bluuebunny/crossref_metadata_2025_split huggingface dataset:
Millimetre and Submillimetre Wave Components for Future Diagnostic Instrumentation
Authors: Mann Chris 
Published: April 2011

ABSTRACTContrary to common belief the technology associated with components and systems for operation in the millimetre and submillimetre or Terahertz (THz) region of the electromagnetic spectrum is mature. However, it has largely been developed for use in the fields of radio astronomy and remote sensing, two areas where size and cost have not been the driving issues. This is changing, both fields now have ambitious plans to put large complex systems into space in experiments such as NASA'a EOS MLS and ESA'a FIRST amongst others. Also, ground based systems such as ALMA are planned where the total number of receivers exceeds 1000. For such instruments cost and size now becomes important. Taking these factors into account for the last decade or so there has been a concerted drive towards smaller and cheaper instrumentation. Initially, the use of quasi-optical systems was implemented in place of waveguide mainly because of its prohibitive manufacturing cost. Quas-ioptical systems are still being developed but waveguide has recently seen a revival due to the use of new micromachining techniques for its fabrication. Planar or integrated circuitry mounted in waveguide has now demonstrated state of the art performance to 2.5THz. Combining these factors means that for the first time the cost of manufacturing high performance RF electronics in the THz region has finally become affordable thereby making it available to new areas of research, material science is one of many. This paper describes how new devices and systems may be implemented to realise the basic building blocks of such instrumentation, namely, detectors and sources.
The Effects of Width Transitions on the Reliability of Interconnects
Authors: Hau-Riege C. S. , Thompson C.V. , Marieb T.N. 
Published: April 2011

AbstractExperimental and modeling studies of Al-based interconnects with narrow-to-wide transitions show that the width transition is a site of atomic flux divergence due to the discontinuity in diffusivities between the narrow and wide segments, which have different microstructures. Lifetimes have been experimentally determined for populations of lines with width transitions, which have varying line-width ratios and varying locations of the width transitions with respect to the line end. The electromigration failure rate is increased as the width-transition is moved closer to the electron-source via. Correlation of the effects width transitions on lifetimes allows determination of the critical stress range for void -nucleation failure, which was found to be 600 ± 108 MPa.
Photo-Induced Growth of Low Dielectric Constant Porous Silica Film at Room Temperature
Authors: Zhang Jun-Ying , Boyd Ian W. 
Published: April 2011

AbstractWe report low temperature (25-200°C) photo-assisted sol-gel processing for the formation of porous silicon dioxide films on Si (100) substrates using 172 nm radiation from an excimer lamp. The effects of substrate temperature and irriadation time on the properties of the films formed have been studied using ellipsometry, Fourier transform infrared spectroscopy (FTIR), and electrical measurements. The FTIR spectra revealed the presence of a Si-O-Si stretching vibration peak at 1070 cm-1 after UV irradiation at 200°C. This is similar to that recorded for oxides grown by thermally oxidation of silicon at temperatures between 600-1000°C. Capacitance measurements indicated that the dielectric constant values of the films, found to be between 1.7-3.3, strongly depended on the substrate temperature during irradiation. Dielectric constant values as low as 1.7 were readily achievable at room temperature. These results show that the photochemical induced effects initiated by the UV radiation enable both reduced processing times and reduced processing temperatures to be used.
Microstructural Analysis of Copper Interconnections Using Picosecond Ultrasonics
Authors: Harper James M.E. , Malhotra Sandra G. , Cabral Cyril , Lavoie Christian , Hao Hsin-Yi , Homsi Wadih , Maris Humphrey J. 
Published: April 2011

