2.3 Patterning process asymmetry

Using simultaneous pulses for force and temperature leads to a patterning process that is not fully symmetric in x and y direction. As a result, the transitions shown in Fig. S4A of the manuscript from an unpatterned to a patterned area are wider along the x-direction (w 30 nm) than along the y-direction (w 20 nm). The horizontal axis of the image corresponds to the fast scanning axis of the setup and is aligned parallel to the long axis of the cantilever. A finite angle of the cantilever with respect to the substrate of w 3^° and the thermal expansion of the lever along its long axis during the heating of the tip cause a motion along the fast scanning axis during a patterning event, which is responsible for the asymmetry. As a result of the asymmetric writing process the patterning depth along the y axis within the patterned areas is modulated. The modulation is w 1 nm in amplitude and does not influence the transfer process into the underlying substrate, as shown in Fig. 3 of the manuscript. The regularity of the modulation is a sign that the position accuracy of the tip is substantially better than the 29 nm pixel size and

that each patterning event is highly reproducible. As demonstrated in Fig. 2 of the manuscript, mainly thermal expansion contributes to the asymmetric writing behavior and can be overcome by adequate heat pulse shaping.

2.4 Tip endurance

To evaluate the tip endurance, we wrote several patterns with the same tip and measured the tip geometry and the patterned fields afterwards using a scanning electron microscope (SEM). The results are displayed in Fig. S5. The total volume removed is « 0.5^m³. This volume corresponds to a cube with a side length of ~ 800 nm. This cube has approximately the size of Fig. S5B at the same scale as the tip in the figure. Within the resolution limit of our SEM instrument, we found no degradation or consumption of silicon on the tip. If present at all, residues on the tip amount to a volume of less than (15nm)³. Therefore the amount of material deposited on the tip is more than 10⁵ times smaller than the amount of material removed from the surface.

2.5 Conformal 3d patterning

For a faithful reproduction of 3D structures, each patterning step must be reproducible and independent of the already existing structures created in preceding steps. Fig. S6A shows a pyramid consisting of 25 written levels with a patterning depth of 0.3 nm each. In each writing step, a defined layer of the molecular glass is removed, leading to a conformal replication of the pyramid as demonstrated by its linear cross section shown in Fig. S6B.

Fig. S5. Tip evaluation after patterning. (A) AFM image of a pattern written in two consecutive steps for the two patterning depths into a 100 nm thick molecular glass film. Force and heat-pulse durations of 5.5 /zs, a tip heater temperature of 300 ± 30 °C and a force of 80 ± 10 nN were applied for each pixel. The quality is similar to the result shown in Fig. 2 in the manuscript. (B) SEM micrograph of the tip after writing the pattern shown in panel a (4.5 x 10⁵ write events) and several other patterns. The outline of the unused tip is overlaid in red. A total number of 2.2 x 10⁶ write events were performed, and subsequently the patterns were imaged using a total linear scan distance of 1.7 m. At the resolution of the instrument, the degradation of the tip is not detectable. (C) SEM micrograph of another pattern written with the same tip. No redeposition of material is found on the surface.

Fig. S6. Conformal 3D patterning. (A) Pyramid written into the molecular glass using 25 consecutive patterning steps. (B) Cross section through the pyramid, demonstrating the linearity of the repeated patterning process.

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