| 1. |
- Alberto, Helena, V, et al.
(författare)
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Characterization of the Interfacial Defect Layer in Chalcopyrite Solar Cells by Depth-Resolved Muon Spin Spectroscopy
- 2022
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Ingår i: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 9:19
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Tidskriftsartikel (refereegranskat)abstract
- As devices become smaller and more complex, the interfaces between adjacent materials become increasingly important and are often critical to device performance. An important research goal is to improve the interface between the absorber and the window layer by inserting buffer layers to adjust the transition. Depth-resolved studies are key for a fundamental understanding of the interface. In the present experiment, the interface between the chalcopyrite Cu(In,Ga)Se-2 absorber and various buffer layers are investigated using low-energy muon spin rotation (mu SR) spectroscopy. Depth resolution in the nm range is achieved by implanting the muons with different energies so that they stop at different depths in the sample. Near the interface, a region about 50 nm wide is detected where the lattice is more distorted than further inside the absorber. The distortion is attributed to the long-range strain field caused by defects. These measurements allow a quantification of the corresponding passivation effect of the buffer layer. Bath-deposited cadmium sulfide provides the best defect passivation in the near interface region, in contrast to the dry-deposited oxides, which have a much smaller effect. The experiment demonstrates the great potential of low energy mu SR spectroscopy for microscopic interfacial studies of multilayer systems.
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| 2. |
- Morenzoni, Elvezio, et al.
(författare)
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Low-Energy Muons at PSI: Examples of Investigations of Superconducting Properties in Near-Surface Regions and Heterostuctures
- 2014
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Ingår i: Proceedings of the International Symposium on Science Explored by Ultra Slow Muon (USM2013). - : The Physical Society of Japan.
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Konferensbidrag (refereegranskat)abstract
- With the advent of polarized low-energy muons, with tunable energy in the kiloelectronvolt range, it is possible to use the sensitivity and the local-probe character of µSR to perform depth-dependent investigations on the nanometer scale of magnetic and superconducting properties of materials. Here, after a brief summary of the present status of LE-µSR at PSI, we give some examples of investigations of superconducting properties in the near-surface regions of single crystals and thin-film materials.
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| 4. |
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| 5. |
- Sugiyama, Jun, et al.
(författare)
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Li-ion diffusion in Li4Ti5O12 and LiTi2O4 battery materials detected by muon spin spectroscopy
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 92:1
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Tidskriftsartikel (refereegranskat)abstract
- Lithium diffusion in spinel Li4Ti5O12 and LiTi2O4 compounds for future battery applications has been studied with muon spin relaxation (mu+SR). Measurements were performed on both thin-film and powder samples in the temperature range between 25 and 500 K. For Li4Ti5O12 and above about similar to 200 K, the field distribution width (Delta) is found to decrease gradually, while the field fluctuation rate (nu) increases exponentially with temperature. For LiTi2O4, on the contrary, the Delta(T) curve shows a steplike decrease at similar to 350 K, around which the nu(T) curve exhibits a local maximum. These behaviors suggest that Li+ starts to diffuse above around 200 K for both spinels. Assuming a jump diffusion of Li+ at the tetrahedral 8a site to the vacant octahedral 16c site, diffusion coefficients of Li+ at 300 K in the film samples are estimated as (3.2 +/- 0.8) x 10(-11) cm(2)/s for Li4Ti5O12 and (3.6 +/- 1.1) x 10(-11) cm(2)/s for LiTi2O4. Further, some small differences are found in both thermal activation energies and Li-ion diffusion coefficients between the powder and thin-film samples.
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| 6. |
- Sugiyama, Jun, et al.
(författare)
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Search for a space charge layer in thin film battery materials with low-energy muons
- 2023
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2462:1
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Konferensbidrag (refereegranskat)abstract
- In an all solid state Li-ion battery, it is crucial to reduce ionic resistivity at the interface between the electrode and the electrolyte in order to enhance Li+ mobility across the interface. Recent first principles calculations predict the presence of a space-charge layer (SCL) at the interface due to the difference in the Li+ chemical potential at the interface between two different materials, as in the metal-semiconductor junction in electronic devices. However, the presence of SCL has never been experimentally observed. Our first attempt in a fresh multilayer sample, Cu(10 nm)/Li3PO4(50 nm)/LiCoO2(100 nm) on a sapphire substrate, with low-energy μ +SR (LE μ +SR) revealed a gradual change in the nuclear magnetic field distribution width as a function of implantation depth even across the interface between Li3PO4 and LiCoO2. This implies that the change in the field distribution width at SCL of the sample is too small to be detected by LE μ +SR.
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| 7. |
- Suter, Andreas, et al.
(författare)
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Two-Dimensional Magnetic and Superconducting Phases in Metal-Insulator La2−xSrxCuO4 Superlattices Studied by Low-Energy Muon-Spin Rotation
- 2014
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Ingår i: Proceedings of the International Symposium on Science Explored by Ultra Slow Muon (USM2013). - : Physical society of Japan. ; , s. 010204-010204
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Konferensbidrag (refereegranskat)abstract
- We show, by means of low-energy muon-spin-rotation measurements, that few-unit-cells thick La2CuO4 layers synthesized digitally by molecular beam epitaxy are antiferromagnetically ordered. Below a thickness of about 5 CuO2 layers the long-range ordered state breaks down, and a magnetic state appears with enhanced quantum fluctuations and a reduced spin stiffness. This magnetic state can exist in close proximity (few Å) to high-temperature superconducting layers, without transmitting supercurrents. Charge-transfer effects and potential softening of the antiferromagnetic state due to the proximity to the superconducting state are discussed.
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| 8. |
- Woerle, Judith, et al.
(författare)
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Interaction of low-energy muons with defect profiles in proton-irradiated Si and 4H-SiC
- 2019
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 100:11
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Tidskriftsartikel (refereegranskat)abstract
- Muon spin rotation (mu SR) with low-energy muons is a powerful nuclear method where electrical and magnetic properties of thin films can be investigated in a depth-resolved manner. Here, we present a study on proton-irradiated Si and 4H-SiC where the formation of the hydrogen-like muonium (Mu) is analyzed as a function of the proton dose. While the Mu formation is strongly suppressed in the highly defective region of the shallow proton stopping profile, the Mu signal quickly recovers for higher muon energies where the muons reach the untreated semiconductor bulk. A lower sensitivity limit of low-energy mu SR to crystal defects of around 10(17) to 10(18) cm(-3) is estimated. Our results demonstrate the high potential of this technique to nondestructively probe near-surface regions without the need for electronic device fabrication and to provide valuable complementary information when investigating defects in semiconductors.
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