bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of Ultra-Thin Thermal Silicon Nitride
Authors: Buchheit Katherine M. , Takeuchi Hideki , King Tsu-Jae 
Published: April 2011

ABSTRACTGrowth behavior and film properties of ultra-thin Si3N4 layers formed by RTN (rapid thermal nitridation) were characterized. The self-limiting growth characteristics of the RTN process are appealing for precise thickness control in the range of 0.5–2.5nm. From SCA (surface charge analysis), the existence of negative fixed charge and electron traps in nitrides was found, in contrast to positive fixed charge and hole traps in oxides, and improvements in interface properties were seen after high temperature annealing. From annealing ambient dependences, the physical origin of the electron traps is likely N-H bonds in the nitride films. AFM (atomic force microscopy) analysis revealed that an atomically flat nitride surface is obtained by post-nitridation spike annealing, but a longer anneal leads to a rougher surface. Effectiveness of ultra-thin nitride barriers against boron penetration from a p+ poly-Si gate was also confirmed by SRA (spreading resistance analysis).
Study of HfAlOx Films Deposited by Layer-by-Layer Growth for CMOS High-k Gate Dielectrics
Authors: Toriumi Akira , Nabatame Toshihide , Horikawa Tsuyoshi 
Published: April 2011

ABSTRACTWe have investigated ternary metal oxide films for high-k gate dielectrics by using a layer-by-layer deposition & annealing method so as to keep the dielectric constant of the film high with no crystallization. HfAlOx films have been prepared by alternating deposition of HfO2 and Al2O3 layers, where it is a key for the improvement of the film quality to understand the intermixing process between two layers by thermal treatments. So, we first discuss the atomic diffusion and structural change of the HfO2/Al2O3 “superlattice” film as a function of the annealing temperature by changing the Hf/Al ratio. In a typical case of the film with HfOx/AlOx=3Å/9Å cycle, a clear superlattice peak is observed below 750 °C by XRD. Above 850 °C, a different type of crystalline structure with no superlattice peaks is observed. These results indicate that the intermixing in HfO2/Al2O3 (3Å/9Å) films occurs between 750 and 850 °C. The intermixing onset temperature increases with increasing Al content in Hf/Al ratio.To further increase the crystallization temperature, nitrogen incorporation into the film is considered, and effects of the nitrogen incorporation into HfAlOx films are studied from the structural and electrical viewpoints. The results indicate that there is a tradeoff between crystallization restriction and leakage current degradation for the nitrogen incorporation into HfAlOx films.
Low-temperature growth of HfO2 dielectric layers by Plasma-Enhanced CVD
Authors: Losurdo M. , Giangregorio M.M. , Luchena M. , Capezzuto P. , Bruno G. , Barreca D. , Gasparotto A. , Tondello E. 
Published: April 2011

ABSTRACTHfO2 dielectric layers have been grown on p -type Si(100) by plasma enhanced chemical vapor deposition (PE-CVD), using Ar-O2 plasmas and hafnium(IV) tetra-t -butoxide as precursors. In-situ control of the plasma phase is carried out by optical emission spectroscopy (OES) and quadrupolar mass spectrometry (QMS).Structural and optical properties of the HfO2 layers and of the HfO2/Si interface are investigated by spectroscopic ellipsometry (SE) in the photon energy range 1.5–6.0 eV‥ SE data are corroborated by results obtained from glancing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS).The effect of the substrate temperature (RT-250°C) and precursor flow on the thickness of interfacial SiO2 layer and on the HfO2 microstructure is investigated. The growth dynamics of HfO2 film and SiO2 interface layer is also discussed.
Oxide-Semiconductor Interface Characterization Using Kelvin Probe-AFM In Combination With Corona-Charge Deposition
Authors: Lägel Bert , Ayala Maria D. , Oborina Elena , Schlaf Rudy 
Published: April 2011

ABSTRACTCorona charge deposition methods in combination with spatially resolved surface potential measurements have become a standard tool for Si oxide quality monitoring. Based on this technique oxide-semiconductor interface parameters such as surface barrier height, oxide thickness and oxide charge density can now be monitored in-line with commercially available devices. The ongoing downscaling of integrated circuits into the sub-100 nm regime makes the development of high resolution oxide screening methods increasingly important.However, currently available commercial devices are limited in their spatial resolution since they employ the traditional vibrating Kelvin probe technique, restricting their lateral resolution to several μm. In order to increase the lateral resolution of this measurement method we have combined the corona-charge deposition technique with Kelvin Probe AFM. We present initial results of this novel measurement technique and demonstrate its feasibility by measurements on lithographically prepared oxide patterns on Si wafers with different oxide thicknesses.
Field-induced reactions of water molecules at Si-dielectric interfaces
Authors: Tsetseris L. , Zhou X. , Fleetwood D. M. , Schrimpf R. D. , Pantelides S. T. 
Published: April 2011

