bluuebunny/crossref_metadata_2025 huggingface dataset:
Fitting forestry models using generalized additive models: a taper model example
Authors: Robinson Andrew P. , Lane Stephen E. , Thérien Guillaume
Published: October 2011

Nonparametric and semiparametric modelling methods are commonly applied in many fields. However, such methods have not been widely adopted in forestry, other than the most similar neighbour and nearest neighbor methods. Generalized additive modelling is a flexible semiparametric regression method that is useful when model-based prediction is the main goal and the parametric form of the model is unknown and possibly complex. Routines to fit generalized additive models (GAMs) are now readily available in much statistical software, making them an attractive option for forest modelling. Here, the use of GAMs is demonstrated by the construction of a taper model for six tree species in British Columbia, Canada. We compare the results with an existing flexible parametric taper model. We assess the performance of the models using the 0.632+ bootstrap method according to five key attributes: whole-stem volume, merchantable volume, number of logs, small-end diameter of the first log, and volume of the first log. The results show that the GAMs and the flexible taper function yielded similar accuracy for all attributes and all species.
Road runoff and sediment sampling for determining road sediment yield at the watershed scale
Authors: Surfleet Christopher G. , Skaugset Arne E. , Meadows Matthew W.
Published: October 2011

In this study, we demonstrate that watershed-scale estimates of road sediment production are improved if field measurements of road runoff and sediment production are used in the analysis. We used several techniques to spatially extrapolate measurements of road runoff and sampled sediment: comprehensive road runoff measurements, runoff estimates derived from the Distributed Hydrology Soil Vegetation Model (DHSVM), and adjustment of the road erosion models WARSEM and SEDMODL2.The sediment yield for the Oak Creek, Oregon, road network based on measured road runoff and sediment was 6.5 tons/year. When DHSVM was used to simulate road runoff, the estimated sediment from roads was similar, 6.9 tons/years. The road sediment production estimated by SEDMODL2 and WARSEM, adjusted with field-measured road runoff and sediment, was 28% and 34% less, respectively, than using the models with the default parameters. When applied to a road network in commercial forest land with frequent road use, the sediment yield estimated by SEDMODL2 and WARSEM without adjustment from field measurements was 480% and 610% higher, respectively, than with adjustments. We found that measuring runoff and sediment from one large storm event (≥1 year recurrence) provided a statistically significant relationship with the annual sediment yield.
Improving tree survival prediction with forecast combination and disaggregation
Authors: Zhang Xiongqing , Lei Yuancai , Cao Quang V. , Chen Xinmei , Liu Xianzhao
Published: October 2011

The tree mortality model plays an important role in simulating stand dynamic processes. Past work has shown that the disaggregation method was successful in improving tree survival prediction. This method was used in this study to forecast tree survival probability of Chinese pine (Pinus tabulaeformis Carrière) in Beijing. Outputs from the tree survival model were adjusted from either the stand-level model prediction or the combined estimator from the forecast combination method. Our results show that the disaggregation approach improved the performance of tree survival models. We also showed that stand-level prediction played a crucial role in refining outputs from a tree survival model, especially when it is a very simple model. Because the forecast combination method produced better stand-level prediction, we prefer the use of this method in conjunction with the disaggregation approach, even though the performance gain in using the forecast combination method shown for this data set was modest.
Ten-year growth and mortality in young Douglas-fir stands experiencing a range in Swiss needle cast severity
Authors: Maguire Douglas A. , Mainwaring Douglas B. , Kanaskie Alan
Published: October 2011

Swiss needle cast, a foliar disease caused by the Ascomycete Phaeocryptopus gaeumannii (T. Rohde) Petr., continues to afflict Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) in north coastal Oregon. Permanent plots were installed in 1998 to assess growth impacts and monitor disease severity. Gross periodic annual increment was measured for three 2-year growth periods and one 4-year growth period and ranged from 0.37 to 31.74 m3·ha–1·year–1. Foliage retention, defined as the average number of annual needle age classes held by a tree, was also estimated as an index of disease severity. Assuming negligible losses in stands with maximum needle retention (approximately 3.9 years), growth losses in net periodic annual increment reached slightly over 50% in stands with the lowest needle retention (approximately 1 year). Mixed-effects regression models supported a consistent relationship between foliage retention and both gross and net periodic annual increment among the four growth periods. Periodic annual mortality ranged from 0 to 19.12 m3·ha–1·year–1 but was not significantly influenced by Swiss needle cast as measured by average foliage retention. Minimum and maximum foliage retention has fluctuated annually from 1998 to 2008 on the permanent plots, but growth losses at a given level of foliage retention appear to have remained stable. Estimated growth losses are similar to those reported for comparable levels of defoliation by other agents.
GENERALIZED HYERS-ULAM STABILITY FOR A GENERAL CUBIC FUNCTIONAL EQUATION IN QUASI-β-NORMED SPACES
Authors: Eskandani G. Z. , Rassias J. M. , Gavruta P.
Published: October 2011

In this paper, we investigate the generalized Hyers-Ulam stability of the following general cubic functional equation [Formula: see text] (k ∈ ℕ, k ≠ 1) in quasi-β-normed spaces and by a counterexample, we will show that this functional equation in a special condition is not stabile.
Low-Resistive Ohmic Contacts for AlGaN Channel High-Electron-Mobility Transistors Using Zr/Al/Mo/Au Metal Stack
Authors: Yafune Norimasa , Hashimoto Shin , Akita Katsushi , Yamamoto Yoshiyuki , Kuzuhara Masaaki
Published: October 2011

