JP6457766B2 - Apparatus and method for determining the number of layers in a two-dimensional thin film atomic structure using Raman scattering spectrum of an insulating material - Google Patents
Apparatus and method for determining the number of layers in a two-dimensional thin film atomic structure using Raman scattering spectrum of an insulating material Download PDFInfo
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Description
本発明は、絶縁材料上に支持されたグラフェン等の２次元薄膜原子構造の積層数決定装置及び積層数決定方法に関する。 The present invention relates to a stack number determining apparatus and a stack number determining method for a two-dimensional thin-film atomic structure such as graphene supported on an insulating material.
グラフェンは、２００４年にNovoselovらが、スコッチテープを用いてグラファイトから機械的に剥離し、酸化膜付きシリコン基板に転写する方法を発見して以来、物性実験からその価値を見出された。 Graphene has found its value in physical properties experiments since 2004 when Novoselov et al. Discovered a method of mechanically peeling it from graphite using scotch tape and transferring it to a silicon substrate with an oxide film.
その後、基礎科学、電子デバイス、センサー、電池等の幅広い分野で研究開発が活発に行われている。グラフェンは、その理想的な２次元構造に起因して様々な特異的性質を有し、各種分野への応用が期待されている物質である。 Since then, research and development has been actively conducted in a wide range of fields such as basic science, electronic devices, sensors, and batteries. Graphene is a substance that has various specific properties due to its ideal two-dimensional structure and is expected to be applied in various fields.
また、グラフェンを筆頭に、原子の２次元的結合構造、あるいは、それと等価な２次元的電子状態を表面、界面などに有する機能性を持った薄膜物質は、従来のバルク物質や単なる薄膜とは異なる特性・構造を持つことで、新たな機能や従来材料の特性を凌駕する機能を発現することが可能であり、新規材料やデバイスの開発につながることが期待される。 In addition, thin film materials that have the functionality of having graphene as the leading element and the two-dimensional bonding structure of atoms, or equivalent two-dimensional electronic states at the surface and interface, are the conventional bulk materials and mere thin films. By having different characteristics and structures, it is possible to develop new functions and functions that surpass the characteristics of conventional materials, which is expected to lead to the development of new materials and devices.
このような２次元薄膜原子構造は、その産業上の利用において、精密な積層数の評価が不可欠である。すなわちグラフェン等の２次元薄膜原子構造は、積層数に依存して電子物性や光学特性が顕著に変化するので、所望の機能を発揮させるためには、予め積層数を決定してデバイスを作製することが要求される。例えばグラフェン積層数の評価法は、キャパシター特性をはじめ、各種デバイスの性能向上に不可欠な技術である。 Such a two-dimensional thin-film atomic structure requires an accurate evaluation of the number of stacked layers for industrial use. In other words, the two-dimensional thin film atomic structure such as graphene changes significantly in the electronic properties and optical characteristics depending on the number of layers. Therefore, in order to exert a desired function, the number of layers is determined in advance to manufacture a device. Is required. For example, the evaluation method of the number of graphene stacks is an indispensable technique for improving the performance of various devices including capacitor characteristics.
従来、絶縁材料上に転写したグラフェンの積層数を評価するものとして、次のような方法が知られている。 Conventionally, the following methods are known for evaluating the number of graphene layers transferred onto an insulating material.
（ａ）ラマン分光法によるグラフェン２Ｄバンド（Ｇ’バンド)の線形フィッティング（非特許文献１、２）。
この方法では、グラフェンのＧバンドと２Ｄバンドの相対強度比、２Ｄバンドの波数（エネルギー）、２Ｄバンドの形状などを基にグラフェン積層数を決定する。
(A) Linear fitting of graphene 2D band (G ′ band) by Raman spectroscopy (Non-Patent Documents 1 and 2).
In this method, the number of graphene layers is determined based on the relative intensity ratio between the G band and 2D band of graphene, the wave number (energy) of 2D band, the shape of 2D band, and the like.
（ｂ）反射光学顕微鏡観察によるコントラスト測定（非特許文献３）。
この方法における観察の原理は、基板と基板上のグラフェンの光学反射によるコントラスト差である。グラフェンを酸化膜付きシリコン基板に貼り付け、そのグラフェンの光学顕微鏡像を取得した後、ＳｉＯ２表面とグラフェンの光学顕微鏡像のコントラスト比を比較する。
(B) Contrast measurement by observation with a reflection optical microscope (Non-patent Document 3).
The principle of observation in this method is a contrast difference due to optical reflection between the substrate and graphene on the substrate. After graphene is attached to a silicon substrate with an oxide film and an optical microscope image of the graphene is acquired, the contrast ratio of the SiO 2 surface and the optical microscope image of graphene is compared.
（ｃ）透過型電子顕微鏡(ＴＥＭ)、原子間力顕微鏡(ＡＦＭ)、走査型電子顕微鏡（ＳＥＭ、特許文献１）による方法。 (C) A method using a transmission electron microscope (TEM), an atomic force microscope (AFM), or a scanning electron microscope (SEM, Patent Document 1).
また、六方晶窒化ホウ素は、グラフェンとよく似た蜂の巣構造を持つ絶縁材料で、窒素とホウ素が形成する非常に強いｓｐ２結合の２次元平面構造が弱い結合で積層した構造になっている。この六方晶窒化ホウ素でも、ラマン分光法による積層数の評価（非特許文献４）、反射光学顕微鏡観察によるコントラスト測定に基づく積層数の評価（非特許文献５）が報告されている。 Hexagonal boron nitride is an insulating material having a honeycomb structure similar to that of graphene, and has a structure in which a very strong sp 2 bond two-dimensional planar structure formed by nitrogen and boron is laminated with a weak bond. Even with this hexagonal boron nitride, evaluation of the number of layers by Raman spectroscopy (Non-patent Document 4) and evaluation of the number of layers based on contrast measurement by reflection optical microscope observation (Non-Patent Document 5) have been reported.
しかしながら、従来の（ａ）〜（ｃ）による積層数の評価は、以下の点で研究開発のボトルネックとなっていた。 However, the conventional evaluation of the number of layers by (a) to (c) has been a bottleneck for research and development in the following points.
上記（ａ）の方法は、グラフェンを支持する絶縁材料の種類によっては、絶縁材料上に転写したグラフェンのラマンピークが絶縁材料のピークと重なってしまう。例えば、ダイヤモンド基板上に転写したグラフェンのラマンピークは、ダイヤモンド（２次）のピークと重なるため、線形解析による積層数評価が困難である。また、５枚以上積層したグラフェンでは、積層数が増すにつれて、各積層数のグラフェンを特徴付けるラマンバンドの位置や形状が不規則に変化することに起因して、ラマンピークの線形がより複雑化し、解析が難しくなる。 In the method (a), the Raman peak of graphene transferred onto the insulating material overlaps with the peak of the insulating material depending on the type of the insulating material that supports the graphene. For example, since the Raman peak of graphene transferred onto a diamond substrate overlaps with the peak of diamond (secondary), it is difficult to evaluate the number of layers by linear analysis. In addition, in the graphene laminated with 5 or more layers, as the number of stacked layers increases, the position and shape of the Raman band that characterizes the number of stacked graphenes irregularly changes, and the Raman peak alignment becomes more complicated, Analysis becomes difficult.
上記（ｂ）の方法は、基板のみの反射強度Ｒ０とｎ層グラフェンが積層した基板上の反射強度Ｒの差が無い場合、コントラスト(＝Ｒ／Ｒ０−１)がなくなり、積層数評価が難しい。この方法では基板として酸化膜付きシリコン基板のみが検討されているが、使用可能な基板の制約がある。また、グラフェン積層数とコントラスト比の線形性の制約によって、６層程度を超える積層数の評価が難しい。 In the method (b), when there is no difference between the reflection intensity R 0 of the substrate only and the reflection intensity R on the substrate on which the n-layer graphene is laminated, the contrast (= R / R 0 −1) disappears and the number of laminations is evaluated. Is difficult. In this method, only a silicon substrate with an oxide film is considered as a substrate, but there are restrictions on the substrates that can be used. Moreover, it is difficult to evaluate the number of stacked layers exceeding about six layers due to the restrictions on the linearity of the number of graphene layers and the contrast ratio.
