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UE Physical measurements at nanoscale by local probes

Degrees incorporating this pedagocial element :

Description

Goal: Introduction to local probes techniques in the field of nanosciences and nanotechnologies.

Content

1. Introduction to Scanning Probes Microscopy (1h30)

  • Comparison between surface analysis techniques: SEM/TEM, SFA
  • Presentation of the SPM sub-families: STM / SFM / SNOM via examples of applications

2. The Scanning Tunneling Microscope (7h)

  • The tunneling effect
    • STM relevant parameters
    • Expression of the tunneling current
  • The STM instrument
    • Tip fabrication methods
    • Electronic and instrumental chain to measure and control tunnelling current in the pico/nano-ampere range ADC/DAC, I/V converter, lock-in amplifier
    • Source of noises and detection limit
    • Vibration isolation (tutorial on transfer function and damping)
    • Measurement at low temperature : how to operate an STM in a cryostat>
  • Operating STM modes and associated measurements
    • Local density of states (LDOS) and I/V spectroscopy
    • Constant current mode versus constant height mode

3. The Atomic Force Microscope (12h)

  • Why mechanical oscillators
    • Introduction and history
    • Mechanical susceptibility
    • Limits of sensitivity (readout noise and Brownian motion)
    • Working at resonance, decrease the size/mass
  • How to build an AFM
    • Micro fabrication of cantilever and tips
    • Nano positioning (piezo material and issues with them as hysteresis…)
    • Precision position measurements (optical and capacitive)
    • Signal analysis (Homodyne detection, PLL and PID)
  • Operating AFMs
    • Calibration process (cantilever stiffness, position detection)
    • What physical values are accessible (van der Waals, electrical, magnetic, friction forces)
    • Different modes of operation
  • Maps analysis and image processing
    • Surface analysis parameters: rms, ra, skewness, kurtosis, etc
    • Artefacts, tip dilation effect
    • Tilt correction via polynomial subtraction and color scale
    • Tutorial on processing of the images and spectroscopy curves obtained in PW via Gwyddion software