Effect of substrate on the characteristics of manganese(IV) oxide thin films prepared by atomic layer deposition

Manganese(IV) oxide exhibits many different crystal structures, and growth of thin films of this compound is expected to experience a guiding effect from the substrate. This effect had been studied by deposition on different kinds of substrates by the atomic layer deposition (ALD) technique. The types of substrates examined are: amorphous substrates such as soda-lime-glass, Si(100) with a native SiOx surface layer, and an organic KaptonTM-foil substrate; single-crystal substrates of oxides [α-SiO2(001), α-Al2O3(012), α-Al2O3(001), muscovite(001), and MgO(100)]; and single crystal alkali-metal halide substrates [NaCl(100), KCl(100), KBr(100), and KI(100)] that may contribute with potential dopant elements to the film in the early growth stages. The films were made using Mn(thd)3 (Hthd=2,2,6,6-tetramethylheptane-3,5-dione) and ozone as precursors. Four different phases of MnO2 are prepared: α-MnO2 (cryptomelane Q) [obtained on NaCl(100), KCl(100), and KBr(100) substrates], β-MnO2 (pyrolusite) [obtained on α-Al2O3(012), muscovite(001), α-SiO2(001), and MgO(100) substrates], mixtures of β-MnO2 and β'-MnO2 [obtained on soda-lime-glass and Si(100) substrates], and ε-MnO2 (akhtenskite) [obtained on α-Al2O3(001)]. The coherence between these phases and the substrates is discussed