上記（ｃ）の方法は、装置が大がかりで、測定や解析には高度な知識と熟練された技術を要する。高真空での測定、試料サイズなど、測定条件も限定される。 The method (c) requires a large apparatus and requires advanced knowledge and skill in measurement and analysis. Measurement conditions such as high vacuum measurement and sample size are also limited.
グラフェンのうち、工業的な利用が期待されるものには１０〜１５層程度のものが多く、このような積層数のものを、非破壊で、かつ、その場観察ができる方法が望まれていた。そしてグラフェンデバイス作製のための基板を選択できないことは、グラフェンデバイスの応用範囲を狭めてしまうことにもなり得る。 Of the graphene, many are expected to be used industrially, with about 10 to 15 layers, and there is a demand for a method capable of non-destructive and in-situ observation of such stacks. It was. The inability to select a substrate for producing a graphene device can narrow the application range of the graphene device.
本発明は、以上の通りの事情に鑑みてなされたものであり、グラフェンの積層数を簡便かつ正確に決定することができ、特に、大がかりな装置や、高度な知識と熟練された技術を要せず、測定条件に厳しい制限のない、絶縁材料上の２次元薄膜原子構造の積層数決定装置及び積層数決定方法を提供することを課題としている。 The present invention has been made in view of the circumstances as described above, and can easily and accurately determine the number of graphene layers. In particular, it requires a large-scale apparatus and advanced knowledge and skill. Therefore, it is an object of the present invention to provide a stack number determining apparatus and a stack number determining method for a two-dimensional thin-film atomic structure on an insulating material without severe restrictions on measurement conditions.
また本発明は、上記の課題に対して、単層から３０層までの広範囲にわたる積層数評価が可能な、絶縁材料上の２次元薄膜原子構造の積層数決定装置及び積層数決定方法を提供することを課題としている。 The present invention also provides a stack number determining apparatus and stack number determining method for a two-dimensional thin-film atomic structure on an insulating material, which can evaluate the stack number over a wide range from a single layer to 30 layers. It is an issue.
また本発明は、上記の課題に加えて、絶縁材料の種類による制限の少ない、絶縁材料上の２次元薄膜原子構造の積層数決定装置及び積層数決定方法を提供することを課題としている。 Another object of the present invention is to provide an apparatus for determining the number of stacked layers and a method for determining the number of stacked layers of a two-dimensional thin-film atomic structure on an insulating material, which are less limited by the type of insulating material.
グラフェンは、炭素原子の薄層構造でありながら、その独特な電気的特性により不透明度が高い。本発明者らは、従来のようにグラフェンのラマンスペクトルの線形解析から積層数を評価するのではなく、グラフェンを転写したラマン活性を示す絶縁材料からのラマンピークを用いて転写されたグラフェン積層数を評価した。 Although graphene is a thin layer structure of carbon atoms, it has high opacity due to its unique electrical characteristics. The present inventors do not evaluate the number of stacks from the linear analysis of the graphene Raman spectrum as in the prior art, but the number of graphene stacks transferred using the Raman peak from the insulating material exhibiting the Raman activity to which the graphene is transferred. Evaluated.
その結果、グラフェンの遮光効果を利用して、グラフェンが載っている絶縁基板由来のラマンピークを測定することで、グラフェンの積層数を簡便かつ正確に導くことができることを見出し、本発明を完成するに至った。 As a result, the inventors have found that the number of graphene stacks can be easily and accurately derived by measuring the Raman peak derived from the insulating substrate on which graphene is mounted using the light shielding effect of graphene, and complete the present invention. It came to.
すなわち、本発明の２次元薄膜原子構造の積層数決定装置及び積層数決定方法は、以下のことを特徴としている。ここで、以下の記述においてＩａ、Ｉｂ、Ｉ０の定義は次のとおりである。
Ｉａ：絶縁材料に支持された積層数未知の２次元薄膜原子構造に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、顕微ラマン分光計によって測定した絶対強度である。
Ｉｂ：絶縁材料に支持された積層数既知の２次元薄膜原子構造に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、顕微ラマン分光計によって測定した絶対強度である。
Ｉ０：２次元薄膜原子構造を配置しない絶縁材料に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、顕微ラマン分光計によって測定した絶対強度である。
That is, the two-dimensional thin film atomic structure lamination number determination apparatus and lamination number determination method of the present invention are characterized by the following. Here, in the following description, the definitions of I a , I b , and I 0 are as follows.
I a : Spectral peak intensity of Raman scattered light derived from insulating material, measured by irradiating incident laser light onto two-dimensional thin film atomic structure with unknown number of layers supported by insulating material, measured by microscopic Raman spectrometer Absolute intensity.
I b : Spectral peak intensity of Raman scattered light derived from an insulating material measured by irradiating incident laser light onto a two-dimensional thin film atomic structure with a known number of layers supported by the insulating material, measured by a microscopic Raman spectrometer Absolute intensity.
I 0 : Spectral peak intensity of Raman scattered light derived from an insulating material, measured by irradiating an insulating material not having a two-dimensional thin film atomic structure with incident laser light, and an absolute intensity measured by a microscopic Raman spectrometer.
本発明の２次元薄膜原子構造の積層数決定装置は、ラマン活性な絶縁材料上の２次元薄膜原子構造の積層数決定装置であって、
前記絶縁材料に支持された積層数未知の２次元薄膜原子構造に入射レーザー光を照射し、前記絶縁材料由来のラマン散乱光の分光ピーク強度比Ｉａ／Ｉ０を取得するための測定を行う顕微ラマン分光計と、
前記絶縁材料に支持された積層数既知の２次元薄膜原子構造に前記入射レーザー光を照射して発生する前記絶縁材料由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０と、前記２次元薄膜原子構造の積層数ｎとの関係を示し、且つ、前記積層数既知の２次元薄膜原子構造の単層に対する前記入射レーザー光の透過率Ｔ及び積層数ｎより、次の関係式：
Ｉ ｂ ／Ｉ ０ ＝Ｔ ２ｎ
で表わされる標準曲線に基づいて、前記分光ピーク強度比Ｉａ／Ｉ０を前記標準曲線と照合し、前記積層数未知の２次元薄膜原子構造の積層数を決定する積層数決定機構とを備えている。
The apparatus for determining the number of stacked layers of a two-dimensional thin film atomic structure according to the present invention is a device for determining the number of stacked layers of a two-dimensional thin film atomic structure on a Raman-active insulating material,
Irradiating incident laser light onto a two-dimensional thin film atomic structure with an unknown number of layers supported by the insulating material, and performing measurement for obtaining a spectral peak intensity ratio I a / I 0 of Raman scattered light derived from the insulating material A micro-Raman spectrometer,
Spectral peak intensity ratios I b / I 0 of Raman scattered light derived from the insulating material generated by irradiating the incident laser light on a two-dimensional thin film atomic structure having a known number of layers supported by the insulating material, and the two-dimensional the relationship between the number n of stacked thin atomic structure shows, and the more the transmittance T and the stacking number n of the incident laser beam, the following relational expression of the single layer of the lamination number known two-dimensional thin atomic structure:
I b / I 0 = T 2n
The spectral peak intensity ratio I a / I 0 is collated with the standard curve on the basis of the standard curve represented by : and a stacking number determination mechanism for determining the stacking number of the two-dimensional thin film atomic structure whose stacking number is unknown. ing.
