Nanomolecularly-Induced Effects on the Synthesis and Properties of Inorganic/Organic Multilayer Nanolaminates

Molecular nanolayers (MNLs) at inorganic thin film interfaces are known to improve chemical stability, stimulate unexpected enhancements, and induce unusual mechanical responses, and electrical and thermal transport behaviors¹. Stacking inorganic nanolayer/MNLs interfaces offers promise to access emergent properties, e.g., via superposition of MNL-induced interface effects². Such hybrid multilayer nanolaminates mimic natural microlayered biocomposites such as nacre and bone, and provide a means to explore³ and exploit nanomolecularly tailored interface effects. Here, we describe the MNL-induced effects on the growth and properties of nanolaminates of metal-oxide/MNL⁴ and metal-nitride/MNL multilayers. Nanolaminates with sharp interfaces were synthesized by sequential low-temperature atomic layer deposition (ALD) to preserve the integrity of the MNLs deposited by single-pulse molecular fluxes. Electron microscopy, X-ray diffraction, and ion beam and electron spectroscopy analyses show that MNLs alter the inorganic nanolayer growth rate, chemical composition, surface roughness, and phase stability. For example, organo-diphosphonate MNLs result in a twofold decrease in titania growth rate, and hydroquinone MNLs result in the conversion of aluminum nitride to aluminum oxide. Atomistic mechanisms underpinning these changes will be discussed relative to the impact of MNL backbone structure and terminal chemistry on film morphology, microstructure, and phase formation. Finally, unusual acoustic damping responses in the multilayer nanolaminates, revealed by femto-second pump-probe spectroscopy, will be described and correlated with the MNL interface chemistry and nanolayer periodicity. Harnessing such MNL-induced effects and understanding their correlations with enhanced/emergent properties is fundamental for designing high-interface-fraction hybrid nanolaminates for applications.<br/><br/>1. G. Ramanath, C. Rowe, G. Sharma, V. Venkataramani, J.G. Alauzun, R. Sundararaman, P. Keblinski, D.G. Sangiovanni, P. Eklund and H. Pedersen: Engineering Inorganic Interfaces Using Molecular Nanolayers. <i>Appl. Phys. Lett.</i> <b>122</b>, 260502 (2023).<br/>2. R. Khadka, G. Ramanath and P. Keblinski: Viscoelastic bandgap in multilayers of inorganic–organic nanolayer interfaces. <i>Sci. Rep.</i> <b>12</b>, 10788 (2022).<br/>3. D.G. Sangiovanni, C. Rowe, G. Sharma, M. Lane, P. Eklund and G. Ramanath: Strain hardening and toughening in metal/molecular nanolayer/metal nanosandwichesMolecularly-induced strain hardening and toughening at metal/molecular nanolayer interfaces. <i>Appl. Phys. Lett.</i> <b>124</b>, 261601 (2024).<br/>4. C. Rowe, A. Kashyap, G. Sharma, N. Goyal, J.G. Alauzun, S.T. Barry, N. Ravishankar, A. Soni, P. Eklund, H. Pedersen and G. Ramanath: Nanomolecularly-induced Effects at Titania/Organo-Diphosphonate Interfaces for Stable Hybrid Multilayers with Emergent Properties. <i>ACS Appl. Nano Mater.</i> <b>7</b>, 11225 (2024).