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Thermodynamic limitations on the resolution obtainable with metal replicas
J T Woodward1, J A Zasadzinski
1Department of Physics, University of California, Santa Barbara 93106, USA.
Journal of Microscopy
|December 1, 1996
Summary
Metal film granularity limits microscopy resolution. This is caused by dewetting, not recrystallization, and is reduced by lowering metal mobility on the sample surface.
Area of Science:
- Materials Science
- Surface Science
- Microscopy
Background:
- Granularity of metal films limits resolution in electron and scanning tunneling microscopy.
- Previous theories attributed this granularity to recrystallization of evaporated metal films.
Purpose of the Study:
- To investigate the fundamental cause of metal film granularity in microscopy.
- To identify factors influencing metal film granularity and microscopy resolution.
Main Methods:
- Thermodynamic analysis of metal film dewetting.
- Examination of evaporated and sputtered amorphous metal alloy films.
- Correlation of metal mobility with film granularity and resolution.
Main Results:
- Metal film granularity arises from dewetting of low surface energy samples by high surface energy metals.
- This dewetting phenomenon is analogous to liquid droplet formation.
- Granularity decreases with increasing alloy melting point, even in non-crystallizing films.
Conclusions:
- Dewetting, driven by surface energy differences, is the primary cause of metal film granularity.
- Metal mobility on the sample surface, influenced by temperature gradients, dictates granularity and resolution.
- Optimizing metal coating for microscopy requires controlling metal mobility to minimize dewetting.