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A method, called the 'MOSAIC'-process, has been developed for producing large-area, single-crystal, diamond plates. It starts by carefully orienting and closely packing a set of diamond seed crystals. This assembly, or mosaic, is then overgrown by chemical vapour deposition (CVD) with a single-crystal diamond layer. The success of the 'MOSAIC'-process was shown for three different CVD techniques, namely the hot filament method (HF-CVD), microwave plasma assisted CVD (MPACVD) and the acetylene-oxygen combustion flame. The largest mosaic structure successfully overgrown -up to now- consists of seven seed crystals and has a surface area slightly in excess of 1 cm{2}. Although several technical problems still have to be solved, there seem to exist no fundamental reasons which could hamper the further enlargement of the surface area.
In order to realize the 'MOSAIC'-process, know-how had to be developed about the diamond synthesis processes. Spatially resolved spectroscopic analyses provide information about the local characteristics of the growth environment. The MPACVD system was studied by optical emission spectroscopy (OES) and laser spectroscopy while the combustion flame was studied by laser induced fluorescence (LIF). The molecular density distributions of different species (H, C2, CH, C2H, OH) and their rotational temperatures (H, H2) have been determined. These results provide essential input data for the optimization and validation of modelling calculations, necessary to unravel the chemistry and dynamics of the dominant precursors, which in-turn are indispensable for the optimization and up-scaling of the deposition processes.
The main objective of the proposed research is to make diamond plates of mono crystalline quality with an area of 1 to 2 cm{2}. The quality of the plates must be high, so that they used for optical components by the optical industry and for substrate by the electronic industry.

Two routes will be followed to reach this goal. The first is to grow an unbroken continuous film of monocrystalline diamond on top of a closely packed ensemble of highly oriented side and surface polished individual mm-sized natural diamond plates. The main effort will be directed into this approach, especially in view a recent successful experiment in the laboratory of one of the participants. The second approach is to grow the diamond layer hetero epitactic on an artificial atomic network created on a removable substrate. this route will be regarded as additional.

The major research tasks to complete this research are:

1. The growth of the initial unbroken film by gentle growth technics.

2. The subsequent thickness growth by a high growth rate process.

Associated research tasks are:

3. Optimization of the gentle growth methods.

4. Further development of the combustion flame growth method in order to achieve uniform thickness growth over large areas. (>1cm²)

If successful this proposal will lead to a new way to produce in an economic way large plates of single crystalline diamonds.This can be considered as a real breakthrough in diamond production.

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PO BOX 9010

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Participants (2)