Chen D, Tuller H L. Voltage‐Controlled Nonstoichiometry in Oxide Thin Films: Pr0. 1Ce0. 9O2− δ Case Study[J]. Advanced Functional Materials, 2014, 24(48): 7638-7644.

ABSTRACT

While the properties of functional oxide thin fi lms often depend strongly on oxygen stoichiometry, there have been few means available for its control in a reliable and in situ fashion. This work describes the use of DC bias as a means of systematically controlling the stoichiometry of oxide thin fi lms deposited onto yttria-stabilized zirconia substrates. Impedance spectroscopy is performed on the electrochemical cell Pr 0.1 Ce 0.9 O 2−δ  (PCO) /YSZ/Ag for conditions: T = 550 to 700 °C,  pO2= 10 −4  to 1 atm, and  ΔE= −100  to 100 mV. The DC bias  ΔE  is used to control the effective  pO2  or oxygen activity at the PCO/YSZ interface. The non-stoichiometry ( δ ) of the PCO fi lms is calculated from the measured chemical capacitance ( Cchem ). These  δ  values, when plotted isothermally as a function of effective  pO2 , established, either by the surrounding gas composition alone, or in combination with applied bias, agree well with each other and to predictions based on a previously deter-mined defect model. These results confi rm the suitability of using bias to pre-cisely control  δ  of thin fi lms in an in situ fashion and simultaneously monitor these changes by measurement of  Cchem . Of further interest is the ability to reach effective  pO2 s as high as 280 atm.