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Electron Beam Patterning

Ferroelectric solids contain electric dipoles that are intrinsic to the atomic structure of a compound. For example, in a cubic perovskite, the displacement of the body center cation in the unit cell produces a dipole in that structure. Dipole-dipole interactions between unit cells causes polarization alignment resulting in ferroelectric domains. Polarization discontinuities in the vicinity of surfaces and interfaces result in polarization bound charge that significantly affects materials properties. The orientation of polarization can be altered with the application of an electric field. It is expected that interactions on ferroelectric surfaces will be influenced by the domain orientation. Since it has been demonstrated that domain orientation can be controlled to produce 10-20 nm domains, if the fundamental relationship between atomic polarization, charge compensation and local reactivity can be understood, it could be utilized to direct assembly of nanostructures.

Ebeam 1
  • Electron beam domain switching is an effect of sample charging
  • Positive charging dominated by blue oxide curve
  • Negative charging dominated by green oxide curve

 

AFM topography image
  • AFM topography image displays a matrix of squares that were exposed to a 30keV beam for different lengths of time
  • Image reveals relationship with exposure time and particle density
Piezoresponse Force Microscopy image illustrates our ability to switch c+ and c- domains with e-beams
Piezoresponse Force Microscopy image illustrates our ability to switch c+ and c- domains with e-beams

 

Positive Poling   Negative Poling
  • Flux of ejected electrons exceeds flux of incident electrons
  • Charge gradient sets up electric field strong enough to orient domains in the c+ direction
Positive & Negative E-Beam Poling
  • Flux of ejected electrons is less than flux of incident electrons
  • Carbon layer forms for extended exposure times
  • Carbon layer dominates surface charging characteristics