On the reversibility of hydrogen effects on the properties of amorphous silicon carbide

Silva, Cesar R. S. da; Justo, J. F.; Fazzio, A.

doi:10.1016/j.jnoncrysol.2004.02.091

Cited by 4 publications

(2 citation statements)

References 22 publications

(26 reference statements)

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“…124 Even if H were to have an effect on disorder, it is difficult to determine experimentally because the effect is convoluted with the influence of C. Theoretical results are mixed, suggesting both an increase and decrease in disorder as a function of hydrogenation. [125][126][127] We note that the relationship between Urbach energy and band gap is opposite in the cases of a-SiC:H and a-Si:H, where in a-SiC:H, the two are directly correlated, but in a-Si:H, they are inversely correlated.…”

Section: B Electronic and Optical Propertiesmentioning

confidence: 84%

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

Nordell

Karki

Nguyen

et al. 2015

Journal of Applied Physics

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Because of its high electrical resistivity, low dielectric constant (j), high thermal neutron capture cross section, and robust chemical, thermal, and mechanical properties, amorphous hydrogenated boron carbide (a-B x C:H y) has garnered interest as a material for low-j dielectric and solid-state neutron detection applications. Herein, we investigate the relationships between chemical structure (atomic concentration B, C, H, and O), physical/mechanical properties (density, porosity, hardness, and Young's modulus), electronic structure [band gap, Urbach energy (E U), and Tauc parameter (B 1/2)], optical/dielectric properties (frequency-dependent dielectric constant), and electrical transport properties (resistivity and leakage current) through the analysis of a large series of a-B x C:H y thin films grown by plasma-enhanced chemical vapor deposition from ortho-carborane. The resulting films exhibit a wide range of properties including H concentration from 10% to 45%, density from 0.9 to 2.3 g/cm 3 , Young's modulus from 10 to 340 GPa, band gap from 1.7 to 3.8 eV, Urbach energy from 0.1 to 0.7 eV, dielectric constant from 3.1 to 7.6, and electrical resistivity from 10 10 to 10 15 X cm. Hydrogen concentration is found to correlate directly with thin-film density, and both are used to map and explain the other material properties. Hardness and Young's modulus exhibit a direct power law relationship with density above $1.3 g/cm 3 (or below $35% H), below which they plateau, providing evidence for a rigidity percolation threshold. An increase in band gap and decrease in dielectric constant with increasing H concentration are explained by a decrease in network connectivity as well as mass/electron density. An increase in disorder, as measured by the parameters E U and B 1/2 , with increasing H concentration is explained by the release of strain in the network and associated decrease in structural disorder. All of these correlations in a-B x C:H y are found to be very similar to those observed in amorphous hydrogenated silicon (a-Si:H), which suggests parallels between the influence of hydrogenation on their material properties and possible avenues for optimization. Finally, an increase in electrical resistivity with increasing H at <35 at. % H concentration is explained, not by disorder as in a-Si:H, but rather by a lower rate of hopping associated with a lower density of sites, assuming a variable range hopping mechanism interpreted in the framework of percolation theory. V

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Section: B Electronic and Optical Propertiesmentioning

confidence: 84%

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

Nordell

Karki

Nguyen

et al. 2015

Journal of Applied Physics

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“…[12,59] Hydrogen atoms may cause the local energy to fluctuate and interact with atoms in metallic glass. Silva et al [60] investigated the effect of hydrogen on the properties of amorphous silicon carbide with free volume Monte Carlo simulation. The results show that carbon atoms segregate, forming small clusters embedded in an extensive silicon network in the presence of hydrogen, and hydrogenation increases the concentration of microvoids in the structure and reduces its midrange order.…”

Section: E Physical Model Of the Nucleation Of A Hydrogen Blister Inmentioning

confidence: 99%

A Nucleation Mechanism of Hydrogen Blister in Metals and Alloys

Ren

Zhou

Shan

et al. 2007

Metall Mater Trans A

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The nucleation process of hydrogen blister in metals was investigated through experiments and the mechanism was discussed. Small hydrogen blister in charged Ni-P amorphous coating and steel was studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermodynamics and kinetics of hydrogen and vacancies in metals are analyzed. Further, an approach of the nucleation mechanism of hydrogen blister is proposed as follows. Atomic hydrogen can induce superabundant vacancies in metals. The superabundant vacancies and hydrogen aggregate into a hydrogen-vacancy cluster (small cavity). The hydrogen atoms in the hydrogen-vacancy cluster become hydrogen molecules that can stabilize the cluster. And the hydrogen blister nucleates. The pressure in the small cavity increases as the hydrogen atoms enter the cavity. The cluster, that is, the hydrogen blister nucleus, grows through vacancies diffusing into it under the action of cluster-hydrogen binding energy and hydrogen pressure. When the blister nucleus grows to a critical size C cr cracks will initiate from the wall of the cavity due to the internal hydrogen pressure.

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A first principles investigation on hypothetical crystalline phases of silicon oxycarbide

Silva

Justo

Pereyra

et al. 2005

Diamond and Related Materials

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On the reversibility of hydrogen effects on the properties of amorphous silicon carbide

Cited by 4 publications

References 22 publications

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

The influence of hydrogen on the chemical, mechanical, optical/electronic, and electrical transport properties of amorphous hydrogenated boron carbide

A Nucleation Mechanism of Hydrogen Blister in Metals and Alloys

A first principles investigation on hypothetical crystalline phases of silicon oxycarbide

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