J. F. Currie

Electrical conduction in biotite micas

The direct current electrical conductivity tensor of biotitic phyllosilicates (mica) has been measured as a function of temperature, of electric field, and of chemical composition. It is found that conductivity depends exponentially upon iron impurity content, and upon electric field at high fields. The dependence upon temperature is more complicated. These results are best interpreted by a model in which mica is an isotropic Fermi glass in which electrical conduction takes places by nonadiabatic hopping of small polarons between iron sites in the crystal.

Material characterization of sputtered sodium-ion conductive ceramics for a prototype CO2 micro-sensor

Abstract RF magnetron sputtered Nasicon and sodium carbonate ionic conductive thin films (2000 A) have been characterized using physical-chemical methods such as Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). It is found that the overall chemical composition of sputtered and of laser deposited films is similar to that of the sputtering target. The Nasicon films show a sufficiently high ionic conductivity (0.36 S cm −1 at 360°C) for use in a prototype integrated CO 2 sensor with the dimensions of 3 × 4 mm.

Sputtered silicate-limit NASICON thin films for electrochemical sensors☆

Abstract We have demonstrated for the first time the production of silicate-limit NASICON [Na 4 Zr 2 (SiO 4 ) 3 ] in the form of thin films. The ionic conductivity was investigated as a function of the temperature. The best measured conductivity at 300°C is 0.5×10 -4 (S/cm) -1 . We report here on the evaluation of the mechanical properties sputtered NASICON thin films

A nuclear scattering evaluation of organometallic bonding in the adhesion of metallization to polymers

Abstract The nuclear profiling of the copper-and nickel-polyimide interfaces was carried out using both elastic recoil detection and Rutherford backscattering. Metallization was carried out both by evaporation and dc sputtering. These techniques revealed differences between metals but not between metallization processes. While both metals reacted with the surface, the copper-polyimide complex was more loosely held, permitting interdillusion. On the other hand, the strongly held nickel-polyimide complex maintained a sharp interface. The implication of these findings on practical adhesion is discussed.

Giant magnetoimpedance effect in soft and ultrasoft magnetic fibers

Soft NiFe‐Permalloy fibers and ultrasoft NiCo‐based amorphous fibers, having a circular cross section with 30–40 μm in diameter, have been cast by melt extraction. The fibers have been driven by a sinusoidal current with 20 mApp constant amplitude and frequencies from 0.1 to 100 MHz. Both longitudinal and transverse giant magnetoimpedance effects have been observed in these fibers. The longitudinal GMI effect at 30 MHz was 60% in ultrasoft (NiCo)70FeSiBMn fibers for a saturating field of about 7 kA/m. The same effect was found at 10 MHz frequency for Permalloy fibers for a larger saturating field (20 kA/m). The transverse GMI effect was smaller (≊35% for NiCo and ≊20% for NiFe), and showed a maximum at low frequency (3 MHz). The magnetic field responses of the fibers are quadratic. An inverse effect of 10%–30% was observed for both types of fibers in longitudinal as well as in transverse field responses at high current frequency and low field strength. All of the observed effects could prove to be very us...

Chemical characterization of plasma-polymerized hexamethyldisilazane by nuclear elastic recoil detection

Abstract Chemical composition profiles of plasma-polymerized hexamethyldisilazane thin films, deposited in microwave discharges, were measured by elastic recoil detection (ERD). The main fabrication variable during film deposition was the substrate temperature, which was varied from 25 to 650°C. Hydrogen, carbon and silicon concentrations and profiles to a depth of roughly 1 μm were measured by ERD. These concentrations were compared with results obtained by conventional chemical microanalysis, and agreement was found to be excellent. As in earlier work using other techniques, ERD confirmed the presence of a thin (approximately 50 nm) “oligomeric” layer at the free surface of the films. Erosive radiation damage caused by the probing ion beam on the carbon and hydrogen profiles was observed and investigated.

Pulsed laser deposition of nasicon thin films

Abstract We have deposited NASICON (Na SuperIonicCONductor) films of thicknesses ranging from 100 to 600 nm, by Pulsed Laser Deposition (PLD), onSiO2Si substrates. The deposition rates varied from6 × 10−3 to 0.08 nm/pulse depending on the conditions employed. XPS measurements show that all elements are transferred from the target to the substrate and that the thin film composition is very close to that of the target. Film morphology depends upon the laser energy density at the target. Films deposited at about 2 J/cm2 show a rough surface and a columnar structure. At lower energy density (400 mj/cm2), a smoother surface is obtained. Electrical measurements show good ionic conductivity, and that the films are suitable for the fabrication of electrochemical gas sensors.

Thermal Stress in Doped Silicate Glasses (B,P) Deposited by PECVD and LPCVD

Using an in situ stress measurement technique which measures stress as a function of annealing temperature, we have investigated the effect of phosphorous and boron doping of silicon dioxide glass films deposited by low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD). The stress at room temperature is σ i . Upon heating, it increases to a maximum, σ m , corresponding to a temperature T m , above which the stress is reduced to zero at a temperature T 0 . All these parameters plus the expansion coefficient are dependent on dopant concentrations and deposition technique.

Preparation and Chemical Investigation of Porous Silicon

We have begun a systematic study of the chemistry of light emitting porous Si (LEPOS) using X-ray photoemission spectroscopy and time-of-flight elastic recoil nuclear scattering. The relation of chemical composition to preparation parameters and its evolution with rapid thermal annealing in N 2 :H 2 and in vacuum were studied. The relation between chemical and photoluminescence properties and stability was investigated. The composition of LEPOS is extremely sensitive to preparation conditions and to subsequent treatment. The concentration of C and F in addition to Si, H and O vary with thermal treatment conditions and with time after preparation. However, preparation under the cleanest possible conditions increase both reproducibility and stability.

Density of states in amorphous silicon produced by microwave glow discharge

Capacitance‐voltage characteristics of a metal‐oxide‐amorphous silicon structure are analyzed in order to obtain the density of states N(E) in microwave glow discharge amorphous silicon films. Our measurement and deconvolution techniques reveal some structure in the density of states profile. At the midgap N(E) is found to be lower than 1017 cm−3eV−1.