Effect of substrate temperature on the growth mechanism of FeSe superconducting films

Abstract

Among all the iron-based superconductors (IBSs), Fe-chalcogenides (Fe-Ch) possess the advan tages of simple structure, non-toxicity, low anisotropy and the potential for high-field applications.One of the most effective methods for preparing Fe-Ch films is pulsed laser deposition (PLD). However, high quality film growth is challenged by the significant volatility difference between the iron
and chalcogens (S, Se, Te), which affects stoichiometric transfer from target to substrate and subsequently impacts superconductivity. Currently, there is limited research on the correlation between the growth mechanism and preparation conditions of Fe-Ch films, particularly in explaining chalcogen volatility during deposition. Technically, PLD offers various adjustable parameters, among
which the substrate temperature (Ts) is the most critical one affecting film quality. It governs particle behavior on the substrate including adsorption, diffusion, bonding reactions, crystallization processes while also strongly affecting volatilization rates. In this study, we fabricated a series of FeSe films using PLD at different Ts ranging from 25 ℃ to 750 ℃.We reveal in detail the impact of
competitive processes between Se volatilization and reactive crystallization of Fe/Se on film quality. The optimal film was obtained at Ts=500 ℃ with a composition ratio of Fe1.01Se. We also investigate the correlations between Ts and film crystallinity, surface morphology, along with their influence on superconductivity. Additionally, the pinning mechanism in FeSe film grown at the
optimal Ts was briefly analyzed. Our results provide reliable experimental evidence regarding the growth mechanism of FeSe films while revealing comprehensive insights into how Ts affects both film quality and performance.