bluuebunny/crossref_metadata_2025 huggingface dataset:
Ordered and Parallel Niobium Oxide Nano-Tubes Fabricated using Atomic Layer Deposition in Anodic Alumina Templates
Authors: Rooth Mårten , Johansson Anders , Boman Mats , Hårsta Anders
Published: April 2011

Amorphous niobium oxide (Nb2O5) nano-tubes were fabricated inside anodic alumina templates using atomic layer deposition (ALD). The nanoporous templates were in-house fabricated anodic alumina membranes having an inter-pore distance of about 100 nm with pores lengths of 2 µm. The pores were parallel and well ordered in a hexagonal pattern. Atomic layer deposition was performed using gas pulses of niobium iodide (NbI5) and oxygen separated by purging pulses of argon. By employing long gas pulses (30 s) it was possible to get coherent and amorphous Nb2O5 films conformally covering the pore-walls of the alumina template. The outer diameter of the nano-tubes was tailored between 40 and 80 nm by using alumina templates with different pore sizes. By using template membranes with pores not opened in the bottom, nano-tubes with one side closed could be fabricated. Free-standing, and still parallel, nano-tubes could be obtained by selectively etching away the alumina template using phosphoric acid. Using the above mentioned procedure it was possible to fabricate unsurpassed parallel niobium oxide nano-tubes of equal length, diameter and wall-thickness, ordered in a perfect hexagonal pattern. The samples were analysed using high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), electron diffraction and x-ray fluorescence spectroscopy (XRFS).
The Self-Assembling “Grow-in-Place” Process: An Environmentally Friendly Approach to Nanowire Device Fabrication
Authors: Shan Yinghui , Kalkan Ali Kaan , Fonash Stephen J.
Published: April 2011

Silicon nanowires (SiNWs) were fabricated directly from the Si source gas into pre-fabricated permanent nanochannel templates by our self-assembling “grow-in-place” approach. The size, shape, position, orientation, and number of the SiNWs can be precisely controlled by the pre-fabricated nanochannel templates. Our approach is environmentally benign and friendly since only the exact number of SiNWs needed was grown and the SiNWs were always confined in the nanochannel templates. In addition, the templates can be fabricated with built-in contacts and integrated into the final devices, providing contacts, interconnects, and passivation/encapsulation. We are developing a variety of built-in ohmic and rectifying contact structures and approaches for the “grow-in-place” methodology. Some initial results will be discussed here.
Size- and Surface-dependent Photoresistance in SnO2 Nanowires
Authors: Mathur Sanjay , Barth Sven , Pyun Jae-Chul , Shen Hao
Published: April 2011

Nanostructured one-dimensional materials, such as nanowires, tubes and rods, are gaining increasing attention due to interesting properties and confinement effects, however controlled synthesis of these structures is still limited to a few methods. We present here the synthesis of SnO2 nanowires (Ø, 50 – 1000 nm) at moderate temperatures (550 – 900 °C) using a molecular source [Sn(OBut)4] with pre-existent Sn-O bonds. The growth occurs via a catalyst driven vapor-solid-solid mechanism. Size-selective synthesis of NWs in high areal density was achieved by choosing Au particles of appropriate size. HR-TEM analysis reveals the single crystalline behaviour of wires with a preferred growth direction [100]. Use of SnO2 nanowires as potential optical switches for UV applications was demonstrated by the photo-response measurements. Determination of band gap values confirmed the blue-shift of the main photo-response peak with shrinking radial dimensions of the wires. Furthermore, deposition of vanadium oxide onto SnO2 led to a red-shift of the main conduction value of the nanowires.
PbS Nanocrystal “Plasma-Polymerization”
Authors: Cademartiri Ludovico , von Freymann Georg , Arsenault Andre C. , Bertolotti Jacopo , Wiersma Diederik S. , Kitaev Vladimir , Ozin Geoffrey A.
Published: April 2011

We here demonstrate the use of semiconductor chalcogenide nanocrystals as single-source precursors for the one-step formation of flexible functional films. By taking advantage of the surface chemistry of these “zero-dimensional” building blocks we obtain close-packed three-dimensional arrays of nanocrystals interconnected by oxide sheaths. The films are obtained by exposing oxidation-resistant nanocrystals to an air plasma treatment. This treatment does not significantly influence the photoluminescence efficiency of the individual nanocrystal building blocks but confers them resilience to bending as well as resistance to acidic environments, hot solvents, annealing, and UV irradiation.
Directed Self-Assembly of Multilayer Thin Films of ZnS and Gold Nanoparticles by Modified Polyelectrolyte Deposition Technique
Authors: Jafri S. H. M. , Sharma A. B. , Thanachayanont Chanchana , Dutta Joydeep
Published: April 2011