また本発明のラマン活性な絶縁材料上の２次元薄膜原子構造の積層数決定方法は、次の工程を含む：
次の工程を含む、ラマン活性な絶縁材料上の２次元薄膜原子構造の積層数決定方法：
前記絶縁材料に支持された積層数既知の２次元薄膜原子構造に入射レーザー光を照射して発生する前記絶縁材料由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０と、前記２次元薄膜原子構造の積層数ｎとの関係を示し、且つ、前記積層数既知の２次元薄膜原子構造の単層に対する前記入射レーザー光の透過率Ｔ及び積層数ｎより、次の関係式：
Ｉ ｂ ／Ｉ ０ ＝Ｔ ２ｎ
で表わされる標準曲線を取得する工程；
前記絶縁材料に支持された積層数未知の２次元薄膜原子構造に前記入射レーザー光を照射し、前記絶縁材料由来のラマン散乱光の分光ピーク強度比Ｉａ／Ｉ０を取得する工程；及び
前記分光ピーク強度比Ｉａ／Ｉ０を前記標準曲線と照合し、前記積層数未知の２次元薄膜原子構造の積層数を決定する工程。
In addition, the method for determining the number of layers of the two-dimensional thin film atomic structure on the Raman active insulating material of the present invention includes the following steps:
A method for determining the number of stacks of two-dimensional thin-film atomic structures on a Raman-active insulating material, including the following steps:
Spectral peak intensity ratios I b / I 0 of Raman scattered light derived from the insulating material generated by irradiating incident laser light onto a two-dimensional thin film atomic structure having a known number of layers supported by the insulating material, and the two-dimensional thin film shows the relationship between the number n of stacked atomic structure, and, wherein from the transmittance T and the stacking number n of the incident laser beam, the following relational expression of the single layer of the lamination number known two-dimensional thin atomic structure:
I b / I 0 = T 2n
Obtaining a standard curve represented by:
Irradiating the incident laser light onto a two-dimensional thin film atomic structure with an unknown number of layers supported by the insulating material to obtain a spectral peak intensity ratio I a / I 0 of Raman scattered light derived from the insulating material; and A step of collating the spectral peak intensity ratio I a / I 0 with the standard curve and determining the number of layers of the two-dimensional thin film atomic structure whose number of layers is unknown.
好ましい態様において、前記標準曲線は、前記絶縁材料に支持され、それぞれ積層数ｎが異なる前記積層数既知の２次元薄膜原子構造を複数用意して前記分光ピーク強度比Ｉｂ／Ｉ０を取得し、これと前記２次元薄膜原子構造の積層数ｎとの関係に基づいて取得される。 In a preferred embodiment , the standard curve is supported by the insulating material, and a plurality of two-dimensional thin film atomic structures having a known number of layers, each having a different number of layers n, are prepared to obtain the spectral peak intensity ratio I b / I 0. , And obtained based on the relationship between the number n of the two-dimensional thin film atomic structures stacked.
本発明によれば、グラフェン等の２次元薄膜原子構造の遮光効果を利用して、２次元薄膜原子構造を支持する絶縁基板由来のラマン散乱強度比を取得することで、２次元薄膜原子構造の積層数を簡便かつ正確に決定することができる。測定に必要なものは顕微ラマン分光計のみで、その他の大がかりな装置、高度な知識と熟練された技術を要しない。そして常温、大気圧下での測定でも積層数評価が可能で、高真空での測定、試料サイズなど、測定条件の厳しい制限がない。 According to the present invention, by utilizing the light-shielding effect of a two-dimensional thin film atomic structure such as graphene, a Raman scattering intensity ratio derived from an insulating substrate that supports the two-dimensional thin film atomic structure is obtained, thereby The number of stacked layers can be determined easily and accurately. All that is required for the measurement is a microscopic Raman spectrometer, which does not require any other large-scale equipment, advanced knowledge and skill. The number of stacked layers can be evaluated even at room temperature and atmospheric pressure, and there are no strict restrictions on measurement conditions such as high vacuum measurement and sample size.
また本発明によれば、単層から３０層までの広範囲にわたる積層数評価が可能である。 According to the present invention, it is possible to evaluate the number of stacked layers over a wide range from a single layer to 30 layers.
また本発明によれば、ラマン活性を示す絶縁材料ならば絶縁材料の種類による制限が少なく、例えばグラフェン等の２次元薄膜原子構造とのコントラストが小さい絶縁材料でも積層数が評価できる。 Further, according to the present invention, the number of stacked layers can be evaluated even with an insulating material having a small contrast with the two-dimensional thin film atomic structure such as graphene, for example, if the insulating material exhibits Raman activity.
以下に、図面を参照しながら本発明の実施形態について説明する。 Embodiments of the present invention will be described below with reference to the drawings.
図１及び図２は、本発明の２次元薄膜原子構造の積層数決定装置の実施形態の概略構成を示した図である。 1 and 2 are diagrams showing a schematic configuration of an embodiment of an apparatus for determining the number of stacked layers of a two-dimensional thin film atomic structure according to the present invention.
積層数決定装置１は、絶縁材料２０上の２次元薄膜原子構造２１の積層数を決定するものであり、図１に示すように、２次元薄膜原子構造２１に入射レーザー光を照射し、ラマン散乱光の強度を測定する測定部２を備えている。 The stack number determining apparatus 1 determines the number of stacks of the two-dimensional thin film atomic structure 21 on the insulating material 20, and irradiates the two-dimensional thin film atomic structure 21 with incident laser light as shown in FIG. A measuring unit 2 for measuring the intensity of scattered light is provided.
また積層数決定装置１は、図１及び図２に示すように、測定部２が測定したラマン散乱光の強度を元に２次元薄膜原子構造２１の積層数を決定する積層数決定部３を備えている。 Further, as shown in FIGS. 1 and 2, the stack number determining apparatus 1 includes a stack number determining unit 3 that determines the number of stacks of the two-dimensional thin film atomic structure 21 based on the intensity of Raman scattered light measured by the measuring unit 2. I have.
測定部２は、絶縁材料２０に支持された積層数未知の２次元薄膜原子構造２１に入射レーザー光１１を照射し、絶縁材料２０由来のラマン散乱光の分光ピーク強度Ｉａを測定するための顕微ラマン分光計である。また測定部２では、前述の分光ピーク強度Ｉｂ及びＩ０も測定される。 Measurement unit 2, the incident laser beam 11 in the stacking number of unknown 2D thin atomic structure 21 supported by the insulating material 20 is irradiated, for measuring the spectral peak intensity I a of the Raman scattered light derived from the insulating material 20 It is a micro Raman spectrometer. Further, in the measurement unit 2, the spectral peak intensity I b and I 0 described above is also measured.
測定部２は、絶縁材料２０に支持された２次元薄膜原子構造２１に入射レーザー光１１を照射するためのレーザー光源１０と、入射レーザー光１１を照射して発生する絶縁材料２０由来のラマン散乱光を分光する分光器１６と、分光したラマン散乱光を検出する検出器１７とを備えている。 The measurement unit 2 includes a laser light source 10 for irradiating the incident laser beam 11 to the two-dimensional thin film atomic structure 21 supported by the insulating material 20, and Raman scattering derived from the insulating material 20 generated by irradiating the incident laser beam 11. A spectroscope 16 that splits the light and a detector 17 that detects the spectroscopic Raman scattered light are provided.
レーザー光源１０は、入射レーザー光１１が安定な単波長であること、十分なラマン散乱光を発生させるために強度の高い光源であること、光源の線幅が狭いほど波数分解能が高くなること等を考慮して選択される。レーザー光源１０としては、例えば、固体レーザー、半導体レーザー、アルゴンイオンレーザー等が挙げられる。 The laser light source 10 is such that the incident laser beam 11 has a stable single wavelength, is a high-intensity light source for generating sufficient Raman scattered light, and the wave number resolution increases as the line width of the light source decreases. Is selected. Examples of the laser light source 10 include a solid laser, a semiconductor laser, and an argon ion laser.
分光器１６は、絶縁材料２０より発生したラマン散乱光を分光する。分光器１６としては、例えば、回折格子を組み込んだポリクロメーター等が挙げられる。 The spectroscope 16 separates Raman scattered light generated from the insulating material 20. Examples of the spectroscope 16 include a polychromator incorporating a diffraction grating.
検出器１７は、ラマン散乱光は非常に微弱なため、感度（量子効率）の高いものを使用することが望ましい。検出器１７の量子効率は波長によって大きく変わるので、励起波長及び測定波数範囲に合わせた選択が必要となる。レーザー光源１０として可視光源を使用する場合、冷却ＣＣＤ検出器を用いることができる。 As the detector 17, Raman scattered light is very weak, so it is desirable to use a detector with high sensitivity (quantum efficiency). Since the quantum efficiency of the detector 17 varies greatly depending on the wavelength, selection according to the excitation wavelength and the measurement wavenumber range is required. When a visible light source is used as the laser light source 10, a cooled CCD detector can be used.
顕微ラマン分光計は、図示はしないが、接眼レンズによる試料の観察や、内蔵カメラによるモニター表示、オートフォーカス、画像上でのマウスクリックによる目的箇所のセンタリングが可能な構成とすることができる。 Although not shown in the figure, the microscopic Raman spectrometer can be configured such that a sample can be observed by an eyepiece, monitor display by a built-in camera, autofocus, and centering of a target location by mouse click on an image.
