Influence of process gas and deposition energy on the atomic and electronic structure of diamond-like (a-C:H) films

Ugolini, D.; Eitle, J.; Oelhafen, P.

doi:10.1016/0042-207x(90)93961-h

Cited by 27 publications

(10 citation statements)

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“…The peak positions are compatible with the idea that the peak around 284.7 eV is due to amorphous hydrogenated carbon and the one at 281.5 eV to crystalline TiC reference spectra for amorphous hydrogenated carbon yield a C 1s binding energy of (284.7Ϯ0.1) eV. 14 For single crystalline TiC x with 0.86рxр0.97 Johansson et al have found a constant C 1s binding energy of (281.40Ϯ0.05) eV. 24 With increasing titanium content the peak that we attribute to the a-C:H is not only decreasing and finally vanishing, but also shifts by about 0.3 eV towards lower binding energies.…”

Section: Resultssupporting

confidence: 73%

“…However, the C 1s binding energy does not depend just on the concentration ratio of sp 3 to sp 2 coordinated carbon. Ugolini et al 14 have deposited a-C:H films by means of direct ion-beam deposition over a large range of deposition energies. From valence-band spectra it is concluded that depending on the deposition energy the concentration ratio of sp 3 to sp 2 coordinated carbon varies significantly.…”

Section: Discussionmentioning

confidence: 99%

“…[14][15][16] In this range the accumulation of a positive charge is hindered by the injection of photoelectrons from the conducting substrate into the insulating film since the penetration depth of the incident light is much larger than the escape depth of the photoelectrons. For titaniumcontaining amorphous hydrogenated carbon films (a-C:H/Ti) the same problem occurs for samples with a low metal content.…”

Section: Methodsmentioning

confidence: 99%

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In situphotoelectron spectroscopy of titanium-containing amorphous hydrogenated carbon films

1999

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Titanium-containing amorphous hydrogenated carbon films (a-C:H/Ti) have been deposited by a mediumfrequency-driven physical vapor deposition plasma-enhanced chemical-vapor deposition process at 40 kHz. Core-level photoelectron spectroscopy and valence-band photoelectron spectroscopy have served as means for the characterization of these films. The spectroscopic data are interpreted by a structural model on the basis of a nanocomposite containing titanium carbide clusters embedded in an amorphous hydrogenated carbon matrix. Within this model parallel energy shifts in the measured positions of the Ti 2p core levels and of the Fermi edge can be explained by a one-electron charging effect of nanometer-sized TiC clusters due to the photoemission process. ͓S0163-1829͑99͒04947-4͔

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Section: Resultssupporting

confidence: 73%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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In situphotoelectron spectroscopy of titanium-containing amorphous hydrogenated carbon films

1999

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“…The amorphous hydrogenated carbon films (a-C:H) were prepared by direct ion beam deposition using either a Penning or a Kaufman ion source [11,12]. Methane was used as a source gas.…”

Section: Methodsmentioning

confidence: 99%

Electron spectroscopy measurements on hydrogen implanted graphite and comparison to amorphous hydrogenated carbon films (a-C:H)

1992

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Abstract.Highly oriented pyrolytic graphite (HOPG) as well as polycrystalline graphite (pcgraphite) were bombarded with 3.5keV H + ions by means of a Penning ion source. The implanted graphite was characterized by in situ electron spectroscopy techniques such as UPS, XPS and EELS. Our UPS valence band measurements of the hydrogen saturated graphite reveal it to be an insulating phase, and XPS measurements show a shift of the Cls core level to higher binding energy with respect to pristine graphite. This behavior is explained by a Fermi energy shift upon hydrogen bombardment of graphite. In addition, a close resemblance in the electronic structure of hydrogen bombarded graphite and amorphous hydrogenated carbon films (a-C :H) is shown which suggests the modification of pristine graphite to an amorphous network [1] of mostly tetrahedrally bonded carbon atoms by hydrogen implantation. 79.20-m, 79.60-i, 73.60-n Graphite is an interesting material in the field of plasma fusion research because of its outstanding physical properties as a first wall material for limiters in fusion reactors (Tokamak) [2][3][4][5]. In particular, one requires a low-Zmaterial with a low vapor pressure. Graphite meets these specifications. PACS:During a tokamak discharge, the first wall interacts with the plasma and is bombarded by hydrogen species which leads to a considerable modification of the surface. Due to the immobility of the implanted hydrogen ions at room temperature, an upper limit of the hydrogen content nn/nc --0.45 is fou/ad in the near-surface region

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“…The general shape of the spectra recorded for short deposition times is very similar to the ones observed for various forms of amorphous carbon. [19][20][21][22] The appearance of two overlapping and rather broad peaks is attributable to the excitation of photoelectrons from the pand p-bands, respectively. These bands are formed by p electrons which participate in chemical bonds of either or symmetry and dominate the UPS spectra on account of their larger excitation cross section as compared to the lower-lying bands with predominantly s character.…”

Section: Resultsmentioning

confidence: 99%

Photoelectron spectroscopic investigation of the bias-enhanced nucleation of polycrystalline diamond films

Reinke

Oelhafen

1997

Phys. Rev. B

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In the present work we describe an investigation of the nucleation mechanism of polycrystalline diamond films if the bias-enhanced-nucleation ͑BEN͒ method is used. Photoelectron spectroscopy with excitation energies in the ultraviolet ͓ultraviolet photoelectron spectroscopy ͑UPS͔͒ and x-ray regime ͑x-ray photoelectron spectroscopy͒ as well as electron energy loss spectroscopy are employed to monitor the nucleation process and the subsequent diamond film growth. The deposition is performed in situ, thus avoiding surface contamination with oxygen or hydrocarbons. The observation of the temporal evolution of composition and structure of the deposited film and its interface with the underlying silicon substrate allow us to develop a qualitative model, which describes the nucleation process. The BEN pretreatment leads, through the irradiation with low-energy ions, to the codeposition of an amorphous carbon phase and the crystalline diamond phase. The presence of both phases is readily apparent in the UPS analysis, which will prove to be an indispensible tool in the structural characterization of the carbon phase present at the surface. There is no indication for the presence of graphite or large graphitic clusters. A deconvolution of the C 1s and Si 2p core-level peaks does confirm the presence of two carbon phases and the formation of a silicon carbide interface. With increasing deposition time the contribution of diamond to the carbon film increases and upon switching to diamond growth conditions the amorphous carbon phase is rapidly etched and only the diamond crystals remain and continue to grow. This removal of the amorphous phase leads to a decrease in the overall carbon concentration at the surface by 18-30 % during the first 30 sec of the diamond growth period and was observed for a variety of pretreatment conditions. A silicon carbide interfacial layer is formed early on during the BEN pretreatment and its thickness is reduced considerably by etching during the diamond growth period. These results are summarized and discussed in the framework of a qualitative model for the nucleation process.

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Influence of process gas and deposition energy on the atomic and electronic structure of diamond-like (a-C:H) films

Cited by 27 publications

References 4 publications

In situphotoelectron spectroscopy of titanium-containing amorphous hydrogenated carbon films

In situphotoelectron spectroscopy of titanium-containing amorphous hydrogenated carbon films

Electron spectroscopy measurements on hydrogen implanted graphite and comparison to amorphous hydrogenated carbon films (a-C:H)

Photoelectron spectroscopic investigation of the bias-enhanced nucleation of polycrystalline diamond films

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