“…[16][17][18] To date, the highest RRRs, (ρ 300 K /ρ 4 K ), reported for thin films are ∼80 for an 80 nm thick SrRuO 3 film and 39 for a 78 nm thick CaRuO 3 film, respectively. 7,73 For comparison, the highest RRRs, (ρ 300 K /ρ 4 K ), reported for single crystals of SrRuO 3 and CaRuO 3 are 162 and 38, respectively. 74,75 In general, the RRRs of perovskite ruthenate thin films have been low, likely due to the presence of ruthenium vacancies and more generally due to a lack of clear guiding principles for the growth of high-quality perovskite ruthenate thin films.…”