Alkali metal intercalated iron selenide superconductors $A_x{\mathrm{Fe}}_{2-y}{\mathrm{Se}}_2$ exhibit unique properties, such as the coexistence of superconductivity and antiferromagnetism, along with an iron-vacancy-order superstructure. However, due to microscopic phase separation, the relationship between these properties and superconductivity remains elusive. In this study, we have employed high-spatial-resolution magnetic force microscopy $\left(\mathrm{MFM}\right)$, Raman spectroscopy, and scanning electron microscopy–energy dispersive x-ray spectroscopy $\left(\mathrm{SEM}\text{−}\mathrm{EDX}\right)$ to identify and characterize the superconducting phase. Below the superconducting critical temperature $T_{\mathrm{c}}$, the striped regions exhibit a pronounced diamagnetic response, while the surrounding areas remain unaffected, providing direct evidence that the striped regions constitute the superconducting phase. $\mathrm{SEM}\text{−}\mathrm{EDX}$ and high-spatial-resolution Raman scattering results reveal a stoichiometry of ${\mathrm{K}}_{0.57}{\mathrm{Fe}}_{1.89}{\mathrm{Se}}_2$ in the striped regions, with a single Raman peak at $173.3{\mathrm{cm}}^{-1}$. Temperature- and polarization-dependent Raman scattering spectra further show that, at low temperatures, this peak shifts to $201{\mathrm{cm}}^{-1}$ in the $B_{1g}$ channel, while a new peak emerges at $165{\mathrm{cm}}^{-1}$ in the $A_{1g}$ channel. The $\mathrm{Fe}:\mathrm{Se}$ ratio in the stripe phase $(1.89:2)$, along with the number, symmetry, and frequencies of the phonon modes, is consistent with the $\mathrm{FeSe}$ layers. These results indicate that the superconducting phase in the striped regions retains an approximately intact $\mathrm{FeSe}$ layer. Our findings underscore the critical role of the intact $\mathrm{FeSe}$ layer in $\mathrm{FeSe}$-based superconductors and provide new insights into the mechanism of high-$T_{\mathrm{c}}$ superconductivity.

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• Superconductivity
• Iron-based superconductors
• Crystal growth
• Magnetic force microscopy
• Magnetization measurements
• Raman spectroscopy
• Resistivity measurements
• Scanning electron microscopy
• Superconductors
• X-ray diffraction