The electrochemical and optical properties of lithium phosphorous oxynitride (Lipon) thin films have been studied with an emphasis on the stability window vs. lithium metal and the behavior of the Li/Lipon interface. Impedance measurements made between -26 and 140°C show that Lipon exhibits a single, Lit-ion conducting phase with an average conductivity of 2.3 (±07) X 10' S/cm at 25°C and an average activation energy of E, = 0.55 0.02 eV. No detectable reaction or degradation was evident at the Li/Lipon interface, and linear sweep voltammetry measurements on three-electrode cells indicated that Lipon is stable from 0 to about 5.5 V with respect to a Li7Li reference. The complex refractive index of Lipon was measured by spectroscopic ellipsometry. Optical bandgaps of 3.45 and 3.75 eV were obtained from the ellipsometry data and from optical absorption measurements, respectively.

Polycrystalline films of LiCoO 2 deposited by radio frequency magnetron sputtering exhibited a strong preferred orientation or texturing after annealing at 700ЊC. For films thicker than about 1 m, more than 90% of the grains were oriented with their (101) and (104) planes parallel to the substrate and less than 10% with their (003) planes parallel to the substrate. As the film thickness decreased below 1 m, the percentage of (003)-oriented grains increased until at a thickness of about 0.05 m, 100% of the grains were (003) oriented. These extremes in texturing were caused by the tendency to minimize volume strain energy for the thicker films or the surface energy for the very thin films. Films were deposited using different process gas mixtures and pressures, deposition rates, substrate temperatures, and substrate bias. Of these variables, only changes in substrate temperature could cause large changes in texturing of thick films from predominately ( 101)-( 104) to (003). Although lithium ion diffusion should be much faster through cathodes with a high percentage of (101)-and (104)-oriented grains than through cathodes with predominately (003)-oriented grains, it was not possible to verify this expectation because the resistance of most cells was dominated by the electrolyte and electrolyte-cathode interface. Nonetheless, cells with cathodes thicker than about 2 m could deliver more than 50% of their maximum energies at discharge rates of 5 mA/cm 2 or higher.

Passive electric properties of biological tissues such as permittivity and conductivity are important in applied problems of electrical stimulation in studying of human electromagnetic fields interactions and development of diagnostic and therapeutic procedures. The current densities and pathways resulting from an applied electrical stimulus are dictated to a large extent by the relative permittivity and specific conductivity of biological tissues; energy absorption also depends on tissue properties. We briefly present some theoretical basis for the current conduction in biologic materials and factors affecting the measurement of tissue dielectric properties that need to be taken into account when designing the measurement procedure. Large discrepancies between the data reported by different researchers are found in the literature, which are caused by factors such as different measuring techniques used, the fact that tissue samples were taken from different species, circumstances under which the measurements were performed, and many others. Electric properties of some biological tissues are summarized and data ranges of values found for relative permittivity and specific conductivity in the literature are given. Finally, we present some applications of bioimpedance measurements.

Thin-film rechargeable lithium batteries with amorphous and crystafline LiCoO2 cathodes were investigated, The lithium cobalt oxide films were deposited by radio-frequency (RF) magnetron sputtering of an LiCoO2 target in a 3:1 Ar/02 mixture gas. From proton-induced -y-ray emission analysis (PIGE) and Rutherford backscatterung spectrometry (RBS), the average composition of these films was determined to be Li115CoO216 or, within experimental uncertainty, LiCoO2 + 0.08 Li20. The x-ray powder diffraction patterns of films annealed in air at 500 to 7 00°C were consistent with the regular hexagonal structure observed for crystalline LiCoO2. The discharge curves of the cells with amorphous LiCoO2 cathodes showed no obvious structural transition between 4.2 and 2.0 V, while the discharge curves of the cells with polycrystalline cathodes were consistent with a two-phase potential plateau at -3.9 V with a relatively large capacity. Two lower capacity plateaus were observed at ---4.2 and 4.1 V with the 600 and 700°C annealed cathodes; the -dq/dV peaks were broader and weaker for the 600°C annealed cathodes and were not present at all with the 500°C annealed films. The chemical diffusion coefficients of Li in the cathodes obtained from ac impedance measurements at cell potentials of -4 V ranged from ,1012 cm2/s for the as-deposited amorphous cathodes to --10 cm2/s for the films annealed at 700°C. The capacity loss on extended cycling of the thin-film cells varied with the crystallinity and thickness of the cathodes and with temperature. With the highly crystalline, 700°C annealed material, losses on cycling between 4.2 and 3.8 V at 25°C ranged from 0.0001%/cycle (>1O cycles) to 0.002%/cycle for cells with cathodes from 0.05 to 0.5 m thick.

An increased permeability of a cell membrane during the application of high-voltage pulses results in increased transmembrane transport of molecules that otherwise cannot enter the cell. Increased permeability of a cell membrane is accompanied by increased membrane conductivity; thus, by measuring electric conductivity the extent of permeabilized tissue could be monitored in real time. In this article the effect of cell electroporation caused by high-voltage pulses on the conductivity of a cell suspension was studied by current-voltage measurements during and impedance measurement before and after the pulse application. At the same time the percentage of permeabilized and survived cells was determined and the extent of osmotic swelling measured. For a train of eight pulses a transient increase in conductivity of a cell suspension was obtained above permeabilization threshold in low- and high-conductive medium with complete relaxation in <1 s. Total conductivity changes and impedance measurements showed substantial changes in conductivity due to the ion efflux in low-conductive medium and colloid-osmotic swelling in both media. Our results show that by measuring electric conductivity during the pulses we can detect limit permeabilization threshold but not directly permeabilization level, whereas impedance measurements in seconds after the pulse application are not suitable.