NSF Award
2403534
With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Prof. Francisco Zaera of the University of California, Riverside, will explore ways to improve the quality of thin metal films grown on solid surfaces by using atomic layer deposition (ALD). ALD has gained prominence in microelectronics fabrication, catalysis, and the design of energy-related devices such as batteries and supercapacitors due to the high film quality and conformality at a sub-nanometer scale, despite of surface roughness and complexity. However, one key challenge remains when growing metal films because metal atoms sinter into 3D nanoparticles (NPs). Prof. Zaera addresses this challenge via pre-conditioning of the surfaces to produce smoother and better-quality metal films. The knowledge gained shall benefit aforementioned applications, and serve educational purposes by illustrating basic principles in kinetics, catalysis, film deposition, and NP synthesis in undergraduate and graduate classes. Collaborations with Latin American research groups will be forged, and student participation from groups underrepresented in research, Hispanics in particular, will be strongly pursued.<br/><br/>The main hypothesis underpinning this project is that control of the structure of the metals deposited on solids by ALD can be achieved via appropriate preconditioning of the surface of the underlying substrates. It should be possible to tune the size and surface density of ALD-grown metal NPs by adjusting the surface density and nature of the ALD nucleation sites: a high density should lead to the rapid coalescence of the developing metal NPs in the early stages of the ALD into 2D films and, conversely, a low density should allow for the NPs to grow in size before coalescing. Zaera's objective will be to study the molecular level chemistry that can afford such control, in particular the use of surface preconditioning as a way to define the characteristics of the metal NPs grown by ALD. Three approaches will be tested: (1) the increase of the density of silanol surface groups to act as nucleation sites; (2) the silylation of the substrate to partially block its nucleation sites; and (3) the derivatization of the nucleation sites to modify the surface chemistry of the metal ALD. Mechanistic studies will be carried out with model flat substrates and controlled ultrahigh vacuum (UHV) environments, relying on a combination of surface-sensitive techniques, including x-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), low-energy ion scattering (LEIS), secondary ion mass spectrometry (SIMS), and Fourier-transform infrared spectroscopy (FTIR). Studies of the preconditioning of the surface will be correlated with subsequent metal ALD tests.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
