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Direct Pattern Writing by Local Heating in a Scanning Tunneling Microscope

IP.com Disclosure Number: IPCOM000062427D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Liehr, M: AUTHOR [+2]

Abstract

The scanning tunneling microscope (STM) is known to achieve extremely high spatial resolution - with the ability to observe individual atoms. To date, its application has been limited mainly to atomic-scale structural observations of surfaces. Disclosed here is a new application which achieves two important goals. First, it exploits the intrinsically high spatial resolution of the STM to write nanostructure patterns in the size regime of N 100 ˜, or possibly below. Second, it writes these patterns directly onto the surface, rather than having to write into resist and then develop resist; this brings the advantage that resist processes need not also be constructed along with the new level of lithographic exposure as well. The present scheme exploits local heating by the STM tip to achieve material modification.

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Direct Pattern Writing by Local Heating in a Scanning Tunneling Microscope

The scanning tunneling microscope (STM) is known to achieve extremely high spatial resolution - with the ability to observe individual atoms. To date, its application has been limited mainly to atomic-scale structural observations of surfaces. Disclosed here is a new application which achieves two important goals. First, it exploits the intrinsically high spatial resolution of the STM to write nanostructure patterns in the size regime of N 100 ~, or possibly below. Second, it writes these patterns directly onto the surface, rather than having to write into resist and then develop resist; this brings the advantage that resist processes need not also be constructed along with the new level of lithographic exposure as well. The present scheme exploits local heating by the STM tip to achieve material modification. STM experiments, as presently carried out, use low currents/voltages for tunneling (typically N 1 nA and in the mV range), so that local heating and field evaporation do not change the structure of the surface being measured. However, it is known that the STM tip can be cleaned by running it at higher currents (N 1 mA), which apparently causes some melting of the tungsten tip surface. In the same way, higher currents could be employed to cause local heating of the surface. For example, with the appropriate tip- surface separation to dissipate the current in a region N 100 ~ in size, a 1 mA current yields a current density of 106 A/cm2; for an applied voltage of 1 V, this means that 106 W/cm2 power is dissipated into the small region near the tip. Furthermore, the energy of the hot electrons which reach the surface from the tip is transferred into the top layers of surface, because the electron mean free path is short (< 100 ~). With a power density input of order 1012 W/cm3 into the...