In this work, Dopant Segregated Schottky Barrier (DSSB) and Schottky Barrier (SB) vertical silicon nanowire (VSiNW) diodes were fabricated on p-type Si substrate using CMOS-compatible processes to investigate the effects of segregated dopants at the silicide/silicon interface and different annealing processes on nickel silicide formation in DSSB VSiNW diodes. With segregated dopants at the silicide/silicon interface, VSiNW diodes showed higher on-current, due to an enhanced carrier tunneling, and much lower leakage current. This can be attributed to the altered energy bands caused by the accumulated Arsenic dopants at the interface. Moreover, DSSB VSiNW diodes also gave ideality factor much closer to unity and exhibited lower electron SBH (ΦBn ) than SB VSiNW diodes. This proved that interfacial accumulated dopants could impede the inhomogeneous nature of the Schottky diodes and simultaneously, minimize the effect of Fermi level pinning and ionization of surface defect states. Comparing the impact of different silicide formation annealing using DSSB VSiNW diodes, the 2-step anneal process reduces the silicide intrusion length within the SiNW by ~ 5X and the silicide interface was smooth along the (100) direction. Furthermore, the 2-step DSSB VSiNW diode also exhibited much lower leakage current and an ideality factor much closer to unity, as compared to 1-step DSSB VSiNW diode.

Multiwalled carbon nanotube (MWCNT)/Nylon-6 nanohybrids were prepared by in situ polymerization under microwave irradiation. The effect of time and power of irradiation on the surface conductivity of the nanohybrid was studied. It was observed that the resistivity increases with irradiation time at low microwave power (200W). On the other hand, at high power (600W) an opposite behavior was observed. And at intermediate power (400W) the resistivity was independent of the irradiation time. Resistivity values range from 102 to 101 Ω/sq. This behavior was associated with the polymer nanocoating covering the surface of the carbon nanotubes.

Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics were fabricated by mixed-oxide route. The compositions along morphotropic phase boundary were investigated. Dielectric properties and piezoelectric coefficient were measured. The maximum relative permittivity is 33600 found in the (PIN-PT)x(PMN-PT)1-x ceramics with x = 0.1 at 167 °C. When increasing the amount of Pb(In1/2Nb1/2)O3, the piezoelectric coefficient of the ceramics decreases but the phase transition temperature increases. The selected-area electron diffraction patterns show the pseudo-cubic perovskite symmetry. Diffuse scattering is found in the diffraction pattern taken at higher order zone axis. Transmission electron microscopy study shows that the morphology of ferroelectric/ferroelastic domains is neither tetragonal nor rhombohedral configuration.

The oxidation and diffusion of Molybdenum layer sputter-deposited on 2μm CVD diamond grown on silicon substrate has been studied. The Mo layer was protected by refractory metal silicide barrier layer. The samples were annealed in air ambient at 500°C over 30 hours. The oxidation of the samples was monitored with Rutherford Backscattering Spectroscopy (RBS). The effect of reactive sputtering of refractory silicide target in argon-nitrogen gas mixture (5% nitrogen by flow rate) on the barrier characteristics was investigated. The sheet resistivity of the barrier layer on SiC substrates as a function of annealing time in air at 500°C is reported. The surface structure and morphology of the refractory silicide films was determined with X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).

We have fabricated a ferroelectric resistive switching device of Pt/Bi1-δFeO3 (BFO)/SrRuO3 (SRO) in which the conductivity of BFO layer was controlled by changing the Bi-deficiency concentration. The devices showed a bipolar-type resistive switching effect, i.e., zero-crossing hysteretic current–voltage (I–V) characteristics. In addition, the I–V characteristics in both high and low resistance states are nonlinear, which can avoid a read-error problem in a passive crossbar memory array. Resistive switching characteristics measured in pulse-voltage mode revealed that the resistance values in low resistance states vary with the amplitude and duration time of the pulsed-voltage stresses, indicating possibility of multilevel switching. On the basis of the experimental results, we discuss the potential of the Pt/BFO/SRO device for application in a large-capacity nonvolatile memory.

