Molecular Layer Deposition of Hybrid Organic−Inorganic Alucone Polymer Films Using a Three-Step ABC Reaction Sequence

Abstract

Thin film growth using molecular layer deposition (MLD) or atomic layer deposition (ALD) is based on sequential, self-limiting surface reactions. In this work, MLD is used to grow a hybrid organic−inorganic polymer film based on a three-step ABC reaction sequence using trimethylaluminum (TMA), ethanolamine (EA), and maleic anhydride (MA) as the reactants. This three-step ABC sequence avoids the use of homobifunctional organic precursors by employing a homotrifunctional inorganic reactant (TMA), a heterobifunctional organic reactant (EA), and a ring-opening organic reactant (MA). The resulting hybrid organic−inorganic polymer film is an alucone with an approximate formula of (−AlCH3−OCH2CH2NH−C(O)CHCHCOO−)n. The growth of this ABC alucone film was monitored using in situ Fourier transform infrared (FTIR) measurements at 90−170 °C. The three sequential surface reactions displayed self-limiting growth. The FTIR difference spectra monitored the absorbance from the surface species during the three surface reactions. The gain and loss of absorbance helped to determine the reaction mechanism for the ABC alucone film growth. Transmission electron microscope (TEM) measurements on ZrO2 nanoparticles also displayed the growth of very conformal ABC alucone films. The ABC alucone growth per cycle was also measured on Si wafers using X-ray reflectivity. ABC alucone growth rates were temperature dependent and varied from 24 Å per cycle at 90 °C to 4.0 Å per cycle at 170 °C. X-ray photoelectron spectroscopy also determined the composition of the ABC alucone films. The robust and efficient growth of the ABC alucone hybrid organic−inorganic films may be useful in applications requiring flexible or sacrificial films.