The influence of grain boundaries on the vibrational properties of nanoscale phononic crystals is studied with the help of molecular dynamics simulations. The low-frequency vibrational density of states of phononic crystals made from single crystal and polycrystalline silicon are derived from the simulations. The results show that the presence of grain boundaries leads to an increase of the density of states and a change of its peak structure at low frequencies. Calculations of the band structure of the model systems along one direction reveal that the grain boundaries affect the bands differently and in a non-uniform manner.

Thermoelectric composite alloys consisting of the β-FeSi2 matrix and SiO2 particles dispersion were fabricated by a so-called combined reactions sintering process using reduction and oxidation reactions between eutectoid Si decomposed from α-Fe2Si5 and added Fe-oxide powder. Typical microstructure may include some of residual eutectoid Si particles, intermediate product Fe2SiO4 particles, and/or remaining reduced Fe particles depending on the composite alloy compositions and the process conditions. Partitioning of doping element, n-type Co or p-type Mn, during the process plays an important role to control the optimum carrier concentration of the composite alloys. Thermal conductivity can be reduced, as expected, by the dispersion of SiO2 particles. The solubility of doping elements, Co, Mn, Al, and Ru was evaluated in α-Fe2Si5 at 1373 K and in β-FeSi2 at 1073 K being based on the isotherm determination. It is suggested that suitable dopants for the present process are n-type Co and p-type Mn, since they have sufficiently large solubility around 10 at% in both α-Fe2Si5 and β-FeSi2 phases.

MG/HK was introduced into CMOS technology and enabled scaling beyond the 45/32nm technology node. The change in gate stack from poly-Si/SiON to MG/HK introduced new reliability challenges like the positive bias temperature instability (PBTI) and stress induced leakage currents (SILC) in nFET devices which prompted thorough investigation to provide fundamental understanding of these degradation mechanisms and are nowadays well understood. The shift to a dual-layer gate stack also had a profound impact on the time dependent dielectric breakdown (TDDB) introducing a strong polarity dependence in the model parameter. As device scaling continues, stochastic modeling of variability, both at time zero and post stress due to BTI, becomes critical especially for SRAM circuit aging. As we migrate towards novel device architectures like bulk FinFET, SOI FinFETs, FDSOI and gate-all-around devices, impact of self-heating needs to be accounted for in reliability testing.

In this paper we summarize the fundamentals of MG/HK reliability and discuss the reliability and characterization challenges related to the scaling of future CMOS technologies.

Janus spheres, micron-sized silica spheres half-coated with platinum, move rectilinearly away from the platinum side in aqueous hydrogen peroxide. Upon self-assembling, these colloidal particles can form dimers with different conformations that exhibit both rectilinear and rotational modes of motion depending upon the relative orientation of each Janus sphere. At the micron length-scale, stochastic rotational Brownian dynamics is of the order of deterministic dynamics, and their coupling results in effective diffusion, in addition to passive translational diffusion. For dimers with rotary motion, the dynamic coupling leads to spiral trajectories for an ensemble average of the displacement vector.

In this work, we have investigated two aniline based squaraine molecules, DBSQ(OH)2 and DHSQ(OH)2, for their potential application in organic photovoltaics. These two squaraine molecules are only different in side chain length (i.e. butyl vs. hexyl). Yet, their solar cell properties are drastically different (PCE = 3.6% vs. 1.9%). We have further investigated the reason behind the superior performance of DBSQ(OH)2 in absorbance spectra, hole mobility characterization and transmission electron microscopy. The results show that DBSQ(OH)2 has a higher hole mobility (5.1×10-4 cm2/V•s vs. 1.4×10-4 cm2/V•s) and is able to mix well with the fullerene acceptor compared to DHSQ(OH)2. Our work shows clearly that the long solubilizing alkyl side chain might be detrimental for OPV performance and that shorter side chains with enough solubility have great value when designing small molecules.

