Home > Instruments > SPM Overview

Scanning Probe Microscopy Overview


Description:

In scanning probe microscopy (SPM), commonly termed atomic force microscopy (AFM), the interaction of a stylus probe and sample surface is quantified and mapped across the sample.  The probe or "tip" is of nanometer-scale sharpness, and the standard image is 3D surface topography at a resolution approaching the atomic or molecular scale.  The tip is attached to a microfabricated cantilever of low spring constant.  Property-sensitive imaging modes are performed simultaneous to topographic imaging.  Gaseous or liquid media, plus sample temperature, can be controlled.  Tip chemistry can be modified for controlled studies of probe-sample interaction.

The Characterization Facility has four scanning probe microscopes:

Accessories common to all SPM instruments:

  • Optical access.  Ability to acquire digital video image (except PicoSPM).
  • Cryo-microtome for cross sectioning samples.  Double-D clamp available for mounting cross-sectioned samples in AFM.
  • BNC breakout box: standard or available for use.
  • Custom adder circuit box for signal manipulation, for example to ramp set point during imaging
  • Analog Witec pulsed force mode for adhesion and stiffness imaging (except PicoPlus).
  • Infinitesima ActuResonance controller for manipulating the or quality factor (Q) of cantilever resonance.
  • Mathematica and ICAdams available for quantitative analysis and modeling of force-distance data and dynamic tip-sample interactions, in order to extract sample storage/loss moduli, surface energy, etc.
  • SPIP available for broad suite of image (e.g. grain size) and force curve (e.g. freely jointed chain model) analysis applications.  Freeware programs WSXM and Gwyddion also available.
  • XYZ manipulator to attach SiO2 or polystyrene microspheres to tipless cantilevers
  • Plasma chamber and metal evaporator for chemical modification of tips by users.  Tip modification services available, using silane linkage procedures customized by staff member Dr. Jinping Dong.

Applications:

  • Sensitive to the following properties: surface chemistry, storage/loss modulus, hardness, interfacial energy, crystallinity, polarization, magnetization, surface charge, and local work function (surface potential).
  • Applicable to conductive and non-conductive samples.
  • Samples can be imaged in air or in liquid media in all modes of operation.
  • Can measure tribological response versus load, scan velocity, temperature, relative humidity.

Capabilities:

  • No sample pre-treatment needed and imaging can be performed in air.
  • Sample can be conductive or nonconductive, hard or soft.
  • Positioning resolution is 0.1 nm laterally and 0.01 nm vertically; imaging lateral resolution depends on sample/tip characteristics (adhesive contact mechanics) and typically is of order 1-10 nm.

Sample Images:

Adhesive label: tapping mode images


Adhesive label: XY mapping of Z dependence