chemical vapor deposition

[coatimundi_org]

Anyone work in CVD?

I'm fascinated by this process. We just learned a very brief bit about this at GIA. (I'm doing the G.G. program)

When will we see cuttable quality CVD enter the market?

Seems like the possibilities are endless when it comes to colored diamonds. How do you think this will effect the value of rare colors like pinks and reds?
How fast can they grow stones using this method?

I'm also interested in the impact CVD will have on computer technology. Will we someday have diamond chips in our home/personal computers?

Do CVD created stones have the same growth patterns as HPHT? With the absence of metallic flux, what type of inclusions might we see in these stones?

 

[John P]

Date: 6/13/2008 7:25:38 PM
Author:coatimundi
Anyone work in CVD?

I'm fascinated by this process. We just learned a very brief bit about this at GIA. (I'm doing the G.G. program)

When will we see cuttable quality CVD enter the market?

Seems like the possibilities are endless when it comes to colored diamonds. How do you think this will effect the value of rare colors like pinks and reds?
How fast can they grow stones using this method?

I'm also interested in the impact CVD will have on computer technology. Will we someday have diamond chips in our home/personal computers?

Do CVD created stones have the same growth patterns as HPHT? With the absence of metallic flux, what type of inclusions might we see in these stones?

Apollo uses the CVD process. They produce near the 0.25-0.50 ct range. Their diamonds can be faceted in any shape but the shape of the rough is shallow.

I attended a fascinating session by Branko Deljanin at the Polygon conclave. He is co-author of a recent book called "Laboratory-Grown Diamonds." I can pass info along from my notes and reading. I have no personal experience beyond my GIA coursework and analysis of some HPHT-grown diamonds in a workshop. I have not seen CVD-grown but I'm anxious to.

From what I understand, with CVD diamonds you can see the diamond grew from only four growth sectors under cross-polarized filters. This can distinguish them from natural and HPHT-grown diamonds. Short wave UV is also useful. Many CVD-grown diamonds show orange fluorescence. Groovy. Unlike natural diamonds the reaction of lab-grown is stronger under SW than LW.

Inclusions: Much less present in CVD and generally SI+. There may be a thin layer on the table or culet which is a remnant of the seed. Carbon-like opaque inclusions and/or microfractures (which look like pinpoints) can also occur. When they do they are always parallel with the direction of growth; table-to-culet or culet-to-table. Sometimes a CVD diamond will have clouds lying in a plane perpendicular to the growth direction. These inclusions are indications of the diamond's origin but they aren't conclusive.

The labs can separate nearly all natural diamonds from others with a DeBeers instrument called DiamondSure. It analyzes the region below 500 nm in the UV/VIS spectra, looking for the 415 nm peak which is present in 95% of all natural diamonds. Any diamond without that peak is either in the 5% natural minority or it's lab-grown. All the non-peak diamonds get referred for further testing. Another instrument called DiamondView incorporates SW UV to reveal MMD growth patterns.

Did your GIA instructors tell you about the "magnet test?" In older lab-grown diamonds (HPHT, not CVD) the metallic inclusions would sometimes be large enough that the diamond could be suspended from a strong magnet. Now you have to scope them to look for metallic inclusions, growth patterns and color zoning.

I defer to the professionals from those companies actually involved in growing diamonds for more current or pertinent input.

 

[coatimundi_org]

Date: 6/13/2008 9:16:33 PM
Author: John Pollard

Apollo uses the CVD process. They produce near the 0.25-0.50 ct range. Their diamonds can be faceted in any shape but the shape of the rough is shallow.


I attended a fascinating session by Branko Deljanin at the Polygon conclave. He is co-author of a recent book called 'Laboratory-Grown Diamonds.' I can pass info along from my notes and reading. I have no personal experience beyond my GIA coursework and analysis of some HPHT-grown diamonds in a workshop. I have not seen CVD-grown but I'm anxious to.