An Al
x
Ga1-x
N/Al
y
Ga1-y
N high-electron-mobility transistor (HEMT) with AlGaN as a channel layer has been fabricated on a sapphire substrate for high-output-power and high-frequency electronic applications. One of the key process steps for the AlGaN-channel HEMT is to ensure low resistivity for source/drain ohmic contacts. In this work, the electrical characteristics of Zr/Al/Mo/Au ohmic contacts for AlGaN-channel HEMTs were investigated at annealing temperatures from 850 to 1000 °C. An AlGaN-channel HEMT was fabricated with Al contents of 0.3 and 0.55 for the channel and barrier layer, respectively. A minimum ohmic contact resistivity of 2.6×10-4 Ω cm2 was achieved for the Al0.55Ga0.45N/Al0.3Ga0.7N heterostructure after annealing at 950 °C.
Two-Dimensional Isotope Imaging of Radiation Shielded Materials Using Nuclear Resonance Fluorescence
Authors: Toyokawa Hiroyuki , Ohgaki Hideaki , Hayakawa Takehito , Kii Toshiteru , Shizuma Toshiyuki , Hajima Ryoichi , Kikuzawa Nobuhiro , Masuda Kai , Kitatani Fumito , Harada Hideo
Published: October 2011

A novel method for two-dimensional (2D) imaging of a specific isotope in a material, which is hidden by a thick radiation shield is presented. Nuclear resonance fluorescence and the laser Compton scattering are used in the present method. We measured γ-rays of 5512 keV from the nuclear resonance fluorescence of 208Pb at several points, and obtained a 2D image of isotope distribution.
Optical Trapping of Beads and Jurkat Cells Using Micromachined Fresnel Zone Plate Integrated with Microfluidic Chip
Authors: Kuo Ju-Nan , Hu Han-Zhong
Published: October 2011

This paper presents a method for trapping beads and cells using a single-beam optical tweezer and a Fresnel zone plate integrated with a microfluidic chip. The experimental results show that a laser power of 2.4 mW is sufficient to trap 3-µm-diameter polystyrene beads, while a laser power of 1.5 mW is sufficient to trap individual Jurkat cells. The Fresnel zone plate developed in this study has many advantages, including a small size, a straightforward fabrication process, and a simple integration with microfluidic chips. Consequently, it provides an ideal solution for the trapping of a wide range of biological cells for analysis purposes.
Workshop report from Web2SE 2011
Authors: Treude Christoph , Storey Margaret-Anne , van Deursen Arie , Begel Andrew , Black Sue
Published: October 2011

Web 2.0 technologies, such as wikis, blogs, tags and feeds, have been adopted and adapted by software engineers. With the annual Web2SE workshop, we provide a venue for research on Web 2.0 for software engineering by highlighting state-of-the-art work, identifying current research areas, discussing implications of Web 2.0 on software engineering, and outlining the risks and challenges for researchers. This report highlights the paper and tool presentations, and the discussions among participants at Web2SE 2011 in Honolulu, as well as future directions of the Web2SE workshop community.
SCAG
Authors: Chanda Jayeeta , Sengupta Sabnam , Kanjilal Ananya , Bhattacharya Swapan
Published: October 2011

Service Oriented Architecture (SOA) provides a foundation to achieve software reuse that enables business professionals, who are not necessarily programmers, to exploit the intrinsic properties of software. A component-based programming model is the key factor in the rapid adoption of SOA. SOA exploits the properties of Component Based Software Engineering (CBSE) in the form of services. SOA components help to provide the business users with some flexibility to play around with the components and rewire them to create new business solutions. The complexity of SOA application plays an important role in project planning and determination of timeline and cost estimation and allocation of resources. This paper proposes a metric-based approach for the determination of relative complexity and coupling of Component based SOA application. We have proposed a Service Component Architecture Graph (SCAG) which can be used for graphical representation of the different service module, the service components in the service module and interaction among them. This metrics may be used by developers to assess the complexity of SOA application and if required redesign to create highly cohesive components with minimal coupling. It will also promote a culture of asset (reusable components) based development by considering the factor like usability, complexity, coupling etc. A case study is presented and graph based analysis is done for deriving the complexity, along with the other aspects of the architecture.
A model for versioning control mechanism in component-based systems
Authors: Kaur Parminder , Singh Hardeep
Published: October 2011

Component-based systems provide a better reuse of software components, greater flexibility, scalability and higher quality of services. Component development generally takes place due to the process of creating and propagating changes in requirement definitions, system designs, program source code, documentation and test data. As a result, multiple versions of constituent components come into existence. Thus, there is a need to keep the track of multiple versions of same component. To handle multiple versions of constituent components, a version-control tool named as Visual Version Control Tool (VVCT), for the management of life-cycle evolution of component, is developed. The developed tool satisfies all the conditions required for version control in component-based systems. The parameters required for uniform version management as well as component frameworks are also satisfied by the developed tool. To monitor and control the versioning system, an example model is tested along with the set of proposed metrics. This paper also incorporates issues like component configuration, component evolution, component framework, component version tree and version-control metrics.
An interview with Stewart W. Wilson
Authors: Wilson Stewart W.
Published: October 2011

Stewart W. Wilson is certainly one of the most innovative and functionality-oriented thinkers I have ever had the honor to meet. His research career commenced at the Massachusetts Institute of Technology (MIT), where he received an S.B. degree in physics and an S.M. and PhD degree in electrical engineering. After having completed his formal education, research work at the Polaroid Corporation (starting in 1962) and the Rowland Institute for Science (starting in 1983) led him to the development of practically useful, yet highly complex, biologically-inspired systems and machine learning architectures. In 1998 he founded the research and consultancy company Prediction Dynamics. Since 1999 he has been an adjunct professor at the University of Illinois at Urbana-Champaign, IL.
"Network Neutrality"
Authors: claffy kc
Published: October 2011

