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In this work, we describe the design and first experimental results of a new setup that combines evaporation of liquids in ultrahigh vacuum conditions with in situ high sensitivity thermal characterization of thin films. Organic compounds are deposited from the vapor directly onto a liquid nitrogen cooled substrate, permitting the preparation and characterization of glassy films. The substrate consists of a microfabricated, membrane-based nanocalorimeter that permits in situ measurements of heat capacity under ultrafast heating rates (up to 105 K/s) in the temperature range of 100–300 K. Three glass forming liquids—toluene, methanol, and acetic acid—are characterized. The spikes in heat capacity related to the glass-transition temperature, the fictive temperature and, in some cases, the onset temperature of crystallization are determined for several heating rates. [ABSTRACT FROM AUTHOR]

The kinetics of intermediate phase formation between ultrathin films of Pd (12 nm) and single-crystalline Si (100) is monitored by in-situ nanocalorimetry at ultrafast heating rates. The heat capacity curves show an exothermic peak related to the formation of Pd2Si. A kinetic model which goes beyond the conventional linear-parabolic growth to consider independent nucleation and lateral growth of Pd2Si along the interface and vertical growth mechanisms is developed to fit the calorimetric curves. The model is used to extract the effective interfacial nucleation/growth and diffusion coefficients at the unusually high temperatures of silicide formation achieved at very fast heating rates. [ABSTRACT FROM AUTHOR]

Abstract: We report on nanocalorimetric measurements of 50nm thick toluene films at heating rates spanning 600 to 8×104 K/s. The films are grown from the vapour at 90K directly onto the nanocalorimetric cell. The kinetic and thermodynamic stability of as-deposited films is higher than the stability of films cooled from the supercooled liquid at 2000K/s. We also show that at those heating rates, the calorimetric T g does not correlate with the relaxation time obtained by dielectric spectroscopy. [Copyright &y& Elsevier]

Abstract: Titanium thin films have been designed to achieve efficient photocatalytic activity in the visible range. Doping induced by oxygen deficiency is the key for the increased photodegradation properties of the film, as both experimental and theoretical studies demonstrate. Its effectiveness on a nonylphenol solution has been demonstrated. [Copyright &y& Elsevier]

Abstract: Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2eV) it is not viable to use sunlight as an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380nm is required. This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO2 thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters. [Copyright &y& Elsevier]

The compressive strain induced in epitaxial Sr4Fe6O13±δ (SFO) films of different thicknesses grown on SrTiO3 substrates is partially released by the modulation of the incommensurate oxygen superstructure along the a-axis parallel to the substrate [q=αam*, superspace group Xmmm(α00)0s0]. The modulation α value varies proportionally to the in-plane a-parameter in a continuous range from 0.41, for fully strained thin films of about 20–30 nm, to 0.44 for partially-relaxed thicker films of about 280 nm. This mechanism is responsible for the observed slow relaxation of the cell structure upon the film thickness increase in comparison with an equilibrium misfit dislocation-mediated relaxation. [ABSTRACT FROM AUTHOR]

Abstract: We report the high temperature electronic transport properties of SrFeO3− δ epitaxial thin films obtained by pulsed laser deposition on NdGaO3(110) substrates. The films show total conductivity higher than the bulk material and apparent activation energy of about 0.12 eV in O2, lower than reported values for SrFeO3− δ films. The conductivity dependence with oxygen partial pressure shows a power dependence with an exponent close to +1/4, in agreement with expected point defect equilibrium. For a given oxygen partial pressure, the temperature coefficient of resistance (TCR) shows a low positive value of about 1.5–2.5 10−3 K−1, which is still suitable for resistive oxygen sensing applications. The transport properties of the films are discussed in view of their particular microstructure. [Copyright &y& Elsevier]

Abstract: The crystallization temperature of ultrathin films of a-Ge sandwiched between SiO2 layers increases with decreasing thickness and also with the heating rate. Based on this premise we used ultrafast heating to probe the amorphous-to-liquid transition in ultrathin films of amorphous Ge. Upon cooling, the melt solidifies into nanocrystalline Ge. We show that sensitive nanocalorimetric measurements can provide kinetic and thermodynamic information involved during the amorphous-to-liquid- and nanocrystalline-to-liquid-phase transitions in the Ge system. A 3-nm a-Ge ultrathin layer is condensed from an e-beam evaporator under high vacuum conditions onto the 180nm thick free-standing SiN x membranes of the calorimeters that form the calorimetric cells. The a-Ge film is sandwiched between a-SiO2 layers to minimize heterogeneous nucleation at the interfaces. Nanocalorimetric measurements are carried out in-situ inside the e-beam setup. The apparent heat capacity (Cp) of the a-Ge layers is extracted measuring the power released to the sample at fast heating rates (104–105 K/s), in the temperature range from 350 to 1200K. [Copyright &y& Elsevier]

Dense ceramic mixed ionic and electronic conducting membranes have been deposited by atmospheric spray-pyrolysis technique onto porous ceramic substrates. Perovskite oxide layers, i.e. manganites La1-xSrxMnO3, ferrites La1-xSrxFe1-y(Co,Ni)yO3, gallates La1-xSrxGa1-y(Co,Ni,Fe)yO3, cobaltites La1-xSrxCoO3 and related perovskites such as lanthanum nickelate La2NiO4 layers have been prepared. The structure, morphology and composition of the layers were characterised by XRD, SEM and WDS, respectively. Density and gas tightness of the layers were studied as a function of deposition process parameters, film thickness (from ∼0.5 to ∼3 μm) and preparation procedure. The presence of cracks and defects due to thermo-mechanical stresses applied during or after the preparation process were correlated with the membrane composition and the corresponding thermal expansion coefficient differences between substrates and membranes. [Copyright &y& Elsevier]

Abstract: We use spectroscopic ellipsometry to investigate crystallization of amorphous Ge thin films by thermal annealing of SiO2/a-Ge/SiO2 trilayer structures. We study the influence of both film thickness and annealing temperature on the effective dielectric functions of the Ge films, which are related to the film micro- and nanostructures. For annealing temperatures below 900 °C, all films remain continuous and consist of mixtures of amorphous and nanocrystallized Ge. The crystallite sizes can be estimated from the observed energy blueshift of the E 1 interband transition. Samples annealed at 900 °C display dielectric function spectra which differ from a bulk-like behavior. This suggests a variation in optical properties which is correlated to formation of discontinuous films of Ge nanocrystals. [Copyright &y& Elsevier]

Abstract: High-quality epitaxial thin films of Sr4Fe6O13 have been deposited on NdGaO3(001) substrates by pulsed laser deposition. The transport properties have been characterized by impedance spectroscopy. The temperature dependence of conductivity suggests a mechanism of adiabatic hopping by small polarons, in agreement with previous results in bulk samples. The transport properties show a clear dependence on the film thickness with the thinner films (10 nm) presenting conductivity values in oxygen one order of magnitude higher than the thicker ones (313 nm). We correlate this behaviour with the thickness dependence of the epitaxial strain. [Copyright &y& Elsevier]