High mobility channel materials and new device structures will be needed to meet the power and performance specifications in future technology nodes. Therefore, the use of Ge and III/V materials and novel devices such as heterojunction TunnelFET’s is investigated for future CMOS applications. High-performance CMOS can be obtained by combining Ge pMOS devices with nMOS devices made on III/V compounds such as InGaAs. In all cases the key challenge is the electrical passivation of the interface between the high-k dielectric and the alternative channel materials.Recent studies have demonstrated good electrical properties of the GeO2/Ge interface. Since the GeO2 layer is very hygroscopic, full in-situ processing of GeO2 formation and high-k deposition must be performed or other methods must be employed to stabilize the GeO2 layer. One of the most successful passivation techniques for Ge MOS gate stacks is a thin, epitaxial layer of Si. A lot of attention went into better understanding of this passivation and the effects of its optimization on various device characteristics. It was found that mobility and Vt trends in both pMOS and nMOS transistors can be explained based on defects located at the Si/SiO2 interface.Unfortunately, III-V/oxide interfaces are not quite as robust and most interfaces present rather high densities of interface states. Although, considerable improvements have been realized in the reduction of the interface state density, further developments are required to obtain high performance MOS devices. To this purpose various passivation methods were critically evaluated. Simulations using Density Functional Theory reveal the possibility of using a thin amorphous layer made of GeOX to obtain an electrically unpinned gap. The major challenge resides in the control of the c-Ge thickness and the oxidation of this layer to avoid the diffusion of oxygen atoms at the Ge/GaAs(001) interface. Promising results are obtained by optimizing the surface preparation, high-k deposition and annealing cycle on In0.53Ga0.47As-Al2O3 interfaces. Self-aligned inversion channel n-MOSFETs fabricated on p-type In0.53Ga0.47As demonstrate inversion-mode operation with high drive current and a peak electron mobility of 3000 cm2/Vs.Since ultimately the major showstopper on the scaling roadmap is not device speed, but rather power density, the introduction of these advanced materials will have to go together with the introduction of new device concepts. Novel structures such as heterojunction TunnelFET’s can fully exploit the properties of these new materials and provide superior performance at lower power consumption by virtue of their improved subthreshold behaviour. Vertical surround gate devices produced from nanowires allow the introduction of a wide range of materials on Si. This illustrates the possibilities that are created by the combination of new materials and devices to allow scaling of nanoelectronics beyond the Si roadmap.

Electrical characterization of CaCu3Ti4O12 (CCTO) ceramics with scanning probe based techniques has been carried out. In particular, conductive atomic force microscopy (C-AFM) and scanning impedance microscopy (SIM) have been used to demonstrate the presence, shape and size in CCTO ceramics of the different electrically domains, both at the grain boundaries and within the grains. The electrical characteristics of single grains and of single domains have been evaluated and it has been observed that the conductive grains are surrounded by insulating grain boundaries.

Carbon steel overpack will corrode by consuming oxygen introduced by repository construction after closure of repository and then will keep the reducing environment in the vicinity of repository. The iron corrosion products can migrate in bentonite as ferrous ion through the interlayer of montmorillonite replacing exchangeable sodium ions in the interlayer. This replacement of sodium with ferrous ion may affect the migration behavior in the altered bentonite not only for redox-sensitive elements but also the other ions. Therefore the authors have carried out electromigration experiments of potassium or rubidium with source of iron ions supplied by anode corrosion of iron coupon in compacted bentonite. Five to fifteen micro liter of tracer solution containing 3.3 M of KCl or 2.2 M of RbCl was spiked on the interface between an iron coupon and bentonite, which dry density was around 1.4 Mg/m3, before assembling. The iron coupon was connected as the working electrode to the potentiostat and was held at a constant supplied potential between - 600 and 300 mV vs. Ag/AgCl reference electrode for up to 8 days. Potassium could migrate faster and deeper in bentonite specimen than iron in each condition. On the other hand rubidium could migrate slower than iron. Migration velocity was a function of applied electrical potential and 8 to 14 nm/s for potassium, 5 to 10 nm/s for iron and 3 to 5 for rubidium, respectively. Dispersion coefficient was also a function of applied potential and 10 to 14 × 10−12 m2/s for potassium, 4 to 8 overv 10−12 m2/s for rubidium and 2 to 4 overv 10−12 m2/s for iron, respectively. Diffusion experiments were also carried out for comparison. Potassium and rubidium might migrate slightly slower in the altered bentonite by iron corrosion than in ordinary compacted bentonite.

