2023-10-19, Besirske, Patricia, Menichetti, Arianna, Montalti, Marco, García‐Ruiz, Juan Manuel, Winterhalder, Martin, Boneberg, Johannes, Cölfen, Helmut

Medical treatment options for bones and teeth can be significantly enhanced by taking control over the crystallization of biomaterials like hydroxyapatite in the healing process. Light‐induced techniques are particularly interesting for this approach as they offer tremendous accuracy in spatial resolution. However, in the field of calcium phosphates, light‐induced crystallization has not been investigated so far. Here, proof of principle is established to successfully induce carbonate‐hydroxyapatite precipitation by light irradiation. Phosphoric acid is released by a photolabile molecule exclusively after irradiation, combining with calcium ions to form a calcium phosphate in the crystallization medium. 4‐Nitrophenylphosphate (4NPP) is established as the photolabile molecule and the system is optimized and fully characterized. A calcium phosphate is crystallized exclusively by irradiation in aqueous solution and identified as carbonate apatite. Control over the localization and stabilization of the carbonate apatite is achieved by a pulsed laser, triggering precipitation in calcium and 4NPP‐containing gel matrices. The results of this communication open up a wide range of new opportunities, both in the field of chemistry for more sophisticated reaction control in localized crystallization processes and in the field of medicine for enhanced treatment of calcium phosphate containing biomaterials.

2021, Feng, Yuyi, Kemmer, Tobias, Graus, Philipp, Nemitz, Clayton A., Leiderer, Paul, Wang, Yongtian, Schmidt-Mende, Lukas, Boneberg, Johannes

Plasmonic metamaterials have recently received increasing attention due to their favorable optical and electrical properties. The physics of the interaction between plasmonic metamaterials and lasers are rich and open opportunities for applications, such as sensing, imaging and photovoltaics. Here, we investigate the mechanism of the interaction between Ag nanorod arrays and nanosecond (ns) pulsed laser. The experimental results show that ns laser pulses significantly improve the crystallinity of the Ag nanorod arrays. Meanwhile, the laser evaporates some of the Ag into the air. This work paves the way for future high-performance plasmonic meta-devices.

2020-07-08, Lenyk, Bohdan, Schöps, Volker, Boneberg, Johannes, Kabdulov, Mikhail, Huhn, Thomas, Scheer, Elke, Offenhäusser, Andreas, Mayer, Dirk

Diarylethene molecules are discussed as possible optical switches, which can reversibly transition between completely conjugated (closed) and nonconjugated (open) forms with different electrical conductance and optical absorbance, by exposure to UV and visible light. However, the opening reaction exhibits, in general, much lower quantum yield than the closing process, hindering their usage in optoelectronic devices. To enhance the opening process, which is supported by visible light, we employ the plasmonic field enhancement of gold films perforated with nanoholes. We show that gold nanohole arrays reveal strong optical transmission in the visible range (~60%) and pronounced enhancement of field intensities, resulting in around 50% faster switching kinetics of the molecular species in comparison with quartz substrates. The experimental UV-Vis measurements are verified with Finite-Difference Time-Domain simulation that confirm the obtained results. Thus, we propose gold nanohole arrays as transparent and conductive plasmonic material that accelerates visible-light-triggered chemical reactions including molecular switching.

2018-12-12, Feng, Yuyi, Kemmer, Tobias, Graus, Philipp, Nemitz, Clayton A., Boneberg, Johannes, Huang, Lingling, Liu, Juan, Wang, Yongtian, Schmidt-Mende, Lukas, Leiderer, Paul

Metallic nanorod metamaterials, arrays of vertically aligned nanorods embedded in an alumina matrix (diameter ~80 nm, length 100-250 nm, period ~113 nm), have recently emerged as a flexible platform for applications in photonics, opto-electronics and sensing. The optical constants for these nanostructured materials are directly associated with their crystallinity. Controlling the crystallinity of these metamaterials in a fast manner has presented a new challenge. Here we show a laser annealing with a pulsed Nd:YAG laser (λ = 532 nm, FWHM 15 ns) to rapidly change the crystallinity of the metallic nanorods. The small column X-Ray diffraction characterization shows that not only the crystallinity of the metallic nanorods is changed, but also that evaporation of the metal occurs with laser annealing.

2021, Wang, Wei, Boneberg, Johannes, Schmidt-Mende, Lukas

Direct laser interference patterning (DLIP) is used to fabricate large-area, periodic surface patterns on Sb₂S₃ substrates to enhance the performance of solar cells. Comparing the power conversion efficiencies (PCE) to the reference cell on flat Sb₂S₃ film, a relative increase of 73% is observed for the DLIP patterned device. Our systematic study reveals that DLIP promotes beneficial crystallization of the Sb₂S₃ film. Light scattering is increased and recombination is depressed in the textured Sb₂S₃ film. It is expected that our study can provide a roadmap for the further development of photovoltaic devices (PVs) based on chalcogenide semiconductors.