絶縁材料２０は、Ｘ−Ｙステージ１８の試料台上に配置されており、Ｘ−Ｙステージ１８を駆動することによって絶縁材料２０をＸ−Ｙ走査できるように構成されている。 The insulating material 20 is disposed on the sample stage of the XY stage 18 and is configured so that the XY scanning of the insulating material 20 can be performed by driving the XY stage 18.
レーザー光源１０から出射された入射レーザー光１１は、ハーフミラー１２によって反射され、顕微鏡対物レンズ１３によって集光されて、絶縁材料２０に支持された２次元薄膜原子構造２１に照射される。 Incident laser light 11 emitted from the laser light source 10 is reflected by the half mirror 12, collected by the microscope objective lens 13, and applied to the two-dimensional thin film atomic structure 21 supported by the insulating material 20.
これにより発生した絶縁材料２０からのラマン散乱光は、顕微鏡対物レンズ１３に取り込まれ、ハーフミラー１２を透過し、レイリー散乱光の除去フィルター１４、スリット１５を通って分光器１６に導かれる。 The Raman scattered light from the insulating material 20 thus generated is taken into the microscope objective lens 13, passes through the half mirror 12, and is guided to the spectroscope 16 through the Rayleigh scattered light removal filter 14 and the slit 15.
２次元薄膜原子構造２１を透過した絶縁材料２０からのラマン散乱光を検出する際には、顕微鏡対物レンズ１３などの光学系を調整して、２次元薄膜原子構造２１のサイズよりもスポット径を小さくする。 When detecting the Raman scattered light from the insulating material 20 that has passed through the two-dimensional thin film atomic structure 21, the optical system such as the microscope objective lens 13 is adjusted to make the spot diameter larger than the size of the two-dimensional thin film atomic structure 21. Make it smaller.
分光器１６で分光されたラマン散乱光は、検出器１７で検出され、電気信号に変換されて積層数決定部３の外部接続部３０へ入力される。 The Raman scattered light dispersed by the spectroscope 16 is detected by the detector 17, converted into an electric signal, and input to the external connection unit 30 of the stack number determining unit 3.
図１及び図２に示す積層数決定部３は、絶縁材料２０に支持された積層数既知の２次元薄膜原子構造２１に入射レーザー光１１を照射して発生する絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０と、２次元薄膜原子構造２１の積層数ｎとの関係を示す標準曲線に基づいて、積層数未知の２次元薄膜原子構造２１を測定して得た分光ピーク強度比Ｉａ／Ｉ０を標準曲線と照合し、積層数未知の２次元薄膜原子構造２１の積層数を決定する積層数決定機構を構成している。分光ピーク強度比Ｉａ／Ｉ０及びＩｂ／Ｉ０は、測定部２で測定されたＩａ、Ｉｂ及びＩ０に基づいて積層数決定部３で取得される。 The number-of-stacks determining unit 3 shown in FIGS. 1 and 2 has Raman scattering light derived from the insulating material 20 generated by irradiating the incident laser light 11 to the two-dimensional thin film atomic structure 21 having a known number of layers supported by the insulating material 20. Spectral spectrum obtained by measuring the two-dimensional thin film atomic structure 21 with an unknown number of layers, based on a standard curve showing the relationship between the spectral peak intensity ratio I b / I 0 of the film and the number n of layers of the two-dimensional thin film atomic structure 21 The peak intensity ratio I a / I 0 is collated with a standard curve to constitute a stacking number determination mechanism that determines the stacking number of the two-dimensional thin film atomic structure 21 whose stacking number is unknown. The spectral peak intensity ratios I a / I 0 and I b / I 0 are acquired by the stack number determination unit 3 based on I a , I b and I 0 measured by the measurement unit 2.
積層数決定部３は、例えばコンピュータであり、外部接続部３０、制御部３１、記憶部３２、入力部３３、及び出力部３４を備えている。これらはバス３５で接続されている。 The stack number determination unit 3 is, for example, a computer, and includes an external connection unit 30, a control unit 31, a storage unit 32, an input unit 33, and an output unit 34. These are connected by a bus 35.
外部接続部３０は、ケーブル等で外部の測定部２等と接続されている。 The external connection unit 30 is connected to the external measurement unit 2 or the like with a cable or the like.
制御部３１は、各構成要素を駆動制御するためのＣＰＵ、ＲＯＭ、ＲＡＭ等を備えている。 The control unit 31 includes a CPU, a ROM, a RAM, and the like for driving and controlling each component.
記憶部３２は、各構成要素を動作させるためのプログラムが格納されている。また積層数決定装置１を動作させるための積層数決定プログラム及び積層数決定に用いる標準曲線、すなわち絶縁材料２０に支持された積層数既知の２次元薄膜原子構造２１に入射レーザー光１０を照射して発生する絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０と、２次元薄膜原子構造２１の積層数ｎとの関係を示す標準曲線のデータも記憶部３２に格納される。 The storage unit 32 stores a program for operating each component. In addition, the incident laser beam 10 is applied to a two-dimensional thin film atomic structure 21 having a known number of layers supported by the insulating material 20, that is, a standard curve used for determining the number of layers and a standard curve used for determining the number of layers for operating the number-of-stacks determination device 1. Data of a standard curve indicating the relationship between the spectral peak intensity ratio I b / I 0 of the Raman scattered light derived from the insulating material 20 generated in this way and the number n of layers of the two-dimensional thin film atomic structure 21 is also stored in the storage unit 32. .
入力部３３は、測定条件等の入力を行うための、マウス、キーボード等である。 The input unit 33 is a mouse, a keyboard, or the like for inputting measurement conditions and the like.
出力部３４は、測定結果を出力するディスプレイ等である。 The output unit 34 is a display that outputs measurement results.
以上のような構成を備えた積層数決定装置１を用いた絶縁材料２０上の２次元薄膜原子構造２１の積層数決定方法は、次の原理に基づいている。以下、２次元薄膜原子構造２１としてグラフェンを用いた場合を例として説明する。 The method for determining the number of stacked layers of the two-dimensional thin-film atomic structure 21 on the insulating material 20 using the stack number determining apparatus 1 having the above configuration is based on the following principle. Hereinafter, a case where graphene is used as the two-dimensional thin film atomic structure 21 will be described as an example.
図３に示すように、グラフェン２１を転写した絶縁材料２０からのラマン散乱スペクトルを測定すると、グラフェン２１によって、入射レーザー光１１が遮蔽され、かつ、絶縁材料２０からのラマン散乱光４０も遮蔽され、その結果、絶縁材料２０のラマンピーク強度は減少する。 As shown in FIG. 3, when the Raman scattering spectrum from the insulating material 20 to which the graphene 21 is transferred is measured, the incident laser light 11 is shielded by the graphene 21 and the Raman scattered light 40 from the insulating material 20 is also shielded. As a result, the Raman peak intensity of the insulating material 20 decreases.
絶縁材料２０上に転写したグラフェン２１の積層数が増えると、絶縁材料２０に到達する入射レーザー光１１に対する遮光性が高くなり、更に絶縁材料２０からのラマン散乱光４０に対する遮光性も高くなり、その結果、絶縁材料２０のラマンスペクトル強度はより減少する。 As the number of stacked graphenes 21 transferred onto the insulating material 20 increases, the light shielding property against the incident laser light 11 reaching the insulating material 20 increases, and the light shielding property against the Raman scattered light 40 from the insulating material 20 also increases. As a result, the Raman spectrum intensity of the insulating material 20 is further reduced.
単層グラフェンの透過率は、非特許文献１等の公知文献からおよそ９７．７％である。よって、ｎ層グラフェン２１が絶縁材料２０上に転写されている場合、絶縁材料２０上のラマン強度比Ｉｂ／Ｉ０は、原理的には（０．９７７）２ｎとなる。 The transmittance of the single-layer graphene is approximately 97.7% from known documents such as Non-Patent Document 1. Therefore, when the n-layer graphene 21 is transferred onto the insulating material 20, the Raman intensity ratio I b / I 0 on the insulating material 20 is (0.977) 2n in principle.
