UE Physical measurements at nanoscale by local probes

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