Browse Prior Art Database

Functionalized SXM Tip

IP.com Disclosure Number: IPCOM000109240D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 3 page(s) / 186K

Publishing Venue

IBM

Related People

Courtens, EL: AUTHOR [+4]

Abstract

One can exploit interfacial interactions whose distance dependence is less pronounced than that of tunneling by structuring the probe tip such that only a small volume at the apex is sensitive to the interaction of interest. This requires either modification of the material at the apex or attachment of a particle with the desired properties. The size of the structured apex should be well below 100 nm to provide a significant improvement in resolution over existing techniques.

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Functionalized SXM Tip

       One can exploit interfacial interactions whose distance
dependence is less pronounced than that of tunneling by structuring
the probe tip such that only a small volume at the apex is sensitive
to the interaction of interest.  This requires either modification of
the material at the apex or attachment of a particle with the desired
properties.  The size of the structured apex should be well below 100
nm to provide a significant improvement in resolution over existing
techniques.

      A solution to the above-described problem takes advantage of
the hollow structure of micropipettes whose inner diameters can be
reduced to 100 nm and less.

      A micropipette 1 (Fig. 1a) is filled with a liquid 2 that wets
the walls of the micropipette.  Partial wetting is favorable for a
well-defined meniscus 3 and spreading over of the pipette endface.
The particle 4 in principle can be attached to the fluid surface 5,
but solidification of the filled volume will create better defined
mounting conditions.  Solidification can be achieved in various ways,
e.g., by filling at elevated temperature and subsequent freezing,
polymerization, crystallization from an (evaporating) solution, or
electron/UV bombardment.

      In general, only the end of the micropipette 1 is filled,
forming a plug as indicated in Fig. 1. The shape of the endface
depends on the interface energies between the plug material, the
micropipette wall, and the outside medium (air, water, etc.) and on
the filling conditions (pressure, electric fields). It can be convex,
concave, or flat.  The differences in the material properties of plug
and micropipette provide various ways to attach a small particle 4 at
the plug endface.  When immersed into a suspension of such particles,
a single particle can be attracted and attached to the endface by
adhesive forces and/or chemical reaction or, if the plug was made
from a conductive material, by an electric field (Fig. 1b).
Alternatively, the endface of the plug can be modified by chemical
reaction with a fluid or gas into which the micropipette gets
immersed.  For instance, plug and immersion materials may contain the
two components of an epoxy glue which would start to polymerize at
the plug endface.  Electrochemical deposition can be used if the plug
is conductive.  With appropriate electrochemical operating
conditions, the particles can be forced to grow in a desired shape to
form, for instance, a small needle-like magnet.

      As another alternative, the particle can be made to travel from
the wide end of the pipette to the narrow one.  The driving force can
be supplied by mechanical flow of the filling, by electric fields
along the pipette in combination with charged particles, by light
pressure, or by magnetic effects. ...