Methylmagnesium isopropoxide MgMe(OiPr) has been applied as the precursor for the vapor phase epitaxy (VPE) of MgO on Si(001) and Si(111) substrates in the temperature range 400-850 °C under high vacuum conditions. Stainless-steel ultrahigh vacuum (UHV) chamber with base pressure of the deposition chamber was below 1x10-8 Torr, chamber pressures increased to 3-5x10-6 Torr after introduction of precursors. Evaporation temperature of MgMe(OiPr) was 100°C to get reasonable vapor pressure. The films were characterized by RHEED in situ in the growth chamber, XRD, x-ray pole figure analysis, SEM, XPS after the growth. Epitaxial growth of MgO on Si(111) was achieved by raising the substrate temperature, however, on Si(001) a SiC buffer layer prior to the deposition of MgO was necessary. Growth temperatures of 700-850°C were necessary for the epitaxial MgO growth in the [100] direction; when the growth temperature was lowered below 600 °C, in the RHEED patterns ring structures appeared indicating polycrystalline films [177]
Methylmagnesium tert-butoxide is sufficiently volatile to be applied as an MOCVD precursor, despite of its tetrameric solid-state structure [MgMe(OtBu)]4. [4][177]
Methylmagnesium tert-butoxide, unlike most of other Mg precursors, does not require an additional oxygen source such as H2O or O2 for MgO deposition (and can be therefore used as a single source precursor for MgO).[179]
MgMe(OtBu) was successfully applied for the growth of MgO films by MOCVD on Si (100) and GaAs substrates, at growth temperature Tdep 350-600°C in the absence of carrier gas, keeping source temperature 80°C and pressure 50-200 mPa (0.38-1.5 mTorr), depos. time several hours.
During evaporation, MgMe(OtBu) had to be heated at 140 °C to give a reasonable vapor pressure, whereas MgMe(OiPr) should be heated at 100 °C, what according to the authors indicates that the two precursors have the same degree of association in the gas phase. The mass spectrum (by quadrupole mass analyzer attached to the UHV chamber) indicated that precursor was pyrolyzed by β-hydrogen elimination between the methyl group and the tert-butyl group. [177]
XPS and Auger spectra of MgO grown with [MgMe(OtBu)]4 showed that C peak is smaller than in MgO films obtained using Mg(thd)2. MgO grown on Si(100) is polycrystalline with some preferential 100 orientation, according to XRD. Films deposited on Si(111) at 500°C and on GaAs(100) at 350°C were less oriented polycrystalline. All films had rough surfaces by SEM; well-shaped facets of cubics MgO we observed on the films grown at 500°C (facets less well shaped at Tdep 350°C) [178]
MgMe(OtBu) was synthesized and characterized by spectroscopic methods and single-crystal X-ray diffraction analysis. Methylmagnesium tert-butoxide MgMe(OtBu) has been applied as single-source precursor for the growth of MgO films by chemical beam deposition on Si(111) and Si(100) substrates at 400−800 °C under high-vacuum conditions (5×10-6 Torr). Layer crystalline structure, chemical composition, and morphology of the deposited films was studied by XPS, XRD, and SEM. Epitaxial MgO films with correct stoichiometry were grown on Si(111) at 800 °C, whereas on Si(100) at 800 °C highly [100] oriented MgO films were obtained. Thermal desorption studies indicate that the precursor is decomposed into isobutene and methane via β-hydrogen elimination. [[i]]
[i] Myung M. Sung, Chang G. Kim, Jinkwon Kim, Yunsoo Kim, Chem. Mater., 2002, 14 (2), pp 826–831, DOI: 10.1021/cm010683x , “Chemical Beam Deposition of MgO Films on Si Substrates Using Methylmagnesium tert-Butoxide”