traced in these pieces whereas Au was used to make gold threads. Cu, Fe and Ti are well known as metallic mordant. In addition, high resolution images were obtained using Scanning Electron Microscope (SEM) to observe the textile structure and their weaving conditions. The whole collected data can assist in bringing into light and facilitate a deeper understanding of the medieval Mongolian cultures, the textile technology, staining techniques, material process technology of the Mongolian Empire and their relations with the neighboring east and central Asian cultures, such as Persia, India and China.
Analysis of Modern and Ancient Artifacts for the Presence of Corn Beer; Dynamic Headspace Testing of Pottery Sherds from Mexico and New Mexico
Authors: Borek Theodore , Mowry Curtis , Dean Glenna
Published: April 2011

A large volume-headspace apparatus that permits the heating of pottery fragments for direct analysis by gas chromatography/mass spectrometry is described here. A series of fermented-corn beverages were produced in modern clay pots and the pots were sampled to develop organic-species profiles for comparison with fragments of ancient pottery. Brewing pots from the Tarahumara of northern Mexico, a tribe that regularly uses corn kernels to ferment a weak beer, were also examined for volatile residues and organic-species profiles were generated. Finally, organic species were generated from ancient potsherds from an archaeological site and compared with the modern spectra. The datasets yielded similar organic species, many of which were identified by computer matching of the resulting mass spectra with the NIST mass spectral library. Additional analyses are now underway to highlight patterns of organic species common to all the spectra. This presentation demonstrates the utility of GC/MS for detecting fermentation residues in the fabric of unglazed archaeological ceramics after centuries of burial. This, in turn, opens unexpected new doors for understanding the human past by means of GC/MS analyses.
The Relation between the Fine Structural Change and Color Fading in the Natural Mineral Pigments Azurite and Malachite
Authors: Nishimura Ryoichi , Ide-Ektessabi Ari
Published: April 2011

Many ancient Asian and Japanese paintings have been drawn with natural mineral pigments. The discoloring mechanism of these pigments has been a real concern for the characterization, restoration and preservation of the ancient cultural properties. The authors expect that the color fading is deeply related with the chemical composition and the fine structural change of the major elements. Therefore the purpose of this paper is to make clear the relation between the fine structural change and color fading.

We analyzed several representative pigments of Japan, including copper carbonate hydroxide pigments (blue verditer and green verditer, “gunjo” and “ryokusho” called in Japanese) by x-ray fluorescence analysis (XRF) and x-ray absorption fine structure (XAFS). In order to examine the deterioration of pigments, some of them were exposed in the highly-heated condition. In addition, the spectral reflectivity data are also collected on spectrophotometer system.

Here we propose to compare the results obtained from XRF and XAFS with the spectral reflectivity data. The results demonstrate that the chemical composition and the fine structural change can provide valuable information for revealing the discoloring mechanism, which would then lead to the original color estimation of the ancient cultural properties.
Collaboration or Appropriation? Examining a 17th c. Panel by David Teniers the Younger and Jan Brueghel the Younger Using Confocal X-Ray Fluorescence Microscopy
Authors: Mass Jennifer L. , Woll Arthur R. , Ocon Noelle , Bisulca Christina , Wazny Tomasz , Griggs Carol B. , Cushman Matt
Published: April 2011

The 17th c. Flemish painting on panel, The Armorer's Shop, has long been attributed to David Teniers the Younger (1610-1690). The painting depicts an opulent pile of parade armor at the bottom left foreground, a seated armorer at the bottom right foreground, and a forge surrounded by workers in the middle ground. The Teniers attribution is derived from his signature at the bottom right as well as figural groups and other visual elements that are commonly associated with him and executed in his style. During dendrochronological examination of the painting, a portion of the oak plank comprising the overall structure was found to have been carved out so that a smaller plank (containing the parade armor) could be inserted into the resulting depression. This unusual construction, combined with the identification of several paintings by Jan Brueghel the Younger (1601-1678) depicting the same parade armor, raised questions about the attribution and chronology of construction of the painting. Art historical research suggests that the smaller plank with the armor was painted by Brueghel and that the remainder of the panel with the workers and forge was painted by his brother-in-law Teniers. While Brueghel writes of collaborating with Teniers in his journal, this appears to be the only identified collaboration of the two artists. Conventional microanalysis methods did not resolve the painting's construction chronology. However, confocal x-ray fluorescence microscopy (CXRF) revealed the composition and location of buried paint layers at the panel interfaces by combining depth scans at a number of adjacent lateral positions to produce virtual cross-sections over 20 mm in length. The relationship of the paint layers at the panel interfaces provided evidence for the armor panel having been painted separately and prior to the rest of the composition. This data, along with dendrochronological and IRR data, provided a chronology of construction for the painting that provided additional evidence for a Brueghel attribution. An overview of the CXRF technique will be provided along with a discussion of how CXRF data relates to data collected using SEM-EDS, FTIR, Raman, conventional XRF, x-radiography, IRR, and dendrochronology.
Combinatorial Approach to Materials Fabrication from Higher Hierarchies of Rosette Nanotubes
Authors: Tikhomirov Grigory , Fenniri Hicham
Published: April 2011