To evaluate the microstructures and mechanical properties in cross-roll rolled pure copper, comparing with conventionally rolled materials, this work was carried out. Pure copper (99.99 mass%) sheets with thickness of 5 mm were cold rolled to 90% thickness reduction by cross-roll rolling (CRR) and subsequently annealed at 400 °C for 30 min. Also, to analyze the grain boundary character distributions (GBCDs), electron back-scattered diffraction (EBSD) technique was employed. As a result, the cold rolled and annealed materials consisted of significantly refined grains than that of the initial material (100 μm). Especially, the CRR processed material showed more refined grain size (6.5 μm) in average than that (9.8 μm) of conventional rolling (CR). These grain refinements directly affected an increase in mechanical properties. Furthermore, the texture development in CRR processed material, in which <112> grains were densely distributed in the normal direction (ND), was more effective to enhance the yield strength.

Embedded Si nano-particles of average size around 5nm were synthesized in an amorphous Si matrix by two stage ion implantation processes. It has been observed that amorphous Si (a-Si) layers were recrystallized using 50 MeV Au ions with enhanced regrowth rate with activation energy in the range of 0.29 eV. During the crystallization process Si nanocrystals were formed in the a-Si layers due to sudden quenching of the molten tracks created by MeV Au ions. The recrystalizations were confirmed by Rutherford backscattering spectrometry-Channeling (RBSC) technique. The structural modification and nanocluster creation that emerged during recrystallization process was observed in high-resolution transmission electron microscopy and photoluminescence (PL) spectroscopy. The PL emission was observed over a broad band of 2.8 – 3.4 eV and centered at 3.25 eV. The Si nano-crystal formation can be explain by a mechanism combining the melting within the ion tracks by thermal spike process and the subsequent recrystallization nucleated from the crystalline sides at the interface.

Nowadays, aeronautic and aerospace are the more demanding sectors for shape memory alloys (SMA) after the bio-medical one. In particular the interest has been recently focused on very high temperature SMA, which would be able of working as sensors and actuators in the hot areas of the engines and exaust devices.

In the present work we undertook a study of the Ru-Nb SMA Intermetallics, which undergo two succesive martensitic transformations around 1050 K and 1180 K respectively, depending on composition. This study has been focused on measurements of internal friction spectra and dynamic modulus variation up to 1700 K, which have been carried out in a sub-resonant torsion mechanical spectrometer.

The internal friction and dynamic modulus have been studied as a function of the heating-cooling rate and the frequency in order to compare experimental behaviour with theoretical models for martensitic transformations. In addition to the internal friction peaks linked to both martensitic transformations we have also observed a complex relaxation process around 950 K, which seems to be linked to the interaction of the martensite interfaces with structural defects. An analysis and discusion of the potential microscopic mechanisms are also presented.

We report a technique that can, in principle, selectively convert SiC into graphene at any location and in any size or shape, limited only by the ability of the available lithographic techniques. This technique relies on our discovery that, at ambient condition, a laser beam can convert SiC into graphene layers at the illuminated site, and the conversion can be realized in two ways. One can pattern the SiC film, which is already grown on a Si wafer, with desirable features and then illuminate the SiC film with the laser, or simply “write” the graphene features directly onto the unpatterned SiC film with the laser. Alternatively, one can pre-pattern the Si substrate to achieve selective growth of SiC, then perform the laser conversion. We have demonstrated the feasibility of both approaches. Fullerene (C60) was used to grow a thin SiC film on a Si (111) substrate using molecular beam epitaxy (MBE) at 700-800 oC. The results are verified by various structural, chemical and optical characterization techniques. This work yields the possibility of fabricating graphene based (electronic) nanostructures or superlattices, photonic crystals, and integrated electronic and optoelectronic devices on a large Si wafer.

