Figure 5. Patterning with Controlled Topography.

6 and10 nm thick Au films were functionalized with an OEG-terminated alkanethiol and arrays of 1×20 pixel ROIs of the OEG SAM were thermally desorbed with a 532 nm laser focused through a 20× (NA0.8) objective with varying laser fluence (50.8–12.8 nJ μm⁻²) and number of iterations (10,000–1) per ROI (see Fig. 1B for the pattern array geometry). Surface topography maps of (A-C) 6 and (D-F) 10 nm Au films after patterning at the indicated fluence and number of iterations were created with white light interferometry. Height traces of the surface topography were acquired as depicted by the dashed white lines. Raised topographical patterning occurred only on 6 nm thick Au films (≥10 iterations at (A) 50.8 or (B) 25.4 nJ μm⁻² and ≥100 iterations at (C) 12.8 nJ μm⁻²) and the extent of the topography increased with increased fluence and number of iterations. The patterned regions increased from nearly flat at low laser energy and/or low number of iterations to ~17 nm at high laser energy and/or increased iterations. (D-F) The higher thermal conductivity of the 10 nm Au films prevented hydrodynamic melting of the Au and only vaporization or chemically-specific patterning occurred. Vaporization of the Au in the patterned regions on 10 nm films resulted in 0.5–1.0 nm indentations (black arrows in the height traces as indicated in D-F). The pattern depth decreased with decreased laser energy and/or fewer iterations. The data demonstrates that LSL allows for fabrication of micropatterns with controlled topography on the nanometer length scale.