We present a one-dimensional simulation study of the capacitance-voltage (C-V) and current-voltage (I-V) characteristics in MOS devices with high mobility semiconductors (Ge and III-V materials) and non-conventional gate stack with high-κ dielectrics. The C-V quantum simulation code self-consistently solves the Schrödinger and Poisson equations and the electron transport through the gate stack is computed using the non-equilibrium Green’s function formalism (NEGF). Simulated C-V characteristics are successfully confronted to experimental data for various MOS structures with different semiconductors and dielectric stacks. Simulation of I-V characteristics reveals that gate leakage current strongly depends on gate stacks and substrate materials and predicts low leakage current for future CMOS devices with high mobility materials and high-κ dielectrics.

In this paper, we present a systematic study of coherent phonons in Si/SiGe superlattices with two different periods. The superlattice periodicity affects the acoustic properties of the structure. Transient thermoreflectance (TTR) technique is used to perform picosecond ultrasonics experiments and then, investigate coherent zone-folded acoustic phonons in different Si/SiGe superlattice structures. Several classes of coherent phonons are produced in the superlattice, whose generation mechanisms are different: Brillouin oscillations, coherent longitudinal-acoustic phonon Bragg reflection and impulsive stimulated Raman scattering (ISRS).

A novel three dimensional (3D) self-assembled hierarchical bismuth oxide was prepared via a sol-gel synthesis with the aid of capping agent of polyethylene glycol-8000 (PEG-8000) at 85 ℃ in 45 min. The morphology evolution was studied versus reaction time and interpreted in terms of growth mechanisms. The as-grown 3D hierarchical flower-like bismuth oxide was crystalline cubic gamma-phase. The morphology and crystal phase of these 3D cubic gamma-phase bismuth oxide flowers were not changed with heating up to 600 ℃. The flower-like morphology was attributed to modification of the growth kinetics by the capping agent from the PEG-OH bond bridging with bismuth ions. Europium doped gadolinium oxide shell were further deposited on the bismuth oxide cores through sol-gel synthesis showing good photoluminescence characteristics at 610 and 622 nm under the excitation at 280 nm.

The performance metrics of highly scaled n-type InSb/InP and InAs/InP core/shell nanowire (NW) field-effect transistors (FETs) are theoretically investigated using an 8-band k•p model and a semiclassical ballistic transport model. We present the ON-current, the intrinsic cut-off frequency, the gate-delay time, the power-delay product, and the energy-delay product of NWFETs with two NW diameters of 10 nm and 12 nm, which operate in the quantum capacitance limit. We compare the results to the numbers predicted or projected for other materials and dimensionalities and find good agreement. Within a source Fermi energy range of 0.1 – 0.3 eV for all devices, the ON-current varies from 7 – 58 μA, the intrinsic cut-off frequency ranges from 8 – 15 THz, the power-delay product varies from 2×10-20 – 9.7×10-19 J, the gate-delay time varies from 2 – 19 fs, and the energy-delay product ranges from 7×10-35 – 1×10-32 Js. These NWFETs, thus, provide both ultra-low power switching and high-speed.

