Doctor of Philosophy Dissertation Development of simple structure 3D X-ray microscope and its application Department of Mechanical Systems Engineering Graduate School of Chonnam National University NGUYEN THANH HAI February 2013 Development of simple structure 3D X-ray microscope and its application Department of Mechanical Systems Engineering Graduate School, Chonnam National University NGUYEN THANH HAI Supervised by Professor JEON, Insu A Dissertation submitted in partial fulfillment of the requirements for the Doctor of Philosophy in Mechanical Systems Engineering. Committee in charge: YOON, Hiseak Prof. KANG, Kiju Prof. YANG, Youngsoo Prof.
Heo, Yonghak Ph.D JEON, Insu Prof. February 2013 CONTENTS LIST OF FIGURES. iv LIST OF TABLES .1 Photoemission electron microscope (PEEM).4 Scanning transmission x-ray microscope .5 Full field and scanning microscope .6 Properties of X-ray .2 Refraction and reflection .7 Background and research objective .8 Organization of the thesis .1 Single layer coating .3 Reflectivity of multilayer .4 Effect of roughness of multilayer on reflectivity. DEVELOPMENT OF A SIMPLE-STRUCTURED ANODE EXCHANGEABLE X- RAY TUBE .2 Design an anode exchangeable x-ray tube.
DEVELOPMENT OF A MULTILAYER MIRROR FOR HIGH-INTENSITY MONOCHROMATIC X-RAY USING LAB-BASED X-RAY SOURCE .2 Design and fabrication of a multilayer parabolic mirror for high-intensity monochromatic x-ray based on glass substrate. DEVELOPMENT OF A MULTILAYER MIRROR FOR HIGH-INTENSITY MONOCHROMATIC PARALLEL X-RAY USING LAB-BASED X-RAY SOURCE .2 Design and fabrication of a multilayer parabolic mirror for high-intensity monochromatic parallel x-ray based on stainless steel substrate. RESULTS AND DISCUSSION .1 Effects of multilayer mirror for high-intensity monochromatic x-ray .2 Effects of multilayer mirror for high-intensity monochromatic parallel x-ray. 81 iii LIST OF FIGURES Figure 1.
Schematic of photoemission electron microscope 2 Figure 1. Schematic of contact microscope 3 Figure 1. Schematic of projection microscope 4 Figure 1. Schematic of scanning transmission x-ray microscope 5 Figure 1.
Schematic of full field transmission x-ray microscope 5 Figure 1. Refraction and reflection for x-rays at the interface 8 Figure 2. Refraction and reflection of thin layer 14 Figure 2. Schematic illustration of multilayer structure and the corresponding notation 18 Figure 2.
Relation between reflectivity and incident angles using Cr Kα wavelength and indicated parameters 19 Figure 2. Relation between reflectivity and energy using Cr Kα wavelength and indicated parameters 20 Figure 2. Effects of periodic ratio on the reflectivity using Cr Kα wavelength and indicated parameters 21 Figure 2. Effects of number of bilayers on the reflectivity using Cr Kα wavelength and indicated parameters 23 Figure 3.
(a) Schematic drawing of the anode exchangeable x-ray tube, and (b) detached structure 27 Figure 3. Measured x-ray spectra of the Al, Cr and Cu anode targets. (a) A wooden plate, and x-ray images taken using (b) Al, (c) Cr, and (d) Cu iv targets 31 Figure 3. MTF change along spatial frequency 32 Figure 3.
Intensity change of X-ray images along pixel number. A parabolic curve 36 Figure 4. Reflectivities of Kα and Kβ along incident angles 38 Figure 4. Designed mirror shape 39 Figure 4.
A mirror substrate 40 Figure 4. A fabricated mirror 40 Figure 4. Surface shape of the mirror and designed shape 41 Figure 4. Representative surface profile of the mirror 41 Figure 4.
SEM image of the cross section of the six W/Al bilayers 42 Figure 5. Reflectivities of Kα and Kβ along incident angles 46 Figure 5. Designed mirror shape 47 Figure 5. A stainless steel substrate for multilayer mirror 47 Figure 5.
