AVS 61st International Symposium & Exhibition
    Thin Film Tuesday Sessions
       Session TF+EN+PS-TuA

Paper TF+EN+PS-TuA8
Pseudocapacitive Manganese Oxide Grown by Atomic Layer Deposition

Tuesday, November 11, 2014, 4:40 pm, Room 307

Session: ALD for Energy
Presenter: Matthias Young, University of Colorado, Boulder
Authors: M.J. Young, University of Colorado, Boulder
C.D. Hare, University of Colorado, Boulder
A.S. Cavanagh, University of Colorado, Boulder
C.B. Musgrave, University of Colorado, Boulder
S.M. George, University of Colorado, Boulder
Correspondent: Click to Email
Pseudocapacitive supercapacitors are a class of energy storage materials that are midway between lithium ion batteries and capacitors in terms of both power and energy densities. Manganese oxide is a well-known pseudocapacitive material with particular appeal due to its earth abundance and low cost. In previous work, we have demonstrated that MnO ALD produced using bis(ethylcyclopentadienyl)manganese (Mn(CpEt)2) and water can be electrochemically oxidized to produce pseudocapacitive MnO2 in aqueous electrolytes. However, recent results have shown that the electrochemical oxidation of MnO ALD films results in partial dissolution and delamination. To avoid these problems, we have worked to grow pseudocapacitive MnO2 by ALD that requires no post-processing. We have grown manganese oxide ALD films using ozone as the coreactant with Mn(CpEt)2. We have also used intermediate ozone doses during Mn(CpEt)2 and water exposures during ALD growth. The use of ozone results in more oxidized manganese oxide films. Another issue is that the alpha-MnO2 crystal structure of MnO2 which exhibits high pseudocapacitance contains open channels that are only stable in the presence of cations such as Na+ or K+. Consequently, directing the ALD growth toward alpha-MnO2 pseudocapacitive crystal structures requires the incorporation of an alkali metal into the MnO2 ALD films.