Fabrication strategies based on mechanisms of self-assembly are now widely being recognized as inevitable tools in nanotechnology. Self-organized construction of advanced materials and devices may be done starting with tailor made nanoparticles as building blocks. Multilayer thin films of gold, zinc sulphide and manganese doped zinc Sulfide nanoparticles were fabricated by a modified polyelectrolyte deposition process. A prerequisite to utilization of colloids for the fabrication of uniform layers is that they remain in suspension and resist unwanted agglomeration. The stability of colloids is generally achieved either by electrostatic stabilization, involving the creation of an electrical double layers arising from ions intentionally adsorbed on the surface of the particle and associated counter ions that surround the particle, or by steric hindrance that is achieved by the adsorption of macromolecules on the surface of the particles. The inherent necessity to introduce electrostatic or steric hindrance to avoid colloidal agglomeration was utilized to induce self-assembly of multilayers applying similar concept used for the layering of polyelectrolytes. Polyacrylic acid was used as the polyanion and chitosan as the polycation for the deposition process. Upto 100 layers of nanoparticles were constructed and films that were found to be stable and uniform over the substrate. The layer-by-layer deposition of multilayers of several different structures was prepared and devices showing resistive and capacitive electrical characteristics have been fabricated. The onset of electrical conduction in the resistive devices could be varied by introducing a dielectric interlayer between gold nanoparticles and by introducing a gold overlayer on the zinc sulphide nanoparticle devices.
Carbon nanotubes and nanostructures grown at below 400°C
Authors: Chen Guan Yow , Poa P.C.H. , Henley S.J. , Stolojan V. , Silva S.R.P.
Published: April 2011

In this paper, we report clear evidence for the growth of carbon nanotubes and nanostructures at low substrate temperatures, using direct-current plasma-enhanced chemical vapour deposition. The catalyst particles are mounted on a titanium layer which acts as a thermal barrier, and allows for a larger temperature gradient between the Ni catalyst surface and the substrate. A simple thermodynamic simulation shows that the temperature differential between the substrate growth surface and the growth electrode is determined by the thickness of the titanium layer. This facilitates the growth of nanotubes, as opposed to nanofibres with herring-bone or amorphous structures. The growth properties are discussed as a function of the bias voltage and hydrocarbon concentration. The heating during growth provided solely by the plasma is below 400°C and is dependent on the process conditions and the electrode configuration in the growth chamber. These conditions need to be taken into account when comparing processes across different growth methods and instruments. The novel approach based on the use of a thermal barrier ensures the synthesis of carbon nanotubes at room temperature substrate conditions, which can be attained with a suitable cooling scheme.
Effects of strain on the resonant Raman profile of metallic
Authors: Souza Filho Antonio G , Kobayashi N , Jiang Jie , Saito Riichiro , Cronin Stephen B , Mendes Filho Josue , Samsonidze Ge G , Dresselhaus Gene , Dresselhaus Mildred S
Published: April 2011

In this paper we report the effects of strain on the electronic properties of single wall carbon nanotubes and its consequence on the resonant Raman cross section. A quantum interference effect has been predicted for the radial breathing mode spectra for metallic tubes. For metallic tubes, the lower and upper components of Eii resulting from the trigonal warping effect are affected differently and for low chiral angle they cross for some strain value. Near (at) the crossing point, the resonant Raman spectra profile exhibits a maximum (minimum) value due to a quantum interference in the Raman cross section. This Raman cross section interference effect was observed in Raman experiments carried out on isolated SWNTs. The Raman experiment performed on an isolated strained metallic SWNT supports our modeling predictions.
Analysis of the Samples of Fe-Cu-Nb-Si-B Amorphous Alloys Obtained by Dynamic Compacting Method
Authors: Golubev Victor A. , Strikanov Andrey V. , Potemkin Grigory A. , Zueva Ludmila V. , Golubev Aleksey V. , Olenina Eleonora V. , Bugrov Vladimir G. , Sten’gach Aleksey V. , Faehl Rickey J.
Published: April 2011

The Dynamic Compacting (DC) method is promising method to produce considerable-size nonporous wares. The phenomenon is based on the impact of shock wave on the initial powders of amorphous alloys. Every time when the shock wave propagates through the bulk of substance then the temperature rises substantially. Therefore there is a need of study of the DC’s effect on the structure and properties of the amorphous alloys. The results of the thermal analysis (in particular, Differential Scanning Calorimetry) of the samples of the soft magnetic alloys are presented in the report. These results concern with amorphous alloys of 5BDSR, GM414, 10NSR trademarks before DC and after DC, respectively. It is shown there is single low-temperature endothermic peak (near 300C) and there are several high temperature exothermic peaks (near 540C, 650C, and 700C). The first peak is related to glass-transition, the following peaks are related to formation of nano-crystalline phases. It was proved by XRD analysis data. The optimal regimes of the thermal processing of final wares were chosen on the base of thermal- and XRD-analysis. The study of the effects of these regimes on the properties (magnetic conductivity, specific losses etc.) of the circular magnetic conductors was executed. In particular, thermal- as well as thermo-magnetic processing of magnetic conductors based on 5BDSR amorphous alloy (after DC) essentially improves their magnetic properties. For example, magnetic conductivity fÝ increases approximately by factor 17 with respect to the magnitude before DC.
Dynamic Compacting of Powders of Some Amorphous Alloys
Authors: Golubev Victor A. , Strikanov Andrey V. , Golubev Aleksey V. , Bugrov Vladimir G. , Potemkin Grigory A. , Kudel’kin Valery B. , Mochalov Mikhail A. , Faehl Rickey J.
Published: April 2011