The self-assembly of six self-complimentary Guanine – Cytosine hybrid heterocycles bearing hydrophobic substituents has been studied using combinatorial approach in eight solvents under different conditions. The parameters that were varied include: the structure of the self-assembling module, its concentration, the solvent, temperature, and time of self-assembly. scanning electron microscopy (SEM) was used as a screening tool. A wide variety of interesting morphologies was found. The most interesting structures were studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray powder diffraction (XRD).
Damping Characteristics of Commensurate Double-Walled Carbon Nanotube Oscillators
Authors: Ooi Y. , Shintani K.
Published: April 2011

The intertube oscillations of double-walled carbon nanotubes (DWNTs) are investigated using molecular-dynamics (MD) simulation. The inner and outer tubes of model DWNTs have chiral indices of armchair type. The intertube oscillations are damped owing to energy dissipation. The logarithmic decrements and frequencies of the damped oscillations are calculated. The results show that the logarithmic decrement increases with increasing the tube diameter and decreases with increasing the tube length.
Investigating the Growth Process of Vertically Aligned Single-Walled Carbon Nanotubes Synthesized from Alcohol
Authors: Einarsson Erik , Xiang Rong , Ogura Kazuaki , Okawa Jun , Zhang Zhengyi , Maruyama Shigeo
Published: April 2011

We have performed a systematic investigation of the influence of the growth parameters on the synthesis of vertically aligned single-walled carbon nanotubes (VA-SWNTs) by the alcohol catalytic chemical vapor deposition (ACCVD) method. The growth process of the VA-SWNTs was monitored using an in situ optical absorbance technique and the effects of CVD temperature and ethanol pressure on the initial growth rate and the catalyst lifetime were investigated. We found that for a given CVD temperature, there is an optimum pressure at which the VA-SWNT film height is maximized, and this pressure increases with temperature. Below this optimum pressure the growth reaction is first-order, with the arrival of ethanol to the catalyst being the rate-limiting step. The activation energy of the growth was also determined to be approximately 1.5 eV.

The root-growth mechanism of VA-SWNTs by the alcohol CVD method was also confirmed by a two-stage growth process. Following a short growth period using normal ethanol, isotope labeled 13C ethanol was introduced to continue the growth. The location of the 13C was confirmed by resonance Raman spectroscopy, confirming the root-growth mechanism.
High-Yield Synthesis of Vertically Aligned Single-Walled Carbon Nanotubes in Ion-Damage and Radical-Damage Free Atmospheric Pressure PECVD
Authors: Nozaki Tomohiro , Ohnishi Kuma , Okazaki Ken
Published: April 2011

Plasma-enhanced chemical vapor deposition (PECVD) is recognized as one of the viable fabrication techniques of carbon nanotubes (CNTs). However, “CNTs” synthesized in low-pressure PECVD is overwhelmingly carbon nanofibers or multi-walled carbon nanotubes because catalyst and CNTs receive severe damage from ion bombardment: single-walled carbon nanotubes (SWCNTs) has been exclusively synthesized in the thermal CVD regime except few examples. We present atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) for high-purity vertically-aligned SWCNT synthesis, because both ion-damage and radical-damage are preferentially avoided in atmospheric pressure. Tentative reaction mechanism is also discussed based gas phase chemistry analyzed by quadrupole mass spectrometer.
Vertically Aligned Carbon Nanotube Arrays for Room Temperature Gas Sensors
Authors: Rajaputra Suresh , Mangu Raghu , Ma Ning , Clore Patricia , Qian Dali , Andrews Rodney , Phok Sovannary , Lumpp Janet , Singh Vijay
Published: April 2011

