Thin Film Technology
Our group works primarily with thin films. Two techniques used for deposition are Pulsed Laser Deposition (in the Ross group) and sputter deposition (right).
Our machine is a magnetron sputterer that allows for RF and DC deposition from both metallic and ceramic targets. Three sputtering guns allow for creation of multilayers and composite thin films
We frequently used lithographically-defined micro- electrodes to characterize our thin films electrically. Seen right is a custom-designed microprobe station with a 2” heater capable of reaching 1200 C.
This probe station is enclosed, allowing for measurements in vacuum or controlled atmosphere conditions. Four micromanipulators allow for both DC and AC measurements. This setup also allows for sensor and single chamber fuel cell experiments.
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Instrumentation
Many
of our experiments are used to determine properties as a function of
atmosphere. Seen left is a triple zone furnace capable of four-point
conductivity measurements on 12 different samples at once.
This setup is equipped with a homemade electrochemical zirconia pump. This pump, combined with current control algorithms on Labview, allow for precise control of intermediate pO2 values that are often difficult to stabilize
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Bulk Ceramic Characterization
Thermal expansion is a well known phenomenon, but have you heard of chemical expansion? Chemical expansion occurs when, for example, cerium oxide releases oxygen upon heating to high temperatures in low oxygen pressure, creating defects that cause the material to dilate without a phase change. Using a dilatometer, we can vary the temperature and oxygen pressure and measure the resulting expansion to deconvolute the thermal from the chemical effects.
Many oxide materials can release and take-in oxygen, like breathing, at high temperature with changes in oxygen pressure without changing structure. This oxygen non-stoichiometry can be measured as a change in mass of the sample using a thermo-gravimetric analyzer (TGA) such as the Cahn 1000. In this setup, mass changes of tens of micrograms to hundreds of milligrams are recorded.