Joseph Lai

Enhanced growth of high quality single crystal diamond by microwave plasma assisted chemical vapor deposition at high gas pressures

Single crystals of diamond up to 18 mm in thickness have been grown by microwave plasma assisted chemical vapor deposition at gas pressures of up to 350 torr. Growth rates of up to 165 μm/h at 300 torr at high power density have been achieved. The processes were evaluated by optical emission spectroscopy. The high-quality single-crystal diamond grown at optimized conditions was characterized by UV-visible absorption and photoluminescence spectroscopy. The measurements reveal a direct relationship between residual absorption and nitrogen content in the gas chemistry. Fabrication of high quality single-crystal diamond at higher growth rates should be possible with improved reactor design that allows still higher gas synthesis pressures.

Developments in synthesis, characterization, and application of large, high-quality CVD single crystal diamond

Single crystal diamond synthesis by microwave plasma chemical vapor deposition at rapid growth rate has considerably advanced in the past few years. Developments have been made in growth, optical quality, and mechanical properties. Of the various types of single crystal diamond that can be produced using these techniques, high quality single crystal CVD diamond can be routinely produced, and this material is playing an increasing role in research on materials under extreme conditions. This article highlights recent developments in single crystal CVD diamond synthesis and characterization, as well as various applications in high-pressure materials research.

Composite chemical vapor deposition diamond anvils for high-pressure/high-temperature experiments

Composite diamond anvils have been developed for high-pressure/high-temperature measurements of diamond anvil cells. The anvils are fabricated using single-crystal chemical vapor deposition (CVD) from previously used and/or slightly damaged anvils made of natural or synthetic diamond. These composite anvils can be fabricated to possess optical characteristics at least comparable to conventional diamond anvils, whereas the single-crystal CVD portion is more durable because of its enhanced toughness relative to natural diamond. The viability of such anvils is demonstrated in measurements on hydrogen at megabar pressures and high temperature.

Single-crystal CVD diamonds as small-angle X-ray scattering windows for high-pressure research

Small-angle X-ray scattering (SAXS) was performed on single-crystal chemical vapor deposition (CVD) diamonds with low nitrogen concentrations, which were fabricated by microwave plasma-assisted chemical vapor deposition at high growth rates. High optical quality undoped 500 µm-thick single-crystal CVD diamonds grown without intentional nitrogen addition proved to be excellent as windows on SAXS cells, yielding parasitic scattering no more intense than a 7.5 µm-thick Kapton film. A single-crystal CVD diamond window was successfully used in a high-pressure SAXS cell.

Hot Spot Formation in Microwave Plasma CVD Diamond Synthesis

Plasma-substrate interactions in diamond synthesis via microwave plasma-assisted chemical vapor deposition (CVD) are an important issue in CVD reactor optimization. The hot spot formation observed during single-crystal diamond synthesis in 2.45-GHz cylindrical cavity reactors is examined after long-run deposition.

Development of the microwave plasma CVD technique for rapid growth of large single-crystal diamond

Summary form only given. The method of high growth rate single crystal microwave plasma chemical vapor deposition (CVD) diamond has opened new applications for precision tools, electronics, optics, and consumer gems. Here we provide an overview of techniques developed under a Carnegie Institution program for producing large single crystal CVD diamond (>1 cm thick, 10 carats) at very high growth rates of ~100 m/h. These diamonds exceed the sizes of those of commercially available crystals made by high-pressure/high-temperature (HPHT) methods. The various microwave plasma CVD systems we have used include home-made, window and bell-jar type reactors. In order to achieve higher growth rate, the energetic plasma was produced at higher methane concentration 8-20% CH4/H2, and higher pressure 160-220 torr at various temperature 900-1400degC. Substrates were HPHT synthetic type Ib yellow or single crystal CVD diamonds with {100} faces on all sides. Morphologies and colors of the as-grown CVD diamonds strongly depend on the deposition temperature and pressures at various systems. Using the above conditions, gem-quality CVD diamond can be grown individually and sequentially on the 6 {100} faces of the substrate. The prospects for producing much larger single crystal diamond with next generation reactors will be discussed

Simulation of microwave plasma discharge in 915 MHZ CVD reactor for single crystal diamond deposition

Despite the complexity of deposition processes in microwave plasma-assisted chemical vapor deposition, this technique is still a common choice to produce an excellent quality diamond. Recently, several simulation plasma models have been proposed in order to prescribe the complex deposition process and also to better understand the plasma -microwave energy and plasma - diamond growth surface interactions in the microwave plasma CVD reactors [1–4].