Vertically aligned multiwalled carbon nanotube (CNT) arrays were fabricated in anodized aluminum oxide (AAO) templates without the use of a catalyst, using xylene pyrolysis. The CNT arrays in AAO template were integrated into a resistive sensor design. The sensors were found to be highly responsive to NH3 and NO2 with steady state sensitivities of 5% and 10% for 100ppm of NH3 and NO2 respectively, at room temperature. Results were interpreted in terms of the CNTs acting as p-type semiconductors. A study was undertaken to elucidate the dependence of sensitivity on the thickness of the conducting amorphous carbon layers on top and bottom. Recovery of the MWNT gas sensor was studied for different types of desorption techniques. The thickness of the amorphous carbon layer (sheet resistance) was found to be critical in determining the sensor response.
Epitaxial and Non-Epitaxial Heterogeneous Integration Technologies at NGST
Authors: Gutierrez-Aitken Augusto , Chang-Chien Patty , Oyama Bert , Tornquist Kelly , Thai Khanh , Scott Dennis , Sandhu Rajinder , Zhou Joe , Nam Peter , Phan Wen
Published: April 2011

To meet increasingly challenging and complex systems requirements, it is not enough to use one single semiconductor technology but to integrate several high performance technologies in an efficient and cost effective way. Heterogeneous integration (HI) approaches lead to a significant higher design flexibility and performance. In this paper we present some of the HI approaches that are being used and developed at Northrop Grumman Space Technology (NGST) that include selective epitaxial growth, metamorphic growth and wafer level packaging (WLP) technology. More recently we are developing a scaled and selective wafer packaging technique to integrate III-V semiconductors with silicon under the COSMOS DARPA program.
Integrated Optics Utilizing GaN-Based Layers on Silicon Substrates
Authors: Rosenberg Armand , Mastro Michael A. , Caldwell Joshua D. , Holm Ronald T. , Henry Richard L. , Eddy Charles R. , Bussmann Konrad , Kim Mijin
Published: April 2011

It is now apparent that future generations of fast electronics and compact sensors may need to rely increasingly on integrated optical components. But integration of electronics and photonics in today's IC's is challenging. Silicon, the ubiquitous electronic material, is neither ideally suited for most photonic functions nor readily integrated with most of the common photonic materials, such as GaAs. The approach we describe here relies on GaN-based films, which can be grown directly on silicon substrates and hence can be potentially integrated with state-of-the-art Si-based electronics. We have demonstrated the fabrication of GaN structures on silicon wafers ranging in overall size from sub-micron to several millimeters, all containing highly accurate individual features on the nm scale. As proof of concept, we have fabricated GaN optical waveguides and photonic crystals containing optical cavities by patterning GaN membranes grown directly on Si wafers. Our optical cavities were designed to have resonant modes within the spectral region of the broad defect-induced luminescence of GaN. We have measured sharp resonant features associated with these cavities by optically pumping above the GaN band edge, and have compared the data to numerical simulations of the spectra. Our results to date demonstrate the feasibility of fabricating high-quality GaN photonic structures directly on Si wafers, thereby providing a possible path to achieving true integration of electronics and photonics in future generations of IC's.
Electron Traps in n-GaN Grown on Si (111) Substrates by MOVPE
Authors: Ito Tsuneo , Terada Yutaka , Egawa Takashi
Published: April 2011

Deep level electron traps in n-GaN grown by metal organic vapor phase epitaxy (MOVPE) on Si (111) substrate were studied by means of deep level transient spectroscopy (DLTS). The growth of n-GaN on different pair number of AlN/GaN superlattice buffer layers (SLS) system and on c-face sapphire substrate are compared. Three deep electron traps labeled E4 (0.7-0.8 eV), E5 (1.0-1.1 eV), were observed in n-GaN on Si substrate. And the concentrations of these traps observed for n-GaN on Si are very different from that on sapphire substrate. E4 is the dominant of these levels for n-GaN on Si substrate, and it behaves like point-defect due to based on the analysis by electron capture kinetics, in spite of having high dislocation density of the order of 1010 cm−3.
Effect of Top Dielectric Morphology and Gate Material on the Performance of Nitride-based FLASH Memory Cells
Authors: Cacciato Antonio , Breuil Laurent , Van den bosch Geert , Richard Olivier , Rothschild Aude , Furnémont Arnaud , Bender Hugo , Kittl Jorge A. , Van Houdt Jan
Published: April 2011