ABSTRACTWater molecules and water-related species are present to a varying degree in SiO2 and other dielectrics and at Si-dielectric interfaces. Their presence, even in small concentrations, constitutes a critical reliability problem for present day ultrathin dielectrics. Here we present first-principles density functional calculations that probe the reactivity of water molecules at the Si-dielectric interface. We report results on different possible reaction pathways for water at the interface, including dissociation of water that can lead to the release of H+ ions. The released protons can migrate along the interface and depassivate dangling bonds. Results are also presented for the reaction of water with a hydrogen atom migrating laterally along the interface that lead to the creation of hydronium species. These atomic-scale mechanisms may account for at least some of the creation of interface traps and oxide trapped charge, the two features that give rise to negative bias temperature instability (NBTI), a well known reliability phenomenon that occurs in MOSFETs under normal operating and stress conditions.
Ultra Shallow Incorporation of Nitrogen into Gate Dielectrics by Pulse Time Modulated Plasma
Authors: Fukuda Seiichi , Suzuki Yoshimune , Hirano Tomoyuki , Kato Takayoshi , Kashiwagi Akihide , Saito Masaki , Kadomura Shingo , Minemura Youichi , Samukawa Seiji 
Published: April 2011

ABSTRACTIn order to obtain a controllability in the nitrogen depth profile in the oxy-nitride gate dielectrics which has been known to have a strong effect on MOS reliability, micro second ordered pulse was used for the inductive coupled plasma source in our pulse time modulated plasma. The radio frequency (RF) of source plasma and pulse frequency were 12.56 MHz and 10 kHz (100 micro second), respectively. Pulse duty ratio was varied from 20 to 100 %. 1.7nm thick thermal silicon dioxide films were subjected to the pulse time modulated plasma and analyzed by SIMS to see the depth profile of nitrogen. A new finding is that both the concentration and the peak position of nitrogen atoms in silicon dioxide films depend on the pulse duty ratio and plasma radiation time. NBTI lifetime was improved with decreased interface state density. We also used this technique to high-k material and investigated process characteristics of nitridation
Silicate interface formation during the deposition of Y2O3 on Si
Authors: Durand C. , Vallée C. , Dubourdieu C. , Bonvalot M. , Gautier E. , Joubert O. 
Published: April 2011

ABSTRACTThe interface behaviour during PE-MOCVD deposition of Y2O3 thin films on Si/SiO2 (8 Å) substrates has been investigated by XPS, TEM and OES analysis. The deposition process involves the sequential injection of MO precursors into the CVD chamber and is assisted by an O2 plasma. The injection frequency greatly influences the interface behaviour in terms of thickness and composition. The O2 plasma and the solvent also greatly affect substrate oxidation, and subsequently interface formation during deposition. Several mechanisms are discussed to account for substrate oxidation in view of a careful control of interface formation.
Microstructure and Electrical Properties of Zinc Oxide Thin Film Varistors Prepared by RF Sputtering
Authors: Chang Keng-Ming , Liu Chuan-Pu , Tsai Chon-Ming 
Published: April 2011

ABSTRACTThe thin film varistors of ZnO-Bi2O3 multilayer junctions were fabricated by RF sputtering. The nonlinear I-V characteristics and nonlinear coefficient, α, under reverse bias were found to be effected by the composition and structure of the varistor multilayers. The threshold voltage is predominantly determined by the microstructure and thickness of the Bi2O3 layer in thin film varistors, while that can be tuned by altering the donor density in ZnO, which was achieved by varying Al doping concentration or sputtering conditions. The higher leakage current and lower nonlinear coefficient associated with the ZnO layer doped with Al (ZnO:Al) can be improved by inserting another ZnO layer doped with selective transition metal impurities between ZnO:Al and Bi2O3 layers. The microstructure and defects of the multilayers were investigated in detail and related to the performance of the electrical properties.
Growth of Scandium Magnesium Oxide on GaN
Authors: Onstine A H , Herrero A , Gila B P , Kim J , Mehandru R , Abernathy C R , Ren F , Pearton S J 
Published: April 2011

