  Metal mono-chalcogenide compounds offer a large variety of electronic
properties depending on chemical composition, number of layers and
stacking-order. Among them, the InSe has attracted much attention due to the
promise of outstanding electronic properties, attractive quantum physics, and
high photo-response. Metal mono-chalcogenide compounds offer a large variety of
electronic properties depending on chemical composition, number of layers and
stacking-order. Among them, the InSe has attracted much attention due to the
promise of outstanding electronic properties, attractive quantum physics, and
high photo-response. Precise experimental determination of the electronic
structure of InSe is sorely needed for better understanding of potential
properties and device applications. Here, combining scanning tunneling
spectroscopy (STS) and two-photon photoemission spectroscopy (2PPE), we
demonstrate that InSe exhibits a direct band gap of about 1.25 eV located at
the Gamma point of the Brillouin zone (BZ). STS measurements underline the
presence of a finite and almost constant density of states (DOS) near the
conduction band minimum (CBM) and a very sharp one near the maximum of the
valence band (VMB). This particular DOS is generated by a poorly dispersive
nature of the top valence band, as shown by angle resolved photoemission
spectroscopy (ARPES) investigation. technologies. In fact, a hole effective
mass of about m/m0 = -0.95 gammaK direction) was measured. Moreover, using
ARPES measurements a spin-orbit splitting of the deeper-lying bands of about
0.35 eV was evidenced. These findings allow a deeper understanding of the InSe
electronic properties underlying the potential of III-VI semiconductors for
electronic and photonic