At present amorphous metallic alloys have the broad expansion in various fields of science&engineering as a result of their unique properties. In particular, soft magnetic amorphous alloys are extensively used in electrical engineering. However the production of considerable-size nonporous wares based on the powders (or tapes) of these alloys is heavy problem owing to high hardness of the particles. Therefore shock wave’s compacting or Dynamic Compacting (DC) method is promising one to produce the wares on the base of powders of amorphous alloys because it can provides high strength and near zero porosity of the wares. The experimental D-U diagrams of soft magnetic amorphous alloys were obtained to realize this method of compacting. The calculations of the amplitude and duration of shock wave were carried out. The several versions of explosive devices using shock plane wave generator to produce circular magnetic conductors were developed and were tested. These magnetic conductors are based on amorphous alloys of 5BDSR, GM414, 10NSR trademarks (Fe with Cu, Nb, Si, B additives). XRD analysis proved that amorphous state of the alloys remains the same up to 20 GPa shock wave’s pressures. The mechanical, structural, electrical and magnetic properties both initial amorphous alloys and compacted one were obtained and compared as a result of the implemented works. It was stated that DC leads to increase of magnetic conductivity by factor ∼15 with respect to initial amorphous alloys powder. Besides the specific losses decrease in ∼4 times.
Strain measurement in metallic glasses and metallic-glass-matrix composites by means of x-ray scattering
Authors: Hufnagel Todd , Ott Ryan T. , Almer Jon
Published: April 2011

The availability of high-energy synchrotron beamlines has made it possible to study the development of elastic strain in crystalline phases in metallic-glass-matrix compositesin situduring loading, and to measure elastic strain in amorphous materials as well. In this paper, we discuss experimental techniques and data analysis for these measurements and give examples. We show that the strain in both the amorphous and crystalline phases in a metallic-glass-matrix composite can be extracted from a single scattering pattern.
Rate Sensitivity and Size Effects in Plasma-Enhanced Chemical Vapor Deposited Silicon Oxide Films
Authors: Cao Zhiqiang , Zhang Xin
Published: April 2011

Plasma-enhanced chemical vapor deposited (PECVD) silicon oxide (SiOx) thin films have been widely used in MEMS to form electrical and mechanical components. In this paper, both the time-independent and the time-dependent plastic responses of the PECVD SiOx films were studied by the instrumented nanoindentation experiments. Our experiments found an enhanced rate-sensitivity and size-effect in the plastic responses of the PECVD SiOx thin films. In addition, the plastic flow behavior is more homogeneous compared with most inorganic glasses and many metallic glasses. The deformation mechanism in the PECVD SiOx thin films is depicted by the shear transformation zone (STZ) based amorphous plasticity theory. The physical origin of the STZ is elucidated and linked with the plastic deformation dynamics.
High Electron Mobility W-doped In2O3 Thin Films
Authors: Newhouse Paul F. , Park Cheol-Hee , Keszler Douglas A. , Tate Janet , Nyholm Peter S.
Published: April 2011

High electron mobility thin films of In2−xWxO3+d (0 ≤ × ≤ 0.075) were prepared by pulsed laser deposition. The highest mobility polycrystalline and textured films show mobility >110 cm2/Vs on both amorphous SiO2 and single crystal yttria-stabilized zirconia substrates. The carrier density is in the range 1−3 × 1020 cm−3 at room temperature. The W dopant concentration for films with optimized electrical properties was x ∼ 0.03.
Reliable semi-transparent pentacene thin-film transistors with polymer gate dielectric layers cured at an optimum temperature
Authors: Hwang Do Kyung , Park Ji Hoon , Choi Jeong Min , Lee Jiyoul , Jeong Seong Hun , Kim Eugene , Kim Jae Hoon , Im Seongil
Published: April 2011

We report on the insulator-charging-effects of poly-4-vinylphenol (PVP) gate dielectric on the reliabilities of pentacene thin-film transistors (TFTs). Our PVP films were prepared by spin coating and curing at various temperatures (155, 175, and 200 °C). Evaluated using Au/PVP/p+−Si structures, the dielectric strength of PVP films cured at 175 °C was superior to those of the other PVP films cured at different temperatures. Although saturation current and field mobility (∼0.13 cm2/Vs) obtained from a TFT with PVP film cured at 200 °C appeared higher than those (∼0.07 cm2/Vs) from the device with 175 °C-cured polymer film, the TFT prepared at 200 °C revealed a low on/off current ratio of less than 104 due to its high off-state current and also unreliable saturation behavior under repetitive gate voltage sweep. The unreliable behavior is due to the dielectric-charging caused by gate-electron-injection. We thus conclude that there are some optimal PVP-curing conditions to improve the reliability of pentacene TFT.
Development of a low energy Ne atom scattering system for insulator surface strctural analysis
Authors: Umezawa Kenji , Narihiro E , Oda K , Nakanishi Shigemitsu , Gibson Walter M
Published: April 2011

We have been developing a low energy Ne atom scattering system combined with a time-of-flight spectrometer for insulator surface structural analysis. Insulator surface structure is difficult to study because of charging effects during electron or ion beam bombardment. Structural analyses of insulator surfaces are very important in fundamental research as well as technology fields. In our system, charged ion beams of 2 keV-Ne+ are converted into neutral beams by charge exchange with the same element gas after the primary beam passes through a chopper. Other features of this system are pulsed beams, time-of-flight measurements, and a micochannel plate (MCP) detector is coaxially mounted along the primary beam. This is a home made equipment. We will show the detection systems, as well.
Ion beam modification of polyimides with linear ion source
Authors: Yamaguchi Tetsuro , Hsiao Shih Hsiu , Tanaka Yoshikazu , Ide Ektessabi Ari
Published: April 2011