そこで、これを標準曲線とし、絶縁材料２０に支持された積層数未知のグラフェン２１に入射レーザー光１１を照射して測定を行い、測定された分光ピーク強度Ｉａに基づいて、絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉａ／Ｉ０を取得する。そして分光ピーク強度比Ｉａ／Ｉ０を標準曲線と照合することで、積層数未知のグラフェン２１の積層数を決定することができる。 Therefore, it was the standard curve, was measured by irradiating an incident laser beam 11 in the stacking number of unknown graphene 21 supported by the insulating material 20, based on the measured spectral peak intensity I a, from the insulating material 20 Spectral peak intensity ratio I a / I 0 of Raman scattered light is acquired. Then, by checking the spectral peak intensity ratio I a / I 0 with a standard curve, the number of layers of graphene 21 whose number of layers is unknown can be determined.
実際には、ここに絶縁材料２０の反射率等がラマン散乱光の分光ピーク強度の要因に加わる。そこで、より精密な積層数の評価を行う場合には、予めグラフェン２１の積層数が分かっているもの（０層、単層、ｎ層、∞層）を転写した絶縁材料２０のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０とグラフェン２１の積層数ｎとの関係を、実験的に標準曲線として求めておく。次に、同一の絶縁材料２０を用いて、評価したい積層数未知のグラフェン２１が転写された絶縁材料２０におけるラマン散乱光の分光ピーク強度比Ｉａ／Ｉ０を取得し、標準曲線と照合して積層数を決定する。 Actually, the reflectance of the insulating material 20 is added to the factor of the spectral peak intensity of the Raman scattered light. Therefore, when a more precise evaluation of the number of layers is performed, the Raman scattered light of the insulating material 20 to which the graphene 21 number of layers already known (0 layer, single layer, n layer, ∞ layer) has been transferred is transferred. The relationship between the spectral peak intensity ratio I b / I 0 and the number n of stacked graphenes 21 is experimentally obtained as a standard curve. Next, using the same insulating material 20, the spectral peak intensity ratio I a / I 0 of Raman scattered light in the insulating material 20 to which the graphene 21 with the unknown number of layers to be evaluated is transferred is obtained and collated with a standard curve. To determine the number of layers.
２次元薄膜原子構造２１を支持する絶縁材料２０としては、ラマン散乱のピークが測定できるものであれば特に限定されないが、例えば、ダイヤモンドや、Ｓｉ、ＧａＡｓ（ガリウムヒ素）、窒化ホウ素等の半導体、マイカ等の絶縁体等を挙げることができる。しかし金属の場合は、ラマン活性を示すものであっても、大抵は低温に冷却しないとラマンピークが得られず、そうなると装置も大がかりとなり、またピークの形状は強度が弱くブロードであることから、絶縁材料２０としては、金属以外のラマン活性を示す物質が好ましい。 The insulating material 20 that supports the two-dimensional thin film atomic structure 21 is not particularly limited as long as the peak of Raman scattering can be measured. For example, a semiconductor such as diamond, Si, GaAs (gallium arsenide), boron nitride, An insulator such as mica can be used. However, in the case of metal, even if it shows Raman activity, the Raman peak is usually not obtained unless it is cooled to a low temperature, and then the apparatus becomes large, and the shape of the peak is weak and broad, so The insulating material 20 is preferably a substance exhibiting Raman activity other than metal.
絶縁材料２０の形状は、特に限定されないが、２次元薄膜原子構造２１を支持する平坦面を有するものが好ましい。例えば、絶縁材料２０として基板を用いることができる。 The shape of the insulating material 20 is not particularly limited, but preferably has a flat surface that supports the two-dimensional thin film atomic structure 21. For example, a substrate can be used as the insulating material 20.
また、観察の妨げにならないように、絶縁材料２０は予め、洗浄や酸素プラズマ等で清浄化することが望ましい。ＣＶＤグラフェンやＳｉＣ熱分解エピタキシャル成長グラファイトの場合、機械的な剥離・貼り付けをせずに成長基板をそのまま用いることも可能である。 In addition, it is desirable to clean the insulating material 20 in advance by cleaning, oxygen plasma, or the like so as not to hinder observation. In the case of CVD graphene or SiC pyrolytic epitaxial growth graphite, it is possible to use the growth substrate as it is without mechanical peeling and pasting.
２次元薄膜原子構造２１は、原子の２次元的結合構造、あるいは、それと等価な２次元的電子状態を表面、界面などに有する機能性を持った薄膜物質であり、例えば、グラフェン、六方晶窒化ホウ素（ｈＢＮ）、トポロジカル絶縁体、２次元原子・分子薄膜等が挙げられる。 The two-dimensional thin film atomic structure 21 is a thin film material having a function of having a two-dimensional bonding structure of atoms or an equivalent two-dimensional electronic state on the surface, interface, etc., for example, graphene, hexagonal nitriding Examples thereof include boron (hBN), topological insulator, and two-dimensional atomic / molecular thin film.
グラフェンは、例えば、天然グラファイトを粘着テープで薄く剥がすことによって得られる。グラフェンの原料としては上記の天然グラファイトのほか、ＨＯＰＧ（高配向熱分解グラファイト）、Ｋｉｓｈ（キッシュ）グラファイト、ＣＶＤ（化学気相成長）グラフェン、ＳｉＣ熱分解エピタキシャル成長グラファイト等を用いることができる。 Graphene is obtained, for example, by peeling off natural graphite with an adhesive tape. In addition to the above natural graphite, HOPG (Highly Oriented Pyrolytic Graphite), Kish (Kish) Graphite, CVD (Chemical Vapor Deposition) Graphene, SiC Pyrolytic Epitaxially Grown Graphite, and the like can be used as the raw material for graphene.
次に、積層数決定装置１を用いた２次元薄膜原子構造２１の積層数決定方法について、図４を参照して説明する。 Next, a method for determining the number of stacked layers of the two-dimensional thin film atomic structure 21 using the stack number determining apparatus 1 will be described with reference to FIG.
まず、積層数決定部３の制御部３１は、記憶部３２に格納された積層数決定プログラムを起動し、評価したい積層数未知の２次元薄膜原子構造２１の試料の測定結果と照合するための標準曲線が得られていない場合には、標準曲線を取得する（Ｓ１０１、Ｓ１０２）。 First, the control unit 31 of the stack number determination unit 3 starts the stack number determination program stored in the storage unit 32, and collates it with the measurement result of the sample of the two-dimensional thin film atomic structure 21 whose stack number is unknown. If the standard curve is not obtained, the standard curve is acquired (S101, S102).
なお、標準曲線が既に取得済みの場合は、Ｓ１０２のステップは不要であり、次のＳ１０３に進む。 If the standard curve has already been acquired, step S102 is unnecessary, and the process proceeds to the next S103.
ここで、Ｓ１０２における標準曲線の取得方法について説明する。 Here, the method for obtaining the standard curve in S102 will be described.
この標準曲線は、絶縁材料２０に支持された積層数既知の２次元薄膜原子構造２１に入射レーザー光１１を照射して発生する絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０と、２次元薄膜原子構造２１の積層数ｎとの関係を示すものである。 This standard curve shows the spectral peak intensity ratio I b / I of Raman scattered light derived from the insulating material 20 generated by irradiating the incident laser light 11 to the two-dimensional thin film atomic structure 21 having a known number of layers supported by the insulating material 20. The relationship between 0 and the number n of layers of the two-dimensional thin film atomic structure 21 is shown.
一例では、標準曲線は、２次元薄膜原子構造２１の単層に対する入射レーザー光１１の透過率Ｔと、２次元薄膜原子構造２１の積層数ｎより、絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０をＴ２ｎとする関係式で表わされる。この関係式の原理については図３を参照して上述したとおりである。この例によれば、測定を要せずとも標準曲線を取得することができ、グラフェンの積層数を非常に簡便に決定することができる。 In one example, the standard curve is a spectral peak of Raman scattered light derived from the insulating material 20 based on the transmittance T of the incident laser beam 11 with respect to a single layer of the two-dimensional thin-film atomic structure 21 and the number n of layers of the two-dimensional thin-film atomic structure 21. The intensity ratio I b / I 0 is represented by a relational expression with T 2n . The principle of this relational expression is as described above with reference to FIG. According to this example, a standard curve can be acquired without requiring measurement, and the number of graphene layers can be determined very simply.
