DC Plasma CVD

Besides the MPCVD reactors, other CVD reactors are also used for diamond deposition. They are hot filament, DC plasma, radio-frequency (rf) plasma, thermal rf plasma, plasma jet, and combustion CVD reactors. In the following, hot filament and DC plasma CVD reactors will be described, because they have been used for oriented growth of diamond. 

Figure 4.2. Schcmalic diagram of DC plasma CVD reactor with BEN capability [72].

Figure 4.3. Plasma generated by the multiple cathode type DC plasma CVD reactor developed at KIST. The source gas was c = 3%CH4/H2, and P = 100 Torr [73, 74].

Cubic boron nitride (cBN) has a zinc blende-type crystal structure with a lattice constant of 3.615 A, which is very close to that of diamond (3.567 A). The difference is only about 1.3%. According to RHEED measurements with the electron beam parallel to the 111 layer of cBN, a growth of diamond by DC plasma CVD on cBN(lll) [150] using c = 0.5%CH4/H2, T = 900°C, and F=180Torr led to a result that a smooth (111) layer of diamond was epitaxially deposited in such a way that the [110] direction of diamond was parallel to that of cBN. Namely, D 111 //cBN(lll and D[110]//cBN[110]. In the RHEED pattern, however, extra spots were observed, which were presumably due to the twinnings of (111 diamond layers. In the Raman spectra, there were two lines due to cBN at 1054.5 and... 

A more thorough study of diamond growth on cubo-octahedral cBN crystals with diameters of about 500 pm was undertaken by DC plasma CVD in Ref. [153],... 

It was discovered by Sawabe and co-workers [10, 405] by DC plasma CVD that diamond grows heteroepitaxially on Ir(lOO). A single crystal Ir(lOO) film for a substrate was deposited on MgO(lOO) of 10-mm square by electron beam deposition at the substrate temperature of 750 °C, and then annealed in vacuum for 60 min at 950 °C. The Ir film thickness was 500 nm. The setup of the DC plasma CVD reactor that has the third electrode between the anode and the cathode for bias application has been shown in Figure 4.2. 

Based on the DC plasma CVD technique, Sawabe and co-workers [376] were successful in making a free-standing, transparent, 2 mm x 2 mm, 8 pm thick, (lOO)-oriented diamond platelet. A defect study of the film was done using ESR [406], In the latest result, a free-standing, transparent diamond plate of l-inch in diameter has been made by Sawabe s group. 

A.7.1. Microwave plasma CVD reactors A.7.2. Hot filament CVD reactor A.7.3. DC plasma CVD reactor A.8. Crystal growth modes A.9. Carbon materials A. 10. Miscellaneous notations... 

S Koizumi, T Murakami, T Inuzuka. Epitaxial growth of diamond thin films on cubic boron nitride [111] surfaces by dc plasma CVD. Appl Phys Lett 57 563, 1990. 

Formation of a cBN film by the DC plasma CVD method has also been claimed (301). Laser-assisted plasma CVD, in which an excimer laser beam irradiated a growing film, was reported to be effective for growing cBN crystals (302,303). 

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