Figure 4. Termination and stoichiometry determination for SrTiO₃ thin films.

(a–d) AFM morphology of 20 nm homoepitaxial SrTiO₃ thin films grown with a laser fluence of 1.05, 1.44, 1.62 and 2.25 J·cm⁻², respectively. Step terraces are of unit cell height (≈4 Å). Inset: Line profiles extracted from the RHEED pattern after growth. For each case, only the specular spot and 1^st order diffracted electrons are detected (each peak is labeled exemplary in (d)). (e) Measured cation ratios (data points) as a function of the photoemission angle and fits (solid lines) according to equation (7).