Carbon films, diamond-like electronics

Q.F. Huang, S.F. Yoon, Rush, Q. Zhang and J. Ahn, Dielectric Properties of Molybdenum-containing Diamond-like Carbon Films Deposited Using Electron Cyclotron Resonance Chemical Vapor Deposition, Thin Solid Films, 409, 211-219 (2002). 

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. 

Diamond-like carbon since its inception in 1962 has found applications in some very important areas. These applications include coatings used in scratch-resistant optics, razor blades, prosthesis in medical applications electron emission surfaces in electronics as an insulator material for copper heat sinks in semiconductors such as solar cells and sensors for visible to infrared radiations and as structural materials such as deuterated DLC film used for neutron storage in advanced research instrumentation. As technology matures the unique properties of DLC will find new and important applications. 

Figure 11.20 shows the influence of electron beam irradiation with =100keV in a transmission electron microscope on thin film structure during 2 s of deposition. As can be seen in Figure 11.20 the electron irradiation of the film results in its amorphization, as the main maximum at d= 0.435 nm attributing to the linear chain structure disappears the film structure transforms into diamond-like carbon. This means that the electron beam excitation of carbon atoms leads to cross-linkages among carbon chains and, as a result, the transformation of sp bonds into sp" and sp" bonds takes place. 

Strelnitskii et al. 32) reported a superdense carbon allotrope (4,100 kg-m ) obtained as carbon films formed by radio-frequency condensation of carbon plasmas on cooled substrates the crystalline phase, obtained along with amorphous phase, was studied by electron diffraction and revealed a primitive rhombohedral unit cell with 8 carbon atoms, hence this phase was called Cs, and its structure, as proposed by Stankevich et al. [33] and Biswas et al. [34], involved cubes connected by single bonds (supercubane). Burdett and Lee [9] found the supercubane structure to be less stable than diamond if the constituting atoms have 4 or less electrons per atom, but more stable for electron-rich systems (i. e. >4 electrons per atom). Johnston and Hoffmann [35], observing discrepancies in the crystallographic analysis and the unusual bond length distribution, found that a likely alternative structure for Cs is the body-centered BC-8 structure adopted by the high-pressure y- Si allotrope. 

Even though the existence of C3P4 was postulated together with C3N4 as early as in 1984 , no research has been done on carbon phosphide besides a recent work on phosphorus-doped diamond-like carbon films. The present study is therefore expected to provide basic information on the structure and properties of carbon phosphide. It is of interest to know whether C3P4 can form a stable alloy. And if it does, what is the possible structure What physical properties does it have The ultimate aim is to produce a stable form of carbon phosphide having potentially useful electronic properties. 

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