JP2021041671A - Complex and method for producing complex - Google Patents
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Abstract
【課題】幅広い濃度領域で電子濃度が制御でき、大気中で長時間安定するＮ型ドープされた炭素系薄膜を提供する。【解決手段】炭素系薄膜を備える複合体の製造方法は、光塩基発生剤層形成工程と、紫外光照射工程を有する。光塩基発生剤層形成工程では、紫外光を透過する基材と、基材上に設けられた炭素系薄膜とを有する積層体の炭素系薄膜上に、光塩基発生剤層を形成する。紫外光照射工程では、積層体の基材側から紫外光を照射する。複合体は、Ｎ型ドープされた炭素系薄膜と、炭素系薄膜上に設けられ、光塩基発生剤に由来する塩基の誘導体で、炭素系薄膜のＮ型ドーパントである塩基誘導体と、炭素系薄膜上に設けられ、光塩基発生剤から塩基が脱離した物質に由来する酸誘導体を有する。【選択図】図８PROBLEM TO BE SOLVED: To provide an N-type doped carbon-based thin film whose electron concentration can be controlled in a wide concentration region and which is stable for a long time in the atmosphere. A method for producing a composite containing a carbon-based thin film includes a photobase generator layer forming step and an ultraviolet light irradiation step. In the photobase generator layer forming step, a photobase generator layer is formed on a carbon-based thin film of a laminate having a base material that transmits ultraviolet light and a carbon-based thin film provided on the base material. In the ultraviolet light irradiation step, ultraviolet light is irradiated from the base material side of the laminated body. The composite is an N-type doped carbon-based thin film, a base derivative provided on the carbon-based thin film and derived from a photobase generator, a base derivative which is an N-type dopant of the carbon-based thin film, and a carbon-based thin film. It has an acid derivative provided above and derived from a substance from which the base has been desorbed from the photobase generator. [Selection diagram] FIG. 8
Description
本願は、幅広い濃度領域で電子濃度が制御でき、大気中で長時間安定するＮ型ドープされた炭素系薄膜を含む複合体と、この複合体の製造方法に関する。 The present application relates to a complex containing an N-type doped carbon-based thin film whose electron concentration can be controlled in a wide concentration range and is stable for a long time in the atmosphere, and a method for producing this complex.
グラフェンを用いた高感度・高速のセンサーまたは高周波デバイスを実用化するためには、グラフェンに欠陥を与えずに、キャリアをＰ型／Ｎ型で自在に制御し安定化する必要がある。グラフェンはＰ型を示すことがよく知られているが、グラフェンのＮ型ドープ（電子ドープ）を大気中で長期間安定化する方法は確立されていない。大気中で長時間安定するグラフェンのＮ型ドープは、特に要求されている技術の１つである。 In order to put a high-sensitivity, high-speed sensor or high-frequency device using graphene into practical use, it is necessary to freely control and stabilize the carrier in P-type / N-type without giving defects to graphene. It is well known that graphene exhibits P-type, but a method for stabilizing graphene N-type doping (electron doping) in the atmosphere for a long period of time has not been established. Graphene N-type doping, which is stable in the atmosphere for a long time, is one of the particularly required techniques.
特許文献１には、ＴＴＦ等の電子供与性有機分子をグラフェン表面に成膜することによって、グラフェンをＮ型ドープする方法が記載されている。この方法によれば、１０１３ ｃｍ−２以上の電子濃度を有するＮ型ドープされたグラフェンが得られる。しかしながら、このＮ型ドープされたグラフェンは、大気中で長期間安定するか不明である。また、このＮ型ドープされたグラフェンは、１０１３ｃｍ−２未満の電子濃度領域で、電子濃度を自在に制御できない。
本願の課題は、幅広い濃度領域で電子濃度が制御でき、大気中で長時間安定するＮ型ドープされた炭素系薄膜を含む複合体を提供することである。 An object of the present application is to provide a complex containing an N-type doped carbon-based thin film whose electron concentration can be controlled in a wide concentration range and which is stable for a long time in the atmosphere.