AbstractWe demonstrate that picosecond ultrasonics provides detailed information on the structure and properties of patterned arrays of copper fine lines used in silicon chip interconnections. In this method, the sample surface is momentarily heated several °C using a pump laser beam, and the transient change in the optical reflectivity is measured by a probe laser beam. Measurements of the optical reflectivity are made on time scales ranging from picoseconds to nanoseconds, revealing information on electronic, acoustic and thermal properties. We have applied this method to samples consisting of copper line arrays of 0.4 µm linewidth, 0.65 µm pitch and 0.35 µm depth in SiO2 on silicon wafers. For comparison, we examined the picosecond ultrasonic response of 200 nm-thick blanket copper thin films. The patterned Cu lines are found to have long-term oscillations at frequencies of 4.39 and 8.29 GHz with lifetimes at least 10 times longer than the oscillations in the blanket Cu film. A two-dimensional mechanical analysis was developed which uses as input parameters the dimensions and sound velocities of the materials in the sample, and finds the normal mode frequencies and displacements. The main vibrational modes are identified and described for the patterned lines, and the simulations confirm that the lowest frequency modes have very small damping coefficients. Also, the time-dependent signal is shown to reveal details of interface layers and integrity of the copper/liner interface.
Volatile Liquid Precursors for the Chemical Vapor Deposition (CVD) of Thin Films Containing Tungsten
Authors: Gordon Roy G. , Barry Seán , Broomhall-Dillard Randy N. R. , Wagner Valerie A. , Wang Ying 
Published: April 2011

AbstractA new CVD process is described for depositing conformal layers containing tungsten, tungsten nitride or tungsten oxide. A film of tungsten metal is deposited by vaporizing liquid tungsten(0) pentacarbonyl 1-methylbutylisonitrile and passing the vapors over a surface heated to 400 to 500 °C. This process can be used to form gate electrodes compatible with ultrathin dielectric layers. Tungsten nitride films are deposited by combining ammonia gas with this tungsten-containing vapor and using substrates at temperatures of 250 to 400 °C. Tungsten nitride can act as a barrier to diffusion of copper in microelectronic circuits. Tungsten oxide films are deposited by adding oxygen gas to the tungsten-containing vapor and using substrates at temperatures of 200 to 300 °C. These tungsten oxide films can be used as part of electrochromic windows, mirrors or displays. Physical properties of several related liquid tungsten compounds are described. These low-viscosity liquids are stable to air and water. These new compounds have a number of advantages over tungsten-containing CVD precursors used previously.
A Comparative Study of Ti/Low-k HSQ (Hydrogen Silsesquioxane) and Ti/TEOS (Tetraethylorthosilicate) Structures at Elevated Temperatures
Authors: Zeng Yuxiao , Chen Linghui , Alford T. L. 
Published: April 2011

AbstractFor the benefit of reducing capacitance in multilevel interconnect technology, low-k dielectric HSQ (hydrogen silsesquioxane) has been used as a gapfill material in Al-metallization- based non-etchback embedded scheme. The vias are consequently fabricated through the HSQ layer followed by W plug deposition. In order to reduce the extent of via poisoning and achieve good W/Al contact, thin Ti/TiN stack films are typically deposited before via plug deposition. In this case, HSQ makes direct contact with the Ti layer. The reliability of the Ti/HSQ structures at elevated temperatures has been systematically studied in this work by using a variety of techniques. These results are also compared with those from Ti/TEOS (Tetraethylorthosilicate) structure, where TEOS is a conventional intra-metal dielectric. When the temperature is below 550 °C, a significant number of oxygen atoms are observed to diffuse into the titanium layer. The primary source of oxygen is believed to come from the HSQ film. When the temperature is above 550 °C, HSQ starts to react with Ti. At 700 °C, a TiO/Ti5Si3/HSQ stack structure forms. The Ti/HSQ system exhibits a higher reactivity than that of the Ti/TEOS system.
High Density Plasma Silicon Carbide as a Barrier/Etch Stop Film for Copper Damascene Interconnects
Authors: M'Saad Hichem , Cho Seon-Mee , Vellaikal Manoj , Li Zhuang 
Published: April 2011

AbstractA low κ dielectric barrier/etch stop has been developed for use in copper damascene application. The film is deposited using methane, silane and argon as precursors in a HDP-CVD reactor. The film has a dielectric constant of 4.2 which is lower than the dielectric constant of conventional SiC or plasma silicon nitride (>7). Film characterization including physical, electrical, adhesion to ILD films, etch selectivity, and copper diffusion barrier properties show that this film is a better barrier than silicon nitride for low κ copper damascene interconnects. This film consists of a refractive index in the range of 1.7 to 1.8, a compressive stress of 1.0-1.5×109 dynes/cm2, and a leakage current of 5.0×10−10 A/cm2 at 1 MV/cm. When integrated in-situ with HDP-FSG, an effective dielectric constant of 3.5 can be achieved.
High-Jc YBCO Conductors Fabricated By Magnetron Deposition
Authors: Savvides N. , Gnanarajan S. , Herrmann J. , Thorley A. , Katsaros A. , Molodyk A. 
Published: April 2011

