We investigated the pressure dependence of the inductive coupled plasma (ICP) oxidation on the electrical characteristics of the thin oxide films. Activation energies and electron temperatures with different pressures were estimated. To demonstrate the pressure effect on the plasma oxide quality, simple N type metal-oxide-semiconductor (NMOS) transistors were fabricated and investigated in a few electrical properties. At higher pressure than 200mTorr, plasma oxide has a slightly higher on-current and a lower interfacial trap density. The on-current gain seems to be related to the field mobility increase and the lower defective interface to the electron temperature during oxidation.

We demonstrate the possibilities of plasma enhanced chemical vapor deposition (PECVD) and solid phase epitaxy to obtain germanium on silicon with excellent crystalline properties, even for very thin layers (< 100 nm). Amorphous germanium layers are deposited by PECVD on silicon substrates. Deposition of an amorphous layer, without the presence of crystalline seeds, is critical. Crystalline inclusions must be avoided to obtain high crystal quality and a smooth surface after crystallization. PECVD is well suited for deposition of amorphous layers because low temperature deposition and high growth rates are possible. Additional experiments with molecular beam epitaxy show that it is not mandatory to have hydrogen present inside the germanium layer to obtain highly crystalline germanium. Atomic hydrogen plays, however, an important role during deposition by lowering the surface adatom mobility and consequently increasing the disorder of the deposited layer. Synchrotron X-ray diffraction shows no germanium diffraction, indicating that the layer does not contain crystalline seeds. Crystallization can be performed at limited temperatures: Raman measurements show crystallization between 400 and 425 °C. Another important advantage of the proposed method is the scalability: germanium layers of larger diameter can be obtained by simply using larger silicon substrates.

Recently, few tens of nanometer thin films of TiOx have been intensively studied in applications for organic solar cells as optical spacers, environmental protection and hole blocking. In this paper we provide initial measurements of optical and electrical properties of TiOx thin films and it’s applications in solar cell and sensor devices. The TiOx material was made through hydrolysis of the precursor synthesized from titanium isopropoxide, 2-methoxyethanol, and ethanolamine. The TiOx thin films of thickness between 20 nm to 120 nm were obtained by spin coating process. The refractive index of TiOx thin films were measured using an ellipsometric technique and an optical reflection method. At room temperature, the refractive index of TiOx thin film was found to be 1.77 at a wavelength of 600 nm. The variation of refractive index under various thermal annealing conditions was also studied. The increase in refractive index with high temperature thermal annealing process was observed, allowing the opportunity to obtain refractive index values between 1.77 and 2.57 at a wavelength 600 nm. The refractive index variation is due to the TiOx phase and density changes under thermal annealing.

The electrical resistance was measured by depositing a thin film of TiOx between ITO and Al electrode. The electrical resistivity of TiOx thin film was found to be 1.7×107 Ω.cm as measured by vertical transmission line method. We have also studied the variation of electrical resistivity with temperature. The temperature coefficient of electrical resistance for 60 nm TiOx thin film was demonstrated as - 6×10-3/°C. A linear temperature dependence of resistivity between the temperature values of 20 – 100 °C was observed.

The TiOx thin films have been demonstrated as a low cost solution processable antireflection layer for Si solar cells. The results indicate that the TiOx layer can reduce the surface reflection of the silicon as low as commonly used vacuum deposited Si3N4 thin films.

Transition metal (Cr) and rare-earth (Dd, Dy) doped III-nitride semiconductor bulk layers and superlattice (SL) structures are grown on sapphire (0001) substrates and GaN (0001) templates by plasma-assisted molecular-beam epitaxy. For the GaGdN/GaN and InGaGdN/GaN SL and Si co-doped samples, enhancement of magnetization and magnetic moment are observed, suggesting the carrier-mediated ferromagnetism. Low temperature growth of GaGdN can increase the Gd concentration and magnetization. Results for the Dy-doped GaN as well as the GaCrN/AlN/GaCrN tunnel magneto-resistance (TMR) diodes are also described.

