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Participant

Join Date: Sep 2008
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Cleaving mica methods

09/19/2008 12:05 PM
Does anyone hava any advice for freshly cleaving mica?

I know you can use a razor blade but there is an increase chance i will damage the freshly cleaved surface and because im looking at protein fibers 5nm wide i want the mica to be as flat and not damaged by my cleaving procedure.

1. I have heard you can use sticky tape to cleave mica but what tape would be best to use?

2. Do both sides of the mica have to be fixed to an object with the sticky tape to cleave best?

3. And when cleaving do you have to pull the objects that each side of the mica is attached to at an angle or do you pull it away as parallel as you can?

Im new to Atomic Force microscopy but understand that the quality of my prepared sample will affect my image data and quality visualising the fibers.

Thanks

Danny

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#1

Re: Cleaving mica methods

09/19/2008 3:36 PM

The razor blade will do you just fine, or similar tool depending on the size of the sheet.

No way you are going to get a glass smooth surface on a cleave separation anyway.

My Grandpa used to cleave them for the furnace work he did. Mica is not a finished surface, but a collection of scales of mineral fused together in layers.

I Dun-Know, you can do the microscopic stuff with it after you have it in layers.

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#2

Re: Cleaving mica methods

09/19/2008 7:29 PM

Can it be cleaved with compressed gas, or purified air?

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#3

Re: Cleaving mica methods

09/20/2008 1:11 PM

Hi,

cleaving with a razor blade is a first good trial,

cleaving with a freshly broken glass is much sharper and thus better but will require some bending and compressing forces to give a very thin blade at one side,

cleaving with a diamond knife (surgical one, 20 to 30° blade angle, 300$) is best.

All this is prone to scratch the freshly cleaved surface and may be damage the cutting edge.

Cleaving with pressure sensitive tape will not give good results unless you make a starting notch with one of the above knives.

Cleaving with attached tapes will give best results if both faces are pulled apart and the rear pulled back, so to let the two faces being pulled apart enclose a very small angle only.

I assume that very thin pressure sensitive tape is better than thick ones.

3M has samples down to 20µm thickness (used for electrical insulation).

I don't think you need a very tough tape as mica is very easy to cleave.

I would try also to start cleaving by a knife and then add some water or cleave under water.

Have success and please report here what you tried.

If you need only very thin flakes of limited size it may be worth to do an ion exchange of the mica's sodium atoms to ammonium, then grind with a colloid mill, then separate the flakes and last step reverse the ion exchange.

RHABE

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Anonymous Poster
#4
In reply to #3

Re: Cleaving mica methods

09/21/2008 4:14 PM

Hi

Thanks for all your fast replies the mica disks i have brought are designed for AFM and are the highest grade muscovite mica and freshly cleaving the mica is enough to allow the protein to bind. i will have an experiment with some of the methods discussed and will report back with which appears most successful

Thanks

Danny

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#5

Re: Cleaving mica methods

09/22/2008 6:07 AM

We've used 40µm thick mica washers which, as far as I know, were all hand cleaved.

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Participant

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#6

Re: Cleaving mica methods

09/22/2008 6:49 AM

The mica disks i have are ~250um thick and i have tried very thin double sided sticky tape on the some steel disks and attached these disks to the mica.

Allowed them to stick for a while just to make sure I cleave 1 complete layer. Then pull the two steel disks apart at a slight angle to cleave the mica.

This appears to be fine for cleavage without the need for a blade to knotch the edge. But I need to see if it is as smooth a surface as i need for my experiment.

Cheers

Danny

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#7

Re: Cleaving mica methods

09/22/2008 4:20 PM

dxb used double sided sticky tape, I would suggest a vacuum plate in place of the sticky tape. One plate on each side of the mica sheet, engage the vacuum and pull slowly.

A little touch with a scapel point might be necessary to initiate seperation. But it should be a clean, flat surface.

Now the only question is "how much do you want to pay to build the fixture?"

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Anonymous Poster
#8

Re: Cleaving mica methods

10/03/2008 5:20 AM

All the proposed methods above will function......it all depends on how smooth a surface one wishes to achieve......atomically smooth areas as large as 1cm2 on both sides have been readily obtained......the source and history of the mica sample is a major factor.......i am a materials engineer, back in 2003 I obtained samples from all over India.....the best stuff i found came from a mob called Electromica, (not to say it can't be matched by other sources).......as mica is a natural product, all samples are unique, so trial and trial(as opposed to error).....

A big factor effecting the quality of the cleave is how the samples are cut..........lathe cut substrates will almost always surpass those that have been die cut......though atomic layer cleave can be achieved in any instance.....

"the best way to cleave mica"

  • Never cleave in air, always place mica in water to reduce the splitting force ("the best" liquid is a hydrogen peroxide solution just above freezing, i can't remember the ratio but it is the point where the dielectric constant is at a maximum)
  • Use the sharpest point you can find (an electrolytically sharpened tungsten needle is "the best")
  • Never force the cleave, apply negligible pressure to begin with and let the water naturally penetrate the cleavage plane
  • be patient,(once the cleave has initiated proceed at about 0.5mm per second, any faster and the chances of multiple cleavage layers is increased...there are no major benefits or risks in going any slower)
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