  Metal chalcogenide is a promising material for studying novel underlying
physical phenomena and nanoelectronics applications. Here, we systematically
investigate the crystal structure and electronic properties of the AlSe surface
alloy on Al (111) using scanning tunneling microscopy, angle-resolved
photoelectron spectrometer, and first-principle calculations. We reveal that
the AlSe surface alloy possesses a hexagonal closed-packed structure. The AlSe
surface alloy comprises two atomic sublayers (Se sublayer and Al sublayer) with
1.16 A along the z direction. The dispersion shows two hole-like bands for AlSe
surface alloy located at about -2.2 eV, far below the Fermi level, which is
sharply different from other metal chalcogenide and binary alloys. These two
bands mainly derive from the in-plane orbital of AlSe (px and py). These
results provide implications for related Al-chalcogen interface. Meanwhile,
AlSe alloy have an advantage of large-scale atomic flatness and a wide band gap
near the Fermi level in serving as an interface for two-dimensional materials.
