Deposition of MnO Anode and MnO₂ Cathode Thin Films by Plasma Enhanced Atomic Layer Deposition Using the Mn(thd)₃ Precursor

Atomic layer deposition (ALD) of a wide range of Mn oxides (MnO to MnO 2 ) is demonstrated by combining the Mn(thd) 3 (tris(2,2,6,6-tetramethyl-3,5-heptanedionato)manganese) precursor with different types of plasma activated reactant gases. Typical ALD behavior is found with hydrogen, ammonia, and water plasma, with a fully precursor controlled temperature window (from 140 to 250 °C) and constant growth rate (0.022 ± 0.001 nm/cycle). A purely ligand-exchange chemistry would predict Mn 2 O 3 films with the transition metal in the +III state. However, it is found that the nature of the processgas or -plasma, more specific its oxidizing/reducing character, largely determines the oxidation state of the grown films. Our approach provides an effective method for the deposition of MnO 2 (+IV), Mn 3 O 4 (+II/+III), and MnO(+II) based on the Mn(thd) 3 (+III) precursor. All as-deposited films are found to be smooth (<1.2 nm rms roughness), crystalline and with <6% impurities. The resulting films are tested as lithium-ion battery electrodes, showing the MnO 2 and the MnO films as possible candidate thin-film cathode and anode, respectively.