ABSTRACTSc2O3 and MgO have been previously shown to be promising gate dielectrics for III-nitride devices. However, even though the films are initially epitaxial, they possess large numbers of defects due to the large mismatch with GaN. Thus further improvements in interface electrical characteristics will require a reduction in the interfacial mismatch between the oxides and the GaN. This paper discusses the feasibility of reducing the Sc2O3 lattice constant via the introduction of Mg and in particular investigates the relationship between growth parameters and microstructure for the resulting ScMgO alloy. Increasing the magnesium cell temperature was found to increase the growth rate but have little effect on surface roughness. Higher Mg cell temperatures also produced evidence in x-ray diffraction (XRD) of a second phase of MgScO which has the rock salt crystal structure and contains ∼2%Sc. Increasing the substrate temperature from 100°C to 300°C was found to have little effect on the growth rate and dramatically increased surface roughness. However higher substrate temperature combined with a lower Mg cell temperature produced a more uniform oxygen profile as determined by depth profiling Auger Electron Spectroscopy (AES). From AES and XRD, the solid solubility limit for ScxMg1−xO with the Bixbyite structure was reached at about XMg =0.28
Characterization of Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) FETs Using (Sr,Sm)0.8Bi2.2Ta2O9 (SSBT) Thin Films
Authors: Saiki Hirokazu , Tokumitsu Eisuke 
Published: April 2011

ABSTRACTWe have fabricated and characterized Pt (60nm) / (Sr,Sm)0.8Bi2.2Ta2O9 (SSBT, 130nm) / Pt (60nm) / Ti (10nm) / SiO2 (10nm) / p-Si (MFMIS:metal-ferroelectric-metal-insulator-semiconductor) structure FETs. The area ratio, the ratio of SSBT capacitor area to SiO2 capacitor, is varied from 1 to 15 in the MFMIS-FETs. It is demonstrated that MFMIS-FETs with area ratio of 6 have memory window of 0.5V with supply voltage of 5 V. Dependence of memory window on the area ratio is discussed.
A Thermogravimetric Study of Alakanethiolate Monolayer-Capped Gold Nanoparticle Catalysts
Authors: Maye Mathew M. , Chen Sandy , Chan Wai-Ben , Wang Lingyan , Njoki Peter , Lim I-Im-. S. , Mitchell Jennifer , Han Li , Luo Jin , Zhong Chuan-Jian 
Published: April 2011

ABSTRACTThe application of molecularly-capped gold nanoparticles (1–5 nm) in catalysis (e.g., electrocatalytic oxidation of CO and methanol) requires a thorough understanding of the surface composition and structural properties. Gold nanoparticles consisting of metallic or alloy cores and organic encapsulating shells serve as an intriguing model system. One of the challenges for the catalytic application is the ability to manipulate the core and the shell properties in controllable ways. There is a need to understand the relative core-shell composition and the ability to remove the shell component under thermal treatment conditions. In this paper, we report results of a thermogravimetric analysis of the alkanethiolate monolayer-capped gold nanoparticles. This investigation is aimed at enhancing our understanding of the relative core-shell composition and thermal profiles.
Formation and Properties of Silicon/Silicide/Oxide Nanochains
Authors: Kohno Hideo , Ohno Yutaka , Ichikawa Satoshi , Akita Tomoki , Tanaka Koji , Takeda Seiji 
Published: April 2011

ABSTRACTSilicon/silicide/oxide nanochains, which have an alternate arrangement of silicon/copper silicide composite nanoparticles and oxide nanowires, were fabricated using silicon/oxide nanochains as templates. Photoluminescence was observed at room temperature and considered to be due to recombination of excitons in oxide. Electrostatic potential in the material was also investigated by electron holography. No visible potential bending at the silicon/silicide interface was detected.
Exciton photoluminescence and energy transfer in nanocrystalline Si/ Si dioxide superlattice structures
Authors: Timoshenko V. Yu. , Shalygina O. A. , Lisachenko M. G. , Kashkarov P. K. , Kovalev D. , Heitmann J. , Zacharias M. , Kamenev B. V. , Tsybeskov L. 
Published: April 2011