Our ability to fabricate close-packed single crystal rutile TiO2 nanowire arrays with average inter-wire distances of 5-10 nm allows us to create and control FRET-induced coupling effects, which can occur in this distance regime, in this architecture. We explored the use of such coupling to boost the performance of nanowire excitonic solar cells. Using Ru complex triplet dye N719 as the energy acceptor and fluorescent tetra tert-butyl substituted zinc phthalocyanine as the energy donor (see Fig. 1 for molecular structures), we obtained up to a four fold improvement in the quantum yield for red photons in the 660-690 nm spectral range. Similarly, by using a carboxylated unsymmetrical squaraine dye as the energy acceptor and highly fluorescent Nile Red dye as the donor (see Fig. 1 for molecular structures), we obtained 60% increased external quantum yields for photons in the 480-580 nm spectral range. For both systems, the use of FRET broadened spectral coverage and improved light harvesting. In this report, we also develop fundamental design principles in choosing donor-acceptor combinations for high efficiency FRET-enhanced solar cells in nanowire array architectures.

A Yb:KGW femtosecond laser (400 fs) with 3rd and 4th harmonic generators (wavelength = 343 and 258 nm) was adopted to a locally built 3DAP instrument to assist field evaporation from ceramics tips that were bonded on tungsten wire. Using this setting, we have demonstrated that quantitative atom probe tomography is possible from Y2O3-ZrO2-MgAl2O4, (Ce,Y)O2, Li(Co,Ni,Mg,Al)O2 sintered bulk ceramics, which are all insulators.

The objective of this study is to characterize the nanoparticle dispersion and to investigate its effect on the surface mechanical properties of nanoparticle-polymer systems. Two types of TiO2 nanoparticles were chosen to mix in two polymeric matrices: solvent-borne acrylic urethane (AU) and water-borne butyl-acrylic styrene latex (latex) coatings. Nanoparticle dispersion was characterized using laser scanning confocal microscopy. Overall, Particle A (PA, without surface treatment) dispersed better than Particle B (PB, organic treatment) in both systems. The AU-PA system exhibited the best dispersion of the four systems, however PB forms big clusters in both of the matrices. Surface mechanical properties, such as surface modulus at micron and sub-micron length scales were determined from depth sensing indentation equipped with a pyramidal tip or a conical tip. The surface mechanical properties were strongly affected by the dispersion of nanoparticle clusters, and a good correlation was found between dispersion of nanoparticle clusters near surface and the modulus-depth mapping using a pyramid tip.

In solid oxide fuel cells, the mechanism of hydrogen oxidation is complex. During this process, protonated forms of monoclinic zirconia may be formed, motivating their study within the framework of density-functional theory (DFT). Using the HCTH/120 exchange-correlation functional, the monoclinic phase of zirconia is, correctly, predicted to be more stable than cubic or tetragonal polymorphs at 0 K, in agreement with previous theoretical results. Several local minima are identified of a proton in monoclinic zirconia, modeled using (up to) a 3×3×3 arrangement of unit cells, in which the proton is bonded to one of the two available oxygen atom types, O1 or O2. The lowest energy structure of the proton bonded to O1 is favored by 0.39 eV compared to that of the proton bonded to O2. Based upon a vibrational analysis as well as finite-temperature Born-Oppenheimer molecular dynamic simulations, this preference of the proton for O1 is suggested to persist at fuel cell operating temperatures.

A simple 1-dimensional Monte Carlo (KMC) model has been developed to simulate the chemical vapour deposition (CVD) of a diamond (100) surface. The model considers adsorption, etching/desorption, lattice incorporation, and surface migration along and across the dimer rows. The reaction probabilities for these processes are re-evaluated in detail and their effects upon the predicted growth rates and morphology are described. We find that for standard CVD diamond conditions, etching of carbon species from the growing surface is negligible. Surface migration occurs rapidly, but is mostly limited to CH2 species oscillating rapidly back and forth between two adjacent radical sites. Despite the average number of migration hops being in the thousands, the average diffusion length for a surface species is <2 sites.

Ni-Mn-Ga based magnetic shape memory (MSM) materials have been studied since 1998 in Finland at the Helsinki University of Technology (TKK, previously HUT). The large HUT-MSM-project resulted in MSM-alloys with high service temperature, 10 % field-induced-strain, as well as circumstances when and how a Ni-Mn-Ga alloy exhibits this phenomenon. The understanding of the structure and behavior of twin boundaries, and their role, for example, in the vibration damping and long-term actuation has been enhanced in the recent projects. Twin boundaries have been studied by XRD, by high-resolution transmission electron microscopy (HRTEM), and by in-situ straining in TEM, the last one in co-operation with the Institute of Physics in Prague (ASCR-IP), Czech Republic. The results obtained by neutron diffraction in co-operation with Hahn-Meitner-Institut Berlin, Institute for Metal Physics (IMP), Kiev, and Institut Laue-Langevin (ILL), Grenoble, have given new crystallographic information. Damping of Ni-Mn-Ga polymer composites has been proved to be excellent at high stiffness levels with the loss factor = 0.6 at E ≈ 1 GPa. This research was carried out in co-operation with the University of California Los Angeles (UCLA), USA. In the long-term actuation, a fatigue life of 2×109 has been recorded for a five-layered modulated Ni-Mn-Ga structure in mechanical cycling. The evolution of the MSM parameters during the long-term use is recorded and used as an input data for the models developed in the European MAFESMA co-operation. The search for alloys with wide stable thermal property range showing MSM effect has continued and alloys that are stable down to 4 K have been established. Modeling based on Ginsburg-Landau theory has been applied to evaluate aging and thermal fluctuations in the modulated Ni-Mn-Ga structures. As a commercial target, AdaptaMat Ltd. develops technology to produce Ni-Mn-Ga magnetic shape memory material with improved quality, lower twinning stress, longer fatigue life as well as lower cost and better availability for use in research and development.

