please read

https://www.materials-talks.com/blog/2020/05/14/basics-to-powder-x-ray-diffraction-how-to-achieve-high-quality-xrd-patterns-qa/

Dear Zachary Neale ,

I havn't made such an experiment.

But for a sufficiently thin epoxy layer (some µm) you will see certainly quartz XRD peaks.

But from the x-ray optics point of view, you should consider two aspects:

a) how strong does the strain relaxes within the quartz as a function of sample depth? I assume that the strain will only affect some superficial atomic layers*) (or lattice constants), but I may be wrong;

and

b) the information depth within the quartz is some**) µm, which is far from a 'few atomic layers'. So you will not only 'see' the surface or superficial regions but also a very lot of the bulk quartz.

So, if the induced strain profile only affects the outermost atomic layers in the superficial region of your quartz, you will not see any significant XRD peak-shift or -broadening.

For more 'surface sensitivity' you have to go for grazing incidence XRD (GIXRD).

However in your case you will a) suffer from increased attenuation due to the epoxy layer and b) the information depth will only go to the low µm regime, which is still far from 'some atomic layers'.

When going extremely down to the angular regime close to the critical angle of total reflection you will have penetration/information depths of around the 20 to 30nm regime; but you will here stick onto the epoxy surface and not on the quartz one.

So far my thoughts yet....

*) Please consider that the stiffness of epoxy is much lower than that of quartz; but I have not done stress/strain profiles distribution calculations yet. Furthermore due to the 'creepy' properties of epoxy, I assume that most of the upcoming stress at the boundary is already removed in the epoxy layer itself in a quite short time interval by creeping.

**) The x-ray mass-attenuation coefficient (µ/rho) of quartz at 8keV is about 36,4g/cm², which for a density of 2,65g/cm³ will give a linear x-ay attenuation coefficient of µ~100/cm. Bearing in mind that the mean XRD information depth is given by 1/(2µ)*sin(theta), one will end up with about 25µm at theta~30° (2theta~60°). Please note that this 'information depth' in quartz is independent on the thickness of the expoy layer on top; the epoxy can be regarded as an x-ray filter, which modifies the x-ray intensity. You may retrieve the mass-attenuation coefficient by yourself from: https://physics.nist.gov/PhysRefData/Xcom/html/xcom1.html

Dear Gerhard Martens ,

Thank you for your thoughtful considerations. Your explanation of x-ray mass-attenuation is very helpful. This has given me a better understanding of this problem.

Thank you,

Zachary