In d-wave unconventional superconductors, superconducting Cooper pairs are believed to be formed via magnetic fluctuations. In fact, the superconducting transition temperature Tc roughly correlates with the antiferromagnetic spin fluctuation energy in d-wave unconventional superconductors including high Tc cuprates. In addition to this correlation, the superconducting pairing symmetry and the magnetic anisotropy of the normal state are found empirically to be strongly correlated in f-electron unconventional superconductors having crystallographic symmetry lower than cubic. In antiferromagnetic systems, unconventional superconductivity appears with singlet (d-wave) pairing for cases of XY anisotropy. In contrast, in ferromagnetic systems, unconventional superconductivity with triplet (e.g. p-wave) pairing appears for cases of Ising anisotropy. In this report, the d-wave case is addressed, the origin of XY anisotropy is discussed in terms of the orbital character; and the angular momentum character jz for each piece of Fermi surfaces is determined.

Localized heating of metals and alloys using a focused laser beam in ambient atmosphere produces dielectric oxide layers that have characteristic optical appearances including different colors. Nanoindentation probed the deformation and fracture of laser-fabricated oxides on 304L stainless steel. Conductive nanoindentation measured electrical contact resistance (ECR) of the same colored oxides indicating a correlation between laser exposure, conductance during loading, current-voltage (I-V) behavior at constant load, and indentation response. Microscopy and X-ray diffraction examined the microstructure and chemical composition of the oxides. Combining techniques provides a unique approach for correlating mechanical behavior and the resulting performance of the films in conditions that cause wear.

Natural pozzolans are supplementary cementitious materials (SCMs) that may be used to improve the properties of mortar and concrete, through the formation of additional hydration products by pozzolanic action. Water reducers (WR) play a main role in high performance concrete in terms of durability, strength and surface finishing. A first optimization of constituent proportions in paste and/or mortar is convenient to assess the compatibility between the WR and the cementitious materials. The compatibility between cement and WR may be affected by SCMs, as they can also interact with the molecules of the admixture. However, the practical implication may be variable. This paper deals with the influence of different types and dosages of WRs in mortars made with pozzolanic Portland cement. Both medium and high ranges WRs have been used. Mortar fluidity has been tested by the spread and the slump tests. Results show different fluidizing capacities of WRs, among which polycarboxylate-based WR was the most compatible with the pozzolanic cement.

Electrical transport properties in ultrathin NdNiO3 films grown on single crystal LaAlO3(001) substrate were characterized. Films with thicknesses ranging from 0.6 nm to 12 nm were grown using a pulsed laser technique. Four probe resistivity as a function of temperature measurements indicated a strong dissipation of strain effects from 0.6 nm to 6 nm as well as the presence of defects in the 12 nm sample. A proposed mechanism of kinetically stable glassy phase formation explains the time dependence of the resistivity in both cooling and heating cycles.

Cardiac disease is the main cause of death in men and women in México and the U.S.A. When heart muscle suffers an injury, i.e. cardiac infarction, the tissue dies and is replaced by a fibrotic scar that does not allow for normal organ function. To alleviate scar tissue, the objective of this work was to investigate and synthesize polyurethane ureas from polycaprolactone diol, methylene bis(4-cyclohexilisocyanate), and butanediamine with different hard segment contents, characterize them, and prove their biocompatibility by seeding SCA-1+/CD45- cardiac progenitor cells obtained from mice cardiospheres. Ultimately, this work aims to explore how polyurethane urea elastomers can aid in therapeutic cardiac tissue regeneration.

The challenges associated with meeting 20nm technology requirements for better Cu CMP process uniformity and lower defectivity have been studied. Required improvements in uniformity were obtained through platen process optimization along with evaluation & selection of specific Cu slurries and pads and their performance reported. The principal factors influencing defect formation, including Cu barrier metallurgy, interconnect pattern density and process queue times were studied. Specific new post CMP clean chemistries were evaluated to assess their capability to suppress defect formation and their performance reported. The trade off between uniformity and defect suppression as a function slurry, pad and post Cu CMP clean chemistry is described.

Magnesium hydroxide (Mg(OH)2) nanoparticles were synthesized by chemical precipitation synthesis method. The influence of the nano-sized Mg(OH)2 on the structural modification was evaluated. The formation of Mg(OH)2 crystals were evaluated by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The particle size and morphology of Mg(OH)2was confirmed by high resolution transmission electron microscopy (HRTEM). The crystalline structure of nanoparticles was characterized by fast Fourier transform (FFT) and X-Ray diffraction (XRD), like analytical tools.

