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| 2. |
- Parhizkar, Shayan, et al.
(författare)
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Two-Dimensional Platinum Diselenide Waveguide-Integrated Infrared Photodetectors
- 2022
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 9:3, s. 859-867
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Tidskriftsartikel (refereegranskat)abstract
- Low-cost, easily integrable photodetectors (PDs) for silicon (Si) photonics are still a bottleneck for photonic-integrated circuits (PICs), especially for wavelengths above 1.8 mu m. Multilayered platinum diselenide (PtSe2) is a semi-metallic two-dimensional (2D) material that can be synthesized below 450 degrees C. We integrate PtSe2-based PDs directly by conformal growth on Si waveguides. The PDs operate at 1550 nm wavelength with a maximum responsivity of 11 mA/W and response times below 8.4 mu s. Fourier-transform IR spectroscopy in the wavelength range from 1.25 to 28 mu m indicates the suitability of PtSe2 for PDs far into the IR wavelength range. Our PtSe2 PDs integrated by direct growth outperform PtSe2 PDs manufactured by standard 2D layer transfer. The combination of IR responsivity, chemical stability, selective and conformal growth at low temperatures, and the potential for high carrier mobility makes PtSe2 an attractive 2D material for optoelectronics and PICs.
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| 3. |
- Schmidt, Ruediger M., et al.
(författare)
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Increasing the carbon deposition rate using sputter yield amplification upon serial magnetron co-sputtering
- 2014
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 252, s. 74-78
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Tidskriftsartikel (refereegranskat)abstract
- Deposition of carbon based materials by magnetron sputtering suffers frequently from the low deposition rate of carbon due to its low sputtering yield. Here, we describe an approach based on the so-called sputtering yield amplification, which significantly increases the sputtering yield. Carbon has been doped by serial co-sputtering with two different elements, namely tungsten and niobium. Both elements provide a significant rate increase. Addition of 3 at.% of Nb increases the deposition rate of carbon by 130%, whereas the same concentration of W increases it by 280%. TRIDYN simulations have been performed, which reproduce the experimental data. Additionally, our experiments find evidence for very long residence times of the dopant in the target as a result of recoil implantation.
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| 4. |
- Schmidt, Rüdiger, et al.
(författare)
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Sputter Yield Amplification of reactively sputtered TiO2
- 2011
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Konferensbidrag (refereegranskat)abstract
- TiO2 is a material with attractive properties which have led to various applications such as anti-reflective coatings [1] or self cleaning surfaces [2]. One of the most applied deposition techniques used for TiO2 is reactive magnetron sputtering. Unfortunately TiO2 suffers from a comparatively low deposition rate when reactively sputtered. To increase the deposition rate, Sputter Yield Amplification (SYA) can be used through recoil of the sputtering species at implanted heavy dopants below the target surface [3,4]. Here we present experimental results showing a large increase of the TiO2 deposition rate when doped with Tungsten. Although SYA has been proposed earlier [5], the production of doped targets was complicated. We have built a designated sputter deposition tool which enables systematic studies of SYA. In this study the rate increase by SYA is investigated for two different dopants, namely Tungsten and Bismuth. Bismuth was chosen since it is the heaviest non-radioactive material available. Our experiments show that the rate increase of TiO2 by Bismuth is surprisingly low. Tungsten on the other hand results in a large rate increase of 160% in DC and 220% in HiPIMS mode. A number of additional experiments have been carried out to verify and explain this observation. Finally TRIDYN [6] simulations have been performed which reproduce the experimental results.
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| 5. |
- Zalden, Peter, et al.
(författare)
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Femtosecond x-ray diffraction reveals a liquid–liquid phase transition in phase-change materials
- 2019
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Ingår i: Science. - Washington, DC : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6445, s. 1062-1067
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Tidskriftsartikel (refereegranskat)abstract
- In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid–liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics.
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