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Integration of oxides with silicon fuses advanced functional properties with a mature technological platform. In particular, direct EuO/Si contact holds high promise for spintronics but requires single‐crystalline epitaxial films with atomically sharp interfaces. The standard approach employing regular 2D superstructures of metal atoms on the Si surface fails to meet the challenge. Here, an alternative route is designed and shown to solve the problem. This route avoids regular templates; the chaotic 2D distribution of metal atoms on the Si surface prevents stabilization of unwanted crystal orientations. Thus, the disordered submonolayer phase at the interface promotes order in oxide/Si coupling, as witnessed by a combination of diffraction techniques and high‐resolution electron microscopy. The results not only mark tangible progress in manufacturing EuO/Si contacts but also provide a general framework for monolithic integration of functional oxides with semiconductor substrates. [ABSTRACT FROM AUTHOR]

Integration of crystalline oxides with silicon provides a versatile platform to extend and advance silicon technology. The interface between oxide and Si controls the structure and functional properties of the resulting material. In particular, the formation of a submonolayer metal phase on silicon is the standard approach to stabilize the epitaxial growth of oxides. However, fundamental questions--a) whether the interface transforms in the process of the synthesis; and b) if it is possible to control the interface and its electronic structure by varying the submonolayer template--remain unanswered. The present study employs MBE synthesis of EuO and SrO on Si(001) to demonstrate that the structure of the oxide/Si interface does not depend on the type of the template, its symmetry, and stoichiometry. Chemical transformations of the templates converging into the same 2D product are detected in situ by electron diffraction. Then, the common interfacial structure of 1D periodicity is visualized by high-resolution electron microscopy. The study provides insights into the process of oxide integration with silicon but also sets the limits in designing oxide/Si interfaces. [ABSTRACT FROM AUTHOR]

Graphene provides a wealth of advantageous functionalities but lags behind in spintronic applications due to lack of magnetism. A solution currently explored is proximity coupling of graphene with a 2D magnet. Recently, a class of submonolayer 2D magnets – superstructures of metal atoms on semiconductor surfaces – has been discovered. In these materials, magnetic metal atoms are not screened by anions; therefore, such 2D magnets can be employed in formation of magnetic heterostructures. Here, we report synthesis of a submonolayer 2D magnet – a superstructure of Gd on silicon – and its integration with graphene to induce spin-related phenomena. Magnetic properties of the 2D magnet and its heterostructure with graphene are rather similar with the exception that the heterostructure acquires significant magnetic coercivity. Proximity to the 2D magnet strongly affects the transport properties of graphene; in particular, the anomalous Hall effect emerges signifying spin-polarization of the carriers. Quantum oscillations are tracked across the magnetic transition; their evolution can be rationalized as an order of magnitude increase in the effective mass in the magnetic state. Being seamlessly integrated with the silicon technological platform, the heterostructure makes a prospective material for graphene spintronics. [Display omitted] [ABSTRACT FROM AUTHOR]

Epitaxial integration of oxides with the ubiquitous silicon technological platform promises devices with dreamed-of functionality but is difficult to achieve due to chemical processes at the Si/oxide interface. The standard approach suggests a protective template – a surface superstructure of SrSi 2 stoichiometry; still, only a handful of oxides couple to Si with atomically abrupt interface. We advocate an alternative approach – the use of metal-rich submonolayer templates as a general recipe, in particular, robust 1 × 5 reconstructions of Sr and Eu on Si. Their fail-safe synthesis is reported, diffraction techniques and electron microscopy reveal the structure and thermal stability of the reconstructions. The surface protection is discussed in terms of oxidation kinetics. The advantages of the new templates are demonstrated recruiting the example of the paradigmatic spintronic system EuO/Si. [ABSTRACT FROM AUTHOR]

Functional oxides demonstrate a wide range of magnetic, optical and transport properties. Their integration with silicon promises significant advances in electronics. An important key in enabling brand-new oxide technologies is the utilization of silicon/oxide epitaxy, thus making quality of the interface a critical issue. The progress depends on our ability to avoid formation of impurity phases at the interface and to tackle structural mismatch of the oxide and Si. We design a novel chemical protection of Si (001) surface on the submonolayer scale based on the surface metal silicide with the (1×5) reconstruction. This new technique is applied to the long-standing problem of integration of a ferromagnetic semiconductor with Si. Direct epitaxial growth of EuO on Si without any buffer layer, so far inaccessible, is achieved by molecular beam epitaxy. The nucleation step, comprising first 10 monolayers of EuO, is followed by a distillation-controlled growth. An alternative to standard capping procedures for EuO, based on controlled formation of an amorphous Eu2O3 layer, is devised. Crystal perfection of the films is established ex situ by x-ray diffraction and Rutherford backscattering. Magnetic properties of the EuO films match those of the bulk. [ABSTRACT FROM AUTHOR]