Enhanced growth rate in atomic layer epitaxy deposition of magnesium oxide thin films

Thin films of MgO were deposited by atomic layer epitaxy (ALE) from bis(cyclopentadienyl)magnesium and water using soda lime glass and Si(100) as substrates. Deposition parameters were studied in the temperature range of 100-400 degrees C. A plateau of surface-controlled growth was observed at 200-300 degrees C with a growth rate of 1.16 Angstrom cycle(-1) on both substrates which is almost a magnitude higher than the ALE growth rate obtained with beta-diketonate-type precursors and ozone or hydrogen peroxide. The growth was studied in more detail at 300 degrees C to confirm the surface-controlled nature of the deposition process. The MgO films obtained were analysed by time-of-flight elastic recoil detection analysis (TOF-ERDA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM) to determine chemical composition, crystallinity and crystallite orientation as well as surface morphology. Films deposited below 200 degrees C were amorphous but above that polycrystalline with (111) dominant orientation on both substrates. According to XPS and TOF-ERDA measurements the films were stoichiometric when deposited at 200-400 degrees C. Impurity levels of 0.1 at% for carbon and 0.5 at% for hydrogen were detected by TOF-ERDA when films were deposited at 300 degrees C. Film roughness was dependent on the deposition temperature. Deposition carried out at 250-350 degrees C produced films with rms values of 8-10 nm whereas the roughness of films deposited above or below this temperature range was 2-4 nm.