bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical Vapor Deposition Coating for Micromachines
Authors: Mani S. S. , Fleming J. G. , Sniegowski J. J. , Boer M. P. De , Irwin L. W. , Walraven J. A. , Tanner D. M. , Dugger M. T. 
Published: April 2011

AbstractTwo major problems associated with Si-based MEMS devices are stiction and wear. Surface modifications are needed to reduce both adhesion and friction in micromechanical structures to solve these problems. In this paper, we will present a process used to selectively coat MEMS devices with tungsten using a CVD (Chemical Vapor Deposition) process. The selective W deposition process results in a very conformal coating and can potentially solve both stiction and wear problems confronting MEMS processing. The selective deposition of tungsten is accomplished through silicon reduction of WF6, which results in a self-limiting reaction. The selective deposition of W only on polysilicon surfaces prevents electrical shorts. Further, the self-limiting nature of this selective W deposition process ensures the consistency necessary for process control. Selective tungsten is deposited after the removal of the sacrificial oxides to minimize process integration problems. This tungsten coating adheres well and is hard and conducting, requirements for device performance. Furthermore, since the deposited tungsten infiltrates under adhered silicon parts and the volume of W deposited is less than the amount of Si consumed, it appears to be possible to release stuck parts that are contacted over small areas such as dimples. Results from tungsten deposition on MEMS structures with dimples will be presented. The effect of wet and vapor phase cleans prior to the deposition will be discussed along with other process details. The W coating improved wear by orders of magnitude compared to uncoated parts. Tungsten CVD is used in the integrated-circuit industry, which makes this approach manufacturable.
Synthesis and Characterization of α-Alumina Films Via Combustion Chemical Vapor Deposition
Authors: Grandinetti G. , Shanmugham S. , Hendrick M.R. , Hampikian J.M. 
Published: April 2011

Abstractα-Alumina films are useful for high-temperature, wear, and semiconductor device applications because of their good oxidation resistance, high hardness values, and electrical properties. α-Alumina films have been previously synthesized using techniques such as chemical vapor deposition, sol-gel, physical vapor deposition, and plasma spraying. This paper presents an alternative approach for producing high quality dense α-alumina coatings using a flame-assisted process called combustion chemical vapor deposition (CCVD). This process is an open atmosphere technique that does not require the use of a reaction chamber. In this work alumina films were grown on YSZ at temperatures ranging from 900 to 1500°C. At lower temperatures only amorphous alumina was grown, but as the deposition temperature increased different alumina phases were formed. At 1100°C, a thin highly crystalline θ-Al2O3 coating was formed. At temperatures higher than 1100°C thick θ-Al2O3 coatings were deposited on the YSZ. Coatings were characterized by scanning electron microscopy (SEM) and x-ray diffraction (XRD).
Vapor Phase Synthesis of II-IV Semiconductor Nanoparticles in a Counterflow Jet Reactor
Authors: Sarigiannis D. , Peck J.D. , Mountziaris T.J. , Kioseoglou G. , Petrou A. 
Published: April 2011

AbstractThe vapor-phase synthesis of polycrystalline ZnSe nanoparticles is reported. The particles were grown at room temperature and at a pressure of 125 torr in a counterflow jet reactor and were collected by impact on a Si watler. The precursors used in this study were vapors of (CH3)2Zn:[N(C2H5)3)]2 and H2Se gas diluted in hydrogen. These precursors have been used in the past for Metalorganic Vapor Phase Epitaxy (MOVPE) of ZnSe thin films. The particles were characterized by Transmission Electron Microscopy (TEM). electron diffraction. and Raman spectroscopy. The reactor was operated in a continuous, steady-state mode using a gas delivery system that is typical flor MOVPII systems.
A Parallel Detecting, Spectroscopic Ellipsometer for Intelligent Process Control of Continuously Deposited CIGS Films
Authors: Simpson L. J. , Joshi B. S. , Gonzales L. A. , Verley J. , Furtak T. E. 
Published: April 2011

