A novel analysis method for peak broadening due to thin structures in double crystal X-ray diffraction measurements

A new method for analyzing X-ray peak broadening due to thin film structure s on (001) substrates in double crystal X-ray diffraction measurements is p roposed. In the method, two typical features exibited by peak profiles for thin film structures are investigated. Diffrence variable DeltaL is introdu ced as a convenient measure for analyzing the two features. It is theoretic ally derived that peak profiles measured using the new variable become hkl- independent if the thin film structural factors dominate the peak broadenin g. Measurement conditions and geometry are essentially taken into account f or the derivation. Based on the theoretical results, a simple criterion is proposed to judge whether broadening of a relevant peak is due to a thin fi lm structure or not. The method is experimentally demonstrated via applicat ion to X-ray satellite peaks of an InGaAsP/InGaAsP multiquantum-well (MQW) sample, and it is verified that the method works well for the satellite pea ks. The method is essentially applied to the analysis of unknown broad and less intense peaks (background peak), which are observed in the X-ray diffr action profiles of tensile strained InGaAsP/InGaAsP MQW. Our method clarifi ed that the microscopic size effect dominates the profile of the unknown pe ak. It is concluded that the unknown peak is caused by the modulation of th e composition in the tensiled well laver. The observation of the unknown pe ak suggests that the strain field is not uniform in either the growth or th e lateral direction.