なお、グラフェンの透過率はいろいろな方法で求められるが、例えば、ラマン分光法によりグラフェン単層の透過率Ｔを次の方法によって求めることができる。グラフェン単層が配置された絶縁材料２０を用意し、絶縁材料２０由来のラマン散乱光の分光ピーク強度Ｉ１を実験から求める。また、絶縁材料２０のラマン散乱光の分光ピーク強度Ｉ０を実験から求める。そしてＩ１／Ｉ０＝Ｔ２の関係式より、Ｔ＝（Ｉ１／Ｉ０）１／２を得る。よって、グラフェン積層数評価のための関係式は、Ｉｎ／Ｉ０＝Ｔ２ｎ＝｛（Ｉ１／Ｉ０）１／２｝２ｎ＝（Ｉ１／Ｉ０）ｎとなる。この例ではグラフェンを用いた場合について説明したが、他の２次元薄膜原子構造２１と置き換えても同様な式が成り立つ。 Note that the transmittance of graphene can be obtained by various methods. For example, the transmittance T of a graphene single layer can be obtained by the following method by Raman spectroscopy. An insulating material 20 in which a graphene single layer is arranged is prepared, and a spectral peak intensity I 1 of Raman scattered light derived from the insulating material 20 is obtained from an experiment. Further, the spectral peak intensity I 0 of the Raman scattered light of the insulating material 20 is obtained from experiments. Then, T = (I 1 / I 0 ) 1/2 is obtained from the relational expression of I 1 / I 0 = T 2 . Therefore, the relational expression for evaluating the number of graphene stacks is I n / I 0 = T 2n = {(I 1 / I 0 ) 1/2 } 2n = (I 1 / I 0 ) n . In this example, the case where graphene is used has been described, but the same formula holds even if the graphene is replaced with another two-dimensional thin film atomic structure 21.
別の例では、標準曲線は、絶縁材料２０に支持され、それぞれ積層数ｎが異なる積層数既知の２次元薄膜原子構造２１を複数用意し、これに入射レーザー光１１を照射して測定された分光ピーク強度Ｉｂより取得した、絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０に基づいて取得される。上記の例では関係式Ｔ２ｎを標準曲線としたが、実際には、ここに絶縁材料２０の反射率等がラマン散乱光の分光ピーク強度の要因として加わる。そこで、より精密な積層数の評価を行うことが適切な場合には、予め２次元薄膜原子構造２１の積層数が分かっているもの（０層、単層、ｎ層、∞層）を転写した絶縁材料２０におけるラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０と、２次元薄膜原子構造２１の積層数ｎとの関係を、実験的に基づく標準曲線として求めておく。次に、同一の絶縁材料２０を用いて、評価したい積層数未知のグラフェン２１が転写された絶縁材料２０におけるラマン散乱光の分光ピーク強度比Ｉａ／Ｉ０を取得し、標準曲線と照合して積層数を決定する。 In another example, the standard curve was measured by irradiating the incident laser beam 11 with a plurality of two-dimensional thin film atomic structures 21 supported by the insulating material 20 and having a different number of layers n, each having a known number of layers. obtained from the spectral peak intensity I b, is obtained based on the spectral peak intensity ratio I b / I 0 of the Raman scattering light from the insulating material 20. In the above example, the relational expression T2n is a standard curve, but actually, the reflectance of the insulating material 20 is added as a factor of the spectral peak intensity of the Raman scattered light. Therefore, when it is appropriate to evaluate the number of stacked layers more precisely, the one in which the number of stacked layers of the two-dimensional thin film atomic structure 21 is known in advance (0 layer, single layer, n layer, ∞ layer) is transferred. The relationship between the spectral peak intensity ratio I b / I 0 of the Raman scattered light in the insulating material 20 and the number n of layers of the two-dimensional thin film atomic structure 21 is obtained as a standard curve based on experiments. Next, using the same insulating material 20, the spectral peak intensity ratio I a / I 0 of Raman scattered light in the insulating material 20 to which the graphene 21 with the unknown number of layers to be evaluated is transferred is obtained and collated with a standard curve. To determine the number of layers.
ここで、予め２次元薄膜原子構造２１の積層数ｎが分かっているものを転写した絶縁材料２０は、ラマン測定（非特許文献１、２）、光学測定（非特許文献３）等の公知の方法で２次元薄膜原子構造２１の積層数ｎを評価することによって得ることができる。 Here, the insulating material 20 in which the number n of the two-dimensional thin film atomic structure 21 of which the number is known is previously transferred is known, such as Raman measurement (Non-Patent Documents 1 and 2), optical measurement (Non-Patent Document 3), etc. It can be obtained by evaluating the number n of stacked layers of the two-dimensional thin film atomic structure 21 by the method.
例えば、積層数ｎが異なる複数の２次元薄膜原子構造２１を用意し、これらを絶縁材料２０に転写する。絶縁材料２０は積層数未知の２次元薄膜原子構造２１を転写するものと同じ材料を用いる。 For example, a plurality of two-dimensional thin film atomic structures 21 having different stacking numbers n are prepared and transferred to the insulating material 20. As the insulating material 20, the same material as that for transferring the two-dimensional thin film atomic structure 21 with an unknown number of layers is used.
次に、制御部３１は積層数決定プログラムに基づき、ステップＳ１０３と同じ条件にて絶縁材料２０に支持された２次元薄膜原子構造２１に入射レーザー光１１を照射するように指示する。それに基づいて、測定部２は、絶縁材料２０に支持された積層数既知の２次元薄膜原子構造２１に入射レーザー光１１を照射して、絶縁材料２０由来のラマン散乱光の分光ピーク強度Ｉｂを測定する。また、基準として２次元薄膜原子構造２１を配置しない絶縁材料２０由来のラマン散乱光の分光ピーク強度Ｉ０も測定しておく。 Next, the control unit 31 instructs to irradiate the incident laser light 11 to the two-dimensional thin film atomic structure 21 supported by the insulating material 20 under the same conditions as in step S103 based on the stacking number determination program. Based on this, the measuring unit 2 irradiates the incident laser light 11 to the two-dimensional thin-film atomic structure 21 with a known number of layers supported by the insulating material 20, and the spectral peak intensity I b of the Raman scattered light derived from the insulating material 20. Measure. Further, as a reference, the spectral peak intensity I 0 of Raman scattered light derived from the insulating material 20 in which the two-dimensional thin film atomic structure 21 is not disposed is also measured.
制御部３１は、２次元薄膜原子構造２１の積層数ｎと、絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０の関係をプロットして、最小２乗法等の回帰分析でフィッティングすることにより標準曲線を作成し、記憶部３２に保存する。 The control unit 31 plots the relationship between the number n of the two-dimensional thin-film atomic structure 21 and the spectral peak intensity ratio I b / I 0 of the Raman scattered light derived from the insulating material 20, and performs regression analysis such as the least square method. A standard curve is created by fitting and stored in the storage unit 32.
以上の例によれば、より精密な積層数の評価を行うことが可能となる。 According to the above example, it is possible to evaluate the number of stacked layers more precisely.
次のステップとして、積層数未知の２次元薄膜原子構造２１、すなわち積層数を決定したい２次元薄膜原子構造２１を絶縁材料２０上に転写する（Ｓ１０３）。この積層数未知の２次元薄膜原子構造２１を支持する絶縁材料２０は、図１のＸ−Ｙステージ１８の試料台上に配置される。 As the next step, the two-dimensional thin film atomic structure 21 with the unknown number of layers, that is, the two-dimensional thin film atomic structure 21 for which the number of layers is to be determined, is transferred onto the insulating material 20 (S103). The insulating material 20 that supports the two-dimensional thin film atomic structure 21 with the unknown number of layers is disposed on the sample stage of the XY stage 18 in FIG.
次のステップとして、積層数決定部３の制御部３１は、積層数決定プログラムに基づき、所定の条件にて絶縁材料２０に支持された積層数未知の２次元薄膜原子構造２１に入射レーザー光１１を照射するように指示し、レーザー光源１０より入射レーザー光１１を照射する（Ｓ１０４）。 As the next step, the control unit 31 of the stack number determination unit 3 applies the incident laser beam 11 to the two-dimensional thin film atomic structure 21 with the unknown stack number supported by the insulating material 20 under a predetermined condition based on the stack number determination program. And the incident laser beam 11 is irradiated from the laser light source 10 (S104).
次のステップとして、制御部３１は、測定部２（顕微ラマン分光計）の検出部１７を制御して絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉａ／Ｉ０を取得する（Ｓ１０５）。 As the next step, the control unit 31 controls the detection unit 17 of the measurement unit 2 (microscopic Raman spectrometer) to acquire the spectral peak intensity ratio I a / I 0 of the Raman scattered light derived from the insulating material 20 (S105). ).