Electrical conduction in Fe, Pd, Nb, W and Mo cluster-assembled films was investigated in-situ, during their growth by supersonic cluster beam deposition. We observed for clusterassembled films resistivity values several orders of magnitude larger than corresponding bulk, as well as an increase of resistivity by increasing the film thickness, in contrast to the behaviour of atom-assembled metallic films. This suggests that nanoscale morphology arising by growth dynamics of cluster-assembled films, such as the minimal cluster-cluster interconnection and the evolution of surface roughness with thickness, may play a crucial role in the observed behaviour. Theoretical models based on non-isotropic 3D distributions of clusters into the film would help for a deeper understanding of the behaviour of cluster-assembled films compared to atomassembled ones. Benefits are expected in the technological field of devices performing electrical read-out on active nanostructured layers, as in the case of chemoresistive sensors.

This paper presents results for the conductivity of BaCe0.85Y0.15O2-δ (BCY15) measured by electrochemical impedance spectroscopy in wet hydrogen and in Air, as well as test results from the application of the material in a new dual membrane fuel cell configuration (“IDEAL Cell”), in which the water is produced and evacuated through a separate chamber. The conductivity of dense BCY15 in wet hydrogen atmosphere at 700 °C is 2.0 10-2 S/cm. The measured values in air are of the same order. Preliminary tests of the material in the new cell design, where the three types of conductivity (protonic, oxide ion and mixed) are used in different cell compartments, are successfully performed.

We describe a near perfect broad band absorber based on a laterally nanostructured multilayer material. We present calculations of the structure that demonstrates over 99% absorption of the 500 K black body spectrum. We also show the ability to manufacture an anti-reflective layer using a nanostructured metamaterial which allows us to tailor the index of refraction using effective medium theory. The absorber can be adapted for use in any frequency range and any source type. These materials may have applications in energy harvesting and scattered light control.

We investigated the resistive switching behavior of WOx films. WOx was obtained from the thermal oxidation of W thin layers. The parameters under investigation were the influence of the temperature (450-500 °C) and time (30-220 s) used to obtain the WOx on the resistive switching characteristics of Si\W\WOx\Metal_electrode ReRAM cells. The metal top electrodes (TE) tested were Pt, Ni, Cu and Au. The elemental composition and microstructure of the samples were characterized by means of elastic recoil detection analysis (ERD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray reflectivity (XRR).

Electrical measurement of the WOx-based memory elements revealed bipolar and unipolar switching and this depended upon the oxidation conditions and TE selected. Indeed, switching events were observed in WOx samples obtained either at 450 °C or 500 °C in time windows of 180-200 s and 30-60 s, respectively. Pt and Au TE promoted bipolar switching while unipolar behavior was observed with Ni TE only; no switching events were observed with Cu TE. Good switching characteristics seems not related to the overall thickness, crystallinity and composition of the oxide, but on the W6+/W5+ ratio present on the WOx surface, surface in contact with the TE material. Interestingly, W6+/W5+ ratio can be tuned through the oxidation conditions, showing a path for optimizing the properties of the WOx-based ReRAM cells.

A novel rapid and easy-to-use method for patterning surfaces on large scale is described. Micro-patterns were created by direct contact of trypsin-functionalized poly(dimethylsiloxane) (PDMS) stamps with poly-L-lysine (PLL) layer adsorbed on silicon surface. The catalytic process does not involve ink transfer and thus lateral diffusion is avoided. As a result duplication of the stamp pattern is highly enhanced comparatively to standard microcontact printing procedure where PLL is used as ink and transferred on silicon surface. Patterning was revealed by fluorescence microscopy and atomic force microscopy (AFM). Adsorption on the patterned surfaces of cellulose nanocrystals was investigated as an example of application.

