The power density and charge-discharge time of electrical double layer capacitors are largely determined by how fast the electrolyte ions can travel within the carbon electrode particles. Our systematic studies using zeolite-templated carbons show that an enhancement in ion transport rate by more than 2 orders of magnitude is possible by minimizing the micropore tortuosity. Very uniform carbon deposition was achieved using a well-controlled process involving the decomposition of acetylene precursor at a reduced pressure of 10 Torr and under a constant flow rate of 100 sccm. Selected carbon samples with well-aligned, straight micropores demonstrate high specific capacitance of up to 300 F/g and outstanding frequency response of up to 10 Hz for 250 microm thick electrodes, indicating an attractive combination of high specific energy and high specific power in electrical double layer capacitors. Such properties are critical for many peak-power hungry applications, such as the leveling of subsecond disturbances in power lines. Our findings provide guidance for the optimal design of porous carbons with greatly improved power storage characteristics.

The temperature dependent Hall mobility data from La-doped SrTiO 3 thin films has been analyzed and modeled considering various electron scattering mechanisms. We find that a ~6 meV transverse optical phonon (TO) deformation potential scattering mechanism is necessary to explain the dependence of transport on temperature between 10-200 K. Also, we find that the low temperature electron mobility in intrinsic (nominally undoped) SrTiO 3 is limited by acoustic phonon scattering. Adding the above two scattering mechanisms to longitudinal optical phonon (LO) and ionized impurity scattering mechanisms, excellent quantitative agreement between mobility measurement and model is achieved in the whole temperature range (2-300K) and carrier concentrations ranging over a few orders of magnitude (8x10 17 cm -3 -2x10 20 cm -3 ).Understanding the carrier scattering mechanisms in any material paves the way for improvement in its transport properties, unraveling of new physics, and eventual applications.A good case in point is the semiconductor GaAs: improvements in the mobility of this material led to the discovery of the fractional quantum Hall-effect, and in ultrafast high electron mobility transistors (HEMTs) that enables high-speed microwave communications [1,2].Strontium titanate, SrTiO 3 , is a perovskite transition metal oxide. It has been studied extensively for the many interesting phenomena it exhibits, such as quantum paraelectricity, structural phase transition, superconductivity etc. [3][4][5]. The discovery of a two dimensional electron gas at the heterointerface of SrTiO 3 and other oxides has opened up a whole new area of heterostructure oxide electronics [6][7][8]. A major obstacle in developing devices using SrTiO 3 is the low electron mobility in this material, and a lack of complete understanding of the major active electron scattering mechanisms.

The thermoelectric properties at temperatures between 10 K and 300 K of La-doped SrTiO3 thin films grown by hybrid molecular beam epitaxy (MBE) on undoped SrTiO3 substrates are reported. Below 50 K, the Seebeck coefficients exhibit very large magnitudes due to the influence of phonon drag. Combined with high carrier mobilities, exceeding 50 000 cm2 V−1 s−1 at 2 K for the films with the lowest carrier densities, this leads to thermoelectric power factors as high as 470 μWcm−1 K−2. The results are compared with other promising low temperature thermoelectric materials and discussed in the context of coupling with phonons in the undoped substrate.

We analyze and compare the temperature dependence of the electron mobility of two- and three-dimensional electron liquids in SrTiO3. The contributions of electron-electron scattering must be taken into account to accurately describe the mobility in both cases. For uniformly doped, three-dimensional electron liquids, the room temperature mobility crosses over from longitudinal optical (LO) phonon-scattering-limited to electron-electron-scattering-limited as a function of carrier density. In high-density, two-dimensional electron liquids, LO phonon scattering is completely screened and the mobility is dominated by electron-electron scattering up to room temperature. The possible origins of the observed behavior and the consequences for approaches to improve the mobility are discussed.