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Meet the Experts cvd
CVD - Chemical Vapour Deposition
Chemical vapour deposition, developed in the mid 1980’s is a process by which incredibly thin films of diamond (a few microns thick) can be generated and deposited on a base. The process involves high temperatures (over 2000°C) and lower pressures than involved in HPHT. Mixtures of hydrogen and hydrocarbon gases are energised with heat or electrical energy in a deposition reactor. The carbon molecules are deposited on a substrate as a thin film of polycrystalline material.
Quality and purity are very high and particular diamond properties can be selected. Boron added to the growth gases, for example, will produce an electrically conducting diamond. When the diamond layer has reached the correct thickness the reactor is shut down and the CVD wafers can be removed. Single crystal diamonds can also be grown, but sizeable gem quality is proving difficult. All CVD diamonds are believed to be Type IIa diamonds as no nitrogen is present.
FOCUS ON THE EXPERT
Anu Manchanda, MSc MSc, GG, DGA, FGA, P J Dip,
FNAG Pearl Graduate (GIA)
Anu Manchanda holds a Masters degree (MSc)
in Geology from India, an FGA, DGA from the School of Jewellery, Birmingham, and the Professional Jewellers’ Diploma (PJ
Dip) with distinction from the National Association of Goldsmiths. She is also a Fellow of the National Association of Goldsmiths (FNAG) and a Pearl Graduate of the Gemological Institute of America. She is recipient of the Christie’s Prize for Gemmology (2004).
This is a trade prize awarded to the best candidate of the year who derives his or her income from activities essentially connected
with the jewellery trade. Anu tutors for the Gemmological Association
of Great Britain’s Correspondence course students for both the Diamond Diploma and Gemmology Diploma courses (DGA and FGA).
As an AnchorCert senior gemmologist Anu is responsible for accuracy and for new initiatives in
the diamond grading and gem testing laboratory.
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