bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thickness-dependent Crystallization Behavior of Phase Change Materials
Authors: Raoux Simone , Jordan-Sweet Jean L. , Kellock Andrew J. 
Published: April 2011

ABSTRACTWe have investigated the crystallization behavior of phase change materials as a function of their thickness. Thin films of variable thickness between 1 and 50nm of the phase change materials Ge2Sb2Te5 (GST), N-doped GST (N-GST), Ge15Sb85 (GeSb), Sb2Te, and Ag and In doped Sb2Te (AIST) were deposited by magnetron sputtering, and capped in situ by a 10nm thick Al2O3 film to prevent oxidation. The crystallization behavior of the films was studied using time-resolved X-ray diffraction. For each material we observed a constant crystallization temperature Tx that was comparable to bulk values for films thicker than 10 nm, and an increased Tx when the film thickness was reduced below 10 nm. The thinnest films that showed XRD peaks were 2 nm for GST and N-GST, 1.5 nm for Sb2Te and AgIn-Sb2Te, and 1.3 nm for GeSb. The observed increase in the phase transition temperature with reduced film thickness and the fact that very thin films still show clear phase change properties are indications that Phase Change Random Access Memory technology can be scaled down to several future technology nodes.
Recent Advances on the Modeling of Phase Change Materials and Devices
Authors: Lacaita Andrea Leonardo , Russo Ugo , Ielmini Daniele 
Published: April 2011

ABSTRACTAs non-volatile memory technology is approaching the 45nm generation node and in view of severe scaling limitations of conventional Flash, phase-change memory (PCM) is gaining momentum as a reference emerging memory. The high applicative interest in this new technologies asks not only for progress in the integration issues of the new storage concept, but, most importantly, for a significant improvement of the physical understanding of programming, reliability mechanisms and scalability of the new technology. This can only be possible by a detail study of microscopic processes in the chalcogenide material covering a wide range of physics, from electron transport in disordered media to self-heating effects, from solid-state nucleation and growth processes at the nanoscale.The presentation will review the most recent advances in the understanding and modeling of the programming and reliability mechanisms in chalcogenide-based PCM devices. Electro-thermal simulations of the programming behavior allows to understand the impact of cell geometry and active/electrode materials on the programming current, and to benchmark different scaling rules for future technology nodes. Cell reliability will be discussed with emphasis on the spontaneous crystallization kinetics in the amorphous chalcogenide material, on the acceleration laws to predict retention time at low temperature, and on the possible scaling limitations due to fast phase transition in amorphous chalcogenide nanoclusters/nanowires. An analytical model for nucleation and growth in the amorphous phase will be shown, allowing to draw guidelines for material engineering and reliability improvement. Other scaling-related reliability issues, such as statistical spread of crystallization times and structural relaxation of the amorphous phase, will be discussed.
Physico-chemical Characterization of Thin Oxide Films: Difficulties and Solutions
Authors: Conard Thierry , Vandervorst Wilfried 
Published: April 2011

ABSTRACTOxides have always been an integral part of semiconductor manufacturing both in front and back-end processing. With the necessary increase in performance, the demand on these oxides has been increasing leading to their (future) replacement by more complex materials, such as high-k's in gate oxide and metal gates. With the increasing material complexity, a thorough characterization of all aspects of these materials is necessary, covering, for instance, surfaces and interfaces, nucleation, growth, atomic structure, …This article focuses on the characterization of front-end oxides and their interfaces. It shows that detailed information can be achieved by sophisticated experimental techniques such as synchrotron radiation, high energy ERD or AtomProbe but that adequate sample preparation and/or analysis by a combination of more routinely available techniques may achieve similar results. This is shown through the study of three different systems/problems in the gate stack analysis. We will first focus on the determination of substrate surface preparation conditions before deposition and their influence on growth mode and the growth characteristics by different growth techniques (ALD, MOCVD, …). Second, we present the possibilities of compositional depth profiling of thin layers both with nuclear techniques and Angle-Resolved XPS. Finally, we will show that using conventional XPS and a combination of front and back-side analysis, the interface between high-k oxide and metal gates can be investigated. More examples of gate stack characterization can be found elsewhere
Effect of GaAs Surface Treatments on Lanthanum Silicate High-K Dielectric Gate Stack Properties
Authors: Lichtenwalner Daniel J , Suri Rahul , Misra Veena 
Published: April 2011