次のステップとして、分光ピーク強度比Ｉａ／Ｉ０を標準曲線と照合し、積層数未知の２次元薄膜原子構造２１の積層数を決定する（Ｓ１０６）。 As the next step, the spectral peak intensity ratio I a / I 0 is collated with a standard curve to determine the number of layers of the two-dimensional thin film atomic structure 21 whose number of layers is unknown (S106).
具体的には、標準曲線における、絶縁材料２０由来のラマン散乱光の分光ピーク強度比Ｉａ／Ｉ０に対応する積層数を２次元薄膜原子構造２１の積層数とする。 Specifically, the number of layers corresponding to the spectral peak intensity ratio I a / I 0 of Raman scattered light derived from the insulating material 20 in the standard curve is defined as the number of layers of the two-dimensional thin film atomic structure 21.
本実施形態によれば、グラフェン等の２次元薄膜原子構造２１の遮光効果を利用して、２次元薄膜原子構造２１を支持する絶縁基板２０由来のラマン散乱強度比を取得することで、２次元薄膜原子構造２１の積層数を簡便かつ正確に決定することができる。測定に必要なものは顕微ラマン分光計のみで、その他の大がかりな装置、高度な知識と熟練された技術を要しない。そして常温、大気圧下での測定でも積層数評価が可能で、高真空での測定、試料サイズなど、測定条件の厳しい制限がない。 According to the present embodiment, the light scattering effect of the two-dimensional thin film atomic structure 21 such as graphene is used to obtain the Raman scattering intensity ratio derived from the insulating substrate 20 that supports the two-dimensional thin film atomic structure 21, thereby The number of stacked thin-film atomic structures 21 can be determined easily and accurately. All that is required for the measurement is a microscopic Raman spectrometer, which does not require any other large-scale equipment, advanced knowledge and skill. The number of stacked layers can be evaluated even at room temperature and atmospheric pressure, and there are no strict restrictions on measurement conditions such as high vacuum measurement and sample size.
また本実施形態によれば、単層から３０層まで、広範囲にわたる積層数評価が可能である。そして、絶縁材料２０の種類による制限が少なく、例えばグラフェン等の２次元薄膜原子構造２１とのコントラストが小さい絶縁材料２０でも積層数が評価できる。 Further, according to the present embodiment, it is possible to evaluate the number of stacked layers over a wide range from a single layer to 30 layers. The number of stacked layers can be evaluated even with the insulating material 20 having a small contrast with the two-dimensional thin-film atomic structure 21 such as graphene, which is less limited by the type of the insulating material 20.
以下に、実施例により本発明をさらに詳しく説明するが、本発明はこれらの実施例に何ら限定されるものではない。 EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
顕微ラマン分光計としてJobin Yvon社製レーザーラマン分光測定システムT64000を用いた。 The laser Raman spectrometer T64000 manufactured by Jobin Yvon was used as a micro-Raman spectrometer.
絶縁材料としてダイヤモンドアンビルを用い、図５に示すように上面にグラフェンを転写して測定を行った。(i)はダイヤモンドアンビルのみ、(ii)はｎ層グラフェンを転写した場合を示す。 A diamond anvil was used as an insulating material, and measurement was performed by transferring graphene to the upper surface as shown in FIG. (i) shows only the diamond anvil, and (ii) shows the case of transferring the n-layer graphene.
図６は、ダイヤモンドアンビルに転写されたｎ層グラフェンの光学顕微鏡写真である。写真中の(1)〜(5)は、積層数の異なる５種類のグラフェンのサンプルであり、これらは別途にグラフェンのラマンスペクトル（２Ｄバンド）を利用して積層数を求めた（非特許文献１）。 FIG. 6 is an optical micrograph of n-layer graphene transferred to a diamond anvil. (1) to (5) in the photograph are five types of graphene samples with different numbers of layers, and these were separately obtained using the Raman spectrum (2D band) of graphene (non-patent literature) 1).
これらの積層数の異なる５種類のグラフェンを転写したダイヤモンドアンビルについて、ダイヤモンドアンビル上面に対して入射レーザー光（波長５１４．５ｎｍ）を照射し、ダイヤモンドからのラマン散乱光を検出して、ダイヤモンド（１次）のラマンスペクトルを測定した。 The diamond anvil onto which these five types of graphene with different numbers of layers are transferred is irradiated with incident laser light (wavelength 514.5 nm) on the diamond anvil upper surface, and the Raman scattered light from the diamond is detected, and diamond (1 Next) Raman spectrum was measured.
図７は、(1)〜(5)のグラフェンを転写したダイヤモンドと、ダイヤモンドアンビルのみ（ＢＧ）のラマンスペクトルである。このように、ｎ層グラフェンを転写した(1)〜(5)ののサンプルでは、ダイヤモンドアンビルのみのＢＧに比べてラマン散乱光の分光ピーク強度は減少し、ダイヤモンドアンビル上のｎ層グラフェンによって、入射レーザー光と反射光のラマン散乱光が遮蔽されることを示唆した。 FIG. 7 is a Raman spectrum of diamond transferred with graphene (1) to (5) and diamond anvil alone (BG). Thus, in the samples of (1) to (5) to which n-layer graphene was transferred, the spectral peak intensity of Raman scattered light was reduced compared to BG with only diamond anvil, and the n-layer graphene on the diamond anvil It is suggested that the incident laser beam and the reflected Raman scattered light are shielded.
表１に、図７の(1)〜(5)の各ピークの強度Ｉｎと、ダイヤモンドのみのピークの強度Ｉ０に対する比（Ｉｎ／Ｉ０）の結果を示す。各ピークの強度は関数のフィッティングから求めた。 Table 1 shows the respective peak intensity I n of (1) to (5) in FIG. 7, the results of the ratio of the intensity I 0 of the peak of diamond only (I n / I 0). The intensity of each peak was obtained from function fitting.
単層グラフェンの透過率は、文献値（非特許文献１等）からおよそ９７．７％である。よって、ｎ層グラフェンが基板上に転写されている場合、基板のラマン強度比Ｉｎ／Ｉ０は、原理的には（０．９７７）２ｎとなる。この数式と、上記のプロットとを図８に対比した。 The transmittance of the single-layer graphene is approximately 97.7% from the literature value (Non-Patent Document 1 etc.). Therefore, when the n-layer graphene is transferred onto the substrate, the Raman intensity ratio I n / I 0 of the substrate is (0.977) 2n in principle. This mathematical expression was compared with the above plot in FIG.
図８に示すように、ダイヤモンドの１次ピークを用いた強度比−積層数のプロットは、上記数式を再現していた。 As shown in FIG. 8, the plot of the intensity ratio-number of stacks using the primary peak of diamond reproduced the above formula.
以上の結果より、予めグラフェンの積層数が分かっているもの（０層、１層、ｎ層、∞層）を転写した基板のラマンスペクトル強度比（基板の強度で割った値）Ｉｎ／Ｉ０と積層数ｎとの関係を実験的に求めておき、回帰分析によって標準曲線を得ることで、同一基板を用いて層数未知のグラフェンを転写し基板のラマンスペクトルを測定し、標準曲線と照合することで、積層数未知のグラフェンの積層数を精度良く決定できることが分かった。 From the above results, the Raman spectral intensity ratio (value divided by the substrate strength) I n / I of the substrate onto which the graphene layer number already known (0 layer, 1 layer, n layer, ∞ layer) was transferred. By experimentally determining the relationship between 0 and the number n of layers, and obtaining a standard curve by regression analysis, the graphene with an unknown number of layers is transferred using the same substrate, and the Raman spectrum of the substrate is measured. By collating, it was found that the number of graphene layers with unknown number of layers can be determined with high accuracy.
更に、単層グラフェンの透過率に基づくシンプルな式を標準曲線として、積層数未知のグラフェンが転写された基板のラマンスペクトルを測定し、そのピーク強度比（基板の強度で割った値）を標準曲線と照合することで、積層数未知のグラフェンの積層数を精度良く決定できることが分かった。 Furthermore, using a simple equation based on the transmittance of single-layer graphene as a standard curve, the Raman spectrum of the substrate onto which the graphene with an unknown number of layers is transferred is measured, and the peak intensity ratio (value divided by the substrate strength) is standard. It was found that the number of graphene layers with unknown number of layers can be determined with high accuracy by matching with the curve.
