Electronic textiles (or e-textiles) have a wide range of potential applications in wearable computing and large-area applications, including medical monitoring, assistance to the disabled, and distributed sensor networks. We aim to integrate thin-film electronics directly into clothing during the weaving process. First, thin-film devices are fabricated on plastic substrates. Individual devices are separated by cutting the substrate into stripes which can then be woven into a textile. Devices on stripes need to survive high applied bending strains during weaving. As a first building block, we used atomic layer deposition (ALD) at a maximum temperature of 150oC to fabricate bottom-gate zinc-oxide thin-film transistors (TFTs) with a 25nm-thick Al2O3 gate dielectric, and a 15nm-thick ZnO semiconducting layer on 50μm-thick Kapton E substrates. These TFTs had average mobilities of 12cm2/Vs, threshold voltages around 1V and subthreshold slopes around 250mV/decade. However, after applying a tensile bending diameter of 1cm to the TFTs, ~80% of TFTs fail due to cracking of the brittle device layers. We studied causes of failure and investigated patterning holes in the brittle layers to prevent crack propagation though the channel. This reduced TFT failure to ~45% under the same applied bending conditions. In this paper, we will discuss failure mechanisms in our standard TFT structure when high tensile bending strains are applied and how the device structure was adjusted to decrease TFT failure.

Highly crystalline superparamagnetic Fe3O4 nanoparticles coated by poly-vinylpyrrolidone (PVP) were prepared by simultaneous thermal decomposition of ferrous and ferric inorganic salts in polyethylene glycol (PEG) with molecular weight 200. The magnetic particles have a diameter in the range of 8-15 nm, and after exchange with citric acid diammonium salt, they transform into very stable super hydrophilic colloidal solutions. The presence of magnetite phase was confirmed using powder X-rays diffraction (XRD) and Mössbauer spectroscopy, while thermogravimetric analysis and FT-IR spectroscopy confirmed the presence of PVP or citrate anions on the nanoparticles surface. The magnetic properties revealed superparamagnetic behavior, with the composite material showing a saturation magnetization up to 57 emu/g. The Fe3O4 nanoparticles prepared by this modified polyol process are suitable for biomedical applications because of the biocompatibility of citrate anions. Magnetic hyperthermia experiments in neutral water solutions shows that the particles induce fast heating rates with specific absorption rate (SAR) values which reached 57.53 W/gFe, when the concentration of iron is 11.2 mgFe/ml.

We report ac electrical transport in the metallic ferromagnet La0.7Sr0.3MnO3. Both ac resistance (R) and reactance (X) were measured as a function of temperature (T= 400-100 K), frequency of the ac current (f = 100 kHz – 20 MHZ) and external dc magnetic field (H = 0-100 mT) applied parallel to the current direction. It is shown that, while R(H = 0 T) decreases smoothly around the Curie temperature (TC) for f = 100 kHz, an abrupt increase followed by a peak close to TC occurs for f ≥ 500 kHz. The peak decreases in magnitude, broadens and shifts down in temperature with increasing values of H. The peak in R is completely suppressed under H= 100 mT resulting in a huge low-field ac magnetoresistance (R/R= -53 % for f= 2MHz) whereas the dc magnetoresistance only -31 % even at H = 7 T. While the reactance X(H = 0 T) also shows an abrupt increase at TC for f < 10 MHz, it decreases abruptly at TC for f ≥ 12 MHz. The magnetoreactance is largest (X/X= -47 %) at f = 100 kHz and it changes sign from negative to positive with increasing frequency. It is suggested that the observed huge ac magnetoresistance arises from decrease of magnetic permeability which enhances skin depth under a magnetic field. Our results indicate that the extraordinary sensitivity of the ac magnetoresistance to low dc magnetic fields can be exploited for device applications.

Sputter deposited YSZ thin films were studied for the application as electrolyte membrane in micro solid oxide fuel cells. A new micro-machined test structure was developed to test 200 μm fuel cell membranes that are integrated onto silicon substrates. The membranes are liberated by means of deep silicon dry etching from the backside, and both contacts are situated on the front side of the wafer. Annular Pt electrodes provide contacts to specific anode and cathode layers. Preliminary tests are reported for the situation without specific electrodes. At 450 °C, an OCV of 570 mV, and a maximal power of about 0.55 mW/cm2 is obtained. LaSrMnO electrodes deposited by pulsed laser deposition were evaluated by electrical impedance spectroscopy. The dense films yielded too high ASR values. Interestingly, these could be reduced by applying a DC bias voltage.

We prepared single-phase nickel ferrite nanoparticles separated by silicon dioxide using sol-gel method with tetraethyl orthosilicate (TEOS) as a precursor for SiO2. The magnetic properties are investigated by using SQUID-magnetometry over a broad temperature range (4.2 – 350 K), magnetic field (2–70,000 Oe) and frequency (0.1 – 1000 Hz) range. The particle size is in the range 8 – 12 nm. Exchange bias and spin disorder appear at the core-shell interface due to broken bonds on the surface. Disorder and core-shell interaction induces spin-glass freezing which is manifested by a low temperature peak in the AC susceptibility well separated from magnetic blocking peak. This low temperature peak is assigned to spin-glass freezing. The proof of spin-glass freezing is managed by zero field cooled/field cooled (ZFC/FC), frequency and DC field dependence of AC susceptibility, low temperature hysteresis loop and time dependent thermoremanent magnetization at different temperatures. All the measurements stated above signify blocking/unblocking at higher temperatures and surface spin-glass freezing at low temperatures. The aim of our work is to contribute to a better understanding of “spin-frozen” magnetic ferrite nanoparticles at diameters 8 – 12 nm which could be important in future for stabilizing the magnetic state of “core-shell”-structured nanomagnets.

