Question

what is a single crystal...? is it possible to make crystal with one particular crystallographic plane..???

Answer 1

Single crystal means that whole part has been grownout from a single nuclei... thus leading to no grain boundries...... and in single crystal, all planes will have one direction..... same plane for example [111] in a crystal will have same directions..... this is what i got from your question and tried to answer relatively

Answer 2

So in a single crystal there will be only one plane....? or can have different plane as in powder sample...?

Answer 3

yes plane orientation will be same for single crystal.... we can think of powder as crystals having different plane orientation.

Answer 4

But can we manipulate which plane we want..? Say I want to prepare a crystal with (111) plane...is that possible..?

Answer 5

In a single crystal, you still have all the different crystal planes present, but you have to rotate the crystal to access all the planes. In a powder, because you have a (ideally for diffraction) random average orientation of the little crystals, you can observe all the crystal planes without changing the sample position because the smaller crystallites are already arranged in all possible orientations. For a single crystal, every family of crystal planes shares the same orientation, so if it isn't at an angle to the diffractometer to give diffraction, that peak won't show up in a diffraction pattern unless you change the angle of the crystal itself relative to the diffractometer.

As to your other question, usually the way you've specified preparing a single crystal represents which crystal plane was grown parallel to the surface. For example, 100 Si will cut into squares because the surface is the 100 plane. The 111 plane still exists, but instead cuts across the diagonal of the silicon instead of being parallel to the surface. You can also grow 111 Si, and in this case it will now cut into triangles. Again, the 100 plain still exists, it just isn't parallel to the surface now.

Answer 6

@ cheideman ...Thank you very much for the reply...really good explanations...helped me a lot...Thanks...