Nearly-free electronlike surface resonance of aβ−Si3N4(0001)/Si(111)−8×8<

Abstract

We report the discovery of a nearly-free electronlike resonant state for a β-Si 3 N 4 (0001)-8 × 8 layer grown on Si(111), as observed by angle-resolved photoemission and scanning tunneling spectroscopy. Comparison with measurements performed on a Si(111)-7 × 7 surface helped us in the identification of the band. It is found that this parabolic state is degenerate with surface projected bulk bands of the Si(111) substrate.

Van der Waals and Graphene-Like Layers of Silicon Nitride and Aluminum Nitride

“…Peaks in the density of states for bias voltages of −0.3, −0.8, −1.5, and −2.3 V, as well as peaks for empty states +0.3 V and +0.8 V, are observed. Similar peaks were observed by many groups [21,24,[32][33][34][35][36][37], and they are usually denoted as S 1 = −0.3 eV, S 2 = −0.8 eV, and S 3 = −1.4 eV; we also observed a state at −2.3 eV, which was detected by the XPS method [38]. Some authors associate certain peaks in the density of state spectrum with specific atoms on the surface (7 × 7), for example, peaks at −0.3 and + 0.3 V are associated with adatoms [21,32], and the peak at −0.8 V is associated with rest atoms [32,37], that is, they are considered in the framework of the approximation of the local density of electronic states of a given atom.…”

“…There are vacancies in the adsorption phase. This confirms the high mobility of atoms in the adsorption phase, which was noted in the work [24]. At present, it is difficult to unequivocally indicate the nature of the protrusions, perhaps they consist of one, two, or several silicon atoms [40,41].…”

“…The authors of the work [24] also have observed a honeycomb structure and have explained it by the manifestation of the crystal structure of β-Si 3 N 4 . The size of the hexagon side in the STM images represented by the authors (see Figure 5a and b in the article [24]), as well as in our case, was about 6 Å.…”

“…The authors of the work [24] also have observed a honeycomb structure and have explained it by the manifestation of the crystal structure of β-Si 3 N 4 . The size of the hexagon side in the STM images represented by the authors (see Figure 5a and b in the article [24]), as well as in our case, was about 6 Å. Let us recall that in the crystal structure of β-Si 3 N 4 , there is a characteristic fragment-a "small" hexagon with a side of 2.75 Å, as shown experimentally, for example, in work [42] with the help of highresolution TEM.…”

“…"Modifications" of this structure such as (11/8 × 11/8) and (3/8 × 3/8) have been discovered and described. Models explaining the appearance of (8 × 8) structure by forming a layer of crystalline silicon nitride β-Si 3 N 4 are dominating in the literature [20][21][22][23][24].…”