Substrate thermal conductivity controls the ability to manufacture microstructures via laser-induced direct write

Abstract

In controlling the thermal properties of the surrounding environment, we provide insight to underlying mechanisms driving the widely-used laser direct write method for additive manufacturing. 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 high-repetition, ultrafast laser pulses. Furthermore, varying the geometry of the heat affected zone, which is controllable based on in-plane thermal diffusion, driven by the substrate thermal conductivity, and laser power, allows for control of the written geometries without any prior substrate preparation. 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.

Direct Laser Writing from Aqueous Precursors for Nano to Microscale Topographical Control, Integration, and Synthesis of Nanocrystalline Mixed Metal Oxides

“…We also examined how the line width varied as a function of material for consistent laser deposition conditions and did observe material-dependent effects (Table S2). To test if variations in thermal conductivity could account for the material-dependent resolution, we measured the thermal conductivities for several oxides (Table S3) but found no correlation. Instead, we experimentally observe that bubbles, generated due to heating at the reaction site, seem to significantly influence achievable line widths; materials for which bubbles do not adhere tend to have higher resolutions (e.g., Mn 2 O 3 , SI Video 1), while for those materials where bubbles persist pinned to the deposition site contribute to lower resolutions (e.g., Cr 2 O 3 , SI Video 2), likely a result of lateral heat deflection and spreading at the bubble–water interface …”

Tunable reflection coating to reduce exposure power threshold for interference-assisted two-photon polymerization lithography

“…The development of TPP lithography for more than two decades has demonstrated enormous advantages in the field of 3D photonic devices, but there are few reports on the fabrication of 2D semiconductor electronic devices. 7) Different from traditional TPP on glass substrates, [8][9][10] semiconductor devices require lithographic substrates to be SOI, 11) silicon, 12,13) silicon nitride, 14) metal, 15,16) and other reflective/opaque substrates, 17) etc. However, due to the high spatial coherence of the light source in TPP, when the laser is focused on the photoresist-substrate interface, the incident light and the reflected light interfere and superimpose to form a standing wave, resulting in periodic undulating oscillations at the side wall of the photoresist pattern.…”