[en] Here, the thermal properties of plasma-generated aluminum oxyfluoride passivation layers at the surface of aluminum thin films are measured. The oxyfluoride layers are generated using plasmas produced in mixtures of NH₃ and SF₆ to simultaneously remove oxygen and add fluorine to the aluminum surface, an alternative approach to the more conventional two-step methods that utilize HF treatments to remove the native oxide followed by metal-fluoride (e.g., MgF₂, LiF, and AlF₃) thin film deposition that serves to protect the aluminum surface from further oxidation. Here, the change in thermal properties of the layers as a function of plasma processing time is determined. A significant reduction in thermal boundary conductance is measured with the increasing treatment time, which can be related to the increasing fluorine content in the layers. Acoustic reflection measurements suggest this reduced thermal boundary conductance is related to lower bonding strength to aluminum with increasing fluorine.

[en] In controlling the thermal properties of the surrounding environment, we provide insight into the underlying mechanisms driving the widely used laser direct write method for additive manufacturing. In this study, we find that the onset of silver nitrate reduction for the formation of direct write structures directly corresponds to the calculated steady-state temperature rises associated with both continuous wave and high-repetition rate, ultrafast pulsed laser systems. Furthermore, varying the geometry of the heat affected zone, which is controllable based on in-plane thermal diffusion in the substrate, and laser power, allows for control of the written geometries without any prior substrate preparation. In conclusion, these findings allow for the advance of rapid manufacturing of micro- and nanoscale structures with minimal material constraints through consideration of the laser-controllable thermal transport in ionic liquid/substrate media.

[en] Highlights: • Eutectic/Eutectoid processing strategy to produce novel hierarchical microstructure. • Thermal conductivity of β-FeSi₂+Si nanocomposite can be reduced with a few at% Ge. • Local Ge incorporation into Si_1-xGe_x nanoinclusions can be controlled via processing. • Ge incorporation can reduce the β/Si_1-xGe_x thermal boundary conductance by 91%. • Local composition can supersede lengthscales, and may enhance thermal stability.