AbstractSuperconducting YBCO/YSZ/Hastelloy tapes or coated conductors were fabricated by combining ion beam assisted deposition (ILBAD) and magnetron sputtering techniques. The degree of biaxial alignment of the YSZ buffer layers and the epitaxial YBCO films was determined from x-ray pole figures and ø-scans. The best YSZ buffer layers had FWHFM δø= 7°- 10°. The corresponding YBCO tapes achieved a similar degree of biaxial alignment and high critical current density, Jc(77K,0T) = (0.9 – l.25)×106 A cm−2.
Kinetic Monte Carlo Simulation of Dynamic Phenomena in thin Film Growth
Authors: Gallivan M. A. , Murray R. M. , Goodwin D. G. 
Published: April 2011

AbstractIn this paper we describe the response of a Kinetic Monte Carlo model to time-varying growth conditions. We vary temperature and partial pressure sinusoidally and identify behavior typical of low-dimensional nonlinear systems. In particular, the frequency content of the roughness response is sensitive to the presence of steps in the surface.
Localized Excimer Laser Energy Modulation in the Crystallization Of Poly-Si Film On Stepped Substrate
Authors: Park Kee-Chan , Jung Sang-Hoon , Nam Woo-Jin , Han Min-Koo 
Published: April 2011

AbstractAnew excimer laser recrystallization method of a-Si film to increase the grain size of poly-Si film has been proposed. Excimer laser energy was locally modulated by being irradiated on stepped substrate with 500 nm deep trench on which a-Si film was deposited. Fairly large poly-Si grains (over 1 µm) were obtained due to lateral thermal gradient which resulted from the laser energy difference on the vertical wall and on the horizontal bottom plane of the trench without altering laser energy density elaborately.
From the Solid-Fluid Interfacial Structure to Genuine Morphology of Crystals
Authors: Liu X.Y. 
Published: April 2011

ABSTRACTCrystals reveal a large variety of shapes, depending on the chemical composition and the structure of crystals, and the growth conditions. To predict precisely the growth morphology of crystals remains a challenging issue for both academia and industry. In this paper, the principles for predicting the growth morphology of crystals based on the best available theories are highlighted and demonstrated.
Modeling of Interface Scattering Effects during Light Emission from Thin Film Phosphors for Field Emission Displays
Authors: Cho K. G. , Singh R. K. , Chen Z. , Kumar D. , Holloway P. H. 
Published: April 2011

ABSTRACTIt has been experimentally shown that the light trapping due to internal reflection from a smooth surface is reduced as the surface becomes progressively rougher. Although this phenomenon is qualitatively understood well, there has been a lack of detailed analysis of the scattering phenomenon which affects the light emission from thin film phosphors (TFPs). Factors which affect the light emission from the TFPs include electron beam-solid interaction (EBSI), film thickness, microstructure, surface recombination rate, surface roughness, and substrate (thus the interface formed). In many cases, they cannot be varied independently and thus making it difficult to interpret the results quantitatively. Furthermore, as the surface roughness is smaller or same as the wavelength of the emitted light, classical theories based on rectilinear propagation of the light cannot be used without gross simplification. A new theoretical model has been developed by incorporating diffraction scattering at the various interfaces and the factors mentioned above. The model provides an integrated solution to explain the cathodoluminescence (CL) properties of TFPs for field emission displays (FEDs).
Stability in Electrical Properties of Ultra Thin Tin Oxide Films
Authors: Matsui Yuji , Yamamoto Yuichi , Takeda Satoshi 
Published: April 2011

