Imaging molecular adsorbates using scanning tunnelling microscopy and image processing

This paper presents the use of scanning tunnelling microscopy (STM) and digital image processing for accurate atomicscale imaging of molecules. The project has involved the development of image enhancement techniques and a calibration procedure for STMs. Graphite imaging has been successfully used as a reliable method for instrument calibration. This calibration is required due to the undesirable effects that are characteristic of STMs, which result in improper scaling and skewing of images. Image enhancement techniques have been created to reduce the noise effects due to thermal drift and tip hysteresis. These techniques were developed for graphite images, but have also been successfully applied to imaging of molecular adsorbates. Low tunnelling currents are used in STM experiments since any experiment uses a tunneling mechanism. This implies low signal-to-noise ratios, resulting in the need for reliable noise removal techniques. These techniques are a necessary step towards the extended use of STM in imaging molecular adsorbates.