Nanostructured vanadium oxide thin film with high TCR at room temperature for microbolometer

We systematically examined the effects of the substrate temperature (TS) and the oxygen pressure (PO2) on the structural and optical properties polycrystalline V O2 films grown directly on Si(100) substrates by pulsed-laser deposition. A rutile-type V O2 phase was formed at a TS ≥ 450 °C at PO2 values ranging from 5 to 20 mTorr, whereas other structures of vanadium oxides were stabilized at lower temperatures or higher oxygen pressures. The surface roughness of the V O2 films significantly increased at growth temperatures of 550 °C or more due to agglomeration of V O2 on the surface of the silicon substrate. An apparent change in the refractive index across the metal–insulator transition (MIT) temperature was observed in V O2 films grown at a TS of 450 °C or more. The difference in the refractive index at a wavelength of 1550 nm above and below the MIT temperature was influenced by both the TS and PO2, and was maximal for a V O2 film grown at 450 °C under 20 mTorr. Based on the results, we derived the PO2 versus 1/TS phase diagram for the films of vanadium oxides, which will provide a guide to optimizing the conditions for growth of V O2 films on silicon platforms.

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“…[1][2][3][4][5][6] For VO 2 , the MIT from a high-temperature metallic phase to a low-temperature insulating phase occurs at around 68…”

Section: Introductionmentioning

confidence: 99%

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Shibuya

Sawa

2015

AIP Advances

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“…V ANADIUM oxide (VO x ) thin films have been studied extensively due to their unique properties, among which the high temperature coefficient of resistance (TCR) is widely used in the microbolometers [1]. Considering the circuit driving capability and the required ratio of signal to noise for microbolometers, a resistivity of 0.1 to 10 · cm with a TCR >2%/K for VO x film is preferred [2].…”

Section: Introductionmentioning

confidence: 99%

Influence of Post-Annealing on Resistivity of VO_x Thin Film

Chen

Jiang

2014

IEEE Electron Device Lett.

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The influence of post-annealing (PA) on the resistivity of 55-nm VO x film (∼1.2 · cm) is investigated in this letter. For the first time, it is demonstrated that PA can effectively lower the film resistivity but with a constant temperature coefficient of resistance (TCR) by enhancing the formation of embedded VO 2 nanocrystals (NCs), while keeping the VO x film composition unchanged. A model based on charge hopping between VO 2 NCs is proposed to illustrate the relationship between the temperature-dependent resistivity and the constant TCR.Index Terms-Vanadium oxide, nanocrystal, temperature coefficient of resistance, post-annealing.

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“…Existing high-performance temperature-sensitive materials, such as vanadium oxide, have temperature coefficient of electrical resistance (TCR) on the order of −6% K −1 at room temperature (4). These materials derive their properties from changes of their crystal structure during semiconductor to metal transitions (5).…”

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confidence: 99%

Plant nanobionic materials with a giant temperature response mediated by pectin-Ca ²⁺

Giacomo

Daraio

Maresca

2015

Proc. Natl. Acad. Sci. U.S.A.

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Conventional approaches to create biomaterials rely on reverse engineering of biological structures, on biomimicking, and on bioinspiration. Plant nanobionics is a recent approach to engineer new materials combining plant organelles with synthetic nanoparticles to enhance, for example, photosynthesis. Biological structures often outperform man-made materials. For example, higher plants sense temperature changes with high responsivity. However, these properties do not persist after cell death. Here, we permanently stabilize the temperature response of isolated plant cells adding carbon nanotubes (CNTs). Interconnecting cells, we create materials with an effective temperature coefficient of electrical resistance (TCR) of −1,730% K −1 , ∼2 orders of magnitude higher than the best available sensors. This extreme temperature response is due to metal ions contained in the egg-box structure of the pectin backbone, lodged between cellulose microfibrils. The presence of a network of CNTs stabilizes the response of cells at high temperatures without decreasing the activation energy of the material. CNTs also increase the background conductivity, making these materials suitable elements for thermal and distance sensors.temperature sensor | plant nanobionics | carbon nanotubes | iontronics | biomaterials M aterials that respond sensitively to temperature variations are used in several applications that range from electrical temperature sensors (1) to microbolometers for thermal cameras (2, 3). Existing high-performance temperature-sensitive materials, such as vanadium oxide, have temperature coefficient of electrical resistance (TCR) on the order of −6% K −1 at room temperature (4). These materials derive their properties from changes of their crystal structure during semiconductor to metal transitions (5). Higher sensitivities have been pursued by exploiting quantum effects (6-9), e.g., in carbon nanotube (CNT) composites (1). However, such composites reach lower TCRs because CNTs are embedded in an insulating polymeric matrix (1).Variations of the ambient temperature influence the biopotential of living plants (10,11). Experiments performed in vivo on a maple tree (Acer saccharum) showed an exponential correlation between the tree's branch electrical resistance and temperature (10). This behavior has been attributed to ionic conductivity occurring in plant cell walls (11). The plant cell wall has a highly complex macromolecular architecture with very dynamic structural and physiological properties (12). The cell wall, positioned outside the plasma membrane (13), is composed of carbohydrates such as cellulose microfibrils (14) with diameters as small as 3.0 nm (15) and hemicellulose interconnected with pectin. Pectins are composed of pectic polysaccharides rich in galacturonic acid that influence properties such as porosity, surface charge, pH, and ion balance and therefore are critical for ion transport within the cell wall. Pectins contain multiple negatively charged saccharides that bind cations, such as Ca 2+, that for...

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Nanostructured vanadium oxide thin film with high TCR at room temperature for microbolometer

Cited by 108 publications

References 25 publications

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Influence of Post-Annealing on Resistivity of VO_x Thin Film

Plant nanobionic materials with a giant temperature response mediated by pectin-Ca ²⁺

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Nanostructured vanadium oxide thin film with high TCR at room temperature for microbolometer

Cited by 108 publications

References 25 publications

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Influence of Post-Annealing on Resistivity of VO x Thin Film

Plant nanobionic materials with a giant temperature response mediated by pectin-Ca 2+

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Influence of Post-Annealing on Resistivity of VO_x Thin Film

Plant nanobionic materials with a giant temperature response mediated by pectin-Ca ²⁺