bluuebunny/crossref_metadata_2025 huggingface dataset:
Early seral hardwood vegetation increases adult and fledgling bird abundance in Douglas-fir plantations of the Oregon Coast Range, USA
Authors: Ellis Tana M. , Kroll Andrew J. , Betts Matthew G.
Published: April 2012

Recent evidence suggests that population declines of bird species associated with early-successional forest conditions may be associated with reduced quality of breeding habitat. Increasing intensity of forest management on private lands and decreased harvest rates on federal lands in the Pacific Northwest, USA, have resulted in a loss of diverse young forest stands, typically called early seral forest. Previous studies suggest that the amount of early seral broadleaf cover within conifer forests is linked to the composition of foliage-gleaning bird communities. However, information regarding productivity and juvenile use of post-breeding habitat in highly modified plantation habitat is lacking. We examined the relationship between vegetation structure resulting from intensive forest management practices and the abundance of five species of leaf-gleaning, neotropical migrants: orange-crowned warbler ( Oreothlypis celata (Say, 1823)), Wilson’s warbler ( Wilsonia pusilla (A. Wilson, 1811)), MacGillivray’s warbler ( Oporornis tolmiei (J.K. Townsend, 1839)), Swainson’s thrush ( Catharus ustulatus (Nuttall, 1840)), and black-headed grosbeak ( Pheucticus melanocephalus (Swainson, 1827)). All species, except MacGillivray’s warbler, showed positive associations with the amount of early seral hardwood cover as fledglings, breeding adults, or both. However, the relative magnitude of these associations varied, suggesting that other factors may also have influenced avian responses. Abundances of breeding pairs and young are likely to show positive responses to management practices that increase early seral hardwood cover in regenerating stands. If adopted at landscape and regional scales, such practices may positively influence population trends of several declining bird species.
Impact of competition from coppicing stumps on the growth of retained trees differs in thinned Eucalyptus globulus and Eucalyptus tricarpa plantations in southeastern Australia
Authors: Forrester David I. , Bertram Courtney A. , Murphy Simon
Published: April 2012

Coppice growth on cut stumps in thinned Eucalyptus plantations has the potential to compete with and reduce the growth of retained sawlog crop trees (SCTs). This study examined to what extent SCT growth was reduced by coppice in two stands in southeastern Australia: (i) a Eucalyptus globulus Labill. plantation thinned at age 10 years and (ii) a slower growing Eucalyptus tricarpa L.A.S. Johnson & K. Hill (syn. Eucalyptus sideroxylon subsp. tricarpa L.A.S. Johnson) plantation thinned at age 62 years. After 5 years, thinning E. globulus from 850 to 400 trees·ha–1 increased the basal area of the largest diameter 200 SCTs·ha–1 (SCT200) by 11% when coppice was removed. There was no significant thinning response by SCT200 when coppice was retained. After 10 years, thinning E. tricarpa from about 600 to 100 trees·ha–1 increased the basal area of the largest diameter 100 SCTs trees·ha–1 (SCT100) by about 10% whether coppice was removed or not. At the time of measurement, coppice contributed 17% and 36% of stand sapwood area in thinned E. globulus and E. tricarpa treatments, respectively, and possibly competed with SCTs for water. This study shows the significant competitive effect that coppice can have in thinned eucalypt plantations and the importance of coppice management to the growth of retained trees.
Environmental relationships with the interannual and seasonal variation of soil respiration in a cedar (Platycladus orientalis) plantation in northern China
Authors: Pang Zhuo , Yu Xinxiao , Zha Tianshan , Jia Guodong , Wu Hailong , Lv Xizhi , Li Yitao , Zhou Bin , Fan Minrui , Song Siming , Zhao Yang , Huang Zhiying , Deng Wenping , Wang Henian , Zhang Yi , Yang Zhige , Fan Dengxing
Published: April 2012

The relationships between soil respiration and environmental factors determine the effect of warming soil on the carbon balance in temperate forest ecosystems and on changes in atmospheric CO2 concentrations. Here, we used 3 years of data regarding soil respiration rates (Rs), soil temperature (Ts), and soil volumetric water content (θ) from a 50-year-old mature cedar ( Platycladus orientalis L.) plantation at Jiufeng Mountain, Beijing, China, to demonstrate the seasonal and interannual variation of Rs dependence on Ts and θ throughout the period 2008–2010. We used the exponential model to calculate the temperature sensitivity indicator Q10 and we examined the annual and seasonal patterns of Rs and Q10. The Rs correlated with Ts annually (p < 0.05). The Rs–Ts exponential relationship was significant in the autumn and winter (p < 0.05), while the combined Ts and θ relationships with Rs were significant in the spring and summer (p < 0.001). The spring Rs anomalies caused by drought appeared to have carryover effects that translated to Rs anomalies in the following summer. Finally, the summer Rs, which was influenced by the coincident precipitation and θ anomalies, determined the magnitude of the annual total amount of soil respiration. This result has implications for how abiotic factors may drive shifts in seasonal patterns of soil respiration under a changing climate.
An examination of stable hydrogen isotope (δD) variation in adult and juvenile feathers from a migratory songbird
Authors: Gow Elizabeth A. , Stutchbury Bridget J.M. , Done T. , Kyser T.K.
Published: April 2012

