the influence of oxygen and hydrogen on gold quantum wires

On the cover: An artist impression of a freely suspended chain of oxygen (red) and gold (gold) atoms. The chain is drawn from a macroscopic gold wire. Preface This thesis is an account of the experimental study on the quantum properties of atomic chains, focussed on the influence of oxygen and hydrogen on a chain of single gold atoms. With this research we have found evidence for the incorporation of oxygen and hydrogen atoms into chains of single gold atoms. The chain formation has been characterized by studying both the conductance, and the chain length, while stretching the quantum wire. Supplementary evidence has been found by using point contact spectroscopy. The oxygen and hydrogen atoms influence the properties of the chain, as a consequence of which we were able to prove the incorporation of the small atoms. Finally we propose a novel explanation for nonlinear behavior of the differential conductance of gold chains affected by hydrogen. The first two chapters describe the general concepts, the experimental setup and the theory of single atom contacts. Chapters three and four show the results of our experiments. These chapters start with showing the recorded data. With references to the work of theoreticians from Brazil and Denmark have we tried to draw conclusions from our obtained results. to finish this thesis directly after the data was obtained, trips to conferences at Oxford and Har-vard, but also teaching to high school student delayed the work significantly; it took me up to June 2006 before all the writing was finished. Jan van Ruitenbeek. I had a very nice time in the group and this work could not have been realized without the help of many people. First of all I want to thank my supervisors. I am also greatful to Sander Otte and Darko Djukic, especially for our fruitful discussions of the two-level model. All the members of the group of AMC for the exciting discussions during coffee breaks, scientific and non-scientific. The discussion were absolutely valuable and learned me to think critical to science and to form an opinion about it. I want to thank the members of the technical department for getting the experiment going in times when things got broken down again. Last but not least, I would like to thank my parents, Rolf and Wineke, and my sisters and brother, Eeuwke, Linde, Annewil, and Ate, for their warm support on all levels.