Electronic structure and surface properties of the mixed-valence doughnut shaped polyoxomolybdate nanocapsule Mo57V6

Fernández, Jorge A.; Miró, Pere; Bonet-Ávalos, Josep; Bó, Carles; Poblet, Josep M.

doi:10.1016/j.ica.2010.07.019

Cited by 5 publications

(3 citation statements)

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“…This is better demonstrated in the occupied POM molecular orbitals and the Coulomb charging energy of the formed molecular islands. 38 For low temperatures the condition k B T < DE for observation of potential changes due to the sequential charging of the POM nanoislands is satisfied for a wider range of dimensions (this is important since the POM islands are not strictly mono-dispersed). As a result, the size scale limit of detectable nanostructures increases and single electron effects can be observed.…”

Section: Dynamic I-v Measurements and Electronic Structure Considementioning

confidence: 99%

Tungsten polyoxometalate molecules as active nodes for dynamic carrier exchange in hybrid molecular/semiconductor capacitors

Balliou

Douvas

Normand

et al. 2014

Journal of Applied Physics

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Superhydrophobicity on transparent fluorinated ethylene propylene films with nano-protrusion morphology by Ar+ O2 plasma etching: Study of the degradation in hydrophobicity after exposure to the environment Photoresist modifications by plasma vacuum ultraviolet radiation: The role of polymer structure and plasma chemistry J. Vac. Sci. Technol. B 28, 993 (2010); 10.1116/1.3484249Ion beam deposition of tantalum pentoxide thin film at room temperature In this work we study the utilization of molecular transition metal oxides known as polyoxometalates (POMs), in particular the Keggin structure anions of the formula PW 12 O 40 3À , as active nodes for potential switching and/or fast writing memory applications. The active molecules are being integrated in hybrid Metal-Insulator/POM molecules-Semiconductor capacitors, which serve as prototypes allowing investigation of critical performance characteristics towards the design of more sophisticated devices. The charging ability as well as the electronic structure of the molecular layer is probed by means of electrical characterization, namely, capacitance-voltage and current-voltage measurements, as well as transient capacitance measurements, C (t), under step voltage polarization. It is argued that the transient current peaks observed are manifestations of dynamic carrier exchange between the gate electrode and specific molecular levels, while the transient C (t) curves under conditions of molecular charging can supply information for the rate of change of the charge that is being trapped and de-trapped within the molecular layer. Structural characterization via surface and cross sectional scanning electron microscopy as well as atomic force microscopy, spectroscopic ellipsometry, UV and Fourier-transform IR spectroscopies, UPS, and XPS contribute to the extraction of accurate electronic structure characteristics and open the path for the design of new devices with on-demand tuning of their interfacial properties via the controlled preparation of the POM layer. V C 2014 AIP Publishing LLC.

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Section: Dynamic I-v Measurements and Electronic Structure Considementioning

confidence: 99%

Tungsten polyoxometalate molecules as active nodes for dynamic carrier exchange in hybrid molecular/semiconductor capacitors

Balliou

Douvas

Normand

et al. 2014

Journal of Applied Physics

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“…A much more smaller water cluster (H 2 O) 6 , which is encapsulated inside the doughnut-shaped [H 3 Mo 57 V 6 (NO) 6 O 183 (H 2 O) 18 ] 21À anion, was also analysed by MD 260. 12.4.…”

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confidence: 99%

Structure, properties and reactivity of polyoxometalates: a theoretical perspective

et al. 2012

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In the thematic review dedicated to polyoxometalate (POM) chemistry published in Chemical Reviews in 1998, no contribution was devoted to theory. This is not surprising because computational modelling of molecular metal-oxide clusters was in its infancy at that time. Nowadays, the situation has completely changed and modern computational methods have been successfully applied to study the structure, electronic properties, spectroscopy and reactivity of POM clusters. Indeed, the progress achieved during the past decade has been spectacular and herein we critically review the most important papers to provide the reader with an almost complete perspective of the field.

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“…Resonance naturally occurs at gate bias voltages where the Al Fermi level is aligned with an electronic state level of the POM nanoislands. The POM nanoislands electronic state levels should be determined both by quantum confinement in the occupied POM molecular orbitals and the Coulomb charging energy of the formed molecular islands [241]. For low temperatures the condition k B T<∆ for observation of potential changes due to the sequential charging of the POM nanoislands is satisfied for a wider range of dimensions (this is important since the POM islands are not strictly mono-dispersed).…”

Section: 14)mentioning

confidence: 99%

Hybrid molecular solid state memories and electronic nanodevices based on polyoxometalates and other molecules of reversible redox activity

