期刊
JOURNAL OF APPLIED PHYSICS
卷 115, 期 3, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.4857075
关键词
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资金
- Chemical Sciences division of the Netherlands Organisation for Scientific Research (NWO) [700.56.027]
- NWO
- Technology Foundation STW through the VICI program on Nanomanufacturing
By accurately tuning the SiO2 interlayer thickness the density and polarity of charges in Si/SiO2/Al2O3 stacks can be controlled. We report on the number density, polarity, and physical location of charges present in the stacks as studied by optical second-harmonic generation (SHG). Depending on the SiO2 interlayer thickness (1-150 nm) the effective charge density in the Si/SiO2/Al2O3 stacks ranges from 10(13) to 10(11) cm(-2) for both n- and p-type silicon. The polarity of the charges switches from negative to positive around a SiO2 interlayer thickness of 5-10 nm at which point the effective charge density in the stacks is negligible. This switch in polarity is apparent from spectroscopic, time-dependent, and azimuthal SHG measurements. The observed trends in charge density and polarity can be explained by tunneling of electrons into defect states at the SiO2/Al2O3 interface as well as the presence of fixed and bulk charges at the Si/SiO2 interface and in the SiO2, respectively. This charge mechanism appears to hold generally for Si/SiO2/Al2O3 stacks as similar results were observed for SiO2 films prepared by various techniques. (C) 2014 AIP Publishing LLC.
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