Borosilicate glassy materials for immobilization of HLW from Russian WWER (PWR) spent nuclear fuel reprocessing were designed, synthesized in a resistive furnace, and characterized by XRD, SEM/EDS, and FTIR spectroscopy. Chemical durability was determined by PCT-A procedure and compared to EPA glass and reference data. The glasses with 20 and 25 wt.% waste loading were found to be X-ray amorphous, homogeneous and chemically durable. Glass network formally had a relatively low degree of connectedness that was increased due to embedding of different structural groups thus improving chemical durability. Boron is present primarily in trigonal oxygen coordination. The glasses with 40-45 wt.% waste loading contained minor britholite phase concentrating rare earth elements and as expected trivalent actinides. Glassy product with up to 30 wt.% waste loading was also produced by cold crucible inductive melting at the IPCE RAS lab-scale unit equipped with 56 mm inner diameter copper cold crucible and energized from a 10 kW/5.28 MHz generator. The product was composed of vitreous phase and minor britholite with average composition K0.39Sr1.99Fe0.16Nd5.50Si7.96O26.60.

The synthesis of a polyacetal-block-polyurethane copolymer was achieved which possesses the ability to depolymerize both selectively and in response to orthogonal stimuli, heat and pH. To utilize heat as a stimulus, poly(phthalaldehyde) (PPA) was used as a block of the copolymer, while poly(benzyl-4-hydroxymethylphenylcarbamate) (PPC) end-capped with a tert-butoxycarbonyl protecting group (Boc group) were explored for viability as a pH-responsive block. The stimulus-induced depolymerization was studied using nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and attenuated total reflectance infrared spectroscopy (ATR-IR). These techniques confirmed that the depolymerization event did not affect the nature of the neighboring polymeric block. Depolymerization kinetics were measured for various chain lengths of each block. The results are presented and discussed to explore the ability of these materials to depolymerize in a controlled manner depending on the magnitude of the stimulus, as well as the ability for the blocks to remain unaffected by the orthogonal stimulus. This work shows promise for the development of advanced coatings systems and drug delivery applications.

The continuous interest in the synthesis and properties study of materials has permitted the development of semiconductor oxides. Zinc oxide (ZnO) with hexagonal wurzite structure is a wide band gap n-type semiconductor and interesting material over a wide range. Chemically sprayed aluminium-doped zinc oxide thin films (ZnO:Al) were deposited on soda-lime glass substrates starting from zinc pentanedionate and aluminium pentanedionate. The influence of both the dopant concentration in the starting solution and the substrate temperature on the composition, morphology, and transport properties of the ZnO:Al thin films were studied. The structure of all the ZnO:Al thin films was polycrystalline, and variation in the preferential growth with the aluminium content in the solution was observed: from an initial (002) growth in films with low Al content, switching to a predominance of (101) planes for heavily dopant regime. The crystallite size was found to decrease with doping concentration and range from 33 to 20 nm. First-order Raman scattering from ZnO:Al, all having the wurtzite structure . The assignments of the E2 mode in ZnO:Al differ from previous investigations. The film composition and the dopant concentration were determined by Auger Electron Spectroscopy (AES); these results showed that the films are almost stoichiometric ZnO. The optimum deposition conditions leading to conductive and transparent ZnO:Al thin films were also found. In this way a resistivity of 0.03 Ω-cm with a (002) preferential growth, were obtained in optimized ZnO:Al thin films.

In the present work the kinetic growth is analyzed for a hard coating applied on a low carbon steel AISI 8620. A thermochemical treatment of bored with dehydrated paste at temperatures of 900, 950 and 1000 °C with a residence time of 2, 4, 6 and 8 h. The morphology and types of borides formed on the surface of the steel were evaluated by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The layer formed has a size of 20 to 113 μm which will be dependent on the process temperature, the treatment time and the alloy elements of the substrate. Hardness of 1493-1852 HV are presented for treatment times and temperatures established in this study. The kinetics of growth were determined and analyzed using a mathematical model of diffusion, evaluating the penetration of the biphasic layer that is determined as a function of the time and temperature of the thermochemical treatment (TCT). The results show the increase in the growth constants (k) with respect to the bored temperatures. The activity energy (Q) of the material AISI 8620 was also obtained.

