Figure 3.

Illustration of the role of stochastic processes in controlling structural precision in top-down, bottom-up and damped-driven assembly. Placement of individual atoms, such as dopants, within semiconductor devices is effectively only as good as the device dimension, with current manufacturing methods. I.e., an atom is only constrained to lie somewhere within the “box” created. Placement of edges is typically a fraction of feature size, and is uniform within the length scale of a circuit. Systems, such as diblock copolymers, which self-assemble with no guiding pattern, show excellent short-range order that decays exponentially with distance. The placement of individual molecules within a domain is again controlled by the size of the box. i.e., the domain. Control over individual atom placement is greatest in biomolecules, where it is specified by atomic relationships in, for example, amino acids, and then by the hierarchy of secondary and tertiary structure. Placement precision between biomolecules not bound together decays rapidly as a function of separation.