Stable hydrogen isotopes (δD) can help predict geographic origin of tissue growth but within-site variation of feather δD (δDf) exists. Multiple hypotheses explain δDf variation: moult timing, physiology, and spatio-temporal differences in source deuterium, but there have been few direct tests of these factors. We assessed δDf variation within a breeding population of Wood Thrush ( Hylocichla mustelina (Gmelin, 1789)), by sampling feathers from hatch-year birds, returning adults (after migration), and to eliminate confounding variables from newly grown adult primary feathers during moult. We evaluated potential mechanisms explaining δDf variation by examining intraindividual variation (different feather types), precipitation δD, prey δD, corticosterone (CORT), and breeding productivity. In addition, we directly compared δDf of newly grown primary feathers to δD blood hematocrit (δDb). We found significant differences in δDf between years and age classes and observed no significant intraindividual variation. δDf and δDb were not significantly correlated. CORT weakly contributed to δDf, but there are other factors influencing δDf. Ten percent of all feather samples had outlying δDf values, and were likely grown away from the breeding grounds. Our results document intrapopulation and intraindividual variation of δDf at a single location and indicated that age class and year-to-year differences contributed to high δDf variance.
Long-distance swimming by polar bears (Ursus maritimus) of the southern Beaufort Sea during years of extensive open water
Authors: Pagano A.M. , Durner G.M. , Amstrup S.C. , Simac K.S. , York G.S.
Published: April 2012

Polar bears ( Ursus maritimus Phipps, 1774) depend on sea ice for catching marine mammal prey. Recent sea-ice declines have been linked to reductions in body condition, survival, and population size. Reduced foraging opportunity is hypothesized to be the primary cause of sea-ice-linked declines, but the costs of travel through a deteriorated sea-ice environment also may be a factor. We used movement data from 52 adult female polar bears wearing Global Positioning System (GPS) collars, including some with dependent young, to document long-distance swimming (>50 km) by polar bears in the southern Beaufort and Chukchi seas. During 6 years (2004–2009), we identified 50 long-distance swims by 20 bears. Swim duration and distance ranged from 0.7 to 9.7 days (mean = 3.4 days) and 53.7 to 687.1 km (mean = 154.2 km), respectively. Frequency of swimming appeared to increase over the course of the study. We show that adult female polar bears and their cubs are capable of swimming long distances during periods when extensive areas of open water are present. However, long-distance swimming appears to have higher energetic demands than moving over sea ice. Our observations suggest long-distance swimming is a behavioral response to declining summer sea-ice conditions.
THE RELATIVISTIC MEAN-FIELD EQUATIONS OF THE ATOMIC NUCLEUS
Authors: ROTA NODARI SIMONA
Published: April 2012

In nuclear physics, the relativistic mean-field theory describes the nucleus as a system of Dirac nucleons which interact via meson fields. In a static case and without nonlinear self-coupling of the σ meson, the relativistic mean-field equations become a system of Dirac equations where the potential is given by the meson and photon fields. The aim of this work is to prove the existence of solutions of these equations. We consider a minimization problem with constraints that involve negative spectral projectors and we apply the concentration-compactness lemma to find a minimizer of this problem. We show that this minimizer is a solution of the relativistic mean-field equations considered.
EMBEDDING OF NONCOMMUTATIVE MASSIVE QED
Authors: MONEMZADEH M. , EBRAHIMI AGHILEH S.
Published: April 2012

In this paper, BFT formalism of Proca model in noncommutative space is investigated. Considering that all theories with first class constraint are gauge theories, Proca model in noncommutative space is not a gauge theory in general due to the appearance of second class constraints in it. In present research, the Proca model is converted into a gauge theory using BFT approach by introducing several auxiliary variables which in turn manage to convert the second class constraints to first class ones. Consequently, we apply modified BFT that preserve the chain structure of constraints. Modified BFT has the benefit that it gives less number of independent gauge parameters and we obtain gauge generating function and infinitesimal gauge variation of fields in Proca model. As results, we investigate partition function of this model and embedded noncommutative Proca is ready to quantize in usual way.
MEDICAL IMAGES SEGMENTATION USING ACTIVE CONTOURS DRIVEN BY GLOBAL AND LOCAL IMAGE FITTING ENERGY
Authors: WANG HAIJUN , LIU MING
Published: April 2012

In this paper, we propose a global and local Chan-Vese model which utilizes both global image information and local image information for image segmentation. We define an energy functional with a global term, which incorporates global image information to improve the robustness of the proposed method, and a local term which is dominant near the object boundaries. The regularization term is added to the energy functional to avoid the time-consuming re-initialization. The comparisons with the C–V model, LBF model and LGIF model show that our model can segment images with intensity inhomogeneity in less iteration steps and take less time.
Hafnia-Based Luminescent Insulator for Phosphor Applications
Authors: Khomenkova Larysa , An Y.-T. , Labbé C. , Portier X. , Gourbilleau F.
Published: April 2012

Pure and doped hafnia-based films were fabricated by RF magnetron sputtering and their microstructure, optical and luminescent properties were investigated versus annealing treatment. It was observed a phase separation in Si-rich-HfO2 films at 900-1100°C resulted in the formation of HfO2 and SiO2 phases, as well as pure silicon clusters. A light emission in the orange-red spectral range was observed from Si-rich-HfO2 samples contrary to their pure counterparts. The correlation of the peak position of red photoluminescence with silicon cluster sizes allowed gives the evidence of the carrier recombination in silicon clusters. The comparison of Er-doped-HfO2 and Er-doped Si-rich-HfO2 films showed an enhancement of rare-earth emission efficiency due to an effective energy transfer from Si-clusters.
The Influence of Carbon on the Structure and Photoluminescence of Amorphous Silicon Carbonitride Thin Films
Authors: Khatami Zahra , Wilson Patrick R. , Dunn Kayne , Wojcik J. , Mascher P.
Published: April 2012

A systematic study on silicon carbonitride matrices has been carried out to determine contributions of carbon on their luminescence process, chemical composition, and electronic structural properties. Thin films were deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition using SiH4, N2, and CH4 process gases. The film structure and composition were determined through Rutherford backscattering spectrometry (RBS), elastic recoil detection (ERD), photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was confirmed that increases in carbon concentration resulted in the enhancement of the photoluminescence properties broadly spread over the visible range.
Surface Potential Measurements of Reconfigurable p-n Junctions in Graphene
Authors: Wang Yunfei , Geer Robert E.
Published: April 2012

