Home > News Release > Press Release > 2008 > A new manipulation method based on atomic force microscopy for the construction of complex atomic patterns of dopants at semiconductor surfaces

A new manipulation method based on atomic force microscopy for the construction of complex atomic patterns of dopants at semiconductor surfaces

Osaka University
National Institute for Materials Science

A team of experimental researchers from the group of Prof. Seizo Morita, at Osaka University, and from the Nanomechanics group of the National Institute for Materials Science has discovered a new atomic manipulation method, that is based on the controlled and reproducible vertical interchange of atoms between the tip of an atomic force microscope (AFM) and a semiconductor surface.

Abstract

A team of experimental researchers from the group of Prof. Seizo Morita, at Osaka University, and from the Nanomechanics group of the National Institute for Materials Science (NIMS; President: Prof. Teruo Kishi) has discovered a new atomic manipulation method, that is based on the controlled and reproducible vertical interchange of atoms between the tip of an atomic force microscope (AFM) and a semiconductor surface.

Using this manipulation method, the researchers demonstrate that it is possible to assemble complex atomic patterns by literally “writing with atoms” (continuously depositing atoms one by one) on a semiconductor surface in a very favorable time scale and at room temperate. They use the AFM as a pencil tool that can plot and erase by alternately depositing two atomic species at a heterogeneous surface.

At variance with previous manipulation techniques, in this work the researchers produce these atomic manipulations by exploring the repulsive part of the short-range chemical interaction between the closest tip-surface atoms. This new method differs from manipulation protocols previously reported using Scanning Tunneling Microscopy (STM) and from other manipulation procedures recently achieved with AFM, that make use of the attractive part of the tip-surface interaction to laterally manipulate atoms without any active participation of the tip, which is only used to tune the interaction of the manipulated atom with the surface.

To gain deeper understanding on the mechanism of these vertical interchange atom manipulations, the Japanese groups have been assisted by a team of theoreticians based at the Universidad Autonoma de Madrid (Madrid, Spain) and the Academy of Science of the Czech Republic (Prague, Czech Republic), that are experts on first-principles atomistic simulations. Working at the limit of current first-principles methods capabilities, and in close collaboration with the experimental researchers, the team of theoreticians have found that the vertical interchange of atoms is controlled by the mechanical properties of a hybrid tip-surface dimer-like structure formed in the repulsive regime of the tip-surface interaction force, and have estimated the energy barriers between the relevant atomic configurations that lead to these manipulations.

The results reported in this paper provide evidence that AFM can be used to incorporate individual dopants in semiconductor surfaces following predetermined and complex atomic arrangements. Although the researchers focus on a tin/silicon alloy, they have reproduced these atomic manipulations in other semiconductor surfaces.

This manipulation technique may pave the way toward selective semiconductor doping, practical implementation of quantum computing, or atomic-based spintronics. The possibility of combining sophisticated vertical and lateral atom manipulations with the capability of AFM for single-atom chemical identification —work published in Nature last year by the same team of researchers— may bring closer the advent of future atomic-level applications, even at room temperature.
This research work is published by Science Magazine, Vol. 322 (#5900) on October the 17th, 2008.


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