Graduation Term

Fall 2025

Degree Name

Master of Science (MS)

Department

Department of Chemistry

Committee Chair

Mahua Biswas

Committee Member

Jun-Hyun Kim

Committee Member

Uttam Manna

Abstract

Technological advancements are pushing towards the use of material patterns with dimensions below 50 nm. Nanomaterials are promising for emerging technologies that were once unimaginable and their distinctive attributes, rooted in their minute size and expansive surface area, have unlocked enhanced optical, electrical, and mechanical properties. The patterning of organic-inorganic materials has multifaceted applications spanning electronics, optics, photonics, energy, and biomedical engineering. There also has been a growing demand for nanomaterials in biocompatible applications and green technologies. Conventional nanofabrication methods are facing challenges such as size limitations, substrate flexibility, slow processing speeds, and high costs. Sequential infiltration synthesis (SIS) offers an alternative to conventional nanofabrication and patterning techniques. It presents an effective approach for the controlled and precise fabrication of patterned nanoscale structures by selectively infiltrating inorganic oxides in vapor form into polymers with interactive functional groups. Self-assembled block copolymer (BCP) nanostructures, such as polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA), have been widely used as templates for nanopatterning oxide materials through the SIS process. However, biocompatible polymers have not been explored in this context. My work focuses on the synthesis of two distinct nanomaterials: aluminum oxide (Al2O3) and aluminum nitride (AlN) that are essential for their wide-ranging applications in power electronics, optoelectronics, and semiconductor industry. Patterned polymeric substrates like block copolymers (BCPs) can serve as a guiding matrix enabling selective infiltration for well-ordered and large-scale deposition of materials in the nanoscale, consequently, allows precise control over the size, shape, and composition of nanostructured materials, including metal oxides, nitrides, and hybrid materials.

This thesis focuses on the fabrication of two distinct nanomaterials that are essential for their wide-ranging applications in power electronics, optoelectronics, and semiconductor industry. First, we utilized polystyrene-block-poly(ε-caprolactone) (PS-b-PCL) BCP as a template for SIS to create Al2O3 nanostructure patterns. PCL, which contains active functional groups, is a biocompatible and biodegradable polymer. PS-b-PCL has not been previously explored for any vapor deposition-based nanofabrication and nanopatterning processes. Scanning electron microscopy (SEM) images of the patterned Al2O3 nanostructures fabricated using a PS-b-PCL template are presented, with SIS experiments conducted at different temperatures and with multiple SIS cycles. Significant Al2O3 deposition was observed during the first SIS cycle, which is beneficial for cost-effective and precise fabrication. The deposited materials were characterized using Energy-Dispersive X-ray Spectroscopy (EDS) and Fourier Transform Infrared Spectroscopy (FTIR). Due to the effective interactions and substantial deposition in the first SIS cycle, PCL emerges as a promising guiding polymer for uniform and cost-effective nanofabrication and patterning processes, particularly for applications in bio-related fields. In our second study, we utilized polystyrene-block-poly(methyl methacrylate) (PS-b PMMA) as a template for SIS for AlN nanostructure patterns. We wanted to fabricate low-dimensional Group III nitride nanostructures that have the possibility of becoming suitable for the next-generation technologies for enhanced device performance. We reported for the first time that the low-temperature (150 °C and less) formation of nanostructured Al–N via SIS process using trimethylaluminum (TMA) and ammonia (NH₃) precursors. Self-assembled PS-b-PMMA block copolymer templates enabled selective Al–N infiltration within PMMA domains, producing sub-20 nm features. Comprehensive characterization (SEM, EDS, FTIR) confirmed successful pattern transfer and revealed key mechanistic insights and process limitations of nitride SIS. To investigate the optical response of the AlN nanopatterns, UV–Visible spectroscopy was employed to measure the absorption characteristics. This work establishes a new route for bottom-up nitride nanofabrication using soft polymer templates, offering opportunities for device integration on temperature-sensitive substrates and scalable, cost-efficient nanoscale manufacturing.

Access Type

Thesis-Open Access

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