FeSe films are of great interest owing to their rich physical properties and good application prospects. Here, we successfully grew a 40-unit-cell-thick high-$T_{\mathrm{c}}$ FeSe/STO films (onset superconducting transition temperature $T_{\mathrm{c}}^{\mathrm{onset}}\sim 28.3\mathrm{K},$ zero-resistance transition temperature $T_{c0}\sim 23\mathrm{K}$) using a custom-designed pulsed laser deposition–scanning tunneling microscopy (PLD-STM) system. Using in situ STM, large-area terraced surfaces and high atomic resolution of FeSe thin films were observed, marking layered FeSe growth via PLD. Hall and magnetoresistance measurements showed minimal changes in carrier concentration compared to $\mathrm{FeSe}/\mathrm{Ca}{\mathrm{F}}_2$ films with $T_{\mathrm{c}}$ of 8 K, and the Berezinskii-Kosterlitz-Thouless transition analysis indicated the presence of the two-dimensional nature of superconductivity. By angle-resolved photoemission spectroscopy experiment, a band with a large effective electron mass was discovered, which is similar to other high-$T_{\mathrm{c}}$ FeSe systems obtained through alkali-metal doping, etc, suggesting that enhanced electron correlations are crucial for the $T_{\mathrm{c}}$ increase in this system. This work provides guidance for the growth of high-quality superconducting thin films, and provides valuable insight into the mechanisms driving superconductivity in FeSe-based systems.

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• Superconductivity
• 2-dimensional systems
• High-temperature superconductors
• Multilayer thin films
• Angle-resolved photoemission spectroscopy
• Resistivity measurements