A novel cocasting approach is presented for improving electroactivity of solution-cast films of conducting polymers. Solutions of the n-doping polymer poly(benzimidazobenzophenanthroline) (BBL) were co-deposited with the ionic liquid electrolyte 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EMIBTI). The resultant co-continuous mixture yielded highly porous polymer films (CC-BBL) upon removal of solvent and EMIBTI. Electrochemical quartz crystal microgravimetry revealed that the n-doping process in neat ionic liquid is anion-dominant, which is contrary to what is observed in dilute electrolyte solutions. The CC-BBL films exhibit a thirty-fold increase in initial current response and capacity relative to non-cocast BBL films. While current response and capacity of the non-cocast BBL improve with cycling, they level out after 800 cycles at 35% of those of the CC-BBL. CC-BBL shows high n-doping stability; no decrease in electroactivity is seen after 1000 cycles.

The integration of oxides with semiconductors is important for the technological advancement of the next generation electronics. Concomitant ferroelectric and antiferromagnetic (AF) behavior is demonstrated in single crystal BiFeO3 (BFO) films grown on 20 nm SrTiO3 (STO) virtual substrates on Si(100) using molecular beam epitaxy (MBE). STO thin films are grown in an oxide MBE chamber by co-deposition of Sr, Ti, and molecular O2. Careful control of the O2 during nucleation produced commensurate growth of STO on Si. The sequence of the steps allows for the suppression of an amorphous SiO2 layer. This STO(20 nm)/Si structure was used as a virtual substrate for MBE deposition of BFO on Si without breaking vacuum. BFO was deposited using Fe and O2 plasma with an overpressure of Bi flux, the growth rate was controlled by the incoming Fe flux. The reflection high energy electron diffraction image shows a 2-D growth front with a 6-fold surface reconstruction under optimized O2 pressure of 5 × 10−8 mbar. Cross-sectional transmission electron microscopy (TEM) confirms the high crystallinity of the films and shows sharp, atomically flat interfaces. The selected area diffraction pattern (SADP) reveals that BFO grows in a distorted rhombohedral crystal structure. X-ray diffraction does not show formation of second phases and is consistent with the TEM and SADP results. The BFO films show AF behavior with a Neel temperature that exceeds 350 K, as expected (TN = 673 K) and with a residual ferromagnetic behavior that decreases with film thickness and is consistent with the G-type AF due to the canted spins. The saturation magnetization per unit volume for a 40 nm thick film was 180 emu/cm3 at an in-plane magnetic field of 8 kOe. The ferroelectric behavior of the films was verified using piezoresponse force microscopy.

We investigate the effect of strain and oxygen vacancies (VO) on the crystal and optical properties of oxygen deficient, ultra-thin (4–30 nm) films of SrTiO3-δ (STO) grown heteroepitaxially on p-Si(001) substrates by molecular beam epitaxy. We demonstrate that STO band gap tuning can be achieved through strain engineering and show that the energy shift of the direct energy gap transition of SrTiO3-δ/Si films has a quantifiable dimensional and doping dependence that correlates well with the changes in crystal structure.

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Annular dark field (ADF) images of complete InAs quantum dots (QDs) in an InP matrix have been simulated in order to study the effects of strain and composition on image contrast. The QDs had a base radius of 2.5 nm, a height of 3.0 nm and were situated on a 0.5 nm InAs wetting layer. The elastic displacement fields, arising from the 3.1% lattice mismatch between InAs and InP, were simulated using finite-element methods and the appropriate anisotropic elastic constants were used for each material [1]. Figures 1A and 1B are the horizontal (x) and vertical (z) displacements of the QD and surrounding material for a plane through the centre of the QD. The magnitude of the displacements is greatest at the edge of the dot and a maximum value of 0.05 nm is observed.