In order to restrain global warming and to realize a sustainable global energy system, further enhancements in energy efficiency are required. One reliable technology for reducing greenhouse gas emissions and the consumption of fossil fuel is thermoelectric technology, which can directly convert heat into electricity and consequently increases the energy conversion efficiency of power generation by combustion. Magnesium silicide (Mg2Si) is a promising candidate for a thermal-to-electric energy-conversion material at operating temperatures ranging from 500 to 800 K. Mg2Si exhibits many promising characteristics, such as the abundance of its constituent elements in the earth’s crust and the non-toxicity of its processing by-products, resulting in freedom from concerns regarding prospective extended restrictions on hazardous substances.The efficiency of a thermoelectric device is characterized by the dimensionless figure of merit, ZT. It is well known that several kinds of dopants are effective in improving the thermoelectric performance of n-type Mg2Si. With Bi-doped n-type Mg2Si, we have achieved a maximum value of the dimensionless figure-of-merit ZT of ˜1.0 at ˜ 850 K. However, the correlation between the ZT values and the power generation characteristics, which is essential to understand in order to design a structure for a TE power generation module, has not been sufficiently investigated. In order to design a structure for a thermoelectric module using Mg2Si, we examined the correlation between the ZT values and the power-output of a single element using Mg2Si (ZT = 0.6) and Mg2Si doped with donor impurities such as Al and/or Bi (ZT = 0.65˜0.77). The measured single element was 2×2 mm2 in section and 10 mm long. Additionally, we developed and evaluated a new architecture based on a ‘unileg’ structure Mg2Si TE power generation module, which can improve the module lifetime and simplify its manufacture. As a starting material for the fabrication of the single element and the TE modules, pre-synthesized polycrystalline Mg2Si, fabricated by UNION MATERIAL was used. The material was sintered using a plasma-activated sintering (PAS) technique, and, at the same time, Ni electrodes were formed on the Mg2Si by employing of a monobloc PAS technique. The thermoelectric power-outputs were measured under a temperature difference, ΔT, ranging from 100-to-500 K by using UNION MATERIAL UMTE-1000M.The observed power-output for single element of Mg2Si (ZT = 0.6), 2 at % Bi-doped Mg2Si (ZT = 0.65) and 1at % Bi + 1at % Al-doped Mg2Si (ZT = 0.77) were 23.2 mW, 13.6 mW and 19.4 mW respectively at ΔT = 500 K (between 873 K and 373 K). For the new architecture based on the unileg structure thermoelectric module, the observed value for power-output-per-unit-area was 12 mW/mm2 at ΔT = 500 K.

Ball milling of ammonothermally synthesized GaN powders was performed in an ethanol solution for a variety of durations, resulting in average particle sizes of nanometer. The ball milled powders showed an obviously brightened color and improved dispersability, indicating reduced levels of aggregation. X-ray diffraction (XRD) peaks of the ball milled GaN powders were significantly broadened compared to those of the as-synthesized powders. The broadening of the XRD peaks was partially attributed to the reduction in the average particle size, which was confirmed through SEM analyses. On the other hand, rare earth doping of commercial GaN powders was also achieved through a ball mill assisted solid state reaction process. Rare earth salts were mixed with GaN powder by ball milling. The as-milled powders were heat treated under different conditions to facilitate the dopant diffusion. Luminescence properties of the rare earth doped GaN powders at near infrared range were investigated and the results were discussed.

The mammalian inner ear is remarkably sensitive to quiet sounds, exhibits over 100dB dynamic range, and has the exquisite ability to discriminate closely spaced tones even in the presence of noise. This performance is achieved, in part, through active mechanical amplification of vibrations by sensory hair cells within the inner ear. All hair cells are endowed with a bundle of motile microvilli, stereocilia, located at the apical end of the cell, and the more specialized outer hair cells (OHC's) are also endowed with somatic electromotility responsible for changes in cell length in response to perturbations in membrane potential. Both hair bundle and somatic motors are known to feed energy into the mechanical vibrations in the inner ear. The biophysical origin and relative significance of the motors remains a subject of intense research. Several biological motors have been identified in hair cells that might underlie the motor(s), including a cousin of the classical ATP driven actin-myosin motor found in skeletal muscle. Hydrolysis of ATP, however, is much too slow to be viable at audio frequencies on a cycle-by-cycle basis. Heuristically, the OHC somatic motor behaves as if the OHC lateral wall membrane were a piezoelectric material and the hair bundle motor behaves as if the plasma membrane were a flexoelectric material. We propose these observations from a continuum materials perspective are literally true. To examine this idea, we formulated mathematical models of the OHC lateral wall “piezoelectric” motor and the more ubiquitous “flexoelectric” hair bundle motor. Plausible biophysical mechanisms underlying piezo- and flexoelectircity were established. Model predictions were compared extensively to the available data. The models were then applied to study the power conversion efficiency of the motors. Results show that the material properties of the complex membranes in hair cells provide them with the ability to convert electrical power available in the inner ear cochlea into useful mechanical amplification of sound induced vibrations at auditory frequencies. We also examined how hair cell amplification might be controlled by the brain through efferent synaptic contacts on hair cells and found a simple mechanism to tune hearing to signals of interest to the listener by electrical control of these motors.

