Refine
Document Type
Way of publication
- Open Access (8)
Language
- English (37)
Keywords
- Photodetectors (2)
- Plasmonics (2)
- Sensors (2)
- Alloys (1)
- C-MOS (1)
- Crystal structure (1)
- Electric currents (1)
- Electromagnetic radiation detectors (1)
- Electronic band structure (1)
- Epitaxy (1)
Institute
Direct-band-gap Germanium-Tin alloys (Ge1-xSnx) with high carrier mobilities are promising materials for nano- and optoelectronics. The concentration of open volume defects in the alloy, such as Sn and Ge vacancies, influences the final device performance. In this article, we present an evaluation of the point defects in molecular-beam-epitaxy grown Ge1-xSnx films treated by post-growth nanosecond-range pulsed laser melting (PLM). Doppler broadening – variable energy positron annihilation spectroscopy and variable energy positron annihilation lifetime spectroscopy are used to investigate the defect nanostructure in the Ge1-xSnx films exposed to increasing laser energy density. The experimental results, supported with ATomic SUPerposition calculations, evidence that after PLM, the average size of the open volume defects increases, which represents a raise in concentration of vacancy agglomerations, but the overall defect density is reduced as a function of the PLM fluence. At the same time, the positron annihilation spectroscopy analysis provides information about dislocations and Ge vacancies decorated by Sn atoms. Moreover, it is shown that the PLM reduces the strain in the layer, while dislocations are responsible for trapping of Sn and formation of small Sn-rich-clusters.
The application of titanium nitride (TiN) as an electrode for electrochemical deposition or characterization requires the removal of an insulating layer from its surface. This process was studied and optimized, and the conditions for the complete removal of this layer through treatment with oxalic acid were formulated. The obtained TiN surfaces were used for the deposition of various conducting and non-conducting polymers. Two different approaches were applied: (i) in situ electrochemical synthesis of the main classes of conducting polymers, including polyaniline, polypyrrole, polythiophene, and selected derivatives thereof, and (ii) electrostatically driven layer-by-layer (LbL) deposition of multilayers of oppositely charged polyelectrolytes. The deposited polymers were characterized by electrochemical methods. The electrochemical properties of the deposited conducting polymers and their deposition on the TiN surface were comparable to those of the metallic electrodes. The films produced via LbL deposition exhibited a pronounced influence of the charge of the last deposited polymer on the redox reaction of ferri/ferrocyanide, validating the charge alteration with each successive polymer layer deposition. The studied deposition technologies can be used for the modification of TiN surfaces required in applications of this material in chemical sensors and other devices.
Optical metasurfaces enable the manipulation of the light–matter interaction in ultrathin layers. Compared with their metal or dielectric counterparts, hybrid metasurfaces resulting from the combination of dielectric and metallic nanostructures can offer increased possibilities for interactions between modes present in the system. Here, we investigate the interaction between lattice resonances in a hybrid metal–dielectric metasurface obtained from a single-step nanofabrication process. Finite-difference time domain simulations show the avoided crossing of the modes appearing in the wavelength-dependent absorptance inside the Ge upon variations in a selected geometry parameter as evidence for strong optical coupling. We find good agreement between the measured and simulated absorptance and reflectance spectra. Our metasurface design can be easily incorporated into a top-down optoelectronic device fabrication process with possible applications ranging from on-chip spectroscopy to sensing.