Control of the interaction strength of photonic molecules by nanometer precise 3D fabrication

Abstract

Applications for high resolution 3D profiles, so-called grayscale lithography, exist in diverse fields such as optics, nanofluidics and tribology. All of them require the fabrication of patterns with reliable absolute patterning depth independent of the substrate location and target materials. Here we present a complete patterning and pattern-transfer solution based on thermal scanning probe lithography (t-SPL) and dry etching. We demonstrate the fabrication of 3D profiles in silicon and silicon oxide with nanometer scale accuracy of absolute depth levels. An accuracy of less than 1nm standard deviation in t-SPL is achieved by providing an accurate physical model of the writing process to a model-based implementation of a closed-loop lithography process. For transfering the pattern to a target substrate we optimized the etch process and demonstrate linear amplification of grayscale patterns into silicon and silicon oxide with amplification ratios of ∼6 and ∼1, respectively. The performance of the entire process is demonstrated by manufacturing photonic molecules of desired interaction strength. Excellent agreement of fabricated and simulated structures has been achieved.

Nanofluidic rocking Brownian motors

“…The nanofluidic confinement apparatus (NCA) is described in detail in (25) and shown schematically in Fig. S1A.…”

“…Imaging of particles was performed by interferometric scattering detection, (25,27), which provides an excellent signal-to-noise ratio for the detection of small particles. The details are described in (25). In brief, a collimated continuous-wave laser (50 mW, 532.1 ± 0.3 nm, Samba, Cobolt) with a beam diameter of ≈ 0.7 mm was used as light source.…”

“…In our experiments, we typically observed a signal to noise ratio of ≈ 50:1, leading to a localization accuracy of better than 1.5 nm. The particle trajectories were reconstructed by linking the lateral particle positions of the individual frames (25).…”

“…We expand the concept of geometry-induced electrostatic trapping to create complex twodimensional (2D) energy landscapes for nanoparticles by replacing the simple recess geometries with lithographically patterned 3D topographies. The patterns were fabricated using thermal scanning probe lithography (t-SPL) (24), which has a depth accuracy in the nanometer range (25). We implement nanofluidic rocking BMs for our model particle system of 60-nm Au nanospheres.…”

“…S1) (26) using the nanofluidic confinement apparatus described in (27). We used closed-loop t-SPL (25) to pattern the thermally sensitive polymer polyphthalaldehyde with a sawtooth profile along complex-shaped transport tracks having a depth of 30 to 50 nm and a period of L 550 nm ( Fig. 1, B to D).…”