Surface and bulk electronic structure ofScN(001)investigated by scanning tunneling microscopy/spectroscopy and optical absorption spectroscopy

Abstract

ScN͑001͒ 1 ϫ 1 surfaces have been prepared by growing ScN on MgO͑001͒ using radio frequency molecular beam epitaxy. In situ ultrahigh vacuum scanning tunneling spectroscopy indicates that the Fermi level at the surface lies slightly above the Sc 3d conduction band edge, which is attributed to a downward band bending at the surface. In situ scanning tunneling microscopy is used to image the Sc and N atom sublattices. While only one atom ͑Sc͒ appears at small negative bias, both atoms (Sc and N) appear at certain positive sample biases due to the partially ionic nature of the bonding. Charge accumulation near ionized subsurface donors is evident from the long-range topographic distortions at the surface. The combination of tunneling spectroscopy and optical absorption results show that ScN has an indirect bandgap of 0.9± 0.1 eV and a direct transition at 2.15 eV.

First-principles modeling of localizeddstates with theGW@LDA+Uapproach

“…This value was later revised by the same authors in a more careful experimental study with significantly reduced free-electron concentrations; the combination of scanning tunneling spectroscopy and optical absorption gives an indirect gap of 0.9Ϯ 0.1 eV and a direct gap of 2.15 eV. 103 Figure 1 shows the indirect ͑E g ⌫-X ͒ and direct ͑E g X-X and E g ⌫-⌫ ͒ band gaps of ScN in LDA+ U, G 0 W 0 , and GW 0 @ LDA+ U as a function of U. In LDA+ U, ScN becomes insulating when U is larger than ϳ2.0 eV and the gap increases almost linearly with increasing U.…”

“…99,100 Interest in ScN has recently increased both experimentally and theoretically due to its possible application in optoelectronic devices. [100][101][102][103][104] LDA predicts ScN to be a semimetal with a negative band gap of Ϫ0.14 eV. Recent calculations based on the exact-exchange OEPx ͑Ref.…”

HVPE of scandium nitride on 6H–SiC(0001)

“…Besides its good lattice constant match with GaN, scandium nitride has potentially useful optical and electrical properties: an indirect bandgap of 0.9 eV and an unusually strong direct bandgap of $2.1 eV [11]; and a high electron mobility for high electron concentrations (twice as high as silicon at 10 20 cm À3 ) [12]. The normal crystal structure for ScN is rock salt with a lattice constant of 4.505 Å [3], but its metastable hexagonal form is predicted to have a very high piezoelectric coefficient [13].…”

TBI Calculations of the Elastic Properties and Structural Phase Transformation in Novel Materials: Yttrium Nitride

“…In the electronic industry they are important as electric contact, diffusion barriers, buffer layer etc. In the last few years there has been an increased awareness in scandium, yttrium and lanthanum nitrides due to phase transition and their semiconducting properties [4][5][6][7][8][9]. The exchange and correlation effects were treated using the generalized gradient approximation (GGA) in case of yttrium nitride (YN) by Stampfl et al [8].…”

“…The transition metal compounds MX (M denotes a transition metal element and X denotes one of the non--metallic elements C, N or O) have attracted attention during last decade because of their high hardness, high melting point, wear and corrosion resistance [1][2][3][4][5][6][7][8][9]. The investigation of the behavior of transition metal compounds under high pressure is very important because of two reasons, namely the interests in an antiferromagnetic Mott type insulator in solid state physics and their roles in the interior of the earth [2].…”