arXiv subjects

Aleksandra Krystyna Dąbrowska

Publications and source records attributed to Aleksandra Krystyna Dąbrowska.

4 recordsLinked to original sources

arXiv2026

Ultralow-Tensile Strain Enables Exciton Funneling and Energy Transfer to Boost MoSe2 Photoluminescence Quantum Yield

Strain engineering is a powerful route for controlling the exciton dynamics in van der Waals (vdW) heterostructures (HSs). The interlayer energy transfer (ET) process is another key factor in controlling the photocarrier relaxation pathways in vdW HSs. In this work, we combine these two processes to achieve an 8-fold enhancement to the relative photoluminescence (PL) quantum yield (QY) in a HS formed from monolayers of ReS2 and MoSe2, separated by a thin hBN interlayer, placed onto an hBN bubble. We achieve this enhancement by applying only 0.1% biaxial tensile strain, which results in efficient exciton funneling and an increased transition dipole moment. Our experimental data are supported by first-principles density-functional theory and coherent transfer-matrix method calculations, ruling out optical interference as the dominant origin of the enhancement. This work provides an innovative route for enhancing the PL QY of vdW materials via interplay between the tensile strain and the ET process.

cond-mat.mtrl-sci↗

arXiv2025

Deterministic hBN bubbles as a versatile platform for studies on single-photon emitters

Single-photon emitters (SPEs) in two-dimensional materials are highly promising candidates for quantum technologies. SPEs in hexagonal boron nitride (hBN) have been widely investigated, but mostly in exfoliated or powder samples that require an activation process, making it difficult to compare studies and reproduce results. Here, we address this problem and propose a platform based on large-area metaloraganic vapour phase epitaxy (MOVPE)-grown hBN, which combines reproducibility and scalability with the ability to readily host SPEs without activation. Through the creation of bubbles via electron-beam irradiation, we achieve additional functionalities, including an interference-mediated enhancement of emission by approximately 100-200\%, dedicated structures that allow the relocation of individual emitters across different systems, and the opportunity to investigate strain-induced effects. Moreover, in contrast to other gas-filled bubbles that deflate at low temperatures, our bubbles remain stable under cryogenic conditions, allowing studies as a function of temperature. To improve the control over the shape and position of bubbles, we demonstrate a~mask-based method that enables deterministic control over bubble formation. The presented hBN bubbles constitute a versatile platform for reproducible studies of hBN-based emitters, providing a reliable insight into their nature and properties.

cond-mat.mtrl-sci↗

arXiv2022

Epitaxial hexagonal boron nitride for hydrogen generation by radiolysis of interfacial water

Hydrogen is an important building block in global strategies towards a future green energy system. To make this transition possible, intense scientific efforts are needed, also in the field of materials science. Two-dimensional crystals, such as hexagonal boron nitride (hBN), are very promising in this regard, as it was demonstrated that micrometer-sized exfoliated flakes are excellent barriers to molecular hydrogen. However, it remains an open question whether large-area layers fabricated by industrially relevant methods preserve such promising properties. In this work we show that electron beam-induced splitting of water creates hBN bubbles that effectively store molecular hydrogen for weeks and under extreme mechanical deformation. We demonstrate that epitaxial hBN allows direct visualization and monitoring of the process of hydrogen generation by radiolysis of interfacial water. Our findings show that hBN is not only a potential candidate for hydrogen storage, but also holds promise for the development of unconventional hydrogen production schemes.

physics.chem-ph↗

arXiv2021

Heteroepitaxial growth of high optical quality, wafer-scale van der Waals heterostrucutres

Transition metal dichalcogenides (TMDs) are materials that can exhibit intriguing optical properties like a change of the bandgap from indirect to direct when being thinned down to a monolayer. Well-resolved narrow excitonic resonances can be observed for such monolayers, however only for materials of sufficient crystalline quality, so far mostly available in the form of micrometer-sized flakes. A further significant improvement of optical and electrical properties can be achieved by transferring the TMD on hexagonal boron nitride (hBN). To exploit the full potential of TMDs in future applications, epitaxial techniques have to be developed that not only allow to growlarge-scale, high-quality TMD monolayers, but allow to perform the growth directly on large-scale epitaxial hBN. In this work we address this problem and demonstrate that MoSe2 of high optical quality can be directly grown on epitaxial hBN on an entire two-inch wafer. We developed a combined growth theme for which hBN is first synthesized at high temperature by Metal Organic Vapor Phase Epitaxy (MOVPE) and as a second step MoSe2 is deposited on top by Molecular Beam Epitaxy (MBE) at much lower temperatures. We show that this structure exhibits excellent optical properties, manifested by narrow excitonic lines in the photoluminescence spectra. Moreover, the material is homogeneous on the area of the whole two-inch wafer, with only +/-0.14 meV deviation of excitonic energy. Our mixed growth technique may guide the way for future large-scale production of high quality TMD/hBN heterostructures.

cond-mat.mtrl-sci↗