Supplementary Information

Figure S1. X-ray diffraction (XRD) patterns of Sr3SnO films prepared with different passivation methods; Figure S2. Original Sr/Sn ratio data mapped across the Sr3SnO compositional spread film; Figure S3. Temperature-dependent resistance of a Sr3SnO thin film and home-built kit used for the resistance measurement; Figure S4. Calculated vapor pressure of Sr as the function of temperature and Sr/Sn ratios mapped across the Sr3SnO compositional spreads grown at different temperatures; Figure S5. XRD patterns of Sr3SnO samples fabricated from the selected positions (P1 - P5) on Si substrates at 800 {degree sign}C; Figure S6. Ternary phase diagram of Sr-Sn-O obtained from Materials project