1 monolayer means how long?

1. Feb 6, 2009

yzou_ua

Always be used in experiments... but when it appears in literature, most authors never tell the exact value of 1 ML (monolayer).

So, what is the value, generally??

2. Feb 7, 2009

ZapperZ

Staff Emeritus
This is not a universal value. It depends on the material and crystal structure of what is being deposited.

Zz.

3. Feb 7, 2009

yzou_ua

So w/o telling from author, we can never know it??

4. Feb 7, 2009

ZapperZ

Staff Emeritus
Unless you know the crystal structure. If the author usually doesn't say, then it's a "common" material that he/she would assume that everyone knows already. This is often the case for, say, high-Tc superconductors or well-known compounds such as Al2O3 or TiN.

Zz.

5. Feb 7, 2009

yzou_ua

Then, let's say a particular example in a paper - "5nm-height 2.5ML InAs quantum dots", what does it mean?
Should the height of QD be equal to "2*lattice constant of InAs (~6Å)" ? Isn't it ??

6. Feb 7, 2009

f95toli

2 monolayers will probably be of that order of magnitude, yes. But the exact value will depend on e.g. the termination of the surface etc.
Also, 2.5ML would mean 2 complette layers and one half-filled layer; meaning the top-most layer does not cover the whole surface. Again, what it looks really like will depend on the materials etc.

Btw, the reason the thickness is given in monolayers is because it is much easier to "count" the number of layers (using RHEED oscillations) during the film growth than it is to actually measure the thickness of the film.

7. Feb 7, 2009

yzou_ua

Thx alot for ur patience & excellent background...
Actually, what i want to do is using my numerical model to simulate the experiment. That's why i need to know the exact length, height, etc.
So, i should use "5 nm" in above example to simulate the QD. Right?