本願の複合体は、Ｎ型ドープされた炭素系薄膜と、炭素系薄膜上に設けられ、光塩基発生剤に由来する塩基の誘導体で、正電荷を帯びた塩基誘導体と、炭素系薄膜上に設けられ、光塩基発生剤から塩基が脱離した物質に由来する酸誘導体とを有する。 The composite of the present application is an N-type doped carbon-based thin film and a base derivative provided on the carbon-based thin film and derived from a photobase generator, which is a positively charged base derivative and a carbon-based thin film. It is provided and has an acid derivative derived from a substance from which a base has been desorbed from a photobase generator.
本願の複合体の製造方法は、紫外光を透過する基材と、基材上に設けられた炭素系薄膜とを有する積層体の炭素系薄膜上に、光塩基発生剤層を形成する光塩基発生剤層形成工程と、積層体の基材側から、炭素系薄膜に紫外光を照射する紫外光照射工程を有する。 The method for producing a composite of the present application is a photobase that forms a photobase generator layer on a carbon-based thin film of a laminate having a base material that transmits ultraviolet light and a carbon-based thin film provided on the base material. It has a generator layer forming step and an ultraviolet light irradiation step of irradiating a carbon-based thin film with ultraviolet light from the base material side of the laminate.
本願によれば、幅広い濃度領域で電子濃度が制御でき、大気中で長時間安定するＮ型ドープされた炭素系薄膜を含む複合体が得られる。 According to the present application, a composite containing an N-type doped carbon-based thin film whose electron concentration can be controlled in a wide concentration range and which is stable for a long time in the atmosphere can be obtained.
グラフェンの正孔濃度は、大気中で吸着した酸素分子または水分子、および基材の影響を受けて、１０１３ｃｍ−２程度と高い状態である場合が多い。本願の発明者らは、グラフェンへの光塩基発生剤塗布と紫外光照射のプロセスが、グラフェンの正孔濃度の抑制に使用できるだけでなく、光反応進行によってグラフェンをＮ型ドープできると考え、各種実験を行った。その結果、Ｓｅｅｂｅｃｋ係数およびＨａｌｌ係数の符号変化で、着想どおりにグラフェンがＮ型ドープされていることを確認した。 The hole concentration of graphene is often as high as 10 13 cm- 2 due to the influence of oxygen molecules or water molecules adsorbed in the atmosphere and the base material. The inventors of the present application consider that the process of applying a photobase generator to graphene and irradiating it with ultraviolet light can be used not only for suppressing the hole concentration of graphene but also for N-type doping of graphene by the progress of the photoreaction. An experiment was conducted. As a result, it was confirmed that graphene was N-type doped as conceived by the sign changes of the Seebeck coefficient and the Hall coefficient.
さらに、このグラフェンのＮ型ドープ状態は、大気中で２か月経過した後も安定していること、キャリア移動度が光塩基発生剤塗布前の２〜４倍に増加し、ＰＥＴ基材上のグラフェンとしては非常に高いキャリア移動度を示すこと、および紫外光照射による欠陥形成がないことなども発見した。この長期安定性は、光塩基発生剤のＮ型ドーパントの対となる非イオン化（不活性）分子が、Ｎ型ドープされたグラフェンに空気中の酸素または水分等が侵入するのを防ぐ保護剤の役割をしているからだと考えた。さらに、光の照射量によって、Ｐ型からＮ型に至る１０１３ｃｍ−２未満のキャリア濃度を任意に制御できることもわかった。 Furthermore, the N-type doped state of graphene is stable even after 2 months have passed in the atmosphere, the carrier mobility has increased 2 to 4 times that before the application of the photobase generator, and the graphene is on the PET substrate. It was also found that graphene shows extremely high carrier mobility and that there is no defect formation due to ultraviolet light irradiation. This long-term stability is a protective agent that prevents non-ionized (inactive) molecules that are paired with the N-type dopant of the photobase generator from entering the N-type doped graphene with oxygen or water in the air. I thought it was because I was playing a role. Furthermore, it was also found that the carrier concentration of less than 10 13 cm- 2 from P-type to N-type can be arbitrarily controlled by the amount of light irradiation.
