The work function is the parameter of greatest interest in many technological applications involving charge exchange mechanisms at the interface. The possibility to produce samples with a controlled work function is then particularly interesting, albeit challenging. We synthetized nanostructured vanadium oxides films by a room temperature Supersonic Cluster Beam Deposition method, obtaining samples with tunable stoichiometry and work function (3.7-7 eV). We present an investigation of the electronic structure of several vanadium oxides films as a function of the oxygen content via in-situ Auger, valence-band photoemission spectroscopy and work function measurements. The experiments probed the partial 3d density of states, highlighting the presence of strong V3d-O2p and V3d-V4s hybridization which influence 3d occupation. We show how controlling the stoichiometry of the sample implies a control over work function, and that the access to nanoscale quantum confinement can be exploited to increase the work function of the sample relative to the bulk analogue. In general, the knowledge of the interplay among work function, electronic structure, and stoichiometry is strategic to match nanostructured oxides to their target applications.
Vanadium oxides are strongly correlated materials which display metal-insulator transitions as well as various structural and magnetic properties that depend heavily on oxygen stoichiometry. Therefore, it is crucial to precisely control oxygen stoichiometry in these materials, especially in thin films. This work demonstrates a high-vacuum gas evolution technique which allows for the modification of oxygen concentration in VOX thin films by carefully tuning thermodynamic conditions. We were able to control the evolution between VO2, V3O5, and V2O3 phases on sapphire substrates, overcoming the n…
We present and discuss an original method to synthesize disordered Nanostructured (NS) VO$_x$ films with controlled stoichiometry and tunable electronic structures. In these NS films, the original lattice symmetry of the bulk vanadium oxides is broken and atoms are arranged in a highly disordered structure . The stoichiometry-dependent disorder as a function of the oxygen concentration has been characterized by in-situ X-ray Absorption Near-Edge Structure (XANES) spectroscopy identifying the spectroscopic fingerprints. Results show structural rearrangements that deviate from the octahedral sym…
Crystal structure, cobalt and iron speciation and oxygen non-stoichiometry of La0.6Sr0.4Co1-yFeyO3-d nanorods for IT-SOFC cathodes
Pontificia Universidad Javeriana（波哥大耶稣会天主教大学）；Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica（康塞普西翁原子中心，国家原子能委员会）；Instituto de Nanociencia y Nanotecnología (INN), CNEA-CONICET（纳米科学与技术研究所，国家原子能委员会-国家科学研究和技术研究委员会）；CONICET / Laboratorio de Cristalografía Aplicada, Escuela de Ciencia y Tecnología, Universidad Nacional de Gral. San Martín（国家科学研究和技术研究委员会/应用晶体学实验室，科学与科技学院，圣马丁国立大学）；CNPEM, Laboratório Nacional de Luz Síncrotron（巴西纳米技术国家研究中心，同步光国家实验室）；Instituto de Física, Universidade de São Paulo（物理研究所，圣保罗大学）
New Sol-Gel Synthesis of Ordered Nanostructured Doped ZnO Films
报道了一种新的溶胶-凝胶法制备c轴取向的未掺杂和Co、Fe、Mn和V掺杂ZnO薄膜。溶胶由水合乙酸锌前体和二甲基甲酰胺（DMF）溶剂制备。将薄膜旋涂到亲水性蓝宝石衬底上，然后干燥，退火和后退火，产生几乎纯单轴ZnO微晶和高度的长程结构有序。六方微晶的特定取向被证明垂直和平行于衬底表面。钴掺杂导致柱状ZnO纳米晶的形成。钒掺杂薄膜形成尖晶石氧化物ZnAl 2 O 4，这是ZnO与蓝宝石衬底反应的结果。结构，光学和形态表征证明了高品质的薄膜。
Synthesis and Characterization of TiFe0.7-xMn0.3Vx (x=0.05, and 0.1) and Ti1-yTayFe0.7Mn0.3 (y=0.2, and 0.4) Nanostructured Metal Hydrides for Low Temperature Applications
MXenes are 2D transition metal carbides with high potential for overcoming limitations of conventional two-dimensional electronics. In this context, various MXenes have shown magnetic properties suitable for applications in spintronics, yet the number of MXenes reported so far is far smaller than their parental MAX phases. Therefore, we have studied the structural, electronic and magnetic properties of bimetallic and vacancy-ordered MXenes derived from a new $(V_{2/3}Zr_{1/3})_2AlC $ MAX phase to assess whether MXene exfoliation would return stable magnetic materials. In particular, we have in…
Strain engineering vanadium dioxide thin films is one way to alter this material's characteristic first order transition from semiconductor to metal. In this study we extend the exploitable strain regime by utilizing the very large lattice mismatch of 8.78 % occurring in the VO$_2$/RuO$_2$ system along the c axis of the rutile structure. We have grown VO$_2$ thin films on single domain RuO$_2$ islands of two distinct surface orientations by atomic oxygen-supported reactive MBE. These films were examined by spatially resolved photoelectron and x-ray absorption spectroscopy, confirming the corre…
