Insecticide-impregnated ear tags for range cattle

When both cows and calves were double-tagged (one tag per ear) with ear tags impregnated with fenvalerate (Ectrin) or permethrin (Atroban), the calves gained faster (P\u3c.01) than when neither cows nor calves were tagged. Double-tagged yearling heifers gained faster (P\u3c.05) than did heifers without tags. When all cows had been double-tagged, tagging the calves did not increase calf weight gain

Post deposition annealing of epitaxial Ce1-xPrxO2-δ films grown on Si(111)

In this work the structural and morphological changes of Ce1−xPrxO2−δ (x = 0.20, 0.35 and 0.75) films grown on Si(111) due to post deposition annealing are investigated by low energy electron diffraction combined with a spot profile analysis. The surface of the oxide films exhibit mosaics with large terraces separated by monoatomic steps. It is shown that the Ce/Pr ratio and post deposition annealing temperature can be used to tune the mosaic spread, terrace size and step height of the grains. The morphological changes are accompanied by a phase transition from a fluorite type lattice to a bixbyite structure. Furthermore, at high PDA temperatures a silicate formation via a polycrystalline intermediate state is observed

Control of electron-state coupling in asymmetric Ge/Si−Ge quantum wells

Theoretical predictions indicate that the n-type Ge / Si − Ge multi-quantum-well system is the most promising material for the realization of a Si -compatible THz quantum cascade laser operating at room temperature. To advance in this direction, we study, both experimentally and theoretically, asymmetric coupled multi-quantum-well samples based on this material system, that can be considered as the basic building block of a cascade architecture. Extensive structural characterization shows the high material quality of strain-symmetrized structures grown by chemical vapor deposition, down to the ultrathin barrier limit. Moreover, THz absorption spectroscopy measurements supported by theoretical modeling unambiguously demonstrate inter-well coupling and wavefunction tunneling. The agreement between experimental data and simulations allows us to characterize the tunneling barrier parameters and, in turn, achieve highly controlled engineering of the electronic structure in forthcoming unipolar cascade systems based on n-type Ge / Si − Ge multi-quantum-wells

Control of Electron-State Coupling in Asymmetric Ge/Si-Ge Quantum Wells

Theoretical predictions indicate that the n-type Ge/Si-Ge multi-quantum-well system is the most promising material for the realization of a Si-compatible THz quantum cascade laser operating at room temperature. To advance in this direction, we study, both experimentally and theoretically, asymmetric coupled multi-quantum-well samples based on this material system, that can be considered as the basic building block of a cascade architecture. Extensive structural characterization shows the high material quality of strain-symmetrized structures grown by chemical vapor deposition, down to the ultrathin barrier limit. Moreover, THz absorption spectroscopy measurements supported by theoretical modeling unambiguously demonstrate inter-well coupling and wavefunction tunneling. The agreement between experimental data and simulations allows us to characterize the tunneling barrier parameters and, in turn, achieve highly controlled engineering of the electronic structure in forthcoming unipolar cascade systems based on n-type Ge/Si-Ge multi-quantum-wells

High-Quality n-Type Ge/SiGe Multilayers for THz Quantum Cascade Lasers

The exploitation of intersubband transitions in Ge/SiGe quantum cascade devices could pave the way towards the integration of THz light emitters into the silicon-based technology. Aiming at the realization of a Ge/SiGe Quantum Cascade Laser (QCL), we investigate optical and structural properties of n-type Ge/SiGe coupled quantum well systems. The samples have been investigated by means of X-ray diffraction, scanning transmission electron microscopy, atom probe tomography and Fourier Transform Infrared absorption spectroscopy to assess the growth capability with respect to QCL design requirements, carefully identified by means of modelling based on the non-equilibrium Green function formalism

Lattice deformation at the sub-micron scale: X-ray nanobeam measurements of elastic strain in electron shuttling devices

The lattice strain induced by metallic electrodes can impair the functionality of advanced quantum devices operating with electron or hole spins. Here we investigate the deformation induced by CMOS-manufactured titanium nitride electrodes on the lattice of a buried, 10 nm-thick Si/SiGe Quantum Well by means of nanobeam Scanning X-ray Diffraction Microscopy. We were able to measure TiN electrode-induced local modulations of the strain tensor components in the range of $2 - 8 \times 10^{-4}$ with ~60 nm lateral resolution. We have evaluated that these strain fluctuations are reflected into local modulations of the potential of the conduction band minimum larger than 2 meV, which is close to the orbital energy of an electrostatic quantum dot. We observe that the sign of the strain modulations at a given depth of the quantum well layer depends on the lateral dimensions of the electrodes. Since our work explores the impact of device geometry on the strain-induced energy landscape, it enables further optimization of the design of scaled CMOS-processed quantum devices.Comment: 16 pages, 6 figure

Electron-doped SiGe Quantum Well Terahertz Emitters pumped by FEL pulses

We explore saturable absorption and terahertz photoluminescence emission in a set of n-doped Ge/SiGe asymmetric coupled quantum wells, designed as three-level systems (i.e., quantum fountain emitter). We generate a non-equilibrium population by optical pumping at the 1→3 transition energy using picosecond pulses from a free-electron laser and characterize this effect by measuring absorption as a function of the pump intensity. In the emission experiment we observe weak emission peaks in the 14–25 meV range (3–6 THz) corresponding to the two intermediate intersubband transition energies. The results represent a step towards silicon-based integrated terahertz emitters