The nitride-based SONOS cell, for its excellent scalability and process simplicity, is the candidate to push the scaling roadmap for FLASH memories beyond the limit imposed on floating-gate memories by the electrostatic interference between adjacent cells. The traditional SONOS cell consists of a nitride layer (the storage element) encapsulated by two SiO2 layers which isolate the nitride layer from the Si substrate and the poly-Si gate (Poly-Si/SiO2/Si3N4/SiO2/c-Si). However, the thick tunnel oxide necessary to meet the retention requirements imposes a severe limit on the erase performance because of the erase saturation phenomenon. One possibility to guarantee both the erase and the retention performance is the replacement of the top SiO2 layer with materials of higher dielectric constant (high-k dielectric). The presence of a high-k dielectric reduces the electric field across the top dielectric, thus decreasing the unwanted parasitic electron injection from the gate during the erase operation. This will allow the cell to erase deep so to meet a basic requirement for Gigabit multilevel NAND memories. The introduction of high-k materials in the SONOS stack is unfortunately not straightforward. One problem is the Fermi-level pinning at the poly-Si/high-k interface. Another problem is the morphological changes the high-k material undergoes during the device fabrication thermal budget. These changes can modify the k-value and affect the band offset between gate and high-k material. The results may, in both cases, be the decrease of the barrier for electron injection from the gate and, as a consequence, the deterioration of the erase performance. In this paper we study the effect of gate material and of the morphological transformation associated with the high-k post deposition anneal on the erase and the retention behaviour of nitride-based cells. Two different high-k dielectrics are investigated: Al2O3 (which has already been found to be able to significantly improve the erase operation, guaranteeing at the same time excellent endurance and sufficient bake retention) and HfAlO. We show that both for Al2O3 and HfAlO a trade-off exists between erase and retention, higher PDA temperatures being beneficial for erase but detrimental for retention. We also discuss the effect of Fermi level pinning and poly-Si depletion on the erase behaviour and compare the erase performances of several PVD- and AVD-deposited metal gates.
Current Conduction Mechanism for Low-molecular Organic Nonvolatile Memory
Authors: Seo Sungho , Nam Woo-sik , Lee Gon-sub , Park Jea-gun
Published: April 2011

Organic devices fabricated with a top metal layer/conductive organic layer/middle metal layer/conductive organic layer/bottom metal layer structure have been reported to demonstrate nonvolatile memory behavior such as an after writing (Ion)/after erasing (Ioff) performance of > 1 × 101 and a response time of ∼10 ns, when the organic conductive layers were AIDCN (2-amino-4, 5-imidazoledicarbonitrile), Alq3 (Aluminum tris(8-hydroxyquinoline)), or α-NPD. We fabricated an organic nonvolatile memory device with a structure of α-NPD/Al nanocrystals surrounded by Al2O3/α-NPD/Al, where α-NPD was N,N'-bis(1-naphthyl)-1,1'biphenyl4-4''diamine. A layer of Al nanocrystals, confirmed by a 1.25-MV high voltage transmission-electron-microscope, was uniformly produced between the α-NPD layers by Al layer evaporation at 1.0 Å/sec on the α-NPD followed by O2 plasma oxidation. We confirmed a conduction bistability of ∼102 and a threshold voltage for a set state of 3 V. Al nanocrystals surrounded by amorphous Al2O3 were formed in the α-NPD. They presented seven different reversible current paths for an electron charge or discharge on the nanocrystals. The current slightly increased with an applied bias from 0 V to Vth (a high resistance state (Ioff)), abruptly increased with an applied bias from Vth to Vp, decreased with an increasing applied bias from Vp to Ve (a negative differential resistance (NDR) region), and slightly increased with an applied bias above Ve. After sweeping the first applied voltage from 0 to 10 V (erase), a second applied bias was swept from 0 to Vp (program), where the current followed a high resistance state (Ioff). Next, a third applied bias was swept from 0 to Vp again, where the current followed a low resistance state (Ion). Surprisingly, the ratio of Ion to Ioff was ∼1×102, which is enough current difference to be nonvolatile memory behavior. These I-V characteristics under a positive applied bias were symmetrically repeated under a negative applied bias. All the current sweeping paths were reproducible and symmetrical for an applied bias polarity. In particular, our device demonstrated multi-level nonvolatile memory behavior. It also revealed the current conduction mechanism for each of its operation regions. We observed that the high resistance and low resistance regions followed space-charge-limited current conduction, the Vth to Vp and VNDR to Ve regions followed precisely thermionic-field-emission current conduction, and the above Ve regions followed space-charge-limited current conduction.
Process Optimization of Ni Nanocrystals Formation Using O2 Plasma Oxidation to Fabricate Low-molecular Organic Nonvolatile Memory
Authors: Nam Woo Sik , Lee Gon-Sub , Seo Sung Ho , Park Jea Gun
Published: April 2011

