Principle

Approaching a very sharp metal tip to an electrically conductive sample by applying a electrical field leads to a current between tip and sample without any mechanical contact. This so-called tunneling current is used to investigate the electronic topography on the sub nanometer scale of a fresh prepared graphite (HOPG) surface. By scanning the tip line by line across the surface graphite atoms and the hexagonal structure are imaged.

Benefits

• Observe atoms within minutes
• Custom-designed for use in teaching labs
• Microscope consists of one compact, portable instrument, no additional instruments required
• Vibration-isolated for better and reproducible results
• Can be used both for imaging of atomic resolution and for spectroscopy
• Additional experiment with gold sample can be performed
• With interactive teaching and learning software

Tasks

1. Prepare a Pt-Ir tip and the graphite (HOPG) sample and approach the tip to the sample.
2. Investigate the topography of clean terraces and the step height between neighboring terraces in constant-current mode.
3. Image the arrangement of graphite atoms on a clean terrace by optimizing tunneling and scanning parameters. Interpret  the structure by analyzing angles and distances between atoms and atomic rows and by using the 2D and 3D graphite model.
4. Measure and compare images in the constant-height and constant-current modes.

Learning objectives

• Tunneling effect
• Hexagonal structures
• Scanning Tunneling Microscopy (STM)
• Imaging on the sub nanometer scale
• Piezo-electric devices
• Local Density Of States (LDOS)
• Constant-Height-Mode 
• Constant-Current-Mode

Software included. Computer not provided.