ABSTRACTThe properties of lanthanum silicate (LaSiOx) gate stacks on GaAs substrates have been examined, comparing different GaAs pretreatments; namely a) as-received, b) HCl-treated, and c) sulphur-treated. X-ray photoelectron spectroscopy of the As 3d, Ga 3d, and Ga 2p binding energy peaks were used to reveal the chemical nature of the stacks. After a 400 °C in situ anneal in 10−6 torr pO2, the LaSiOx chemically reduces the As oxides from the as-received GaAs, while Ga oxide species remain. HCl and S-treated GaAs similarly show no As oxides, and a much smaller degree of Ga oxides than the as-received case. The Ga-S bonding may be responsible for lowering the tendency towards Ga oxidation for the S-treated case. On p-type, Zn-doped GaAs, 3.0 nm lanthanum silicate films produce MOS device EOT values of 2.38 nm, 1.51 nm, and 1.37 nm, on as-received, HCl-treated, and S-treated substrates, respectively. The high EOT for the as-received GaAs corresponds to the thicker Ga oxide and elemental As at the interface. The decreases in both Ga oxide and elemental As at the interface of the S-treated stack appears to be related to it having the lowest EOT devices.
A-Site Distribution in La1−xSrxMnO3: a Computational Study
Authors: Jang Yun Hee , Gervais François , Lansac Yves 
Published: April 2011

ABSTRACTThe possibility of an A-site (La3+/Sr2+) ordering in a colossal magnetoresistance manganite (CMR) La3/4Sr1/4MnO3 was explored using molecular dynamics (MD) simulations with a newly developed force field (FF) and quantum mechanics (QM) calculations on the structures obtained from MD. The calculated degrees of stabilization (enthalpy gain) of various patterns of A-site ordering are not significant enough to overcome the accompanying entropy loss, supporting the random A-site distribution in La3/4Sr1/4MnO3. This approach combining MD and QM as well as the versatile FF developed in this study should be useful to investigate the structures and functions of magnetic tunnel junction devices involving mixed-valence manganites.
Microstructural Investigations of Hafnium Aluminum Oxide Films
Authors: Craciun Doina , Socol Gabriel , Axente Emanuel , Galca Aurelian-Catalin , Singh Rajiv , Craciun Valentin 
Published: April 2011

ABSTRACTThe crystalline structure, composition, chemical bonding and thermal stability of HfO2-Al2O3 mixtures deposited on Si using a combinatorial pulsed laser deposition technique were investigated. After deposition some films were annealed at temperatures from 850 to 950 °C for 6 or 12 minutes. Grazing incidence x-ray diffraction investigations were performed to asses the crystallinity and thermal stability of the annealed layers. Measurements of the Al to Hf ratios were performed using energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy. From simulations of the x-ray reflectivity and spectroscopic ellipsometry spectra the phase composition and thickness of the films was calculated and then the Al to Hf ratios. Al/Hf values of 1 and 8 were found to be necessary to block the crystallization of the films after anneals at 850 and 950 °C, respectively.
A New Technique to Measure and Deliver Low Levels of Water Vapor into Atmospheric and Vacuum Processes
Authors: Spiegelman Jeffrey 
Published: April 2011

ABSTRACTAs material processes move to the nanoscale, fine control of process chemistries becomes critical. Atomic Layer Deposition, Chemical Vacuum Deposition, and Selective Gate Oxidation, as well as fabrication of Carbon Nanotubes all need water vapor from 50 sccm (40mg/min) to below 1 sccm ( 0.8 mg/min). Water vapor can be used for oxidation, cleaning and annealing of the nanoscale devices and thin films.At 0.8 mg/min, flow control of liquid water with a mechanical pump is difficult without pulsation. Because water is liquid at room temperature, a standard thermal mass flow controller for gas cannot be used. Instead bubblers are used. However, they do not provide consistent or repeatable delivery. They are affected by gas and liquid temperature, relative pressures as well as gas velocity, liquid height, thermal droop, and contamination build up.RASIRC® has developed a new pervaporation device that selectively allows water to diffuse into a carrier gas stream. The liquid water never directly contacts the carrier gas, allowing for independent liquid and gas pressures. A nonporous, hydrophilic membrane provides very rapid diffusion of water vapor into the carrier gas stream. This allows for precise amounts of water vapor to be added to the carrier gas based solely on relative vapor pressures.To validate the performance of the device at very low flow rates into both atmosphere and vacuum process pressures, a heated humidity probe was used. This device was able to measure flow rates of 1 to 200 sccm in both vacuum and atmospheric pressure. The experimental results were compared with the expected theoretical dew point to validate the procedure. The humidity probe was used to measure both long term stability of the device and the instantaneous response time. Experimental results were compared to the expected time needed to change the water vapor concentration in the test volume.
Numerical Simulation of the Growth of ZnO Nanostructures in a Tube Furnace by Physical Vapour Deposition
Authors: Dalal Sharvari , Gallo Federico , Flewitt Andrew J , Milne William I 
Published: April 2011