AbstractAdvanced materials processing involves active control of fabrication and real-time monitoring of the final product. Sensors must be an integral part of the overall material processing system. ITN Energy Systems, Inc. and the Colorado School of Mines have developed a Parallel Detection, Spectroscopic Ellipsometer (PDSE) sensor for in-situ, real-time characterization and process control of multi-layered vapor deposited films. By measuring changes in the polarization state of reflecting light as a function of wavelength (250 to 5000 nm), the PDSE sensor determines the complex reflectance and/or the ellipsometric amplitude and phase. The PDSE provides cost-effective in-line sensing for film process control through detection of critical product variables that directly relate to film performance including: film thickness, optical excitation states, impurity concentrations, conductivity/resistance, intermixing at interfaces, microstructure, surface roughness, void fraction, defects, and grain size. The PDSE sensor is an optical probe with no moving parts that can measure the optical properties of thin films in as little as 3 msec with sensitivity to films less than a monolayer in thickness. We will use this PDSE system to provide real time process control of vapor deposited CuInGaSe2 (CIGS) films on a continuous flexible substrate. Initial results from CIGS films indicate that the PDSE has the sensitivity and accuracy to provide intelligent process control. The remaining challenge is to develop interpretive algorithms; the amount and quality of information required will determine their complexity. In addition, with the inception of in-situ, real-time monitoring, we hope to enable minimal data analysis approaches1 that provide extremely useful information with minimum interpretive algorithm development.
Atomic Layer Deposition of thin Films Using Sequential Surface Reactions
Authors: George S. M. , Ferguson J.D. , Klaus J.W. 
Published: April 2011

AbstractThin films can be deposited with atomic layer control using sequential surface reactions. The atomic layer deposition (ALD) of compound and single-element films can be accomplished using the appropriate surface chemistry. This paper reviews the ALD of dielectric alumina (Al2O3) films and conducting tungsten (W) films. The Al2O3 films are deposited on submicron BN particles and the surface chemistry is monitored using Fourier transform infrared (FTIR) spectroscopy. Additional transmission electron microscopy (TEM) studies investigated the conformality of the Al2O3 growth on the BN particles. FTIR investigations of the surface chemistry during W ALD are performed on nanometer-sized Si02 particles. Additional in situ spectroscopy ellipsometry studies of W ALD on Si(100) established the W ALD growth rates. Al2O3 and W ALD both illustrate the potential of ALD to obtain conformal and atomic layer controlled thin film growth using sequential surface reactions.
Investigation On Laser-Induced Effects In Nanostructure Fabrication With Laser-Irradiated Scanning Tunneling Microscope Tips in Air Ambient
Authors: Mai Z. H. , Lu Y. F. , Song W. D. , Chim W. K. 
Published: April 2011

AbstractIn this paper, we report our investigation on the kinetics of nanostructure fabrication on gold films and on H-passivated Ge surfaces. The relationship between the current and the tip-sample distance of the STM junction was measured for both gold films and H-passivated Ge surfaces. The tip-sample distance for gold films under a electrochemically etched W tip is approximately 2 nm, while that for H-passivated Ge sufaces is more than 27 nm. The thermal expansion length of the tip under laser irradiation was calculated. From the comparison of the thermal expansion length and the tip-sample distance, we can reach the conclusion that for gold films, thermal mechanical indention is the primary reason of nanostructure formation, while for H-passivated Ge surfaces, optical enhancement is the only reason.
Preparation Of Superhard Functionally Graded Tetrahedral Amorphous Carbon Coatings By Pulsed Laser Deposition
Authors: Wei Q. , Yamolenko S. , Sankar J. , Sharma A. K. , Narayan J. 
Published: April 2011

AbstractThe internal compressive stress as large as 10 GPa has been the major stumbling block for preparation of relatively thick superhard tetrahedral amorphous carbon (Ta-C) films. We have successfully deposited Ta-C films as thick as 1000 nm by mechanical doping to reduce and alleviate the level of internal compressive stresses. In this paper, we reported the preparation of functionally graded Ta-C coatings by pulsed laser deposition. The thickness of the Ta-C films with significantly improved adhesion was measured to be up to 1500 nm. The concentration of foreign atoms such as silver, copper, silicon and titanium was decreased away from the coating/substrate interface, and the surface layer was pure Ta-C. Nanoindentation measurements were performed on the coatings. Nanohardness as high as 65 GPa and Young‘s modulus as large as 600 GPa were obtained for the functionally graded Ta-C films. Micro-Raman measurements and microstructural analysis by transmission electron microscopy was carried out to acquire information about the bonding environment and atomic structure of the coatings as a function of foreign atoms. The results were discussed in combination with theoretical models associated with the prediction of elastic properties of amorphous carbon networks.
The Kinetics of Calcite Growth: Interpreting Chemical Affinity-Based Rate Laws Through the Lens of Direct Observation
Authors: Teng Henry H. , Dove Patricia M. , Yoreo James J. De 
Published: April 2011