The direct surface potential measurement of reconfigurable graphene p-n junctions in exfoliated graphene deposited on a buried split-gate test structure is reported. The experimental geometry permitted direct imaging of the Fermi level variation across the electrostatically-doped p-n junction using Kelvin Probe Force Microscopy (KPFM). The measured graphene p-n junction doping profile and junction width are in good agreement with predictions from finite-element calculations.
Aberration Corrected Microscopy of CVD Graphene and Spectroscopic Ellipsometry of Epitaxial Graphene and CVD Graphene for Comparison of the Dielectric Function
Authors: Nelson Florence , Prasad Sinha Dhiraj , Comfort Everett , Lee Ji Ung , Diebold Alain C. , Sandin Andreas , Dougherty Daniel B. , Rowe Jack E.
Published: April 2012

Chemical Vapor Deposition (CVD) on metallic foils and the thermal decomposition of SiC have become two of the dominant fabrication methods of large area graphene due to their industrial scalability. The work will present STEM imaging of CVD graphene performed at 60 kV with atomic resolution achieved through aberration correction. Single-crystal areas are identified as well as defect structures. Spectrscopic Ellipsometry (SE) is used to extract the dielectric function (complex refractive index) of graphene from both growth methods. Epitaxial graphene on SiC sits on a buffer layer, the dielectric function of which is also measured with SE for comparison to the pure sp2-bonded graphene layers.
Modeling the Growth of SWNTs and Graphene on the Atomic Scale
Authors: Neyts Erik C. , Bogaerts Annemie
Published: April 2012

The possibility of application of nanomaterials is determined by our ability to control the properties of the materials, which are ultimately determined by their structure and hence their growth processes. We employ hybrid molecular dynamics / Monte Carlo (MD/MC) simulations to explore the growth of SWNTs and graphene on nickel as a catalyst, with the specific goal of unraveling the growth mechanisms. While the general observations are in agreement with the literature, we find a number of interesting phenomena to be operative which are crucial for the growth, and which are not accessible by MD simulations alone due to the associated time scale. Specifically, we observe metal mediated healing and restructuring processes to take place, reorganizing the carbon network during the initial nucleation step. In the case of carbon nanotube growth, this leads to the growth of tubes with a determinable chirality. In the case of graphene formation, we find that graphene is only formed at temperatures above 700 K. These results are of importance for understanding the growth mechanisms of these carbon nanomaterials on the fundamental level.
Demonstration of Single Crystal GaAs Layers on CTE-Matched Substrates by the Smart Cut Technology
Authors: Jouanneau Thomas , Bogumilowicz Yann , Gergaud Patrice , Delaye Vincent , Barnes Jean-Paul , Klinger Vera , Dimroth Frank , Tauzin Aurélie , Ghyselen Bruno , Carron Véronique
Published: April 2012

Templates made of a thin single crystal GaAs layer on CTE-matched substrate (sapphire) have been realized using the Smart CutTM technology. These templates can withstand high processing temperatures thanks to the CTE matching between the GaAs thin film and its support, and therefore can be used for many applications since they require no specific restriction concerning thermal treatments. The GaAs templates have been compared to conventional bulk GaAs substrates. TEM images and XRD spectra show similar crystalline quality. AFM measurements show a similar surface microroughness. Photoluminescence of a AlGaAs double heterostructure grown by MOCVD on the GaAs template shows the same intensity as a reference structure on bulk GaAs. Therefore, the GaAs templates can replace GaAs bulk substrates in various domains such as photonics devices (solar cell, laser) or high frequency electronics.
Germanium on Insulator (GOI) Structure Using Hetero-Epitaxial Lateral Overgrowth on Silicon
Authors: Nam Ju Hyung , Fuse Takashi , Nishi Yoshio , Saraswat Krishna C.
Published: April 2012

A technique to achieve germanium on insulator (GOI) structure on Si platform using hetero-epitaxial lateral overgrowth is presented. On (100) Si wafer, SiO2 is thermally grown, and patterned to locally reveal Si surface on which Ge is grown via selective epitaxy. After filling the growth window, Ge starts growing laterally, and adjacent Ge crystals coalesce with each other on SiO2. After the coalescence, <100> directional growth is made dominant, to fill the valley and planarize the surface. Thus, single crystalline Ge film sitting on SiO2 can be made for GOI applications.
Sub-100nm Non-Planar 3D InGaAs MOSFETs: Fabrication and Characterization
Authors: Gu Jiangjiang J. , Ye Peide D.
Published: April 2012

InGaAs MOSFETs have been considered promising candidate for post-Si logic devices beyond 14nm technology node. To meet the increasing demand in electrostatic control at sub-100nm channel lengths, non-planar 3D structures have been introduced to the fabrication of InGaAs MOSFETs. In this paper, the fabrication and characterization of various non-planar 3D InGaAs MOSFETs have been demonstrated and summarized, including InGaAs heterostructure FinFETs, InGaAs-on-nothing nanowire MOSFETs, and InGaAs gate-all-around nanowire MOSFETs. It is shown that the implementation of 3D structure greatly reduces short channel effect and improves scalability of InGaAs MOSFETs. The gate-all-around nanowire structure has been fabricated by a novel top-down approach for the first time and is found to offer great scalability down to at least 50nm channel length with good transport property, making InGaAs gate-all-around nanowire MOSFETs strong candidate for ultimately scaled III-V logic technology.
Non-Destructive, Large-Scale Imaging of Anti-Phase Disorder in GaP Epilayers on Si(001) Using Low-Energy Electron Microscopy
Authors: Borkenhagen Benjamin , Döscher Henning , Hannappel Thomas , Lilienkamp Gerhard , Daum Winfried
Published: April 2012