In June 2011 I participated on a panel on network neutrality hosted at the June cybersecurity meeting of the DHS/SRI Infosec Technology Transition Council (ITTC), where "experts and leaders from the government, private, financial, IT, venture capitalist,and academia and science sectors came together to address the problem of identity theft and related criminal activity on the Internet." I recently wrote up some of my thoughts on that panel, including what network neutrality has to do with cybersecurity.
Thin Film a-Si/c-Si1-xGex/c-Si Heterojunction Solar Cells: Design and Material Quality Requirements
Authors: Abdul Hadi Sabina , Hashemi Pouya , Nayfeh Ammar , Hoyt Judy
Published: October 2011

a-Si:H/crystalline-Si1-xGex/c-Si heterojunction solar cells (HIT cells) are simulated and fabricated for the first time. Cells with junction layers consisting of Si, Si0.75Ge0.25, and Si0.59Ge0.41 are compared to study the effect of increasing Ge concentration. The results show a Voc drop from 0.6V for Si cells to 0.4V forSi0.59Ge0.41, consistent with the reduction in bandgap. The measured Jsc increases from ~18.5 mA/cm2 for Si cells to 20.3 mA/cm2 for theSi0.59Ge0.41 cells,for one light pass. Simulations suggest that the measured Jscfor the Si0.59Ge0.41 based solar cells is limited by a low lifetime. In order for Si1-xGexbased cells to exceed the efficiency of Si, simulations indicate that Ge percentages larger than 40% and lifetimes above 1 μs are required.
Role of the Back Metal-Semiconductor Contact on the Performances of a-Si:H Solar Cells
Authors: Foti Marina , Cannella Giuseppe , Gerardi Cosimo , Di Marco Silvestra , Ravesi Sebastiano , Sparta Noemi , Lo Verso Stella , Principato F. , Coffa Salvatore , Lombardo Salvatore
Published: October 2011

We have investigated the role of the metal-semiconductor back contact on the performances of thin film modules consisting of single junction a-Si:H photovoltaic (PV) cells deposited with p-i-n configuration. We find that an adequate choice of the back contact helps reducing the barrier height of the junction improving the contact conductivity. For this purpose Mo has shown to be effective. Moreover we find that Mo, as refractory material, has additional beneficial effects reducing the formation of defects leading to the decrease of recombination losses. We have then fabricated a PV module on flexible substrate for indoor energy harvesting applications using Mo as back contact. An efficiency of 6% is obtained at 300 lux under F12 spectrum illumination.
Novel Organic Solar Cell Based on Polyaniline - Carbon Nanotubes Composite
Authors: Ebrahim Shaker , Abdel-Fattah Tarek M. , Soliman Moataz , Hafez Mostafa
Published: October 2011

In this work a fabrication of a novel design of organic solar cell using polyaniline base (EB), multi-walled carbon nanotubes (MWCNTs), organic dye (rhodamine B or riboflavin), zinc oxide (ZnO) and indium-tin oxide (ITO) was succeeded. The highest short current density, open circuit voltage and efficiency were found to ITO/EB-MWCNTs/ZnO-rhodamine B/ITO structure and equal to 0.224 mA/cm2, 0.4 V and 0.3 respectively.
Electrodeposition of Ni3S2 for Photovoltaic Applications: Colloidal Sulfur Stabilization by Gelatin
Authors: Pac Munteha , Han Xiaofei , Tao Meng
Published: October 2011

Electrochemical deposition of Ni3S2 for photovoltaic applications: colloidal sulfur stabilization by gelatin Munteha Pac , Xiaofei Han and Meng Tao a Department of Materials Science and Engineering and b Department of Electrical Engineering, University of Texas at Arlington, Arlington, Texas 76019, USA Electrodeposition of Ni3S2 with significantly improved uniformity and adhesion to F-doped SnO2 substrate is reported. Ni3S2 films of about 1 μm thickness were deposited from an aqueous solution containing NiSO4, Na2S2O3 and gelatin. Gelatin is found to stabilize the size of colloidal sulfur to ~260 nm, keeping the electroactive sulfur concentration stable during the deposition. Other deposition parameters such as NiSO4 concentration, bath temperature and deposition potential are found to have a profound effect on film morphology and adhesion. Ni3S2 films with a uniform composition across the entire substrate can be deposited from a solution containing 0.013M NiSO4, 0.5M Na2S2O3, 8.8×10-4 wt% gelatin at 60°C temperature, pH 4.7 and -0.4V deposition potential.
Investigation of Electrically Active Defects in n-CdS/p-CdTe Solar Cells
Authors: Kharangarh Poonam R. , Misra Durga , Georgiou George , Chin Ken
Published: October 2011

Current-voltage (J-V) and Capacitance-voltage (C-V) measurements of diode devices at different temperatures and illumination intensities are used to provide valuable information about non-idealities in the pn semiconductor junction and metal-semiconductor junction. In principle, continuous monitoring of this information can be used to improve diode and solar cell performance. In this paper we characterize the n+p CdTe on CdS solar cell. The activation energy derived from the temperature dependence of our solar cell J-V curves is consistent with trap assisted tunneling being the dominant carrier transport mechanism in the pn junction. Interpretation is complicated in the particular case of thin-film CdTe, by multiple non-shallow (not fully ionized) "doping" energy levels in the CdTe band gap are in reality, which are not distinct from "trap" energy levels. We use C-V profiling to further understand the concentrations of recombination centers as well as the interplay of the double acceptor Cd vacancy and the non- shallow acceptor Cu substitute of Cd.
Electric Field Driven Degradation of AlGaN/GaN High Electron Mobility Transistors during Off-State Stress
Authors: Chang C. Y. , Douglas Erica , Kim Jinhyung , Liu Lu , Lo Chien-Fong , Chu Byung-Hwan , Cheney D. J. , Gila Brent P. , Ren F. , Via G. D. , Cullen David A. , Zhou Lin , Smith David J. , Jang Soohwan , Pearton S. J.
Published: October 2011

