Single-particle tunneling spectroscopy and superconducting gaps in the layered iron-based superconductor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi mathvariant="normal">KCa</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mi mathvariant="normal">Fe</mml:mi></mml:mrow><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mi mathvariant="normal">As</mml:mi></mml:mrow><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mi …

We perform scanning tunneling microscopy/spectroscopy study on the layered iron based superconductor KCa$_2$Fe$_4$As$_4$F$_2$ with a critical temperature of about 33.5 K. Two types terminated surfaces are generally observed after cleaving samples in vacuum. On one commonly obtained surface, we observe full gap feature energy values close to 4.6 meV. This type spectrum shows clean and uniform space, which indicates absence nodes this superconductor. Quasiparticle interference patterns have also been measured, show no scattering between hole tiny electron pockets, but rather an intra-band pattern is possibly due hole-like $\alpha$ pocket. The Fermi band only $24\pm6$ meV as derived from dispersion result. Meanwhile, impurity induced bound-state peaks can be at $\pm2.2$ some spectra, peak value seems independent magnetic field. second surface rarely obtained, fully gapped still although multiple gaps either single or separate ones, determined coherence locate mainly range 4 8 Our results clearly indicate nodeless superconducting nature KCa$_2$Fe$_4$As$_4$F$_2$, superfluid contributed by near $\Gamma$ point. would inspire further consideration effect shallow incipient bands M point, help understand pairing mechanism highly iron-based