Variable-temperature scanning tunneling spectroscopy revealed a sharp Verwey transition in individual ∼10 nm magnetite nanocrystals prepared by the coprecipitation technique and embedded in the surface of a gold film. The transition was observed as a significant change in the electronic structure around the Fermi level, with an apparent band gap of ∼140-250 meV appearing below the transition temperature and a pseudogap of ∼75 ± 10 meV appearing above it. The transition temperature was invariably observed around 101 ± 2 K for different nanocrystals, as opposed to 123 K typically reported for stoichiometric bulk crystals. This suggests that the lowering of the transition temperature is an intrinsic finite size effect, probably due to the presence of the surface.

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Epitaxial growth of atomically-sharp interfaces serves as one of the main building blocks of nanofabrication. Such interfaces are crucial for the operation of various devices including transistors, photo-voltaic cells, and memory components. In order to avoid charge traps that may hamper the operation of such devices, it is critical for the layers to be atomically-sharp. Fabrication of atomically sharp interfaces normally requires ultra-high vacuum techniques and high substrate temperatures. We present here a new self-limiting wet chemical process for deposition of epitaxial layers from alkoxide precursors. This method is fast, cheap, and yields perfect interfaces as we validate by various analysis techniques. It allows the design of heterostructures with half-unit cell resolution. We demonstrate our method by designing hole-type oxide interfaces SrTiO3/BaO/LaAlO3. We show that transport through this interface exhibits properties of mixed electron-hole contributions with hole mobility exceeding that of electrons. Our method and results are an important step forward towards a controllable design of a p-type oxide interface.Growth methods of epitaxial thin films can be roughly categorized as physical and chemical. While physical methods (i.e. molecular beam epitaxy, pulsed laser deposition (PLD) [1]) are based on creating a beam of the film material and transporting it in vacuum onto the substrate. Chemical methods such as: chemical vapor deposition and atomic layer deposition (ALD) use a chemical precursor, a compound containing the film growth material. The precursor is transferred in vacuum onto the substrate, where the surface catalyzes the precursor dissociation reaction, and the deposition of the film. While giving very good results for film growth, these methods lack the versatility and become increasingly complex [2] when a wide variety of surface monolayers is required. In Solution monolayer epitaxy (SoME) the substrate of choice, in this case a (100) TiO 2 terminated SrTiO 3 , is submersed in a solution of a dissolved precursor of choice, at a temperature slightly lower than its decomposition temperature. Under these conditions the precursor molecules do not decompose in the solution unless they are in close proximity to the surface of the substrate, which catalyzes the decomposition of the precursor and the required material resulting in a monolayer.In our case SoME is used to grow a BaO monolayer (termination) on a SrTiO 3 substrate as described in Figure 1. We then grow an additional epitaxial layer of LaAlO 3 using traditional pulsed laser deposition, givarXiv:1710.04216v1 [cond-mat.str-el]