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

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

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

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

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

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

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

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

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

Experimental Approach Evaporation coat glass substrates with a gold thin film Thicknesses ranging from (150-450nm) 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

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

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

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

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

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

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

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

Results 170 Data Points

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

Acknowledgements I would like to thank the National Science Foundation (REU Grant DMR-0243830) 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

Questions? (Questions)