We introduce low-energy electron microcopy (LEEM) as a surface-sensitive technique for the investigation of anti-phase disorder and other defects in III-V semiconductor layers on Si(100) and present first results for 40 nm GaP films on Si(100). Using an actively pumped ultra-high vacuum transfer chamber, we were able to preserve the surface structure and chemical composition of the MOVPE-grown GaP films on Si(100) during transfer from the MOVPE reaction chamber to the remote electron microscope. Applying dark- and bright-field imaging modes we demonstrate the unique potential of LEEM for non-invasive, fast and large-scale inspection of anti-phase disorder and surface defects in heteroepitaxial III-V systems on Si.
(Invited) Semiconductor Nanocrystals Embedded in High-k Materials
Authors: Benner Frank , Haas Sven , Schneider Frank , Klemm Volker , Schreiber Gerhard , Von Borany Johannes , Heitmann Johannes
Published: April 2012

The combination of high-k materials and nanocrystalline semiconductors leads to remarkable properties for various applications. The phase separation of ZrGeO and ZrSiO films in superlattice geometries were investigated. In case of the Si containing films, round-shaped clusters within a crystalline ZrO2 matrix have been observed after annealing at 1000 °C. The appearance of nanocrystalline Si could not be shown, whereas amorphous clusters within the crystalline ZrO2 matrix were formed. For the Ge containing films, the formation of Ge nanocrystals was observed after annealing at 650 °C. In both material systems the ZrO2 matrix crystallized in the tetragonal phase.
(Invited) Low-Temperature Growth of Ge Nanowires by Vapor-Liquid-Solid Chemical Vapor Deposition
Authors: Simanullang Marolop , Seyhan Ayse , Usami Koichi , Kodera Tetsuo , Kawano Yukio , Oda Shunri
Published: April 2012

This paper reports the growth of the germanium nanowires (Ge NWs) with a single-step temperature method via vapour-liquid-solid (VLS) mechanism in the low pressure chemical vapour deposition (CVD) reactor at 300, 280 and 260°C. The Ge NWs grown at 300°C tend to have a tapered structure and the sidewalls of the nanowires were observed to be decorated with gold. The tapering was caused by the uncatalysed deposition of Ge via CVD mechanism at the sidewalls of the nanowires and significantly minimised at 260°C which leads to the formation of straight and ultra-thin Ge NWs. The sidewalls of the Ge NWs grown at 260°C were also observed not to be decorated with gold. The Ge NWs grown from 0.1-nm-thick Au at 260°C had diameter as small as ~3 nm which offers an opportunity to fabricate high-performance p-type ballistic Ge NW transistor and to realise nanowire solar cell with higher efficiency.
An Extended Unified Schottky-Poole-Frenkel Theory to Explain the Current-Voltage Characteristics of Capacitors Using High-k Dielectric Materials
Authors: Lau Wai Shing
Published: April 2012

Historically, there is a controversy regarding the current-voltage (I-V) characteristics of thin film MIM (metal-insulator-metal) capacitors, which is quite frequently modeled by either the Schottky model or the Poole-Frenkel model. In this letter, the author points out that the two models actually can be unified. The physics underlying this model involves a non-uniform distribution of defect states such that a very large quantity of defect states exist at the two interface of the MIM capacitor while the density of defect states in the insulator bulk is relatively low, resulting in an M/n-i-n/M structure. This unified Schottky-Poole-Frenkel model can be further extended to include other effects like space charge limited current, tunneling, etc. Evidence supporting this theory will be provided.
(Invited) FinFET Flash Memory Technology
Authors: Liu Yongxun , Kamei Takahiro , Matsukawa Takashi , Endo Kazuhiko , O'uchi Shinichi , Tsukada Junichi , Yamauchi Hiromi , Ishikawa Yuki , Hayashida Tetsuro , Sakamoto Kunihiro , Ogura Atsushi , Masahara Meishoku
Published: April 2012

The crystal-Si and poly-Si fin-channel flash memories with a thin n+-poly-Si floating-gate (FG) layer have successfully been fabricated, and their electrical characteristics have systematically been investigated. It was experimentally found that the better short-channel effect (SCE) immunity, the smaller threshold voltage (Vt) variations and a higher program speed are obtained in the crystal-Si fin-channel tri-gate (TG)-type flash memories than in the double-gate (DG)-type ones. It was also confirmed that split-gate crystal-Si fin-channel flash memories show highly suppressed over-erase as compared to that in stack-gate memories. Moreover, it was found that Vt variation in the poly-Si fin-channel flash memories after a program/erase (P/E) cycle became comparable to that in the crystal-Si fin-channel memories. The measured source-drain breakdown voltage (BVDS) was higher than 3.2 V even the gate length (Lg) was down to 76 nm. The developed technology is very useful for the fabrication of scaled NOR-type flash memory.
Analysis of Cycling Induced Interface Degradation in Si Nanocrystal Memory Devices
Authors: Jiang Dandan , Zhang Manhong , Huo Zongliang , Sun Zhong , Wang Yong , Zhang Bo , Chen Junning , Liu Ming
Published: April 2012

This work has investigated the interface degradation of Si-nanocrystal memory devices under Fowler-Nordheim program/erase cycling. The evolution of the high-frequency capacitance-voltage curves pointed out that the mean density of interface traps had an unsymmetrical distribution around the surface intrinsic Fermi level (Eis) and the acceptor-type interface traps generated much faster than the donor-type ones during the cycling stress. It was further supported by the charge pumping measurement under several stress conditions. The energy distribution of the interface traps near Eis had a clear step-like shape with a higher density of acceptor-type interface traps. The results show that the generation of acceptor-type interface traps played a dominant role in the interface degradation.
Modeling of Copper Diffusion in Amorphous Aluminum Oxide in CBRAM Memory Stack
Authors: Sankaran Kiroubanand , Goux Ludovic , Clima Sergiu , Mees Maarten , Kittl Jorge A. , Jurczak Malgorzata , Altimime Laith , Rignanese Gian-Marco , Pourtois Geoffrey
Published: April 2012

