Date of Publication

12-2018

Document Type

Master's Thesis

Degree Name

Master of Science in Physics

Subject Categories

Physics

College

College of Science

Department/Unit

Physics

Thesis Adviser

Gil Nonato C. Santos

Defense Panel Chair

Emmanuel T. Rodulfo

Defense Panel Member

Christopher T. Que
Elmer S. Estacio

Abstract/Summary

The synthesis of functional metal oxide nanomaterial has been widely studied due to its extensive potential especially in gas sensing. Gallium Oxide (Ga2O3), a wide band-gap metal oxide with high stability and has long been known to exhibit conductive property, has been used as bulk material for monoclinic Gallium Oxide nanoparticle synthesis.

This study was conducted to synthesize Gallium Oxide nanomaterials from its bulk form using a low-cost and repeatable method and investigate on its potential as sensing element for Ethanol (EtOH). Horizontal Vapor Phase Growth (HVPG) Technique, patented by Santos, et al., with the application of magnetic field (AMF) was utilized to synthesize monoclinic Gallium Oxide (β- Ga2O3) nanowires. Images of the synthesized nanomaterials obtained using a Scanning Electron Microscope showed high density nanowires on the region closest to the highest temperature gradient as well as where the magnetic field was applied. Higher surface-to-volume ratio was also noted in this particular area. SEM micrographs also showed that the grown nanostructures using HVPG Technique were at the nanoscale with diameters ranging from 51.60 to 908.38 nm. The Gallium to Oxygen ratio was verified to be approximately 2:3 using Energy Dispersive X-ray which agrees with the atomic ratio of Ga2O3. Traces of Gold and Silicon were also detected in the sample which was attributed to the substrate used in the synthesis and the sample preparation for SEM analysis. The monoclinic structure of the grown nanomaterials was investigated using Raman Spectroscopy. Raman peaks of the samples were at 199 and 486 cm-1 which agrees with the Raman peaks for β-Ga2O3 from cited literatures. The Raman spectrum of the grown nanowires confirmed that the material is monoclinic in structure and belongs to the C2/m space group. This indicates that the grown nanomaterial is a β-polytype. The I-V Curve of the grown nanowires were also determined using a two-point probe which illustrates a non-linear curve similar to that of a semiconductor material. Furthermore, additional fundamental properties such as resistivity and specific conductance of the materials were also determined via van der Pauw Technique. Results showed that the material has high specific conductance and low resistivity.

The synthesized material was responsive to Ethanol vapor. Exposure to the said compound increases the resistance of the material. Graphs showed that there is a significant difference in the response time between higher concentration and lower concentration of Ethanol solution. Overall, the material showed potential for use in gas sensing and gas detection.

Abstract Format

html

Accession Number

CDTG007370

Keywords

Nanostructured materials; Gallium; Oxides; Gas detectors; Gas chromatography

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Embargo Period

9-5-2022

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