本願の実施形態の複合体は、炭素系薄膜と、塩基誘導体と、酸誘導体を備えている。炭素系薄膜は、主成分が炭素であり、厚さが０．２４ｎｍ以上０．６６ｎｍ以下の膜である。炭素系薄膜としては、単層グラフェン、２層グラフェン、および２層グラフェン中に部分的に単層グラフェンの領域が混在するグラフェンが挙げられる。光透過率測定によって算出した層数の平均値は、単層グラフェンで０．８以上１．２以下、２層グラフェンで１．８以上２．２以下、２層グラフェン中に部分的に単層グラフェンの領域が混在するグラフェンで０．８以上２．２以下である。 The complex of the embodiment of the present application includes a carbon-based thin film, a base derivative, and an acid derivative. The carbon-based thin film is a film in which the main component is carbon and the thickness is 0.24 nm or more and 0.66 nm or less. Examples of the carbon-based thin film include single-layer graphene, double-layer graphene, and graphene in which a region of single-layer graphene is partially mixed in the double-layer graphene. The average value of the number of layers calculated by light transmittance measurement is 0.8 or more and 1.2 or less for single-layer graphene, and 1.8 or more and 2.2 or less for two-layer graphene. Graphene in which the graphene region is mixed is 0.8 or more and 2.2 or less.
本願の実施形態の炭素系薄膜はＮ型ドープされている。光塩基発生剤に由来する塩基は、炭素系薄膜のＮ型ドーパントである。塩基誘導体は、光塩基発生剤に由来する塩基の誘導体である。つまり、塩基誘導体は、光塩基発生剤に紫外光が照射されて発生した塩基が、炭素系薄膜に電子を供与して、正電荷を帯びた物質である。光塩基発生剤は、紫外光が照射されると塩基を発生する。紫外光は波長１０ｎｍ〜４００ｎｍの光である。 The carbon-based thin film of the embodiment of the present application is N-type doped. The base derived from the photobase generator is an N-type dopant in a carbon-based thin film. A base derivative is a derivative of a base derived from a photobase generator. That is, the base derivative is a positively charged substance in which the base generated by irradiating the photobase generator with ultraviolet light donates electrons to the carbon-based thin film. Photobase generators generate bases when irradiated with ultraviolet light. Ultraviolet light is light having a wavelength of 10 nm to 400 nm.
光塩基発生剤としては、２−（９−オキソキサンテン−２−イル）プロピオン酸１，５，７−トリアザビシクロ［４．４．０］デカ−５−エン、１，２−ジシクロヘキシル−４，４，５，５−テトラメチルビグアニジウムｎ−ブチルトリフェニルボラート、および１，２−ジイソプロピル−３−［ビス（ジメチルアミノ）メチレン］グアニジウム２−（３−ベンゾイルフェニル）プロピオナートなどが挙げられ、いずれも市販品として入手できる。光塩基発生剤から発生した塩基および塩基誘導体は炭素系薄膜上に設けられている。この塩基および塩基誘導体は、塩基が炭素系薄膜のＮ型ドーパントとして機能できれば、炭素系薄膜に接していても、酸誘導体または他の物質を介して炭素系薄膜上に設けられていてもよい。
Examples of photobase generators include 2- (9-oxoxanthen-2-yl)
酸誘導体は、光塩基発生剤から塩基が脱離した物質に由来する。つまり、酸誘導体は、光塩基発生剤に紫外光が照射されて塩基が発生し、発生した塩基が光塩基発生剤から脱離したときに残った物質自体、この物質からＣＯ２などの簡単な分子が抜けたもの、この物質にＨ＋などの簡単な化学種が付加したもの、またはこの物質の化学構造がそのまま変化したものである。 The acid derivative is derived from a substance from which the base has been eliminated from the photobase generator. In other words, the acid derivative is a simple substance such as CO 2 from the substance itself that remains when the photobase generator is irradiated with ultraviolet light to generate a base and the generated base is desorbed from the photobase generator. The molecule is missing, the substance is added with a simple chemical species such as H + , or the chemical structure of this substance is changed as it is.
