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Completed Project

Identification of Vibrational Modes in Thin Film TiN Structures Using Non-Destructive Pump-Probe Laser Technique

Sushant Mahat, Vassar College ’16, Aine Connolly, Vassar College ’17 and Prof. Brian Daly

Thin film materials are the foundation of how nanoscale devices, such as microprocessors found in computers and phones, are constructed. Understanding the underlying physics of these materials plays a vital role in making them faster, smaller and more reliable. Our experiment deals with measuring the precise acoustic and thermal properties of these thin-film materials. The structures tested consist of three layers grown on a silicon wafer: TiN wires, a layer of a very soft, so called “ultra-low k” material, and a layer of silicon dioxide. The samples vary in number of TiN wires per unit length, and we sought to identify the effect of the density of the wires upon the vibrations transmitted through the sample. A non-destructive pump-probe laser technique, repeated using three separate laser orientations, was used to measure the change in reflectivity of the sample as it heats, vibrates and cools due to the incidence of a laser pulse. As a result of the technique, vibrational modes dependent on the periodicity of the TiN wires were discovered, and results as to the modeling and analysis of these modes will be presented.