Near Room‐Temperature Memory Devices Based on Hybrid Spin‐Crossover@SiO<sub>2</sub> Nanoparticles Coupled to Single‐Layer Graphene Nanoelectrodes

Holovchenko, Anastasia; Dugay, Julien; Giménez‐Marqués, Mónica; Torres‐Cavanillas, Ramón; Coronado, Eugenio; Zant, Herre S. J. van der

doi:10.1002/adma.201600890

Cited by 95 publications

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“…A state with higher conductance was observed at T = 325 K, which has to be associated to the LS state, while a lower conductance state was observed at T = 355 K (measured in the cooling mode) for the HS state (Figure e). This result is in good agreement with previous studies performed in related SCO systems . The unprecedented sharp transition in the conductance can be explained by considering the coexistence of several factors, namely i) the preservation of thermal bistability in small SCO nanoparticles (4 nm) of the Fe‐triazole series; ii) a reinforcement of the elastic interactions occurring at the core–shell interfaces because of the reduced sizes of the NPs; and iii) the excellent thermal conductivity of the Au NP centers that are expected to provide a homogeneous and efficient heat transfer.…”

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confidence: 91%

Design of Bistable Gold@Spin‐Crossover Core–Shell Nanoparticles Showing Large Electrical Responses for the Spin Switching

et al. 2019

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Of particular interest are those SCO materials displaying a hysteretic behavior in their spin transition since they can be useful as components of nonvolatile memory devices. [6] In order to read-out the spin state in these devices, materials with large electrical responses, preferably displaying hysteretic spin transitions occurring near room temperature, are required. However, the SCO electronic devices reported to date, based on micrometric particles, have typically shown a gradual hysteresis in the conductance as well as very low electrical responses, owing to the insulating nature of the SCO material. [7,8] This situation becomes even more complex when the SCO system is downscaled to the nanometer or single molecule range since, under these circumstances, the hysteretic behavior observed in the bulk is generally lost. [9] Here the chemical design of core-shell nanoparticles (NPs) formed by a metallic Au core and a SCO shell is undertaken. Despite the extensive works performed on core-shell NPs, [10][11][12] nanostructures formed by a metallic core and a molecular SCO shell are unprecedented. In addition, as compared to previous examples that contain simple SCO entities deposited or contacted to gold surfaces/electrodes, [13][14][15][16][17] the core-shell configuration reported here is expected to combine in a single nanostructure the metallic behavior of the core with the insulating behavior of the SCO shell. In these hybrid nanostructures, the appropriate selection of the SCO material should warrant the maintenance of a cooperative spin transition at the nanoscale, while the metallic core is expected to make these novel nanostructures more conductive. As SCO material the system of choice has been the well-known iron(II)-triazole coordination polymer of formula [Fe(Htrz) 2 (trz)](BF 4 ) (Htrz = 1,2,4-triazole). [18,19] This SCO material exhibits large and abrupt thermal hysteresis occurring near room temperature. Furthermore, its well-established miniaturization protocol, [20][21][22] enables the maintenance of the cooperative spin transition features in NPs as small as 4 nm. [23] These NPs have already been integrated into electronic devices, showing a detectable conductivity change during the SCO transition. Thus, single NP devices (NP mean size of 10 nm) showed an ON/OFF ratio in the A simple chemical protocol to prepare core-shell gold@spin-crossover (Au@SCO) nanoparticles (NPs) based on the 1D spin-crossover [Fe(Htrz) 2 (trz)](BF 4 ) coordination polymer is reported. The synthesis relies on a two-step approach consisting of a partial surface ligand substitution of the citrate-stabilized Au NPs followed by the controlled growth of a very thin layer of the SCO polymer. As a result, colloidally stable core@ shell spherical NPs with a Au core of ca. 12 nm and a thin SCO shell 4 nm thick, are obtained, exhibiting a narrow distribution in sizes. Differential scanning calorimetry proves that a cooperative spin transition in the range 340-360 K is maintained in these Au@SCO NPs, in full agreement with the v...