From what I understand, with CVD diamonds you can see the diamond grew from only four growth sectors under cross-polarized filters, which can distinguish them from natural and HPHT-grown. Short wave UV is even more useful. Many CVD-grown diamonds show orange fluorescence. Groovy. Unlike natural diamonds their reaction is also stronger under SW than LW.


Inclusions: Much less present in CVD. They are generally SI+. There may be a thin layer on the table or culet which is a remnant of the seed. Carbon-like opaque inclusions and/or microfractures (which look like pinpoints) can also occur and when they do they're always parallel with the direction of growth - table-to-culet or culet-to-table. Sometimes a CVD diamond will have clouds lying in a plane perpendicular to the growth direction. These inclusions are indications of origin but they aren't conclusive.


The labs can separate nearly all natural diamonds from others with a DeBeers instrument called DiamondSure. It analyzes the region below 500 nm in the UV/VIS spectra, looking for the 415 nm peak which is present in 95% of all natural diamonds. Any diamond without that peak is either in the 5% natural minority or it's lab-grown. All the non-peak diamonds get referred for further testing.


Did your GIA instructors tell you about the 'magnet test?' In older lab-grown diamonds (HPHT, not CVD) the metallic inclusions would sometimes be large enough that the diamond could be suspended from a strong magnet. Now you have to scope them to look for metallic inclusions, growth patterns and color zoning.


I defer to the professionals from those companies actually involved in growing diamonds for more current or pertinent input.

Yah, saw some fun photos of the magnet test, and some cool photos of the metallic flux inclusions. These depress me, though, not because they're synthetic, but because they look cold and lifeless. I'm an inclusion junkie, and I prefer the natural to flux---infinite variety. Today I saw a beautiful included diamond crystal--a wispy thing with transparent trigons just hanging out in the middle of the stone--an otherworldly wonder to behold.

I wonder if CVD stones would have the hourglass growth marks of the HPHT variety.

Orange fluor is cool--I'd love to see that. I believe we'll be viewing some HPHT synthetics next week--so no orange, but yellow and green fluor will be cool to see. Class erupted in a huge debate about these yesterday--synthetics vs. natural. Debates are always fun!

I've only seen photos of CVD fashioned stones--no rough. I can't wait to view some in the future. The ease in which they can add color is brilliant. Want blue? Just spike it with Boron.

Thanks for the response, John!

 

[John P]

Date: 6/13/2008 9:36:18 PM
Author: coatimundi

Want blue? Just spike it with Boron.

You''re welcome - and you just made me thirsty for a margarita with a splash of Blue Curacao. Happy Friday.

 

[coatimundi_org]

Happy Friday to you too!

Off to drink!

 

[Clark McEwen]

I wonder if CVD stones would have the hourglass growth marks of the HPHT variety.


Orange fluor is cool--I''d love to see that. I believe we''ll be viewing some HPHT synthetics next week--so no orange, but yellow and green fluor will be cool to see. Class erupted in a huge debate about these yesterday--synthetics vs. natural. Debates are always fun!


I''ve only seen photos of CVD fashioned stones--no rough. I can''t wait to view some in the future. The ease in which they can add color is brilliant. Want blue? Just spike it with Boron.

Thanks for the response, John![/quote]

I''m posting the side view of a CVD crystal...you can clearly see the seed, the diamond growth and what appears to be some graphite formation.

Cheers,
Clark

 

[Clark McEwen]

Another picture of CVD diamonds at different stages both rough and polished

 

[coatimundi_org]

Thanks so much for posting those photos Clark!

That graphite formation is interesting. Does that happen with HPHT? Graphite forms with a changed (lessened) heat and pressure correct? So, during HPHT and CVD is there a dramatic shift in heat or pressure when the diamond is finished, or is it gradual, and would that be what produces the graphite?

 

[Clark McEwen]

Date: 6/14/2008 3:00:09 PM
Author: coatimundi
Thanks so much for posting those photos Clark!