酸誘導体は炭素系薄膜上に設けられている。酸誘導体は、炭素系薄膜に接していても、塩基、塩基誘導体または他の物質を介して炭素系薄膜上に設けられていてもよい。実施形態の複合体は、紫外光を透過する基材をさらに備え、炭素系薄膜が基材上に設けられていてもよい。基材と、基材上の炭素系薄膜と、炭素系薄膜上の光塩基発生剤を備える多層構造体の基材側から紫外線を照射すれば、実施形態の複合体が簡易に製造できるからである。 The acid derivative is provided on the carbon-based thin film. The acid derivative may be in contact with the carbon-based thin film or may be provided on the carbon-based thin film via a base, a base derivative or another substance. The complex of the embodiment may further include a base material that transmits ultraviolet light, and a carbon-based thin film may be provided on the base material. This is because the composite of the embodiment can be easily produced by irradiating ultraviolet rays from the base material side of the base material, the carbon-based thin film on the base material, and the base material side of the multilayer structure including the photobase generator on the carbon-based thin film. is there.
本願の実施形態の複合体の製造方法は、光塩基発生剤層形成工程と、光塩基発生剤層形成工程後の紫外光照射工程を備えている。光塩基発生剤層形成工程では、積層体の表面に光塩基発生剤層を形成する。積層体は、基材と、基材上に設けられた炭素系薄膜を備えている。光塩基発生剤層は、積層体の表面のうち、炭素系薄膜上に形成される。基材は紫外光を透過する。「紫外光を透過する」とは、その物を介して光塩基発生剤に紫外光を照射したときに、光塩基発生剤が塩基を発生する程度の紫外光透過性を有することをいう。なお、「紫外光を照射する」は、紫外光を含有する光を照射することを意味し、紫外光以外の光も含まれる光を照射することを含む。 The method for producing the composite of the embodiment of the present application includes a photobase generator layer forming step and an ultraviolet light irradiation step after the photobase generator layer forming step. In the photobase generator layer forming step, a photobase generator layer is formed on the surface of the laminate. The laminate includes a base material and a carbon-based thin film provided on the base material. The photobase generator layer is formed on a carbon-based thin film on the surface of the laminate. The base material transmits ultraviolet light. "Transmitting ultraviolet light" means that the photobase generator has ultraviolet light transmittance to the extent that the photobase generator generates a base when the photobase generator is irradiated with ultraviolet light through the object. In addition, "irradiating ultraviolet light" means irradiating light containing ultraviolet light, and includes irradiating light including light other than ultraviolet light.
光塩基発生剤層形成工程は、弾性体、例えばジメチルポリシロキサン（ＰＤＭＳ）またはポリイミドフィルムの表面に形成した光塩基発生剤層を、積層体の表面に転写する過程を備えていることが好ましい。この過程により、炭素系薄膜表面に光塩基発生剤が均一かつ十分に塗布される。このため、光塩基発生剤の光反応によるＮ型ドーピングの効果が炭素系薄膜上で均一に与えられるとともに、炭素系薄膜表面に存在する光塩基発生剤が不十分の場合に空気または水分が炭素系薄膜に侵入してＮ型ドーピングの効果を損ねることを防止できる。 The photobase generator layer forming step preferably includes a step of transferring the photobase generator layer formed on the surface of an elastic body such as dimethylpolysiloxane (PDMS) or a polyimide film to the surface of the laminate. By this process, the photobase generator is uniformly and sufficiently applied to the surface of the carbon-based thin film. Therefore, the effect of N-type doping by the photoreaction of the photobase generator is uniformly given on the carbon-based thin film, and when the photobase generator present on the surface of the carbon-based thin film is insufficient, the air or water is carbon. It is possible to prevent the system thin film from invading and impairing the effect of N-type doping.