First-principles modeling techniques are used to study the diffusion of copper in amorphous alumina (a-Al2O3) for Conductive Bridging Random Access Memories (CBRAM) Pt/CuxTe(1-x)/Al2O3/Si stacks. The enthalpy of injection (Ei) of Cu(+1/+2) and Te(-2/+2) ions into a-Al2O3 have been quantified. We found that the kinetics associated to Cu+1 injection is characterized by a diffusion pre-factor of 5.8×10-4 cm2/s and an activation energy of 0.9 eV in a-Al2O3. The diffusion kinetics of the Te+2 ions is similar to the Cu+1 one.
Ge-Doped Hafnia-Based Dielectrics for Non-Volatile Memory Applications
Authors: Khomenkova Larysa , Portier X. , Carrada M. , Bonafos C. , Sahu B. S. , Slaoui A. , Gourbilleau F.
Published: April 2012

Fully high-k based non-volatile memory structures were fabricated by RF magnetron sputtering technique. The pure HfO2 and HfSiO materials were used as tunnel and/or control layers, whereas HfGeO ones were used as a charge storage node. The capacitance-voltage measurements of HfO2/HfGeO/HfO2 and HfSiO/HfGeO/HfSiO stacks were performed to study the charge trapping characteristics of these structures. The memory effect was observed in both types of MIS capacitors and the optimal annealing treatment was found to be at 610°C for 15 minutes. A memory window of ~7 V at a sweeping voltage of ± 14 V has been achieved, indicating the potential use of these stack structures for non-volatile memory devices.
(Invited) Ozone Assisted ALD of Doped ZnO as a Transparent Metal
Authors: Yuan Hai , Luo Bing , Gladfelter Wayne L. , Campbell Stephen
Published: April 2012

The rapidly escalating cost of indium tin oxide has led to search for lower cost transparent conductor options such as heavily doped zinc oxide. Here we study the donors aluminum (AZO) and gallium (GZO), as well as phosphorus (PZO) which is n-type as-deposited, but converts to p-type with a suitable anneal. We present the results of atomic layer deposition (ALD) of AZO, GZO, and PZO with ozone as the oxidant. The metal-containing precursors were diethyl zinc, trimethyl aluminum, triethylgallium and trimethylphosphite. Homogeneous and layered structures are compared. Homogeneous films with about 2% aluminum or gallium were found to have the lowest resistivity (~0.5 milliohm-cm). For PZO, the lowest resistivity was found to occur for films with 3.2%P when annealed at 750oC (0.46 ohm-cm).
Influence of Forming Gas Annealing on SiO2/Si(100) Interface Structures Formed Utilizing Oxygen Molecules Different from that Utilizing Oxygen Radicals
Authors: Suwa Tomoyuki , Kumagai Yuki , Teramoto Akinobu , Muro Takayuki , Kinoshita Toyohiko , Sugawa Shigetoshi , Hattori Takeo , Ohmi Tadahiro
Published: April 2012

Soft-x-ray-excited angle-resolved photoelectron spectroscopy studies on silicon dioxide films formed utilizing oxygen radicals (ORs) and oxygen molecules (OMs) with or without forming gas annealing (FGA) are reported. The SiO2/Si interface structure formed utilizing ORs were only slightly influenced by FGA. On the other hand, although the thickness of oxide film formed utilizing OMs is weakly influenced by FGA, the FGA-induced nearly 10% decrease in the amounts of Si1+, Si2+, and Si3+ formed utilizing OMs were found. Therefore, the interface structure formed utilizing OMs is influenced by FGA.
Characterization of Strain-Engineered Si:C Epitaxial Layers on Si Substrates
Authors: Yoo Woo Sik , Ishigaki Toshikazu , Ueda Takeshi , Kajiwara Junya , Kang Kitaek , Hung P. Y. , Ang Kah-Wee , Min Byoung-Gi
Published: April 2012

Pseudomorphically grown Si:C thin films on Si(100), with a carbon content ranging from 0.9 to 1.5 at% and thickness from 45 to 84 nm, were prepared by ultrahigh vacuum (UHV) and low pressure (LP) chemical vapor deposition (CVD) and characterized by various non-invasive and non-destructive characterization techniques including high resolution X-ray diffraction (HRXRD), multi-wavelength high resolution Raman spectroscopy, and room temperature (RT) multi-wavelength photoluminescence (PL). Benefits and limitations of these characterization techniques are discussed. Results are shown for similar thicknesses, LP-CVD sample has less total C and remains pseudomorphic while UHV-CVD has higher amount of interstitial C and exhibits the onset of relaxation.
Ultra Low-Temperature Epitaxial Growth of Strained Si Directly on Si Substrates
Authors: Shahrjerdi Davood , Hekmatshoar Bahman , Bedell Stephan W. , Ott John A. , Hopstaken Marinus , Sadana Devendra K.
Published: April 2012

We present a unique ultra low-temperature plasma enhanced chemical vapor deposition process that enables epitaxial growth of compressively strained silicon directly on silicon substrates. The epitaxial layers were structurally examined using high-resolution x-ray diffraction, transmission electron microscopy and secondary ion-mass spectroscopy. The results indicate that the compressive strain of the epitaxial layers stems from the hydrogen incorporation during the growth. In addition, we study the effect of phosphine gas flow on the phosphorus doping incorporation in the epitaxial films at low temperatures. Utilizing our epitaxial process, we demonstrate that heavily phosphorus-doped compressively strained Si films with an active doping concentration of ~2×10^20cm^-3 can be achieved at 150C.
Nanocrystalline MoOx Embedded ZrHfO High-k Memories - Charge Trapping and Retention Characteristics
Authors: Liu Xi , Yang Chia-Han , Kuo Yue , Yuan Tao
Published: April 2012