ABSTRACTChemical affinity-based rate laws are used across the geochemical and materials communities to quantify mineral/material corrosion and growth kinetics. These rate expressions are founded in assumptions regarding reaction mechanism with little evidence for surface processes. Using Atomic Force Microscopy (AFM), this study demonstrates the dependence of growth kinetics upon the structures of dislocation sources. In situ observations show that the dominant mode of growth occurs by hillock development initiated at complex sources. Derivations of surface process-based rate expressions show a complex dependence of rate on chemical affinity. This dependence is approximated by second order affinity-based rate laws only under the special conditions that 1) growth proceeds by development of single sourced spirals and 2) growth occurs at very near equilibrium conditions where spiral formation is the only operative mechanism. This suggests that growth experiments that measure temporal changes in solution chemistry yield a composite rate that arises from the contributions of the different hillock types. Hence, chemical affinity-based rate laws do not generally give meaningful interpretations of growth mechanism. By combining direct observations with macroscopic methods that monitor temporal changes in solution chemistry, rate laws with greater predictive capabilities may be possible.
Templated Crystallization of Calcite on Patterned Self-Assembled Monolayers
Authors: Aizenberg Joanna 
Published: April 2011

ABSTRACTMicropatterned self-assembled monolayers (SAMs) that serve as substrates for nucleation provide a way of controlling various aspects of the crystallization process with a previously unreachable precision. We focus on crystallization of calcite (CaCO3) on SAMs of HS(CH2)nX (X = CO2H, CH3, SO3H, OH, N(CH3)3Cl) supported on Ag and Au. Fine-tuning of the crystallographic orientation of the forming crystals has been achieved by using different functional groups and metal substrates. By patterning SAMs with microregions having different nucleating activities and proper geometry, it is possible to confine crystallization to well defined, spatially delineated sites. This method provides means to fabricate arbitrarily patterned calcitic arrays with controlled density of nucleation, crystallographic orientation, and crystal sizes. The experimental conditions and the mechanisms discussed can be applied to the templated nucleation of a wide range of inorganic materials.
Nitrogen containing hydrogenated amorphous carbon prepared by integrated distributed electron cyclotron resonance for large area field emission displays
Authors: Conway N. M. J. , Godet C. , Equer B. 
Published: April 2011

ABSTRACTThe field emission properties of hydrogenated amorphous carbon containing up to 29at% nitrogen (a-C:N:H), grown in an integrated distributed electron cyclotron resonance (IDECR) reactor were studied using a sphere-plane geometry. All films were smooth in character and required a high field (20-70V/νm) activation process before emission, which created micron- sized craters in the emission region. Further analysis suggested that the emission originates from activation-created geometrically enhanced areas around the crater region. Upon low-level nitrogen incorporation (N/N+C≤0.2), the field required for activation decreased from 54V/νm to a minimum value of 20V/νm. The turn-on field required for 1νA of current also decreased, reaching a minimum of 11.3V/νm. The decrease in activation and turn-on field was related to the increase in conductivity observed with increasing nitrogen content. At higher nitrogen concentrations, the increase in activation energy and turn on field for emission may be due to changes in overall material structure, as indicated by the decreasing optical gap
The Effects of Microstructure on the Brightness of Pulsed Laser Deposited Y2O3:Eu Thin Film Phosphors for Field Emission Displays
Authors: Cho K. G. , Singh R. K. , Kumar D. , Holloway P. H. , Gao H-J. , Pennycook S. J. , Russell G. , Wagner B. K. 
Published: April 2011