Cerium incorporation in zirconolite glass-ceramic systems, consolidated by hot isostatic pressing, was investigated. Samples were formulated to target Ce incorporation on the Ca and / or Zr sites. Results show successful incorporation of Ce into the ceramic phase although complete waste digestion was not achieved. The formation of a Ce-bearing perovskite phase when targeting Zr substitution, was associated with reduction of Ce4+ to Ce3+. This study is part of preliminary work towards fabricating Pu-bearing glass-ceramic HIP samples.

In this paper, field effect transistors (FET) based on different kinds of non-graphene materials are introduced, which are MoS2, WSe2 and black phosphorus (BP). Those devices have their unique features in fabrication process compared with conventional FETs. Among them, MoS2 FET shows better electrical characteristics by applying a SiO2 protective layer; WSe2 FET is fabricated based on a new low pressure chemical vapor deposition (LPCVD) method; BP FET acquires high on/off ratio and high hole mobility by using a simple dry transfer method. Those novel non-graphene materials inspire new design and fabrication process of basic logic device.

Mesoporous titania films are prepared via the polymer-template assisted sol-gel synthesis at low temperatures, using the titania precursor ethylene glycol-modified titanate (EGMT) and the diblock copolymer polystyrene-block-polyethyleneoxide (PS-b-PEO). UV-irradiation is chosen as a low temperature technique to remove the polymer template and thereby to obtain titania sponge-like nanostructures at processing temperatures below 100 °C. After different UV irradiation times, ranging for 0 h to 24 h, the surface and inner morphologies of the titania films are studied with scanning electron microscopy (SEM) and grazing incidence small-angle x-ray scattering (GISAXS), respectively. The evolution of the band gap energies is investigated using ultraviolet/visible (UV/Vis) spectroscopy. The findings reveal that 12 h UV-treatment is sufficient to remove the polymer template from the titania/PS-b-PEO composite films with a thickness of 80 nm, and the determined bad gap energies indicate an incomplete crystallization of the titania nanostructures.

An aqueous two phase system (ATPS) is composed of binary hydrophilic polymers, for example, polyethylene glycol (PEG) and dextran, under an immiscible condition, and can also exhibit micro-segregation to produce cell-sized microcompartments like water-in-water microdroplets. Without membranes, interestingly, the microdroplet can serve as a micro-vessel (reactor) that contains various biochemical macromolecules like DNAs and proteins. We here present that PEG/dextran ATPS micro-segregation can provide an effective soft boundary to separate these biochemical macromolecules from the external environment. Trapped DNAs and proteins were concentrated inside such small spaces, and therefore, their interaction could be highly promoted to cause passive aggregation and controlled cross-linking if a certain cross-linker was added. We believe that the ATPS microdroplets might be associated with complicated structures and functions of living cells.

Electric-field noise from the surfaces of ion-trap electrodes couples to the ion’s charge causing heating of the ion’s motional modes. This heating limits the fidelity of quantum gates implemented in quantum information processing experiments. The exact mechanism that gives rise to electric-field noise from surfaces is not well-understood and remains an active area of research. In this work, we detail experiments intended to measure ion motional heating rates with exchangeable surfaces positioned in close proximity to the ion, as a sensor to electric-field noise. We have prepared samples with various surface conditions, characterized in situ with scanned probe microscopy and electron spectroscopy, ranging in degrees of cleanliness and structural order. The heating-rate data, however, show no significant differences between the disparate surfaces that were probed. These results suggest that the driving mechanism for electric-field noise from surfaces is due to more than just thermal excitations alone.

We have demonstrated the high yield and highly single wall selective synthesis of carbon nanotube forest grown using a MgO single crystal as a catalyst underlayer without any surface treatment. Such efficiency has not been previously reported using this underlayer system. Our investigation revealed that the growth ambient which contained no hydrogen but small amounts of water is essential for such efficiency. Evaluation of the growth kinetics by in-situ height monitoring revealed that the 350 μm tall forest with 65% single wall selectivity possessed a catalyst lifetime of about 5 minutes. Investigation by AFM, and XPS depth profiling revealed that this longer lifetime compared with as-deposited MgO can be attributed to the stability of the catalyst particle array with small size and high number density on MgO single crystal substrate. Shorter growth lifetime, when compared to the alumina underlayer system, resulted from an instability in the catalyst nanoparticle size and composition.

