In a brief paper in Applied Physics Letters, a group from the Solid State Physics department at TU Berlin report an interesting process to build isolating mesas to support single quantum dots. Given a random distribution of quantum dots on a surface, one can select specifically those which suit one’s purposes as follows. Coat the sample with PMMA, scan with an electron beam thereby exciting cathodoluminescence from the quantum dots. Return the beam to the selected locations and invert the resist tone. Develop, etch, ash, etc. This leaves the selected quantum dots isolated from one another, each on its own small mesa. Apparently, the dose required to acquire sufficient luminescence signal is enough to fully expose the PMMA (in the positive sense). This is why the polymerization (tone reversal) step is needed.
The paper can also be found on the arXiv.