Thermochromic materials change color with temperature. Organic ternary mixtures composed of a dye, developer and solvent can reversibly change color with temperature. Although they are used in many commercial products, little is known about the detailed mechanism of thermochromism. Given the wide range of available components and compositions that could potentially show thermochromic behavior, we have embarked on combinatorial studies using inkjet printing to directly prepare thermochromic mixtures on paper.

This study examines the effect of cyclic damage on the constitutive response and microstructural evolution of SAC305 solder. Cyclic damage is induced through isothermal, mechanical cycling tests at high strain rate and room temperature, using modified lap shear microscale specimens (180μm wide solder joint). The properties of interest are elastic, plastic, yield, and viscoplastic material constitutive behavior. In the current study, creep strain accumulation is accommodated when determining the constants, unlike those reported in prior studies [1]. Insights into the evolution of the measured properties are provided by correlating previously reported microstructural grain evolution of microscale SAC305 solder as a function of cyclic damage [2, 3].

The hysteresis response and the elastic, plastic and yield measurements from the initial cycles show significant piece-to-piece variability (similar to prior virgin state viscoplastic measurements [3]). The scatter arises since as-reflowed SAC solder joints at length scales of 200μm consist of only a few anisotropic Sn grains that make the joint mechanically inhomogeneous. However, when subject to mechanical cycling fatigue at room temperature these joints undergo grain homogenization due to recrystallization, which is a possible explanation to the drop in scatter with progressing damage. The observed grain evolution is similar to that seen in solder joints under life-cycle loading.

The elastic-plastic response and yield strength of SAC305 solder do not show significant contribution from creep deformations at the chosen load levels. The properties degrade with increasing accumulated cyclic damage, at a rate that is proportional to the severity of the cyclic load. The yield stress measurements suggest that SAC305 obeys an independent hardening rule, rather than isotropic or kinematic hardening. The performance of a continuum damage mechanics based model from prior studies in representing the measured degradation in elastic, plastic and yield properties is discussed [4,5].

Comparison of the creep behavior of cycled SAC305 specimens (at 50% load drop) with that of uncycled specimens shows that the effective creep compliance and effective secondary creep strain rate increase significantly. As a point of comparison, the creep resistance of cycled SAC305 specimens is even lower than that of as-reflowed Sn37Pb specimens. Similar changes are seen in the stress relaxation behavior. Challenges and limitations of the current studies are included.

We have fabricated the nano-floating gate memory with the TiSi2 and WSi2 nanocrystals embedded in the dielectrics. The TiSi2 and WSi2 nanocrystals were created by using sputtering and rapidly thermal annealing system, and then their morphologies were investigated by transmission electron microscopy. These nanocrystals have a spherical shape with an average diameter of 2-5 nm. The electrical properties of the nano-floating gate memory with TiSi2 and WSi2 nanocrystals were characterized by capacitance-voltage (C-V) hysteresis curve, memory speed and retention. The flat-band voltage shifts of the TiSi2 and WSi2 nanocrystals capacitors obtained appeared up to 4.23 V and 4.37 V, respectively. Their flat-band voltage shifts were maintained up to 1.6 V and 1 V after 1 hr.

Many impurity complexes in silicon such as boron-oxygen and iron-boron complexes are found to be bistable. Commonly bistable recombinative complexes in silicon are studied through carrier lifetime experiments and are analysed by use of Shockley-Read-Hall (SRH) recombination theory. SRH recombination theory is valid for stable defects with one configuration and one energy level in the band gap, however, the theory might fail upon considering the recombination centers through bistable defects, which can be in two different configurations separated by a potential barrier. This work presents a study of electrical properties of silicon with bistable impurity complexes. The analysis has been performed for statistics of free electrons and holes, their recombination rate and lifetime. The results have been compared with those obtained from the Shockley-Read-Hall recombination theory.

