Preparation diamond-like carbon films

H. Nakazawa, A. Sudoh, M. Suemitsu, K. Yasui, T. ltoh,T. Endoh, Y. Narita, M. Mashita, Mechanical and tribological properties of boron, nitrogen-coincorporated diamond-like carbon films prepared by reactive radio-frequency magnetron sputtering., Diamond and Related Materials, vol. 19, pp. 503-506, 2010. 

Preparation Methods for Diamond-like Carbon Films... 

FlQUre 31 Raman spectra at different self-bias DC voltages showing the shift in the D-line and G-line peak position for films deposited at 7 mtorr [72]. (Reproduced from Diamond and Related Materials, 7, Yoon, S. R, et al., The effects of self-generated DC bias on the characteristics of diamond-like carbon films prepared using ECR-CVD, pp. 1213-1218. Copyright 1998, with permission from Elsevier Science.)... 

Besides the proper diamond flhns obtained by vapor deposition, the same method also allows for the preparation of further, similar materials. These include the so-called a-C H- and a-C-phases that are alternatively termed diamond-like carbon (DLC) films. ... 

As for the first topic, methane and other light hydrocarbon plasmas are of great interest in industrial applications, in particular in the chemical vapor deposition ptrocesses. Amorphous carbon and diamond-like thin films, suitable for mechanical and electronic applications can be prepared using low pressure discharges of hydrocarbon gases. The research in this field is mainly devoted to the understanding of the nature of the film growing mechanism but in spite of intense experimental and theoretical work it is not yet fully understood which species are responsible for the deposition process. 

In Section 2 we showed that the properties of amorphous carbon vary over a wide range. Graphite-like thin films are similar to other carbonaceous materials (glassy carbon, and the like) in their electrode behavior. Redox reactions proceed in a quasi-irreversible regime on these films. In particular, the cathodic reduction of nitrate previously studied on crystalline diamond electrodes (see Section 6.4.2) was performed with amorphous carbon films prepared by UHV laser deposition and comprising both sp2- and sp3-carbon [152], Reduction current density as high as 2 mA cur 2 was reached in neutral or alkaline solutions. The use of such electrodes in microgravimetry is discussed [153]. 

Process of chemical vapor deposition (CVD) is one of the most effective methods for preparation of flat emission cathodes. This method allows to produce different carbon structures on the cathode substrate. Depending on conditions of deposition, derivable carbon surface can be diamond-like films [1], amorphous graphite [2], various carbon constitutions, including carbon nanotubes [3], Investigation results of field emission properties produced cathodes have shown this is a promising technology for production Field Emission Display (FED). 

Diamond films may be polycrystalline or monocrystalline layers. In polycrystalline films, the diameter of particles is either on the range of micrometers, or they measure just a few nanometers across (UNCD). The preparation is mostly achieved by deposition from the gas phase (CVD methods). A variety of gaseous hydrocarbons like methane serve as carbon source. Film formation only occurs in the presence of atomic hydrogen that must be generated in situ, for example, in a plasma, on a hot filament, or in a flame. The deposition takes place on a substrate heated at 800-1200 °C. 

Table 19.1 contains a list of chemicals and their properties that are likely to be found in both urban air and urban surface films. At this point we must consider the situation of a gas-phase chemical in relation to a bulk surface film containing a fraction of organic material, /oo, into which the gas-phase chemical will partition. Afa as discussed in Section 19.2.2, can be approximated by/oc oA- In this case, foe becomes a proportionality constant translating between the sorptive capacity of octanol and the film s sorptive capacity. We retain the use/oc as a proportionality constant, which is consistent with its use to describe organic carbon in other matrices such as soil and vegetation. As seen in Table 19.1, A fa is a highly variable parameter and its numerical value will impact the value of Ka- From Equation 19.2, we see that this resistance-in-series expression combines the individual MTCs. (See Chapter 4, Section 4.4.3 for details on its development.) Thibodeaux and Diamond (in preparation) present an analysis and options for the transport of organic molecules within the film by assuming it is composed of various material compositions. Details on the composition and physical structures of surface films are still uncertain at this time. Three film types were assumed air-filled porous material, water-filled porous material, and an organic matter, gel-like material. Calculations were performed using Equation 19.2 and in all three cases, they indicate that the air-side resistances are greater than those for the film-side except for the volatile chemicals such as benzene.

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