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Dense Ge nanocrystals embedded in TiO2 with exponentially increased photoconduction by field effect
- Source :
- Scientific Reports, Vol 8, Iss 1, Pp 1-11 (2018)
- Publication Year :
- 2018
- Publisher :
- Springer Science and Business Media LLC, 2018.
-
Abstract
- Si and Ge nanocrystals in oxides are of a large interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in nanocrystals. In this work, dense Ge nanocrystals suitable for enhanced photoconduction were fabricated from 60% Ge in TiO2 amorphous layers by low temperature rapid thermal annealing at 550 °C. An exponential increase of the photocurrent with the applied voltage was observed in coplanar structure of Ge nanocrystals composite films deposited on oxidized Si wafers. The behaviour was explained by field effect control of the Fermi level at the Ge nanocrystals-TiO2 layer/substrate interfaces. The blue-shift of the absorption gap from bulk Ge value to 1.14 eV was evidenced in both photocurrent spectra and optical reflection-transmission experiments, in good agreement with quantum confinement induced bandgap broadening in Ge nanocrystal with sizes of about 5 nm as found from HRTEM and XRD investigations. A nonmonotonic spectral dependence of the refractive index is associated to the Ge nanocrystals formation. The nanocrystal morphology is also in good agreement with the Coulomb gap hopping mechanism of T–1/2 -type explaining the temperature dependence of the dark conduction.
- Subjects :
- Photocurrent
Multidisciplinary
Materials science
business.industry
Band gap
lcsh:R
Fermi level
lcsh:Medicine
Field effect
02 engineering and technology
010402 general chemistry
021001 nanoscience & nanotechnology
01 natural sciences
0104 chemical sciences
Amorphous solid
symbols.namesake
Nanocrystal
Quantum dot
symbols
Optoelectronics
lcsh:Q
lcsh:Science
0210 nano-technology
business
High-resolution transmission electron microscopy
Subjects
Details
- ISSN :
- 20452322
- Volume :
- 8
- Database :
- OpenAIRE
- Journal :
- Scientific Reports
- Accession number :
- edsair.doi.dedup.....8393b3feeec35e5667456f2947ba39ac