As feature sizes in integrated circuits approach 0.18 μm, problems with interconnect resistance-capacitance (RC) delay, power consumption, and crosstalk become more urgent. Integration of low-dielectric-constant (k) materials will partially mitigate these problems, but each candidate with k significantly lower than that of dense silica (k ∼ 4) suffers disadvantages. Current low-k commercialization emphasizes spin-on glasses (SOGs) and fluorinated SiO2 with k > 3, and a number of polymers are under development with k in the range of 2–3. These suffer from potential problems including thermal stability, mechanical properties, low thermal conductivity, and reliability. For some low-k materials, a protective liner covering the conductor is necessary. Although the material k is often cited, the value of practical concern is the effective k, which may be quite different because of this protective liner. As feature sizes shrink, the presence of the liner becomes more problematic and necessitates even lower k materials.Another approach employs nanoporous silica with k of ∼1–4. Porous silica has been classified as an aerogel (dried supercritically) or as a xerogel (dried by solvent evaporation). We use the term nanoporous silica since it captures the key material properties that may be independent of how the films are processed. The ultralow dielectric constant results from porosity incorporation. For a porous material, the dielectric constant is a combination of that of air (∼1) and of the solid phase. The variation of k with porosity (volume fraction of pores) appears in Figure 1.

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Photosensitized oxidations or reductions at p‐ and n‐type normalGaAs and normalInP semiconductor electrodes of aromatic species in aprotic solvents leading to electrogenerated chemiluminescence (ECL) are described. The energy of the irradiating light equal to the bandgap energy of the semiconductor and the electrical energy input couple to produce excited states which eventually produce emission at shorter wavelengths. Intense ECL is observed by alternately generating radical cations and radical anions at an illuminated semiconductor electrode with smaller potential excursions than required on metal (platinum) electrodes.

The Cr(III) complexes present in the acidified chromium solutions used in the iron-chromium redox energy storage system have been isolated and identified as Cr(H20)6 ~ and Cr(H20)sC1 § by ion-exchange chromatography and visible spectrophotometry. The cell reactions during charge-discharge cycles have been followed by means of visible spectrophotometry. The spectral bands were resolved into component peaks and concentrations of the Cr(III) species calculated using Beer's law. During the charge mode, Cr(H~O)sCt +2 is reduced to Cr(H20)sCF, and during the discharge mode Cr(H20)~C1 § is oxidized back to Cr(H~O)sC1 § Electrode potential measurements also support this interpretation. Hysteresis effects in the charge-discharge curves can be explained by the slow attainment of equilibrium between Cr(H20)~ +3 and Cr(H20)~C1 §

Current flow through Pt/(Ba0.7Sr0.3)TiO3/Pt stack consists of both polarization current and electronic leakage current, which were separated by monitoring the discharging current when applied voltage was turned off. Electronic current comes from electrical field enhanced Schottky emission at the electrode–dielectric interface, and dominates the current flow at high electric field. At low electric field, polarization current prevails. The voltage and time dependence of the polarization current can be modeled by a distribution of Debye-type relaxations. The relaxation time and capacitance derived from current–time measurements were applied to simulate the current–voltage behavior, where good fitting to experimental result was obtained.