Epitaxial diamond films were deposited on polished single crystal Ib type HPHT diamond plates of (100) orientation by microwave CVD. The epilayers were used for the fabrication of surface channel MESFET structures having sub-micrometer gate length in the range 200-800 nm. Realized devices show maximum drain current and trasconductance values of about 190 mA/mm and 80 mS/mm, respectively, for MESFETs having 200 nm gate length. RF performance evaluation gave cut off frequency of about 14 GHz and maximum oscillation frequency of more than 26 GHz for the same device geometry.

The influence is investigated of the average valence electron number on the systematic changes of a Ni2MnGa based alloy series. The experimental investigation focuses on an isoelectronic alloy series Ni2Mnx(CrFe)1-x/2Ga for which the average valence electron number is unchanged for any value of x. Based on the changes of physical properties of alloys in this series compared to Ni2MnGa it is argued that local lattice distortions are more relevant for driving the change in alloy characteristics, such as the martensitic phase transition temperature or the ferromagnetic ordering temperature, than the band filling by valence electrons.

Two fundamentally different types of domains were resolved in multiferroic MnWO4 by optical second harmonic generation (SHG). Hybrid-multiferroic (absolute) domains reflect the magnetic chirality coupled 1:1 to the spontaneous polarization because of the magnetic origin of the ferroelectric order. Magnetic translation (relative) domains reflect discontinuities in the progression of the magnetic spin spiral. SHG topography is the only experimental method so far allowing one to image both types of domains. The imaging procedure and the SHG contributions involved are therefore discussed in detail.

The effect of polisher kinematics on average and standard deviation of shear force and removal rate in copper CMP is investigated. A ‘delamination factor’ consisting of average shear force, standard deviation of shear force, and required polishing time is defined and calculated based on the summation of normalized values of the above three components. In general, low values of the ‘delamination factor’ are preferred since it is believed that they minimize defects during polishing. In the first part of this study, 200-mm blanket copper wafers are polished at constant platen rotation of 25 RPM and polishing pressure of 1.5 PSI with different wafer rotation rates and slurry flow rates. Results indicate that at the slurry flow rate of 200 ml/min, ‘delamination factor’ is lower by 14 to 54 percent than at 400 ml/min. Increasing wafer rotation rate from 23 to 148 RPM reduces ‘delamination factor’ by approximately 50 percent and improves removal rate within-wafer-non-uniformity by appx. 2X. In the second part of this study, polishing is performed at the optimal slurry flow rate of 200 ml/min and wafer rotation rate of 148 RPM with different polishing pressures and platen rotation rates. Results indicate that ‘delamination factor’ is reduced significantly at the higher ratio of wafer to platen rotation rates.

PLLA microparticles were successfully fabricated via pulsed-DC electrospray. In this study, we investigated the effect of the pulsed voltage characteristics (e.g. pulse frequency, pulse amplitude and pulse width) on the particle’s size. We found that pulse frequency, pulse amplitude, pulse width, and the combinations of these factors had a statistically significant effect on the particle’s size. The process conditions to obtain smaller particles with uniform shape and size are a low pulse frequency, high pulse amplitude, and long pulse width (or a high duty cycle).

Alloy 22 is highly resistant to all forms of corrosion; however, it may suffer crevice corrosion in presence of chloride ions especially at temperatures higher than ambient and at anodic potentials. The susceptibility of Alloy 22 to suffer crevice corrosion is highly dependent on the type of electrolyte solution that is in contact with the alloy including variety of species in solution and their relative concentration. Laboratory research has shown that at a constant chloride concentration, the susceptibility of Alloy 22 to crevice corrosion is not influenced by the nature of the cations present in solution. On the other hand, that nature of the anions is highly influential. Of the anions present in ground water, only chloride is detrimental and the others are inhibitors or innocuous for crevice corrosion susceptibility. That is, the presence of the other anions counter balances the negative effect of chloride. The inhibition effect is explained and the likelihood that Alloy 22 would suffer crevice corrosion in contact with ground water is discussed.

Ar cluster ions in the size range 1000�16000 atoms/cluster were irradiated onto Si substrates at incident energies of 10 and 20 keV and the sputtering yields were measured. Incident cluster ions were size-selected by using the time-of-flight (TOF) method. The sputtering yield was calculated from the sputtered Si volume and irradiation dose. It was found that the sputtering yields decreased with increasing incident cluster size under the same incident energy conditions. The integrated sputtering yields calculated from the sputtering yields measured for each size of Ar cluster ions, as well as the cluster size distributions, were in good agreement with experimental results obtained with nonselected Ar cluster ion beams.

