Photoconductivity of Hf-based binary metal oxide systems
To explore the possibility of bandgap engineering in binary systems of oxide insulators we studied photoconductivity of nanometer-thin Hf oxide layers containing different concentrations of cations of different sorts (Si, Al, Sr, or Ce) deposited on (100)Si. The lowest bandgap of the Hf:Al oxide is...
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Published in | Journal of applied physics Vol. 104; no. 11; pp. 114103 - 114103-6 |
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Main Authors | , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
American Institute of Physics
01.12.2008
|
Online Access | Get full text |
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Summary: | To explore the possibility of bandgap engineering in binary systems of oxide insulators we studied photoconductivity of nanometer-thin Hf oxide layers containing different concentrations of cations of different sorts (Si, Al, Sr, or Ce) deposited on (100)Si. The lowest bandgap of the Hf:Al oxide is close to the value 6-6.2 eV of elemental amorphous
Al
2
O
3
and insensitive to the Al content for concentrations of Al exceeding 36%. This result suggests that the Al oxide subnetwork with the largest bandgap preserves this energy width while development of a narrower gap of
HfO
2
is prevented possibly by
dilution
of the second cation subnetwork. When Ce is admixed to
HfO
2
an
intermediate
bandgap value (between the
CeO
2
and
HfO
2
bandgap widths) of
5.3
+
0.1
eV
is observed for all concentrations of Ce, suggesting that the electronic structure of both elemental oxide subnetworks which form the binary metal oxide system, is affected. In Hf:Si oxide samples photoconductivity thresholds of 5.6-5.9 eV corresponding to the bandgap of
HfO
2
are observed for all studied Si concentrations, suggesting
phase separation
to occur. The photoconductivity of
SrHfO
3
exhibits two thresholds at 4.4 and 5.7 eV, which are close to the bandgaps of elemental SrO and
HfO
2
, respectively, indicating, again, phase separation. Through this work we have illustrated photoconductivity as a feasible method to trace phase separation in nanometer-thin layers of binary systems of metal oxides. |
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ISSN: | 0021-8979 1089-7550 |
DOI: | 10.1063/1.3020520 |