In this thesis we study the thermal and inertia effects on atomic friction. The Friction Force Microscope (FFM) is simulated with the Tomlinson model. We introduce a method to calculate atomic friction including thermal effects. A novel scaling form is proposed and tested. We also investigate the inertial effects of the bulk and the tips. We find if the bulk is weakly damped, there is hysteresis in the velocity versus driving force curve. When the tips are weakly damped, the friction force shows large deviations. / In the first half of the thesis, we study the atomic friction between an FFM tip and a solid substrate at nonzero temperatures. Through theoretical analysis, we find the frictional force follows an universal scaling form F ∝ const---T2/31n 2/3(T/v), where T is temperature and v is scanning velocity. We test the theoretical results with numerical simulations. The FFM is simulated with the Tomlinson model. A tip is connected to a support with a spring. The support is pulled with a constant scanning velocity. We model the substrate with two different systems: one is a sinusoidal surface potential function for rigid substrate; the other is a ball-spring model for an elastic substrate. We find the friction force follows the scaling form well, with both kinds of substrates. This confirms the universality of our findings. The results also compare well to recent experimental work, permitting the quantitative extraction of microscopic parameters. / In the second half of the thesis, we study the inertial effects on atomic friction with a multiple-tip Tomlinson model. The model consists of an array of tips mounted on a common bulk support. We find if the bulk is weakly damped and driven by an external force, there is hysteresis in the velocity versus driving force curve. The relative amount of hysteresis decreases with the number of tips for incommensurate systems. We also find that if the tips are weakly damped and experience longjumps, then when the bulk is pulled with a constant velocity, the total friction force shows a large deviation. The deviation exists even for incommensurate systems and cannot be averaged out by incorporating more tips. However, the deviation decreases with increasing temperatures. These findings provide new insights on the influence of the inertia of the bulk and the tips. They also shed some light on future multiple-tip FFM experiments.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.102165 |
| Date | January 2005 |
| Creators | Sang, Yi, 1976- |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Physics.) |
| Rights | © Yi Sang, 2005 |
| Relation | alephsysno: 002489122, proquestno: AAINR25245, Theses scanned by UMI/ProQuest. |
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