Phantomlike elastomer simulations do not always deform globally affinely in the way that classical theory predicts. Assuming that each crosslink will deform affinely with its topological neighbors gives much better results, and creates a way to isolate crosslinks with unpredictable deformation properties. The correlation of non-affinities and network properties depends on the constitutive model and boundary condition used. We always find a correlation between local density of crosslinks and degree of non-affinity.

Bio-electrospraying and aerodynamically assisted bio-jetting are rapidly evolving approaches for directly handling living cells and organisms. In this article we demonstrate how these technologies now elucidated as being safe for handling living cells and organisms can be explored not only for tissue engineering and regenerative medicine but also in biology for single cell and organism diagnostics.

Measurements of single asperity wear on oxidized silicon surface in aqueous potassium hydroxide (KOH) using atomic force microscopy (AFM), where the single crystal silicon tip was used both to tribologically load and image the surface, is presented. AFM was also operating in the lateral (frictional) force mode to investigate the pH dependence of kinetic friction between the tip and the SiO2 surface. It was shown that the Si tip wear amount strongly depended on the solution pH value and was at a maximum at around pH 10. It was also found that the Si removal volume in mol was approximately equal to that of SiO2 irrespective of the solution pH value. This equality implies that the formation of the Si–O–Si bridge between one Si atom of the tip and one SiO2 molecule of the specimen at the wear interface. The surface of the Si tip is then oxidized. Finally, the bond rupture by the tip movement will occur, the dimeric silica (OH)3Si–O–Si(OH)3, including the Si–O–Si bridge, is dissolved in the KOH solution. The frictional signal is also sensitive to the pH values of the solution and peaked at around pH 10. These results indicate that the removal behavior of the Si tip and SiO2 surface would be affected by the frictional force between the Si and the SiO2, because of an increased liquid temperature and a compressive stress in Si and SiO2 networks. Strong influence is observed by the pH of the ambient solution confirming the important role of the OH− in the wear mechanism. Pressure dependence of the microwear behavior under aqueous electrolyte solutions has also been investigated. A microscopic removal mechanism, which is determined by interplay of the diffusion of water in Si and SiO2, is presented.

To meet the stringent requirements of device integration and manufacture, surface defects and mechanical stresses that arise during chemical mechanic planarization (CMP) must be reduced. Towards this end, we have synthesized multiple hybrid and composite particles on micron length scales consisting of siloxane co-polymers functionalized with inorganic nanoparticles. These particles can be easily tailored during synthesis, leading to softer or harder abrasion when desired. Upon using these particles for the planarization of silicon oxide wafers, we obtain smooth surfaces with reduced scratches and minimal particle deposition, which is an improvement from conventional abrasive materials like pure silica, ceria and alumina nanoparticle slurries. Tribological characteristics during polishing were examined using a bench top CMP tester to evaluate the in situ co-efficient of friction. Characterization of the hybrid and composite particles has been done using infrared spectroscopy, dynamic light scattering, and electron microscopy. Surface roughness of the wafers was examined using atomic force and optical microscopy while removal rate measurements were conducted using ellipsometry at multiple angles.

In many instances the quality of the surface in ZnO nanoscale systems is a key performance-defining parameter. The surface itself could be a very significant source of lattice defects as well as contaminating impurities, and this influence may extend into the sub-surface vicinity. In our work, key element of the surface analysis is the surface photovoltage (SPV) spectroscopy known for its advantages, such as: identification of conduction vs. valence band nature of the defect-related transitions and the defect level positions within the band gap, ability to measure relatively low densities of surface defects as well as their cross sections. Additional information can be obtained from the SPV transient measurements. In our system, SPV characterization is run in high vacuum, complemented by in situ remote plasma treatment. This combination of surface-sensitive and surface-specific tools is well-suited for studying surface properties with a high degree of reliability since there is no exposure to common air contaminants between processing and characterization cycles. We employed O/He remote plasma treatments of ZnO nanocrystalline surfaces. In situ SPV spectra and transient measurements of the as-received and processed samples revealed, on the one hand, a number of common spectral features in different ZnO nanopowder specimens, and, on the other hand, a noticeable plasma-driven changes in the surface defect properties, as well as in the overall electronic and optical surface characteristics.