Describe how CVD diamonds grow and what their layers are composed of.

• A. They are grown layer by layer and consist of growth sectors known as terraces and risers.
• B. They grow in random chunks with no layered structure.
• C. They grow as perfect single crystals without steps.
• D. They form in alternating shells of carbon and hydrogen.

Answer: (A)

CVD diamond growth occurs by adding carbon atoms to the existing crystal surface in a layered, stepwise fashion. As atoms incorporate, the surface develops steps that create flat, wide areas called terraces and the vertical rises between them are known as risers. This layer-by-layer (step-flow) growth is what builds the diamond lattice, with each new layer formed atop the previous one. The layers themselves are carbon atoms arranged in a diamond (sp3) lattice; hydrogen in the gas helps control the surface chemistry and suppress non-diamond carbon, but the layers are not alternating shells of carbon and hydrogen. So describing growth as layer by layer with terraces and risers best captures how CVD diamonds form.