deposition process allows its employ in a wide range of applications. Numbers ... of the plasma, and these in turn have a wide use in the industrial area as cutting tools, ... On the other hand, arc plasma processes for carbon-based grown are.
Carbon-Based Coatings Production By Arc Plasma A. Devia C1, P. Arango1, J. Botero1, M. Arroyave1, E. Restrepo1, L. Garcia1, A. Pulzara1, Y. Arango1, W. Ramirez1, W. Rivera2, P. Prieto3 Laboratorio de Fisica del Plasma Universidad National de Colombia Sede Manizales Universidad del Cauca Universidad del Valle labrjlaun(ci)mamzales. cetcol. net, co
Abstract. Carbon-based coatings were produced by arc plasma for physical vapor deposition starting from HOPG (High Oriented Pyrolitic Graphite) target. The coatings were deposited on substrates of silicon (100) and (110) a temperature of 46°C. XRD spectra and AFM images were taken on samples, further the plasma was characterized by OES. The low temperature of deposition process allows its employ in a wide range of applications. Numbers PACS: 52. 75.Rx
INTRODUCTION The processes assisted by plasma are of wide use in the technology of surfaces and the engineering of materials; they are diverse the techniques that are being employees to give functional properties to current materials according to the application type. The carbon-based hard coatings is one of the many examples of technological applications of the plasma, and these in turn have a wide use in the industrial area as cutting tools, forming tools. In this applications high wear resistance, corrosion barriers, thermal properties and low coefficient of friction is required. The materials used for these coatings can be classified according to their characteristics of chemical bonding and this in particular as ceramic covalent (nitrides, carbides and borides as: IF, B, diamond, BN, SiC, etc.) [1]. On the other hand, arc plasma processes for carbon-based grown are most suitable for applications a low temperature and high rate deposition. In this paper it is presented the partially results of production and characterization of carbon-based coatings by arc plasma evaporation.
CP563, Plasma Physics: IX Latin American Workshop, edited by H. Chuaqui and M. Favre ©2001 American Institute of Physics l-56396-999-8/01/$18.00 73
EXPERIMENTAL DETAILS The carbon-based films were deposited onto polished silicon substrates (110), and (100). The deposition system is a non-commercial reactor which consist of a RLC circuit (C=54mF, L=2.3mH, R=0.54Q) connected between two plain electrodes located inside a vacuum chamber. The vacuum arc discharge is generated by capacitor bank by spark ignition with an additional trigger circuit. The chamber is pumped up to 5x10~5 milibar and after is filled with hydrogen/argon mixture up to 5.0 milibar, since with only hydrogen it is more difficulty the arc ignition. A previous argon glow discharge was realized for target cleaner of high oriented pirolytic graphite (HOPG) at 2.0 milibar of pressure for five minutes, so a heating effect of substrate is produced. The figure 1 shows a depicted of system. The sample was characterized in composition by XRD (x-ray Diffraction), further it is taken AFM images on surface of samples for study morphology characteristics. During the discharge it is obtained optical emission spectra for knowing the species that are involved in the coating formation. osciloscope
ground
ground
FIGURE 1. Diagram of PAPVD system for coating production.
DISCUSSIONS Figure 2 shows an AFM image of large area scanning of carbon-based coatings. Some broken films flakes have been thrown off from the surface. Usually, buckling would not spread over the whole surface but start from edges of the specimen. The sinusoidal shape of the buckling pattern would be more obvious, as see. The same problems have been reported for DLC production by pulsed laser deposition (Wei 1999) [5].
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FIGURE 2. AFM images obtained on coating samples (34 x 34 jim2 scanning area)
AFM image of large area scanning (20 x 20 urn2) of figure 3 shown a relatively soft surface with some particles that rising around 120A, in this case the carbon-based films stick well to the substrate and no buckling was observed. Other image, with area scanning of 5 x 5 jam2, (figure 4) is more clear the presence of particles in peak shape that seem diamond structure in according was reported by Shima (1999) [2].
FIGURE 3 AFM images obtained on coating samples (20 x 20 fim2 scanning area)
FIGURE 4. AFM images obtained on coating samples ( 5 x 5 |am2 scanning area)
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The shape and position of the three mains peaks that appear in x-rays spectra, indicates the existence of different crystalline structures. The first of these three peak corresponds to crystalline graphite orientation (002), the second peak is characteristic of the silicon substrate for an orientation (111), and the third peak is of diamond (111). The peak in 44.860 is next to the value reported for the diamond (111) for K. Edamatsu(1991)[3].
16000 14000 12000 ^ 10000 13
I |
Ar
6000
0) •
2000
390
400
410
420
430
440
450
460
Wavelenght (nm) FIGURE 5. Spectrum of plasma using to obtained carbon based coatings
The figure 5 shows typical optical emission spectrum for the process. The species detected by this technique in a pulsed discharge using argon and nitrogen gas to fill the chamber and a target of HOPGH were summarized in table 1. The species found here are similar as those reported by other authors [4]. We could see many lines of atomic and molecular carbon, and also it was possible to find hydrogen atomic (Ha, Hp, and Hy) and molecular lines. Furthermore, it can note that carbon and hydrogen are mixed to obtain CH and CH+. TABLE 1. Species In Arc Plasma.
Species CH CH+ H2 C2 H C
Band System
Balmer (a,p,y) 396.58 nm, 404.67 nm
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Some of possible reactions that occur at the discharge process as the literature shows are: C++H2-»CH++H C+H2-»CH +H H+C2-»CH+C
CONCLUSIONS The measures of X rays of the samples of carbon-based coating by arc plasma PVD starting from a target of HOPG reveals the existence of a diamond phase (111). Further a typical structure of coating surface it's seem with reports previous of AFM images and micrograph optical for diamond structure. This can be the first report of production of carbon-based coatings with diamond phase for the technique arc plasma PVD starting from HOPG.
ACKNOWLEDGMENTS The authors thanks COLCIENCIAS and Universidad Nacional de Colombia by support this work.
REFERENCES Rodrigo A. Plasma processing materials. Second Latino American plasma processing materials course. Argentina. Aug 1999. Shima R. et al. Journal of Vacuum science Technology. 1912-1918 (Sep/Oct 1999). K. Edamatsu, et al. Japanese Journal of Applied Physics. Vol. 30, No. 5, 1073-1083 (1991). K. Teii. Journal of Vacuum Science Technology. 138-143.(Jan/Feb 1999). Q. Wei. Journal of Vacuum Science Technology. 3406-3414 (Nov/Dec 1999)
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