| With the shift to smaller and smaller microelectronic components that run faster, longer, and more reliably, a need for understanding the fundamentals of deformation at the nanoscale is desired. From large scale bulk materials used in buildings and automobiles to thin films in micro-electro mechanical systems (MEMS) to nanoparticles found in environmental sensors, the motion of dislocations that cause plasticity is the same but the scale at which they are confined and their behavior changes dramatically. By employing nanoindentation techniques one can study the deformation of nanostructures. Mechanical properties such as hardness, elastic modulus, and yield strength can be determined for thin films and nanostructures as well as bulk materials. It is the aim of this study to first examine how plasticity is affected by the loading of an indenter, either quasi-statically or dynamically, into single crystals. Single crystals are utilized because they are essentially defect free due to the absence of grain boundaries. Large excursions, or pop-in events, found in the load-displacement curve of nanoindentation experiments indicate the initiation and motion of dislocations. The occurrence of excursions leads to an important length scale parameter, the dislocation wall spacing and the calculation of the activation volume required for dislocation motion under a nanoindenter. The dislocation wall spacing and activation volume knowledge can lead to a fundamental equation of state to describe plasticity. From an engineering standpoint, strength, friction, and wear are dominant factors in the performance and reliability of nickel based nanoscale devices. However, the effects of frictional contacts and wear on device performance are undefined. To address these effects on a fundamental level, a program using nanoscratch and nanoindentation to study wear on (001), (110) and (111) oriented single crystal nickel was conducted. Nanoscratch techniques were used to generate wear patterns as a function of load and number of cycles and nanoindentation was used to measure properties in each wear pattern. AFM, EBSD and TEM revealed a parallel change in microstructure with increasing applied load and number of wear cycles, from a dislocation cell structure to subsurface structure of randomly oriented nanocrystalline grains. |