The critical degradation voltage of AlGaN/GaN High Electron Mobility Transistors with Ni/Au gate during off-state electrical stress was studied. Devices with different gate length and gate-drain distances were found to exhibit the onset of degradation at different source-drain biases but similar electric field strengths, showing that the degradation mechanism is primarily field-driven. The calculated degradation field was ~1.8MV/cm by ATLAS simulations. Transmission Electron Microscopy imaging showed creation of defects under the gate after DC stress.
Electrical Performance of Chlorine-Treated AlGaN MOS Diodes with i-ZnO Insulator
Authors: Chiou Ya-Lan , Lee Ching-Ting , Lee Hsin-Ying , Chang Kuo-Jen , Lin Jia-Ching , Chuang Hao-Wei
Published: October 2011

The intrinsic zinc oxide (i-ZnO) film deposited by a vapor cooling condensation system was used as the gate dielectric layer of the AlGaN metal-oxide-semiconductor (MOS) diodes. The chlorine surface treatment of AlGaN was utilized to reduce the surface states resided on the AlGaN surface. Comparing with the untreated AlGaN MOS diodes, the chlorine-treated AlGaN MOS diodes revealed a lower leakage current and a lower interface states density. The experimental results indicated that the chlorine surface treatment could effectively improve the quality of the i-ZnO/AlGaN interface and the electrical performance of the AlGaN MOS diodes with i-ZnO insulator layer.
Evaluation of the High Temperatures Influence on High Frequency C-V Curves of MOS Capacitor
Authors: Borges Ziliotto Ana Paula , Bellodi Marcello
Published: October 2011

It is presented numerical bi-dimensional simulations results concerning the high frequency capacitance versus voltage (C-V) characteristic of the MOS capacitor operating from room temperature up to 573K using AC analysis. The results show that the C-V curves behavior is influenced by substrate doping concentration, substrate and gate materials. Also, it is presented experimental results concerning to the high frequency C-V characteristic of a sample MOS capacitor, confirming the results obtained through simulations.
Enhanced Photoelectrochemical Properties of CdS/ZnO Supported on Carbon Nanotube Films
Authors: Dong Lifeng , Malone John , Yu Liyan , Dong Hongzhou , Yu Jianhua
Published: October 2011

We report here a facile vacuum filtration method to fabricate CdS and CdS-ZnO particles wrapped with carbon nanotubes on conductive glass substrates. The net-like nanotube structures facilitate carrier transport and greatly improve photon-response characteristics of CdS and CdS-ZnO particles. The enhancement is related to the structural characteristics of the nanotubes and the configuration of CdS and ZnO particles. For instance, single-walled carbon nanotube-based ZnO-CdS structures have higher photo-response currents than CdS-ZnO structures, whereas, multi-walled carbon nanotube-based CdS-ZnO structures have better photo-response characteristics than ZnO-CdS structures.
Adding New Capabilities to Silicon CMOS Integrated Circuits via Deterministic Assembly
Authors: Kim Jaekyun , Morrow Thomas , Lin Lan , Keating Christine , Mayer Jeffrey , Mayer Theresa S.
Published: October 2011

Electric-field-assisted deterministic assembly is used to position individual nanowires in high density arrays on silicon integrated circuits. Forces induced on the solution-suspended nanowires by a spatially varying, nonuniform electric field determines the position of each wire with respect to lithographic features on the circuit. Two electrode structures used to create the spatial variations in field strength are compared experimentally and theoretically. This technique is applied to fabricate bioprobe-coated nanowire resonator device arrays for chip-based sensing applications.
Hydrogen Detection Using Chemical Vapor Deposited Graphene Coated with Platinum
Authors: Chu Byung-Hwan , Nicolosi Justin , Lo Chien-Fong , Strupinski Wlodek , Pearton S. J. , Ren F.
Published: October 2011

The effect of Pt metal thickness on the hydrogen sensing sensitivity of Pt-coated, multi-layered graphene grown by chemical vapor deposition on Si-polar 4H-SiC, was investigated. As-grown graphene samples and graphene samples coated with 1nm or 4nm thick Pt films were used in this study. Compared to graphene without platinum, significantly improved hydrogen detection sensitivity was observed with the addition of platinum films. The highest hydrogen sensitivity was observed with the graphene sensor with 1nm platinum coating. The platinum coated graphene sensor also showed good selectivity for hydrogen detection over methane, ammonia, oxygen, and nitrogen oxide.
The Impact of Active Layer Pre-Treatment on Bias Stress Stability of Sol-Gel Derived Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistor
Authors: Chung Wan-Fang , Chang Ting-Chang , Li Hung-Wei , Chen Yu-Chun , Li Iue-Hen , Tseng Tseung-Yuen , Tai Ya-Hsiang
Published: October 2011

We have investigated the gate bias stress-induced instability on the electrical properties with different pre-treatments for sol-gel derived amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs). The device with illuminating and heating pre-treatments under the positive/negative gate bias stress in vacuum had the smallest threshold voltage shift as the stress duration increased, while the device with oxygen gas pre-treatment exhibited an obvious variation. These electrical instabilities were ascribed to the charge trapping in the gate insulator and the oxygen/water adsorption on the active layer. It indicates that the specific pre-treatment for the a-IGZO film can improve the device stability. It also provides the important information for the subsequent passivation process concerning the pre-treatment of the active layer.
Determining the Fundamental Kinetic Parameters for Rinsing and Cleaning of Hafnium-Based High-k Materials
Authors: Zamani Davoud , Keswani Manish , Yan Jun , Raghavan Srini , Shadman Farhang
Published: October 2011