Polyimide films are widely used in various industrial fields. Some typical products are flexible printed circuits (FPCs), flexible displays, and electronic papers. Good adhesion between metal thin films and polyimide films is required for their long lifetime. Ion beam irradiation to the polyimide films modifies the chemical compositions, the chemical states, and the surface nanomorphology. These modifications are potential techniques to improve the adhesion. In this study, the authors employed a linear ion source, which is able to irradiate ion beam on large surfaces homogeneously. The linear ion source is desirable for industrial usage because of its high productivity. The aim of this work was to investigate the effect of modification using the linear ion source. The chemical states of the interface were characterized using x-ray photoelectron spectroscopy (XPS). The surface nanomorphology was investigated by atomic force microscopy (AFM). The performance of the modification system will be discussed, and the characteristics of the modified polyimide will be investigated in detail.
NSF NSDL Materials Digital Library & MSE Education
Authors: Bartolo Laura M. , Glotzer Sharon C. , Lowe Cathy S , Powell Adam C. , Rajan Krishna , Sadoway Donald R. , Warren James A. , Tewary Vinod K.
Published: April 2011

The National Science Foundation created the National Science Digital Library (NSDL) in order to establish a technical, communal, and organizational framework for access to high quality resources and tools that support innovations in teaching and learning at all levels of science, technology, engineering, and mathematics education. As part of the NSDL, the Materials Digital Library (MatDL) Pathway focuses specifically on serving the materials science (MS) community with a target audience that includes MS undergraduate and graduate students, educators, and researchers. MatDL is a collaborative effort involving the Materials Science and Engineering Laboratory at the National Institute of Standards and Technology, Kent State University, Massachusetts Institute of Technology, University of Michigan, Iowa State University, and Purdue University. Our network of collaborations also includes a Nanoscience Interdisciplinary Research Team, Materials Research Science and Engineering Center, and International Materials Institute. A primary goal of MatDL is to bring materials science research and education closer together. MatDL provides innovative uses of digital libraries and the web as educational media in the MS community with particular emphasis on providing: 1) tools to describe, manage, exchange, archive, and disseminate scientific data 2) workspace for open access development of modeling and simulation tools 3) services and content for virtual labs in large undergraduate introductory science courses, and 4) workspace for collaborative development of core undergraduate MS teaching resources for emerging areas. This paper will provide an overview of the NSDL MatDL Pathway, details about specific aspects of the project, as well as interactions between research and education.
The Future of Materials Undergraduate Programs: Can we Avoid Extinction?
Authors: Vanasupa Linda
Published: April 2011

In materials research, the current funding focus has shifted from largely mechanical-properties based aspects of materials to their molecular-level chemical nature, such as biomaterials or nanoscale phenomenon. Along with this shift in emphasis, we have seen many undergraduate materials programs become absorbed by other programs as a concentration in other engineering majors. Many programs have absolved departments in favor of a model where faculty from a variety of departments have adjunct appointments in, say, an interdisciplinary materials science and engineering program. What exactly is the fate of undergraduate materials programs? Is it time for materials science and engineering undergraduate programs to be absorbed into the sea of interdisciplinarity? In this talk, I will present data on the landscape of trends within the undergraduate materials community against the changes in the global arena. What is our role as materials science and engineering educators in the societal state of flux that we face? What are the opportunities? In an attempt to see into the future, we will consider all these questions.
Simulation of Realistic Core-shell Silicon Nanowires
Authors: Biswas Rana , Pan Bicai
Published: April 2011

We have developed an efficient scheme for simulating silicon nanowires with crystalline cores and amorphous sheaths, using molecular dynamics. By starting with a crystalline nanowire and performing high temperature anneal an amorphous outer sheath can be grown with controlled thickness on the nanowire. Simulations for [001] nanowires with diameters of 12 nm find low energy facets between the amorphous and crystalline layers. Simulations for [110] nanowires find weak faceting and an inhomogeneous amorphous-crystalline boundary.
Metastability in Hydrogenated Nanocrystalline Silicon Solar Cells
Authors: Yue Guozhen , Yan Baojie , Ganguly Gautam , Yang Jeffrey , Guha Subhendu
Published: April 2011

We have recently reported that hydrogenated nanocrystalline silicon (nc-Si:H) solar cells exhibit metastability behavior that is significantly different from hydrogenated amorphous silicon (a-Si:H) solar cells. First, we studied the light-induced change of nc-Si:H cells under different light spectra, and observed that no light-induced degradation occurs when the photon energy is lower than the bandgap of a-Si:H, while light-induced degradation indeed occurs when the photon energy is higher than the bandgap of a-Si:H. Based on this observation, we conclude that the light-induced defect generation occurs mainly in the amorphous and/or grain boundary regions. Secondly, we found that forward-bias current injection in the dark does not cause any degradation in the performance of nc-Si:H cells, in contrast to observations in a-Si:H cells. This phenomenon can be explained by assuming transport percolation through crystallites, where excess carrier recombination does not cause degradation. Third, we found that a reverse electrical bias does not reduce, but rather enhances the light-induced degradation in the nc-Si:H cell performance. This enhancement increases with the magnitude of the reverse bias. We carried out a systematic study including measurements of quantum efficiency losses and fill factors under different color filters. In view of the heterogeneity of the material structure, we proposed a “back-to-back” diode model which explains most of the experimental results. Finally, we present results of the improvement of stability of nc-Si:H cells made using hydrogen dilution profiling. We find that the nc-Si:H cells with an optimized hydrogen dilution profile show very little light-induced degradation though these cells have a high amorphous volume fraction. This indicates that the amorphous volume fraction is not the only factor determining the degradation. Other factors, such as the structure and distribution of the amorphous phase, as well as the properties of the grain boundaries, apparently play important roles in the overall stability of nc-Si:H cells.
Nucleation and Growth of Quasicrystalline Silicon Thin Films on Glass Substrate Synthesized by Ceramics Hot Wire Chemical Vapor Deposition
Authors: Middya Abdul Rafik , Liang Jian-Jun , Ghosh Kartik
Published: April 2011