ABSTRACTZinc oxide is a versatile II-VI naturally n-type semiconductor that exhibits piezoelectric properties. By controlling the growth kinetics during a simple carbothermal reduction process a wide range of 1D nanostructures such as nanowires, nanobelts, and nanotetrapods have been synthesized. The driving force for the nanostructure growth is the Zn vapour supersaturation and supply rate which, if known, can be used to predict and explain the type of crystal structure that results. A model which attempts to determine the Zn vapour concentration as a function of position in the growth furnace is described. A numerical simulation package, COMSOL, was used to simultaneously model the effects of fluid flow, diffusion and heat transfer in a tube furnace made specifically for ZnO nanostructure growth. Parameters such as the temperature, pressure, and flow rate are used as inputs to the model to show the effect that each one has on the Zn concentration profile. An experimental parametric study of ZnO nanostructure growth was also conducted and compared to the model predictions for the Zn concentration in the tube.
Effect of Inactivated Dopants Clusters and Processing Parameters on Electrical Properties of Indium Tin Oxide on Plastic Substrates
Authors: Han Hauk , Lewis Jay , Alford Terry 
Published: April 2011

ABSTRACTIndium tin oxide (ITO) thin films were deposited on polyethylene napthalate (PEN) by rf sputtering using different rf powers (60 and 120 W) and at different substrate temperatures (room temperature and 100 °C). Rutherford backscattering spectrometry was used to determine the oxygen content in the films. Hall effect measurements were used to evaluate the electrical properties. In this paper the influence of defect structure, sputtering conditions, and the effect of annealing on the electrical and optical properties of ITO on PEN have been investigated. Electrical properties such as carrier concentration, mobility, and resistivity of the ITO films varied with rf power and substrate temperature. The electricalproperties of the films changed after annealing in air. This study also describes how the as-deposited amorphous ITO changes from amorphous to crystalline as a result of heat treatment, and investigates the effects of Sn defect clustering on electrical and optical properties of the ITO films.
High-mobility Nanocrystalline Indium Oxide TFTs with Silicon Nitride Gate Dielectric
Authors: Wang Kai , Vygranenko Yuriy , Nathan Arokia 
Published: April 2011

ABSTRACTA variety of oxide semiconductors such as ZnO, SnO2, In2O3 and other multi-component oxide compounds have been successfully used as channel materials in thin-film transistors (TFTs). Compared with amorphous silicon and organic semiconductor counterparts, the unique features of these materials include good performance, stability, low temperature processing, and transparency. In this work, we report on room-temperature deposition of indium oxide thin films by reactive ion beam assisted evaporation (IBAE) and their application to TFTs. By modifying the deposition parameters, nanocrystalline indium oxide (nc-In2O3) with an average grain size of 12 nm was achieved. TFTs with IBAE nc-In2O3 channel and silicon nitride gate dielectric deposited by conventional plasma-enhanced chemical vapour deposition (PECVD), were fabricated. The n-channel TFT has a threshold voltage of ∼2.5 V, a field-effect mobility of ∼32 cm2/Vs, along with an ON/OFF current ratio of ∼108, and a sub-threshold slope of 2.5 V/decade. The TFT reported here has one of the best performance characteristics in terms of device mobility, ON/OFF current ratio, and OFF current, using conventional, and large area foundry-compatible PECVD gate dielectrics. The device performance coupled with its low-temperature processing makes IBAE-derived nc-In2O3 TFT a promising candidate for active matrix flat panel displays.
Ion Implantation Through Thin Silicon Dioxide Layers for Si-based Solid-State Quantum Computer Device Development
Authors: McCallum Jeffrey , Dunn Michael L. , Gauja Eric 
Published: April 2011