2020-08-28, Polushkin, Nikolay I., Möller, Thomas B., Bunyaev, Sergey A., Bondarenko, Artem V., He, Miao, Shugaev, Maxim V., Boneberg, Johannes, Kakazei, Gleb N.

In memory nanodevices based on phase changes induced thermally, the process of information recording is a reversible transition between the structurally ordered (crystalline) and disordered (amorphous) phases that can provide a difference in the physical properties of these two states, for example, in optical reflectivity, electrical resistivity, or magnetic permeability. It is of particular interest to explore whether the chemical disorder is erasable, rewritable, and scalable in solid alloys upon their exposure to short heating pulses. Here, we model this process by assuming second-order phase transitions between chemically ordered and disordered states in the atomic lattice. Our simulations reveal that nanosecond laser irradiation concentrated within a nanoscale spot on the sample surface is able to induce reversible chemical-order (B2)-disorder (A2) transformations (CODTs) in intermetallic Fe-rich Fe_xAl_1–x alloys that exhibit the disorder-induced ferromagnetism. A realization of this concept would provide an alternative approach to current technologies for magnetic recording and data storage, in which the written bits are represented by regions with not a different polarity but with a different magnitude of magnetization. We envision that the proposed approach can be realized with tools used currently for heat-assisted magnetic recording (HAMR), for example, with a near-field transducer (NFT). A specific design for CODT-based magnetic recording media is proposed.

2020, Graus, Philipp, Möller, Thomas B., Leiderer, Paul, Boneberg, Johannes, Polushkin, Nikolay I.

2021, Zhang, Surong, Guo, Chenyang, Ni, Lifa, Hans, Kerstin M., Guhr, Daniel C., Boneberg, Johannes, Guo, Xuefeng, Lee, Takhee, Scheer, Elke, Xiang, Dong

Pairs of electrodes with nanometer gap, termed as nano-gapped electrodes, are fundamental building blocks for the fabrication of nanometer-sized devices and are essential for the examination of molecular properties and extreme nano-optics. Although modern fabrication techniques make it feasible to fabricate nanometer gaps, it is still a formidable challenge to fabricate adjustable gaps arrays with angstrom preci sion. Here, we demonstrate that in-situ adjustable nanogaps (arrays) with sub-angstrom precision can be fabricated via laser irradiation on the substrate which supports the electrode pairs. We further demonstrate that atomic-level metal contacts can be switched and the direction of the switching can be selectively controlled by the laser irradiation position. By varying the laser power gradually, the nanogap’s size can be continuously changed, providing a reliable break junction technique to address the properties of single- molecule junctions. The small spatial focus size of the laser beam makes it feasible to realize addressable on-chip molecular junction arrays.

2020-08-25, Snegir, Sergii, Huhn, Thomas, Boneberg, Johannes, Haus, Simon, Pluchery, Olivier, Scheer, Elke

Developing optoelectronic devices, biological or chemical sensors, displays, and other devices based on nanoparticles (NPs) requires designing tailored NP assemblies on solid substrates, and often with a given surface positioning. In our study, we discuss a new soft-lithographic method for patterning an organic layer, which is capable of binding gold nanoparticles (AuNPs) to the surface. AuNPs with a citrate shell were 17 nm in diameter and prepared by the Turkevich protocol. Our method is based on controlling the binding capability of (3-aminopropyl)trimethoxysilane (APTES)-coated surface by deactivating the −NH₂ terminal groups of APTES under the action of UV-generated ozone in air. We show that partial and complete deactivation can be achieved depending on the atmosphere and exposure time. Using a shadow mask during irradiation, we furthermore show that our method can be applied for creating micron-scale arrays of NPs on APTES-coated substrates with a spatial resolution down to ∼1.5 μm, currently limited by the properties of the mask.

2019-08-16, Kalb, Julian, Weller, Fabian, Irmler, Lukas, Knittel, Vanessa, Graus, Philipp, Boneberg, Johannes, Schmidt-Mende, Lukas

For potential applications of nanostructures, control over their position is important. In this report, we introduce two continuous wave laser-based lithography techniques which allow texturing thin TiO₂ films to create a fine rutile TiO₂ structure on silicon via spatially confined oxidation or a solid-liquid-solid phase transition, for initial layers, we use titanium and anatase TiO₂, respectively. A frequency-doubled Nd:YAG laser at a wavelength of 532 nm is employed for the lithography process and the samples are characterized with scanning electron microscopy. The local orientation of the created rutile crystals is determined by the spatial orientation of hydrothermally grown rutile TiO₂ nanorods. Depending on the technique, we obtain either randomly aligned or highly ordered nanorod ensembles. An additional chemically inert SiO₂ cover layer suppresses the chemical and electronic surface properties of TiO₂ and is removed locally with the laser treatment. Hence, the resulting texture provides a specific topography and crystal structure as well as a high contrast of surface properties on a nanoscale, including the position-controlled growth of TiO₂ nanorods.