A heterophase polydomain structure has been recently discovered in BiFeO3 epitaxial ferroelectric films, which provides large electromechanical responses. In this work, the formation of such a microstructure is explained by theory of elastic domains. The thermodynamics of the heterophase polydomain microstructure is analyzed to predict the equilibrium volume fraction of domains at different film-substrate lattice misfits. Extrinsic mechanical and piezoelectric properties are discussed for the heterophase polydomains. It is shown that an applied electric field, which increases electrostatic interaction between domains, may lead to dramatic increase of piezo response. The results of this work are in good agreement with experimental data for BiFeO3.

The refractory element Ta was added to L12-type Ni3(Si,Ti) intermetallic alloys in order to substitute for Ti. The microstructure and the mechanical properties of the alloys were investigated as a function of the Ta content. All the alloys were doped with 50 wt.ppm boron to suppress intergranular fracture. The alloys containing up to 5 at.% Ta showed an L12 single-phase microstructure, while the alloys containing more than 5 at.% Ta exhibited a two-phase microstructure consisting of Ni3Ta particles in the L12 matrix. At room-temperature (RT), the hardness of the alloys with the L12 single-phase microstructure increased with increasing Ta content due to solid solution hardening of Ta. RT yield stress (0.2% yield strength) and tensile ultimate strength of the alloys with the L12 single-phase microstructure increased with increasing Ta content keeping a high level of tensile elongation. At high-temperature (HT), the positive temperature dependence of hardness was observed in all the alloys, irrespective of Ta addition. HT hardness was also enhanced by the addition of Ta. It was consequently demonstrated that Ta is a remarkable solid solution hardening element in the Ni3(Si,Ti) alloys.

For many engineers and technologists, their only exposure to materials engineering principles occurs within a single fundamentals course. Within that course, the students must conceptualize a wide variety of interdisciplinary topics drawn from chemistry, physics, engineering, and mathematics. Often, the students consider this fundamentals course challenging because it is likely that this is the first time that they are to develop understanding in such an interdisciplinary environment. Research studies in engineering education, which are based in social and cognitive constructivism, indicate that students build scaffolds from existing cognitive structures to new information when the students are able to make connections to their existing knowledge and experiences. It is also known that prior learning heavily influences this learning and that motivation plays a key role in the time that students devote to acquiring new knowledge. Research has also shown cooperative learning, understanding of individual student learning styles, and inductive teaching practices are important components that lead to improved Student Learning Outcomes (SLOs). The only way to truly understand effective practice is to implement constructively aligned strategies, problems, and concept learning opportunities, and then measure the SLOs. Additionally, an in-depth study of prior knowledge, conceptual understanding, and experiences is absolutely essential as key research questions are probed.

This paper describes research work underway at Western Washington University to understand how to improve SLOs in a fundamental materials engineering course by investigating students’ prior knowledge and conceptual understanding, measuring individual learning styles, measuring the effectiveness of different constructively aligned course modules based upon ‘WHERETO” principles with collaborative problem sets or design problems, investigating the effect of pre-exam quizzing, measuring term-long conceptual gains, and developing Information Communication Technology (ICT) enabled applications to support and enhance student learning. Future investigations will probe how more personalizable instruction that allows for student differences might be accomplished with ICT applications, especially for large lecture classes.

We report on novel liquid crystals with extremely large flexoelectric coefficients in a range of ultra-fast photonic modes, namely 1) the uniform lying helix, that leads to in-plain switching, birefringence phase devices with 100 μs switching times at low fields, i.e.2-5 V/μm, and analogue or grey scale capability, 2) the uniform standing helix, using planar surface alignment and in-plane fields, with sub ms response times and optical contrasts in excess of 5000:1 with a perfect optically isotropic or black “off state”, 3) the wide temperature range blue phase that leads to field controlled reflective color, 4) chiral nematic optical reflectors electric field tunable over a wide wavelength range and 5) high slope efficiency, wide wavelength range tunable narrow linewidth microscopic liquid crystal lasers.

