Abstract ▼

Title: Nano-scale materials characterization for atomic structure and chemical composition using FE-TEM
Characterization is a continuous quest that parallels the search of improved materials and devices, with particularly stiff challenges being raised by the recent development of nano-structures

Title: Nano-scale materials characterization for atomic structure and chemical composition using FE-TEM
Characterization is a continuous quest that parallels the search of improved materials and devices, with particularly stiff challenges being raised by the recent development of nano-structures and related technologies. The objective of present study is to establish a cost-effective nano-scale materials characterization technique revealing information of both atomic structure and chemical composition concurrently with a sub-nanometer spatial resolution utilizing field-emission transmission electron microscopy (FE-TEM). Quantitative analysis for chemical composition analysis aiming mainly light weight elements (B-O), computer simulation of high resolution electron microscopy (HREM) image, and nano-probe convergent beam electron diffraction (CBED) technique can make FE-TEM, at present, as the most reliable analysis tool for both structural and chemical characterization of materials in nano- scale. The establishment of these techniques is, thus, crucial for the upcoming development of nano-electronics and nano-photonic devices. Following are the results of this nano frontier project.
(1) Nano-beam diffraction (NBD) and nano-beam EDS analysis studies with a sub-nanometer spatial resolution
The main research topic of the present study is the characterization of initial growth behavior, its associated interfacial reaction during thin film deposition and subsequent defects formation occurring at interfaces. Research activities have been focused mainly on magnetic multi-layer thin films and oxide thin films used for memory or data storage devices applications.
The properties of multilayer nano-devices, such as MRAM (Magnetic Random Access Memory), multi-quantum well and quantum dots, strongly depend on the interface structure and chemistry as well as atomic arrangement. The characterization and control of interface structure and chemistry are essential part in understanding and for fabricating nano-devices. However, rarely found are the experimental results on the interfacial structure affecting the magnetic properties of magnetic multilayer thin films due to the intrinsic difficulties in characterizing the interface structure. In the present research, NBD and nano-beam EDS techniques will be applied to analyze the interface structure and chemistry with a sub-nanometer spatial resolution.
(2) Computer simulation and quantitative analysis of HREM image
Quantitative analysis of the HREM image has been, recently realized by the incorporation of digital recording media, such as image plate (IP). For the quantitative analysis, the electron dose distribution of HREM image canbe converted to a two-dimensional contour mapping. The electron intensity contour map will, then, be compared with the results of computer simulation results to obtain more precise information on localatomic arrangement at interfaces, site determination of unknown crystal structures, local lattice parameter and nano-scale crystalline defects.
Digitized HREM images directly recorded on IP can also be processed by using various image filtering and numerical functions such as Fourier transform. Fourier transform of the electrostatic potential of the local lattice, that corresponds to the diffraction spots to form a HREM image, can also be inversely transformed by selecting either whole spots or only specific spots along certain crystallographic direction. These methods can easily visualize various lattice defects and materials with different lattice constant, otherwise hardly seen in as-recorded HREM image.
(3) Compositional and Chemical analyses in nano-scale by using EELS and EF-TEM
As scale for fabrication becomes smaller, the effects of interfacial structure on the electrical properties becomes more important. Outof various spectroscopy techniques, electron energy loss spectroscopy within FE- TEM has many advantages for interfacial characterization.
Some kinds of specimen have a limit for structural identification with ordinary TEM techniques due to structural similarity. Therefore energy filtering within FE-TEM can be much powerful equipment because it visualizes the images of specific elements. Therefore the identification of multi -layer thin films with similar structure can be accomplished by energy filtering techniques optimized in nano-scale i.e. high magnification and resolution condition.
(4) Collaborations within this nano-frontier project
In order to achieve a successful application of chemical and structural analysis techniques, developed in our research group, to practical fabrication of nano-structures, collaborations with other development research group are quite important. Many achievements were expected through these collaborations. With nano-materials growth research group, improvement of crystal andelectrical properties are accomplished through the optimization of growth condition. In case of our analysis group, the developed TEM analysis techniques can be applied to the real nano-devices and materials. More accurate techniques can be also performed by feedback.

목차 Contents

• 제 1 장 연구개발과제의 개요...19
• 제 2 장 국내외 기술개발현황...20
• 제 3 장 연구개발수행 내용 및 결과...22
• 제 1 절 나노 빔을 이용한 EDS 성분 분석...22
• 1. 에너지 분산 분광법 (EDS)의 신뢰도 검증...22
• 가. EDS 분석시 발생하는 시편 오염 및 제거...22
• 나. 신뢰성 있는 나노 빔의 형성...25
• 2. 나노 빔 EDS를 이용한 SrRuO₃ 박막의 계면 반응 분석...26
• 가. SrRuO₃ 박막의 결정 구조...26
• 나. SrRuO₃ 박막과 Si 기판의 계면 반응 분석...30
• 제 2 절 Digital image processing을 이용한 고분해능 영상의 정량적 해석...39
• 1. 자성 다층 박막의 계면 구조 분석을 위한 고분해능 영상의 정량적 해석...39
• 2. 다양한 시스템에서의 digital image processing...43
• 제 3 절 전자에너지 손실분광법을 잉요한 성분 분석 및 에너지 필터링을 이용한 성분 분포 분석...52
• 1. 전자에너지 손실분광법 (electron energy loss spectroscopy, EELS)...52
• 2. EELS 분석 조건의 최적화와 나노 빔 EELS 분석...56
• 3. 에너지 필터링 (energy filtering) 영상...57
• 제 4 절 나노 분석법을 이용한 ALD 나노 소자 공동 연구...65
• 제 4 장 목표달성도 및 관련분야에의 기여도...69
• 제 5 장 연구개발결과의 활용계획...70
• 제 6 장 연구개발과정에서 수집한 해외과학기술정보...71
• 제 7 장 참고문헌...72