Optical Transmission and Resistivity Measurements
of Pd/Mg Film Hydrides
Corey Griffin '09

Corey by the evaporator

Abstract:

   In this work, we observe the drastic changes that occur simultaneously in optical transmission, sheet resistance, and Hall resistance due to the absorption of gaseous hydrogen in custom made palladium/magnesium bilayer film samples. Initial data showed a factor of 70 increase in both Hall and sheet resistance data, as well as a significant increase in optical transparency. Hydrogen absorption causes charge carrier density to decrease, particularly in magnesium. This results in a transition from electrical conductor to insulator, and is measured quantitatively by the Hall resistance. At the same time, the material visibly changes from opaque to transparent. Our in situ measurement of the three separate quantities during hydrogen cycling is unique among previous testing. The custom film samples were tailored to facilitate the van der Pauw method of resistivity measurement, and the sample holder included permanent magnets to create the required magnetic field, as well as a monochromatic LED and photo detector to measure optical transmittance. This type of system has received attention due to potential applications it has for hydrogen storage and switchable mirror devices.

   For more information, contact Dr. Daniel Koon:

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