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Design of Bistable Gold@Spin‐Crossover Core–Shell Nanoparticles Showing Large Electrical Responses for the Spin Switching

et al. 2019

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“…This problem will be addressed in the second part of this review, while the third part will be devoted to examples of successful integration of SCO nanomaterials into devices. The most advanced and most straightforward device concepts use photonic principles—mainly for sensing purposes, but recent results revealed promising perspectives also for applications in electronic junctions and mechanical actuators . At this point it must be noted that, in strong connection with the development of SCO nanomaterials, there has been a significant experimental and theoretical progress also in exploring the properties of single isolated SCO molecules on surfaces with the primary aim to use them in single molecule electronic devices.…”

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Spin Crossover Nanomaterials: From Fundamental Concepts to Devices

et al. 2017

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Nanoscale spin crossover materials capable of undergoing reversible switching between two electronic configurations with markedly different physical properties are excellent candidates for various technological applications. In particular, they can serve as active materials for storing and processing information in photonic, mechanical, electronic, and spintronic devices as well as for transducing different forms of energy in sensors and actuators. In this progress report, a brief overview on the current state-of-the-art of experimental and theoretical studies of nanomaterials displaying spin transition is presented. Based on these results, a detailed analysis and discussions in terms of finite size effects and other phenomena inherent to the reduced size scale are provided. Finally, recent research devices using spin crossover complexes are highlighted, emphasizing both challenges and prospects.

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“…Dielectrophoresis (DEP) consists in the directed motion of dielectric and polarizable particles properly dispersed within a liquid medium under the influence of an electric field gradient. Such a gradient can be generated by the application of an alternating voltage between two electrodes and has been used before to trap low-dimensional objects like nanoparticles [26][27][28] , carbon nanotubes [29][30][31] , nanoribbons 32 and nanowires 33 . We show that the lamellar structure of franckeite is preserved after DEP, something a priori not straightforward for heterostructures formed from individual layers with different polarizabilities.…”

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confidence: 99%

Simultaneous assembly of van der Waals heterostructures into multiple nanodevices

et al. 2018

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van der Waals heterostructures (vdWH) are made of different two-dimensional (2D) layers stacked on top of each other, forming a single material with unique properties that differ from those of the individual 2D constituent layers, and that can be modulated through the interlayer interaction. These hetero-materials can be artificially made by mechanical stamping, solution processing or epitaxial growth. Alternatively, franckeite has been recently described as an example of a naturally-occurring vdWH that can be exfoliated down to nanometer thicknesses. Research on vdWHs has so far been limited to manually exfoliated and stamped individual devices. Here, a scalable and fast method to fabricate vdWH nanodevices from liquid phase exfoliated nanoflakes is reported. The transport and positioning of the flakes into localized submicrometer structures is achieved simultaneously in multiple devices via a dielectrophoretic process. The complex vdWH is preserved after dielectrophoresis and the properties of the resulting field-effect transistors are equivalent to those fabricated via mechanical exfoliation and stamping. The combination of liquid phase exfoliation and dielectrophoretic assembly is particularly suited for the study of vdWHs and applications where large-scale fabrication is required.

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Near Room‐Temperature Memory Devices Based on Hybrid Spin‐Crossover@SiO₂ Nanoparticles Coupled to Single‐Layer Graphene Nanoelectrodes

Cited by 95 publications

References 31 publications

Design of Bistable Gold@Spin‐Crossover Core–Shell Nanoparticles Showing Large Electrical Responses for the Spin Switching

Design of Bistable Gold@Spin‐Crossover Core–Shell Nanoparticles Showing Large Electrical Responses for the Spin Switching

Spin Crossover Nanomaterials: From Fundamental Concepts to Devices

Simultaneous assembly of van der Waals heterostructures into multiple nanodevices

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Near Room‐Temperature Memory Devices Based on Hybrid Spin‐Crossover@SiO2 Nanoparticles Coupled to Single‐Layer Graphene Nanoelectrodes

Cited by 95 publications

References 31 publications

Design of Bistable Gold@Spin‐Crossover Core–Shell Nanoparticles Showing Large Electrical Responses for the Spin Switching

Design of Bistable Gold@Spin‐Crossover Core–Shell Nanoparticles Showing Large Electrical Responses for the Spin Switching

Spin Crossover Nanomaterials: From Fundamental Concepts to Devices

Simultaneous assembly of van der Waals heterostructures into multiple nanodevices

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Product

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Near Room‐Temperature Memory Devices Based on Hybrid Spin‐Crossover@SiO₂ Nanoparticles Coupled to Single‐Layer Graphene Nanoelectrodes