Properties of hydrogenated amorphous carbon films and the effects of doping

Jones, D. I.; Stewart, A. D.

doi:10.1080/01418638208224021

Cited by 198 publications

(51 citation statements)

References 13 publications

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“…The N content is seen to increase quite rapidly up to Rϭ1, and then increase more gradually. The data shows that the incorporation ratio is much less than one, presumably because N is less easily ionized than CH 4 . Although the ionization potential of N 2 is 11.1 eV, in order to get N ϩ ions an energy of 14.5 eV is required.…”

Section: A Composition and Growthmentioning

confidence: 96%

“…An encased permanent rare earth magnet ͑Nd-B-Fe͒ is used around the substrates to increase the plasma density. The deposition was carried out at a fixed pressure of 0.1 Torr from a CH 4 , He, and N 2 gas mixture, with flow rates of 5 sccm for CH 4 , 45 sccm for He, and 0-20 sccm for N 2 . The magnetic field and the He increases the ionization of the methane plasma, giving a plasma electron temperature of over 6 eV, which results in a higher deposition rate and a lower bias voltage for a given rf power.…”

Section: Methodsmentioning

confidence: 99%

“…Meyerson and Smith 2 observed that a-C:H could be doped n-and p-type by phosphorus and boron, respectively, in a similar fashion to a-Si:H. They concluded that there was true substitutional doping by observing the thermopower sign reversal expected as the conductivity changed from n-type to p-type. 3 However, the doping effect was weaker than in a-Si:H. Indeed, Jones and Stewart 4 found still lower doping efficiencies and they questioned whether true doping was occurring. Interestingly, they observed that nitrogen was able to increase the conductivity of a-C:H, and this has since been repeated by numerous other groups.…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, they observed that nitrogen was able to increase the conductivity of a-C:H, and this has since been repeated by numerous other groups. [4][5][6][7][8][9][10] However, it has been unclear whether N increased the conductivity by doping-raising the Fermi level towards the conduction band, or by graphitization of the bonding-narrowing the band gap.…”

Section: Introductionmentioning

confidence: 99%

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Nitrogen modification of hydrogenated amorphous carbon films

Silva

Robertson

Amaratunga

et al. 1997

Journal of Applied Physics

342

130

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The effect of nitrogen addition on the structural and electronic properties of hydrogenated amorphous carbon ͑a-C:H͒ films has been characterized in terms of its composition, sp 3 bonding fraction, infrared and Raman spectra, optical band gap, conductivity, and paramagnetic defect. The variation of conductivity with nitrogen content suggests that N acts as a weak donor, with the conductivity first decreasing and then increasing as the Fermi level moves up in the band gap. Compensated behavior is found at about 7 at. % N, for the deposition conditions used here, where a number of properties show extreme behavior. The paramagnetic defect density and the Urbach tailwidth are each found to decrease with increasing N content. It is unusual to find alloy additions decreasing disorder in this manner.

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Section: A Composition and Growthmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Nitrogen modification of hydrogenated amorphous carbon films

Silva

Robertson

Amaratunga

et al. 1997

Journal of Applied Physics

342

130

View full text Add to dashboard Cite

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“…Since then, there has been significant scientific interest in the electrical and optical properties of nitrogenated amorphous carbon films. 4 The synthesis of the superhard compound ␤-C 3 N 4 is another aspect, not discussed in this article, that has motivated research. 5 Amir and Kalish 6 and Schwan et al 7 found that nitrogenation of a-C:H leads to a ''graphitization'' of amorphous hydrogenated carbon when deposited with a standard plasma enhanced chemical vapor deposition ͑PECVD͒ system.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen doping of amorphous carbon thin films

Schwan

Batori

Ulrich

et al. 1998

Journal of Applied Physics

103

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Nitrogenated and hydrogenated amorphous carbon (a-C:H:N) films have been deposited by a plasma beam source using a gas mixture of C2H2, Ar and N2. The Ar/C2H2 ratio is kept constant at a ratio of 3, with the nitrogen flow allowed to vary. Nonnitrogenated films, with Ar/C2H2 ratios of 3 and 6 were also deposited and analyzed before attempting to identify the modifications to the microstructural properties due to nitrogen doping. The nitrogenated and hydrogenated a-C (a-C:H:N) films deposited in this study reveal interesting properties with regard to their optical gap, electrical conductivity, and mobility of the charge carriers. The optical E04 gap passes through a maximum of 2.7 eV as a function of incorporated nitrogen. The electrical conductivity, too, reaches a peak value of 10−3(Ω cm)−1 with increasing optical gap and remains constant for higher N2 flows. The electrical conductivity process is thermally activated with activation energies in the range 0.1–0.3 eV. This is discussed in terms of the mobility of the charge carriers (determined by Hall measurements) and electronic doping. The defect density (measured by electron spin resonance) is found to decrease with increasing nitrogen incorporation. The films have also been characterized by infrared spectroscopy, photo thermal deflection, and Raman spectroscopy. The microstructure of the deposited a-C:H:N films is discussed in terms of the electronic density of states.

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