The nonvolatile memory properties of metal-oxide-semiconductor memory capacitors containing nanocrystalline MoOx embedded ZrHfO high-k gate dielectric have been investigated. The charge trapping capacity and trapping site were investigated using the capacitance-voltage hysteresis and constant voltage stress methods. The memory functions were mainly based on trapping holes at the MoOx site. The current density-voltage curve result confirmed the above charge trapping mechanism and showed the Coulomb blockade phenomena. More than 50% of trapped charges could be retained for more than 10 years. This is a viable dielectric structure for future nanosize memories.
Electrical Improvement of MIS Capacitor with HfAlOx Gate Dielectrics Treated by Dual Plasma Treatment
Authors: Deng I-Chung , Chang Kow-Ming , Chang Ting-Chia , Chang Po-Chun , Huang Bo-Wen , Wu Chien-Hung
Published: April 2012

High dielectric constant materials (high-k) such as Hf-based thin films are the promising candidates for 45-nm CMOS technology. It has been described that nitridation processes could improve thermal stability and dielectric constants of Hf-based dielectrics. Furthermore, fluorine incorporation into high-k dielectric was also proposed in order to suppress leakage current and passivate defects. In this study, we examined dual plasma treatment (CF4 pre-treatment and N2 post-treatment) on HfAlOx thin films in order to improve electrical characteristics. Based on our experimental results, HfAlOx Metal-Insulator-Semiconductor (MIS) capacitor properties such as capacitance density, gate leakage current density, and hysteresis could be successfully improved. Compared to untreated samples, capacitance is 42.5 % higher and gate leakage is suppressed about three orders when dual plasma treatment is used. According to this study, dual plasma treatment would be an effective technology to improve the electrical characteristic of HfAlOx thin films.
Bipolar Resistive Switching Memory Characteristics Using Al/Cu/GeOx/W Memristor
Authors: Maikap Siddheswar , Rahaman S. Z.
Published: April 2012

Low power operations of resistive switching memory using Al/Cu/GeOx/W memristor have been reported for the first time. Under the SET process the copper ions migrate through defects into the GeOx solid-electrolyte and there is the formation of a copper filament by reduction process. However, the RESET process or dissolution of this filament occurs by an oxidation process. Excellent uniformity with narrow distributions of SET/RESET voltages and low resistance states (LRS) are obtained. Furthermore, high resistance ratio of >104 with multi-level (MLC) operation and low SET and RESET powers (~19 and ~ 8.36 µW) are advantages for future high density memory applications.
Mixed Conductors for Electrochemical CO2 Separation
Authors: Xu Nansheng , Zhang Lingling , Zhao Hailei , Huang Kevin
Published: April 2012

One of the major concerns of consuming fossil fuels to produce useful form of energy is the emission of CO2, a greenhouse gas that can cause climate change and ultimately threaten the survival of humanity. Controlling CO2-emission is an urgent but the only practical solution to stabilize CO2 concentration in the atmosphere. In this paper, we report our effort to capture CO2 from a simulated flue gas by utilizing a dual-phase mixed electron and carbonate-ion conducting (MECC) membrane. The obtained CO2 flux density is the highest among the published dual-phase carbonate systems. These results demonstrate the Ag-MC dual-phase composite as a promising high-flux membrane for high-temperature electrochemical CO2 separation from flue gas with high selectivity.
Metallic Nanoparticles and Proton Conductivity: Improving Proton Conductivity of BaCe0.9Y0.1O3-δ and La0.75Sr0.25Cr0.5Mn0.5O3-δ by Ni-doping
Authors: Caldes Maria Teresa , Kravchyk Kostian V. , Benamira Messaoud , Besnard Nicolas , Joubert Olivier , Bohnke Odile , Gunes Veyis , Jarry Angelique , Dupré Nicolas
Published: April 2012

In this work we have used metallic nanoparticles to improve proton conductivity of the ceramic electrolyte BaCe0.9Y0.1O3-δ (BCY) and of the electrode material La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM). Instead of adding metallic nanoparticles as a separate phase, they were dissolved in the compounds as their oxidized form (Ni2+). The metal nanoparticles precipitated from compounds upon heating under reducing atmosphere. Below 600°C under reducing atmosphere, BaCe0.9-xY0.1NixO3-δ compounds exhibit higher conductivity than BCY. Thus, an increase of one order of magnitude was observed for BaCe0.7Y0.1Ni0.2O3-δ. A protonic contribution to the total conductivity is observed below 600°C. This phenomenon is more pronounced for the compounds containing more nickel in surface which can facilitate the dissociation of hydrogen and the incorporation of protons in the structure. La0.75Sr0.25Cr0.5Mn0.5-xNixO3-δ compounds show also a protonic contribution to the total conductivity below 400°C. NMR results confirmed that these compounds contain protons.
Oxide Ion Conductivity of LaNi0.6Fe0.4O3
Authors: Nishi Mina , Horita Teruhisa , Yamaji Katsuhiko , Yokokawa Harumi , Shimonosono Taro , Kishimoto Haruo , Brito Manuel E. , Cho Do Hyong , Wang F.
Published: April 2012

The oxide ion conductivity of LaNi0.6Fe0.4O3 was studied by oxygen isotope exchange measurement and SIMS at 673 ˜ 1073K in p(O2) = 0.4 ˜ 20 kPa.
Ionically Conducting Ceramics for Soot Oxidation Mechanistic Study with 18O2 Isotopic Exchange
Authors: Lizarraga Leonardo , Obeid Emil , Tsampas Michalis N. , Boréave Antoinette , Steil M.C. , Vernoux Philippe
Published: April 2012