ABSTRACTTin Oxide films of less than 30nm in thickness were developed as transparent conductive electrodes. The films were deposited onto glass substrates by APCVD. Fluorine was used as a doping component. Stability to heat treatments in air at more than 500• was studied. Carrier concentration decreased and Hall mobility increased by the heat treatments. It was found relations between carrier concentration and mobility exhibited an exponential relation in extremely low fluorine concentration films. The exponent of the relation was close to −1.5. Resistivity decreased for the films, while it increased for films with high fluorine concentration. It was also found migration of sodium from the substrates into the films increased with increase of fluorine concentration in the films. Results suggest the sodium migration would affect grain growth and electrical properties of the films.
Nitride Phosphors for Low Voltage Cathodoluminescence Devices
Authors: Kanie Hisashi , Kawano Takahiro , Sugimoto Kose , Kawai Ryoji 
Published: April 2011

ABSTRACTUndoped and Zn doped InGaN microcrystals were synthesized by a two-step method. The InGaN microcrystals have a wurtzite structure and brownish body color. The InGaN samples prepared at 900°C did not contain a metal In phase. The InGaN:Zn microcrystals showed blue photoluminescence (PL) at 77K different from that of GaN:Zn. Reflectivity and photoluminescence excitation (PLE) measurement showed that the fundamental absorption edge of the InGaN:Zn phosphors is 3.47 eV, which implies that the In content in the InGaN:Zn phosphors is less than 0.2%. GaN:Zn and InGaN:Zn showed a Zn related PLE peak at 3.34 eV. InGaN and InGaN:Zn showed an In related PLE peak at 3.14 eV. When the InGaN:Zn samples were selectively excited at 3.15 eV, an In-related emission band centered at 2.2 eV emerged. The InGaN:Zn phosphors mounted on vacuum fluorescent displays (VFDs) showed room-temperature blue cathodoluminescence (CL) and the CL peak shifted slightly toward the low energy compared to that of the GaN:Zn phosphors because of the superimposed In related band. The InGaN:Zn phosphors had a luminance of 50 cd/m2 and a luminance efficiency of 0.03 lm/W at an anode voltage of 50 V.
Excimer Laser Crystallisation of Poly-Si TFTs for AMLCDs
Authors: Brotherton S D , McCulloch D J , Gowers J P , Ayres J R , Fisher C A , Rohlfing F W 
Published: April 2011

ABSTRACTThere is interest in reducing the shot number in the poly-Si laser crystallisation process in order to improve its throughput. Two distinct shot number dependent effects have been identified, which are both laser intensity dependent. The critical laser energy density is that which causes full film melt-through, and the major issue occurs at energies greater than this, where there is a considerable degradation in device uniformity with reducing shot number. The cause of this is non-uniform recovery of the full-melt-through fine grain poly-Si, and it is demonstrated that by extending the trailing edge of the beam, the material uniformity at reduced shot number can be improved. For energies less than this, the issue is not so much uniformity, as a general degradation in overall device properties with reducing shot number, which has been correlated with reducing grain size.In more demanding, future applications (such as system-on-panel), it will be necessary to improve circuit performance and approach that of current MOSFET devices. This will require short channel, self-aligned (SA) TFTs, and some of the issues with this architecture, particularly lateral ion implantation damage beneath the gate edge and drain field relief are discussed.
A Novel Approach for True Work Function Determination of Electron-Emissive Materials by Combined Kelvin Probe and Photoelectric Effect Measurements
Authors: Lägel Bert , Baikie Iain D. , Dirscherl Konrad , Petermann Uwe 
Published: April 2011

ABSTRACTFor the development of new electron-emissive materials knowledge of the work function Φ and changes in Φ is of particular interest. Among the various methods, the ultra-high vacuum (UHV) compatible scanning Kelvin Probe has been proven to be a superior technique to measure work function changes due to e.g. UHV cleaning processes, chemical contamination, thermal processing etc. with high accuracy (<1meV).The Kelvin Probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (Φtip) is unknown.Here, we present a novel approach to measure Φtip with the Kelvin Probe via the photoelectric effect, where a Gd foil is used as the photoelectron source. This method thus provides the true work function of the sample surface with an accuracy of approx. 50meV. We demonstrate the application of the technique by in situ work function measurements on evaporated layers of the low work function material LaB6 on a Re substrate and follow the changes in Φ of LaB6 due to the surface adsorption of residual gas molecules. Thus, the extended Kelvin Probe method provides an excellent tool to characterise and monitor the stability of low work function surfaces.
Study on Depletion Mode Operation of Protruding-Tip Field Emitter Triodes
Authors: Luo Y-C. , Shibata M. , Okada H. , Onnagawa H. 
Published: April 2011

