Seminarium Advanced Methods of Semiconductor Research – wtorek 5 maja 2026
We cordially invite you to Advanced Methods of Semiconductor Research Seminar on Tuesday 5th of May 2026 at 13:15 in room 321, building A-1, where there will be delivered a lecture:
The use of fiber optics in spectroscopic setups for studying van der Waals crystals
by Dr. Karolina Ciesiołkiewicz-Klepek
from Department of Semiconductor Materials Engineering, Wrocław Tech
This presentation is related to participation in the employment procedure at Wrocław Tech.
The lecture abstract is attached below.
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Two-dimensional transition metal dichalcogenides (TMDCs) exhibit strong excitonic effects and composition-dependent optical properties, making them attractive for tunable optoelectronic and photonic applications. However, reliable characterization of monolayers and ultrathin films, particularly under variable temperature conditions, remains experimentally challenging due to their small thickness and sensitivity to environmental perturbations. In this work, we present an optical fiber-based spectroscopy platform designed for investigating the optical properties of van der Waals materials. The studied samples are transferred directly onto the core of a multimode optical fiber placed inside a cryostat, forming a compact lab-on-fiber configuration that enables stable transmission measurements while minimizing thermal drift and mechanical vibrations.
Using this system, we investigate the optical response of TMDC monolayers, alloys, and their heterostructures through temperature-dependent transmission spectroscopy in the range of 20-320 K. In particular, we study Mo1-xWxS2 and Mo(S1-xSex)2 alloys, in which compositional engineering allows continuous tuning of the electronic band structure. The fiber-based configuration enables precise probing of interband transitions associated with the A, B, and C excitons. Systematic spectral shifts of these transitions are observed as a function of alloy composition: increasing Se content results in a redshift of the excitonic resonances, while substitution of Mo with W produces a blueshift and modifies the spin-orbit-related splitting between the A and B transitions. Temperature-dependent measurements further reveal distinct thermal responses depending on alloy composition.
The presented results demonstrate that fiber-integrated spectroscopy provides a robust and versatile platform for studying ultrathin van der Waals materials and their alloys. By combining high measurement stability with the ability to probe excitonic transitions over a wide temperature range, this approach offers a powerful tool for investigating band structure engineering and optical phenomena in two-dimensional semiconductors.