The interactions of HF with hafnium oxide are important during post-etch cleaning of high-k dielectrics. The dynamics of these interactions during the rinse process are studied using a quartz crystal microbalance (QCM) equipped with a flow-through cell. A process model is developed showing that the overall process consists of three simultaneous process steps: adsorption, desorption and etching involving fluoride species. The model was validated using the experimental data obtained in QCM. The key parameters of these process steps namely adsorption, desorption and etch rate coefficients were determined using the combined experimental measurement and process modeling.
Cleaning Challenges of EUV Mask Substrates, Blanks, and Patterned Mask
Authors: Rastegar Abbas , House Matthew , John Kadaksham Arun
Published: October 2011

SEMATECH has been a pioneer in EUV mask substrate and blank cleaning since early 2003. Nevertheless, EUV mask blank defectivity remains one of the main challenges in realizing EUV lithography. EUV masks have their own cleaning challenges that are partly related to introducing new materials and partly related to cleaning-induced EUV reflectivity changes in the multilayer structure. Removal of sub-20 nm particles from the surface of EUV mask substrates without leaving pits is a major challenge along with maintaining Ru cap durability over multiple cleanings and removing sub-20 nm particles from the inside of contact holes and trenches. The goal of this paper is to introduce challenging problems in EUV mask cleaning to researchers and technologists whose research can accelerate the mitigation of EUV mask defects.
Wet Cleaning and Surface Preparation for Ge
Authors: Takahashi Hiroaki , Wada Masayuki , Snow Jim , Vos Rita , Mertens Paul W. , Shirakawa Hajime , Nadahara Soichi
Published: October 2011

In the process flow with Ge material, several wet cleaning steps are considered as post Ge channel deposition, post gate etch and post spacer etch. For these cleanings, not only high PRE (Particle Removal Efficiency) but also the control of Ge loss is required. We confirmed the characteristic of PRE on the Ge surface and Ge loss with conventional chemistries. Particles can be removed by the lift-off phenomena using ozonated water but a large amount (> 3nm) of Ge loss were required to obtain sufficient PRE. Applying diluted APM for high pH oxidation chemistry can minimize Ge loss while keeping effective particle removal. However since evaluated APM (1:1:20,000) still etches Ge layer first, it might have an issue of the concentration controllability and reproducibility. In this paper, we demonstrated a novel chemistry alternative to highly diluted APM that has proven significant competitive advantages.
(Invited) GaN-on-Si For High-Voltage Applications
Authors: Visalli Domenica , Van Hove Marleen , Srivastava Puneet , Marcon Denis , Geens Karen , Kang Xuanwu , Vandenplas Erwin , Viaene John , Leys Maarten , Cheng Kai , Sijmus Bram , Decoutere Stefaan , Borghs Gustaaf
Published: October 2011

This work provides an overview of our GaN-on-Si activity for high voltage applications. We will discuss the failure mechanisms of GaN-on-Si devices by electrical characterization and TCAD simulations. The main issues of the use of the Si as substrate are identified and addressed. A breakdown voltage as high as 1050 V and a specific on-resistance as low as 2 mOhm⋅cm2 have been achieved.
Evaluation of Properties of SiO2 Films Fabricated by Plasma Oxidation
Authors: Yamaguchi Takuya , Nagata Kohki , Ogura Atsushi , Koganezawa Tomoyuki , Hirosawa Ichiro , Kabe Yoshiro , Sato Yoshihiro , Ishizuka Shuuichi , Hirota Yoshihiro
Published: October 2011

Properties of SiO2 films formed by plasma oxidation were compared with those of films formed by thermal oxidation. X-ray reflectivity (XRR) was used to evaluate the SiO2/Si interface roughness, thickness, and density of SiO2 films. Chemical properties of the SiO2 films were investigated by X-ray photoelectron spectroscopy (XPS). Moreover, the relation between film density and its chemical properties was evaluated. This evaluation shows that SiO2 films fabricated by plasma oxidation have higher density and a smoother interface than those fabricated by thermal oxidation. In addition, oxidation rate was increased and interface quality and density were improved by incorporating hydrogen in the plasma atmosphere.
(Invited) Voltage Ramp Stress Based Stress-And-Sense Test Method For Reliability Characterization of Hf-Base High-k/Metal Gate Stacks For CMOS Technologies
Authors: Cartier Eduard , Kerber Adreas , Krishnan Siddarth , Linder Barry , Ando Takashi , Frank Martin M. , Choi Kisik , Narayanan Vijay
Published: October 2011

Traditionally, the reliability of gate oxides is mostly evaluated using a Constant Voltage Stress, CVS, based stress-and-sense methodology, in which a constant stress voltage is interrupted to quantify the degradation. In this paper, we discuss the use of a Voltage-Ramp Stress, VRS, based stress-and-sense method in which the stress voltage is ramped at a constant rate and degradation is quantified by interrupting the VRS at increasingly higher stress voltages. The two methods are used and compared for dielectric breakdown and bias temperature instability measurements using high-k/metal gate stacks. It is shown that the two methods can be used interchangeably, producing very similar reliability assessments. It is shown that the VRS method, however, has distinct advantages over a CVS approach. It is fast and 'foolproof', providing reliable information on the voltage acceleration without any prior knowledge on the dynamics of the degradation. The use of a VRS is therefore well suited for monitoring reliability parameters during gate stack and process development, and during device optimization, where large variations in the reliability parameters are common.
Electron Irradiation Effects on Atomic Layer Deposited High-k Gate Dielectrics
Authors: García Hector , Castán Helena , Dueñas Salvador , Bailón Luis , Campabadal Francesca , Rafi Joan Marc , Zabala Miguel , Beldarrain Oihane , Ohyama Hidenori , Takakura Kenichirou , Tsunoda Isao
Published: October 2011