ABSTRACTElectrical characteristics of Spindt-type Molybdenum (Mo) field emitter triode devices with varied emitter tip-height have been studied based on device modeling and experiment. Potential and electric field distributions with varied the emitter tip-height has been simulated. It is observed that the electric field of the top of the higher emitter tip was strongly affected with the anode-gate distance and the anode voltage compared to conventional field emitter triode device. Experimental results with varied different tip-height were in good agreement with that of calculated results. We present the possibility of “depletion mode” field emitter triode device.
Capacitance and Transient Photocapacitance Studies of Tetrahedral Amorphous Carbon
Authors: Palinginis Kimon C. , Ilie A. , Milne W.I. , Cohen J. David 
Published: April 2011

ABSTRACTWe have applied junction capacitance and transient photocapacitance measurements to undoped tetrahedral amorphous carbon (ta-C)/silicon carbide (SiC) heterostructures to deduce defect densities and defect distributions in ta-C. The junction capacitance measurements show two thermally activated processes. One can be related to the activation of carriers out of defects at the ta-C/SiC interface while the other one with an activation energy of 0.36eV is an intrinsic property of the ta-C. The defect density at the ta-C/SiC interface is estimated to be roughly 9 ± 2 × 109 cm−2. The transient photocapacitance measurements have allowed us to observe the broader band tail of ta-C, giving a value (Urbach energy) of 230meV.
Formation of Carbon Nanotube by using RF plasma CVD equipment from Acetylene and Hydrogen gases
Authors: Show Y. , Matsukawa T. , Iwase M. , Izumi T. 
Published: April 2011

AbstractThe carbon nanotubes were grown on the round Ni particles at the growth temperature below 60 °C by the radio frequency plasma CVD equipment from the acetylene and the hydrogen gases. For the low growth of the carbon nanotubes, the acetylene concentration in the hydrogen gas was essential parameter. In the case of the high acetylene concentration above 30 %, the cauliflower-like carbon film was grown. On the other hand, the low acetylene concentration of 10 % realized the low temperature growth of the carbon nanotubes.
Fabrication of Freestanding Carbon Nanotube Arrays in Large Scale
Authors: Huang Z.P. , Moser J. , Sennett M. , Gibson H. , Naughton M.J. , Wen J.G. , Ren Z.F. 
Published: April 2011

AbstractWe have successfully fabricated many freestanding carbon nanotube arrays on silicon substrates. Two sizes of nickel dot arrays have been made by E-beam lithography. It has been found that the size of the carbon nanotubes is closely related to the size of the dot. Compared with our previous report on diameters of about 300 –400 nm, much thinner carbon nanotubes of 100 –150 nm have been made. With even smaller dots, it is expected that even thinner nanotubes of a few tens of nanometers could be made. The nanotube height is controlled by the growth time and nanotube uniformity has been greatly improved by introduction of a two-phase process of nucleation and growth.
Reinforcement Mechanisms in Polymer Nanotube Composites: Simulated Non-Bonded and Cross-Linked Systems
Authors: Frankland S. J. V. , Caglar A. , Brenner D. W. , Griebel M. 
Published: April 2011

AbstractA summary of three simulations related to the issue of load transfer in carbon nanotube/polymer composites is given. Each simulation considers a (10,10) nanotube in a polyethylene matrix modeled with either a united-atom or fully-atomic polyethylene representation. The first simulation uses molecular dynamics to model a 100 nm nanotube in polyethylene in which the nanotube and matrix interact through weak non-bonded interactions. No permanent stress transfer is observed for this system. The second simulation estimates the shear yield strength for the nanotube in each of the model polyethylene matrices. The third simulation addresses a chemically functionalized nanotube in which there are cross-links between the nanotube and matrix. The results indicate that the cross-linked system has an enhanced shear yield strength of one to two orders of magnitude larger than the non-bonded composites.