Growth of La1−xCaxMnO3 thin films by atomic layer deposition

Abstract

Thin films of calcium substituted lanthanum manganite (La_1−xCa_xMnO₃) have been synthesised by the ALD (atomic layer deposition) technique using Mn(thd)₃ (Hthd = 2,2,6,6-tetramethylhepta-3,5-dione), La(thd)₃, Ca(thd)₂, and ozone as precursors. The effect of each of these precursors on the product stoichiometry has been investigated, and ALD type growth was achieved in the temperature range 200–330 °C. A concept on precursor surface area coverage has been applied in order to describe the difference between pulsed and obtained cation stoichiometry. The La_1−xCa_xMnO₃ films are low in carbonate impurities although Ca(thd)₂ and ozone alone as precursors would give CaCO₃. Mn(thd)₃ can be used as a precursor for ALD growth of these oxides for temperatures up to 330 °C when codeposited along with Ca and La, whereas 240 °C is the upper usable temperature for Mn(thd)₃ when Mn is deposited alone. Films have been deposited on substrates of (amorphous) soda-lime glass and single crystals of Si(100), MgO(100), SrTiO₃(100), and LaAlO₃(100). Growth with a cube-on-cube epitaxy has been achieved for SrTiO₃(100) and LaAlO₃(100) substrates. Magnetoresistive properties are recorded for films with a composition close to La_0.7Ca_0.3MnO₃.