Related Experiment Videos
How dry are dried samples? Water adsorption measured by STM
J Freund1, J Halbritter, J K Hörber
1EMBL, Heidelberg, Germany.
Microscopy Research and Technique
|March 25, 1999
Summary
Scanning probe microscopy (SPM) is affected by water layers. This study uses SPM to investigate water adsorption on titanium, gold, and graphite surfaces across varying humidity levels.
Area of Science:
- Surface science
- Nanotechnology
- Microscopy
Background:
- Water layers significantly impact scanning probe microscopy (SPM) operation under ambient conditions.
- Adsorbed water influences both sample structure and imaging processes in techniques like Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM).
- Capillary forces from water dominate tip-surface interactions in AFM, while electron transfer is affected in STM.
Purpose of the Study:
- To investigate the distribution and quantity of adsorbed water on different surfaces using STM.
- To understand how relative humidity affects water adsorption on hydrophilic and hydrophobic surfaces.
- To characterize water layer formation from low to high humidity conditions.
Main Methods:
- Utilized Scanning Tunneling Microscopy (STM) for imaging and current/distance spectroscopy.
- Studied hydrophilic (titanium, graphite) and hydrophobic (gold) surfaces.
- Varied relative humidity from 10% to 90%.
Main Results:
- At <15% relative humidity, water presence was detected by current decay length differences compared to UHV conditions.
- On gold, water formed droplets that increased in size and coverage with humidity, forming a film >55% humidity.
- Titanium and graphite surfaces showed closed water layers that thickened with increasing humidity.
Conclusions:
- STM is effective for characterizing adsorbed water layers on various surfaces.
- Water adsorption behavior differs between hydrophilic and hydrophobic surfaces.
- Humidity levels critically dictate water layer formation and thickness, impacting SPM analyses.