Figure 1: Establishing the orientation relationship of the topotactic transformation.
From: High-quality EuO thin films the easy way via topotactic transformation
(a) θ–2θ-scans of a single-phase (401)-oriented Eu2O3 film (sample 1) and a single-phase (001)-oriented EuO film capped with titanium (sample 2) grown on (110) YAlO3. Thickness fringes are present around the EuO 002 peak. Substrate peaks are marked by asterisks. (b) φ-scans of the YAlO3 101 and the monoclinic Eu2O3 310 families of peaks. These scans demonstrate the epitactic growth of the Eu2O3 film with in-plane orientation relationship 
(scan parameters: 
; 
; 
; 
). (c) φ-scans of the YAlO3 101 and the EuO 111 families of peaks. The four EuO peaks demonstrate the topotactic conversion of Eu2O3 into an untwinned (001)-oriented EuO film on the (110) YAlO3 substrate with in-plane orientation relationships 
(scan parameters: 2θEuO=30.08°; ψEuO=52.50°; 
; 
). (d) Rocking curves of the YAlO3 220 peak and the Eu2O3 401 peak, measured on sample 1, respectively. The FWHM of the film peak is comparable to that of the substrate peak, indicating the excellent crystalline quality. (e) Rocking curves of the YAlO3 220 peak and the EuO 002 peak, measured on sample 2, respectively. The FWHM of the film peak is only slightly larger than that of the film peak of sample 1.
