Proceedings of the 12th Workshop on Quantum Solar Energy Conversion - (QUANTSOL 2000)
March 11-18, 2000, Wolkenstein, Südtirol, Italy

Photoelectrochemical Study of Electrochemically-Deposited Diamond-Like Carbon Films

A.I. Kokorin*, E.V. Shevchenko#, D.V. Sviridov&, D.I. Kochubey**, A.I. Kulak#

* Institute of Chemical Physics, Russian Academy of Sciences
Kosygin st. 4, 117977 Moscow B-334, Russia

#Institute of General and Inorganic Chemistry, National Belarusian Academy of Sciences,
Surganov st. 9, Minsk 220072, Belarus

&Institute of Physico-Chemical Problems, Belarusian State University,
Leningradskaya st., 14, Minsk 220050, Belarus

** Institute of Catalysis SB RAS
Novosibirsk, Russia

Considerable recent attention has been focused on the diamond-like carbon (DLC) films which offer promise as an electrodic material for various electrochemical [1-3] and photoelectrochemical [4,5] applications owing to high chemical ineptness, pronounced photoactivity and the possibility of controlling electric conductivity. In these studies, the DLC films prepared via hot filament-assisted chemical vapor deposition [1,2,5] and microwave plasma-assisted deposition [3,4], as a rule, are used. The potentialities of several other deposition techniques including pulsed-laser evaporation [6], laser-induced arc [7], and mass-selected ion beam deposition [8] have also been demonstrated.

In this work, the possibility of electrochemical deposition of photoelectrochemically-active DLC films was demonstrated for the first time. For this purpose, the anodic oxidation of lithium acetylide Li-Cº CH at the conductive support (F-doped SnO2, Pt film at heavily-doped silicon, Ni, glassy carbon) was employed. The deposition has been carried out from 0.1 M Li-Cº CH + 0.01 M Bu4NClO4/dimethyl sulphoxide solution under potentiostatic or galvanostatic conditions. The photoelectrochemical studies were performed in the 0.2 M CH3COONa aqueous buffered solution (pH 4.4) using 120 W medium-pressure Hg lamp as a light source.

It is seen from Fig.1 that in presence of Li-Cº CH a drastic increase of anodic current is observed at Pt, Ni, and degenerated SnO2 electrodes against the background currents, the deposition of transparent carbon film being observed both in the potential range corresponding to the peak in the potentiodynamic polarization curve and at high biases. AES profiling evidences that carbon deposition at nickel electrode biased at 0.0 ¸ +0.3 V occurs with the rate of ca. 0.2 nm/min. By contrast to Pt, Ni, and SnO2 electrodes, the carbon deposition at glassy carbon occurs much more effective yielding, however, black porous graphite-like layers.

The transparent carbon films at the degenerate SnO2 demonstrate a pronounced photoactivity (Fig.1c) exhibiting the photoresponse of n-type in contact with aqueous solution. The photocurrent onset potential is of -0.4 ¸ -0.3 vs. Ag/AgCl electrode.

The XPS spectra (Fig. 2) evidence that Li-Cº CH oxidation yields DLS film which is almost completely free from sp2 carbon bonding typical for graphite (with the binding energy of C 1s electron equal to 284.1 eV); only small amount of sulphur originating from dimethyl sulphoxide used as an aprotic mediasolution is also detected in the XPS and AES spectra. Alongside with sp3 hybridized carbon which manifests itself as higher binding energy peak at 285.4 eV the presence of carbon bonding with oxygen is observed as a high-energy shoulder which is, in fact, a superposition of at least two signals arising from different oxidized carbon spices. The fact that the energy difference between the most positive and most negative excursions of C KLL derivative spectrum (Fig. 3), ca. 14 eV for electrochemiclly-grown carbon film, is close to that typical for diamond (13.4-14.5 eV [9]), being thus considerably lower then that for graphite (22.8 eV) also implies the presence of predominately sp3 hybridized carbon atoms in our case.

The electrochemical deposition of conductive DLC films opens possibilities for novel photoelectrodic and photovoltaic systems.

Figure 1 Anodic polarization curves (2 mV/s) for DLC deposition at (a) nickel and platinum electrode; (b) at degenerated SnO2. ( c) Current vs. potential dependencies for DLC film grown under galvanostatic conditions (400 m A cm-2, 30 min)

Figure 2 C 1s X-ray photoelectron spectrum for the carbon film electrochemically grown at Pt/Si electrode under galvanostatic conditions (400 m A cm-2, 30 min)

Figure 3 Auger electron spectrum for different carbon samples.

References

  1. N. Katsuki, E. Takahashi, M. Toyoda, et al. J. Electrochem. Soc. 145 (1998) 2358.
  2. L.-F. Li, D.A. Totir, N. Vinokur, et al. J. Electrochem. Soc. 145 (1998) L85.
  3. T. Yano, D.A. Tryk, K. Hashimoto and A. Fujishima. J. Electrochem. Soc. 145 (1998) 1870.
  4. A. Sakharova, Yu. Pleskov, F. Di Quarto, et al. Electrokhimiya 32 (1996) 1298.
  5. A. Modestov, Yu. Pleskov, V. Varnin, I.Termezkaya. Electrokhimiya 33 (1997) 60.
  6. W. Kautek, S. Pentzien, A. Conradi, et al. Appl. Surf. Sci. 106 (1966) 158-165.
  7. C. Collins, F. Davanloo, D. Jander et al. J. Appl. Phys. 69 (1991) 7862.
  8. J.H. Freeman, W. Temple, G.A. Gard. Vacuum 34 (1984) 305.
  9. J.C. Lascovich, R. Giorgi, S. Scaglione. Appl. Surf. Sci. 47 (1991) 17.

[List of Contributions]

E-mails: kokorin@chph.ras.ru, kulak@igic.bas-net.by, elchem@fhp.bsu.unibel.by, kochubey@catalysis.nsk.su

Last updated April 25, 2000