Jörg Pezoldt

Multizone synthesis and localized deposition of bimetallic nanoarchitectures remain major challenges in additive manufacturing at the nanoscale, particularly when control over nanoarchitecture and localized functionality is required. Here, a multizone gas-phase electrodeposition strategy for the simultaneous synthesis and localized deposition of Pt/In core−shell nanoparticles through coupled vapor-phase encapsulation and electrostatic confinement is reported. In contrast to previous gas-phase electrodeposition studies that primarily focused on metallic and metal-oxide nano- and microarchitectures, the present work extends the process to bimetallic core−shell nanoarchitectures as functional nanoscale building blocks. Spark-generated Pt nanoparticles interact in flight with transported In vapor, enabling ligand-free Pt/In encapsulation before deposition. By controlling the In vapor supply through the evaporation temperature, two distinct nanoarchitectures are obtained: centric Pt-core/In-shell nanoparticles (evaporation temperature 750 °C) and eccentric core−shell nanoparticles (evaporation temperature 900 °C) with asymmetric shell distribution. In-flight particle collection reveals that the asymmetry initiates during high-temperature formation and becomes more pronounced during cooling after deposition. The charged Pt/In core−shell nanoparticles are selectively deposited into predefined Si micro-openings and linear patterns. The eccentric Pt/In structures exhibit broadened visible-light absorption and generate a measurable photo-thermoelectric response under illumination at 532 nm. The polarity reversal strongly supports the thermoelectric origin of the response. This approach establishes gas-phase electrodeposition as a route toward localized bimetallic core−shell nanoarchitectures for optothermal and thermoelectric applications.

The morphology of CVD-grown molybdenum disulfide (MoS₂) is sensitive to the local precursor environment, which governs nucleation density, edge stability, and growth kinetics. In this work, we systematically investigate the effect of precursor ratio on the morphological evolution of MoS₂ microstructures synthesized by atmospheric-pressure chemical vapor deposition on SiO₂/Si substrates. By varying the relative amounts of MoO₃ and sulfur precursors, distinct growth regimes were obtained, ranging from compact hexagonal and quasi-circular domains to multilayer hexagonal structures, triangular domains, and dendritic morphologies. At higher MoO₃ loading, growth is dominated by dense nucleation, leading to isolated few-layer hexagonal domains. A moderate reduction in Mo precursor concentration promotes diffusion-assisted growth and secondary nucleation, resulting in multilayer hexagonal structures with aligned or slightly rotated stacked layers. Under sulfur-rich conditions, morphology evolves into triangular domains due to anisotropic edge stabilization, while further increase in sulfur concentration gives rise to branched dendritic structures through kinetically limited, diffusion-dominated growth. Cross-sectional FIB analysis reveals dense vertical stacking and lateral displacement of upper layers in the multilayer hexagonal domains. Raman and photoluminescence measurements confirm strong correlations between morphology, layer thickness, and optical response, with thinner regions exhibiting reduced Raman peak separation, enhanced photoluminescence intensity, and blue-shifted excitonic transitions. The results show that, under fixed APCVD reactor geometry, source positions, temperature profile, carrier-gas flow, and nominal growth duration, the nominal MoO₃ to sulfur source-loading ratio reproducibly correlates with the transition between compact hexagonal, multilayer hexagonal, triangular, and dendritic MoS₂ morphologies on amorphous SiO₂/Si substrates. Because vapor-phase Mo- and S-containing partial pressures were not directly measured, this ratio is treated as a nominal source-inventory descriptor rather than as a direct vapor-phase stoichiometric ratio. The observed trends are interpreted using a qualitative thermodynamic and kinetic framework based on precursor fluence, nucleation density, edge stability, and diffusion-limited growth.

Based on the analysis of the defect formation in silicon carbide polytypes in different semiconductor manufacturing processing steps, device operation and environmental-device interaction it is concluded that external material and energy fluxes are generally able to destabilize the polytype structure. The governing reason is the formation of stacking faults and instabilities of the partial dislocation associated with them. A new ansatz is proposed to describe the structural instabilities using none-equilibrium thermodynamics and the entropy production. A criterial form for polyype transitions is proposed. The developed criterial form is applied to describe observed structural instabilities occur­ring under different external actions.

Gas‐phase electrodeposition is presented as a nanoparticle‐based route toward the fabrication of Pt/Al bimetallic stacks (self‐propagating reactive system). This approach enables localized self‐assembly of spark discharge‐synthesized sub‐10‐nm Pt and Al nanoparticles on patterned substrates. Precise control over Pt film morphology (porosity) through modulation of spark power and carrier gas flow rate is demonstrated. Porous Pt layers lead to diffused Pt/Al interfaces, which become sharper for densely packed Pt layers. On ignition, the self‐sustained high‐temperature alloy formation reaction wavefronts are recorded. The bimetallic interface strongly influences the Pt/Al reaction kinetics, with three orders of magnitude faster reaction speeds for sharper interfaces. Porous morphologies and hence diffused interfaces are hindered by excessive air gaps and premixed regions, intermediate porosities achieved speeds of 0.012 m s ⁻¹ , and dense morphologies have sharp interfaces with minimal air pockets reaching speeds up to 6 m s ⁻¹ . Selected area (electron) diffraction (SAED) and X‐Ray diffraction (XRD) studies reveal Al ₂ Pt and Al ₃ Pt ₂ as the dominant alloy phases amongst other intermediate PtAl phases. Furthermore, XRD demonstrates temperature‐dependent facet growth of Pt‐Al alloys. These results prove the critical influence of film morphology on reaction kinetics and emphasize the potential of tuneable Pt/Al bimetallic systems for future energy‐related applications.

This study investigates the chemical vapour deposition (CVD) of molybdenum disulfide (MoS₂) on SiO₂, examining the formation of various grains and grain boundaries (GBs) in single- to few-layer MoS₂. The material, optical, and electronic properties of the resulting MoS₂ were evaluated through Raman and photoluminescence (PL) spectroscopy. Notably, both Raman and photoluminescence intensities were quenched at the GBs. Moreover, a consistent redshift in the photoluminescence peak positions at the grain boundaries indicating local strain or defect-induced modifications. Electrical characterization of lateral 2-terminal backgated devices on individual grains exhibited lower carrier mobility than those fabricated on continuous few-layers MoS₂, with the highest measured mobility reaching 18.6 cm² V⁻¹ s⁻¹. Additionally, the back-gated field effect transistors (FET) on individual grains and continuous fewlayered showed pronounced clockwise hysteresis in their transfer characteristics, revealing the distinctive contribution of MoS₂ surface and MoS₂/SiO₂ interface defects and their associated traps-as primary sources of hysteresis.

The ability to locally engineer semiconducting structures enables the development of next generation nanoscale devices and photonics. Contrary to the widely used selective area epitaxy, an alternative approach for localized single crystal growth on noncrystalline substrates is presented. Individual growth positions are defined by topological design of an electrostatic field above the substrate guiding the material transport of unipolar charged molecules to the nucleation and growth positions. In this way, the topologically designed electric field imprints the geometrical pattern for graphoepitaxial crystallite growth. After nucleation, the growth evolves into vertical growth of three-dimensional high aspect ratio towers tipped with single crystal copper oxide. The demonstrated graphoepitaxial method allows for the facile growth of advanced 3D material structures on noncrystalline substrates.