We fabricated organic nonvolatile memory with a device structure of Al/Alq3 (aluminum tris (8-hydroxyquinoline))/Ni nanocrystals surrounded by NiO/Alq3/Al. We obtained the best bistable switching characteristics at a 30-nm Alq3 thickness, 0.1-Å/sec evaporation rate, and 10-nm Ni nanocrystal layer thickness. The electrical behavior of the bistable switching devices was obtained by sweeping the voltage from 0 to 10 V. Our devices showed excellent bistable memory characteristics, such as a Vth of 2 V, Vp of 3 V, Ve of 5 V, and Ion/Ioff ratio of greater than 104. We found that a region of negative differential resistance exists between Vp and Ve.
CVD of Amorphous GeTe Thin Films
Authors: Chen Philip S , Hunks William J , Stender Matthias , Chen Tianniu , Stauf Gregory T , Xu Chongying , Roeder Jeffrey F
Published: April 2011

This is the first submission
Molecular Electronics with Large-area Molecular Junctions
Authors: Akkerman Hylke B. , Kronemeijer Auke J. , Blom Paul W. M. , van Hal Paul , de Leeuw Dago M. , de Boer Bert
Published: April 2011

A technology is demonstrated to fabricate reliable metal-molecule-metal junctions with unprecedented device diameters up to 100 μm. The yield of these molecular junctions is close to unity. Preliminary stability investigations have shown a shelf life of years and no deterioration upon cycling. Key ingredients are the use of a conducting polymer layer (PEDOT:PSS) sandwiched between a bottom electrode with a self-assembled monolayer (SAM) and the top electrode to prevent electrical shorts, and processing in lithographically defined vertical interconnects (vias) to prevent both parasitic currents and interaction between the environment and the SAM [1].

Modeling the current–voltage (I–V) characteristics of alkanedithiols with the Simmons model showed that the low dielectric constant of the molecules in the junction results in a strong image potential that should be included in the tunneling model. Including image force effects, the tunneling model consistently describes the current-voltage characteristics of the molecular junctions up to 1 V bias for different molecule lengths [2].

Furthermore, we demonstrate a dependence of the I–V characteristics on the monolayer quality. A too low concentration of long alkanedithiols leads to the formation of looped molecules, resulting in a 50-fold increase of the current through the SAM. To obtain an almost full standing-up phase of 1,14-tetradecanedithiol (C14) a 30 mM concentration is required, whereas a 0.3 mM concentration leads to a highly looped monolayer. The conduction through the full standing-up phase of C14 and C16 is in accordance with the exponential dependence on molecular length as obtained from shorter alkanedithiols [3].

Finally, a fully functional solid-state molecular electronic switch is manufactured by conventional processing techniques. The molecular switch is based on a monolayer of photochromic diarylethene molecular switches. The monolayer reversibly switches the conductance by more than one order of magnitude between the two conductance states via optical addressing. This reversible conductance switch operates as an electronic ON/OFF switch (or a reprogrammable data storage unit) that can be optically written and electronically read [4].
Studies of Charge Transport Properties in P3HT/ZnO Composites Using Photoinduced Charge Extraction by Linearly Increasing Voltage Technique
Authors: Chellappan Vijila , Zhu Furong , Liu Minghui , Loh Kian Ping
Published: April 2011

The charge transport properties in a mixture of regio-regular (poly 3-hexylthiophene) (RR-P3HT) and Zinc Oxide nano particle (ZnO) have been studied using the photoinduced charge extraction by linearly increasing voltage (PhotoCELIV) technique. We have studied the effect of ZnO nanoparticle size (12 nm and 50 nm) on the charge transport properties by fixing the composition ratio of P3HT/ZnO hybrid. The PhotoCELIV mobility in P3HT/50nm-ZnO at room temperature is found to be 7.8×10−5cm2/Vs at an applied electric field of 2.5 × 104 V/cm, which increases to 1.7×10−4cm2/Vs for P3HT/12nm-ZnO composite. The temperature and electric field dependence of charge mobility in these composites have been studied and analysed using Gaussian disorder formalism. The obtained results suggest that the charge transport properties in P3HT/ZnO composite, at low ZnO concentrations, can be tuned by varying the size of the nanoparticle.
Transistor Performance and Film Structure of Hexabenzocoronene Derivatives
Authors: Mori Tomohiko , Kikuzawa Yoshihiro , Umemoto Kazuhiko , Nozaki Hiroshi , Seno Yoshiki , Takeuchi Hisato
Published: April 2011

