We report on efficient spin polarized injection and transport in long $\left({10}^2\text{nm}\right)$ channels of ${\text{Alq}}_3$ organic semiconductor. We employ vertical spin valve devices with a direct interface between the bottom manganite electrode and ${\text{Alq}}_3$, while the top-electrode geometry consists of an insulating tunnel barrier placed between the “soft” organic semiconductor and the top Co electrode. This solution reduces the ubiquitous problem of the so-called ill-defined layer caused by metal penetration, which extends into the organic layer up to distances of about 50–100 nm and prevents the realization of devices with well-defined geometry. For our devices the thickness is defined with an accuracy of about 2.5 nm, which is near the ${\text{Alq}}_3$ molecular size. We demonstrate efficient spin injection at both interfaces in devices with 100- and 200-nm-thick channels. We solve one of the most controversial problems of organic spintronics: the temperature limitations for spin transport in ${\text{Alq}}_3$-based devices. We clarify this issue by achieving room-temperature spin valve operation through the improvement of spin injection properties of both ferromagnetic/${\text{Alq}}_3$ interfaces. In addition, we discuss the nature of the inverse sign of the spin valve effect in such devices proposing a mechanism for spin transport.

We present a first-principles framework to extract deformation potentials in silicon based on density-functional theory (DFT) and density-functional perturbation theory (DFPT). We compute the electronic band structures, phonon dispersion relations, and electron-phonon matrix elements to extract deformation potentials for acoustic and optical phonons for all possible processes. The matrix elements clearly show the separation between intra- and intervalley scattering in the conduction band, and quantify the strength of the scattering events in the degenerate bands of the valence band. We then use an advanced numerical Boltzmann transport equation (BTE) simulator that couples DFT electronic structures and energy/momentum-dependent scattering rates to compute the transport properties for electrons and holes. By incorporating ionized impurity scattering as well, we calculate the $n$-type and $p$-type mobility versus carrier density and make comparisons to experiments, indicating excellent agreement. The fact that the method we present uses well-established theoretical tools and requires the extraction of only a limited number of matrix elements, makes it generally computationally very attractive, especially for semiconductors with a large unit cell and lower symmetry.

The electronic structures of the 8-hydroxyquinoline-aluminum $\left({\text{Alq}}_3\right)/{\text{Al}}_2{\text{O}}_3/\text{Co}$ interfaces were studied by photoelectron spectroscopy. A strong interface dipole was observed, which leads to a reduction in the electron injection barrier. The x-ray photoelectron spectroscopy spectra further indicate that the ${\text{Al}}_2{\text{O}}_3$ buffer layer prevents the chemical interaction between ${\text{Alq}}_3$ molecules and Co atoms. X-ray magnetic circular dichroism results demonstrate that a Co layer deposited on an ${\text{Al}}_2{\text{O}}_3$ buffered ${\text{Alq}}_3$ layer shows better magnetic ordering in the interface region than directly deposited Co, which suggests a better performance of spin valves with such a buffer layer. This is consistent with the recent results from [Dediu et al., Phys. Rev. B 78, 115203 (2008)].