Transport Measured Through a Single Atom in a Transistor

Transport has been successfully measured through a single atom in a transistor, giving researchers new insights into the behavior of so-called dopant atoms in silicon, one of the stumbling blocks impeding the further miniaturization of electronics.

Researchers from Delft University of Technology and the FOM Foundation (Fundamental Research on Matter) were able to measure and manipulate a single dopant atom in a realistic semiconducting environment. They published their findings recently in the journal Physical Review Letters.

An electronmicroscopic image of the FinFET industrial transistor used for the Delft research. (Image: TU Delft)

The electronics industry uses a semiconducting material, primarily silicon, that contains dopant atoms to give the silicon the desired electronic characteristics. Through miniaturization, the number of dopant atoms per transistor has become extremely small (only a few dozen), making the position and effect of each individual atom a huge factor in how the entire transistor works. This means that two transistor chips, manufactured identically, can differ from each other and behave differently. This is an alarming situation for the electronics industry, the researchers said, which faces increasing pressure to make products increasingly smaller while improving performance.

Researchers Hermann Sellier, Gabri Lansbergen, Jaap Caro and Sven Rogge of the Kavli Institute of Nanoscience Delft and the FOM Foundation successfully measured a single dopant atom in a semiconducting environment. The scientists, who work in the Photronic Devices research group, transported a charge through one atom and measured and manipulated the quantum mechanical behavior of a single dopant atom, successfully placing one or two electrons in a particular shell of the atom.

The Delft researchers used an advanced industrial transistor (a MOSFET) called FinFET, made as a prototype by IMEC, a research center in Leuven, Belgium. In this transistor, which consists of approximately 35-nm-wide silicon nanowires, the electrical current flows through a single dopant atom (in this case, arsenic). The nanowire is connected to a "gate"; by applying a voltage to the gate, the researchers enable the electrons to flow through the arsenic atom (from the "source" to the "drain"). By detailed measurements of the electrical current's behavior, researchers can observe the effects.

This research however does immediately solve the problems of miniaturization, but it does provide the industry with greater insights into the (quantum mechanical) behavior of transitions on the nanolevel, the scientists said.

The research conducted at the Kavli Institute not only provided new insights into the atomic physics occurring inside a solid, but it also resembles a structure needed to build the still-theoretical quantum computer based on dopant atoms in silicon, the scientists said.

For more information, visit: www.ns.tudelft.nl