Electron radiation effects on the electrical properties of Al2O3 and HfO2-based MIS capacitors have been studied. High-k dielectrics were grown by atomic layer deposition, and capacitors were exposed to three different electron radiation doses. Capacitance-voltage, deep-level transient spectroscopy, conductance transients, flat-band voltage transients and current-voltage techniques were used to characterize the samples. In all cases, positive charge is trapped in the dielectrics after irradiation. Insulator/semiconductor interface quality can be improved for low irradiation doses. However, for high doses interface quality worsens. Irradiation always degrades the dielectric layers in terms of gate leakage current.
A Drain Current - Drain Voltage Relation for MOSFETs with High-k Gate Stacks
Authors: Kar S.
Published: October 2011

New analytical MOSFET drain-current-drain-voltage relations have been derived incorporating effects of gate stack traps and charges, semiconductor-metal work function difference, and non-saturating surface potential, employing a novel approach of treating these complicating factors. These analytical drain current, transconductance, and channel conductance versus drain voltage relations in closed form provide a comprehensive and clear physical picture and show directly how the gate stack traps and charges, the non-saturating surface potential, and the semiconductor-metal work function difference affect and significantly degrade the drain current, the transconductance, and the channel conductance.
Electrical Characteristics of GaN and Si Based Metal-Oxide-Semiconductor (MOS) Capacitors
Authors: Hossain Tashfin Z. , Wei Daming , Edgar James H.
Published: October 2011

We report on the electrical properties of Al2O3 and TiO2 dielectrics in three different MOS capacitors of Al2O3/n-Si, TiO2/n-Si, and Al2O3/n-GaN. Hysteresis analysis of capacitance-voltage data and shifts in flat band voltages showed that the interface electrical quality of TiO2/Si was superior compared to that of Al2O3/Si and Al2O3/GaN. The growth temperature during atomic layer deposition were varied and Al2O3 deposited at 300°C on GaN and TiO2 deposited at 200°C on Si had better electrical property. The dielectric constant of the unannealed TiO2 was low and only the brookite crystalline phase of TiO2 was detected by XRD. The variation in the capacitance on some MOS capacitors was related to nonuniformities of the TiO2 oxide surface, as found from AFM images. The leakage current densities were low, as obtained from current-voltage measurement of Al2O3 and TiO2 gate oxide.
(Invited) Efficient Guiding Principle of Highly Scalable MONOS-Type Memories
Authors: Kamiya Katsumasa , Yamaguchi Keita , Otake Akira , Shigeta Yasuteru , Shiraishi Kenji
Published: October 2011

We study the atomistic behavior of O-related defects in metal-oxide-nitride-oxide-semiconductor (MONOS) type memories using first-principles calculations. We find that the O-related defects in SiN charge trap layers result in the local collapse of the layer, leading to serious memory degradation. Based on these results, we propose an efficient guiding principle for the fabrication of highly scalable MONOS-type memories; the interfacial O chemical potential should be controlled to prevent the formation of the O-related defects in the SiN layer. The realistic and skillful recipe along the guidelines is the insertion of a thin Si layer into the SiO2 layer near SiO2/SiN interface. This recipe is also applicable for future nano-scale devices, where the fabrication of sharp and high quality oxide interfaces is crucial.
(Invited) In Situ Transmission Electron Microscopy Analysis of Conductive Filament in Resistance Random Access Memories
Authors: Takahashi Yasuo , Fujii Takashi , Arita Masashi , Fujiwara Ichiro
Published: October 2011

In-situ transmission electron microscopy (TEM) analysis of resistance random access memories (ReRAMs) is reported. While ReRAMs have high potentiality as universal memories, there is a big critical issue for making them practicable. It is the obscurity of operation mechanisms. In this report, two typical ReRAM materials, NiO and Cu-GeS, are investigated. It is widely believed that the NiO shows monopolar resistive switching caused by the formation and the breakdown of conducting filaments. On the other hand, a solid electrolyte Cu-GeS shows bipolar switching, where the metallic filament is thought to be formed and dissolved in the material. In order to clarify the operation mechanisms of these ReRAM materials, we employed in-situ TEM direct observation of resistance switching, and succeeded to detect the filament formation for both materials. In addition, the real-time disappearance of the filament in Cu-GeS was clearly recognized in corresponding to the resistance switching.
Electrical Properties of Rare-Earth Oxides and La2O3 Stacked Gate Dielectrics
Authors: Kouda Miyuki , Kakushima Kuniyuki , Ahmet Parhat , Tsutsui Kazuo , Nishiyama Akira , Sugii Nobuyuki , Natori Kenji , Hattori Takeo , Iwai Hiroshi
Published: October 2011

