SEM od CD's

8-6-98

I know this has been covered in the distant past, but I never wrote it

down. We have an open house coming up and I would like to have a

micrograph from a CD for show and tell. Could someone tell me the

sample prep steps to do this? I've never done it before.

-Scott Walck

Scott D. Walck, Ph.D.

PPG Industries, Inc.

Guys Run Rd. (packages)

P.O. Box 11472 (letters)

Pittsburgh, PA 15238-0472

Walck@PPG.com

(412) 820-8651 (office)

(412) 820-8161 (fax)

We did something like this years ago. I can't put my hand directly on the

records for the moment, but I think it went like this. The problem was

that the dimples are not at the top of the CD, but buried inside with a

metallic layer to reflect. As memory serves me, what we did was to cut

out a small area of the CD, and then bed it shiny side down on some rapid

cure Araldite. After this hardened, one could then flick off the piece of

CD, leaving the shiny layer on the Araldite, and the dimples appeared as

troughs in the surface that was exposed. This was then sputter coated

with gold in the usual way, and examined under SEM with the direction of

the grooves or dimple at the "magic angle" (put in flat, rotate so the

the grooves run at 45^ to x and y, and then tilt z by 54^. I think one

could also look at the remaining metallized area on the Aralidite, again

gold coating.

There may be inaccuracies after such a long time of recall, but I think

this will give you a general principle to work on.

Good hunting!

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Hi Scott,

I took a damaged writable cd and cut a wedge out,

plastic and all. The foil peels off easily. I

then mounted it on a stub with double sided carbon

tab.

The long line is called an "atip". This is

the tract the lases follows. Then there are

"lands" and "pits". These are the spaces(lands)

between the laser burns(pits). Hope this helps.

Greg R

greg@umic.sunysb.edu

Dear Scott,

I did this years ago, and as I recall, I cut a one centimeter square from

the CD, put it in tri-chorethane overnight to dissolve the plastic, then

fished out the very thin Al foil that was released and put it on a shiny

graphite stub. It wrinkles horribly and the little grooves are hard to see

until you reach 10,000X mag, but it is possible. This is for ressed CD's,

the CD-R's you make yourself are completely different.

Mary Mager

mager@interchg.ubc.ca

Scott-

previously I produced SEM samples of CD's to evaluate the etching or

burning from the laser involved in the writing process.

simple steps (as long as you understand the CD will be destroyed) immerse

the CD in liquid nitrogen (other cryo-liquids will probably work also) for

approx. 30-60 sec. You will hear it start to crack. Remove the CD with

tongs, slap it down onto a hard surface (lab bench, desk) or strike it

while lying on the hard surface with a hammer. The plastic/metal interface

will sheer, leaving a conductive metal to examine under the SEM.

I usually used carbon sticky tabs to mount, no sputtering was necessary.

Good Luck

-Mike

MIKE ROCK

merock@du.edu

Hi,

I have a request for a micrograph of the pits and lands on a music CD. I

thought this would be fun and simple but we aren't having any luck imaging

anything (actually it was so reflective we imaged the detector!:-)

Here's what we've done:

We cut up a CD - using a piece of it close to the center hole (so we knew

it had something on it to see). The piece was mounted (lower surface up) on

a stub using a carbon sticky tab and silver paste. The sample was sputter

coated for 2 minutes (some for 3) and scoped. The first time we viewed it

we didn't coat it (see paragraph one for details).

Do we need a solvent to munch awhile on the surface layer of the CD?

Any help would be greatly appreciated!

It was a Christmas music CD so maybe that is the problem :-).

beth

**************************************

Beth Richardson

EM Lab Coordinator

Botany Department

University of Georgia

Athens, GA 30602

Phone - (706) 542-1790

FAX - (706) 542-1805

Email - beth@dogwood.botany.uga.edu

Beth

I have done this in the past using a rewritable CD where the

reflective coating can be readily stripped using tape. Using a normal

CD I think we had to physically rip it apart, ( I seem to remember it

was quite tough ), a good source for this is the freebies that you

find on computer mags.

John

John Findlay

Science Faculty EM Facility.

Edinburgh University.

Daniel Rutherford Bldg.

Kings Buildings.