ABSTRACTIon implantation doping of Si through an SiO2 overlayer is of interest for fabrication of a range of devices on the pathway to development of a solid–state quantum computer (SSQC). The fabrication requirements of devices based on the Kane architecture typically involve implantation through a pre-existing thin device–quality thermal oxide at low fluences ∼1011 cm−2 and ion energies in the range 10 – 20 keV. Here we present results from a deep level transient spectroscopy studies of ion–implanted MOS capacitors in which interface–trap densities have been measured in as–grown and H–passivated thermal oxides and in ion implanted and rapid–thermally processed devices. For thin oxides of 5nm or less and low ion fluences we find that implantation does not significantly increase interface trap densities and somewhat surprisingly that it can even be beneficial when the interface trap density is abnormally high, (∼ 1 × 1011cm−2.eV−1) in the as-grown oxide.
Microstrcutural Evolution of SiC Fibre Embedded AA6061 Matrix Induced by Ultrasonic Consolidation
Authors: Zhu Z. , Wynne B.P , Ghassemieh Elaheh 
Published: April 2011

ABSTRACTUltrasonic consolidation (UC) uses high frequency (20-40KHz) mechanical vibrations to produce a solid-state metallurgical bond (weld) between metal foils. UC as a novel layered manufacturing technique is used in this research to embed reinforcing members such as silicon carbide fibers into the aluminium alloy 6061's matrices. It is known that UC induce volume and surface effect in the material it is acting on. Both effects are employed in embedding active/passive elements in the metal matrix. Whilst the process and the two effects are used and identified at macro level, what is happening at micro level is unknown and hardly studied. In this research we are investigating the phenomena occurring in the microstructure of the parts during UC process to obtain better understanding about how and why the process works.In this research, high-resolution electron backscatter diffraction is used to study the effects of the UC process on the evolution of microstructure in AA6061 with and without fibre elements.The inverse pole figures (IPF), pole figures (PF) and the correlated misorientation angle distribution of the mentioned samples are obtained. The characteristics of the crystallographic orientation, the grain structure and the grain boundary are analysed to find the effect of ultrasonic vibration and embedding fibre on the microstructure and texture of the bond. The ultrasonic vibration will lead to exceptional refinement of grains to a micron level along the bond area and affect the crystallographic orientation. Additional plastic flow occurs around the fibre which leads to the fibre embedding.
Efficient High Power ns Pulsed Fiber Laser for Lidar and Laser Communications
Authors: Liu Jian 
Published: April 2011

AbstractResearch results on high energy/power ns pulsed fiber lasers are discussed in this paper. Modulation schemes for a seed laser in getting various optical waveforms, high power operation of fiber amplifiers, nonlinearity mitigation in high power fiber lasers, and trade-offs have been addressed. It shows experimentally that ns pulses can be achieved by direct modulation of a semiconductor seed laser and an energy level of sub-mJ were demonstrated. 23 % wall plug efficiency was achieved for a compact laser module.
Simplified Homodyne Detection for Linear FM Lidar
Authors: Adany Peter , Allen Chris , Hui Rongqing 
Published: April 2011

ABSTRACTA fiber based lidar system is developed which simplifies the processing of linear FM pulses by using a modulated local oscillator power in the coherent detector. Experiments were conducted on lidar systems with direct, heterodyne and simplified homodyne detection to compare receiver sensitivity. A field experiment using the homodyne system verified the sensitivity estimation on a building target at 370-m range.
Surface Modification of ZrO2 Nanoparticles as Functional Component in Optical Nanocomposite Devices
Authors: Tsedev Ninjbadgar , Garnweitner Georg 
Published: April 2011

