Angle-resolved photoemission study of the surface state on TiC(111)

Abstract

Angle-resolved photoemission spectroscopy utilizing synchrotron radiation has been used to study the electronic structure of a TiCQ 96(111)surface. A sharp emission from a surface state is observed at just below the Fermi level (0.20 eV at the I point) which is rapidly quenched by hydrogen adsorption. In addition, a weak emission peak is observed at 0.55 eV, which is also derived from the polar structure of the (111)surface but is insensitive to hydrogen adsorption. The two-dimensional band dispersion of the surface state is not found directly, but o8'-normal-emission measurements suggest that the state disperses upwards for both the I~M and I~E directions above the Fermi level, A resonant enhancement of the surface-state emission is found at h v-45 eV.

Optical and electronic properties of TiCxNy films

“…The overall shape of the spectra for TiN and TiC is consistent with spectra reported previously in the literature. [9][10][11]15,32,34,[37][38][39][40] In both cases the spectrum is formed by three structures. The lowest binding energy valence band feature is associated to the nonmetal ͑N or C͒ 2s electrons.…”

Interaction of Oxygen with the Polar HfC(111) Surface: Angle-Resolved Photoemission Study

“…The broad band is ascribed to the Hf 5d -C 2p bulk band emissions, while the sharp peak at just below E F is attributed to emissions from the surface state mostly composed of 5d orbitals of surface Hf atoms [11,12]. The metal d-derived surface states around E F are commonly observed on all the unreconstructed TMC(111) surfaces [8][9][10][11][12][13][14]. The formation of the surface states results in the redistribution of the electronic charge around the surface, which is predicted to stabilize the polar surface through the screening of the long-range electric field inherent to polar surfaces [9][10][11][12][13][14].…”

“…The metal d-derived surface states around E F are commonly observed on all the unreconstructed TMC(111) surfaces [8][9][10][11][12][13][14]. The formation of the surface states results in the redistribution of the electronic charge around the surface, which is predicted to stabilize the polar surface through the screening of the long-range electric field inherent to polar surfaces [9][10][11][12][13][14]. Details of the surface electronic structure of HfC(111) were discussed in our previous papers [11,12].…”

“…On the other hand, the (111) surface is covered with a hexagonal metal layer. In addition, the surface metal atoms are activated due to the existence of the metal d-derived surface states around E F [8][9][10][11][12], and thus the oxygen should interact preferentially with the surface metal atoms in the case of the (111) surface. The access of O atoms to the substrate C atoms is thus hindered both sterically and electronically, which is thought to be the reason why the oxidation does not proceed on the (111) surface.…”

“…The atomic structure of the (111) surface has been investigated extensively with impact-collision ion scattering spectroscopy (ICISS) for TiC [4], HfC [5], NbC [6] and TaC(111) [7], and it has been established that these surfaces are terminated with (1 × 1) metal layers. A series of angle-resolved photoemission spectroscopy (ARPES) studies have been made on the electronic structures of TiC [8,9], ZrC [10], HfC [11,12], NbC [13] and TaC(111) [14], and these studies have revealed that metal d-derived surface states are formed around the Fermi level (E F ) on all these surfaces. On the (100) surface, such states are lacking and the density of states around E F is relatively small [2].…”