Graduation Semester and Year
2016
Language
English
Document Type
Thesis
Degree Name
Master of Science in Materials Science and Engineering
Department
Materials Science and Engineering
First Advisor
Jin Seong Koh
Abstract
Nanopillars exhibit novel electrical and optical properties which could not be obtained from bulk materials. Many of their practical applications would require controlled placement of nanopillars at exact locations. However, precise placement and large scale fabrication of nanopillars have been challenging with conventional fabrication techniques. This thesis investigates a new approach to fabricate nanopillars at exact locations on a large scale. In this approach, fabrication of nanopillars is accomplished by first placing nanoparticles (NP) at exact locations and then performing anisotropic dry etching using these NPs as hard masks, resulting in formation of nanopillars on exact substrate positions. Precise placement of nanoparticles was carried out by forming an electrostatic guiding template that forces nanoparticles onto site specific locations on the substrate. The electrostatic guiding template was made of a gold layer on SiO2 substrate in which 100nm circular holes are made with underlying SiO2 substrate exposed. The gold substrate surface and exposed SiO2 surface were functionalized with self-assembled monolayers of 16-mercaptohexadecanoic acid (MHA) and 3-aminopropyltriethoxysilane (APTES), producing negatively and positively charged surfaces, respectively. DNA-functionalized Au nanoparticles (negatively charged due to DNA) were used for the nanoparticle hard masks. Guiding of the DNA-functionalized Au nanoparticles to a specific location was conducted by using the electrostatic funneling technique, where the SAMs-functionalized template guided the Au nanoparticles onto center positions of the circular holes. Placement of exactly one single Au nanoparticle at the center of the circular SiO2 exposed area was achieved using self-limiting electrostatic gating, which was controlled by varying ionic and pH concentration of the solution during attachment. Subsequently, with the precise placement of Au nanoparticles, a selective removal of Au deposited layer was carried out, leaving the single Au nanoparticles at specified positions on the SiO2 substrate. Then, using AuNP as a hard mask SiO2 layer was anisotropically etched to form SiO2 nanopillars. Using these SiO2 pillars as etch masks, Si substrate was subsequently etched anisotropically. With the above process, the resultant nanopillars had the lengths of 100 nm and diameter of 30 nm at desired locations. These controlled placements of nanopillars could be potentially used in electrical/ optical devices and chemical/biological sensors.
Keywords
Synthesis and processing, Reactive ion etching, Self-assembly
Disciplines
Engineering | Materials Science and Engineering
License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Recommended Citation
Talasila, Sravan Chowdary, "A NOVEL APPROACH FOR FABRICATION OF SINGLE SILICON/SILICON OXIDE NANOPILLARS AT PRECISE LOCATIONS" (2016). Material Science and Engineering Theses. 141.
https://mavmatrix.uta.edu/materialscieng_theses/141
Comments
Degree granted by The University of Texas at Arlington