In this work, we report on nucleation and growth of silicon thin films on glass substrate with “five-fold” symmetry and “six-fold” symmetry by ceramics hot wire chemical vapor deposition. We observed “confinement of heat and photon” is a powerful approach in developing silicon thin films with novel structure, i.e. quasicrystalline silicon thin films on glass substrate. We found unambiguously that photons emitted from the hot filament influence the nucleation of nanocrystal silicon that produces new type of silicon thin films with “five-fold” symmetry and “six-fold” symmetry.
Relationship between Phase Shift, Square-Wave Response and Density of States in Modulated Photocurrent Spectroscopy
Authors: Reynolds Steve , Main Charlie
Published: April 2011

Low- and high-frequency modulated photoconductivity measurements (LF and HF MPC) have been made on amorphous silicon films prepared by the expanding thermal plasma (ETP) and RF PECVD techniques. Time constants have been measured by decay of square wave excitation and behavior of complex frequency response. The influence of quasi-Fermi level position has been examined. Band tail slopes of 32 meV (ETP) and 37 meV (PECVD), and defect densities of order 1018 and 1017 cm-3 eV-1 respectively are found. Tail state capture coefficients of order 3×10-8 cm3 s-1 are calculated from overlapping LF and HF regimes. Defect state values for ETP (< 10-8 cm3 s-1) are smaller than for PECVD silicon films (> 10-7 cm-3 s-1).
Low Temperature Fabrication of Microcrystalline Silicon Germanium Films by RF Reactive Magnetron Sputtering
Authors: Nakamura Isao , Ajiki Toru , Isomura Masao
Published: April 2011

Microcrystalline silicon germanium films (μc-SiGe) were fabricated on Corning #7059 glass substrates by the RF reactive magnetron sputtering method. The μc-SiGe films with Ge fraction of 0.7-0.8 could be crystallized at of 200 °C by H2 introduction into the sputtering gases. The absorption coefficients of the films decrease in long wavelength region corresponding to the photon energies below the energy gap by the decrease in the substrate temperature and become close to those of single crystal Si0.25Ge0.75. The dark conductivities show lower values of 10-7 S/cm at 200 °C and 300 °C with H2 introduction. Besides, the photosensitivities are observed in these samples. These results indicate that the H2 introduction into the sputtering gas has two important effects to decrease the crystallization temperature of the μc-SiGe and to improve the film properties by reducing the dangling bond defects.
Image Sensors Based on Thin-film on CMOS Technology: Additional Leakage Currents due to Vertical Integration of the a-Si:H Diodes
Authors: Miazza Clement , Wyrsch N. , Choong G. , Dunand S. , Ballif C. , Shah A. , Blanc Nicolas , Kaufmann R. , Lustenberger F. , Moraes D. , Despeisse M. , Jarron P.
Published: April 2011

Image sensors based on thin-film on CMOS technology (TFC) have been developed. In this approach, amorphous silicon (a-Si:H) detectors are vertically integrated on top of a CMOS readout chip so as to form monolithic image sensors. In order to reduce as far as possible the dark current density (Jdark) of the TFC sensors, we have focused on analyzing and understanding the behavior of Jdark in this type of detectors. Edge effects along the periphery and at the corners of the pixel, due to the non planar configuration of the vertically integrated photodiodes, are found to be responsible for an increase of the dark current. A new and adapted solution for the minimization of Jdark is proposed, which combines the use of a metal-i-p a-Si:H diode configuration with a deposition on top of an unpassivated CMOS chip. Values of Jdark as low as 12 pA/cm2 at a reverse polarization of V = -1 V are measured on such TFC sensors.
Nano-Crystalline Silicon Thin Film Transistors on PET Substrates Using a Hydrogenation-assisted Metal-induced Crystallization Technique
Authors: Behnam Ashkan , Haji Saber , Karbassian Farshid , Mohajerzadeh Shams , Ebrahimi Aida , Abdi Yaser , Robertson Michael D
Published: April 2011

The effects of RF-Plasma hydrogenation and applied mechanical strain on the crystallization of silicon layers deposited on plastic substrates have been investigated where the maximum temperature remained below 170 °C for the entire process. The structural properties of the samples have been studied by optical, scanning-electron and transmission-electron microscopies where the nano-crystallinity of the silicon layers has been confirmed. The maximum average diameter of the silicon grains was 4.5 nm and occurred for an applied tensile strain of 4 %. In addition, a thin-film transistor on a plastic substrate has been fabricated and found to possess an electron mobility of 2.4 cm2/Vs.
Defect States in Excimer-Laser Crystallized Single-Grain TFTs Studied with Isothermal Charge Deep-level Transient Spectroscopy
Authors: Nadazdy Vojtech , Rana V. , Ishihara R. , Lanyi S. , Durny R. , Metselaar J.W. , Beenakker C.I.M.
Published: April 2011

