Nanofabrication of chromium lines by laser-focused atomic deposition
This project [EPG pub# 633] represents the first
demonstration of nanofabrication of a permanent structure using laser focusing
of atoms. The basic geometry consists of a one-dimensional standing wave
grazing across the surface of a silicon wafer. Chromium atoms are focused by
light forces in the nodes of the standing wave into an array of lines with
spacing 212.78 nm:, height 34 ± 10 nm: and width
65 ± 6 nm:. The array covers an area of 0.4 mm: by
1 mm:.
Figure 1. Laser-focused atomic deposition of atoms in a one-dimensional standing wave
In this fabrication process, chromium atoms emerge from an effusive, high temperature oven, are collimated by laser cooling, pass through the laser standing wave, and deposit onto the substrate After deposition, which takes about 10 to 20 minutes, the silicon substrate is removed from the vacuum and observed with an atomic force microscope.
Figure 2. AFM image of Cr lines on a Si substrate.
Lines are approximately 65 nm: wide, and are spaced by 212.78 nm.
Since the original demonstration, we have improved the resolution of the lines by decreasing the waist size of the standing wave (which the paraxial approximation showed us would shorten the focal length of the atom lens). The result has been a reduction of the linewidth to 38 ± 1 nm:, full width at half maximum.
Figure 3. AFM image of improved resolution in laser-focused atomic deposition, showing 38 ± 1 nm:
(FWHM) linewidth.
In addition, we have determined the background of Cr between the lines by making an edge in the deposited Cr pad and measuring the depth of the average deposition with the AFM. When the contribution from 16% other isotopes is subtracted out, the background level was found to be only 10% of the total peak height.
Laser Focused Atomic Deposition
Jabez J. McClelland - NIST
Robert J. Celotta - NIST
Bobby Anderson - Lighthouse, Inc.
Curtis Bradley - Petroleum Institute, Dubai
Rajeev Gupta
Zeina Jabbour - NIST
Eric Palm - University of Florida
Robert Scholten - University of Melbourne
Online: May 1996
Last update: February 2008
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