ABSTRACTPhotoluminescence (PL) of nanocrystalline Si (nc-Si) assemblies formed by thermal crystallization of amorphous Si/SiO2 and SiO/SiO2 superlattices (SLs) has been investigated at different temperatures and excitation conditions. The low temperature resonant PL spectroscopy reveals phonon-assisted excitonic recombination. At room temperature the samples formed from a-SiO/SiO2 SLs possess relatively high PL quantum yield (∼ 1%). The PL transients have non-exponential decay, which indicates the exciton energy transfer in nc-Si ensembles. The excitonic energy of Er-doped nc-Si SL structures can be almost completely transferred to Er ions incorporated in SiO2 matrix that results in a strong emission line at 0.81 eV.
GaP Nanostructures: Nanowires, Nanobelts, Nanocables, and Nanocapsules
Authors: Seo Hee Won , Bae Seung Yong , Park Jeunghee 
Published: April 2011

ABSTRACTVarious GaP nanostructures such as nanowires, nanobelts, nanocables, and nanocapsules were synthesized by sublimation of ball-milled powders. They have a single-crystalline zinc blende structure with [111] growth direction. The morphology and structure were controlled by reactant gas, growth time, flow rate, and growth temperature. The size, morphology and properties of the nanostructures were examined by scanning electron microscopy, transmission electron microscopy, electron energy-loss spectroscopy (EELS), electron diffraction, energy dispersive x-ray spectroscopy, powder x-ray diffraction, and Raman spectroscopy using a 514.5 nm argon ion laser. The photoluminescence was carried out using the 458 nm line of an argon ion laser as the excitation source. The GaP nanowires are straight, cylindrical, and smooth in surface, with mean diameter of 40 nm and length up to 300 mm. The nitrogen-doped nanobelts and nanowires were synthesized by ammonia ambient gas. EELS data reveals that the nitrogen doping occurs mainly in the surface region. The PL spectrum shows the typical isoelectronic bound exciton peaks in the range of 2.11∼2.25 e V, suggesting a concentration of (1018 cm-3 nitrogen atoms. We also synthesized two types of GaP nanocables; GaP nanowire sheathed with the amorphous silicon oxide layers and with the graphite layers. The core-shell diameter is under 30 nm and the outerlayer can be removed by acid treatment to produce the 10 nm diameter GaP nanowires. The GaP encapsulated with BCN nanotubes were synthesized under the ammonia flow using the ball-milled carbon-containing boron oxide powders. The number of BCN layers is typically 10∼20.
Low Temperature Gas Phase Synthesis of Germanium Nanowires
Authors: Mathur Sanjay , Shen Hao , Werner Ulf 
Published: April 2011

ABSTRACTSingle crystal Ge nanowires (NWs) were obtained in high yield by gas phase decomposition of germanium di-cyclopentadienylide ([Ge(C5H5)2]), at 325 °C on iron substrates. Highresolution electron microscopy (SEM/TEM) showed Ge NWs to be uniform in terms of diameter (20 nm) and length (> 25 μm). The wire growth is selective and appears to be governed by a Ge-Fe alloy epilayer formed by the reaction between Ge clusters and iron substrate, during the initial stages of the CVD process. The supersaturation of Ge-Fe solid-solution with respect to Ge content induces the spontaneous formation of single crystal germanium nuclei that act as templates for the nanowire growth. X-ray and electron diffraction revealed the NWs to be single crystals of cubic germanium with a preferred growth direction[11–2]. The proposed base-growth model on Fe substrate is supported by TEM, EDX and XPS studies.
Energy exchange between optically excited Silicon Nanocrystals and Molecular Oxygen
Authors: Gross E. , Kovalev D. , Künzner N. , Diener J. , Koch F. , Timoshenko V. Yu. , Fujii Minoru 
Published: April 2011

ABSTRACTWe report on the photosensitizing properties of optically excited Silicon (Si) nanocrystal assemblies that are employed for an efficient generation of singlet oxygen. Spin triplet state excitons confined in Si nanocrystals transfer their energy to molecular oxygen (MO) adsorbed on the nanocrystal surface. This process results in a strong suppression of the photoluminescence (PL) from the Si nanocrystal assembly and in the excitation of MO from the triplet ground state to singlet excited states. The high efficiency of the energy transfer if favored by a broad energy spectrum of photoexcited excitons, a long triplet exciton lifetime and a highly developed surface area of the nanocrystal assembly. Due to the specifics of the coupled system Si nanocrystal – oxygen molecule all relevant physical parameters describing the photosensitization process are accessible experimentally. This includes the role of resonant and phonon-assisted energy transfer, the dynamics of energy transfer, and its mechanism.
Diffuse x-ray scattering from InGaAs/GaAs quantum dots
Authors: Köhler Rolf , Grigoriev Daniil , Hanke Michael , Schmidbauer Martin , Schäfer Peter , Besedin Stanislav , Pohl Udo W. , Sellin Roman L. , Bimberg Dieter , Zakharov Nikolai D. , Werner Peter 
Published: April 2011

