Surface reconstruction and band alignment of nonmetallic 
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 perovskites

Sung, Ha-Jun; Mochizuki, Yasuhide; Oba, Fumiyasu

doi:10.1103/physrevmaterials.4.044606

Cited by 10 publications

(20 citation statements)

References 114 publications

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“…The electron affinity (EA) and ionization potential (IP) energies were obtained to determine the conduction band (CB) and valence band (VB) edges with respect to the vacuum level, by calculating the planar-averaged electrostatic potential of the nonpolar oxide surfaces of supercells separated by 20 Å thick vacuum layer compared to the macroscopic-averaged crystal potential . IP is evaluated using the following equation: where Δ V is the difference in electrostatic potential between the vacuum level and the reference level, which uses the macroscopic-averaged potential in the slab model.…”

Section: Calculation Methodsmentioning

confidence: 99%

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p-Type Semiconduction in Oxides with Cation Lone Pairs

2022

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Semiconducting oxides are valuable as thin-film displays or solar cell electrodes and are recently of interest as back-end-of-line devices. There are numerous high-mobility n-type semiconducting oxides, but there is a lack of p-type oxides with similar mobility. This led to a search for additional p-type oxides using high-throughput calculations. We find that many of these proposed oxides possess cation s-like lone-pair states. The defect energies of some of these oxides are calculated here in detail. SnTa2O6 is found to be promising p-type oxide based on its low effective hole mass owing to its cation lone-pair character, wide stability range, and absence of compensating native defects. This leads to a desirable p-type doping limit range, which includes the valence band edge, but other oxides with structures more closely based on perovskite configuration are more n-type rather than p-type. The experimentally observed p-type conductivity in related niobium compounds is also discussed. The valence band edge of the disordered SnTa2O6 phase has a mixed O(p)–Sn(s)–O(p) character; thus, it is relatively insensitive to disorders, indicating that it could also make an effective p-type amorphous semiconductor.

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Section: Calculation Methodsmentioning

confidence: 99%

“…The EA value can be determined once IP and band gap are obtained. This method eliminates any explicit effects of the surface states; thus, it is reliable to accurately determine the band edge positions. Note that these electrostatic calculations also used the HSE functional with all results converged.…”

Section: Calculation Methodsmentioning

confidence: 99%

p-Type Semiconduction in Oxides with Cation Lone Pairs

2022

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“…We also found weak positive correlations between ε VBM and the Goldschmidt tolerance factor (see Figure S5 in the Supporting Information), which is similar to the trend of the half-AO-terminated surfaces (the stripe structures) of A 2+ B 4+ O 3 . 66 On the other hand, correlations are unclear between ε CBM or ε VBM and total surface rumpling, as well as those between ε CBM and the Goldschmidt tolerance factor (see Figures S5 and S6 in the Supporting Information).…”

Section: Chemical Trends Of Surface Energy and Bandmentioning

confidence: 99%

“…65 Furthermore, the theoretically reported band positions of the fully AO-and BO 2 -terminated surfaces of A 2+ B 4+ O 3 perovskites are considerably different from each other. 63,66 A recent experimental study by Thapa et al has shown that SrTiO 3 surfaces exhibit a mixture of the SrO and TiO 2 terminations or a full SrO termination during the hybrid oxide molecular beam epitaxy growth of stoichiometric films on SrTiO 3 (001) single crystal substrates. 75 Our previous first-principles calculations have predicted that the band positions of reconstructed SrTiO 3 (001) surfaces with mixed terminations show up to ∼1 eV differences from those of fully SrO-and TiO 2 -terminated surfaces.…”

Section: Introductionmentioning

confidence: 99%

Chemical Trends of Surface Reconstruction and Band Positions of Nonmetallic Perovskite Oxides from First Principles

et al. 2023

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An evolutionary algorithm search in combination with first-principles calculations is performed to systematically predict the reconstructed surface structures of nonmetallic perovskite oxides. Four types of lowest-energy reconstruction patterns are obtained for the macroscopically stoichiometric (001) surfaces of NaTaO3, KTaO3, CaTiO3, SrTiO3, YAlO3, and LaAlO3 as representatives of A + B 5+O3, A 2+ B 4+O3, and A 3+ B 3+O3 systems. We explain chemical trends in the surface energies and band positions of 10 perovskite oxides, additionally including KNbO3, BaTiO3, BaZrO3, and LaGaO3, in terms of the atomic environments at the outermost reconstructed surface layers. Regaining A–O (B–O) coordination numbers and bond lengths at the surfaces is found to stabilize the A 2+ B 4+O3 and A 3+ B 3+O3 (A + B 5+O3) surfaces. Decreasing the coordination number of cation A (B) leads to shallow (deep) valence band maxima and conduction band minima relative to the vacuum level. Our study provides general insights into the surface reconstruction and band alignment of nonmetallic perovskite oxides.

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“…To this end, we must obtain the alignment of the valence band edge (VBE) with respect to the electrochemical water oxidation potential [31,45] for each surface termination. In oxide perovskites (ABO 3 ), the work function difference between the AO-and BO 2 -terminated (001) surfaces is theoretically predicted to be on the scale of a few eV [46,47]. While the specific case of pure SrTiO 3 has been studied in detail using density functional theory (DFT)-based methods [48][49][50], the aqueous interface band alignment remains unexplored.…”

Section: Electronic Structure and Band Alignmentmentioning

confidence: 99%