Properties of Sapphire

Dobrovinskaya, Elena R.; Lytvynov, Leonid A.; Pishchik, Valerian

doi:10.1007/978-0-387-85695-7_2

Cited by 83 publications

(57 citation statements)

References 35 publications

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“…Fig. S6, as well as predictions for silicon from other theoretical calculations based on similar approaches 20,41 and experimental data for both silicon 42 and sapphire 43 . Our calculations are in good agreement with these previous works.…”

Section: S4 Thermal Conductivity and Phonon Mean Free Path Spectra Fsupporting

confidence: 63%

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A New Regime of Nanoscale Thermal Transport: Collective Diffusion Counteracts Dissipation Inefficiency

Yamanouchi

Cundiff

Vivie‐Riedle

et al. 2014

19th International Conference on Ultrafast Phenomena

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Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well as for many technological applications including thermal management in nanoelectronics, thermoelectric devices, nano-enhanced photovoltaics and nanoparticle-mediated thermal therapies. Thermal transport at the nanoscale is fundamentally different from that at the macroscale and is determined by the distribution of carrier mean free paths in a material, the length scales of the heat sources, and the distance over which heat is transported. Past work has shown that Fourier's law for heat conduction dramatically over-predicts the rate of heat dissipation from heat sources with dimensions smaller than the mean free path of the dominant heat-carrying phonons. In this work, we uncover a new regime of nanoscale thermal transport that dominates when the separation between nanoscale heat sources is small compared with the dominant phonon mean free paths. Surprisingly, the interplay between neighboring heat sources can facilitate efficient, diffusive-like heat dissipation, even from the smallest nanoscale heat sources. This finding suggests that thermal management in nanoscale systems including integrated circuits might not be as challenging as projected. Finally, we demonstrate a unique and new capability to extract mean free path distributions of phonons in materials, allowing the first experimental validation of differential conductivity predictions from first-principles calculations.2

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Section: S4 Thermal Conductivity and Phonon Mean Free Path Spectra Fsupporting

confidence: 63%

“…The red dots in (a) represent the measured thermal conductivity of isotope-enriched silicon by Inyushkin et al 42 while the orange and green curves are other previous theoretical calculations 20,41 . The red dots in (b) show the experimentally measured thermal conductivity for sapphire 43 .…”

mentioning

confidence: 99%

A New Regime of Nanoscale Thermal Transport: Collective Diffusion Counteracts Dissipation Inefficiency

Yamanouchi

Cundiff

Vivie‐Riedle

et al. 2014

19th International Conference on Ultrafast Phenomena

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“…While patterning of nanowires in transparent conductive In 2 O 3 has been demonstrated using FIB, the conductivity modulation was limited to 4 orders of magnitude 28,29 . Here, we show nanopatterning of conductive zones in highly insulating Al 2 O 3 , achieving a conductivity modulation of 14 orders of magnitude (see Supporting Information) 30 . To the best of our knowledge, this is the highest reported change in conductivity using FIB.…”

Section: Correspondence: Hmohseni@northwesternedumentioning

confidence: 81%

Giant Conductivity Modulation of Aluminum Oxide Using Focused Ion Beam

Bianconi¹,

Park²,

Mohseni

2019

ACS Appl. Electron. Mater.

