Electronic structure of ScN determined using optical spectroscopy, photoemission, and ab initio calculations - art. no. 125119

Experimental and ab initio computational methods are employed to conclusive ly show that ScN is a semiconductor rather than a semimetal, i.e., there is a gap between the N 2p and the Sc 3d bands. Previous experimental investig ators reported, in agreement with band structure calculations showing a ban d overlap of 0.2 eV, that ScN is a semimetal while others concluded that it is a semiconductor with a band gap larger than 2 eV. We have grown high qu ality, single crystalline ScN layers on MgO(001) and on TiN(001) buffer lay ers on MgO(001) by ultrahigh vacuum reactive magnetron sputter deposition. ScN optical properties were determined by transmission, reflection, and spe ctroscopic ellipsometry while in-situ x-ray and ultraviolet valence band ph otoelectron spectroscopy were used to determine the density of stares (DOS) below the Fermi level. The measured DOS exhibits peaks at 3.8 and 5.2 eV s temming from the N 2p bands and at 15.3 eV due to the N 2s bands. The imagi nary part of the measured dielectric function epsilon (2) consists of two p rimary features due to direct X- and Gamma -point transitions at photon ene rgies of 2.7 and 3.8 eV, respectively. For comparison, the ScN band structu re was calculated using an nb initio Kohn-Sham approach which treats the ex change interactions exactly within density-functional theory. Calculated DO S and the complex dielectric function are in good agreement with our ScN va lence-band photoelectron spectra and measured optical properties. respectiv ely. We conclude, combining experimental and computational results, that Sc N is a semiconductor with an indirect Gamma -X bandgap of 1.3 +/- 0.3 eV an d a direct X-point gap of 2.4 +/- 0.3 eV.