Polytype Semiconductor Nanowires.
- 주제(키워드) polytypic , nanowire , semiconductor , chemical vapor deposition
- 발행기관 고려대학교 대학원
- 지도교수 박정희
- 발행년도 2017
- 학위수여년월 2017. 2
- 학위구분 박사
- 학과 대학원 미세소자공학협동과정
- 원문페이지 138 p
- 실제URI http://www.dcollection.net/handler/korea/000000071817
- 본문언어 영어
- 제출원본 000045897372
초록/요약
Semiconductor alloy nanowires (NWs) have recently attracted considerable attention for applications in optoelectronic nanodevices because of many notable properties, including band gap tunability. Here in this study, we synthesized GaAs1-xPx and Zn3(P1-xAsx)2 NWs with different composition and crystal structures by controlling the growth conditions via chemical vapor deposition. In chapter 1, composition tuned GaAs1-xPx alloy nanowires with two average diameters of 60 and 120 nm. Smaller diameter and higher P content (x) result in shorter periodic superlattice structures. The band gap of the smaller diameter nanowires is larger than that of the larger diameter nanowires by about 90 meV, suggesting that the twinned superlattice structure increases the band gap. In chapter 2, we investigated the mechanical properties of GaP and GaAs NWs on their crystallographic structure using Raman spectroscopy. The polytypic NWs, zinc blende-wurtzite structures were controlled, were bent by the mechanical buckling of PDMS, which transformed the straight NWs into wavy shapes by releasing the pre-strain. Micro-Raman spectra collected for individual NWs showed linear peak broadening/shift versus the bending strain (up to 3.5%). The strain-induced Raman peak change was more significant for the GaP NWs than for the GaAs NWs, as supported by the larger Young’s modulus of GaP than that of GaAs. The GaP [211] NWs exhibited the highest strength, which was probably due to the high-density polytypic structures along the wire axis. Our work provides insight into the mechanical properties of one-dimensional nanostructures by engineering the polytypic structures. In chapter 3, Zn3P2 and Zn3As2 belong to a unique pseudocubic tetragonal system. A first type of synthesized NWs was single-crystalline and grew uniformly along the [110] direction (in a cubic unit cell) over the entire compositional range (0 ≤ x ≤ 1) explored. The use of an indium source enabled the growth of a second type of NWs, with remarkable cubic-hexagonal polytypic twinned superlattice and bicrystalline structures. The growth direction of the Zn3P2 and Zn3As2 NWs was also switched to [111] and [112], respectively. These structural changes are attributable to the Zn-depleted indium catalytic nanoparticles which favor the growth of hexagonal phases. The formation of a solid solution at all compositions allowed the continuous tuning of the band gap (1.0~1.5 eV). Photocurrent measurements were performed on individual NWs by fabricating photodetector devices; the single-crystalline NWs with [110] growth direction exhibit a higher photoconversion efficiency compared to the twinned crystalline NWs with [111] or [112] growth direction.
more목차
Chapter 1. Band Gap Tuning of
Twinned GaAsP Ternary Nanowires
1. Introduction………………………………………………… 10
2. Experiment………………………………………………… 13
3. Results and Discussion………………………………… 14
4. Conclusion………………………………………………… 32
5. References………………………………………………… 33
6. Supporting Information ……………………………………38
Chapter 2. Raman Spectroscopy Probe for
Polytypic GaP and GaAs Nanowires under Bending Strain
1. Introduction………………………………………………… 43
2. Experiment………………………………………………… 46
3. Results and Discussion ………………………………… 48
4. Conclusion………………………………………………… 70
5. References………………………………………………… 71
6. Supporting Information……………………………………75
Chapter 3. Zn3P2−Zn3As2 Solid Solution Nanowires
1. Introduction………………………………………………… 94
2. Experiment ……………………………………………… 96
3. Results and Discussion………………………………… 98
4. Conclusion…………………………………………………119
5. References…………………………………………………121
6. Supporting Information………………………………… 126