That graphite formation is interesting. Does that happen with HPHT? Graphite forms with a changed (lessened) heat and pressure correct? So, during HPHT and CVD is there a dramatic shift in heat or pressure when the diamond is finished, or is it gradual, and would that be what produces the graphite?

Hi Coatimudi,

Your assumption with regards to heat and pressure is correct when looking a the HPHT process (any small deviation in these will cause issues) but not so with CVD as the temperature and pressures are not used in the same manner. A microwave is used to convert the carbon laden gas into a vapor and I believe that the process actually occurs in a vacuum.

Cheers,
Clark

 

[coatimundi_org]

Hi Clark,
Thank you for answering my questions.
Will Gemesis use CVD in the future? Is CVD more efficient/cost effective than HPHT?

 

[Clark McEwen]

Date: 6/16/2008 1:11:42 AM
Author: coatimundi
Hi Clark,

Thank you for answering my questions.

Will Gemesis use CVD in the future? Is CVD more efficient/cost effective than HPHT?

Gemesis is in the diamond growth business and will use, develop or acquire whatever technology is available. CVD is different than HPHT...this is primarily due to the shape of the grown crystals (HPHT produces "truncated octahedrons while CVD produces wafers or plates) CVD crystals are currently much more suited for industrial applications (optical windows, electronics or coatings) than it is for gem. This is again due to the size (thickness) and shape of the plates that are produced.

 

[coatimundi_org]

We viewed synthetics in class today. Got to see all the inclusions/growth patterns/color zoning through the microscope. Only saw HPHT(no CVD)--some from Gemesis.

We mainly saw yellows, but did get to see a couple blues. Twas cool! Also got to see a piece of rough. They are easy to identify (through the scope/loupe only) as their inclusions and growth patterns are so unlike natural. They are remarkable!

Great company photos in the other thread, Clark.

 

[Clark McEwen]

Date: 6/16/2008 7:45:04 PM
Author: coatimundi
We viewed synthetics in class today. Got to see all the inclusions/growth patterns/color zoning through the microscope. Only saw HPHT(no CVD)--some from Gemesis.

We mainly saw yellows, but did get to see a couple blues. Twas cool! Also got to see a piece of rough. They are easy to identify (through the scope/loupe only) as their inclusions and growth patterns are so unlike natural. They are remarkable!


Great company photos in the other thread, Clark.

Thanks, they are remarkable (and beautiful) aren''t they...and why a diamond industry vet such as myself decided to join the lab-grown game.

I should caution you with regards to the samples that you saw in class today as these are not typical of what you should expect to see in the market. The current samples used in the course are 1) old 2) rejection quality and 3) used to illustrate certain characteristics that students can readily see without too much trouble.

I am working with the GIA to get some newer and better quality material for them to use along side of the current examples that they have.

Cheers,
Clark

 

[coatimundi_org]

Date: 6/17/2008 2:01:30 PM
Author: Clark McEwen

Date: 6/16/2008 7:45:04 PM

Author: coatimundi

We viewed synthetics in class today. Got to see all the inclusions/growth patterns/color zoning through the microscope. Only saw HPHT(no CVD)--some from Gemesis.

We mainly saw yellows, but did get to see a couple blues. Twas cool! Also got to see a piece of rough. They are easy to identify (through the scope/loupe only) as their inclusions and growth patterns are so unlike natural. They are remarkable!



Great company photos in the other thread, Clark.

Thanks, they are remarkable (and beautiful) aren't they...and why a diamond industry vet such as myself decided to join the lab-grown game.


I should caution you with regards to the samples that you saw in class today as these are not typical of what you should expect to see in the market. The current samples used in the course are 1) old 2) rejection quality and 3) used to illustrate certain characteristics that students can readily see without too much trouble.


I am working with the GIA to get some newer and better quality material for them to use along side of the current examples that they have.


Cheers,

Clark

Thanks! That's good to know. I had a feeling they chose some of the more highly included ones, so we could view a
variety of inclusions--similiar to our laser drilling/fracture filling lab. We saw some pretty crazy examples!

They are beautiful. Diamonds, pure and simple.