| 1. |
- Achermann, M, et al.
(författare)
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Carrier and field dynamics around nanoscale Schottky contacts investigated by ultrafast near-field optics
- 2002
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 65:4
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Tidskriftsartikel (refereegranskat)abstract
- We present femtosecond-resolved optical near-field pump-probe measurements of spatiotemporal carrier dynamics around a single nanoscale tungsten (W) disk embedded in GaAs. In these samples, Schottky contacts are formed at the W/GaAs interface. The experimental results are modeled by a selfconsistent treatment of the drift-diffusion equation for the carriers and Poisson's equation for the built-in electric field. At lower optically excited carrier densities, we observe that the built-in field suppresses electron transport towards and trapping into the metal particles. In this regime, an accumulation of carriers is seen at the edge of the depletion region of the Schottky contacts. The calculation reveals that the formation of a self-induced dynamic potential well is the origin of this result. In the high-density regime, efficient carrier transport towards and trapping into the W nanoparticle take place, resulting from the screening of the built-in field. These results allow us to describe measurements of the carrier dynamics in annealed low-temperature grown GaAs and demonstrate that the coupling of the carrier and field dynamics can substantially affect carrier trapping in metal-semiconductor composite materials.
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| 2. |
- Achermann, M, et al.
(författare)
-
Carrier dynamics around nano-scale Schottky contacts: a femtosecond near-field study
- 2002
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Ingår i: Applied Surface Science. - 1873-5584. ; 190:1-4, s. 513-516
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Tidskriftsartikel (refereegranskat)abstract
- We report spatially and time-resolved measurements of ultrafast carrier dynamics around buried nano-scale Schottky contacts, performed with a novel femtosecond near-field scanning optical microscope. The experimental results are modeled by a self-consistent treatment of the drift-diffusion equation for the carriers and Poisson's equation for the built-in electric field. We show that the built-in field suppresses electron transport towards and trapping into the metal particles at lower optically excited carrier densities. In contrast, efficient electron trapping into the metal occurs at higher electron densities, which screen the built-in field, allowing for efficient transport of electrons towards the Schottky contact. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 3. |
- Achermann, M, et al.
(författare)
-
Nano-scale Schottky contacts: ultrafast drift-diffusion dynamics studied in the optical near field
- 2002
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Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 13:2-4, s. 819-822
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Tidskriftsartikel (refereegranskat)abstract
- We present direct measurements of the ultrafast carrier dynamics around buried nano-scale Schottky contacts with high spatial and time resolution, performed with a novel fermosecond near-field scanning optical microscope, It is shown that high optically excited carrier densities screen the built-in field around a Schottky contact and allow for efficient transport of electrons towards the contact, followed by trapping of electrons into the metal. The experimental results are modeled by a self-consistent treatment of the drift-diffusion equation for the carriers and Poisson's equation for the built-in electric field. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 4. |
- Sievers, S., et al.
(författare)
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Quantitative Measurement of the Magnetic Moment of Individual Magnetic Nanoparticles by Magnetic Force Microscopy
- 2012
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 8:17, s. 2675-2679
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Tidskriftsartikel (refereegranskat)abstract
- The quantitative measurement of the magnetization of individual magnetic nanoparticles (MNPs) using magnetic force microscopy (MFM) is described. Quantitative measurement is realized by calibration of the MFM signal using an MNP reference sample with traceably determined magnetization. A resolution of the magnetic moment of the order of 10-18 A m2 under ambient conditions is demonstrated, which is presently limited by the tip's magnetic moment and the noise level of the instrument. The calibration scheme can be applied to practically any magnetic force microscope and tip, thus allowing a wide range of future applications, for example in nanomagnetism and biotechnology.
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