EPAPS Materials
Part I: Quantum Confinement and K-Point Sample Effects:
There is a quantum confinement in DFT calculations in the present study. The
quantum confinement effect appears due to the limited slab thickness, which in the trough
region of the slab is ~7 Å. Therefore, the small system sizes affect material properties
causing them to deviate from bulk values. Conversely, bandgap was calculated with
progressive K-point mesh sampling and didn’t reveal any significant effect of K-point
sampling on the bandgap value above 2×4×1 grid (EPAPS Fig. 1). The effects of
quantum confinement and K-point sampling for InGaAs are shown in EPAPS Fig. 1 and
in our recent paper [17].
EPAPS Fig. 1 shows the eigenvalues, the engenvalue
populations, and the corresponding bandgaps for bulk vs. slab illustrating the quantum
confinement effect. However, even for the bulk InGaAs, there is a true bandgap. The
slab bandgap value was calculated with different k-point sampling and no significant
band-gap variation was observed for the used 2×4×1 K-point grid and denser grids.
(EPAPS Fig. 1).
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EPAPS Figure 1. The eigenvalues, their occupation and density of states for InGaAs
bulk and slab. (a) bulk InGaAs. (b) clean InGaAs slab at 2×4×1 K-point mesh. (c) clean
InGaAs slab at 4×8×1 K-point mesh. The Fermi level is at 0 eV. DOS curve was
normalized to [0,1] interval. Eigenvalues are presented for all K-points.
Part II: DFT Calculations of DOS of HfO2 and ZrO2 sites on InAs(0 0 1) – (4 × 2)
The electronic structures for the four HfO2 and ZrO2 sites on InAs(0 0 1) – (4 × 2)
described in the paper (trough insertion, row edge site, bridge site, and full coverage) are
shown in EPAPS Figure 2 (a)-(d). Each electronic structure is compared to the results for
the clean β3′(4 × 4) reconstruction. The impact on the electronic structure post MO2
adsorption is nearly identical for both HfO2 and ZrO2. All four MO2 sites produced
improved electronic properties compared to the initial clean surface. The gap state at the
Fermi level induced by the clean InAs reconstruction is reduced by the adsorption of
oxide on the surface. Specifically, the electronic structure for the bridge site [EPAPS
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Fig. 2(c)] reduces the density of states at Fermi level due to the restoration of the trough
In atoms and edge As atoms to bulk-like sp3 hybridized bonding schemes.
Most promising is the electronic structure result for the full coverage MO2 site.
The full coverage site passivates all surface states induced by the trough and produces an
improved electronic structure. The electronic structure results for all MO2/InAs(001)-(4 ×
2) configurations suggest that the covalent nature of the MO2 bonding to the surface
improves the electronic interface properties. When the band structures were calculated
for the adsorbed MO2 surfaces the bandgap was found to be an average of 0.8 eV for each
site, similar to the results for the β3′Alt.(4 × 2) structure.
EPAPS Figure 2. DFT calculated electronic structures for the 4 MO2 (M = Hf, Zr)
adsorption sites simulated compared to the clean InAs(0 0 1)-β3′(4 ×4) electronic
structure (black dashed line). Hf and Zr oxide adsorption sites have almost identical
DOS structures near the Fermi level for all sites modeled. DOS is the density of states
per slab, double unit cell.
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