Chaos at Interface Brings Order into Oxide/Silicon Structure

Abstract

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.

Interfacial bond engineering for direct integration of functional oxides with Si and Ge

“…High resolution transmission electron microscopy images in ref. 21 and 29 for oxide synthesis at such conditions signify the absence of interfacial amorphous layers in the heterostructures.…”

“…The milder conditions promote the quality of the interface but lead systematically to polycrystalline films. 21 The amount of alien orientations may be small but their mere presence may ruin the potential applications by causing leakage currents in a prospective device. The problem cannot be solved by varying the metal superstructure as the synthesis proceeds via a universal 1 × 3 phase.…”

“…The problem cannot be solved by varying the metal superstructure as the synthesis proceeds via a universal 1 × 3 phase. 29 Epitaxial oxide films can be synthesized on Si 21 or Ge 30 without any metal superstructures but the resulting interfaces exhibit a chaotic distribution of metal atoms. 21 Therefore, alternative synthetic routes to single-crystalline oxides integrated with semiconductor platforms are still in demand.…”

“…30 In particular, the main problem of low-temperature synthesis – formation of polycrystalline EuO films – has been revealed. 21,29,30 The interest in EuO arises from its record magnetotransport 42 and magneto-optical response, 43 high amenability of its properties to doping 42,44 and external strains. 45,46 EuO can be a useful component of oxide electronics as the recent observations of 2D superconductivity, 47 photoconductivity 48 and spin-dependent properties 49 in EuO/KTaO 3 suggest.…”

Femtosecond optical orientation triggering magnetization precession in epitaxial EuO films

“…21 Significant progress has been reached in synthesis of EuO in the form of epitaxial films on different substrates 17,[22][23][24][25] including such technologically important platform as Si. 26,27 The interest is not only in EuO itself but also in its effect on properties of other materialsimprinting magnetism in graphene 28 and other 2D materials, 29 making spin contacts to Si, 30 producing 2D superconductivity, 31 photoconductivity 32 and spin-dependent transport properties 33 in oxide structures. All this explains the continuing appeal of magneto-optical studies of EuO.…”