Low temperature atomic layer deposition of PbO2 for electrochemical applications

A low temperature atomic layer deposition (ALD) process for PbO2 was developed using bis(1-dimethylamino-2-methyl-2-propanolate)lead(II), Pb(DMAMP)(2), and O-3 as the reactants, with a high growth rate of 2.6 & Aring;/cycle. PbO2 readily reduces under low oxygen partial pressures at moderate temperatures making it challenging to deposit ALD PbO2 from Pb2+ precursors. However, thin films deposited with this process showed small crystalline grains of alpha-PbO2 and beta-PbO2, without signs of reduced PbOx phases. The ALD PbO2 thin films show the high electrical conductivity characteristic of bulk PbO2. In situ measurements of ALD PbO2 film conductivity during growth suggest a reaction mechanism by which sub-surface oxygen mobility contributes to the growth of resistive PbO or PbOx during the Pb(DMAMP)(2) surface reaction step, which is only fully oxidized from Pb2+ to Pb4+ during the O-3 reaction step. These films were electrochemically reduced to PbSO4 in H2SO4 and then reoxidized to PbO2, demonstrating their suitability for use as an electrode material for fundamental battery research and other electrochemical applications.