Hexabenzocoronene (HBC) derivatives that are designed to self-assemble into lamellar aggregates were synthesized. The derivatives were deposited as an active layer in an organic field-effect transistor (OFET) using vacuum sublimation. The dihexyl and tetrahexyl derivatives (2H-HBC, 4H-HBC) increased the field-effect mobilities and on/off ratios by a factor of 10 or more compared to unsubstituted HBC and hexahexyl-hexabenzocoronene (6H-HBC). The crystal and thin film structures were determined by powder x-ray diffraction and grazing incidence X-ray diffraction (GIXD). The data indicate that 2H-HBC and 4H-HBC self-assemble into lamellar aggregates. 2H-HBC forms layers of aromatic cores that are sandwiched by the layers of hexyl groups, which is a preferable crystal structure for carrier transport. The good OFET performance could be explained by the self-assembly in lamellar aggregates of 2H-HBC and 4H-HBC, in contrast to self-assembly in the columnar aggregate of 6H-HBC and the low self-assembling properties of unsubstituted HBC.
Effect of Tensile Deformation on the Grain Size of Annealed Grain Non-Oriented Electrical Steel
Authors: Salinas B. J. , Salinas A.
Published: April 2011

An experimental study on the effect of tensile deformation on recrystallized grain size has been carried out in order to establishing the optimal deformation needed to accelerate grain growth during final annealing of semi-processed non-oriented Si-Al, low C electrical steel sheets. The material is deformed in tension to strains from 3 to 20% and then air-annealed at temperatures between 700 and 900 °C. The results show that the critical deformation for recrystallization (8%) is independent of annealing temperature. However, the critical recrystallized grain size increases with annealing temperature from 160 to 240 μm. After that, the grain size decreases exponentially with increasing deformation. Abnormal grain growth is observed in samples annealed at 700 °C after strains in the range from 7 to 12%. This type of behavior is also observed in specimens annealed at 800 and 900 °C, however, in this case the pre-strain range is expanded to 3–12%. Normal grain growth is observed in samples pre-deformed to strains larger than 12%. In this case, the final grain size after 2 hour anneal is about 55 μm, also independent of annealing temperature. The possible implications of these results on the magnetic properties of these materials are discussed.
Rheological characterization and tape casting of aqueous zircon slips
Authors: León Carriedo M. , Gutiérrez Chavarría C. A. , Rodríguez Galicia J. L. , Pech Canul M. I. , López Cuevas J.
Published: April 2011

In this work, a commercial zircon flour of 99% purity and mean particle size of 10μm is used. Suspension stabilization process is carried out using the electrostatic stabilization mechanism at pH 11 employing Tetramethylammonium hydroxide (TMAH). Tape casting suspensions are formulated with binding systems obtained by the combination of polyvinyl alcohol with polyethylene glycol, additionally the binding system is added at different binder:plasticizer ratio ranging from 1:1 to 3:1. Suspensions are characterized rheologically determining its type and flow properties by obtaining flow and viscosity curves. Suspensions are tape cast on vinyl-acetate substrates and are dried at room conditions to determine some physical properties of the obtained tapes and to correlate the rheological with the physical properties. The experimental results show that tape casting suspensions have a shear thinning flow type, yield points and flow indexes varying as a function of binder system combination and binder:plasticizer ratio. Also, the binder system has a strong influence on the green tapes characteristics.
Dynamic Behaviour of Lead Nanoparticles in A Dielectric Matrix
Authors: Cheyssac P. , Kofman R. , Merli P. G. , Migliori A. , Stella A.
Published: April 2011

In this paper we present electron microscopy results near and below the melting temperature, both in dark field and high resolution mode, of lead nanoparticles embedded in a dielectric matrix of amorphous SiOx. Three different size dependent regimes are distinguished. Indications of solid particles rotations as well as of a new phenomenon amenable to spontaneous solid-liquid phase fluctuations will be briefly discussed.
Holographic Atom Imaging from Experimental Photoelectron Angular Distribution Patterns
Authors: Terminello L. J. , Lapiano-Smith D. A. , Barton J. J. , Petersen B. L. , Shirley D. A.
Published: April 2011