Surface shape of the substrate and designed shape at the center profile along the length direction 48 Figure 5. Surface shape of the substrate and designed shape at the center profile along the cross section direction 48 Figure 5. Surface profile of the stainless steel substrate 49 Figure 5. A fabricated mirror 50 Figure 5.
Surface shape of the mirror and designed shape 51 Figure 5. Surface shape of the multilayer mirror and designed shape at the center profile v along the cross section direction 51 Figure 5. Surface profile of the mirror 52 Figure 5. SEM image of the cross section of the six W/Al bilayers 52 Figure 6.
Experiment set up for investigating the effect of multilayer mirror 56 Figure 6. A wood plate 57 Figure 6. X-ray images of wood plate taken (a) using multilayer mirror deposited on glass substrate and (b) without mirror 57 Figure 6. MTF change along the spatial frequency 58 Figure 6.
Intensity change of x-ray images along pixel number 59 Figure 6. A wood tip 60 Figure 6. X-ray images of wood tip taken (a) using multilayer mirror and (b) without mirror 60 Figure 6. MTF change along the spatial frequency 61 Figure 6.
Intensity change of x-ray images along pixel number 61 Figure 6. X-ray images taken (a) using multilayer mirror and (b) without mirror 63 Figure 6. Intensity change of x-ray images along pixel number 63 Figure 6. X-ray images of wood plate taken (a) using multilayer mirror and (b) without mirror 64 Figure 6.
Intensity change of x-ray images along pixel number 65 Figure 6. MTF change along the spatial frequency 65 vi LIST OF TABLES Table 4. Debye-Waller and Nevot-Croce factors calculated using fabricated surface roughness of multilayer mirror based on glass substrate 42 Table 5. Debye-Waller and Nevot-Croce factors calculated using fabricated surface roughness of multilayer mirror based on stainless steel substrate 53 vii DEVELOPMENT OF SIMPLE STRUCTURE 3D X-RAY MICROSCOPE AND ITS APPLICATION NGUYEN THANH HAI Department of Mechanical Systems Engineering Graduate School, Chonnam National University (Supervised by Professor JEON, Insu) (Abstract) The aim of this study is to develop a simple structure of 3D x-ray microscope and some application.
This research consists of four main parts: i) design an anode exchangeable x-ray tube of very simple structure with three kinds of target materials (copper, chromium and aluminum); ii) develop a multilayer mirror producing high-intensity monochromatic x-rays including parallel x-ray beam based on the glass substrate using lab-based x-ray source; iii) design and fabricate mirror deposited by six couples of tungsten and aluminum based on stainless steel substrate that can generate high-intensity monochromatic parallel x-ray; iv) investigate the effects of multilayer mirror on x-ray images obtained by using mirror and without mirror. In design of an anode exchangeable x-ray tube, the operation principle and the structure of the x-ray tube will be described in details. As a result, x-ray spectra of each target material were investigated using spectrometer. X-ray images of a thin wood plate were taken using those targets.
The measured energies of the characteristic x-rays of each target agreed well with the presented results. The difference of resolution and brightness of each image was found based on MTF values and intensities. The developed x-ray tube can give high durability, and higher quality x-ray images of an arbitrary viii object by exchanging anode targets. In another part, the design and fabrication of a parabolic multilayer mirror based on the glass substrate that can produce the high-intensity monochromatic x-rays containing parallel x-rays using a lab-based x-ray source will be described.
For fabricating the mirror, a glass substrate was fabricated and its surface was precisely polished. Six W/Al bilayers were deposited on the glass substrate surface to form the mirror. The effects of the mirror on an x-ray image were investigated using the calculated MTF and image intensity values of the image. The higher MTF and intensity values of the x-ray image, which indicated higher image resolution and brightness, were obtained using the mirror.
The results show a high potential for the fabricated mirror to produce high resolution x-ray images using a lab- based x-ray source. The rest of major purposes of this research is to design and fabricate a multilayer mirror generating high-intensity monochromatic parallel x-ray beam based on stainless steel substrate using a lab-based x-ray source. The mirror is then formed by depositing six W/Al bilayers on the polished stainless steel substrate. The multilayer mirror is utilized for investigating its effects based on the taken x-ray images.