紫外光照射工程では、積層体の基材側から紫外光を照射する。すなわち、基材に紫外光を照射して、基材を透過した紫外光が炭素系薄膜に照射されるようにする。炭素系薄膜は薄いので、基材を介して炭素系薄膜に照射された紫外光は、炭素系薄膜上に形成された光塩基発生剤に届く。光塩基発生剤に届いた紫外光によって、光塩基発生剤は塩基を発生する。この塩基は、構造変化して炭素系薄膜に電子を供与し、さらに塩基誘導体となる。つまり、この塩基は、炭素系薄膜のＮ型ドーパントとして機能する。 In the ultraviolet light irradiation step, ultraviolet light is irradiated from the base material side of the laminated body. That is, the base material is irradiated with ultraviolet light so that the ultraviolet light transmitted through the base material is irradiated to the carbon-based thin film. Since the carbon-based thin film is thin, the ultraviolet light irradiated to the carbon-based thin film through the base material reaches the photobase generator formed on the carbon-based thin film. The ultraviolet light that reaches the photobase generator causes the photobase generator to generate a base. This base undergoes a structural change to donate electrons to the carbon-based thin film, and further becomes a base derivative. That is, this base functions as an N-type dopant for the carbon-based thin film.
また、積層体の基材側から紫外光を照射することによって、炭素系薄膜と光塩基発生剤の境界で塩基が多く発生し、炭素系薄膜のＮ型ドープを促進する。塩基誘導体は、正電荷を帯びており、安定化された状態で炭素系薄膜上に存在する。なお、光塩基発生剤から塩基が発生すると、光塩基発生剤から塩基が脱離した物質に由来する酸誘導体も、炭素系薄膜上に存在する。 Further, by irradiating ultraviolet light from the base material side of the laminate, a large amount of bases are generated at the boundary between the carbon-based thin film and the photobase generator, and N-type doping of the carbon-based thin film is promoted. The base derivative is positively charged and exists on the carbon-based thin film in a stabilized state. When a base is generated from the photobase generator, an acid derivative derived from a substance from which the base is desorbed from the photobase generator also exists on the carbon-based thin film.
なお、炭素系薄膜表面に形成された光塩基発生剤に炭素系薄膜側から紫外光が照射された場合、炭素系薄膜の表面近傍で光反応が完了して塩基と酸誘導体が生成する領域（光反応領域）と、光反応領域の上に堆積し、紫外光と未反応の領域（未反応領域）とが存在する場合もある（図８参照）。光反応領域では、光塩基発生剤は、炭素系薄膜に電子を供与して、炭素系薄膜をＮ型導電体にできる塩基と、不活性な酸誘導体に変化している。なお、塩基の少なくとも一部は、炭素系薄膜をＮ型導電体にした後に、塩基誘導体として炭素系薄膜上に存在する。 When the photobase generator formed on the surface of the carbon-based thin film is irradiated with ultraviolet light from the carbon-based thin film side, the region where the photoreaction is completed and the base and the acid derivative are generated near the surface of the carbon-based thin film ( There may be a photoreactive region) and an ultraviolet light and an unreacted region (unreacted region) deposited on the photoreactive region (see FIG. 8). In the photoreactive region, the photobase generator is transformed into a base that can donate electrons to the carbon-based thin film to make the carbon-based thin film an N-type conductor, and an inactive acid derivative. At least a part of the base is present on the carbon-based thin film as a base derivative after the carbon-based thin film is made into an N-type conductor.
この塩基、塩基誘導体、および酸誘導体は、空気中の酸素または水分等が炭素系薄膜表面に侵入することを防いで、炭素系薄膜のＮ型状態が損なわれるのを抑制する。加えて、未反応領域がある場合、未反応領域も、空気中の酸素または水分等が光反応領域および炭素系薄膜表面に侵入することを防いで、炭素系薄膜のＮ型状態が損なわれるのを抑制する。このため、塩基、塩基誘導体、および酸誘導体の上に、光塩基発生剤をさらに有する複合体では、炭素系薄膜のＮ型ドープが、大気中で長時間安定、例えば約２か月間安定する。 The base, the base derivative, and the acid derivative prevent oxygen or moisture in the air from invading the surface of the carbon-based thin film, and suppress the N-type state of the carbon-based thin film from being impaired. In addition, when there is an unreacted region, the unreacted region also prevents oxygen or moisture in the air from entering the photoreactive region and the surface of the carbon-based thin film, and the N-type state of the carbon-based thin film is impaired. Suppress. Therefore, in a complex having a photobase generator on top of a base, a base derivative, and an acid derivative, the N-type dope of the carbon-based thin film is stable in the atmosphere for a long time, for example, about 2 months.
