Less than a week following the announcement of IBM’s miraculous 7-nm chip-ready transistor , another microscopic transistor made headlines — this one is made up of a single molecule plus smidgen of atoms but features a working electrical gate.
An international team of physicists from Paul-Drude-Institut für Festkörperelektronik (PDI) and the Freie Universität Berlin (FUB), Germany, the NTT Basic Research Laboratories (NTT-BRL), Japan, and the U.S. Naval Research Laboratory (NRL), United States, constructed the transistor using a scanning tunneling microscope and managed to successfully control its gate, even at the atomic scale.
No matter the size, all transistors rely on one fundamental element: functioning electrical gates to control the conductance between the source and the drain contacts. But as soon transistors approach the atomic-scale, precise control of the gate becomes nearly impossible using traditional single-electron transportation.
In this case, the scanning tunneling microscope was able to manipulate individually charged atoms by positioning them with the STM tip on the surface of an indium arsenide (InAs) crystal. This approach permitted the team to assemble the electrical gate from positively charged atoms with ultra-precision before placing them at their desired position.
Stefan Fölsch, the physicist at the PDI who led the team, explained that “the molecule is only weakly bound to the InAs template. So, when we bring the STM tip very close to the molecule and apply a bias voltage to the tip-sample junction, single electrons can tunnel between template and tip by hopping via nearly unperturbed molecular orbitals, similar to the working principle of a quantum dot gated by an external electrode. In our case, the charged atoms nearby provide the electrostatic gate potential that regulates the electron flow and the charge state of the molecule.”
Meaning, it functions like a larger transistor. For those craving an in-depth explanation of the fundamental physics at play, the published research may be found in journal Nature Physics.
Source: Sciencedaily
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