This study shows that Yttria-Stabilized Zirconia (YSZ) is an effective catalyst for soot particles oxidation. Soot oxidation already occurs from 270°C. Temperature-Programmed Oxidation experiments with 18O2 demonstrate the key-role of bulk oxygen species in the oxidation process. To the best of our knowledge, this is the first time that such a result is reported for a purely O2- ionically conducting ceramic without any redox property. We assume that the soot oxidation takes place via a fuel-cell type electrochemical mechanism at the nanometric scale. Electrochemical oxidation of the soot takes place at the soot/YSZ interface while oxygen electrochemical reaction occurs at the triple phase boundary.
La0.6Sr0.4CoO3-δ Thin Films Prepared by Pulsed Laser Deposition as Cathodes for Micro-Solid Oxide Fuel Cells
Authors: Evans Anna , Karalić Sasa , Martynczuk Julia , Prestat Michel , Tölke René , Yáng Zhen , Gauckler Ludwig J.
Published: April 2012

Lanthanum-strontium-cobalt oxide (LSC) thin films fabricated by pulsed laser deposition (PLD) can be used as electrodes for micro-solid oxide fuel cells (micro-SOFCs) in the intermediate temperature range of 450-550 °C. The LSC thin films deposited under a high oxygen chamber pressure are nanocrystalline after thermal treatment at 550 °C and have a nanoporous microstructure. The buckling pattern of the free-standing yttria-stabilised-zirconia (YSZ) membrane influences the survival rate of the free-standing LSC|YSZ|LSC cells. Electrochemical impedance spectroscopy is used to investigate the properties of the LSC/YSZ interface in free-standing quasi-symmetrical LSC|YSZ|LSC membranes. LSC electrodes with a thickness of ~150 nm had an area specific resistance (ASR) of 3.7 Ωcm2 at 550 °C.
Electrical Properties of Transition Metal-Doped (Mn,Co)3O4 Spinels and Their Interaction with Chromia for SOFC Interconnect Coatings
Authors: Liu Yingjia , Kumar C.J. D. , Fergus Jeffrey W.
Published: April 2012

Spinel oxide ceramic coatings have been shown effective to reduce oxidation rate and chromium volatilization of ferritic stainless steels SOFC interconnect. In this work, the effects of transition metal (TM) doping in (Mn,Co)3O4 (TM=Fe) spinels on the reaction with chromia and electrical conductivity at high temperature were studied. Iron additions lead to a decrease in conductivity, but do not increase the extent of reaction except for the higher Fe content of 0.7 in MnCo2-xFexO4. Even at this highest Fe content, Fe was not present in the high-chromium reaction layer.
(Invited) Theory and Application of Nonlinear Electrochemical Impedance Spectroscopy
Authors: McDonald Timothy J. , Adler Stuart
Published: April 2012

This paper provides an overview of the theoretical basis and application of nonlinear electrochemical impedance spectroscopy (NLEIS) to SOFC electrodes. A principle advantage of impedance methods is the ability to delineate processes by time scale. With the addition of NLEIS, it is possible to probe nonlinear response as a function of frequency. This approach can be used to better understand and delineate rates, especially when system behavior drifts with time and/or is unstable upon application of large nonlinear driving forces. This paper reviews the use of NLEIS to identify surface reaction rate laws, probe transport pathways in porous electrodes, and identify the origins of degradation.
Influence of ZnO on the Electrical Properties of YSZ
Authors: Marcomini Raphael F. , Pinatti Ferreira de Sousa Dulcina , Kleitz Michel , Dessemond Laurent , Steil M.C.
Published: April 2012

Impedance spectroscopy was performed on dense YSZ/ZnO composites with a ZnO content varying from 3 to 25 vol% and under different oxygen pressures. Raman spectroscopy showed that the cubic zirconia phase is not fully stable in contact with ZnO, under the selected sintering conditions (1300°C, 2h). The impedance diagrams reveal a peculiar blocking effect associated with the ZnO grains. Its magnitude is independent of the large variations in conductivity of ZnO, associated with changes in the equilibrium oxygen pressure. Its relaxation frequency markedly depends on this parameter. These peculiar properties are interpreted in terms of a pseudo-capacitive behavior of the electronically conducting ZnO in contact with the YSZ ionic conductor. This contact forms an electrode, the potential of which being determined by the predominant point defect concentration in ZnO.
Probing Redox Kinetics in Pr Doped Ceria Mixed Ionic Electronic Conducting Thin Films by In Situ Optical Absorption Measurements
Authors: Bishop Sean R. , Kim Jae Jin , Thompson Nicholas , Tuller Harry L.
Published: April 2012

In-situ optical absorption measurements are used to derive the kinetics of oxidation and reduction of Pr0.1Ce0.9O2-d in an oxygen partial pressure range from 4 - 50% O2 at 600 oC without potential interference from catalytic metal electrodes. The chemical oxygen surface exchange coefficient is found to obey a power law dependence on pO2 suggesting an adsorption limiting process. The sources of discrepancies with values obtained in previous studies are discussed in terms of the catalytic activity of metal electrodes or changes in film surface chemistry.
Chemical Lift-Off of Blue Light-Emitting Diodes Grown on Sapphire Substrate with an Oxide-Patterned Sacrificial Layer
Authors: Pan Chun-Ting , Shen Kun-Ching , Wuu Dong-Sing , Hsueh Hsu-Hung , Horng Ray-Hua
Published: April 2012

A high quality GaN epilayer was successfully grown on a sapphire substrate with patterned SiO2 as a sacrificial structure utilizing the direct heteroepitaxial lateral overgrowth method. The light-emitting diode (LED) structure was subsequently grown on the GaN epilayer and fabricated using a chemical lift-off process. After SiO2 was removed with a HF solution, the LEDs with Cu substrate could be separated from the sapphire substrate due to an increase in the GaN/sapphire interfacial strain. Similar forward voltage and output power characteristics were obtained for vertical LEDs fabricated using chemical lift-off and laser lift-off processes.
Microstructure Characterization of Nonpolar ZnO and Zn1-xMgxO Epilayers Grown on (100) γ-LiAlO2 by Chemical Vapor Deposition
Authors: Huang Teng Hsing , Lin Wan-Hsien , Wu Jih-Jen , Chou Mitch M.C. , Yan Tao , Chang Liuwen
Published: April 2012

