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🔬Nanoelectronics and Nanofabrication

Scanning probe microscopy techniques are game-changers in nanoelectronics. They let us see and measure things at the atomic level, giving us a window into the nanoscale world that was once invisible.

These tools, like AFM and STM, don't just show us what things look like. They help us understand how materials behave at the tiniest scales, which is crucial for developing new nanoelectronic devices.

Scanning Probe Microscopy Techniques

Fundamental Principles of Scanning Probe Microscopy

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  • Scanning probe microscopy utilizes a physical probe to scan sample surfaces
  • Probe-sample interactions generate high-resolution topographical images
  • Achieves atomic-scale resolution by detecting forces between probe and sample
  • Operates in various environments (vacuum, air, liquid)
  • Enables characterization of mechanical, electrical, and magnetic properties

Atomic Force Microscopy (AFM)

  • Measures atomic-scale forces between probe tip and sample surface
  • Utilizes a cantilever with a sharp tip to scan the sample
  • Cantilever deflection detected by laser reflection onto photodiode
  • Operates in contact, non-contact, and tapping modes
  • Provides topographical information and measures surface forces
  • Achieves resolution down to fractions of a nanometer

Scanning Tunneling Microscopy (STM)

  • Relies on quantum tunneling effect between probe tip and conductive sample
  • Applies bias voltage between tip and sample to induce tunneling current
  • Maintains constant tunneling current by adjusting tip height during scanning
  • Produces atomic-resolution images of conductive and semiconductive surfaces
  • Allows manipulation of individual atoms (atomic-scale engineering)
  • Achieves vertical resolution of 0.01 nm and lateral resolution of 0.1 nm

Near-field Scanning Optical Microscopy (NSOM)

  • Overcomes diffraction limit of conventional optical microscopy
  • Uses a sub-wavelength aperture or sharp tip to illuminate sample in near-field
  • Collects light scattered from sample surface using far-field optics
  • Combines high spatial resolution of scanning probe techniques with spectroscopic capabilities
  • Achieves resolution of 20-50 nm (surpasses Abbe diffraction limit)
  • Enables optical imaging and spectroscopy at nanoscale

Force Spectroscopy

  • Measures interaction forces between probe tip and sample as function of separation
  • Provides information on mechanical properties (elasticity, adhesion)
  • Involves approaching and retracting probe tip from sample surface
  • Generates force-distance curves for quantitative analysis
  • Allows investigation of molecular interactions and material properties
  • Achieves force resolution down to piconewtons

Specialized AFM Modes

Surface Potential and Work Function Mapping

  • Kelvin Probe Force Microscopy (KPFM) measures surface potential differences
  • Applies AC voltage to AFM tip to nullify electrostatic forces
  • Maps work function variations across sample surface
  • Achieves resolution of few nanometers for surface potential imaging
  • Provides insights into electronic properties of materials (semiconductors, organic electronics)

Magnetic Domain Imaging

  • Magnetic Force Microscopy (MFM) detects magnetic forces between tip and sample
  • Uses magnetically coated probe tip to interact with sample's magnetic domains
  • Operates in non-contact mode to minimize topographical interference
  • Maps magnetic field gradients and domain structures
  • Achieves resolution of 20-50 nm for magnetic imaging
  • Applications include data storage devices and spintronics research

Electrical Conductivity Measurements

  • Conductive AFM (C-AFM) measures local electrical properties of samples
  • Utilizes conductive probe tip to apply voltage and measure current
  • Maps conductivity variations across sample surface
  • Enables nanoscale current-voltage (I-V) spectroscopy
  • Achieves spatial resolution of few nanometers for conductivity mapping
  • Applications include semiconductor device characterization and failure analysis


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© 2025 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.