ABSTRACTIn order to investigate the effect of microstructure on the brightness of thin film phosphors for field emission displays, Y2O3:Eu thin film phosphors were prepared using pulsed laser deposition. To deconvolute the effects experimentally, the Y2O3:Eu films of controlled thickness and microstructure were prepared on various substrate materials such as amorphous quartz, (0001) sapphire, (100) lanthanum aluminate (LaAlO3), and (100) silicon wafers. Cathodoluminescent brightness and efficiency of the films were obtained in both transmission and reflection modes. The Y2O3:Eu films deposited on the quartz substrates showed the maximum brightness followed by the films on (0001) sapphire, (100) lanthanum aluminate (LaAlO3), and (100) silicon substrates. The role of interface scattering of the emitted light on the film brightness will be discussed together with changing surface roughness and film thickness.
Field-Emitter-Array Cold Cathode Arc-Protection Methods - A Theoretical Study
Authors: Parameswaran L. , Murphy R.A. 
Published: April 2011

ABSTRACTField-emitter arrays (FEAs) are desirable for use as electron emitters in microwave-tube amplifiers because they can provide such advantages as higher efficiency and faster turn-on compared to their thermionic counterparts. Calculations have shown that Spindt-type metal and semiconductor emitters operate well below intrinsic current limits due to thermal effects, even for high-current applications such as klystrodes, twystrodes, and traveling-wave amplifiers. Nevertheless, the primary barrier to FEA utilization in such applications is premature failure due to arcing. These failures appear to be produced by ionization of gas molecules and/or desorbed contaminants, which are exacerbated by a poor vacuum environment. Lifetime and stability issues have been largely resolved for less stringent applications, such as flat-panel displays, through the use of integrated passive resistors that provide current limiting. However, such an approach is not directly compatible with operation at high frequency and current density. Other more complex approaches, such as the incorporation of active control in the form of integrated transistors, have also been demonstrated, but again, only for FEAs used in displays. This paper will review some of these schemes in the context of their efficacy in improving lifetime and stability of FEA cold cathodes in high-frequency applications. A theoretical analysis will be given of the effect on highfrequency performance of incorporating arc protection structures into Spindt-type metal FEAs. Specifically, two approaches will be considered: passive protection schemes such as the use of a modified thin film resistive layer, and active schemes such as FETs and saturated current limiters.
Electron Emission of Vertically Aligned Carbon Nanotubes Grown on a Large Area Silicon Substrate by Thermal Chemical Vapor Deposition
Authors: Lee Cheol J. , Park Jung H. , Son Kwon H. , Kim Dae W. , Lee Tae J. , Lyu Seung C. , Kang Seung Y. , Lee Jin H. , Park Hyun K. , Lee Chan J. , You Jong H. 
Published: April 2011

ABSTRACTWe have grown vertically aligned carbon nanotubes on a large area of Co-Ni codeposited Si substrates by thermal chemical vapor deposition using C2H2 gas. The carbon nanotubes grown by the thermal chemical vapor deposition are multi-wall structure, and the wall surface of nanotubes is covered with defective graphite sheets or carbonaceous particles. The carbon nanotubes range from 50 to 120 nm in diameter and about 130 μm in length at 950 °C. Steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically. The turn-on voltage was about 0.8 V/μm with a current density of 0.1 μA/cm2 and emission current reveals the Fowler-Nordheim mode.
Large Field Emission from Vertically Well-aligned Carbon Nanotubes
Authors: Sohn Jung Inn , Lee Seonghoon , Song Yoon-Ho , Choi Sung-Yool , Cho Kyoung-Ik , Nam Kee-Soo , Kang Young-Il 
Published: April 2011

AbstractWe have grown well-aligned carbon nanotube arrays by thermal chemical vapor deposition at 800°C on Fe nanoparticles deposited by a pulsed laser on a porous Si substrate. Porous Si substrates were prepared by the electrochemical etching of p-Si(100) wafers with resistivities of 3 to 6 ωcm. These well-aligned carbon nanotube field emitter arrays are suitable for electron emission applications such as cold-cathode flat panel displays and vacuum microelectronic devices like microwave power amplifier tubes. Field emission characterization has been performed on the CNT-cathode diode device at room temperature and in a vacuum chamber below 10−6 Torr. The anode is maintained at a distance of 60[.proportional]m away from the carbon nanotube cathode arrays through an insulating spacer of polyvinyl film. The measured field emitting area is 4.0×10−5cm2. Our carbon nanotube field emitter arrays emit 1mA/cm2at the electric field, 2V/[.proportional]m. And they emit a large current density as high as 80mA/cm2 at 3V/[.proportional]m. The open tip structure of our carbon nanotubes and their good adhesion through Fe nanoparticles to the Si substrate are part of the reason why we can attain a large field emission current density within a low field. The field emitter arrays in our diode device are vertically well-aligned carbon nanotubes on the Si-wafer substrate.
Thermal Properties of Single-Walled Carbon Nanotubes
Authors: Hone J. , Batlogg B. , Benes Z. , Llaguno M.C. , Nemes N.M. , Johnson A.T. , Fischer J.E. 
Published: April 2011

