UV-visible absorption and cathodoluminescence spectra of phase-pure epitaxial BiFeO3 thin films grown on SrTiO3(001) substrates by ultrahigh vacuum sputtering reveal a bandgap of 2.69–2.73eV for highly strained ∼70nm thick BiFeO3 films. This bandgap value agrees with theoretical calculations and recent experimental results of epitaxial BiFeO3 films, demonstrating only minimal bandgap change with lattice distortion. Both absorption and cathodoluminescence spectra show defect transitions at 2.20 and 2.45eV, of which the latter can be attributed to defect states due to oxygen vacancies.

Experimental DetailsGeneral considerations. Tin(II) sulfide (Aldrich, 99.99+%) and europium(III) nitrate hexahydrate (Strem, 99.9+%) were purchased and used without further purification. Both 1,2-ethylenediamine (Fluka, 99.5+%) and 1,2-ethanedithiol (98+%, Alfa Aesar) were distilled prior to use. 1,2-Ethylenediamine (en) was first dried for 3 d with either CaO (~120 g per 500 mL) or CaH 2 (~15-20 g per 1 L); after decanting, en was refluxed over Na until a dark blue color was observed (ca. 6.5 h) and was then distilled under N 2 (g). 1,2-Ethanedithiol (edt) was dried over 3 Å molecular sieves and then distilled. The dissolution was performed using standard Schlenk techniques under N 2 (g) in the absence of H 2 O and O 2 (g). CAUTION: 1,2-ethanedithiol has a pungent odor and should be handled in a fume hood as with any volatile, flammable organic solvent using appropriate personal protection equipment. The thiol may be quenched in a fume hood by slow addition to a large excess of stirred commercial hypochlorite laundry bleach solution (5.25% sodium hypochlorite); a pH > 6 should be maintained by addition of NaOH, if necessary. After stirring for 24 h, the solution can be treated as aqueous waste.Dissolution of bulk SnS. A typical dissolution experiment entailed addition under flowing N 2 (g) of ca. 650 mg of thoroughly ground SnS powder into a three-neck round-bottom flask that had been fitted with a reflux condenser and a stir bar. Distilled en (10 mL) and edt (0.9 mL) were then added. The mixture was lightly heated with a heat gun and was sonicated for a ca. 10 min. A heating mantle was then used to further heat the mixture to 50 ˚C for 15 h with stirring.SnS Recovery and Organic Content Determination. Thermogravimetric analysis (TGA) was performed in a TA Instruments Q50 TGA. An alumina pan was used to dry 50 µL of the solution mixture in situ. The program entailed heating to 125 ˚C and holding this temperature for 15 min, followed by cooling to 30 ˚C and equilibration. The final analysis step entailed heating the sample to 425 ˚C at 10 ˚C min -1 . FT-IR spectroscopy was performed with aBruker Vertex 80v and a ZnSe substrate was used to drop cast the SnS mixture followed by an anneal on a hot plate under flowing N 2 (g).