Nata-de-coco (bacterial cellulose) forms nanowhiskers with a larger aspect ratio owing to higher crystalline, longer and thinner microfibrils than those formed by cellulose from other sources. Suspension of these nanowhiskers undergoes transition from isotropic to liquid crystalline phase at a very low concentration of about 0.05 wt% in water and through a broad biphasic region. Formation of nematic as well as cholesteric phase is presented in this work.

In this paper, we compare degradation modes and failure mechanisms of different AlGaN/GaN HEMT technologies. We present data concerning reverse-bias degradation of GaN-based HEMTs, which results in a dramatic increase of gate leakage current, and present a timedependent model for gate degradation. Some of the tested technologies demonstrated to be immune from this failure mechanism up to drain-gate voltages in excess of 100 V. When this was the case, the main failure mode consisted of drain current degradation during on-state tests, resulting from charge trapping in the gate-drain access region attributed to hot-electron effects. Finally, the use of diagnostic techniques such as electroluminescence microscopy and Deep Level Transient Spectroscopy for the identification of failure modes and mechanisms of GaNbased HEMTs is reviewed. Concerning reverse-bias degradation of GaN-based HEMTs, we demonstrate that, (i) when submitted to reverse-gate stress, HEMTs can show both recoverable and permanent degradation. (ii) recoverable degradation consists of a decrease in gate current and threshold voltage, which are ascribed to the simultaneous trapping of negative charge in the AlGaN layer, and of positive charge close to the AlGaN/GaN interface. (iii) permanent degradation is manifested by the generation of parasitic leakage paths. Time-dependent analysis suggests that permanent degradation can be ascribed to a defect generation and percolation process. Results supports the existence of a time to breakdown for HEMT degradation, which significantly depends on the stress voltage level. On the contrary, AlGaN/GaN technologies which were found to be resistant to gate degradation (off-state critical voltage larger than 100 V for a 0.25 um gate device) were subjected to on-state tests at different gate and drain voltage levels. All tests showed a non-recoverable degradation of electrical parameters (drain saturation current, threshold voltage and on-state resistance) and electroluminescence signal EL, with a strong dependence on the EL value of the bias point, and a negligible dependence of temperature. Once verified that EL intensity represents a reliable estimate of channel hot electron effects, we attributed the degradation to hot electron trapping in the gate-drain access region. Using EL intensity as a measure of the stress acceleration factor, we derived an acceleration law for GaN HEMT hot electron degradation similar to the one already demonstrated for GaAs devices.

Aging effects of as-deposited and passivated slanted columnar thin films from cobalt determined by generalized ellipsometry within the visible spectral region are reported. Slanted columnar thin films have been grown by glancing angle electron beam deposition and sub-sequently coated with Al2O3 by an atomic layer deposition process. An anisotropic Bruggeman effective medium approximation developed for highly ordered three dimensional metal nanostructures is employed to analyze spectroscopic Mueller matrix ellipsometry data. Our model approach allows for determination of biaxial optical and structural properties as well as fractions of multiple film constituents. While the optical properties of the uncoated film change over time, the alumina passivation layer prevents oxidation in air and therefore aging effects; however, it affects the intrinsic bulk-like Co optical properties.

Light-emitting diodes (LEDs) based on p-GaN/ZnO heterojunction were fabricated. GaN was deposited on sapphire using metal-organic chemical vapor deposition (MOCVD), and two kinds of ZnO i.e. ZnO thin film deposited by sputtering and ZnO nanorods (NRs) grown by hydrothermal method were used as n-type layer respectively. MgO film with the thickness around 10 nm was deposited by electron-beam deposition to act as an interlayer between GaN and ZnO. Photoluminescence, electroluminescence and I-V curves were measured to compare the properties of GaN based heterojunction LEDs with different architectures. The existence of MgO interlayer as well as the morphology of ZnO obviously influenced the electrical and optical properties of GaN based LEDs. The effect of MgO interlayer on ZnO growth, properties and I-V curves and emission spectra of LEDs is discussed in detail.