The defects and optical properties of nonpolar (10-10) ZnO and Zn0.9Mg0.1O epilayers grown on (100) gamma-LiAlO2 substrates by CVD were investigated by XRD, TEM and CL. The x-ray rocking curves of the (1-100) reflection for the ZnO and Zn0.9Mg0.1O possessed low FWHM values of 504 and 216 arcsec, respectively. Misfit dislocations in high density exhibited at the epilayer/substrate interface with b=1/3[-12-10] for both samples. Basal stacking faults, threading dislocations and inversion domains were observed in the ZnO with densities on the order of 10-5 cm-2, 10-9 cm-2 and 10-4 cm-1, respectively. On the other hand, only basal stacking faults and threading dislocations were found in the Zn0.9Mg0.1O. The densities of these defects were at least one order of magnitude lower than those of the ZnO one. The Zn0.9Mg0.1O exhibited a near band-edge emission at 3.5 eV whose intensity is about 15 times stronger than that of ZnO at 3.3 eV.
Investigating Degradation Behavior under Hot Carrier Stress in InGaZnO TFT with Symmetric and Asymmetric Structure
Authors: Tsai Ming-Yen , Chang Ting-Chang , Chu Ann-Kuo , Chen Te-Chih , Hsieh Tien-Yu , Che Yu-Te
Published: April 2012

This letter studies the hot-carrier effect in indium-gallium-zinc oxide (IGZO) thin film transistors with symmetric and asymmetric source/drain structures. The different degradation behaviors after hot-carrier stress in symmetric and asymmetric source/drain devices indicate that different mechanisms dominate the degradation. Since the C-V measurement is highly sensitive to the trap state compared with the I-V characterization, C-V curves are utilized to analyze the hot-carrier stress-induced trap state generation. Furthermore, the asymmetric C-V measurements CGD (gate-to-drain capacitance), CGS (gate-to-source capacitance) are useful to analyze the trap state location in the channel. For the asymmetric device structure, the different source/drain structure under hot-carrier stress-induces an asymmetric electrical field and causes different degradation behaviors. In this work, the on-current and subthreshold swing (S.S.) degrade under low electrical field, whereas the apparent Vt shift occurs under a large electrical field. The different degradation behaviors indicate that trap states are generated under low electrical field and the channel-hot-electron (CHE) effect occurs under a large electrical field.
N2O Plasma Treatment Suppressed Temperature-Dependent Point Defects Formation with Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors
Authors: Jhu Jhe-Ciou , Chang Ting-Chang , Chang Geng-Wei , Syu Yong-En , Tsai Tsung-Ming , Jian Fu-Yen , Chang Kuan-Chang , Tai Ya-Hsiang
Published: April 2012

The abnormal sub-threshold leakage current is observed at high temperature in amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors (a-IGZO TFTs). To confirm this phenomenon dependence of the defects of a-IGZO active layer, the paper proposes the devices with N2O plasma treatment at a-IGZO film. This phenomenon only appears in the as-fabricated device, but not in the device with N2O plasma treatment, which is experimentally verified. N2O plasma treatment at a-IGZO TFTs enhances the thin film bonding strength which could suppress the formation of temperature-dependent point defects. The point defects could be generated from oxygen atoms have left their original sites above 400K. The N2O plasma treatment devices have better stability performance than as-fabricated devices. The results suggested that the density of point states for a-IGZO TFTs with N2O plasma treatment is much lower than that as-fabricated. The N2O plasma repairs the point defect to suppress temperature-dependent sub-threshold leakage current.
Drain Leakage Current in Δ-channel SOI nMOSFET Operating at High Temperatures
Authors: Correia Marcello M. , Bellodi Marcello
Published: April 2012

This paper presents the electric behavior of Δ-channel SOI nMOSFET transistors (triangular channel), as a function of the channel geometric dimensions, such as the channel length (L) and the internal angle (θ) of the triangular structure, in the drain leakage current (IDleak) behavior, for these devices operating since room temperature up to 300ºC. Through three-dimensional numeric simulations it was observed that IDleak is composed mainly by electrons, in all analyzed devices operating at high temperatures. Besides that, as L reduces, it was noticed that IDleak increases. However, for smaller angles θ, result smaller IDleak values, when the transistors are operating at same bias and temperature conditions.
The Effect of Oxgen Species on the ZnO TFT Prepared by Atmosphere Pressure Plasma Jet
Authors: Wu Chien-Hung , Chang Kow-Ming , Huang Sung-Hung , Deng I-Chung , Chi Chia-Wei , Wu Chin-Jyi , Chang Chia-Chiang
Published: April 2012

Bottom-gate thin-film transistors (TFTs) were fabricated with ZnO channel layer deposited by atmospheric pressure plasma jet (APPJ). The effect of oxygen partial pressure on the ZnO TFT was investigated. The ZnO thin films were deposited at 100oC, and oxygen gas was incorporated into plasma gas (N2) in the percentage of 0%-1% (O2/N2+O2). Reactive oxygen species could repair the oxygen vacancies during deposition, and the switching behavior was improved effectively. With increasing oxygen partial pressure, the ZnO thin films exhibited a more random orientation. By incorporating 0.69% O2 into plasma gas, a threshold voltage of 26.7 V, a subthreshold swing of 3.89 V/decade, a field-effect mobility of 2.38 cm2/Vs and an Ion/Ioff current ratio of 4.63x109 were obtained.