Dara Gough

North Carolina State University

Major: Materials Science and Engineering
Advisor: Prof. Alex King
Project: Atomic Force Microscopy Studies of Gold Thin Films

Introduction

Thin films of gold are easily made by evaporation, and they are typically polycrystalline, with a "columnar" grain structure. Films of this type (though usually made of materials other than gold) are very widely used in integrated circuits and many other applications. Where grain boundaries meet the film surface, grooves form, and the purpose of this project is to study the development of these grooves as a function of the film thickness. We are also very interested in the intersections of grain boundaries (called triple junctions) and their effect on the groove depth, since this is expected to provide important information about the energy of the triple junctions, which has never been measured.

Objectives

  • To create gold thin films on a glass substrate
  • To determine optimum annealing temperature and time for the films
  • To analyze the samples using the Atomic Force Microscope (AFM)
  • To analyze the images using AFM software

Experimental Approach

  • Create gold thing films via evaporation coating
  • Measure the average thicknesses of the films using a Profilometer
  • Anneal the films at 350oC for 72 hours
  • Use the Atomic Force Microscope (AFM) to obtain surface profiles of the samples at multiple points
  • Analyze the obtained surface profiles using AFM software: obtaining relative heights at the grain center, grain boundary, and triple junction

Findings

  • "Anti-dendrites" (gold recedes from the substrate and is replaced by air; termed by Prof. King) form with the over-annealing of the gold films.
  • The Atomic Force Microscope is a pain to use.


Image 1: This transmitted light microscopy image that shows "anti-dendrite" formation in an over-annealed gold film.
Image 2: This is an AFM image of a gold film. This image depicts grain boundaries clearly as well as triple junctions.
Final Presentation