論文 / 著書情報
Article / Book Information
題目(和文)

マイクロ・ナノラマン分光によるナノマテリアルの局所物性評価に関する研究

Title(English)

Characterization of local physicochemical properties of nano-sizedmaterials by micro and nano-Raman spectroscopy

著者(和文)

BaloisMariaVanes

Author(English)

Maria Vanessa Balois

出典(和文)

学位:博士（理学）,学位授与機関:東京工業大学,
報告番号:甲第9959号,授与年月日:2015年9月25日,
学位の種別:課程博士,
審査員:林 智広，早澤 紀彦，原正彦，北村房男，尾笹Citation(English)

Degree:,Conferring organization: Tokyo Institute of Technology,
Report number:甲第9959号,
Conferred date:2015/9/25,
Degree Type:Course doctor,
Examiner:

学位種別(和文)

博士論文

Category(English)

Doctoral Thesis

種別(和文)

論文要旨

Type(English)

Summary

Powered by T2R2 (Tokyo Institute Research Repository)

一成

（博士課程）Doctoral Program論 文 要 旨ＴＨＥＳＩＳ ＳＵＭＭＡＲＹ

専攻：
Department of

学生氏名：
Student’s Name

Electronic Chemistry

専攻

Maria Vanessa Cases Balois

申請学位（専攻分野）： 博士
Academic Degree Requested

指導教員（主）：Academic Advisor(main)

指導教員（副）：Academic Advisor(sub)Doctor of（	  Science	  ）

Associate Professor
Tomohiro Hayashi
Professor Masahiko Hara

要旨（英文 800 語程度）
Thesis Summary （approx.800 English Words ）This thesis deals with analyses of local physicochemical properties of strained-silicon nanowires(e-SiNWs) and carbon nanotubes (CNTs) via micro and nano-Raman spectroscopy, respectively, toimprove transistor technology. This work’s significance is addressing the effects of size reduction andcomplexity increase of transistor geometry – a trend dictated by Moore’s law – on transistorperformance. Present-day transistors employ e-Si as channel material using high stress to increasecarrier mobility. The amount of stress is altered, however, during nanopatterning inducing
dimension-dependent anisotropic stress relaxation, suggesting reduced carrier mobility and sizelimitations. To overcome these problems, CNTs as alternative materials are considered because of
their intrinsic electronic transport properties and ultrathin body. Function optimization can be realized
through characterization of CNT’s local electronic properties utilizing nano-Raman.
Chapter 1 Introduction briefly discusses the two materials of interest, e-SiNWs and CNTs, and theirrole in present and future transistor technology, respectively. The current problems of e-SiNWs due to
Moore’s law and the possible solutions of CNTs as channel material are presented. To study suchnano-sized materials, characterization methods, particularly micro-Raman and nano-Raman
spectroscopy, are explained. From here, the objective and the significance of this work were stated.
Chapter 2 Properties of a focused three-dimensional field across an interface for micro-Raman
spectroscopy. The theory and physics on how focused light is diffracted across an interface isdescribed in detail. The three types of polarization (linear, radial, and azimuthal) are explained and theeffects of polarization on the components of the focused electric field (Ex, Ey, and Ez) are compared. Asimple two-layer system consisting of a glass/air interface was studied as proof-of-principle and islater extended to a more complex system (three-layers) in Chapter 3. Utilizing the integral
representation of an electric field for each polarization, the electric field was calculated and visualized
as it travelled between the glass/air interface. It was shown that each polarization generated different
electric field distributions in the transverse (Ex + Ey) and longitudinal (Ez) components and suchinformation would be useful depending on the application.
Chapter 3 Strained Silicon: a theoretical study.The theory of Raman scattering in Silicon and thepolarization selection rules based on the Raman tensors are presented and discussed. Stress in Si(particularly e-Si) can be quantified through the detection of longitudinal optical (LO) and transverse
optical (TO) phonons. The detection of these phonon modes is dictated by their respective Ramantensor, known as the polarization selection rules. In a backscattering geometry, TO modes cannot bedetected and reflects a limitation of micro-Raman spectroscopy. This technique could only detect theaverage amount of stress and was insensitive to anisotropy. It was hypothesized that if a highnumerical aperture (NA) was used, it would be possible to detect TO modes. A Raman spectroscopy
experiment was modeled based on this hypothesis, using 1) an illuminating beam with either linear orradial polarization, 2) a high numerical aperture lens and 3) a sample consisting of a three-layer
system (oil/e-Si/air). Three-dimensional electric calculations were conducted based on the electricfield distribution inside silicon using the theory developed in Chapter 2, which was then applied to theRaman tensor of both LO and TO modes. It was shown via numerical simulations that through the useof a high NA lens and appropriate polarization, it is possible to directly detect the undetectable TOphonons. Therefore making the initially insensitive micro-Raman spectroscopy sensitive anisotropy.

