In-plane observations of RF-sputtered LiNbO₃ thin films using an energy dispersive total-reflection x-ray diffractometer

'In-plane' structures of RF-magnetron sputtered LiNbO₃ thin films grown on Pt(111)/SiO₂/Si and α-Al₂O₃(001) substrates have been observed using a newly developed energy dispersive total-reflection X-ray diffractometer (ED-TXRD). Clear diffractions from both the LiNbO₃ thin films and substrates, with low background level, could be obtained using the ED-TXRD. Hence, it was possible to precisely determine orientations and in-plane lattice spacings within the epitaxially grown thin films. In the case of α-Al₂O₃(001) single crystalline substrates, the rocking curves for in-plane orientation of the grown LiNbO₃ film could be analyzed with high angular resolution. Moreover, it was found that the lattice spacings (d-spacings) of the LiNbO₃ films grown on the Pt(111)/SiO₂/Si substrates were slightly larger than those of LiNbO₃ bulk crystals. From the measurement results using both the ED-TXRD and surface profilometry, the occurrence of residual stresses and lattice defects in the films and substrates were discussed.