AbstractThe thermal properties of carbon nanotubes are strongly dependent on their unique structure and size, and show promise as an ideal material for thermal management on the micro- and macro-scale. The specific heat of nanotubes is similar to that of two-dimensional graphene at high temperatures, but is sensitive to the effects of rolling the the graphene sheet into a small cylinder at low temperatures. Specifically, the acoustic phonon modes are stiffened due to the cylindrical geometry, and the phonon spectrum is quantized due to the small diameter of the tube. In bundles of single-walled nanotubes, the specific heat is a sensitive probe of inter-tube mechanical coupling. Measurements of the specific heat show that inter-tube coupling is relatively weak, and show direct evidence for quantum effects. The thermal conductivity of nanotubes should reflect the on-tube phonon structure. Aligned bundles of SWNTs show a high thermal conductivity (>200 W/m-K at room temperature), and possible quantization effects at low temperature.
Three-Dimensional Electronic Surfaces
Authors: Sturm J.C. , Hsu P.I. , Miller S.M. , Gleskova H. , Darhuber A. , Huang M. , Wagner S. , Troian S. , Suo Z. 
Published: April 2011

AbstractThere is an increasing interest in electronics functionality on surfaces which are not planar. This paper examines the critical technologies for fabricating electronic surfaces which have a three-dimensional shape. Two different approaches for achieving such a goal are examined. One can fabricate electronics using conventional technologies on a flat surface, and then after fabrication deform that surface into the desired shape (e.g. a spherical cap). In an alternative approach, one can directly fabricate onto substrates with an arbitrary shape. In this case one must address the issue of pattern formation and transfer on the curved surfaces. The scaling of letterpress printing to micron-scale features on flat and spherically curved surfaces is demonstrated.
Nanofabrication Using Self-Assembled Alumina Templates
Authors: Rabin Oded , Herz Paul R. , Cronin Stephen B. , Lin Yu-Ming , Akinwande Akintunde I. , Dresselhaus Mildred S. 
Published: April 2011

AbstractA new approach for the use of porous alumina films as a template for nanofabrication is presented. In this process the porous films are prepared on silicon substrates, simplifying both the template fabrication and subsequent processing, and improving the quality of the films and their surfaces. Structural analysis of the film was carried out. Bismuth and bismuth telluride nanowires were prepared by pressure injection and electrochemical deposition, respectively, in alumina films 5-10 μ thick with parallel ordered pores 40 nm in diameter. The films were also patterned by lithography, offering new opportunities for area-selective anodization of non-planar structures. The new approach offers a straightforward method for the fabrication of arrays of nanostructures and their incorporation into electronic and optical devices.
Silicon Single Electron Transistors with Single and Multi Dot Characteristics
Authors: Savin Alexander , Manninen Antti , Kauranen Jari , Pekola Jukka , Prunnila Mika , Ahopelto Jouni , Kamp Martin , Emmerling Monika , Forchel Alfred 
Published: April 2011

AbstractSilicon single electron transistors (SET) with side gate have been fabricated on a heavily doped silicon-on-insulator (SOI) substrate. Samples demonstrate two types of characteristics: some of them demonstrate multiple dot behavior and one demonstrates single dot behavior in a wide temperature range. SETs demonstrate oscillations of drain-source current and changes in the width of the Coulomb blockade region with change of gate voltage at least up to 100 K. At temperature below 20 K long-term oscillations (relaxation) of source-drain current after switching the gate voltage has been observed in both multiple dot and single dot samples. Illumination affects both the characteristics of the SETs and the relaxation process. Telegraph noise has been observed in a definite range of source-drain and gate voltages.