The system is indeed silicon based. P impurities are placed with atomic control on top of a Silicon surface in a very controlled patters. Wires conducting carriers to the single impurities are made of the same process. Gates modulating the transistor are alos made of the same process. The physics of the device operation is a bit different than room temperature operation of typical impurities that are being referred to below. Here the single impurity acts like a quantum dot, like an artificial atom that can hold 0, 1, or 2 electrons. These transitions are observed int he our experiment and calculated in our theory. The Ohmic action of the one atom tall wires are discussed in a science paper from January. http://science.slashdot.org/story/12/01/06/044208/ohms-law-survives-to-the-atomic-level To learn more about quantum dots and artificial atoms I refer you to free simulation tools on nanoHUB.org: https://nanohub.org/tools/qdot Hopefully I will place a lecture about these single electron devices on nanoHUB soon.