Novel approach to optimize quantum dot (QD) materials for specific optoelectronic applications is based on engineering of nanoscale potential profile, which is created by charged QDs. The nanoscale barriers prevent capture of photocarriers and drastically increase the photoelectron lifetime, which in turn strongly improves the photoconductive gain, responsivity, and sensitivity of photodetectors and decreases the nonradiative recombination losses of photovoltaic devices. QD charging may be created by various types of selective doping. To investigate effects of selective doping, we model, fabricated, and characterized AlGaAs/InAs QD structures with n-doping of QD layers, doping of interdot layers, and bipolar doping, which combines p-doping of QD layers with strong n-doping of the interdot space. We have measured spectral characteristics of photoresponse, photocurrent and dark current. The experimental data show that providing the same electron population of QDs, the bipolar doping creates the most contrasting nanoscale profile with the highest barriers around dots.

Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), it was shown for four different types of carbon that electrode treatments at negative potentials enhance the kinetics of VIV-VV and inhibit the kinetics of VII-VIII while electrode treatments at positive potentials inhibit the kinetics of VIV-VV and enhance the kinetics of VII-VIII. These observations may explain conflicting reports in the literature. The potentials required for activation and deactivation of electrodes were examined in detail. The results suggest that interchanging the positive and negative electrodes in a vanadium flow battery (VFB) would reduce the overpotential at the negative electrode and so improve the performance. This is supported by flow-cell experiments. Thus, periodic catholyte-anolyte interchange, or equivalent alternatives such as battery overdischarge, show promise of improving the voltage efficiency of VFBs.

In this paper, we report a first hand study of plasmon-enhanced photocurrent observed in hybrid nanostructures based heterojunction solar cell. The heterojunction solar cell was fabricated, using chemically synthesized narrow gap, IV-VI group semiconductor nanoparticles (PbS) of 3∼6nm diameter, wide gap semiconductor ZnO nanowires of 500nm∼1 μm length and ∼50nm diameter, and gold nanoparticles (∼5nm to 30nm), by spin-coating (∼20cycles) onto FTO glasses, in ambient conditions (25°C, 1atm). The synthesized nanostructures were characterized by XRD, UV-VIS absorption, SEM, TEM, solar simulator, etc. Nanostructures of variant sizes were integrated in to the heterojunction devices to study the effects on photocurrent and solar cell performance. The sizes, lengths, thickness of nanostructures were optimized to have best solar cell devices. The effects of fabrication conditions (such as growth temperature, growth time, anneal temperature, ligand treatments, in air or in N2, etc.) on device performance were also studied. The architecture of film stack, i.e., the positions of Au nanoparticles and PbS nanoparticles were also studied. It was confirmed that introducing Au nanopartiles with proper size would lead to the increase of photocurrent. The key challenges were to minimize the trap states and optimize the interface of nanostructures.

Fe-based amorphous and nanocrystalline soft magnetic alloys have been intensively researched for many applications, including high efficiency electrical distribution and power conditioning applications. New amorphous foils with a saturation magnetization of 1.63T and new nanocrystalline foils with saturation up to 1.9T have been developed. Often these new materials are not drop-in replacements for the conventional competing alloys and require significant changes in processing to be able to fabricate commercial devices.

Many simple diatomic and triatomic molecules such as N2 and CO2 have the potential to form extended “polymeric” solids under extreme conditions, which can store a large sum of chemical energy in its three-dimensional network structures made of strong covalent bonds. Diatomic nitrogen is particularly of interest because of the uniquely large energy difference between that of the single bond (160 kJ/mol) and that of the triple bond (954 kJ/mol). As such, the transformation of a singly bonded polymeric nitrogen back to triply-bonded diatomic nitrogen molecules can release nearly 5 times the energy of TNT without any negative environmental impact. In this paper, we will describe our recent research efforts to synthesize novel extended phases of isoelectronic systems of N2 and CO, as well as those of N2+CO mixtures to lower the transition pressures and enhance the stability of recovered products at ambient condition.