Reciprocal Space Maps

Re-use of this resource is governed by a Creative Commons Attribution-
NonCommercial-ShareAlike 4.0 International
https://creativecommons.org/licenses/by-nc-sa/4.0/

Real Space Unit Cells

Film

substrate

Film strained to match substrate

Reciprocal Space Points

In plane lattice
parameters matched

Real Example of (105) Reciprocal Space Maps
AlGaN cell < GaN cell < InGaN cell

Al_xGa_(1-x)N film on GaN In_xGa_(1-x)N film on GaN

x-coordinates unmatched.

x-coordinates matched showing that the film is strained to the substrate

The same data in real space on diffractometer axes.

With the data plotted in real space the crystallographic result is not readily apparent.

(105) RSMs

c out-of-plane and a & b within the plane. GaN is hexagonal 1/S001= c, 1/S100=d100, a= d100 /cos30. The intensities of the contours are plotted on a log scale so the substrate peak is stronger than the film peak.
Al_xGa_(1-x)N film on GaN In_xGa_(1-x)N film on GaN

GaN out of plane has a spacing of ~0.962Å^-1 for 5 cells so c ~ 5/0.962 = 5.2Å.
In-plane the spacing is 0.367Å^-1. a ~ 1/0.367 × cos 30 = 3.19Å.

Note Real cells Al_xGa_(1-x)N < GaN < In_xGa_(1-x)N.