This work studies the control of the magnetic and magnetotransport properties of La 0.67 Sr 0.33 MnO 3 thin films through strain engineering. The strain state is characterized by the tetragonal distortion (c/a ratio), which can be varied continuously between a compressive strain of 1.005 to a tensile strain of 0.952 by changing the type of substrate, the growth rate, and the presence of an underlying La 0.67 Sr 0.33 FeO 3 buffer layer. Increasing tensile tetragonal distortion of the La 0.67 Sr 0.33 MnO 3 thin film decreases the saturation magnetization, changes the temperature dependence of the resistivity and magnetoresistance, and increases the resistivity by several orders of magnitude.The perovskite oxides have been widely investigated in recent years since they possess various important physical properties such as ferromagnetism, superconductivity, and ferroelectricity. 1 In particular, La 0.67 Sr 0.33 MnO 3 (LSMO) is an attractive candidate for spintronic devices 2,3 because it displays colossal magnetoresistance (CMR) and half-metallicity, and possesses a Curie temperature, T C, above room temperature (~ 360 K). 4,5 In this material, the T C marks the transition between the ferromagnetic (FM)/ metallic and the paramagnetic (PM)/ insulating states, as well as the peak in the CMR. This correlation between the electrical and magnetic properties is explained by the double-exchange mechanism 6,7 which involves the hopping of electrons between Mn 3+ and Mn 4+ ions with parallel spin through a bridging O 2-ion. Due to the strong interactions between the charge and orbital degrees of freedom, these properties can be manipulated by a number of different parameters, including external pressure 8 , oxygen stoichiometry 9 , and the doping level. 10,11 With thin films, the epitaxial strain imposed from the underlying substrate provides an additional tuning parameter for the functional properties. It has been shown that coherently strained LSMO thin films can be grown on a wide range of different single crystal oxide substrates and that the resulting strain dramatically impacts the magnetic and magnetotransport properties of the thin films. [12][13][14][15][16] The strain state can be characterized by the tetragonal distortion, defined as the c/a ratio, where the in-plane lattice parameter of the film, a, is dictated by the lattice parameter of the substrate, and the out-of-plane lattice parameter, c, is allowed to respond accordingly. For example, Kwon et al. reported that an in-plane easy magnetization direction is observed in tensile-strained films (c/a ratio < 1) grown on (001)-oriented SrTiO 3 (STO) substrates, while compressively strained films (c/a ratio > 1) grown on (001)-oriented LaAlO 3 (LAO) substrates exhibit an out-of-plane easy axis. 12 Furthermore, it has been shown that the magnitude of this tetragonal distortion depends on the crystallographic orientation of the film and the substrate. 13,14,17 Fully strained LSMO films grown on (110)-oriented substrates show enhanced electrical and magnetic propertie...

We study the vibrational motion of membrane resonators upon strong drive in the strongly nonlinear regime. By imaging the vibrational state of rectangular siliconnitride membrane resonators and by analyzing the frequency response using optical interferometry, we show that upon increasing the driving strength, the membrane adopts a peculiar deflection pattern formed by concentric rings superimposed onto the drum head shape of the fundamental mode. Such a circular symmetry cannot be described as a superposition of a small number of excited linear eigenmodes. Furthermore, the different parts of the membrane oscillate at different multiples of the drive frequency, an observation that we denominate as 'localization of overtones'. We introduce a phenomenological model that is based on the coupling of a very small number of effective nonlinear oscillators, representing the different parts of the membrane, and that describes the experimental observations. arXiv:1902.01270v1 [cond-mat.mes-hall]

We report measurements of the temperature coefficient of the resistance (TCR) and the low-frequency noise of epitaxial La0.7Sr0.3MnO3 (LSMO) thin films deposited on SrTiO3 (STO) and (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates. An x-ray-diffraction study showed that the films were (001) oriented. A normalized Hooge parameter of 9×10−31m3 was measured at 300K in the case of a 10-μm-wide, 575-μm-long line patterned in the 200-nm-thick film grown on STO substrate. This value is among the lowest reported values for manganites and close to values measured in standard metals and semiconductors. The corresponding noise equivalent temperature (NET) was constant in the 300–340K range and equal to 6×10−7KHz−1∕2 at 10Hz and 150μA for a 10-μm-wide, 575-μm-long line patterned in a 200-nm-thick LSMO film. This very low NET value is comparable to the best published results for manganites and was even found to be lower than the NET of other uncooled thermometers such as amorphous semiconductors, vanadium oxides, or semiconducting YBa2Cu3O6+σ. This can easily be explained by the lower noise level of epitaxial manganites thin films compared to others. The results show that despite a TCR of only 0.017K−1 at 300K, and thanks to a very low-noise level, LSMO thin films are real potential material for uncooled thermometry and bolometry.