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Growth of GaN thin film on the sapphire covered by hexagonal non-closed packed hollow silica particles

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dc.contributor.advisor윤 의 준-
dc.contributor.author김로-
dc.date.accessioned2017-07-14T03:09:35Z-
dc.date.available2017-07-14T03:09:35Z-
dc.date.issued2014-08-
dc.identifier.other000000021779-
dc.identifier.urihttps://hdl.handle.net/10371/123327-
dc.description학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2014. 8. 윤의준.-
dc.description.abstractIn few decades, III-V compound semiconductors have attracted much attention due to theirs excellent optical properties. Especially, because of the suitable band gap of GaN, it is selected and used in the light emitting diode (LED) devices. Comparing with conventional lighting devices, LED devices have many advantages, such as high lighting efficiency, long lifetime of devices, and less heating lighting effect. However, the performance of conventional GaN based LED devices is suffered by high threading dislocation density, low external extraction efficiency and wafer bowing effect.
In order to overcome these problems, a method of growth of GaN thin film on the sapphire covered by hexagonal non-closed packed (HNCP) hollow silica particles was proposed in this study. This method concluded three steps. At first, various sized monodisperse shrinkable PS-silica core-shell beads were synthesized. As-synthesized particles had two important features, one was the shrinkable shell, and another was decomposable core. Second step was patterning. Sapphire substrate coated by monolayer core-shell particles with hexagonal closed packed (HCP) structure was fabricated by spin-coating method. Then after thermal treatment, HCP core-shell particles array was transformed to HNCP hollow silica particles array. The main defects in HNCP silica hollow particle pattern was the connection between particles. Due to connection between neighboring particles, HNCP pattern was not perfect. These connection defects were inevitably formed during thermal treatment with low ramping time. However in the case of thermal treatment with high ramping time, connection between neighboring particles could be avoided. In the end, GaN thin film was grown on patterned substrate by metal organic chemical vapor deposition (MOCVD). Due to high coverage percentage of hollow silica beads mask, existence of bilayer and aggregate particles, and imperfect growth condition, GaN films was not fully coalescent. SEM images show that self-assembly HNCP hollow silica particle pattern was successfully embedded with GaN thin films with ultra-high coverage percentage of hollow silica beads. By using HNCP hollow silica beads coated substrate, XRD FWHM value of (102) plane was reduced from 521.1 to 335.1 arcsec, PL intensity was increased by a factor of 7, the PL peak was shift from 361.8 to 363.5. We concluded that GaN films are grown with higher crystal quality, higher external quantum efficiency and lower stress by inserting HNCP hollow silica beads.
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dc.description.tableofcontentsContents

Abstract i
Contents iv
List of Figures vi
Chapter 1. Introduction 1
Chapter 2. Synthesis of shrinkable core-shell sphere by one-pot method 6
2.1 Introduction 6
2.1.1 Synthesis of polystyrene-MTC copolymer 6
2.1.2 Synthesis of silica shell on the copolymer beads 12
2.2 Experiment and analysis 14
2.2.1 Materials 14
2.2.2 Synthesis of submicron polystyrene spheres 14
2.2.3 Synthesis of micron-sized polystyrene spheres 15
2.2.3 Analysis tools 16
2.3 Results and discussion 19
2.3.1 Synthesis of submicron core-shell spheres 19
2.3.2 Synthesis of micron-sized core-shell spheres 25
2.3.3 Features of as-synthesized particles 25
2.4 Conclusion 35
Chapter 3. Fabrication of hexagonal non-closed packed hollow silica particle on sapphire substrate 36
3.1 Introduction 36
3.2 Experiment and analysis 39
3.2.1 Materials 39
3.2.2 Fabrication of HCP monolayer of core-shell beads by spin-coating 39
3.2.3 Fabrication of HNCP monolayer of hollow silica beads by thermal treatment 40
3.2.4 Analysis tools 40
3.3 Results and discuss 41
3.2.1 Fabrication of HCP monolayer of core-shell beads by spin-coating 41
3.3.3 Fabrication of HNCP monolayer of hollow silica beads by thermal treatment 43
3.4 Conclusion 51
Chapter 4. Growth GaN thin films on patterned sapphire substrate 52
4.1 Introduction 52
4.2 Experiment and analysis 54
4.2.1 MOCVD system 54
4.2.2 Growth procedure 54
4.2.3 Analysis tools 54
4.3 Results and discuss 56
4.4 Conclusion 66
Chapter 5. Conclusion 67
Reference 69
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dc.formatapplication/pdf-
dc.format.extent2523182 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectMetal organic chemical vapor deposition (MOCVD)-
dc.subjectGallium nitride (GaN)-
dc.subjectHexagonal non-closed packing (HNCP)-
dc.subjectShrinkable polystyrene-silica core-shell beads-
dc.subjectHollow silica beads-
dc.subjectSpin coating-
dc.subjectThermal treatment-
dc.subject.ddc620-
dc.titleGrowth of GaN thin film on the sapphire covered by hexagonal non-closed packed hollow silica particles-
dc.typeThesis-
dc.contributor.AlternativeAuthorJin Lu-
dc.description.degreeMaster-
dc.citation.pages81-
dc.contributor.affiliation공과대학 재료공학부-
dc.date.awarded2014-08-
Appears in Collections:
College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Material Science and Engineering (재료공학부) Theses (Master's Degree_재료공학부)
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