One of the most challenging areas of materials research is the imaging of technologically relevant materials with microscopic and atomic-scale resolution. As part of the development of these methods, near-surface atoms in single crystals were imaged using core-level photoelectron holograms. The angle-dependent electron diffraction patterns that constitute an electron hologram were two-dimensionally transformed to create a three dimensional, realspace image of the neighboring scattering atoms. We have made use of a multiplewavenumber, phased-summing method to improve the atom imaging capabilities of experimental photoelectron holography using the Cu(001) and Pt(111) prototype systems. These studies are performed to evaluate the potential of holographic atom imaging methods as structural probes of unknown materials.
Imaging of Buried Si and Si:Ge Surface Structure Under Amorphous Ge Films by Plan View Transmission Electron Microscopy
Authors: Hellman Olof C.
Published: April 2011

Real space plan-view Transmission Electron Microscopy (TEM) of the interfacial structure at the amorphous-Ge / Si (111) interface is presented. Ge is deposited at between room temperature and 150°C on either a 5×5 or 7×7 reconstructed surface. Conventional Plan-view TEM analysis reveals microstructural details such as surface steps, reconstruction phase shift boundaries and the reconstruction itself buried under the amorphous film, features which have previously been seen only as clean surfaces in UHV. Also imaged are small regions where Ge grows epitaxially on the Si surface above room temperature. These are seen to appear preferentially at steps and phase shift boundaries.
Nanostructural Studies by MÖssbauer Spectroscopy
Authors: Papaefthymiou Georgia C.
Published: April 2011

Application of 57Fe MÖssbauer spectroscopy to the determination of magnetic structural parameters relevant to nanostructural studies is discussed. Variable temperature and applied magnetic field strength investigations are considered in order to illustrate the power of the technique in rendering a microscopic picture of the internal spin structure and dynamical spin relaxation phenomena associated with nanoscale systems. Examples from biology and chemistry, where iron aggregates of nanometer dimensions are encountered, are presented.
Compositions and Chemical Bonding in Ceramics by Quantitative Electron Energy-Loss Spectrometry
Authors: Bentley J. , Horton L.L , Mchargue C.J. , Mckernan S. , Carter C.B. , Revcolevschi A. , Tanaka S. , Davis R.F.
Published: April 2011

Quantitative electron energy-loss spectrometry was applied to a range of ceramic materials at a spatial resolution of <5 nm. Analysis of Fe L23 white lines indicated a low-spin state with a charge transfer of ∼1.5 electrons/atom onto the Fe atoms implanted into (amorphized) silicon carbide. Gradients of 2 to 5% in the Co:O stoichiometry were measured across 100-nm-thick Co3O4 layers in an oxidized directionally solidified CoO-ZrO2 eutectic, with the highest O levels near the ZrO2. The energy-loss near-edge structures were dramatically different for the two cobalt oxides: those for Co3O4 have been incorrectly ascribed to CoO in the published literature. Kinetically stabilized solid solubility occurred in an AIN-SiC film grown by low-temperature molecular beam epitaxy (MBE) on α(6H)-SiC, and no detectable interdiffusion occurred in couples of MBE-grown AIN on SiC following annealing at up to 1750°C. In diffusion couples of polycrystalline AIN on SiC, interfacial 8H sialon (aluminum oxy-nitride) and pockets of Si3N4-rich β'sialon in the SiC were detected.
Spectroscopic Characterization of Nanoscale Modification of Passivated Si(100) Surface by STM
Authors: PÉRez-Murano F. , Barniol N. , Aymerich X.
Published: April 2011

The electrochemical modification of H-passivated Si(100) surface is produced and characterized by Scanning Tunneling Microscopy and Spectroscopy (STM/STS) operating in air. In order to better understand this nanometer scale modification, we have characterized spectroscopically the modified region. From the current-voltage (I/V) curves, dI/dV versus V curves and tip to sample spacing versus voltage (s/V) curves (at constant current) we have concluded that the modification induces a local electrochemical change on the surface, which in turn produces both, a decrease of the local density of surface states and a variation of the band bending in the silicon surface.
Microtribological Studies by Using Atomic Force and Friction Force Microscopy and its Applications
Authors: Bhushan Bharat , Koinkar Vilas N. , Ruan J.
Published: April 2011

