Growth of PdCoO2 films with controlled termination by molecular-beam epitaxy and determination of their electronic structure by angle-resolved photoemission spectroscopy

Utilizing the powerful combination of molecular-beam epitaxy (MBE) and angle-resolved photoemission spectroscopy (ARPES), we produce and study the effect of different terminating layers on the electronic structure of the metallic delafossite PdCoO2. Attempts to introduce unpaired electrons and synthesize new antiferromagnetic metals akin to the isostructural compound PdCrO2 have been made by replacing cobalt with iron in PdCoO2 films grown by MBE. Using ARPES, we observe similar bulk bands in these PdCoO2 films with Pd-, CoO2-, and FeO2-termination. Nevertheless, Pd- and CoO2-terminated films show a reduced intensity of surface states. Additionally, we are able to epitaxially stabilize PdFexCo1-xO2 films that show an anomaly in the derivative of the electrical resistance with respect to temperature at 20 K, but do not display pronounced magnetic order

Enhanced TC in SrRuO3/DyScO3(110) thin films with high residual resistivity ratio

Epitaxial untwinned SrRuO3 thin films were grown on (110)-oriented DyScO3 substrates by molecular-beam epitaxy. We report an exceptional sample with a residual resistivity ratio (RRR), ρ [300 K]/ρ [4 K] of 205 and a ferromagnetic Curie temperature, TC, of 168.3 K. We compare the properties of this sample to other SrRuO3 films grown on DyScO3(110) with RRRs ranging from 8.8 to 205, and also compare it to the best reported bulk single crystal of SrRuO3. We determine that SrRuO3 thin films grown on DyScO3(110) have an enhanced TC as long as the RRR of the thin film is above a minimum electrical quality threshold. This RRR threshold is about 20 for SrRuO3. Films with lower RRR exhibit TCs that are significantly depressed from the intrinsic strain-enhanced value

Synthesis of Submicrometer Hollow Particles with a Nanoscale Double-Layer Shell Structure

The morphology of hollow, double-shelled submicrometer particles is generated through a rapid aerosol-based process. The inner shell is an essentially hydrophobic carbon layer of nanoscale dimension (20 nm), and the outer shell is a hydrophilic silica layer of approximately 40 nm, with the shell thickness being a function of the particle size. The particles are synthesized by exploiting concepts of salt bridging to lock in a surfactant (CTAB) and carbon precursors together with iron species in the interior of a droplet. This deliberate negation of surfactant templating allows a silica shell to form extremely rapidly, sealing in the organic species in the particle interior. Subsequent pyrolysis results in a buildup of internal pressure, forcing carbonaceous species against the silica wall to form an inner shell of carbon. The incorporation of magnetic iron oxide into the shells opens up applications in external stimuli-responsive nanomaterials

Demystifying the growth of superconducting Sr2RuO4 thin films

We report the growth of superconducting Sr2RuO4 thin films by molecular-beam epitaxy on (110) NdGaO3 substrates with transition temperatures of up to 1.8 K. We calculate and experimentally validate a thermodynamic growth window for the adsorption-controlled growth of superconducting Sr2RuO4 epitaxial thin films. The growth window for achieving superconducting Sr2RuO4 thin films is narrow in growth temperature, oxidant pressure, and ruthenium-to-strontium flux ratio

Adsorption-controlled growth and properties of epitaxial SnO films

When it comes to providing the unusual combination of optical transparency, p-type conductivity, and relatively high mobility, Sn2+-based oxides are promising candidates. Epitaxial films of the simplest Sn2+ oxide, SnO, are grown in an adsorption-controlled regime at 380 degrees C on Al2O3 substrates by molecular-beam epitaxy, where the excess volatile SnOx desorbs from the film surface. A commensurately strained monolayer and an accompanying van der Waals gap is observed near the substrate interface, promoting layers with high structural perfection notwithstanding a large epitaxial lattice mismatch (-12%). The unintentionally doped films exhibit p-type conductivity with carrier concentration 2.5 x 10(16) cm(-3) and mobility 2.4 cm(2) V(-1)s(-1) at room temperature. Additional physical properties are measured and linked to the Sn2+ valence state and corresponding lone-pair charge-density distribution.Funding Agencies|ASCENT - DARPA; National Science Foundation (NSF)National Science Foundation (NSF) [DGE-1650441]; NSF MRSEC ProgramNational Science Foundation (NSF)NSF - Directorate for Mathematical &amp; Physical Sciences (MPS) [DMR-1719875]; NSFNational Science Foundation (NSF) [ECCS-1542081, DMR-0703406]; Air Force Office of Scientific ResearchUnited States Department of DefenseAir Force Office of Scientific Research (AFOSR) [FA955018-1-0024]; U.S. Department of Energy (DOE) Office of Science User FacilityUnited States Department of Energy (DOE) [DEAC02-06CH11357]; Olle Engkvist Foundation; NSF [Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM)] [DMR-1539918]</p