Thermal conductivity of sputtered and evaporated SiO2 and TiO2 optical coatings

Cahill, David G.; Allen, Thomas H.

doi:10.1063/1.112355

Cited by 151 publications

(98 citation statements)

References 14 publications

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“…For example, diamond and c-BN have an A U of 0.06 and 0.19, respectively [58], far less than that of m-HfO 2 . Data are from a: [53] (this experimental value is for films); b: [54]; c: [11]; d: [55]. , and 4, we find that the bulk modulus is more anisotropic than Young's modulus, which in turn is more anisotropic than the minimum thermal conductivity.…”

Section: Elastic Anisotropymentioning

confidence: 99%

Elastic properties, hardness, and anisotropy in baddeleyite IVTMO2 (M=Ti, Zr, Hf)

Chen

Liang

et al. 2015

Sci. China Mater.

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and HfO 2 thin films. Other researchers have investigated the transformation from monoclinic phase to tetragonal phase in HfO 2 [5], as well as its mechanical [11], optical, and elastic properties [12]. Even with this range of study, some properties of IVTMO 2 , particularly their mechanical properties, are not well understood . For example, elastic anisotropy in thin films usually leads to microcracks, and differences in thermal expansion between a film and matrix might induce a dropping of the film from the matrix.Zhao et al. [10] reported that bulk ZrO 2 has three crystalline structures at normal pressure: cubic (2300−2680°C), tetragonal (1170−2300°C), and monoclinic (<1170°C). Bulk HfO 2 has only two crystalline structures: tetragonal (1750−2800°C) and monoclinic (<1750°C). The most abundant polymorph of TiO 2 found in nature is rutile, and at room temperature it is stable up to 12 GPa, where it directly converts to the baddeleyite-type (monoclinic) phase [13]. Because m-HfO 2 has a larger bulk modulus than the other two metal dioxides [12], it was expected to have high hardness. The bulk modulus was once thought to be good predictor of hardness. Although it is true that a hard material must have a high modulus [14], it is a common misconception that an incompressible material is a hard one. For example, osmium has only a twentieth the hardness of diamond, though its bulk modulus is comparable to diamond, making it one of the most incompressible materials known.It is now well recognized that high bulk and shear moduli do not guarantee high hardness. Other factors-including high electron density, short bond length, high degree of covalent bonding, and near-isotropic deformation-usually dominate a material's intrinsic hardness [15]. Thus, it is important to thoroughly investigate baddeleyite-type IVTMO 2 (we henceforth refer to these m-MO 2 materials as m-TiO 2 , m-ZrO 2 , and m-HfO 2 ), especially their hardness, elasticity, and anisotropy. To our best knowledge, there are no systemic studies of monoclinic metal dioxides, which are stable at room temperature. In the past decade,In this article, we used plane-wave density functional theory to investigate the elasticity, anisotropy, and minimum thermal conductivities of baddeleyite type IVTMO2 (m-TiO2, m-ZrO2, and m-HfO2). The elastic constants and modulus, Poisson's ratio, hardness, sound speed, Debye temperature, and minimum thermal conductivities at high temperature were calculated. These calculations show that m-MO2 is not superhard, with a hardness range of about 8-13 GPa. Among these materials, m-TiO2 is the hardest, while m-HfO2 is the least hard. Their elastic and plastic anisotropy are given in detail. Moreover, the m-HfO2 thin film is the most likely to develop microcracks during preparation because it has the highest elastic anisotropy. Among the three dioxides, m-HfO2 is the best thermal barrier because it has the lowest thermal conductivity.

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Section: Elastic Anisotropymentioning

confidence: 99%

Elastic properties, hardness, and anisotropy in baddeleyite IVTMO2 (M=Ti, Zr, Hf)

Chen

Liang

et al. 2015

Sci. China Mater.

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“…1(c), where the temperature rise across any two nodes is proportional to the product of the dissipated power and the thermal resistance between the nodes. 34 Most substrate dielectrics considered in this work have low thermal conductivity 35 (e.g. ~1.4 Wm -1 K -1 for SiO2 at room temperature) and they tend to dominate the heat flow path, although the precise balance of the thermal resistances also depends on the substrate thickness and interface quality or TBR.…”

Section: A Transport Modelmentioning

confidence: 99%

Theoretical analysis of high-field transport in graphene on a substrate

Serov

Ong

Fischetti

et al. 2014

Journal of Applied Physics

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We investigate transport in graphene supported on various dielectrics (SiO2, BN, Al2O3, HfO2) through a hydrodynamic model which includes self-heating and thermal coupling to the substrate, scattering with ionized impurities, graphene phonons and dynamically screened interfacial plasmonphonon (IPP) modes. We uncover that while low-field transport is largely determined by impurity scattering, high-field transport is defined by scattering with dielectric-induced IPP modes, and a smaller contribution of graphene intrinsic phonons. We also find that lattice heating can lead to negative differential drift velocity (with respect to the electric field), which can be controlled by changing the underlying dielectric thermal properties or thickness. Graphene on BN exhibits the largest highfield drift velocity, while graphene on HfO2 has the lowest one due to strong influence of IPP modes.

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“…The pristine SiO2 and TiO2 as well as the composite SiO2-TiO2 films have been extensively studied because of their extraordinary optical, catalytic, electrical and mechanical properties [35][36][37][38]. However, their gas sensing performance for NH3 has not been widely exploited.…”

Section: Introductionmentioning

confidence: 99%

NH3 sensing property and mechanisms of quartz surface acoustic wave sensors deposited with SiO2, TiO2, and SiO2-TiO2 composite films

Tang

et al. 2018

Sensors and Actuators B: Chemical

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Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. and SiO2-TiO2 films showed positive frequency shifts, whereas SiO2 film exhibits a negative frequency shift to NH3 gas. it is believed that the negative frequency shift was mainly caused by the increase of NH3 mass loading on the sensitive film while the positive frequency shift was associated to the condensation of the hydroxyl groups (-OH) on the film making the film stiffer and lighter, when exposed to NH3 gas. It demonstrated that humidity played a significant factor on the sensing performance. Comparative studies exhibited that the sensor based on the composite SiO2-TiO2 film had a much better sensitivity to NH3 at a low concentration level (1 ppm) with a response of 2 KHz, and also showed fast response and recovery, excellent selectivity, stability and reproducibility. Accepted Manuscript

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Thermal conductivity of sputtered and evaporated SiO2 and TiO2 optical coatings

Cited by 151 publications

References 14 publications

Elastic properties, hardness, and anisotropy in baddeleyite IVTMO2 (M=Ti, Zr, Hf)

Elastic properties, hardness, and anisotropy in baddeleyite IVTMO2 (M=Ti, Zr, Hf)

Theoretical analysis of high-field transport in graphene on a substrate

NH3 sensing property and mechanisms of quartz surface acoustic wave sensors deposited with SiO2, TiO2, and SiO2-TiO2 composite films

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