We have used atomic force microscopy (AFM) and friction force microscopy (FFM) techniques for microtribological studies including microscale friction, nanowear, nanoscratching and nanoindentation hardness measurements. The microscale friction studies on a gold ruler sample demonstrated that the local variation in friction correspond to a change of local surface slope, and this correlation is explained by a friction mechanism. Directionality effect is also observed as the sample was scanned in either direction. Nanoscratching, nanowear and nanoindentation hardness studies were performed on single-crystal silicon. Wear rates of single crystal silicon are approximately constant for various loads and test duration. Nanoindentation hardness studies show that AFM technique allows the hardness measurements of surface monolayers and ultra thin films in multilayered structures at very shallow depths and low loads. The AFM technique has also been shown to be useful for nanofabrication.
Reliability of Optical Coatings Submitted to a High Power Continuous Wave Laser Beam
Authors: Dijon Jean , Duloisy E. , Hue J. , Ignat M.
Published: April 2011

This paper shows experimental results concerning the life time of mirrors irradiated with a continuous wave CO2 laser. An experimental process and a possible mecanism of degradation are discussed.
Hrem Structure Characterization of Relaxed Interfaces in Covalently Bonded Materials
Authors: Scheerschmidt Kurt
Published: April 2011

Multi-layer semiconductor structures (quantum wells and grain boundaries) grown by molecular beam epitaxy (MBE) as well as precipitates in glasses are investigated by high resolution electron microscopy (HREM) providing local atomic information at the relaxed interfaces. The interpretation of the micrographs requires methods of image analysis and the computer simulation of the HREM contrast by calculating the electron beam specimen interaction of a theoretical structure model, and by subsequently considering the electron-optical process. The relaxed atomic structures of the interfaces are modelled by molecular dynamics and energy minimization with the bonding forces and the parameters of the pair and three-body potentials being varied. Possibilites will be discussed of revealing the compositional variations and the elastic deformations at the interfaces by HREM imaging under special imaging conditions.
X-Ray Diffraction Determination of the Effect of Passivations on Stress in Patterned Lines of Tungsten
Authors: Maniguet L. , Ignat M. , Dupeux M. , Bacmann J.J. , Normandon Ph.
Published: April 2011

The determination by X-ray diffraction of the elastic strain tensors and the corresponding stress tensors in patterned lines of tungsten has been performed to investigate the effect of various passivation. For unpassivated lines, the stresses are biaxial and decrease with decreasing line width. Passivation over patterned lines results in triaxial tensile stress. The stress along the line is not changed by the passivation. The stress across the line decreases as the line width decreases. The third component of stress, perpendicular to the surface, which appears with the passivation, increases with decreasing line width. High compressive intrinsic stress in the passivation does not result in high tensile stress in the metal line.
Impact of Various In Situ Preoxidation Process Perturbations on Gate Oxide Quality
Authors: Roy P. K. , Weinhoffer M. , Dyas R. L. , Meester S.
Published: April 2011

This work describes an orthogonal array (OA8) designed experiment involving several insitu process perturbations during oxidation to develop a 90 Å gate oxide for 0.5μm CMOS technology. The biggest impactors were (i) the insitu preoxidation anneal at oxidation temperature, Tox, (ii) 90% N2 dilution of the ambient during ramp-up, and (iii) lowering the Tox to 850°C. Significant improvements in leakage, breakdown, and wear-out characteristics of the oxide are probably due to the reduction of poor quality ramp oxide grown by 90% N2 dilution and improved Si/SiO2 interfacial substructure attained by the insitu preoxidation anneal.
Line width Dependence of Stress Relaxation and Yield Behavior of Passivated Al(Cu) Lines
Authors: Yeo I.-S. , Anderson S.G.H. , Liao C.-N. , Jawarani D. , Kawasaki H. , Ho P.S.
Published: April 2011

Stress relaxation behavior of thermally induced stresses in passivated line structures is strongly influenced by the metal yield strength. For some line geometries, stress relaxation can lead to void formation. In this study, bending beam measurements have been carried out to measure the thermal stress and stress relaxation behavior of passivated Al(l wt.% Cu) line structures with 3, 1, and 0.5 µm line widths. Our results reveal that stress relaxation in Al(Cu) films and lines shows log(time) kinetics consistent with a thermally activated dislocation glide mechanism. The kinetics of stress relaxation depend on line geometry and temperature, which can be explained by a combined effect of temperature (mass transport) and shear stress (driving force).