（グラフェンの製造）
銅箔を加熱しながら、プラズマ中の荷電粒子または電子のエネルギーで銅箔中の炭素成分を活性化し、銅箔に含まれる炭素成分、反応容器内に付着した微量の炭素成分、および処理ガスに含まれる微量の炭素成分を用いて、単層グラフェンおよび２層グラフェン（以下、単層グラフェンと２層グラフェンをまとめて、グラフェンと記載することがある）を銅箔上にそれぞれ製造した（特開２０１５−１３７９７号公報参照）。
(Manufacturing of graphene)
While heating the copper foil, the carbon components in the copper foil are activated by the energy of charged particles or electrons in the plasma, and the carbon components contained in the copper foil, the trace amount of carbon components adhering to the reaction vessel, and the processing gas are converted. Single-layer graphene and double-layer graphene (hereinafter, single-layer graphene and double-layer graphene may be collectively referred to as graphene) were produced on copper foil using a trace amount of carbon component contained (Japanese Patent Laid-Open No. 2015-13797 (see).
（グラフェンのＰＥＴ基材への転写と積層体の加工）
熱剥離シート（日東電工社製、リバアルファー）上に、銅箔上のグラフェンを貼った。０．５ｍｏｌ／Ｌ過硫酸アンモニウムで銅箔をエッチングした後、流水で洗浄した。この熱剥離シートとグラフェンの積層体のグラフェン部分を、Ａ４判のＰＥＴ基材に貼り付けた。熱加熱することで剥離シートを剥離して、透明のＰＥＴ基材上にグラフェンが形成された積層体を得た。Ａ４判の積層体を切断して、一辺が１０ｍｍの正方形、または幅１０ｍｍ×長さ２０〜２０ｍｍの長方形の積層体を得た。
(Transfer of graphene to PET substrate and processing of laminate)
Graphene on copper foil was pasted on a heat release sheet (Nitto Denko, Liver Alpha). The copper foil was etched with 0.5 mol / L ammonium persulfate and then washed with running water. The graphene portion of the heat-release sheet and the graphene laminate was attached to an A4 size PET substrate. The release sheet was peeled off by heating to obtain a laminate in which graphene was formed on a transparent PET substrate. An A4 size laminate was cut to obtain a square laminate having a side of 10 mm or a rectangular laminate having a width of 10 mm and a length of 20 to 20 mm.
（グラフェンの石英基材への転写）
銅箔上のグラフェンの表面に、ポリメタクリル酸メチル樹脂（ＰＭＭＡ）の２質量％アニソール溶液を、３０００ｒｐｍで３０秒間スピンコートした。自然乾燥させた後、０．５ｍｏｌ／Ｌ過硫酸アンモニウムで銅箔をエッチングした後、流水で洗浄した。このＰＭＭＡ層とグラフェンの積層体のグラフェン部分を、一辺が１０ｍｍの正方形の石英基材に貼り付けた。アセトンで浸潤してＰＭＭＡを除去し、透明の石英基材上にグラフェンが形成された積層体を得た。
(Transfer of graphene to quartz substrate)
A 2% by mass anisole solution of polymethyl methacrylate resin (PMMA) was spin-coated on the surface of graphene on a copper foil at 3000 rpm for 30 seconds. After air-drying, the copper foil was etched with 0.5 mol / L ammonium persulfate and then washed with running water. The graphene portion of the PMMA layer and the graphene laminate was attached to a square quartz substrate having a side of 10 mm. PMMA was removed by infiltration with acetone to obtain a laminate in which graphene was formed on a transparent quartz substrate.
