Low temperature specific heats of permanently densified glassy GeO<sub>2</sub>

Carini, G.; Carini, G.; D’Angelo, Giovanna; Tripodo, G.; Orsingher, L.; Fontana, A.

doi:10.1080/14786435.2010.530617

Cited by 7 publications

(3 citation statements)

References 28 publications

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“…The heterogeneity scenario comes from the correlation between mass density and the density of TLSs observed here and in the specific heat study [14]. Similar mass density dependence of TLSs has also been found in a-As x Se 1−x [30] and in compacted a-SiO 2 [31,32]. It is known that a-Si cannot be made more dense than c-Si, and a larger mass density deficit (∼10%) has been linked to the formation of voidlike structures [33].…”

supporting

confidence: 82%

Hydrogen-Free Amorphous Silicon with No Tunneling States

et al. 2014

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The ubiquitous low-energy excitations, known as two-level tunneling systems (TLSs), are one of the universal phenomena of amorphous solids. Low temperature elastic measurements show that e-beam amorphous silicon (a-Si) contains a variable density of TLSs which diminishes as the growth temperature reaches 400 °C. Structural analyses show that these a-Si films become denser and more structurally ordered. We conclude that the enhanced surface energetics at a high growth temperature improved the amorphous structural network of e-beam a-Si and removed TLSs. This work obviates the role hydrogen was previously thought to play in removing TLSs in the hydrogenated form of a-Si and suggests it is possible to prepare "perfect" amorphous solids with "crystal-like" properties for applications.

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confidence: 82%

Hydrogen-Free Amorphous Silicon with No Tunneling States

et al. 2014

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“…In this section we give a brief overview of the methods used to prepare the permanently densified samples and to perform the heat capacity measurements. A more detailed description of the experiments can be found in previously published manuscripts [25,31,33].…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Here, we present a detailed analysis of the specific heat of vitreous germanium oxide (v-GeO2) at various densities [22,31], that we compare to those of the corresponding hexagonal crystal [32]. The aim of this work is to review the already published experimental data [22,31] and clarify the effect induced by density changes on the thermal properties of glasses.…”

Section: Introductionmentioning

confidence: 99%

New insights on the specific heat of glasses

Baldi

Carini

Chumakov

et al. 2016

Philosophical Magazine

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The physical properties of disordered systems are in the focus of a large research effort. In particular, one of the open problems related to glasses is their excess of modes in the THz frequency range over the vibrational contribution predicted by the Debye model. In fact, one could expect the continuum approximation underlying the Debye model to hold in glasses at long wavelengths at least as well as in crystalline solids. Experiments, instead, seem to indicate that the specific heat at low temperature (a few Kelvin) and the density of vibrational states at low frequency (a few terahertz) are very different from the Debye prediction. We present here a detailed analysis of specific heat measurements of vitreous GeO2, a prototype of strong glasses, and of permanently densified vitreous GeO2. Our data give experimental evidence that glasses do not show any excess of vibrational modes when compared to their crystalline counterparts of similar mass density.

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