Using this kind of multilayer mirror, the high-intensity monochromatic parallel x-ray region can be obtained. The mirror also shows the high-intensity monochromatic x-ray beside the high- intensity monochromatic parallel x-rays due to the effects of large size of focal spot on target. Based on the obtained x-ray images, the intensity of the image using mirror is larger than that of without mirror. The wood plate as a sample was used to check the effects of multilayer mirror on specific material.
ix CHAPTER 1 INTRODUCTION X-ray microscopes are utilized to investigate the inner structures of quite thin films in biological and biomedical researches. Many kinds of x-ray microscopes have been developed using either synchrotron sources or lab-based x-ray sources during the last few decades. At the early state, Kirkpatrick-Baez x-ray microscope was developed based on the grazing incident reflective optics to focus the x-ray at very large incident angles [1]. Two orthogonal mirrors were used to overcome the severe astigmatism of single spherical mirror.
After that, a new laboratory contact microscope was developed using ocular, positive lens and binocular to reach the stereoscopic effect that can be intensified diaphragms located at exit pupils [2]. Consequently, Underwood increased the resolution of the microscope by using multilayer mirror [3]. Scanning soft x-ray microscope was built using mini-undulator and Fresnel zone plate to increase the resolution up to 75-100 nm [4]. Moreover, scanning photoelectron microscope was designed using Fresnel zone plate and grating monochromator to increase the resolution up to 16 nm [5].
A phase contrast hard x-ray microscopy was developed based on the divergent and coherent beam using lensless geometrical projection to magnify spatial variations in optical path length more than 700 times [6]. In 1999, a microscope for hard x-ray based on parabolic compound refractive lenses was described allowing magnification up to 50 [7]. Sub-100 nm resolution water-window soft x-ray full- field transmission microscopy with a compact system was demonstrated [8]. In 2002, differential aperture x-ray microscope using polychromatic synchrotron x-ray microbeam to probe microstructure with submicrometer spatial resolution in three dimensions [9].
Recently, soft x-ray microscope at spatial resolution below 15 nm using overlay technique for zone 1 plate was reported [10]. For further, detailed development of x-ray microscopes have been summarized [11]. In this chapter, some typical microscopes will be briefly introduced.1 Photoemission electron microscope (PEEM) Photoemission electron microscope, a widely used microscope, utilizes local variations in electron emission to produce image contrast. Electron created by photoemission and photo-absorption are projected by a set of magnetic lenses onto a micro-channel plate intensifier [12].
It consists of an objective (cathode lens), projector lens and double multilayer channel plate (see Fig. Fluorescence Double screen multichannel plate Imaging energy filter Projective lens Focus Extractor X-ray o 30 Sample Figure 1. Schematic of photoemission electron microscope The incident x-ray impinges on and is absorbed by the sample. The ejected primary photoelectrons propagate through the sample and scattering, creating secondary electrons.
Electrons near the surface with enough kinetic energy can overcome the surface work function and are ejected from the sample surface. These electrons are subsequently 2 accelerated and focused by an objective lens. A series of magnetic and electrostatic lenses focus and magnify the photoelectron image onto a multichannel plate, where the signal is intensified and projected onto a fluorescence screen. The fluorescence screen is located in front of the CCD camera, and detect photoelectron-phosphor event that creates visible light.
The amount of counts on CCD depend greatly on the emitted photonelectrons [13]. However, the spatial resolution is limited mainly by the accelerating electrical field between sample and the anode of the objective.2 Contact microscope In the contact microscope, Fig.2, the sample placed on the photo-resist layer is illuminated by an x-ray beam. The map of various photo-absorption coefficient of the sample is recorded on the photo-resist layer. The recorded pattern can be view by the optical.
The resolution with contact microscope is limited by the diffraction effect and penumbra effect due to the angular divergence of the income beam [14]. Schematic of contact microscope 3 1.