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According to ITRS 2.0 2015, memory technologies will continue todrive pitch scaling and highest transistor count. As DRAM products areexpected to reach their scaling limits by 2024, and unless some majorbreakthrough occurs, flash memory is expected to lead the semiconduc-tor industry towards the next revolution in transistor density.Inspired from this fact, this work focuses on molecular flash mem-ories and logic switching molecular networks which, among all emerg-ing technology candidates, are considered particularly promising due totheir ability for reduction of size per cell and solution processing (lowcost, injection-printing friendly), conceptual compatibility with photonicaddressing due to molecular photosensitivity, multilevel storage, high in-formation density, quick write-read operations, low power consumption,mechanical flexibility, bottom-up fabrication logic (overcoming the litho-graphic patterning constrains), conceptual non-binary data representationand properties’ tunability through chemical tailoring.Molecular electronic devices are fabricated via a combination of bottom-up layer-by-layer nanofabrication and self-assembly with CMOS platformlithography in order to provide a low cost large-scale route towards ex-tension of the functional value of Si-based platforms.Tungsten Polyoxometalates (POM, [PW 12 O 40 ] 3− ) of the Keggin classare being self-arranged both on nanocrystal and hyperstructure level ina rational way resulting in layers of tunable spatial correlation length.The hyperstructures exhibit tunable valence and conduction bands and,hence, adjustable electronic properties directly related to the extent ofcrystallization of their building blocks.Dimensional crossover-driven insulator-to-semimetal transitions canbe enforced in these hyperstructures via tuning the extent of crystalliza-tion in solution. Being able to transport or confine charge at will, thesehyperstructures constitute ideal candidates for alternative molecule-basedsolution-printed circuitry components and transistor channels.Hybrid CMOS/molecular memory devices based on the parallel platearchitecture are fabricated, characterized and tested. Each memory el-ement contains a planar hyperstructure of molecules (typically several millions) that can store charge having multiple times the charge densityof a typical DRAM capacitor.Transition-metal-oxide hybrids composed of high surface-to-volumeratio Ta 2 O 5 matrices and tungsten POMs are investigated as a chargestorage composite in molecular nonvolatile capacitive memory cells. En-hanced internal scattering of carriers results in a memory window of 4.0V for the write state and a retention time around 10 4 s without blockingmedium.Differential distance of molecular trapping centers from the cells gateand electronic coupling to the space charge region of the underlying Sisubstrate are being identified as critical parameters for enhanced electrontrapping for the first time in such devices.The incorporation of a molecular-friendly blocking oxide that facili-tates long term retention while suppressing cross-talking, is performedthrough realization of a multi-functional oxide stack (SiO 2 /hybrid Ta 2 O 5 -POM transition metal oxide/Al 2 O 3 ) that takes parallel advantage of photo-nically-addressed phononic modes to boost information storage and reachmolecular states that were previously non-available. A 37 % informationdensity increase is attained via phononic pumping, while the memorywindow reaches 7.0 V, corresponding to ∼ 4 × 10 14 cm 2 charging nodesable to carry 65-195 μCb/cm 2 . Ability of multi-state addressing and writespeed of 10 ns are being documented for the packed cell.The fabricated high performance non-volatile memories are the firstdocumented CMOS-compatible long term (10 years criterion satisfaction)retention molecular capacitive cell of its kind.Following a different approach, brain-inspired, neural systems per-forming in networks and data-centric non-Von Neumann processing areamong the latest trends for non-conventional approaches in the semicon-ductor industry. We focus on hybrid molecular-nanoparticle networksthat exploit the massive parallelism of designless interconnected net-works of locally active components, obviating the need for expensivelithographic steps.Molecular multi-junction networks comprising of gold nanoparticles(AuNPs) of diam.∼1.4 nm, electronically linked by means of copper 3-diethylamino-1-propylsulphonamide sulfonic acid substituted phthalocya-nine (CuPcSu) molecules are fabricated and studied.When electrons flow through the non-linked nanoparticle arrays, theyexperience on-site Coulomb repulsion and are strongly localized, with lo-calization length (ξ=0.7 nm). Under dynamic excitation the system under-goes Coulomb oscillations, while the introduction of CuPcSu moleculesresults in the formation of a network of multiple molecular/Au nanojunc-tions and conductance increases by 5 orders of magnitude. This switching behavior functions on reversible red-ox reactions andpushes carriers in a weak localization state. In this state electrons spreadover several junctions and all temperature scaled current vs voltage curves,J/T^(1+α) vs eV/kT, collapse in one universal curve, characterizing the net-work and the extent of its disorder.On the other hand, the strongly non-linear I-V response and negativedifferential resistance of drop-cast nanojunction 3-d arrays makes themsuitable platforms for logic function exhibition. Common miniaturiza-tion bottlenecks such as capacitive crosstalk, are embraced as exploitablephysical processes, that can lead to robust computational functionality.The networks can be configured on-flight with pulses as quick as 10 nsto modify their resistance between two discrete levels. Both levels can beaddressed real time utilizing patterned nano-electrode pairs and readingvoltage of the order of 500 mV. The networks are able to perform as atwo-input “then-if” logic gates.

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Electronic structure and surface properties of the mixed-valence doughnut shaped polyoxomolybdate nanocapsule Mo57V6

Cited by 5 publications

References 51 publications

Tungsten polyoxometalate molecules as active nodes for dynamic carrier exchange in hybrid molecular/semiconductor capacitors

Tungsten polyoxometalate molecules as active nodes for dynamic carrier exchange in hybrid molecular/semiconductor capacitors

Structure, properties and reactivity of polyoxometalates: a theoretical perspective

Hybrid molecular solid state memories and electronic nanodevices based on polyoxometalates and other molecules of reversible redox activity

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