Alucone Alloys with Tunable Properties Using Alucone Molecular Layer Deposition and Al₂O₃ Atomic Layer Deposition

Abstract

Ultrathin and conformal hybrid organic–inorganic thin films can be deposited by molecular layer deposition (MLD) techniques. By combining the hybrid organic–inorganic MLD process with an inorganic atomic layer deposition (ALD) process, ALD/MLD alloy films can be deposited that have an adjustable organic–inorganic composition. These alloys have tunable properties that may be useful for designing various functional films. In this study, alucone MLD using trimethylaluminum (TMA) and ethylene glycol (EG) was employed together with Al2O3 ALD using TMA and H2O to deposit alucone alloys at 135 °C. The surface species and film growth were examined using in situ Fourier transform infrared spectroscopy. The mass gain for each reactant exposure during film growth was also monitored using an in situ quartz crystal microbalance (QCM) in a viscous flow reactor. The composition of the alucone alloy was varied by adjusting the relative number of ALD and MLD cycles in the reaction sequence. Alucone alloys were grown using relative numbers of ALD and MLD cycles varying from 1:3 to 6:1 (TMA/H2O:TMA/EG). These alucone alloys displayed varying density, refractive index, elastic modulus, and hardness. The density and refractive index changed from 1.6 g/cm3 and n = 1.45 for pure alucone to 3.0 g/cm3 and n = 1.64 for pure Al2O3, respectively. The elastic modulus and hardness varied from 21 ± 8 GPa and 1.0 ± 0.1 GPa for pure alucone to 198 ± 8 GPa and 13.0 ± 0.2 GPa for pure Al2O3, respectively. These results demonstrate the potential of ALD/MLD alloy films to provide tunable properties for many functional film applications.

History of atomic layer deposition and its relationship with the American Vacuum Society

“…36 Combining ALD and MLD can also produce organic-inorganic alloys or nanolaminates, where the properties are tunable between pure inorganic and organic-inorganic. 37,38 The number of materials is nearly endless considering the metals and types of organic linkages available.…”

Tunable optical properties of hybrid inorganic–organic [(TiO2)m(Ti–O–C6H4–O–)k]n superlattice thin films

“…12,13 Most interestingly, use of metal precursors together with organic precursors enables hybrid inorganic-organic thin films to be fabricated with combined ALD/MLD processes, 14,15 where the organic precursors can be, e.g., organic alcohols 14,16 or carboxylic acids. 17,18 Such combined ALD/MLD processes also allow for fabrication of hybrid inorganic-organic materials in the form of nanolaminates [19][20][21] and superlattices [22][23][24] in an elegant manner.…”

Hybrid inorganic–organic superlattice structures with atomic layer deposition/molecular layer deposition

“…There are a growing number of reports on various hybrid thin films fabricated with ALD/MLD, [6][7][8][9][10][11][12][13][14][15][16] but the focus has primarily been on homogeneous 1:1 inorganic-organic hybrid materials where single layers of the organic constituent alternate with single layers of the inorganic part, and then also on so-called nanolaminate structures built up of considerably thicker layers of the two constituents. Despite the potential usefulness of superlattices consisting of very thin layers of one material between thicker layers of another, there are very few reports of the fabrication of hybrid superlattices using ALD/MLD.…”