ABSTRACTWe have recently shown the successful synthesis of zirconia nanoparticles that can be optimized for use in volume phase holography by a post-functionalization surface treatment. Here, we present further investigations on the surface modification treatment with the aim of providing tools to tailor the nanoparticle compatibility to the photocurable organic matrix. Highly crystalline ZrO2 nanoparticles with a mean diameter of 5nm are synthesized in multigram yield through a one-pot solvothermal reaction of zirconium (IV) n-propoxide in benzyl alcohol. It is shown that the yield of the ZrO2 nanoparticles and stability of the nanoparticle dispersions are strongly dependent on the synthesis temperature. Post-synthetic surface modification of ZrO2 nanoparticles using several aliphatic ligands with different surface binding groups such as carboxylate (-COO−), amine (−NH2), phosphate (−PO4) and methoxysilane (−SiOCH3) was performed in order to compare the binding ability of these functional groups to the nanoparticle surface and therefore provide a new rational approach for nanoparticle stabilization with organic ligands.
Fabrication of Nano-Structured Gold Arrays by Guided Self-assembly for Plasmonics
Authors: Li Xiaoli V. , Milhano Clelia A. , Cole Robin M. , Bartlett Phil N. , Baumberg Jeremy J. , de Groot Cornelis H. 
Published: April 2011

ABSTRACTGold inverse spherical nanoscale voids have been fabricated in linear arrays for directional plasmon measurements in the visible spectral range. We show that by KOH anisotropic etching in Si, we are able to make V-grooves in which latex spheres of the order of 500 nm self-assemble with largely defect-free cubic symmetry. Both single layer and multilayer assembly in a face-centered close-packed (FCC) lattice can be achieved by varying the width of the trenches. This template is subsequently used for electrodeposition of gold to create the inverse spherical nanovoids.
Structural Dynamics of a Single Photoreceptor Protein Molecule Monitored With Surface-Enhanced Raman Scattering Substrates
Authors: Singhal Kushagra , Bhatt Karthik , Kang Zhouyang , Hoff Wouter , Xie Aihua , Kalkan A. Kaan 
Published: April 2011

ABSTRACTPhotoactive yellow protein (PYP) is a small cytosolic photoreceptor that actuates the negative phototactic response in its host organism Halorhodospira halophila. It has an optical absorption maximum at 446 nm (blue light). We report an initial study of the photocycle of PYP at the single molecule level using “high enhancement factor” surface-enhanced Raman scattering (SERS)-active nanostructures with 514 nm laser excitation. The SERS-active “nanometal-on-semiconductor” structures are prepared employing a redox technique on thin germanium films, coated on glass slides. Single molecule spectra are observed in terms of sudden appearance of discernable Raman peaks with spectral fluctuations. The single molecule spectra capture protonation, photo-isomerization, and H-bond breaking - the steps that are instrumental in the photocycle of PYP. This is indicative of single PYP molecules diffusing to high-enhancement-factor SERS sites, and undergoing photo-cycle under 514 nm excitation.
Molecular-level Manipulation Technology for Low-k Dielectrics Controlling the Physical and Chemical Structures toward 32nm-node BEOLs
Authors: Hayashi Yoshihiro 
Published: April 2011

ABSTRACTLow-k materials in advanced interconnect modules are required not only to lower the parasitic capacitances, but also to have mechanical stability with damage-less interfaces. By plasma-polymerization (PP) process using ring-type siloxane precursor, a new self-organized porous SiOCH film is developed with preserving the original hexagonal silica-backbone structure, thus so called as a molecular-pore-stack (MPS) SiOCH film. The hydrocarbon-rich MPS film has high endurance to the process damages. A density-modulated MPS film is obtained with reinforced interfaces by plasma co-polymerization (PcP) process using not only the ring-type but also linear-type siloxane. Furthermore, an ultimate full low-k module with low-k silica-amorphous-carbon composite (SACC) cap, instead of high-k SiCN, is also obtained simply by the one-step deposition scheme. The modulated PcP process and the sophisticated molecular design of the precursor siloxane provides scaled-down interconnect modules with good mechanical strength and excellent dielectric reliability at a low manufacturing cost, applicable for 45/32/22nm-nodes ULSIs.
UV Curing Effects of Low-k Materials under Reactive Conditions
Authors: Moore Darren , Waldfried Carlo , Sakthivel Palani , Escorcia Orlando 
Published: April 2011

ABSTRACTThis work describes the effect of addition of O2 and NH3 to the N2 ambient used during the UV cure process of low-k materials. The effects of O2 give an acceleration of the cure process, resulting in increased film modulus and shrinkage. The use of NH3 resulted in a retardation of UV cure, explained by the higher absorption cross section of NH3 at the wavelengths used.