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We report the epitaxial growth of Ruddlesden–Popper nickelates, Lan+1NinO3n+1, with n up to 5 by reactive molecular beam epitaxy. X-ray diffractions indicate high crystalline quality of these films, and transport measurements show strong dependence on the n values. Angle-resolved photoemission spectroscopy reveals the electronic structure of La5Ni4O13, showing a large hole-like pocket centered around the Brillouin zone corner with a (π, π) back-folded copy.

Precisely controlled growth of oxide interfaces at the atomic layer level is critical for device applications but quite challenging. Here Sun et al. show real time monitoring and control of the surface composition of epitaxial strontium titanate perovskite films by analysing the Kikuchi lines.

Bronze phase titanium dioxide (TiO2-B) has an ideal open structure for applications in high-rate lithium-ion batteries, but high quality and water-free TiO2-B is difficult to synthesize since TiO2-B is energetically less stable compared to other TiO2 polymorphs. Using CaTi5O11 as a template layer can help stabilize TiO2-B phase, but it is still challenging to avoid the formation of TiO2 anatase (TiO2-A) impurity phase. Here we show the synthesis of phase pure TiO2-B films by in situ engineering of the surface quality of the buffer layer using molecular beam epitaxy (MBE). By applying surface sensitive in situ reflection high-energy electron diffraction (RHEED), the formation of the impurity TiO2 anatase phase on the surface of CaTi5O11 buffer layer can be monitored and eliminated in real time, leaving a clean template surface for the growth of phase pure TiO2-B films.

K0.63RhO2 single crystals were successfully grown by the flux method. Rietveld refinement of power X-ray diffraction patterns suggests that K0.63RhO2 belongs to the monoclinic P63mmc space group. Transport measurements on K0.63RhO2 revealed metallic behavior. The temperature-dependent resistance is well fitted by a different power law in two different temperature ranges. Antiferromagnetic ordering is observed in the ab-plane of K0.63RhO2 below 50 K. The most attractive feature of K0.63RhO2 is its significant Seebeck coefficient at room temperature (46 μV/cm), which is much greater than that of normal metals. Considered all together, the metallic conductivity, the significant Seebeck effect, and the non-hygroscopic properties of K0.63RhO2 make it a promising candidate material for thermoelectric applications.

The acceleration of ultrathin targets driven by intense laser pulses induces Rayleigh–Taylor-like instability. Apart from laser and target configurations, we find that electron heating and surface rippling, effects inherent to the interaction process, have an important role in instability evolution and growth. By employing a simple analytical model and two-dimensional particle-in-cell simulations, we show that the onset of electron heating in the early stage of the acceleration suppresses the growth of small-scale modes, but it has little influence on the growth of large-scale modes, which thus become dominant. With the growth of surface ripples, a mechanism that can significantly influence the growth of these large-scale modes is found. The laser field modulation caused by surface rippling generates an oscillatory ponderomotive force, directly modulating transverse electron density at a faster growth rate than that of ions and eventually enhancing instability growth. Our results show that when surface deformation becomes obvious, electron surface oscillation at 2ω0 (where ω0 is the laser frequency) is excited simultaneously, which can be seen as a signature of this mechanism.

A simple and efficient post-treatment method has been developed to tune the low-field magnetoresistance (LFMR) of Sr2FeMoO6 (SFMO) ceramics. SFMO ceramics, with initial 10% Fe/Mo anitsite defects (ASD), were prepared and soaked in a glycerin/water mixture (v/v, 1/19) for 0–24 h at room temperature; such post-treatment leads to SrMoO4 precipitating, which affects both the grain boundary (GB) strength and the ASD content. By controlling the soaking time the negative effect of ASD and the positive effect of GB on LFMR can be controlled, thus the LFMR can be tuned. When the soaking time is no longer than 6 h, the precipitated SrMoO4 influences the effects of ASD negligibly, but greatly improves the effects of GB, with LFMR enhancements of ~2 times obtained. However, longer soaking times result in an abrupt increase in ASD content; its negative effect is dominant and can offset the increasingly positive effect of GB, so LFMR is suppressed. Our work may provide a new method of using organic materials to manipulate the transport properties of double perovskite ceramics. [ABSTRACT FROM AUTHOR]