Atomic force acoustic microscopy (AFAM) is a non-destructive method able to determine the indentation modulus of a sample with high lateral and depth resolution. We used the AFAM technique to measure the indentation modulus of film-substrate systems Msam and then to extract the value of the indentation modulus of the film Mf . The investigated samples were films of silicon oxide thermally grown on silicon single crystal substrates by use of dry and wet oxidation methods. The thickness of the samples ranged from 7 nm to 28 nm as measured by ellipsometry. Our results clearly show that the values of Msam obtained for the film-substrate systems depended on the applied static load and the film thickness. The observed dependency was used to evaluate the indentation modulus of the film. The values obtained for Mf ranged from 77 GPa to 95 GPa and were in good agreement with values reported in the literature.

Structural rules have been formulated for the molecular crystal of ammonia borane (AB, NH3BH3) and clathrates thereof. These rules are similar to the “ice rules” in water. Periodic structures of possible clathrates of AB have been predicted. A rigorous analysis of the uniform space filling tessellations of 3D space has been performed resulting in the identification of two promising structures for AB clathrates. Additional five structures have been identified exploiting features and properties of AB molecules. The screening, or evaluation, of proposed periodic structures has been performed on the basis of their stability determined at the density functional level of theory. Hydrogen capacity of the most stable periodic structure (cantitruncated cubic honeycomb) is estimated to be 21 wt%, 19% chemically bound in AB and 2 wt% of H2 physisorbed in the cages of AB.

Magnetofluorescent hybrid nanoparticles consisting of Au layer, an iron oxide moiety, and fluorescent molecules could provide a promising platform for development of multimodal imaging and therapy approaches in the treatment of cancer. However, the feasibility of this platform has yet to be fully explored. In this study, we synthesized biocompatible dumbbell-like iron-gold hybrid particles that are superparamagnetic, fluorescent and with strong optical absorption. Furthermore, we showed that hybrid nanoparticles can be conjugated to targeting agents allowing for specific targeting of cancer cells.

Photonic thermal conductance of a multi-layer photonic crystal, when normalized with the corresponding thermal conductance of vacuum at each temperature, can be significantly below unity. The minimum of this normalized thermal conductance occurs at the high-temperature limit, and the conductance value at this limit is independent of the layer thicknesses. We give an analytic theory to explain such independence, and show that it is related to the ergodic nature of the distribution of photonic bands in frequency space.

Recent research has found that cell spreading on materials affects cell functions, including proliferation and differentiation. Also, cell spreading is related to filopodia extension which has been shown to be dependent on substrate topography. To better understand this correlation, live-cell imaging was used here to investigate osteoblast (bone forming cell) filopodia extension and cell spreading on two different kinds of diamond. Nanocrystalline diamond (NCD) and submicron crystalline diamond (SMCD) were fabricated to possess similar surface chemistry but different topographies, consisting of nanoscale spherical grains in NCD and submicron polyhedral grains in SMCD. The filopodia extension and cell expansion results showed that cells on nanoscale topographies had faster filopodia extension and greater expansion area than on submicron topographies. Results indicated that substrate topography has an impact on cell filopodia extension and cell spreading, and NCD promoted filopodia extension and cell expansion better than SMCD.

We study the thermodynamic properties of solutions of the physically gelling poly(N-isopropylacrylamide-2-hydroxyethyl methacrylate) [poly(NIPPAm-HEMA)]. We construct its phase diagram and characterize its kinetics of phase separation. This material belongs to a class of thermosensitive, “smart” polymers, that exhibit complex phase behavior.The copolymer studied is liquid at low temperatures and undergoes phase separation near 28°C, with negligible dependence on concentration. Above the transition temperature we observe coexistence between a polymer-dilute solution and a gel. We show that, upon quick heating, liquid solutions form a homogeneous gel that phase separates (shrinks) from a dilute polymer solution. We find that the evolution of the gel volume fraction is well described by a double exponential decay, indicating the presence of two shrinking regimes in a close parallel to the behavior of chemically cross-linked gels. The first stage is characterized by quick water ejection. In the second stage, slower shrinking is observed associated with internal reorganization of the polymers that allows the creation of gel-forming contacts.

A new melt processing route for the fabrication of large grain Gd-Ba-Cu-O (GdBCO) bulk superconductors has been developed based on the use of novel GdBa4Cu3O8−δ (Gd-143) and GdBa6Cu3O10−δ (Gd-163) precursor compositions. The new processing route enables the fabrication of large single grains from precursor powders that contain high concentrations of Ba. The superconducting properties and microstructures of GdBCO single grains with extra Ba fabricated via this new processing route are reported. Most importantly, the possible formation of a new form of Gd1+xBa2−xCu3O7−δ solid solution (Gd-123ss) with x < 0 in single grains fabricated from the Ba-rich precursor are discussed for the first time based on the superconducting, chemical, and structural properties of the large GdBCO grains.