국회도서관 서비스 이용에 대한 안내를 해드립니다.
검색결과 (전체 1건)
원문 있는 자료 (1)열기
원문아이콘이 없는 자료는 국회도서관에 방문하여 책자로만 이용이 가능합니다.
목차보기더보기
Title Page
ABSTRACT
Contents
1. Introduction 11
2. Backgrounds 13
2.1. Gallium Arsenide (GaAs) for spintronics 13
2.2. Surface defects in GaAs growth 16
2.2.1. Mound shape defects 16
2.2.2. Triangle shape defects 19
2.3. How to suppress the surface defects? 21
2.3.1. Growth temperature and Ga/As flux ratio 21
2.3.2. Vicinal substrates 24
3. Experimental 26
3.1. Basic concept of molecular beam epitaxy 26
3.2. Epitaxial growth of GaAs(110) 30
3.3. Surface morphology analysis 32
3.4. Microstructure analysis 33
4. Results and Discussion 35
4.1. An effect of a layer thickness on the GaAs(110) layer 35
4.1.1. An observation of surface morphology evolution 35
4.1.2. An observation of the Ga or As agglomeration 42
4.1.3. An observation of underlying crystal defects 43
4.2. An effect of a growth temperature on the GaAs(110) layer 51
5. Conclusions 54
References 56
Fig. 1. Schematic of gallium arsenide structure. 13
Fig. 2. Atomic arrangement of the surfaces (a) GaAs(001) and (b) GaAs(110). 15
Fig. 3. Surface and underlying defects in GaAs(001) called "mound (a)" and "pyramid (b)" respectively. 17
Fig. 4. Schematic of Ehrlich-Schwoebel barrier energy to inhibit downward movement of adatoms. 18
Fig. 5. 5 Reported triangle shaped surface defects (a) and〈112〉directional step edge (b). 20
Fig. 6. AFM image of a 1,000 ㎚ thick GaAs(001) layer grown at a substrate temperature of (a) 280 ℃ and (b) 210 ℃. 22
Fig. 7. Normarski microscopic images (90 ㎛ × 90 ㎛) of the GaAs(110) surface after deposition 1000ML of GaAs at five different growth conditions using As₄.... 23
Fig. 8. Schematic of the islands formation mechanism on the relatively longer terrace of the GaAs surface. 24
Fig. 9. Cross-sectional electron microscopy bright field images of LT-GaAs layers on different substrate types (a) nominal substrate and (b) vicinal substrate. 25
Fig. 10. Schematic of a typical MBE system. 26
Fig. 11. Mechanisms of RHEED intensity oscillations during growth of a monolayer. 28
Fig. 12. 12 Different surface elemental processes occurring in MBE growths. 29
Fig. 13. Schematic of homoepitaxial GaAs(110) growth process and conditions. 31
Fig. 14. Schematic of AFM instrument showing "beam bounce" method of detection using a laser and position sensitive photodiode detector. 32
Fig. 15. Interactions between electrons and material. 33
Fig. 16. Schematic illustration of cross-sectional TEM sampling to be have [110] zone axis using a FIB to investigate the crystal defects in GaAs(110) layer.(이미지참조) 34
Fig. 17. 10 ㎛ × 10 ㎛ AFM images (a)-(e) of GaAs(110) surface depending on different layer thickness (a) 200 ㎚, (b) 300 ㎚, (c) 350 ㎚, (d) 500 ㎚, and (e)... 36
Fig. 18. AFM image of elongated line defects along with [110] on the surface.(이미지참조) 38
Fig. 19. (a) measured roughness data of surface defects by AFM analysis, (b) height, and (c) size (length × width). 40
Fig. 20. 20 Scanning electron microscopy images with different layer thickness (a) 200 ㎚, (b) 300 ㎚, (c) 500 ㎚, and (d) 1,000 ㎚ (Insets are AFM images observed). 41
Fig. 21. Electron probe micro-analyzer results (a) SEM image, (b) Ga distribution, and (c) As distribution. 42
Fig. 22. (a) SEM and (b) cross-sectional TEM images sampled by FIB 44
Fig. 23. Comparison of twin density between (a) out of pyramid region and (b) inner pyramid region. 45
Fig. 24. Cross-sectional TEM image and diffraction patterns of GaAs(110) substrate and homoepitaxial layer in [110] zone axis (a) TEM image, (b) substrate...(이미지참조) 46
Fig. 25. (a) cross-sectional TEM image and diffraction patterns for three different regions (b) region 1 (between long legs), (c) region 2 (out of pyramid), and (d)... 47
Fig. 26. Illustration of stacking fault formation in zinc-blende structure (a) zinc-blende (111) surface, (b) wurtzite(0001) surface, and (c) inserted wurtzite 1... 48
Fig. 27. (a) cross-sectional TEM image and (b) Balls and sticks model of the pyramid defect formation in GaAs(110). 49
Fig. 28. Cross-sectional TEM images and diffraction patterns of long leg (a) TEM image, (b) HRTEM image, (c) FFT image out of long leg, and (d) FFT image of... 50
Fig. 29. 10 ㎛ × 10 ㎛ AFM images (a)-(e) of GaAs(110) surface depending on different growth temperature (a) 360 ℃, (b) 400 ℃ , (c) 420 ℃, (d) 440 ℃, and... 53
초록보기 더보기
The evolution of surface topology and underlying multiple twin defects in homoepitaxial GaAs(110) growths has been investigated with respect to the layer thickness and growth temperature by mainly using a transmission electron microscope and an atomic force microscope. Single triangular-shaped surface defects appear at the layer thickness of 300 nm which is considered as a critical thickness upon the advent of underlying pyramidal defects of stacking faults and twins. With the increase of the layer thickness, the triangular-shaped defects further evolve into paired triangular defects of which individual apexes contact pointing in the [00-1] crystallographic direction on the surface. Additional increase of the layer thickness above 500 nm makes the surface defect shape further change to a dagger with four side edges parallel to〈112〉and〈113〉directions and the more entangled underlying multiple twins. It is also found that the rather higher growth temperature of 420℃ retards the evolution of the defects and significantly reduces the surface defect density because of enhanced Ga migration. Higher temperatures above 420℃, however, lead to surface roughness due to the low As incorporation.
원문구축 및 2018년 이후 자료는 524호에서 직접 열람하십시요.
도서위치안내: / 서가번호:
우편복사 목록담기를 완료하였습니다.
* 표시는 필수사항 입니다.
* 주의: 국회도서관 이용자 모두에게 공유서재로 서비스 됩니다.
저장 되었습니다.
국회전자도서관에 오신 것을 환영합니다. 로그인을 하시려면 아이디와 비밀번호를 입력해주세요. 모바일 간편 열람증으로 입실한 경우 회원가입을 해야합니다.
공용 PC이므로 한번 더 로그인 해 주시기 바랍니다.
아이디 또는 비밀번호를 확인해주세요
