In this letter, we report on electrical spin injection and detection in n-type germanium-on-insulator using a Co/Py/Al2O3 spin injector and 3-terminal non-local measurements. We observe an enhanced spin accumulation signal of the order of 1 meV consistent with the sequential tunneling process via interface states in the vicinity of the Al2O3/Ge interface. This spin signal is further observable up to 220 K. Moreover, the presence of a strong inverted Hanle effect points out the influence of random fields arising from interface roughness on the injected spins.

Electrical spin injection into semiconductors paves the way for exploring new phenomena in the area of spin physics and new generations of spintronic devices. However the exact role of interface states in spin injection mechanism from a magnetic tunnel junction into a semiconductor is still under debate. In this letter, we demonstrate a clear transition from spin accumulation into interface states to spin injection in the conduction band of n-Ge. We observe spin signal amplification at low temperature due to spin accumulation into interface states followed by a clear transition towards spin injection in the conduction band from 200 K up to room temperature. In this regime, the spin signal is reduced down to a value compatible with spin diffusion model. More interestingly, we demonstrate in this regime a significant modulation of the spin signal by spin pumping generated by ferromagnetic resonance and also by applying a back-gate voltage which are clear manifestations of spin current and accumulation in the germanium conduction band.

In this letter, we first show electrical spin injection in the germanium conduction band at room temperature and modulate the spin signal by applying a gate voltage to the channel. The corresponding signal modulation agrees well with the predictions of spin diffusion models. Then by setting a temperature gradient between germanium and the ferromagnet, we create a thermal spin accumulation in germanium without any tunnel charge current. We show that temperature gradients yield larger spin accumulations than pure electrical spin injection but, due to competing microscopic effects, the thermal spin accumulation in germanium remains surprisingly almost unchanged under the application of a gate voltage to the channel.Comment: 7 pages, 3 figure

Functional oxides of the perovskite family present a variety of physical properties (ferroelectricity, ferromagnetism, superconductivity, high Pockels coefficients, …) that make them very attractive for applications in the micro-optoelectronic field. 1 These materials are classically used as thin layers grown on oxide substrates, mainly SrTiO 3 (STO). Important perspectives for the integration of new functionalities on silicon and other semiconductor platforms, and therefore for the fabrication of innovative devices combining the physical properties of functional oxides and semiconductors, are offered by the advances in epitaxy of ABO 3 perovskites on semiconductors using molecular beam epitaxy (MBE). From the material science point of view, STO/Si can be considered as a prototypical system to understand the impact of structural and chemical heterogeneity on crystal growth. Controlling the chemical reactions between the growing layer and the substrate is one of the main challenges related to the epitaxial growth of perovskite oxides on semiconductor and particularly STO on Si, as the interface between these materials has been predicted as thermodynamically instable. 2 This is to a certain extent made possible by using a Sr-based treatment of the Si surface, as evidenced since the very first studies of this system 3,4 , and popularized by McKee et al. 5 Such procedure or its

Integration of epitaxial complex ferroelectric oxides such as BaTiO 3 on semiconductor substrates depends on the ability to finely control their structure and properties, which are strongly correlated. The epitaxial growth of thin BaTiO 3 films with high interfacial quality still remains scarcely investigated on semiconductors; a systematic investigation of processing conditions is missing although they determine the cationic composition, the oxygen content, and the microstructure, which, in turn, play a major role on the ferroelectric properties. We report here the study of various relevant deposition parameters in molecular beam epitaxy for the growth of epitaxial tetragonal BaTiO 3 thin films on silicon substrates. The films were grown using a 4 nm-thick epitaxial SrTiO 3 buffer layer. We show that the tetragonality of the BaTiO 3 films, the crystalline domain orientations, and SiO 2 interfacial layer regrowth strongly depend on the oxygen partial pressure and temperature during the growth and on the post-deposition anneal. The ferroelectricity of the films, probed using piezoresponse force microscopy, is obtained in controlled temperature and oxygen pressure conditions with a polarization perpendicular to the surface. V

The effect of the top electrode interface on the hysteretic behavior of epitaxial ferroelectric Pb(Zr,Ti)O3 thin films with bottom SrRuO3 electrode J. Appl. Phys. 112, 064116 (2012); 10.1063/1.4754318 Microstructure and ferroelectric properties of low-fatigue epitaxial, all (001)-oriented ( Bi , La ) 4 Ti 3 O 12 ∕ Pb ( Zr 0.4 Ti 0.6 ) O 3 ∕ ( Bi , La ) 4 Ti 3 O 12 trilayered thin films on (001) Sr Ti O 3 substrates J. Appl. Phys. 98, 014101 (2005); 10.1063/1.1946913 Growth, structure, and properties of all-epitaxial ferroelectric ( Bi , La ) 4 Ti 3 O 12 ∕ Pb ( Zr 0.4 Ti 0.6 ) O 3 ∕ ( Bi , La ) 4 Ti 3 O 12 trilayered thin films on Sr Ru O 3 -covered Sr Ti O 3 ( 011 ) substrates Appl. Phys. Lett. 86, 082906 (2005); 10.1063/1.1864248 Domain structure of epitaxial PbTiO 3 thin films on Pt(001)/MgO(001) substrates

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