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 (1h30)
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…)
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