A. Synthetic single crystal diamond is a manufactured product for industrial applications, produced by high pressure / high temperature (HPHT) synthesis process and tightly controlled crystal growth conditions. Repeatable physical characteristics and dimensional consistency are the notable features of synthetic single crystal diamond.

Q. What is the atomic structure of Synthetic Single Crystal Diamond?

A. Synthetic single crystal diamond has an identical physical structure to that of natural single crystal diamond. The basic diamond atomic structure, described by its unit cell can be pictured as a face-centred cube (as shown below) with a carbon atom in the middle of each face and four more atoms arranged diagonally opposite each other in pairs, with the upper plane offset at a right angle to the lower plane.

Atomic Structure of Syntethic Single Crystal Diamond

Key to diagram

Unlike graphite, the individual planes are not flat but corrugated. In diamond, each carbon atom is connected to four other carbon atoms by covalent bonds. In the simplest case, these four atoms form a perfect tetrahedron. Due to covalent bonding between the atoms there are no free electrons and synthetic diamond is normally not electrically conducting. In the case for synthetic diamond, one or more of the carbon atoms might be replaced (or substituted) with nitrogen atoms, giving the diamond a yellow colour.

Q. Why is Synthetic Single Crystal Diamond Yellow?

A. Nearly all synthetic single crystal diamond is Type Ib diamond, which is characterised by its optical absorption spectrum and contains nitrogen in a dispersed substitutional form (where a carbon atom has been replaced by a nitrogen atom) in small amounts, typically about 0.01%.

Picture of Syntethic Single Crystal Diamonds

A selection of synthetic single crystal diamond plates

The effect of this form and quantity of nitrogen atoms is to introduce absorption bands in the visible wavelength spectrum which give this diamond a yellow colour when viewed under white light Natural single crystal diamond exists in a variety of colours - including yellow - some of which are dominated by the inclusion of atomic nitrogen, but many where the colour is an inherent aspect of the diamond's beauty, its origin unknown - even after careful scientific examination.

CVD (Chemical Vapour Deposition)

Q. What is CVD?

A. CVD is an abbreviation for Chemical Vapour Deposition which is a crystal growth process used not only for diamond but also for a range of different semiconductor and other crystalline materials such as silicon or gallium arsenide. The technique generally involves the growth of a solid material from the gas phase using a reactive gas mixture which supplies the necessary active species (carbon in the case of diamond) onto a controlled surface (or substrate).

CVD Process

In contrast to high pressure/high temperature (HPHT) synthesis, the CVD technique is generally performed at below atmospheric pressure. Because CVD can use very high purity reagents the technique is capable of synthesising crystals in which the purity is closely controlled.

Picture of CVD Diamonds

Development of CVD technology over the last decade has led to the formulation of a range of new diamond materials with properties optimised for specific applications. These include high purity CVD diamond for optical or electronic applications as well as CVD diamond grades suitable for thermal and machanical use.

Q. Is CVD diamond as tough as PCD?

A. Albeit a tough material with a fracture toughness comparable with many ceramics, polycrystalline CVD diamond has no binder phase and consequently has a fracture toughness 5.3 - 7.0 MPam1/2 (compared with silicon nitride of 6 MPam1/2) whereas typical PCD has a fracture toughness of 8.81 MPam1/2. For simple comparison, the fracture toughness of ISO K10 tungsten carbide is 10.48 MPam1/2.

CVD Diamond Samples

Q. What is CVD diamond?

A. In most respects, CVD diamond exhitbits the extreme chemical and physical properties of natural and high pressure / high temperature (HP/HT) synthetic diamond: It is essentially pure carbon with no binder phase. However, formed as intergrown diamond microcrystallites, CVD diamond is a truly polycrystalline material with a grain structure and rather than a fixed growth habit it has a degree of orientation or "texture". As is the case with many materials grown with thin-film technology, the grains in this CVD diamond grow from small nuclei which intergrow as they become larger and the layer becomes thicker giving it a columnar structure.

A scanning Electron Microscope picture of the cross-section of a 2.3mm thick optical grade CVD diamond layer

A scanning Electron Microscope picture of the cross-section of a 2.3mm thick optical grade CVD diamond layer

CVD diamond is chemically inert, has outstanding thermal conductivity and excellent abrasion resistance. Depending on the synthesis process used, CVD diamond can be engineered to give a range of diamond materials which enable new technologies and new opportunities for research and industry.

Q. What does CVD diamond look like?

A. CVD diamond is synthesised as plates of material, perhaps as large as 140mm in diameter and as thick as 2mm! This "as-synthesised" (or "as-grown") material is not generally suitable for use in its raw form and requires shaping and finishing. Consequently, most commercially available CVD diamond has been processed in some way or another to give it the right size and surface for the application it is intended for. For example, CVD diamond used for laser windows is highly polished on both sides to optical component tolerances.

A scanning Electron Microscope picture of the as grown surface of a CVD diamond layer

A scanning Electron Microscope picture of the as grown surface of a CVD diamond layer

In its as-grown state, when removed from the deposition apparatus, CVD diamond has two surfaces of importance: the growth surface, which is characterised by a faceted structure of well-intergrown diamond crystals ranging in size up to hundreds of microns across (dependent on the grade of CVD diamond produced) and a nucleation surface composed of very fine-grained diamond crystals, perhaps even sub-micron in size (also dependent on the grade of CVD diamond produced).

Q. Is CVD diamond as hard as natural or synthetic single crystal diamond?

A. Both natural and synthetic single crystal diamond have measured hardness values which are dependent on the crystal orientation of the face measured using indentation hardness techniques. This typically ranges from 57GPa (for the (100) surface) to 104GPa (for the (111) surface) in Knoop hardness value.

Hardness testing CVD Diamond

CVD diamond (which is polycrystalline) has no single crystal orientation and consequently no orientation dependence of its bulk hardness which has been measured as 81Ã??Ã?Â±18GPa.

Regiatration FAQ

Q. How to choose a secure password?

A. Passwords should be at least 10 characters long and only include the letters A-Z, a-z, and the numbers 0-9. Passwords are case sensitive.

To ensure your password is secure you should:

Mix upper and lowercase letters and numbers in your password.
Ensure you do not use your name, your company name, CVD, e6, your date of birth, the current year or other common words as part of your password, there are easier to guess.

A good strategy is to pick a phrase that you will remember and use the first letters from that phrase, for example:

Phrase: "The best holiday I ever had was in San Sebastian"
First letters: "TbhIehwiSS"
Replace some letters with numbers: "TbhI3hw1SS"

Note: Remember most passwords are not "cracked" by anonymous "hackers", but usually discovered by reading the post-it stuck to your monitor, the note in your diary, the passwords.doc file on your hard drive or the entry in your mobile phone phonebook. So, pick a password you can remember and don't need to write down.

Q. What is the Element Six Customer Number?

If you are an existing Element Six customer you will have an Element Six Customer Number. This should be on the top of your invoices. If you have an Element Six Customer Number we will already have your details in our order fulfilment system. Including your Element Six Customer Number will help us fulfil your order more efficiently and you will receive your goods sooner.

Q. What is the Verification Text?

A. The distorted verification text image you see on the registration form is a security test that prevents malicious computer programs from registering false accounts on our website. Current computer programs cannot read the distorted verification text but humans usually can.

If you are having problems reading the text, simply click the "Try another" button to get a new verification text.

This kind of test that tries to tell the difference between computers and humans is called a "Turing Test". This particular test called a "CAPTCHA". This is an acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart".