arXiv subjects

Oliver Skibitzki

Publications and source records attributed to Oliver Skibitzki.

6 recordsLinked to original sources

arXiv2026

Nonlinear Elasticity at the Damage Threshold of Semiconductor Nanocrystals

The nonlinear photoacoustic response of indium phosphide nanocrystals on silicon nanotip arrays is investigated using time-resolved optical pump-probe spectroscopy and synchrotron-based X-ray diffraction. Femtosecond laser excitation triggers low-frequency and high-frequency radial breathing modes of the nanocrystals at 8 GHz and 10.3 GHz, respectively. At excitation fluences above 3 mJ/cm^2, nonlinear frequency mixing occurs, including sum- and difference-frequency generation, indicative of strain-induced nonlinear elasticity. A higher-order extension of Hooke's law models the fluence-dependent spectral response and yields a physically valid elastic energy potential. Ex-situ energy-dispersive X-ray spectroscopy reveals a correlation between nanocrystal oxidation and the emergence of nonlinear acoustic modes. Time-resolved X-ray diffraction confirms the nanocrystals as the origin of the low-frequency modes and supports the hypothesis of acoustic decoupling from the substrate. These findings provide insight into the mechanical limits of semiconductor nanostructures under intense optical excitation and suggest new pathways for material characterization and optomechanical control at the nanoscale. The results advance the understanding of nonlinear phonon dynamics in nanocrystals and highlight their potential for integration into next-generation photonic and quantum devices.

cond-mat.mtrl-sci↗

arXiv2026

Direct Orientation Contrast Imaging of Anti-Phase Domains on III-V Materials Using Scanning Electron Microscopy

Direct orientation contrast imaging of zinc-blende III-V materials is studied using scanning electron microscopy. A quantitative approach is taken using a 3 μm thick orientation-patterned GaP grown on GaAs sample, studying the anti-phase domain contrast with respect to the electron beam energy and the tilt angle. A qualitative approach is taken for III-V grown on non-polar materials with and without chemical mechanical polishing. Finally, a processing of the acquired image for GaP on Si reveals in plane preferential anti-phase boundaries.

cond-mat.mtrl-sci↗

arXiv2025

Tunable Light Emission from GaAsP and GaInP Islands Grown on Silicon (001) Nanotips Wafer

In this work, we present the monolithic integration of GaAsP and GaInP islands, selectively grown on a CMOS-compatible Si nanotip wafer using gas-source molecular beam epitaxy via a nanoheteroepitaxy approach. These alloys span a wide electronic bandgap range, from infrared to green; making them highly attractive for optoelectronic applications in silicon photonics. In addition, the nanoheteroepitaxy method enables the growth of various alloy combinations without the need for a lattice-matched substrate. We discuss the epitaxial challenges involved, particularly the balance between growth selectivity and alloy miscibility. Despite these challenges, our work demonstrates a promising and scalable route toward tunable light sources and detectors monolithically integrated on silicon, contributing to the development of compact and efficient photonic components for next-generation silicon-based technologies.

physics.optics↗

arXiv2024

Thermal expansion and temperature dependence of Raman modes in epitaxial layers of Ge and Ge$_{1-x}$Sn$_{x}$

Temperature dependence of vibrational modes in semiconductors depends on lattice thermal expansion and anharmonic phonon-phonon scattering. Evaluating the two contributions from experimental data is not straightforward, especially for epitaxial layers that present mechanical deformation and anisotropic lattice expansion. In this work, a temperature-dependent Raman study in epitaxial Ge and Ge$_{1-x}$Sn$_{x}$ layers is presented. A model is introduced for the Raman mode energy shift as a function of temperature, comprising thermal expansion of the strained lattice and anharmonic corrections. With support of x-ray diffraction, the model is calibrated on experimental data of epitaxial Ge grown on Si and Ge$_{1-x}$Sn$_{x}$ grown on Ge/Si, finding that the main difference between bulk and epitaxial layers is related to the anisotropic lattice expansion. The phonon anharmonicity and other parameters do not depend on dislocation defect density (in the range $7\cdot 10^6$ - $4\cdot 10^8$ cm$^{-2}$) nor on alloy composition in the range 5-14 at.%. The strain-shift coefficient for the main model of Ge and for the Ge-Ge vibrational mode of Ge$_{1-x}$Sn$_{x}$ is weakly dependent on temperature and is around -500 cm$^{-1}$. In Ge$_{1-x}$Sn$_{x}$, the composition-shift coefficient amounts to -100 cm$^{-1}$, independent of temperature and strain.

cond-mat.mtrl-sci↗

arXiv2022

Polarization-Tuned Fano Resonances in All-Dielectric Short-Wave Infrared Metasurface

The short-wave infrared (SWIR) is an underexploited portion of the electromagnetic spectrum in metasurface-based nanophotonics despite its strategic importance in sensing and imaging applications. This is mainly attributed to the lack of material systems to tailor light-matter interactions in this range. Herein, we address this limitation and demonstrate an all-dielectric silicon-integrated metasurface enabling polarization-induced Fano resonance control at SWIR frequencies. The platform consists of a two-dimensional Si/GeSn core/shell nanowire array on a silicon wafer. By tuning the light polarization, we show that the metasurface reflectance can be efficiently engineered due to Fano resonances emerging from the electric and magnetic dipoles competition. The interference of optically induced dipoles in high-index nanowire arrays offers additional degrees of freedom to tailor the directional scattering and the flow of light while enabling sharp polarization-modulated resonances. This tunability is harnessed in nanosensors yielding an efficient detection of 10^{-2} changes in the refractive index of the surrounding medium.

physics.optics↗

arXiv2016

Tunable Schottky barrier and high responsivity in graphene/Si-nanotip optoelectronic device

We demonstrate tunable Schottky barrier height and record photo-responsivity in a new-concept device made of a single-layer CVD graphene transferred onto a matrix of nanotips patterned on n-type Si wafer. The original layout, where nano-sized graphene/Si heterojunctions alternate to graphene areas exposed to the electric field of the Si substrate, which acts both as diode cathode and transistor gate, results in a two-terminal barristor with single-bias control of the Schottky barrier. The nanotip patterning favors light absorption, and the enhancement of the electric field at the tip apex improves photo-charge separation and enables internal gain by impact ionization. These features render the device a photodetector with responsivity (3 A/W for white LED light at 3 mW/cm2 intensity) almost an order of magnitude higher than commercial photodiodes. We extensively characterize the voltage and the temperature dependence of the device parameters and prove that the multi-junction approach does not add extra-inhomogeneity to the Schottky barrier height distribution. This work represents a significant advance in the realization of graphene/Si Schottky devices for optoelectronic applications.

cond-mat.mes-hall↗