Formation of a crystalline phase in amorphous hydrogenated carbon-germanium films by electron beam irradiation

Tyczkowski, J.; Pietrzyk, B.; Mazurczyk, Radoslaw; Polański, K.; Balcerski, J.; Delamar, Michel

doi:10.1063/1.120223

Cited by 10 publications

(7 citation statements)

References 11 publications

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“…Although it was clearly shown that a-S samples were more cross-linked, no rapid changes in the chemical structure between a-S and a-I, contrary to their electronic structure, were also observed . Similarly, investigations performed by the transmission (TEM) and scanning (SEM) electron microscopy as well as by the electron diffraction have not revealed any differences in the supermolecular structure between the a-I and a-S films . A certain confirmation of the a-I−a-S transition, from the supermolecular structure point of view, has been given, however, by the atomic force microscopy (ATM) and unconventional analysis of XPS spectra …”

Section: Introductionmentioning

confidence: 92%

“…3 Similarly, inves- tigations performed by the transmission (TEM) and scanning (SEM) electron microscopy as well as by the electron diffraction have not revealed any differences in the supermolecular structure between the a-I and a-S films. 5 A certain confirmation of the a-I-a-S transition, from the supermolecular structure point of view, has been given, however, by the atomic force microscopy (ATM) and unconventional analysis of XPS spectra. 4 These measurements indicate that a-Ge X C Y :H films have a nonhomogeneous distribution of charge that step changes between the a-I and a-S forms.…”

Section: Introductionmentioning

confidence: 99%

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Transition from Amorphous Semiconductor to Amorphous Insulator in Hydrogenated Carbon−Germanium Films Investigated by Raman Spectroscopy

Kazimierski¹,

Tyczkowski²,

Kozanecki

et al. 2002

Chem. Mater.

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Amorphous hydrogenated carbon-germanium films (a-Ge X C Y :H) were fabricated by plasma chemical vapor deposition in an audio frequency (af) three-electrode reactor using tetramethylgermane (TMGe) as a source compound. Two types of the material, namely semiconducting (a-S) and insulating (a-I) films characterized by quite different electronic properties, were produced. For example, electrical conductivity at room temperature, T room , amounts to approximately 10 -18 S/m (with activation energy E A ≈ 0.9 eV) and 10 -4 S/m (E A ≈ 0.3 eV) for a-I and a-S, respectively. This very drastic change in the electronic structure of the a-Ge X C Y :H films can be caused by a very small variation of the plasma deposition conditions and therefore it is termed a-I-a-S transition. The previous attempts to explain the nature of the a-I-a-S transition from the molecular and supermolecular point of view (quantitative chemical microanalysis, XPS and IR spectrscopies, TEM, SEM, electron diffraction, and AFM) have failed. In this paper Raman spectroscopy has been used to this end. It has been found that the carbon structure does not determine the electronic properties of the films and sp 2 sites are not responsible for the a-I-a-S transition. This conclusion is supported by investigations on a-Ge X C Y :H films, in which sp 2 sites are purposely created. On the other hand, a drastic difference in the Ge atoms dispersion in the a-I and a-S has been found. In the a-I films a great amount of Ge atoms is molecularly dispersed, whereas in the a-S films the vast majority of Ge atoms is in the form of a-Ge several-nanometersized clusters. It is suggested that these clusters play a crucial role in the formation of the amorphous semiconductor network and they are responsible for the a-I-a-S transition.

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Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Transition from Amorphous Semiconductor to Amorphous Insulator in Hydrogenated Carbon−Germanium Films Investigated by Raman Spectroscopy

Kazimierski¹,

Tyczkowski²,

Kozanecki

et al. 2002

Chem. Mater.

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“…The phenomenon of formation of a crystalline phase in amorphous materials upon electron beam irradiation has been already described for hydrogenated carbon−germanium films produced by plasma deposition in a three-electrode reactor . It has been found that the crystalline phase of these films is composed of pure germanium nanocrystals.…”

Section: Resultsmentioning

confidence: 93%

Hydrogenated Carbon−Lead Films Plasma-Deposited from Tetraethyllead in a Three-Electrode Reactor

1998

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Amorphous hydrogenated carbon-lead films (a-Pb X C Y :H) were produced by plasma chemical vapor deposition (PE CVD) in an audio-frequency (af) three-electrode reactor using tetraethyllead as a source compound. The negative amplitude of af voltage, V (-) , measured on a small electrode, on which the films were deposited, with respect to the ground was the only operational parameter of the deposition process. V (-) was changed in the range of 0-1150 V. Investigations on electrical and optical properties, chemical structure, and morphology of the films were carried out. It has been found that a change in V (-) of about 100 V brings about rapid changes in the electrical conductivity (from 10 -14 to 10 -4 S/m), its activation energy (from 0.5 eV to the nonactivated process), and the optical gap (from about 3.0 to 1.3 eV). On the other hand, any drastic changes have not been observed in the chemical structure. This effect has been attributed to the amorphous insulator-amorphous semiconductor transition. It has been suggested that the transition effect is closely connected with the film cross-linking and Pb-C bonds play an important part in this process. The role of oxygen that is embedded into the film structures during the deposition process and the aging processes proceeding in the films under air treatment have been also discussed.

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“…electrical conductivity at room temperature changes more than 15 orders of magnitude. At the same time no rapid change in chemical constitution is observed [3,7,8]. Detailed analysis performed by means of chemical microanalysis, electron spectroscopies (XPS and Auger) and FTIR spectroscopy revealed that chemical structure is practically unchanged when step change in electronic structure occurs [3,9].…”

Section: Introductionmentioning

confidence: 93%

Mesostructured thin films deposited by PECVD from TMGe

Kazimierski

2006

Thin Solid Films

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Formation of a crystalline phase in amorphous hydrogenated carbon-germanium films by electron beam irradiation

Cited by 10 publications

References 11 publications

Transition from Amorphous Semiconductor to Amorphous Insulator in Hydrogenated Carbon−Germanium Films Investigated by Raman Spectroscopy

Transition from Amorphous Semiconductor to Amorphous Insulator in Hydrogenated Carbon−Germanium Films Investigated by Raman Spectroscopy

Hydrogenated Carbon−Lead Films Plasma-Deposited from Tetraethyllead in a Three-Electrode Reactor

Mesostructured thin films deposited by PECVD from TMGe

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