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Precise control of the conductivity of semiconductors through doping has enabled the creation of advanced electronic devices, similarly, the ability to control the conductivity in oxides can enable novel advanced electronic and optoelectronic functionalities. While this was successfully shown for moderately insulating oxides, such as In 2 O 3 , a reliable method for increasing the conductivity of highly insulating, wide bandgap dielectrics, such as aluminum oxide (Al 2 O 3 ), has not been reported yet. Al 2 O 3 is a material of significant technological interest, permeating diverse fields of application, thanks to its exceptional mechanical strength and dielectric properties. Here we present a versatile method for precisely changing the conductivity of Al 2 O 3 . Our approach greatly exceeds the magnitude of the best previously reported change of conductivity in an oxide (In 2 O 3 ). With an increase in conductivity of about 14 orders of magnitude, our method presents about 10 orders of magnitude higher change in conductivity than the best previously reported result. Our method can use focused ion beam to produce conductive zones with nanoscale resolution within the insulating Al 2 O 3 matrix. We investigated the source of conductivity modulation and identified trap-assisted conduction in the ion damage-induced defects as the main charge transport mechanism. Temperature-dependency of the conductivity and optical characterization of the patterned areas offer further insight into the nature of the conduction mechanism. We also show that the process is extremely reproducible and robust against moderate annealing temperatures and chemical environment. The record conductivity modulation, combined with the nanoscale patterning precision allows the creation of conductive zones within a highly insulating, mechanically hard, chemically inert, and bio-compatible matrix, which could find broad applications in electronics, optoelectronics, and medical implants.Aluminum oxide (Al 2 O 3 ) is one of the most widely employed dielectric materials, thanks to its excellent insulating properties 1 , mechanical hardness and resistance 2 , and biocompatibility 2,3 , with applications ranging from device passivation 1,4-8 , MOSFET gate 9-13 , to biomedical implants and antifouling passivation 2,3,14,15 . Electrical functionalization of Al 2 O 3 via reliable and spatially-accurate control of its conductivity could enable novel sensing technologies encompassing electrical contacts embedded in a mechanically hard, chemically inert, and electrically insulating dielectric matrix. Examples of such technological applications include photon emission and detection 7,16-19 , low-energy in-terconnects 20-22 , energy conversion 1,23,24 , and implantable devices [25][26][27] . We here present an effective method for the non-subtractive nanopatterning of electrically conductive wires and other features embedded in a dielectric Al 2 O 3 substrate, using focused ion beam (FIB). While patterning of nanowires in transparent conductive In 2 O 3 has been ...

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“…The observed density ranged from 99.96% to 100.02% of the theoretical value of 3.986 g∕cm 3 . The theoretical value is calculated for sapphire with a formula mass of 101.961 g∕mol and rhombohedral cell dimensions a ¼ 0.4758 nm and c ¼ 1.2991 nm at 26°C with six formulas per unit cell and unit cell volume a 2 c ffiffi ffi 3 p ∕2.…”

Section: Methodsmentioning

confidence: 99%

“…The crystal has threefold rotational symmetry about the c-axis (the optic axis) in Fig. 1 and twofold rotational symmetry about the three a directions perpendicular to c. 2,3 As a result of its uniaxial symmetry, the crystal exhibits two extreme values of refractive index and refracts incoming randomly polarized light into two slightly separated rays-a property called birefringence.…”

Section: Introductionmentioning

confidence: 99%

Refractive index of infrared-transparent polycrystalline alumina

et al. 2017

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Abstract. The refractive index of fully dense, infrared-transparent polycrystalline alumina (PCA) with a mean grain size of ∼0.6 μm is reported for the wavelength range 0.85 to 5.0 μm over the temperature range T ¼ 296 to 498 K. The temperature-dependent Sellmeier equation is.5533, and the root-mean square deviation from measurements is 0.0002. This paper describes how to predict the refractive index of fully dense isotropic PCA with randomly oriented grains using the ordinary and extraordinary refractive indices (n o and n e ) of sapphire spatially averaged over the surface of a hemisphere. The refractive index of alumina at 296 and 470 K agrees within AE0.0002 with the predicted values. Similarly, the ordinary and extraordinary optical constants k o and k e are used to predict the absorption coefficient of alumina. The refractive indices n o and n e of sapphire grown at Rubicon Technologies by the Kyropoulos method were measured at 295 K and agree with published Sellmeier equations for sapphire grown by other methods within AE0.0002.

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Properties of Sapphire

Cited by 83 publications

References 35 publications

A New Regime of Nanoscale Thermal Transport: Collective Diffusion Counteracts Dissipation Inefficiency

A New Regime of Nanoscale Thermal Transport: Collective Diffusion Counteracts Dissipation Inefficiency

Giant Conductivity Modulation of Aluminum Oxide Using Focused Ion Beam

Refractive index of infrared-transparent polycrystalline alumina

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