Insights into the electronic structure of tin() pyrochlore oxides with 5s lone pair states as transparent p-type oxide semiconductors
Developing transparent p-type oxide semiconductors has been a long-standing subject of interest for optoelectronic devices, but it has been hindered by the strongly localized valence band (VB) structure intrinsic to metal oxides. Sn 2+ oxides represented by SnO are proposed as promising p-type semic...
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| Published in | Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 12; no. 29; pp. 11139 - 11148 |
|---|---|
| Main Authors | , , , , |
| Format | Journal Article |
| Language | English |
| Published |
25.07.2024
|
| Online Access | Get full text |
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| Summary: | Developing transparent p-type oxide semiconductors has been a long-standing subject of interest for optoelectronic devices, but it has been hindered by the strongly localized valence band (VB) structure intrinsic to metal oxides. Sn
2+
oxides represented by SnO are proposed as promising p-type semiconductors since the Sn 5s
2
state could help to alleviate the carrier localization at the VB. In this work, using a combination of X-ray spectroscopy and density functional theory calculations, we explore the electronic structures of Sn
2+
-based Sn
2
Nb
2
O
7
and Sn
2
Ta
2
O
7
pyrochlores as wide bandgap p-type oxide semiconductors. Our results show that Sn
2
Nb
2
O
7
and Sn
2
Ta
2
O
7
have large optical bandgaps of 2.8 eV and 3.4 eV, respectively, and better chemical stability over SnO. Both the experimental and theoretical calculations verified the presence of Sn 5s
2
states at the top of the VB of Sn
2
Nb
2
O
7
and Sn
2
Ta
2
O
7
, and the Sn 5s
2
states increase the VB dispersion and result in lower hole effective masses of 2.09
m
e
and 2.23
m
e
for Sn
2
Nb
2
O
7
and Sn
2
Ta
2
O
7
, respectively, but work less effectively than that for SnO. The different VB features originate from the varied Sn-O interactions influenced by crystal structures. The lattice distortions in SnO allow hybridization between Sn 5p orbitals with occupied (Sn 5s-O 2p)* states, forming asymmetrically distributed electronic states with enhanced dispersion. However, in Sn
2
Nb
2
O
7
and Sn
2
Ta
2
O
7
, these interactions are forbidden by their cubic symmetry and lead to less-dispersive electronic states. Increasing lattice distortions in Sn
2
Nb
2
O
7
and Sn
2
Ta
2
O
7
would be necessary to achieve higher hole mobilities. Our findings elucidate the microscopic origins of the optoelectronic properties of tin (
ii
) pyrochlore oxides, highlighting the significant role of synergistic valence band modulation and crystal structural design in advancing high-performance p-type oxide semiconductors.
P-type oxide semiconductor is crucial for advanced electronics. This work reveals the development of tin(
ii
) pyrochlore oxides as transparent p-type oxide semiconductor through synergistic valence band modulation and crystal structural design. |
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| Bibliography: | https://doi.org/10.1039/d4tc01455c Electronic supplementary information (ESI) available. See DOI |
| ISSN: | 2050-7526 2050-7534 |
| DOI: | 10.1039/d4tc01455c |