１ 積層数決定装置
２ 測定部（顕微ラマン分光計）
３ 積層数決定部（積層数決定機構）
１０ レーザー光源
１１ 入射レーザー光
１２ ハーフミラー
１３ 顕微鏡対物レンズ
１４ レイリー散乱光の除去フィルター
１５ スリット
１６ 分光器
１７ 検出器
１８ Ｘ−Ｙステージ
２０ 絶縁材料
２１ ２次元薄膜原子構造
３０ 外部接続部
３１ 制御部
３２ 記憶部
３３ 入力部
３４ 出力部
３５ バス
４０ 絶縁材料からのラマン散乱光
1 Stack number determination device 2 Measuring unit (micro Raman spectrometer)
3 Stack number determination unit (Stack number determination mechanism)
DESCRIPTION OF SYMBOLS 10 Laser light source 11 Incident laser beam 12 Half mirror 13 Microscope objective lens 14 Rayleigh scattered light removal filter 15 Slit 16 Spectrometer 17 Detector 18 XY stage 20 Insulating material 21 Two-dimensional thin film atomic structure 30 External connection part 31 Control part 32 Storage unit 33 Input unit 34 Output unit 35 Bus 40 Raman scattered light from insulating material
Claims (5)
前記絶縁材料に支持された積層数未知の２次元薄膜原子構造に入射レーザー光を照射し、前記絶縁材料由来のラマン散乱光の分光ピーク強度比Ｉａ／Ｉ０ （Ｉ ａ とＩ ０ の定義はそれぞれ下記に示す）を取得するための測定を行う顕微ラマン分光計と、
前記絶縁材料に支持された積層数既知の２次元薄膜原子構造に前記入射レーザー光を照射して発生する前記絶縁材料由来のラマン散乱光の分光ピーク強度比Ｉｂ／Ｉ０ （Ｉ ｂ の定義は下記に示す）と、前記２次元薄膜原子構造の積層数ｎとの関係を示し、且つ、前記積層数既知の２次元薄膜原子構造の単層に対する前記入射レーザー光の透過率Ｔ及び積層数ｎより、次の関係式：
Ｉ ｂ ／Ｉ ０ ＝Ｔ ２ｎ
で表わされる標準曲線に基づいて、前記分光ピーク強度比Ｉａ／Ｉ０を前記標準曲線と照合し、前記積層数未知の２次元薄膜原子構造の積層数を決定する積層数決定機構とを備えることを特徴とする２次元薄膜原子構造の積層数決定装置。
Ｉ ａ は前記絶縁材料に支持された積層数未知の２次元薄膜原子構造に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、且つ、顕微ラマン分光計によって測定した絶対強度であり、
Ｉ ｂ は前記絶縁材料に支持された積層数既知の２次元薄膜原子構造に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、且つ、顕微ラマン分光計によって測定した絶対強度であり、
Ｉ ０ は２次元薄膜原子構造を配置しない前記絶縁材料に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、且つ、顕微ラマン分光計によって測定した絶対強度である。 A device for determining the number of layers of a two-dimensional thin-film atomic structure on a Raman-active insulating material,
The two-dimensional thin film atomic structure with an unknown number of layers supported by the insulating material is irradiated with incident laser light, and the spectral peak intensity ratio I a / I 0 ( definition of I a and I 0 of Raman scattered light derived from the insulating material) Is a micro-Raman spectrometer that performs measurements to obtain
Spectral peak intensity ratios I b / I 0 ( definition of I b) of Raman scattered light derived from the insulating material generated by irradiating the incident laser light onto a two-dimensional thin film atomic structure having a known number of layers supported by the insulating material the below) shows the relationship between the stacking number n of the two-dimensional thin atomic structure, and the incident laser light transmittance T and laminated for a single layer of the lamination number known two-dimensional thin atomic structure From the number n, the following relational expression:
I b / I 0 = T 2n
The spectral peak intensity ratio I a / I 0 is collated with the standard curve on the basis of the standard curve represented by : and a stacking number determination mechanism for determining the stacking number of the two-dimensional thin film atomic structure with the unknown stacking number is provided. An apparatus for determining the number of stacked layers of a two-dimensional thin-film atomic structure.
I a is a spectral peak intensity of Raman scattered light derived from an insulating material, measured by irradiating incident laser light onto a two-dimensional thin film atomic structure with an unknown number of layers supported by the insulating material, and a microscopic Raman spectrometer Is the absolute intensity measured by
I b is a spectral peak intensity of Raman scattered light derived from an insulating material, measured by irradiating incident laser light onto a two-dimensional thin film atomic structure with a known number of layers supported by the insulating material, and a microscopic Raman spectrometer Is the absolute intensity measured by
I 0 is the spectral peak intensity of the Raman scattered light derived from the insulating material, measured by irradiating the insulating material with no two-dimensional thin film atomic structure irradiated with incident laser light, and the absolute intensity measured by a microscopic Raman spectrometer It is.
前記絶縁材料に支持された積層数既知の２次元薄膜原子構造に入射レーザー光を照射して発生する前記絶縁材料由来のラマン散乱光の分光ピーク強度比ＩSpectral peak intensity ratio I of Raman scattered light derived from the insulating material generated by irradiating incident laser light onto a two-dimensional thin film atomic structure having a known number of layers supported by the insulating material ｂb ／Ｉ/ I ０0 （Ｉ(I ｂb とＩAnd I ０0 の定義はそれぞれ下記に示す）と、前記２次元薄膜原子構造の積層数ｎとの関係を示し、且つ、前記積層数既知の２次元薄膜原子構造の単層に対する前記入射レーザー光の透過率Ｔ及び積層数ｎより、次の関係式：And the number of stacked layers of the two-dimensional thin film atomic structure n, and the transmittance T of the incident laser light with respect to a single layer of the two-dimensional thin film atomic structure of which the number of stacked layers is known. And from the number n of layers, the following relational expression:
ＩI ｂb ／Ｉ/ I ０0 ＝Ｔ= T ２ｎ2n
で表わされる標準曲線を取得する工程；Obtaining a standard curve represented by:
前記絶縁材料に支持された積層数未知の２次元薄膜原子構造に前記入射レーザー光を照射し、前記絶縁材料由来のラマン散乱光の分光ピーク強度比ＩThe incident laser beam is irradiated onto a two-dimensional thin film atomic structure with an unknown number of layers supported by the insulating material, and a spectral peak intensity ratio I of Raman scattered light derived from the insulating material ａa ／Ｉ/ I ０0 （Ｉ(I ａa の定義は下記に示す）を取得する工程；及びThe definition of is given below); and
前記分光ピーク強度比ＩThe spectral peak intensity ratio I ａa ／Ｉ/ I ０0 を前記標準曲線と照合し、前記積層数未知の２次元薄膜原子構造の積層数を決定する工程。And the standard curve to determine the number of layers of the two-dimensional thin film atomic structure whose number of layers is unknown.
ＩI ａa は前記絶縁材料に支持された積層数未知の２次元薄膜原子構造に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、且つ、顕微ラマン分光計によって測定した絶対強度であり、Is the spectral peak intensity of the Raman scattered light derived from the insulating material, measured by irradiating the two-dimensional thin film atomic structure with unknown number of layers supported by the insulating material with incident laser light, and measured with a microscopic Raman spectrometer Absolute strength,
ＩI ｂb は前記絶縁材料に支持された積層数既知の２次元薄膜原子構造に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、且つ、顕微ラマン分光計によって測定した絶対強度であり、Is the spectral peak intensity of the Raman scattered light derived from the insulating material, measured by irradiating the two-dimensional thin film atomic structure with a known number of layers supported by the insulating material with incident laser light, and measured with a microscopic Raman spectrometer Absolute strength,
ＩI ０0 は２次元薄膜原子構造を配置しない前記絶縁材料に入射レーザー光を照射して測定した、絶縁材料由来のラマン散乱光の分光ピーク強度であり、且つ、顕微ラマン分光計によって測定した絶対強度である。Is the spectral peak intensity of the Raman scattered light derived from the insulating material, measured by irradiating the insulating material with no two-dimensional thin-film atomic structure irradiated with incident laser light, and the absolute intensity measured by a microscopic Raman spectrometer .
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