Agilent has a long history of electronic measurements but I often get questions about our newest product line - the atomic force microscope or AFM.  So what is an atomic force microscope and how does it work?

AFM stands for Atomic Force Microscopy or Atomic Force Microscope and is often called the “Eye of Nanotechnology”. AFM, also referred to as SPM or Scanning Probe Microscopy, is a high-resolution imaging technique that can resolve features as small as an atomic lattice in the real space. It allows researchers to observe and manipulate molecular and atomic level features.

How AFM works is illustrated in the figure below. An AFM works by bringing a cantilever tip in contact with the surface to be imaged. An ionic repulsive force from the surface applied to the tip bends the cantilever upwards. The amount of bending, measured by a laser spot reflected on to a split photo detector, can be used to calculate the force. By keeping the force constant while scanning the tip across the surface, the vertical movement of the tip follows the surface profile and is recorded as the surface topography by the AFM.

The predecessor of AFM is STM, Scanning Tunneling Microscopy or the Scanning Tunneling Microscope, was invented in 1981 by G. Binnig and H. Rohrer who shared the 1986 Nobel Price in Physics for their invention. An excellent technique, STM is limited to imaging conducting surfaces.

AFM has much broader potential and application because it can be used for imaging any conducting or non-conducting surface. The number of applications for AFM has exploded since it was invented in 1986 and now encompass many fields of nanoscience and nanotechnology. It provides the ability to view and understand events as they occur at the molecular level which will increase our understanding of how systems work and lead to new discoveries in many fields. These include life science, materials science, electrochemistry, polymer science, biophysics, nanotechnology, and biotechnology.

 AFM has a number of advantages over other techniques making it a favorite among leading researchers. It provides easily achievable high-resolution and three-dimensional information in real space with little sample preparation for low-cost. In-situ observations, imaging in fluids, temperature and environmental controls are all available.  The Agilent AFM’s have a number of modes that let one measure hardness, elasticity, friction, and adhesion in addition to the 3D topology.  Over time we plan to add more modes to our AFM’s - stay tuned. 

If you want more complete information on the Agilent atomic force microscopes - go to the Agilent AFM website at www.agilent.com/find/AFM.

Click on the AFM Image Library on the nanotechnology home page (www.agilent.com/find/nano) to see examples of images and applications that are possible with the Agilent atomic force microscopes. 

The Agilent 4294A Impedance Analyzer is a very popular product for MEMS (micro electromechanical systems) measurements.  Although technically not considered nanotechnology, the measurement principles apply to nanoscale devices.  Agilent has an application note for using this product with a probing station to measure MEMS.  I think you will find this application very appropriate for those of you interested in making impedance measurements at the nanoscale. 

Check out Application Note 1369-3 “Accurate Impedance Measurement with a Cascade Microtech Probe System”.  If you want more information on MEMS and NEMS measurements from Agilent - go to this Agilent web page - www.agilent.com/find/mems

In the June issue of Nature Nanotechnology Harvard University and the University of Hawaii at Manoa have found a way to align carbon nanotubes and nanowires in a cm samples.  Their technique involves suspending the nanodevices in a polymer epoxy and blowing bubbles into the solution to align the nanoscale devices.   The process could lead to a way to produce arrays of transistors. 

 The researchers used an Agilent Semiconductor Analyzer to characterize the current and voltage of these aligned nanotubes and nanowires.  We know that researchers like to use these semiconductor analyzers for nanotaechnology research so we’ve added specific carbon nanotube FET set-ups in the library of functions for the Agilent B1500A Semiconductor Analyzer.  We’ve had a number of positive remarks from researchers who find the touch-screen set-up quite easy to use and flexible to implement. 

What do you use for your electrical characterizations of nanotubes and nanowires?  Post your successes so others can learn from experience.