A tensile test procedure that accommodates specimens with gage section 25 μm thick, 70 μm wide and 360 μm long was developed and demonstrated. The instrumentation and technique were adapted from those previously developed and used to test thin films, by increasing both the force capacity of the load cell and the stiffness of the pull rod. Specimens with bow-tie geometry were fabricated by photolithography from nominally 25 μm thick full hard stainless steel 302 foil. A silicon test frame fabricated by bulk micromachining techniques included tapered grips in the form of recesses in its top surface that accepted and retained the specimen grip sections. One grip was on the fixed outer portion of the frame. The other grip was on a plate suspended in the center of the frame by long slender silicon beams. Force was imposed on this plate by pin loading. The force was measured by use of a custom load cell. The displacement was measured by sub-pixel digital image correlation to surface features on the two ends of the gage section, applied to images with a resolution of approximately 0.8 μm per pixel. Yield and ultimate strengths and elongation values consistent with vendor-provided information were obtained. The values of Young’s modulus were scattered but within the range of expected behavior for the specimen material.

Refractory Metal-Intermetallic Composites (RMICs) based on the Nb-Si system have been considered as candidates for the next-generation high temperature materials (i.e. >1200°C). Ti, Cr and Hf have been shown to have beneficial effects on the oxidation resistance and mechanical properties of Nb-Si alloys. The present study has determined phase equilibria in the Nb-rich region of the Nb-Si-Ti-Cr-Hf system via the Calphad approach. The alloying effects of Cr and Hf on the microstructure of Nb-Si-Ti alloys are understood based on isothermal sections, liquidus projections, and solidification curves that were calculated from the thermodynamic models of the Nb-Ti-Si-Cr-Hf system developed in the present study. This work provides important guidelines on the development of new Nb-Si-Ti-Cr-Hf alloys.

We propose a phototransistor geometry that incorporates silicon nanowires (SiNW) in the device channel. A set of two gates controls the charge flow inside the NW. This improves the device photo-response more than 10x when compared with a single gate phototransistor, leading to a photo-responsivity of greater than 104(A/W), while the dark properties of both devices are similar.

In this work we investigate theoretically the effects imposed by plasmonexcitations in spherical metallic nanoparticles (MNPs) on the rate of energytransfer in peridinin-chlorophyll-protein (PCP) complex reconstituted withboth chlorophyll a (Chl a) and chlorophyll b (Chl b). This light-harvestingcomplex is unique since it features efficient energy transfer both fromhigher-lying Chl b to lower-lying Chl a aswell as in the opposite, less energy-favorable direction. The results ofcalculations show that the Förster energy transfer rate decreases with aMNP-PCP distance changing from 2 to 144nm, while the energytransfer from Chl a to Chl b remains lessefficient at all distances. We conclude that plasmon excitations allow forcontrolling the energy transfer between Chls, as well as the excitationdistribution between two spectrally distinguishable Chls within thereconstituted PCP complex.

This work addresses the paucity of roughness measurements by reporting on roughness parameters in uniaxial strained Si beams relevant for state of the art MOSFETs, nanowire and MEMS devices, with varying degrees of strain. Roughness is characterized by high resolution AFM and strain is characterized by Raman spectroscopy. Microstructures comprising a silicon nitride actuator are used to induce a wide range of stress levels in Si beams. The microstructures also allow the comparison of surface evolution in the strain direction (along the Si beam) compared with the unstrained direction (across the Si beam). A gradual reduction in rms roughness amplitude and increase in roughness correlation length in the direction of the applied stress are found for increasing values of strain. In contrast, surface roughness in the direction perpendicular to the applied stress remained largely unchanged from the unstrained initial state.

Statistical studies involving the fracture behavior of coatings can play an important role in the mechanical analysis of films employed in the hard coating industry. In this study, Nanoimpact tests using a cube corner indenter were carried out in various CrAl(Si)N coatings for the quantitative assessment of properties of coatings like non-catastropic failure time and catastrophic failure time. These parameters decrease in value as silicon is incorporated in coatings, showing that this addition results in a decrease in ductility. Scanning electron microscope images were taken to the analyzed coatings exhibiting the residual imprints after nanoimpact test that were correlated with the fracture behavior of CrAl(Si)N coatings.