The universality of self-organisation: a path to an atom printer?

Abstract

More than 30 years ago, Donald Eigler and Erhard Schweizer spelt the letters IBM by positioning 35 individual xenon atoms at 4 K temperature using a scanning tunnelling microscope. The arrangement took approximately 22 h. This was an outstanding demonstration of control over individual atoms. Since then, 3D printers developed into a near-ubiquitous technology. Nevertheless, with typical resolutions in the micrometres, they are far from the atomic scale of control that the IBM demonstration seemed to herald. Even the highest resolution achieved with ultrafast lasers driving two-photon polymerisation barely reaches 100 nm, three orders of magnitude distant from the atomic scale. Here, we adopt a long-term view when we ask about the possibility of a 3D atom printer, which can build an arbitrarily shaped object of macroscopic dimensions with control over its atomic structure at room temperature and within a reasonable amount of time. After discussing the state-of-the-art technology based on direct laser writing, we identify three fundamental challenges to overcome. The first is the fat fingers problem, which refers to laser wavelengths being much larger than the size of the atoms. The second one is complexity explosion, namely, the number of processing step scales with the inverse cube of the resolution, leading to prohibitively long processing times. The third challenge is the increasing strength of random fluctuations as the size of the smallest volume element to be printed approaches the atomic scale. This requires control over the fluctuations, which we call mischief of fluctuations. Although direct-writing techniques offer sufficient resolution, speed, and excellent flexibility for the mesoscopic scale, each of the three fundamental problems above appears enough to render the atomic scale unreachable. Each of these arise out of a need to control each atom individually and with precision. In contrast, the three challenges of direct writing are not fundamental limitations to self-organisation, this chapter proposes a potential path to a 3D atom printer, where laser-driven self-organisation can complement direct-writing techniques by bridging the atomic and mesoscopic scales.