Researchers shine light on atomic transistor

Nov 22, 2006
Researchers shine light on atomic transistor
Electronmicroscopic image of FinFET transistor that was used for the research. Credit: TU Delft

Researchers from TU Delft and the FOM Foundation (Netherlands) have successfully measured transport through a single atom in a transistor. This research offers new insights into the behaviour of so-called dopant atoms in silicon.

The researchers are able to measure and manipulate a single dopant atom in a realistic semi-conducting environment. The individual behaviour of dopant atoms is a stumbling block to the further miniaturisation of electronics.

The researchers have published their findings in the Physical Review Letters.

The electronic industry uses a semiconducting material, dominantly silicon, that contains dopant atoms. This 'contamination' is necessary for giving the silicon the desired electronic characteristics. Owing to the continuing process of miniaturisation, a situation has arisen in which the characteristics of two chips, despite both being manufactured in a totally identical way, still differ from each other.

The number of dopant atoms per transistor has in fact become so small (only a few dozen) that they can no longer be regarded as a continuum. The position and effect of each individual atom influences how the entire transistor works. Effectively, this means that even perfectly manufactured transistors will not behave identically. This is an especially alarming situation for the electronics industry, which has already been feeling the pinch for a number of years.

Researchers Sellier, Lansbergen, Caro and Rogge of TU Delft's Kavli Institute of Nanoscience and the FOM Foundation have successfully managed to measure a single dopant atom in an actual semi-conducting environment. The researchers, who work in the Photronic Devices, transported a charge through one atom. Moreover, they successfully measured and manipulated the quantum mechanical behaviour of a single dopant atom. They were able for example to place one or two electrons in a particular shell of the atom.

The Delft researchers used an advanced industrial transistor (a MOSFET), which was made as a prototype by IMEC, a research centre in Leuven, Belgium. In this transistor, which consists of approximately 35 nanometre-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 behaviour, researchers can observe the remarkable effects.

This research however does not offer an immediate solution to the problems previously mentioned relating to miniaturisation, but it does provide the industry with greater insights into the (quantum mechanical) behaviour of transitions on the nano level. The research conducted at the Kavli Institute of Nanoscience Delft is also extremely interesting from a purely physics point of view.

The transistor that was researched not only provided new insights into the atomic physics occurring inside a solid, but this also resembles a structures that is needed to build a certain type of quantum computer. This still purely theoretical computer–the Kane design–is based on dopant atoms in silicon. One of the advantages of using dopants in silicon is that the realization of such a quantum computer can rely on the extremely well developed silicon nanotechnology.

Citation: H. Sellier, G. P. Lansbergen, J. Caro, and S. Rogge, N. Collaert, I. Ferain, M. Jurczak, and S. Biesemans, "Transport Spectroscopy of a Single Dopant in a Gated Silicon Nanowire", Physical Review Letters volume 97 issue 20, page 206805, 2006. See dx.doi.org/10.1103/PhysRevLett.97.206805

Source: TU Delft

Explore further: Artificial materials are revealing how living things work

add to favorites email to friend print save as pdf

Related Stories

For electronics beyond silicon, a new contender emerges

Sep 16, 2014

Silicon has few serious competitors as the material of choice in the electronics industry. Yet transistors, the switchable valves that control the flow of electrons in a circuit, cannot simply keep shrinking ...

Recommended for you

How cloud chambers revealed subatomic particles

9 hours ago

Atoms are made of electrons, protons and neutrons. Protons and neutrons are in turn made up of quarks. These are just some of the elementary particles that make up the foundation of modern particle physics. ...

When a doughnut becomes an apple

10 hours ago

In experiments using the wonder material graphene, ETH researchers have been able to demonstrate a phenomenon predicted by a Russian physicist more than 50 years ago. They analyzed a layer structure that ...

Uncovering the forbidden side of molecules

Sep 21, 2014

Researchers at the University of Basel in Switzerland have succeeded in observing the "forbidden" infrared spectrum of a charged molecule for the first time. These extremely weak spectra offer perspectives ...

User comments : 0