Antony George

Ph.D. thesis

Summary

This PhD thesis addresses two major issues:
1) Fabricating nanometer-scale patterns of functional materials,
2) Extending the applicability of soft lithographic processes to a wide range of functional materials on conventional silicon substrates and flexible plastic substrates.
This thesis describes novel soft lithographic processes, with which it is possible to fabricate sub-50 nanometer to micrometer length scale patterns of a wide range of functional materials, including metals, nanoparticles, organosilane molecules, nanowires, semiconducting materials and conducting polymers on silicon and flexible plastic substrates.
Chapter 2 describes the patterning of oxide materials in sub-50 nm scale to micrometer scale using transfer printing metal loaded water soluble polymers. The process is a simple and low cost approach to pattern a wide range of oxide materials on the sub -100 nanometer scale that have potential applications in the fabrication of device structures.
Chapter 3 introduces a method to pattern organosilane molecules on silicon substrates on the nanometer and micrometer scale. The process is a time-controlled approach which uses the phenomena of geometry dominated condensation of organosilane molecules from a vapor phase to generate high-resolution patterns. PDMS stamps of large dimensions can be used to fabricate patterns of much smaller dimensions.
Chapter 4 extends the application possibility of the process described in the previous chapter to pattern inorganic functional materials on the nanometer to micrometer scale. The chapter shows that the gas phase pattern deposition of organosilane molecules is fully controllable. Also self-assembled molecular thin films of mercaptosilane molecules were used as thin resists for the electrodeposition of metallic and semiconducting materials.
Chapter 5 further extends the application range of the process described in chapter 3. Sequential deposition of different organosilane molecules on silicon substrate is used to fabricate substrates with multiple chemical functionalities. Multifunctional multi-length scale surfaces have been realized on the micrometer and nanometer scale. The potential application of organosilane patterns as resists for atomic layer deposition (ALD) and as template for site-selective adsorption of nanoparticles has been demonstrated.
Chapter 6 describes a novel process to pattern octadecanethiol (ODT) SAMs on gold substrate by channel diffused plasma etching. The patterned SAMs were used as templates for electrodeposition, electroless deposition and solution phase deposition of a wide range of functional materials (Ni, Ag, ZnO, and ZnO nanowires) on the nanometer and micrometer scale.
Chapter 7 describes the potential application of channel diffused plasma surface modification of plastic substrates like polycarbonate (PC), PDMS and polyethylene terephthalate (PET) to create a hydrophilic-hydrophobic contrast on these surfaces. After surface modification, subsequent material deposition processes such as electroless deposition, solution phase deposition, site selective de-wetting and site selective adsorption were used to obtain patterns of functional materials such as ZnO, ZnO nanowires, Ag , TiO2, conducting polymer (PEDOT:PSS) and Ag nanoparticles
Chapter 8 describes a novel process of electrodeposition in capillaries. The process enables bottomup micro and nano patterning of metallic and semiconducting materials by electrodeposition of an electrolyte solution inside PDMS capillaries in contact with a substrate.
The thesis closes with conclusions and outlook in chapter 9.