The momentum-resolved electronic structure of $\mathrm{Si} \left(111\right)\sqrt{3}\times \sqrt{3}\text{−}\mathrm{Sn}$, a surface Mott insulating system, was verified by in situ angle-resolved photoemission and spectroscopic-imaging scanning tunneling microscopy measurements. All the samples grown on different Si substrates were shown to be metallic at room temperature. However, discrepancies with the density functional theory calculation that do not consider correlation effects were observed, which suggests that there is some effect of correlation even though the Mott transition was reported to occur at 200 K. At 7 K the samples became insulating, but we found that the electron filling of this system can be controlled by repeated annealing of the Si substrate (flashing); the sample grown on a highly $p$-doped substrate became metallic due to hole doping whereas the the sample grown on a highly $n$-doped substrate became more insulating by increasing the number of flashing. The quasiparticle band dispersion with a small bandwidth near the Fermi level was clarified after hole doping and reproduced with tight-binding calculations.

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• Doping effects
• Electronic structure
• Surface states
• Mott insulators
• Angle-resolved photoemission spectroscopy
• Scanning tunneling microscopy
• Scanning tunneling spectroscopy