1. Atomic Force Microscopy Studies of Gold Thin Films
Dara Gough
Advisor: Prof. King

2. Overview Brief Background Purpose of the project Project objectives
Why use gold films?
Experimental approach
Setbacks
Results

3. Background
The angle formed by the grain surfaces at the grain boundary is constant
The triple junction was ignored in previous research
It is now believed to have a line tension associated with it that affects the grains

4. Background
Theory: Groove (grain boundary and triple junction) depths increase with decreasing grain size
The effects may be significant in Nano-scale

5. Purpose Eventual Goal:
Triple junctions may be “doped” to high levels (Via Diffusion Along the Triple Junction) to make them conductive in an insulating material, or magnetic, or otherwise active regions of near-atomic dimension.
Courtesy of Prof. King

6. Purpose
To study the development of grooves as a function of the film thickness
The relative height (Hr) is approximately equivalent to 4/3 and is derived by the expression: zg
zgb
ztj

7. Objectives To create gold thin films of varying thicknesses
To anneal the film samples
To obtain surface profiles of the samples

8. Objectives To analyze the surface profiles and obtain data points
The data points are the height differences between:
The center of the grain and the middle of the grain boundary
The center of the grain and the triple junction

9. Why Gold? Gold is the ideal metal for this experiment because:
It is polycrystalline
It does not oxidize in atmospheric conditions
It evaporates easily in high temperature-low pressure environment

10. Experimental Approach
Evaporation coat glass substrates with a gold thin film
Thicknesses ranging from ( nm)
Anneal the samples at 350°C for 72 hours
To create dome-shaped grains that are approximately equal in size to the film thickness
Image courtesy of Prof. King

11. Experimental Approach
Obtain profiles of the gold film using the Atomic Force Microscope (AFM)
Multiple images must be taken of each film in order to obtain hundreds of data points
12 x 12 microns
Image courtesy of Raghavan Narayanan

12. Experimental Approach
The next step in the project is to analyze the images
This is done using Scanning Probe Microscopy Software
The software analyzes changes in height along the surface and provides relative height differences

13. Setbacks Problems: Multiple scan errors with the AFM
Vibration lines in images
Improper engagement of the tip
1.0 x 1.0 micron

14. Image courtesy of Raghavan Narayanan
Setbacks
This is an ideal image obtained using the AFM
1.0 x 1.0 micron
This is the type of image obtained from the AFM recently
6 x 6 microns
Image courtesy of Raghavan Narayanan

15. Setbacks My initial set of gold films was over-annealed
This resulted in the gold receding from the substrate

16. Setbacks This optical microscopy image was taken using reflected light
This is the same image taken using transmitted light

17. Image courtesy of Raghavan Narayanan
Results
I was able to begin analyzing an image provided by Raghavan Narayanan
Average grain size is 1270 nm2 (counted 252 grains)
1.0 x 1.0 micron
Image courtesy of Raghavan Narayanan

18. Results
170 Data Points

19. Future Work Take more surface profiles using the AFM
Over a wider variety of film thicknesses (grain sizes)
Analyze the surface profiles using the Scanning Probe Microscopy Software

20. Acknowledgements
I would like to thank the National Science Foundation (REU Grant DMR ) for financing my research alongside the Department of Energy
I would like to thank Prof. Alex King for his support and guidance
I would also like to thank Raghavan Narayanan for his assistance throughout the course of the project

21. Questions?
(Questions)