Defect states were quantitatively evaluated in single-grain (SG) Si thin-film transistors (TFTs), prepared by micro-Czochralski (grain filter) process with excimer-laser crystallization, by means of isothermal charge deep-level transient spectroscopy with a high sensitive charge/voltage converter. Its sensitivity reaches 10-16 C and it operates in the range of 2 microseconds - 10 ms. Measurements were performed on the SG-Si TFTs with various energy densities of laser crystallization, various channel areas, and positions in the grain. Our results indicate a direct correlation of fabrication parameters, parameters of the TFT determined from its transfer characteristics, and parameters of defect states (energy position in the band gap, concentration) induced by coincidence site lattice boundaries inside the location-controlled grains and by defects in the grain filter.
Post Deposition Ultraviolet Treatment of Silicon Nitride Dielectric: Modeling and Experiment
Authors: Zubkov Vladimir , Balseanu Mihaela , Xia Li-Qun , M'Saad Hichem
Published: April 2011

Simulation and FTIR analysis of the UV treatment impact on bond strengths of PECVD deposited silicon nitride films
Characterization of Nickel Induced Crystallized Silicon by Spectroscopic Ellipsometry
Authors: Pereira Luis , Aguas Hugo , Beckers Manfred , Martins Rui M. S. , Fortunato Elvira , Martins Rodrigo
Published: April 2011

In this work Spectroscopic Ellipsometry (SE) was used to study metal induced crystallization (MIC) on amorphous silicon films in order to analyze the influence of different annealing conditions on their structural properties. The variation of the metal thickness has shown to be determinant on the time needed to full crystallize silicon films. Films of 100 nm thickness crystallize after 2h at 500°C using 1 nm of Ni deposited on it. When reducing the average metal thickness down to 0.05 nm the same silicon film will need almost 10 hours to be totally crystallized. Using a new approach on the modelling procedure of the SE data we show to be possible to determine the Ni remaining inside the crystallized films. The method consists in using Ni as reference on the Bruggeman Effective Medium Approximation (BEMA) layer that will simulated the optical response of the crystallized silicon. Silicon samples and metal layers with different thicknesses were analyzed and this new method has shown to be sensible to changes on the initial metal/silicon ratio. The nickel distribution inside the silicon layers was independently measured by Rutherford Backscattering Spectroscopy (RBS) to check the data obtained from the proposed approach.
Low Thermal Budget Techniques For Controlling Stress In Si1-XGeX Deposited At 210°C
Authors: Sedky Sherif , Mortagy Omar , Witvrouw Ann
Published: April 2011

This work reports, for the first time, on the possibility of realizing surface micromachined silicon germanium structures at 210°C, which have extremely low strain gradient (μm-1). This extremely low strain gradient is obtained by tuning the physical properties of Si1-xGex, locally, without affecting the underlying layers, by excimer laser annealing. Tuning the laser annealing condition to optimize the physical properties of PECVD Si1-xGex is challenging, especially for films deposited at low temperatures (~ 250°C or lower) due to the high hydrogen content and the poor adhesion of these films. Furthermore, optimizing some properties might be at the cost of others. To clarify this issue, it is interesting to note that reducing the electrical resistivity implies using high laser pulse fluence. This however will increase mean stress, strain gradient and surface roughness as will be shown in this work.
High Quality Hot-wire Microcrystalline Silicon for Efficient Single and Multijunction N-i-p Solar Cells
Authors: Stolk Robert L. , Li Hongbo , Franken Ronald H. , Van der Werf Karine H.M. , Rath Jatindra K. , Schropp Ruud E.I.
Published: April 2011

In this paper, the potential of hot-wire chemical vapor-deposited (HWCVD) microcrystalline silicon (μc-Si) for use in solar cells is explored. Incorporation of the material in the current-limiting bottom cell of two tandem cells on plain stainless steel resulted in FF values as high as 0.77, which is much higher than the highest single junction FF. A combination of experiments, calculations and computer simulations was employed to identify causes for the observed high tandem cell FF values. Both the light intensity and the spectral composition of the bottom cell illumination in a tandem were found to contribute to an increase of the bottom cell FF. The fact that the operational voltage of a tandem cell is higher than that of the current-limiting subcell, was calculated to lead to a tandem FF that can be far higher than that of the limiting cell. Com-puter simulations with the AMPS computer code show that the current mismatch in a tandem cell reduces the recombination in the current-limiting cell, possibly by slightly enhancing the internal field of that cell. Use of a 1.5 μm ìc-Si:H hot-wire deposited absorber layer in a single junction cell on a textured back reflector yielded a Voc, FF and Jsc of 0.543 V, 0.656 and 23.60 mA/cm2, respectively, which combine to an 8.4 % record efficiency for μc-Si single junction n-i-p cells with a hot-wire intrinsic layer.
Millisecond Annealing: Past, Present and Future
Authors: Timans Paul , Gelpey Jeff , McCoy Steve , Lerch Wilfried , Paul Silke
Published: April 2011