The electrical properties of La2O3 gate dielectric stacked with other rare-earth oxides were investigated. A reduction of fixed charged defects in the dielectric film was observed in CeOx/ La2O3/NdOx compared to that of La2O3/NdOx. Obtained equivalent oxide thickness (EOT) was smaller for CeOx/ La2O3/NdOx gate stack compare to that of CeOx/ La2O3 gate stack while the estimated fixed charged defects in the dielectric film were almost same. An EOT of 0.45 nm was achieved by using Nd-oxide as a capping layer. Our results show that combination of several rare-earth oxides is useful in improving electrical properties of high-k gate stacks.
Influence of Flash Lamp Annealing on Electrical Characteristics of MOS Device with Si/La2O3/n-Si Structure
Authors: Kaneda Tasuku , Kouda Miyuki , Kakushima Kuniyuki , Ahmet Parhat , Tsutsui Kazuo , Nishiyama Akira , Sugii Nobuyuki , Natori Kenji , Hattori Takeo , Iwai Hiroshi
Published: October 2011

The influence of flash lamp Annealing (FLA) on Si/La2O3/n-Si structure and electrical characteristics of MOS devices have been studied.
(Invited) Device and Integration Technologies of III-V/Ge Channel CMOS
Authors: Takagi Shinichi , Yokoyama Masafumi , Kim Sang-Hyeon , Zhang Rui , Takenaka Mitsuru
Published: October 2011

One of the ultimate CMOS structures can be the combination of III-V nMOSFETs and Ge pMOSFETs. In this presentation, we focus on the possible solutions for realizing CMOS integration of III-V and Ge MOSFETs. In order to realize the integration of III-V/Ge MOSFETs, the direct wafer bonding is a promising way. The gate stack formation is also a critical issue for III-V/Ge CMOS integration. We have employed Al2O3 gate insulators for both InGaAs and Ge MOSFETs. We have recently realized Al2O3/GeOx/Ge MOS gate stacks with low Dit and thin EOT by employing ALD Al2O3 and successive plasma oxidation. We consider that metal S/D scheme can be the best solution for III-V/Ge CMOS. We have implemented Ni-based metal S/D technologies for InGaAs and Ge MOSFETs. By employing these technologies, we have demonstrated successful integration of InGaAs-OI nMOSFETs and Ge p-MOSFETs on a same wafer and their superior device performance.
The Annealing Kinetic Study on Germanium Surface Blistering by Hydrogen Implantation
Authors: Yang Fan , Zhang Xuan Xiong , Ye Tian Chun , Zhuang Song Lin
Published: October 2011

The annealing blistering after hydrogen implantation is a fundamental to achieve GeOI (germanium-on-insulator) by the well-known Smart-cut process. The impacts of H implantation dose and energy on the annealing kinetic plots are studied. The experimental results indicated: (1) the implantation with low dose or energy results in Arrhenius plot with a break point that separate the plot into two regions due to different activation energy; (2) the situation of the kinked kinetic plot, high and low temperature corresponding to high and low activation energy, is against that for other known materials; (3) the unitary activation energy occurs as either implantation dose or energy is enhanced. Moreover, the critical size to form craters increases with the rise of either dose or energy in H-implanted Ge. The variation of the kinetic plot may be related to the different desorption energy from the diverse types of H-platelets with distinct bind energy in germanium.
Moisture Uptake Impact on Damage Layer of Porous Low-k Film in 80nm-Pitched Cu Interconnects
Authors: Tagami Masayoshi , Ogino Atsushi , Miyajima Hideshi , Shobha Hosadurga , Baumann Frieder H. , Ito Fuminori , Spooner Terry
Published: October 2011

Impacts of the moisture uptake into the damage layer of porous SiOCH low-k film on line capacitance and leakage current were investigated in the 80nm-pitch triple layer interconnect structure. The damage layer thickness was controlled from zero to 8nm by the RIE, wet process and Cu surface treatment. The damage layer thickness is defined by TEM-EELS analysis. The line capacitance and leakage current were increased by moisture uptake. The dielectric constant of damage layer including moisture was estimated 7.6 by the capacitance simulation. The moisture control of the damage layer in porous SiOCH low-k film is very important to reduce the line capacitance and improve the line leakage current as well as damage layer elimination.
Low Equivalent Oxide Thickness TiO2 Based Capacitors for DRAM Application
Authors: Fröhlich Karol , Hudec Boris , Hušeková Kristina , Aarik Jaan , Tarre A. , Kasikov Aarne , Rammula Raul , Vincze Andrej
Published: October 2011

Properties of TiO2 based DRAM capacitors with equivalent oxide thickness of 0.5 nm are described. It is shown, that dielectric constant values more than 100 can be obtained in these structures for the TiO2 films with the thickness down to 10 nm. Leakage current density below 10-7 A/cm2 at 0.8 V can be obtained after post-deposition processing for the films with the thickness of 16 nm (EOT ≈ 0.5 nm). Al doping of the TiO2 films decreases dielectric constant, but improves leakage current density. Al-doped TiO2 films with the thickness of 10 nm (EOT = 0.46 nm) exhibit leakage current density below 10-7 A/cm at 0.8 V.
ALD Applied to Conformal Coating of Nanoporous γ-Alumina: Spinel Formation and Luminescence Induced by Europium Doping
Authors: Rauwel Erwan , Nilsen Ola , Galeckas Augustinas , Walmsley John , Rytter Erling , Fjellvaåg Helmer
Published: October 2011

We report on conversion of nanoporous γ-alumina particles into the spinel type ZnAl2O4 without deteriorating porosity of the host material notably. The material was converted by depositing thin layers of ZnO by the atomic layer deposition (ALD) technique and annealing the sample at 800°C to facilitate a solid state reaction for formation of the spinel phase. Such particles represent robust and inert structures most suitable as host materials for catalysis and other processes where large surface area is desired. These samples were used as host materials for a red-emitting phosphor by depositing a thin layer of europium on the surface of the particles, also by the ALD technique. The europium coating was limited to the particle surface due to reaction kinetics, however a strong luminescence at 620 nm was observed. The synthesis and characterization of all these structures will be described.
(Invited) Atomic Layer Deposition of Superconductors
Authors: Proslier Thomas , Klug J. , Becker Nicholas C. , Elam Jeffrey W. , Pellin Michael
Published: October 2011

