This picture, 15KB

Fig. 3-3 Real-time RHEED (reflection high energy electron diffraction) observation during film growth Pure carbon ions specified with respect to isotopes are deposited onto a Si (111) substrate at the vacuum of 10-7Pa. At the same time the diffraction pattern of the surface deposit is observed using 25 keV electron beam.

Photo 1

(a)		(b)
(c)		(d)

Photo 2

Fig. 3-4 Changes of RHEED-pattern Photo 1 (a) shows the original Si(111)-pattern, (b) after deposited with 1015 12C /cm2 at 10 eV, (c) after deposited with 1016 showing the existence of two phases, Si and SiC, and (d) after deposited with 1017 weak-ring patterns showing polycrystallization (graphitization). Photo 2 shows a pattern consisting of streaks due to diamond structure (lattice constant: 3.6 angstrom) which was obtained after 100 eV12C+deposition at 1018/cm2.

Table 3-1

Characterization of IBD-carbon thin films (RHEED)

Practical synthesis of diamond thin films using the CVD (chemical vapor deposition) technique provides a polycrystalline diamond containing many impurities as the method involves a high temperature process. Meanwhile, it has been expected that the IBD (ion beam deposition) technique can be utilized as a low-pressure and ambient-temperature process to synthesize a crystalline pure diamond thin film. With the IBD technique, experimental conditions are finely controlled because monoenergetic atoms, even isotopes are deposited on a substrate at ultra-high vacuum. Thus we investigated for the first time in the world the film-growing process in real time using RHEED (reflection high energy electron diffraction). As a result, we found out that the deposition energy of incident carbon ions is an important parameter and that the deposition energy of 100 eV is more suitable for making diamond single crystals than 10 eV which is close to the binding energy of the substrate.

Reference H. Ohno and S. Nagai, Synthesis of Single Crystaline Diamond Thin Films, Kogyo Zairyo, 44, 110 (1996).

Select a topic in left column