Synthesis and Characterization of Chemically Etched Nanostructured Silicon

Handle URI:
http://hdl.handle.net/10754/222131
Title:
Synthesis and Characterization of Chemically Etched Nanostructured Silicon
Authors:
Mughal, Asad Jahangir
Abstract:
Silicon is an essential element in today’s modern world. Nanostructured Si is a more recently studied variant, which has currently garnered much attention. When its spatial dimensions are confined below a certain limit, its optical properties change dramatically. It transforms from an indirect bandgap material that does not absorb or emit light efficiently into one which can emit visible light at room temperatures. Although much work has been conducted in understanding the properties of nanostructured Si, in particular porous Si surfaces, a clear understanding of the origin of photoluminescence has not yet been produced. Typical synthesis approaches used to produce nanostructured Si, in particular porous Si and nanocrystalline Si have involved complex preparations used at high temperatures, pressures, or currents. The purpose of this thesis is to develop an easier synthesis approach to produce nanostructured Si as well as arrive at a clearer understanding of the origin of photoluminescence in these systems. We used a simple chemical etching technique followed by sonication to produce nanostructured Si suspensions. The etching process involved producing pores on the surface of a Si substrate in a solution containing hydrofluoric acid and an oxidant. Nanocrystalline Si as well as nanoscale amorphous porous Si suspensions were successfully synthesized using this process. We probed into the phase, composition, and origin of photoluminescence in these materials, through the use of several characterization techniques. TEM and SEM were used to determine morphology and phase. FT-IR and XPS were employed to study chemical compositions, and steady state and time resolved optical spectroscopy techniques were applied to resolve their photoluminescent properties. Our work has revealed that the type of oxidant utilized during etching had a significant impact on the final product. When using nitric acid as the oxidant, we formed nanocrystalline Si suspensions composed of particles with a crystal structure different than the common polymorph of Si. These particles emitted UV to blue wavelengths. Iron(III) chloride was also employed as an oxidant, and it created amorphous Si nanostructures from a bulk crystalline Si source. These suspensions showed ultra-bright visible photoluminescence, which could be tuned through engineering the surface.
Advisors:
Chaieb, Saharoui ( 0000-0002-8053-3610 )
Committee Member:
Bakr, Osman M.; Ooi, Boon S. ( 0000-0001-9606-5578 )
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Mechanical Engineering
Issue Date:
May-2012
Type:
Thesis
Appears in Collections:
Theses; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.advisorChaieb, Saharouien
dc.contributor.authorMughal, Asad Jahangiren
dc.date.accessioned2012-05-07T12:05:56Zen
dc.date.available2012-05-07T12:05:56Zen
dc.date.issued2012-05en
dc.identifier.urihttp://hdl.handle.net/10754/222131en
dc.description.abstractSilicon is an essential element in today’s modern world. Nanostructured Si is a more recently studied variant, which has currently garnered much attention. When its spatial dimensions are confined below a certain limit, its optical properties change dramatically. It transforms from an indirect bandgap material that does not absorb or emit light efficiently into one which can emit visible light at room temperatures. Although much work has been conducted in understanding the properties of nanostructured Si, in particular porous Si surfaces, a clear understanding of the origin of photoluminescence has not yet been produced. Typical synthesis approaches used to produce nanostructured Si, in particular porous Si and nanocrystalline Si have involved complex preparations used at high temperatures, pressures, or currents. The purpose of this thesis is to develop an easier synthesis approach to produce nanostructured Si as well as arrive at a clearer understanding of the origin of photoluminescence in these systems. We used a simple chemical etching technique followed by sonication to produce nanostructured Si suspensions. The etching process involved producing pores on the surface of a Si substrate in a solution containing hydrofluoric acid and an oxidant. Nanocrystalline Si as well as nanoscale amorphous porous Si suspensions were successfully synthesized using this process. We probed into the phase, composition, and origin of photoluminescence in these materials, through the use of several characterization techniques. TEM and SEM were used to determine morphology and phase. FT-IR and XPS were employed to study chemical compositions, and steady state and time resolved optical spectroscopy techniques were applied to resolve their photoluminescent properties. Our work has revealed that the type of oxidant utilized during etching had a significant impact on the final product. When using nitric acid as the oxidant, we formed nanocrystalline Si suspensions composed of particles with a crystal structure different than the common polymorph of Si. These particles emitted UV to blue wavelengths. Iron(III) chloride was also employed as an oxidant, and it created amorphous Si nanostructures from a bulk crystalline Si source. These suspensions showed ultra-bright visible photoluminescence, which could be tuned through engineering the surface.en
dc.language.isoenen
dc.subjectSiliconen
dc.subjectnanostructuresen
dc.subjectporousen
dc.subjectamorphousen
dc.subjectphotoluminescenceen
dc.subjectetchingen
dc.titleSynthesis and Characterization of Chemically Etched Nanostructured Siliconen
dc.typeThesisen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberBakr, Osman M.en
dc.contributor.committeememberOoi, Boon S.en
thesis.degree.disciplineMechanical Engineeringen
thesis.degree.nameMaster of Scienceen
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