| 학회 | 한국재료학회 |
| 학술대회 | 2015년 가을 (11/25 ~ 11/27, 부산 해운대그랜드호텔) |
| 권호 | 21권 2호 |
| 발표분야 | D. 구조 재료 |
| 제목 | Correlative Microscopy of Nanostructured Materials |
| 초록 | In my talk I will focus on several recent examples utilizing correlative techniques (Atom-probe tomography (APT) + Scanning transmission electron microscopy (STEM)) to analyze the same sample, to obtain information that would be impossible to obtain using only one instrument. The specific problems are as follows: (1) Using APT and STEM sequentially, on the same microtip sample, we characterized the evolution of oxide and hydride phases using APT. We find agreement of the oxide and hydride types determined by STEM's diffraction patterns and elecrton-energy loss spectrosopy (EELS); (2) APT is utilized to obtain three-dimensional chemical information concerning grain boundary (GB) segregation with atomic spatial resolution. The detailed crystallography of GBs is determined using a combined approach of electron backscatter diffraction and FIB to establish a GB’s five macroscopic degrees of freedom, followed by an APT GB composition analysis. Characterizations of GB microstructure and microchemistry are performed to improve our understanding of mechanisms controlling intergranular attack and stress-corrosion cracking. Atom-probe tomography (APT) is in the midst of a dynamic renaissance as a result of the development of a well-engineered commercial instrument that is robust and ergonomic and capable of collecting large data sets, hundreds of millions of atoms, in short time periods compared to earlier instruments. An APT is a field-ion microscope coupled directly to a special time-of-flight (TOF) mass spectrometer that permits one to determine the mass-to-charge state of individual field-evaporated ions plus their x-, y-, and z-coordinates in a specimen in direct space with subnanoscale resolution. The three-dimensional (3D) data sets acquired are analyzed using increasingly sophisticated software programs that utilize high-end workstations, which permit one to handle increasingly large data sets. APT has the unique ability to dissect a lattice, with subnanometer-scale spatial resolution, using either voltage or laser pulses, on an atom-by-atom and atomic plane-by-plane basis and to reconstruct it in 3D with the chemical identity of each detected atom identified by TOF mass spectrometry. Employing femto- or pico-second laser pulses using visible (green or blue light) to ultraviolet light (355 nm wavelength) makes the analysis of metallic, semiconducting, ceramic, and organic materials practical to different degrees of success. The utilization of dual-beam focused ion-beam microscopy for the preparation of microtip specimens from multilayer structures and surface films, semiconductor devices, and for producing site-specific specimens extends enormously the capabilities of APT to a wider range of scientific and technologically important problems than could be previously studied for a range of materials: metals, semiconductors, ceramics, biominerals, and organics. The advent of aberration-corrected scanning transmission electron microscopy (STEM) coupled with an electron-energy loss spectoscope (EELS) equipped, which is equipped with a LN2 double-tilt cooling-stage, operating between 94 to 300 K, makes it possible to utilize annular bright-field (ABF) imaging of atoms as light as hydrogen. And the presence of H in an ABF image is proven to be real by recording EELS H K-edge spectra from the same specimen. STEMs are also equipped with a high-angle annular dark-field (HAADF) detector, which provides Z (atomic number) contrast from individual columns of atoms. |
| 저자 | 김윤준 |
| 소속 | 인하대 |
| 키워드 | <P>Transmission electron microscopy; Atom-probe tomography; Nano-precipitates; Grain boundary segregation</P> |
