Electrical conduction in amorphous carbon films

Morgan, M.

doi:10.1016/0040-6090(71)90049-6

Cited by 116 publications

(40 citation statements)

References 18 publications

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“…The electrical conductivity of amorphous carbon (up to 10 6 S m À 1 ) is multiple orders of magnitude higher than that of silicon carbide (down to 10 À 4 S m À 1 under a nitrogen atmosphere) or voids [35,36]. Hence, the deposition of silicon dioxide and the removal of carbon via reaction 5 should result in a sharp decline in the conductivity of the fibers.…”

Section: Thermal Treatmentmentioning

confidence: 99%

Highly permeable and mechanically robust silicon carbide hollow fiber membranes

Wit

Kappert

Lohaus

et al. 2015

Journal of Membrane Science

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a b s t r a c tSilicon carbide (SiC) membranes have shown large potential for applications in water treatment. Being able to make these membranes in a hollow fiber geometry allows for higher surface-to-volume ratios. In this study, we present a thermal treatment procedure that is tuned to produce porous silicon carbide hollow fiber membranes with sufficient mechanical strength. Thermal treatments up to 1500 1C in either nitrogen or argon resulted in relatively strong fibers, that were still contaminated with residual carbon from the polymer binder. After treatment at a higher temperature of 1790 1C, the mechanical strength had decreased as a result of carbon removal, but after treatments at even higher temperature of 2075 1C the SiC-particles sinter together, resulting in fibers with mechanical strengths of 30-40 MPa and exceptionally high water permeabilities of 50,000 L m À 2 h À 1 bar À 1 . Combined with the unique chemical and thermal resistance of silicon carbide, these properties make the fibers suitable microfiltration membranes or as a membrane support for application under demanding conditions.

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Section: Thermal Treatmentmentioning

confidence: 99%

Highly permeable and mechanically robust silicon carbide hollow fiber membranes

Wit

Kappert

Lohaus

et al. 2015

Journal of Membrane Science

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“…The scaling exponent S = 2/3 found in a-C 1-x N x :H is not compatible with values expected from most FEC models [25][26][27] including some hopping transport models using a function ϕ(b) of a single reduced field parameter b = (eF/2γ kT) thus corresponding to a value of S = 1 [9,28]. The second puzzling point appearing at high field concerns the effective temperature T eff .…”

mentioning

confidence: 66%

“…-S = 1/2: a (F 1/2 /T) scaling was observed in a-C sandwich devices [25] as expected for the PooleFrenkel mechanism for charge carrier emission from a Coulombic trap [26].…”

Section: Scaling Analysismentioning

confidence: 81%

Scaling analysis of field‐enhanced bandtail hopping transport in amorphous carbon nitride

Godet¹,

Kleider²,

Gudovskikh³

2007

Physica Status Solidi (b)

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International audienceHopping transport within a bandtail distribution of localized electronic states has been investigated in amorphous carbon nitride (a-C1-xNx:H, x = 0.23) as a function of temperature T and electric field F. The conductivity σ follows Mott's law in the ohmic regime, i.e. ln (σohmic) varies linearly with T-1/4, while at higher field, a scaling law, ln (σ /σohmic) = φ [FS /T ] with S = 0.67 (±0.05), is found. Data are fully consistent with a field-enhanced bandtail hopping (FBTH) model in which the effective temperature concept describes the non-equilibrium occupation probability of tail states. A "filling rate" method, considering forward non-activated hopping transitions, is developed to analyze the high field regime of FBTH. For an exponential distribution with disorder energy E0, increasing F shifts the transport energy EDL towards shallower tail states, with a density of states N (EDL) ∼ (F)3 (E0)-4. In this model, FBTH is parametrized using ln σ (T, F) vs T-1/4 plots, which provide field-dependent apparent values of prefactor (ln σ00) and slope (T01/4). As F increases, both parameters strongly decrease. This behavior (observed in a-C1-xNx:H, x = 0.23, for F > 5 × 104 V cm-1) is a signature of band tail hopping transport. Our FBTH model predicts a minimum value equation image of σ00(F), which is indeed observed in a-C1-xNx:H (x = 0.23) for T < 70 K (equation image ≈ 10-6 S cm-1 at Fmin ≈ 3 × 105 V cm-1). Near Fmin, kT *eff = (1/kTeff - 1/E0)-1 is parametrized by kT *eff ∼ Fq. The value of q that best reproduces the experimental results, q = 0.7 ± 0.1, is consistent with the scaling exponent S = 0.67 and with the density of states parameters deduced from the Ohmic regime. Hence, this "filling rate" method applied to FBTH transport appears to be very useful to analyze the apparent prefactor σ00(F) and to derive the effective temperature Teff(T, F) which governs bandtail states occupation and FBTH conductivity

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“…It may be mentioned here that in amorphous materials, non-ohmic behavior has also been explained in terms of high field conduction due to the Poole-Frenkel effect of screened charge intrinsic defects and field induced lowering of energy barriers for the charge-carrier hopping within localized states at the band edges [23][24][25], according to which the current I at a particular voltage V is given by:…”

Section: Resultsmentioning

confidence: 99%