The challenge of achieving maximal dopant activation with minimal diffusion has re-awakened interest in millisecond-duration annealing processes, almost two decades after the initial research in this field. Millisecond annealing with pulsed flash-lamps or scanned energy beams can create very shallow and abrupt junctions with high concentrations of electrically active carriers, but solutions for volume manufacturing must also meet formidable process control requirements and economic metrics. The repeatability and uniformity of the temperature cycle is the key for viable manufacturing technology, and the lessons from the development of commercial rapid thermal processing (RTP) tools are especially relevant. Advances in the process capability require a fuller understanding of the trade-off between dopant activation, defect annealing. diffusion and deactivation phenomena. There is a strong need for a significant expansion of materials science research into the fundamental physical processes that occur at the short time scales and high temperatures provided by millisecond annealing.
Germanium & Carbon Co-implantation for Enhanced Short Channel Effect Control in PMOS Devices
Authors: Dumont Benjamin , Pouydebasque Arnaud , Pawlak Bartek , Oudet Benjamin , Delille Dominique , Milesi Frederic , Souifi Kader , Skotnicki Thomas
Published: April 2011

This work demonstrates the efficiency of a Germanium and Carbon co-implantation that suppresses the Boron Transient Enhanced Diffusion, enhances Boron activation and enables large improvement of Short Channel Effects in PMOS devices while maintaining drive current performances. We present here 65/45nm node devices on conventional bulk substrates featuring Germanium and Carbon engineered shallow junctions that enable to reduce the Drain Induced Barrier Lowering compared to devices implanted only with Boron. This improvement is attributed to the suppression of Boron channelling with Ge pre-amorphization (PAI), and to the reduction of Boron TED due to the trapping of interstitial defects by Carbon with Germanium PAI.
Defect Evolution During Laser Annealing
Authors: Felch Susan B. , Mayur Abhilash , Parihar Vijay , Nouri Faran , Jones Kevin S. , Zeenberg Daniel E. , Jones Britta E.
Published: April 2011

Implementation of millisecond annealing requires the identification of the operating conditions for that technique which minimize the residual defects. In addition, possible combinations of low temperature annealing with millisecond annealing could result in minimal residual defects. The samples studied here were implanted with Ge+ pre-amorphization and boron dopant ions and were activated with a scanning laser annealing technique with maximum temperature dwell times of about one millisecond. The laser anneal conditions were varied, along with combinations of spike anneals. The annealed samples were analyzed by plan-view transmission electron microscopy (TEM) to measure the residual defect density and size. The effects of spike temperature, laser annealing temperature, and scan rate will be discussed.
Physical Modeling of Defects, Dopant Activation and Diffusion in Aggressively Scaled Bulk and SOI Devices: Atomistic and Continuum Approaches
Authors: Moroz Victor , Martin-Bragado Ignacio
Published: April 2011

In this overview we examine how advanced continuum and atomistic modeling can help to understand and resolve process and device design issues for the 65 nm technology generation and beyond. The following implantation-related issues are reviewed: wafer temperature for different types of implant equipment and its impact on defect formation and amorphization, ion scattering off the photoresist mask and its impact on threshold voltage variation, dual rotation halo implant instead of the conventional quad rotation halo implant, and engineering of the source/drain junction overlap for diffusionless annealing by using tilted implants. The following annealing-related issues are also considered: limitations of spike anneal; benefits of cocktail junctions, heat transfer mechanisms for spike and millisecond annealing, and implant damage evolution for different thermal budgets. Taken together, implant, annealing, and layout conditions are shown to explain observed threshold voltage and transistor performance variations. In addition, the effects of transistor geometry on dopant diffusion, activation, and defect formation are shown for several generations of bulk and FDSOI MOSFETs.
Structure and Process Parameter Optimization for Sub-10nm Gate Length Fully Depleted N-Type SOI MOSFETs by TCAD Modeling and Simulation
Authors: Jin Yawei , Ma Lei , Zeng Chang , Dandu Krishnanshu , Barlage Doug William
Published: April 2011

According to most recent 2004 International Technology Roadmap for Semiconductor (2004 ITRS), the high performance (HP) MOSFET physical gate length will be scaled to 9nm (22nm technology node) in 2016. We investigate the manufacturability of this sub-10nm gate length fully depleted SOI MOSFET by TCAD simulation. The commercial device simulator ISE TCAD is used. While it is impractical for experiments currently, this study can be used to project performance goals for aggressively scaled devices. In this paper, we will optimize different structure and process parameters at this gate length, such as body thickness, oxide thickness, spacer width, source/drain doping concentration, source/drain doping abruptness, channel doping concentration etc. The sensitivity of device electrical parameters, such as Ion, Ioff, DIBL, Sub-threshold Swing, threshold voltage, trans-conductance etc, to physical variations will be considered. The main objective of this study is to identify the key design issues for sub-10nm gate length Silicon based fully depleted MOSFET at the end of the ITRS. The paper will present the final optimized device structure and optimized performance will be reported.
BCl3/N2 Plasma for Advanced non-Si Gate Patterning
Authors: Shamiryan Denis , Paraschiv Vasile , Eslava-Fernandez Salvador , Demand Marc , Baklanov Mikhail , Boullart Werner
Published: April 2011

As conventional materials in CMOS manufacturing, Si as a gate material and SiO2 as a gate dielectric, approach their performance limit, the search for new materials becomes key point. Patterning of the new stacks containing these materials require both new plasma etch chemistries and new approaches.