We report the use of atomic layer deposition (ALD) to synthesize thin superconducting films and multilayer superconductor-insulator (S-I) hetero-structures. ALD being applied to superconducting films opens the way for a variety of applications, including improving the performance and decreasing the cost of high energy particle accelerators, superconducting wires for energy storage, and bolometers for radiation detection. Furthermore, the atomic-scale thickness control afforded by ALD enables the study of superconductivity and associated phenomena in homogeneous layers in the ultra-thin film limit. Two-dimensional superconductivity in such films is of interest from a fundamental point of view, as a new effect has recently been discovered at ultra-low temperature in thin superconducting films made by ALD: the super-insulating transition. The discovery of a new state with apparently infinite resistivity in ultra-thin ALD films offers both a platform to explore new physics as well as the promise, on a longer term, of new opportunities for loss electronics and detectors.
Study of Atomic Layer Deposition of ZnO on a Polar Oxide Substrate by In Situ Quartz Crystal Microbalance
Authors: Pradhan Kallol , Lyman Paul F.
Published: October 2011

ZnO thin films were grown using the atomic layer deposition (ALD) technique with diethyl zinc (DEZ) and deionized water as precursors. A viscous-flow atomic layer deposition reactor has been designed and constructed for the ZnO growth. An in-situ quartz crystal microbalance (QCM) has been interfaced with the reactor to monitor the ALD film growth. Using this ALD reactor we have grown ZnO films on oxidized Si(001) and on MgO(111) polar oxide substrates. QCM was used to monitor the film growth rate as function of precursor pulse time and temperature. In the ALD temperature window (130 to 170oC), the growth rate was found to be about 2.3 Aå/cycle. Ex-situ atomic force microscope (AFM) studies on ZnO thin films reveal surface roughness increases with number of ALD cycles.
(Invited) Molecular Layer Deposition of Flexible, Transparent and Conductive Hybrid Organic-Inorganic Thin Films
Authors: Yoon Byunghoon , Lee Byoung Hoon , George Steven M.
Published: October 2011

Hybrid organic-inorganic thin film alloys were fabricated by molecular layer deposition (MLD) and atomic layer deposition (ALD) methods using diethyl zinc (DEZ), hydroquinone (HQ), and water (H2O). Sequential exposures of DEZ & HQ for zincone MLD and DEZ & H2O for ZnO ALD led to the linear growth of zincone alloy films. The alloy film composition could be varied by changing the number of MLD cycles and ALD cycles per reactant sequence. The alloy films were found to be highly conductive. Zincone alloys grown with MLD:ALD cycle ratios of 1:1 and 2:2 displayed sheet resistivities in the 10-3Ω cm range. These sheet resistivities were substantially lower than the sheet resistivity for ZnO ALD films. These alloys films may be useful as flexible, transparent and conducting coatings.
(Invited) Atomic Layer Deposition for Novel Dye-Sensitized Solar Cells
Authors: Tétreault Nicolas , Heiniger L-P. , Stefik M , Labouchère P. L. , Arsenault Éric , Nazeeruddin N. K. , Ozin G A. , Grätzel M.
Published: October 2011

Herein we present the latest fabrication and characterization techniques for atomic layer deposition of Al2O3, ZnO, SnO2, Nb2O5, HfO2, Ga2O3 and TiO2 for research on dye-sensitized solar cell. In particular, we review the fabrication of state-of-the-art 3D host-passivation-guest photoanodes and ZnO nanowires as well as characterize the deposited thin films using spectroscopic ellipsometry, X-ray diffraction, Hall effect, J-V curves and electrochemical impedance spectroscopy.
(Invited) Atomic Layer Deposited Yttria Stabilized Zirconia Barrier Layer for Proton Conducting Oxide
Authors: Park Joong Sun , Kang Sangkyun , Gür Turgut M. , Prinz Fritz
Published: October 2011

This paper describes the evidence of proton transport in atomic layer deposited yttria-stabilized zirconia (YSZ) and its application as chemical barrier layer for proton conduction oxides that are vulnerable to carbon dioxide attack. Secondary ion mass spectrometry measurement in atomic layer deposited YSZ showed that atomic layer deposited YSZ contains two orders of magnitude higher deuterium concentration than the pulsed laser deposited YSZ, which may be attributed to innate properties of atomic layer deposition processes. We also demonstrated proton conducting oxide fuel cells employing atomic layer deposited YSZ as a protection layer, which can mitigate a formation of carbonate layer, which blocks proton incorporation and transport.
PEMFC MEA and System Design Considerations
Authors: Knights Shanna , Bashyam Rajesh , He Ping , Lauritzen Michael , Startek Cara , Colbow Vesna , Cheng Tommy , Kolodziej Joanna , Wessel Silvia
Published: October 2011

Proton exchange membrane fuel cells (PEMFCs) are being developed and sold commercially for multiple near term markets. Ballard Power Systems is focused on the near term markets of backup power, distributed generation, materials handling, and buses. Significant advances have been made in cost and durability of fuel cell products. Improved tolerance to a wide range of system operation and environmental noises will enable increased viability across a broad range of applications. In order to apply the most effective membrane electrode assembly (MEA) design for each market, the system requirements and associated MEA failures must be well understood. The failure modes associated with the electrodes and membrane degradation are discussed with respect to associated system operation and mitigating approaches. A few key system considerations that influence MEA design include expected fuel quality, balance-of-plant materials, time under idle or open circuit operation, and start-up and shut-down conditions.