Edinburgh EH9 3JH.

tel. 0131-650-5344

fax. 0131-650-6563

John.Findlay@ed.ac.uk

Greetings,

The pits and lands on a CD are <<inside>> the plastic of the CD, so you

need to dissolve it with some sort of solvent (I believe I used

methanol,

but can't recall for sure). The correct organic solvent will make the

plastic

disappear entirely, not just craze it and turn it cloudy. I think there

may

be several types of plastic used as the base, because I used toluene a

number

of years ago the first time I tried this, and it didn't work on the CD I

used a few

months ago. Anyway, use a couple of fresh changes until the foil is

floating free,

then mount it on a stub and take a look. You might need to mount both

sides of a single

piece so that you are sure you have the side with the pits. If you've

gotten all the plastic

off, you might get away without coating, but I coated mine anyway.

You can see an example of the pits and lands at

http://www.mta.ca/~jehrman/cd.htm

BTW, the CD I used is a Microsoft(TM) Office demo CD, so any flaws

are Bill Gate's fault, not mine!

Cheers,

Jim

James M. Ehrman

Digital Microscopy Facility

Mount Allison University

Sackville, NB E4L 1G7

CANADA

phone: 506-364-2519

fax: 506-364-2505

email: jehrman@mta.ca

There was a thread about CDs recently which might be helpful. In a

mass produced CD the pits are in the aluminum layer which is under

a plastic layer. Electron imaging won't stand a chance unles the

plastic is removed. BTW... CD-Rs are quite different - use a dye

rather than Al film.

Woody

McDermott Technology

me: http://www.geocities.com/capecanaveral/3722

Please pardon the commercials!

Beth,

What are the lateral and Z dimensions of these structures? There have been a number of other techniques,including SWLI (Scanning White Light Interferometry) used to image these structures. I have access to a system which can do that, if it would be helpful.

Best regards,

Barbara Foster

mme@map.com

Protocol for preparation of CDs for SEM analysis (by Mike Rock)

This simple method utilizes the coefficient of thermal expansion for

separation of materials of differing densities. CDs are made up of a

metallic core (usually aluminum or gold) surrounded by a plastic layer on

either side. Other methods include dissolving the plastic with various

solvents, or by removing the metal layer by etching techniques. Both may

work fine, I have tried neither. This protocol uses liquid nitrogen to

cool the sample (CD) to a point where the materials separate, and has

proved successful with both gold and aluminum CDs.

Using tongues immerse the CD in the liquid nitrogen, after 15-30 seconds

the CD will sound as if it is cracking. After 30- 60 seconds remove the

CD from the liquid nitrogen.

Place the frozen CD on a firm surface and strike it with a hammer (wear

safety glasses), the CD will shatter. Alternatively you may wish to slap

the frozen CD down against the bench top (results of the two techniques

are similar), shearing between the plastic and metal interface. The metal

will easily pull away from the surface of the plastic if still in contact.

Mount the metallic layer, which contains the information tracks ("pits"

and "lands") on a aluminum stub using double stick "conductive" carbon

tape or tabs. Sputter coating is usually not necessary. Examination with

the SEM is fairly routine at this point (5-15 kV).

MIKE ROCK

merock@du.edu

Greetings,

The pits and lands on a CD are <<inside>> the plastic of the CD, so you

need to dissolve it with some sort of solvent (I believe I used

methanol,

but can't recall for sure). The correct organic solvent will make the

plastic

disappear entirely, not just craze it and turn it cloudy. I think there

may

be several types of plastic used as the base, because I used toluene a

number

of years ago the first time I tried this, and it didn't work on the CD I

used a few months ago. Anyway, use a couple of fresh changes until the

foil is

floating free, then mount it on a stub and take a look. You might need

to mount both

sides of a single piece so that you are sure you have the side with the

pits. If you've

gotten all the plastic off, you might get away without coating, but I

coated mine anyway.

You can see an example of the pits and lands at

http://www.mta.ca/~jehrman/cd.htm

BTW, the CD I used is a Microsoft(TM) Office demo CD, so any flaws

are Bill Gate's fault, not mine!

Cheers,

Jim

James M. Ehrman

Digital Microscopy Facility

Mount Allison University

Sackville, NB E4L 1G7

CANADA

phone: 506-364-2519

fax: 506-364-2505

email: jehrman@mta.ca

The simplest way that was suggested by Brian McIntyre and what worked

fine was to simply scratch the back surface with a knife and take some

good scotch tape and press on the back over the scratch with the tape.

When it has been pressed onto the back with a lot of pressure, simply

peel it off. You'll see the pattern transferred to the tape. Since

this layer is conductive, there is no need to coat it as long as you

have a good conductive path from that surface to the support stub. You

can use carbon paint.

If you have the conductive carbon double sticky pads, they work well

also.