Quartz Crystal Microbalance Studies of Atomic-Scale Friction

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By most recent estimates, improved attention to friction and wear would save developed countries up to 1.6% of their gross national product, or over $100 billion annually in the U.S. alone. The late 1980's and early 1990's particularly marked a renaissance in fundamental areas of tribology (the study of friction and wear), sparked by a number of new experimental and theoretical techniques capable of studying the force of friction in geometries which were well defined at the nanometer scale. This project involves the use of one such technique, namely the Quartz Crystal Microbalance (QCM), (1) to explore the role of energy dissipative mechanisms in the recently discovered, and increasingly controversial phenomenon of superconductivity-dependent friction, (2) to probe the temperature of a simplified sliding contact, a quantity that has been exceptionally difficult to quantify from theoretical, experimental and computational approaches, and (3) to explore the linearity of friction laws governing molecularly thin liquid films over a wide range of length and time scales. A complimentary educational component includes (1) ongoing participation of undergraduates in the research, and (2) direct dissemination of state-of-the-art information on friction to instructors developing curriculum on the topic, as well as to more general audiences through lectures and written reviews. Technical Abstract: The late 1980's and early 1990's marked the advent of a renewed interest in fundamental areas of tribology, sparked by a number of new experimental and theoretical techniques capable of studying the force of friction in geometries which were well defined at the nanometer scale. This project involves the use of one such technique, namely the Quartz Crystal Microbalance, to probe critical issues of importance to this field. A first set of experiments will explore the role of electronic and phononic energy dissipative mechanisms in the recently discovered, and increasingly controversial phenomenon of superconductivity-dependent friction. Magnetic fields perpendicular and parallel to adsorbed layers sliding on Pb and Nb substrates will be employed to drive the system in and out of the superconducting state. A second set of studies involves documentation of the impact of sliding on the two-dimensional melting point of monolayer thick Krypton layers adsorbed on Graphene sheets with variable lattice spacing. The goal of these studies is to probe the temperature of a simplified sliding contact, a quantity that has been exceptionally difficult to quantify from theoretical, experimental and computational approaches. The third set of proposed experiments involves operation of a QCM in conjunction with a blowoff apparatus recently developed at IBM Almaden. The goal here is to explore the linearity of friction laws governing molecularly thin liquid films over a wide range of length and time scales. A complimentary educational component includes (1) ongoing participation of undergraduates in the research, and (2) direct dissemination of state-of-the-art information on friction to instructors developing curriculum on the topic, as well as to more general audiences through lectures and written reviews.