SiOx nanowires can be grown via the vapor-liquid-solid growth mechanism using SiO vapor produced during the active oxidation of a Si substrate. The as-grown SiOx nanowire have a range of useful physical properties but can also be used as large surface area substrates for the growth of secondary materials. In this study we report the use of optically active impurities to grow and dope secondary nanowire structures, and the use of simple coating methods to enhance and extend the functionality of these unique nanowire substrates.

To successfully incorporate the highly spin-polarized material La0.7Sr0.3MnO3 (LSMO) into spin-based electronic devices it is essential to be able to control and tune the magnetic domain structure. In this work, we geometrically confine epitaxial thin films of LSMO into hexagons to examine the effect of magnetostatic and magnetic anisotropy energies on the domain formation. We find through careful choice of hexagon aspect ratio, crystalline direction, and substrate orientation, we can tune the magnetic domain formation to be single, two, six (flux closure), or other domain configurations.

Membrane separations are a key enabling technology for future energy conversion devices. Ionic transport membranes must have both proton and electronic conductivity to function as hydrogen separation membranes without an external power supply. A technical obstacle to material modification by compositional changes is that the hydrogen flux through a dense membrane is a function of both the proton ionic conductivity and the electronic conductivity. An alternative way to modify the materials conductivity without changing the ratio of the chemical constituents is by altering the microstructure. In this study, SrCe0.95Yb0.05O3 was produced by conventional mixed oxide bulk ceramic techniques and chemical solution routes self-rising approaches using urea as the leavening agent. In conventional ceramic processing routes, the perovskite phase was observed to form at temperatures near 1300oC, while solution techniques resulted in perovskite phase formation starting near 1000oC with complete phase transformations occurring at 1100oC. Thermogravimetric analysis (TGA) was conducted in various gas atmospheres resulting in bulk oxide route powders exhibiting a 0.6% weight loss at 800oC under a nitrogen environment as compared to chemically derived powders which displayed weight losses on the order of 3.4%.The increased weight loss observed in chemically derived SrCe0.95Yb0.05O3 is correlated with an increase in the number of electron charge carriers and results in elevated electronic conduction. This study will report on the development of structure property relations in the model proton conducting ceramic system SrCe0.95Yb0.05O3.

Monodispersed nickel oxide nanoparticles have been synthesized using solution combustion synthesis method. Size of the nanoparticles was controlled by varying different reaction parameters such as reaction temperature and reaction time. Structure and morphology of the nanoparticles were investigated using X-ray diffraction and transmission electron microscopy. BET surface area of 99.7 m2/g was obtained for the nanoparticles synthesized at 300 °C. A decrease in surface area was observed with increase in reaction temperature. The nanoparticles were compacted using spark plasma sintering technique at 950 °C and thermal conductivity was studied on compacted sample. Significant decrease in thermal conductivity was observed for nanoparticles in compared to their bulk counter-part.

Materials which possess electrical and magnetic coupling are of great interest for novel devices. Bi(Fe1-xCox)O3 (BFCO) material system was synthesized by solution route for various compositions and thin films were prepared by spin coating on Pt (Pt/Ti/SiO2/Si) substrates. Structural properties of the films were investigated by x-ray diffraction and Raman spectroscopy. X-ray diffraction patterns confirms intense (110) in BiFeO3 and Bi(Fe1-xCox)O3 with rhombohedra distorted perovskite structure without impure phase. Bi(Fe1-xCox)O3 films show week ferroelectric polarization and ferromagnetism at room temperature. Ferroelectric and ferromagnetic coupling could be attributed to the elimination of oxygen vacancies and increased stress in the crystal structure by partial replacement of Fe2+ ion by Co2+ ion.

Thin layers of indium tin oxide (ITO) were deposited onto glass substrates by RF magnetron sputtering with the pressure varying from 6 mTorr to 15 mTorr. The films were annealed in a reducing atmosphere at 500 °C for 30 minutes. Sheet resistance was determined by four-point-probe measurement. Resistivity, mobility, and carrier concentration were obtained by Hall effect measurements. Transmission of the films in the visible spectrum was determined by photospectrometry. The structure of the films was characterized by X-ray diffraction. X-ray photoelectron spectroscopy was used to determine the oxidation state of Sn, which was used to determine the fraction of active tin clusters. The effect of additional anneals was investigated. The results reveal that the lowest resistivity obtained was 1.69×10-4 -cm at 9 mTorr and the highest transmittance of 90% was obtained after a second anneal. However, the second anneal decreased the mobility and conductivity for high sputter pressures.