We propose a BCl3/N2 based plasma mixture for the advanced gate patterning (in this case pure Ge gates and TaN metal gates). There are three reasons to select this combination:

a) The gas mixture generates Cl* species able to etch a diversity of materials, b) it is selective towards Si due to formation of passivating Si-B bonds and c) it improves profile control possibly by formation of a passivating BN-like film on feature side walls. It was found that BCl3 in presence of N2 results in a film deposition if no bias is applied to the substrate (i.e. there is no ion bombardment). The film is hexagonal BN-like since the characteristic peaks corresponding to the in-plane B-N and out-of-plane B-N-B bonds were found in FTIR spectra. The composition of the film surface as found by XPS is B, N and O (as no O2 is present in the plasma it may be a result of oxidation in the atmosphere), the amount of Cl is approx. 1%. The film is soluble in water that makes its removal easy. The deposition rate can be as high as 300 nm/min depending on plasma power, pressure, flow rates and BCl3 to N2 ratio.

We propose to use the BCl3/N2 mixture to etch materials too sensitive to Cl-based plasma. Pure BCl3 plasma might distort gate profiles, as materials are etched in a lateral direction as well, this is the case, e.g. for pure Ge gates. Addition of small amount of nitrogen (5% to 10%) to the BCl3 plasma preserves the vertical profile, apparently by the formation of a passivating BN-like layer on the vertical surfaces where there is no ion bombardment. Too high nitrogen concentration results in positively sloped gate profile or even in the etch stop that could be attributed to the too high deposition rate that exceeds the etch rate. All experiments have been performed in Lam Versys 2300 etch chamber.
Layer Transfer of Hydrogen-Implanted Silicon Wafers by Thermal-Microwave Co-Activation
Authors: Yang Y. Y. , Huang C. H. , Hsu Y. -K. , Jeng S. -J. , Tai C. -C. , Lee S. , Chen H. -W. , Gan Q. , Chu C. -S. , Ting J. -H. , Lai C. S. , Lee T. -H.
Published: April 2011

Silicon on insulator (SOI) substrate is a key materials for nano-scaling IC device and the requirement for its crystal structure and quality is really high. Nanothick silicon thin film can be transferred onto a handle wafer from a donation wafer to form a SOI wafer after this process including hydrogen implantation of donation wafer, wafer bonding, and thermal treatment at moderately high temperatures of 400 to 600 degree centigrade. The expansion of the hydrogen molecular evolving from the implanted hydrogen ions interacting with silicon dangling bonds and trapped inside the microcavities located near the ion projected range resulted in exfoliation of the silicon thin film in the final heating step. The hydrogen molecules inside the microcavities tend to expand along the bonded interface rather than radially to form individual blisters. Finally, the fracture failure of ion implanted area parallel to the bonded interface near the projected ion range is formed by the sideway expansion of the cavities due to the diffusion supply of implanted hydrogen excited by thermal energy. Microwave processing can lower the activity energy to speed the chemical reaction so that it leads the format of microcavities occurring at low temperature by directly exciting the implanted hydrogen ions by microwave energy and also results in decreasing the critical dosage for layer splitting. However, microwave irradiation alone at room temperature causes the formation of lots of nucleus sites of micro-voids filled by hydrogen molecule which is immobility in silicon resulting in the issue of uniformity of transferred layer. In this study, the hydrogen implanted silicon substrate was irradiated by microwave at low temperature (200 degree centigrade) rather than microwave alone to co-activate the implanted hydrogen ions in silicon to increase not only kinetic energy but also mobility to successfully achieve a completely transferred layer in a short time.
Moisture Induced Degradation of Porous Low-k Materials
Authors: Baklanov Mikhail , O'Dwyer David , Urbanowicz Adam M , Le Quoc Toan , Demuynck Steven , Hong Eun Kee
Published: April 2011

Interaction of moisture with porous low-k films is evaluated by using in situ ellipsometry setup. The adsorbed water amount is calculated from change of refractive index measured during the adsorption. Pristine low-k films reversibly adsorb 2 - 5% of water that reflects presence of constitutive hydrophilic centrums. Plasma and thermal treatments increase the number of hydrophilic centrums. Once the amount of these centrums has reached a certain critical value sufficient to form a continuous water film, bulk water condensation is observed. Change of properties during the water adsorption in the damaged films is not fully reversible. Each additional adsorption cycle increases the dielectric function of the film because of decreasing porosity, increasing skeleton density and shrinkage. The pressure corresponding to the bulk condensation allows us to calculate internal contact angle (internal surface energy) of low-k materials. The water molecules adsorbed on separate OH groups play the role of a catalyst that hydrolyses the siloxane bridges initially present on hydrophobic surface.
Low-Temperature PETEOS-to-PETEOS Wafer Bonding Using Titanium as Bonding Intermediate
Authors: Yu Jian , Moore Richard L. , Lee Sang Hwui , McMahon J. Jay , Lu Jian-Qiang , Gutmann Ronald J.
Published: April 2011

Bonding of pre-processed silicon wafers at back-end-of-the-line (BEOL) compatible conditions is one of the attractive approaches for three-dimensional (3D) integration. Among various technologies being evaluated, bonding of low temperature oxides (e.g., plasma-enhanced tetraethylorthosilicate (PETEOS)) is of great interest. In this work, we report low-temperature PETEOS-to-PETEOS wafer bonding, using a thin layer of titanium (Ti) as bonding intermediate. The bonding strength is evaluated qualitatively, while the bonding interface is examined by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). Preliminary results of PETEOS/Ti/PETEOS bonding on patterned wafers with single-level Cu damascene structures are also discussed.