Reversible oxygen vacancies doping in (La0.7,Sr0.3)MnO3 microbridges by combined self-heating and electromigration

Combination of electric \ufb01elds and Joule self-heating is used to change the oxygen stoichiometry and promote oxygen vacancy drift in a freestanding (La,Sr)MnO 3 thin \ufb01lm microbridge placed in controlled atmosphere. By controlling the local oxygen vacancies concentration, we can reversibly switch our (La,Sr)MnO 3 -based microbridges from metallic to insulating behavior on timescales lower than 1 s and with small applied voltages (<5 V). The strong temperature gradients given by the microbridge geometry strongly con\ufb01ne the motion of oxygen vacancies, limiting the modi\ufb01ed region within the free-standing area. Multiple resistive states can be set by selected current pulses that determine different oxygen vacancies pro\ufb01les within the device. Qualitative analysis of device operation is also provided with the support of \ufb01nite element analysi

Thermoelectric properties of Zn4Sb3 intermetallic compound doped with Aluminum and Silver

The beta-phase Zn4Sb3 has attracted much attention because of its high thermoelectric performance in the intermediate temperature range thanks to disorder in the Zn lattice site. In this work are presented structural, thermal, electric and thermoelectric characterization of Zn4Sb3 pure and Ag, Al doped, prepared by a simple synthesis. Structural and microstructural analyses reveal homogeneous one-phases having compositions in agreement with the nominal ones. After thermoelectric characterization, Ag doping results mostly effective in lowering the resistivity and Seebeck coefficient value, by introducing holes in the system. On the other hand, the Al substitution yields a very small decrease of the Seebeck coefficient but, at the same time, a significant decrease of the thermal conductivity mainly due to the depressed phonon contribution. The thermal conductivity behavior is the main responsible for the good thermoelectric performances of (Zn0.33Al0.01)(4)Sb-3, whose thermoelectric figure of merit reaches the encouraging value of 0.23 at 260 K

Ballistic electron and photocurrent transport in Au/organic/Si(001) diodes with PDI8-CN2 interlayers

The authors use ballistic electron emission microscopy (BEEM) to probe hot-electron and photocurrent transport in Au/organic/n-Si(001) diodes incorporating the n-type perylene diimide semiconductor PDI8-CN2. For the case of an ultrathin organic interlayer, hot-electron injection is weak and can be detected only at randomly distributed nanosized domains, where BEEM provides electronic barrier heights of 3c0.67 and 3c0.94 eV, respectively. No ballistic transport is detected for devices with a 10 nm-thick interlayer. Regardless of the organic layer thickness, BEEM reveals laterally uniform contributions due to scanning tunneling microscopy-induced photocurrent (STM-PC), with a characteristic energy onset at 3c1.2 eV and a broad intensity peak in the 2-4 eV range. The authors give insight on such spectroscopic features by examination of temperature-dependent spectra and of literature data. This study shows that PDI8-CN2 limits the penetration of Au toward Si, likely due to stiff intermolecular interactions and reactivity of the cyano groups. Moreover, ballistic transmittance is remarkably suppressed and photocurrent transport takes place via defects or recombination centers. Our analysis of electronic and STM-PC fingerprints appears useful for the characterization of several organic-on-inorganic interfaces of interest for heterostructures and devices

Metal\u2013insulator transition in free-standing VO2/TiO2microstructures through low-power Joule heating

We investigated voltage bias-driven electronic phase switching from insulating to metallic states in the VO2 thin films having freestanding structures (FSS) and non-freestanding structures (N-FSS). By measuring the electrical power during switching under different thermal conditions, we found that the thermal coupling of the microstructures determined the spatial temperature distribution on the device and strongly affected the efficiency of the insulator-metal switching induced by the Joule effect. The power required for switching in the FSS was two orders lower than that for the N-FSS. This indicates that an appropriate design of the thermal flow is a fundamental issue for developing efficient switching and memristive devices

Fabrication and electromechanical actuation of epitaxial SrTiO3 (0 0 1) microcantilevers

We report on the fabrication, mechanical characterization and electrostatic actuation of dielectric STO(0 0 1) thin film microcantilevers (MCs). Finite element analysis (FEA) is used for mechanical analysis and for calculating the distribution and the magnitude of the dielectric forces on the actual devices. The actuation of insulating oxide microstructures is of potential interest in the field of ferroelectric/multiferroic materials as well as for developing novel detecting schemes on dielectric oxides. \ua9 2013 IOP Publishing Ltd

Inkjet printing of conducting silver patterns on alumina and insulating ceramic-glass by saline precursors

We used ink-jet printing technique to fabricate conducting silver circuits on two substrates of technological interest (alumina and insulating ceramic-glass) using a very simple and cost-effective reduction reaction of silver nitrate (AgNO3) aqueous solution followed by annealing in argon-5% hydrogen atmosphere. Commercial dishwashing detergent was added to the ink to act as surfactant. To achieve homogeneous and connected silver (Ag) patterns, we used a two-steps technique consisting of two printing and annealing steps. Indeed, the second printing step was used to fill up the voids formed during ink evaporation in the center of the first printed pattern due to the \ue2\u80\u9ccoffee ring effect\ue2\u80\u9d. We produced conducting Ag line patterns on alumina and insulating ceramic-glass with resistivity values of about 30 and 90 \uce\ubc\uce\ua9 cm, respectively, which are nearly 20 and 60 times higher than that of bulk silver. These results are preliminary for prototyping hybrid circuits on these ceramic substrates by inkjet technology

Multistate Memory Devices Based on Free-standing VO2/TiO2 Microstructures Driven by Joule Self-Heating

Two-terminal multistate memory elements based on VO2/TiO2 thin film microcantilevers are reported. Volatile and non-volatile multiple resistance states are programmed by current pulses at temperatures within the hysteretic region of the metal-insulator transition of VO2. The memory mechanism is based on current-induced creation of metallic clusters by self-heating of micrometric suspended regions and resistive reading via percolation

Nanopatterning process based on epitaxial masking for the fabrication of electronic and spintronic devices made of La0.67Sr0.33MnO3/LaAlO3/SrTiO3 heterostructures with in situ interfaces

The fabrication of oxide electronics devices is presently hindered by the lack of standardized and well established patterning procedures, applicable down to the nanoscale. In this work, the authors propose a procedure to obtain patterns with resolution around 100 nm on (La,Sr)MnO3/LaAlO3/SrTiO3 heterostructures. Our method is based on a multistep technique, which includes wet and dry etching, epitaxial masking, and e-beam lithography. Our procedure is devised to define independent patterns on the interfacial two dimensional electron gas and on the metallic top electrode, while preserving an all-in situ approach for the heterostructure growth. The authors show results on nanoscale devices based on (La,Sr)MnO3/LaAlO3/SrTiO3, suitable for oxide spintronics applications