This makes it possible to accurately determine the stress in strained Silicon structures such as
nanowires.
Chapter 4 Strained Silicon: a micro-Raman spectroscopy characterization study of stress after
nanopatterning via precise polarization control. By implementing the experimental conditions
simulated in Chapter 3, TO phonon splitting was experimentally observed for the first time via
micro-Raman spectroscopy. As a result, analysis on the redistribution of stress after nanopatterning
could be done. It was found that stress relaxation anisotropy was experienced by the nanowires andthis anisotropy was greatly influenced by the nanowire’s geometry. It was also found that even at
small dimensions, high anisotropic stress can still be attained. This finding is important because it iscontrary to the prevalent belief that as the dimensions of e-SiNWs become smaller, the stress alsodecreases. The work in Chapter 4 presents a new method of stress characterization that is sensitive toanisotropic stress and will be very useful for strain nanoengineering of transistors.
Chapter 5 Carbon Nanotubes: theory, properties and tip-enhanced Raman spectroscopy. The
discussion shifts to carbon nanotubes giving a brief background on their properties. The Raman
spectrum of CNTs was also discussed and what information can be extracted from these spectra wasexplained. To study CNTs whose diameters range from 0.7 to 10 nm, nano-Raman spectroscopy
techniques such as tip-enhanced Raman spectroscopy (TERS) must be employed to spatially resolve
them. This chapter demonstrates the power of TERS in terms of spatial resolution and signalenhancement.
Chapter 6 Carbon Nanotubes: tip-enhanced terahertz Raman scattering, a nano-Raman
spectroscopy study. In order to precisely study CNTs, and any other sample for that matter, using
TERS, possible sources of problems from the technique must be addressed. It has been said that TERS
is a non-invasive analytical tool, but TERS generates a strong enhanced electric field, and it isunavoidable that this electric field can generate heat. This heating can affect the sample, tip andsubstrate (if it is metallic), thus affecting sample analysis. In this light, TERS can be viewed asinvasive. In order to establish TERS as a truly non-invasive analytical tool, the local temperature
generated at the tip apex must be determined and controlled. This is most especially important whenstudying heating effects in CNTs, which is an important aspect for transistors. To overcome thischallenge, a novel temperature determination technique that can detect the temperature andtemperature changes at the nanoscale has been developed. This technique is called tip-enhanced THz
Raman spectroscopy (TE-THzRS). Through the detection of the RBM of CNTs and the Boltzmann
distribution, the temperature of the CNTs was determined. It was also found that at low temperatures(less than 100˚C) the temperature can be controlled by controlling the power of the illuminating laser.
TE-THzRS is not only useful for CNTs but can be extended to other fields and applications as well,such as biological samples.
Chapter 7 Summary and Conclusions. A brief summary of this thesis is given and the important
conclusions from each chapter are mentioned.
備考 : 論文要旨は、和文 2000 字と英文 300 語を 1 部ずつ提出するか、もしくは英文 800 語を 1 部提出してください。
Note : Thesis Summary should be submitted in either a copy of2000 Japanese Characters and 300 Words (Engｌish) or 1copy of 800

Words (English).
注意：論文要旨は、東工大リサーチリポジトリ（T2R2）にてインターネット公表されますので、公表可能な範囲の内容で作成してください。
Attention: Thesis Summary will be published on Tokyo Tech Research Repository

Website (T2R2).