ABSTRACTMulti-fold stacks of In0.6Ga0.4As quantum dots embedded into a GaAs matrix were investigated by means of x-ray diffuse scattering. The measurements were done with synchrotron radiation using different diffraction geometries. Data evaluation was based on comparison with simulated distributions of x-ray diffuse scattering. For the samples under consideration ((001) surface) there is no difference in dot extension along [110] and [-110] and no directional ordering. The measurements easily allow the determination of the average indium amount in the wetting layers. Data evaluation by simulation of x-ray diffuse scattering gives an increase of Incontent from the dot bottom to the dot top.
Dark exciton signatures in time-resolved photoluminescence of single quantum dots
Authors: Smith Jason M. , Dalgarno Paul A. , Warburton Richard J. , Gerardot Brian D. , Petroff Pierre M. 
Published: April 2011

ABSTRACTTime-resolved photoluminescence of single charge tuneable quantum dots allows us to probe the differences in recombination dynamics between neutral and negatively charged excitons. We find that the luminescence decay from a neutral exciton contains a second lifetime component of several nanoseconds that is not present in the luminescence from singly or doubly charged excitons. We attribute the slowly decaying component to excitation cycles in which the initial exciton formed in the dot is dark, with angular momentum M = 2, and which subsequently scatters into the bright state with M = 1.The nature of the scattering mechanism is revealed by the dependence of the lifetime on the electrical bias applied across the charge-tuneable device. That the lifetime changes by an order of magnitude within a short bias range implies that the dark-to-bright transmutation does not occur through a simple spin flip. Rather it appears to come about by the dot briefly entering a higher energy charging state which allows exchange of the existing electron with another from the n-type contact region. We model the lifetimes and relative intensities of the two decay components using a simple rate equation analysis.
Measurement Techniques for Thermoelectric Materials and Modules
Authors: Hogan Tim , Loo Sim , Guo Fu , Short Jarrod 
Published: April 2011

ABSTRACTThermoelectrics is a multidiscipline area of study, rich in condensed matter physics, chemistry, engineering, and material science. The figure of merit used for evaluating individual materials consists of three interdependent material properties. The measurement of these properties should be taken on the same sample for all three measurements, preferably simultaneously. Each of these measurements requires close attention to potential sources of losses for accurate analysis of the materials and testing of theoretical models. For example, relatively simple scanning measurement techniques can be used to gain insight into accurate geometry measurements and influences of contact dimensions. In addition, the field of thermoelectrics spans a wide temperature range, from cryogenic temperatures to > 1000 °C. This requires systems capable of large temperature variations, and/or multiple measurement systems for various ranges of interest. Additional measurements, such as Hall effect, help to gain further insight into the material properties and their optimization. The number and importance of measurements is further extended as the development of devices from these new materials is initiated, where studies of contact resistance and overall device performance must be evaluated. For mechanical robustness of fabricated modules, properties such as the coefficient of thermal expansion, and grain size for the new materials are of interest. Models for device behavior are useful in evaluating the measured results and further extracting material and device properties. In this paper, we review measurements used in evaluating bulk thermoelectric materials some of the information that can be extracted from these measurements, along with a model that can be used in conjunction with these measurements for module design.
Using the Compatibility Factor to Design High Efficiency Segmented Thermoelectric Generators
Authors: Jeffrey Snyder G. , Caillat T. 
Published: April 2011

ABSTRACTUsing thermoelectric compatibility, efficient thermoelectric generators are rationally designed. With examples, compatible and incompatible systems are explained and materials proposed for targeted development. The compatibility factor explains why segmentation of TAGS with SnTe or PbTe produces little extra power, while filled skutterudite increases the efficiency from 10.5% to 13.6%. High efficiency generators are designed with compatible n-type La2Te3, and similar p-type material, while incompatible SiGe alloys actually reduce the efficiency. A refractory metal with high p-type thermopower (> 100 μV/K) is required for development. The Chevrel compound Cu4Mo6Se8is a compatible p-type metal that provides a modest increase in efficiency. A fully segmented generator using Bi2Te3-type, PbTe, TAGS, Zn4Sb3, skutterudite, La2Te3, and Chevrel compounds between 25° C and 1000° C will achieve 18.1% conversion efficiency.