（グラフェンの層数の測定）
グラフェンの層数測定は、ヘイズメータ（日本電色工業株式会社、ＮＤＨ５０００ＳＰ）を用いた光透過率測定によって行った。光源は白色ＬＥＤであり、観測エリアは１０ｍｍ×１０ｍｍ程度である。グラフェンは１層あたり光透過率が２．３％低下することを用いて、層数ｎは以下の式で算出できる。
ｎ＝ＬＯＧ（サンプル透過率／基板の透過率）／ＬＯＧ（０．９７７）
この算出結果から、測定の誤差等を鑑みて、０．８≦ｎ≦１．２を単層、１．８≦ｎ≦２．２を２層とした。
(Measurement of graphene layers)
The number of layers of graphene was measured by measuring the light transmittance using a haze meter (Nippon Denshoku Industries Co., Ltd., NDH5000SP). The light source is a white LED, and the observation area is about 10 mm × 10 mm. Using graphene, which reduces the light transmittance per layer by 2.3%, the number of layers n can be calculated by the following formula.
n = LOG (sample transmittance / substrate transmittance) / LOG (0.977)
From this calculation result, in consideration of measurement error and the like, 0.8 ≦ n ≦ 1.2 was set as a single layer, and 1.8 ≦ n ≦ 2.2 was set as two layers.
（光塩基発生剤の塗布）
図１に示すように、光塩基発生剤（ＰＢＧ）の２−（９−オキソキサンテン−２−イル）プロピオン酸１，５，７−トリアザビシクロ［４．４．０］デカ−５−エン（東京化成工業製、Ｏ０３９６）は、陰イオン化した分子Ａ（２−（９−オキソキサンテン−２−イル）プロピオン酸：２−（９−ｏｘｏｘａｎｔｈｅｎ−２−ｙｌ）ｐｒｏｐｉｏｎｉｃ ａｃｉｄ）と陽イオン化した分子Ｂ（１，５，７−トリアザビシクロ［４．４．０］デカ−５−エン：１，５，７−ｔｒｉａｚａｂｉｃｙｃｌｏ［４．４．０］ｄｅｃ−５−ｅｎｅ）から構成される塩である。
(Application of photobase generator)
As shown in FIG. 1, the photobase generator (PBG) 2- (9-oxoxanthen-2-yl)
この光塩基発生剤の１０〜２０ｍｇ／ｍＬメタノール溶液をＰＤＭＳ（ｐｏｌｙｄｉｍｅｔｈｙｌｓｉｌｏｘａｎｅ）シート（東レ ＳＩＬＰＯＴ １８４）またはポリイミドフィルム（東レ・デュポン Ｋａｐｔｏｎ ２０ＥＮ、厚さ７μｍ）上に滴下した。積層体のグラフェンの両端以外の部分または四隅以外の部分に、このＰＤＭＳシートまたはポリイミドフィルムを押し当てて、積層体のグラフェンの表面に光塩基発生剤を転写した。ホットプレート上に、表面に光塩基発生剤が設けられたこの積層体を載せ、大気中８０℃で２０分間乾燥して、溶媒のメタノールを除去した。 A 10 to 20 mg / mL methanol solution of this photobase generator was added dropwise onto a PDMS (polydimethylsiloxane) sheet (Toray SILPOT 184) or a polyimide film (Toray DuPont Kapton 20EN, 7 μm thick). The PDMS sheet or polyimide film was pressed against a portion other than both ends or four corners of the graphene of the laminated body to transfer the photobase generator to the surface of the graphene of the laminated body. This laminate having a photobase generator on its surface was placed on a hot plate and dried in the air at 80 ° C. for 20 minutes to remove methanol as a solvent.
（紫外光照射）
光源（分光計器製、高強度分光光源：ＳＭ２５型ハイパーモノライト）を用いて、石英基材およびＰＥＴ基材側から、波長３４０ｎｍ、最大強度１．３ｍＷｃｍ−２の紫外光（ＵＶ）を最大４６０秒間照射して、石英基材またはＰＥＴ基材と、グラフェンと、光塩基発生剤に由来する物質を備える複合体を得た。
(Ultraviolet light irradiation)
Using a light source (manufactured by a spectroscope, high-intensity spectroscopic light source: SM25 type hypermonolite), ultraviolet light (UV) with a wavelength of 340 nm and a maximum intensity of 1.3 mWcm-2 can be emitted from the quartz substrate side and the PET substrate side at a maximum of 460. Irradiation for seconds gave a composite comprising a quartz or PET substrate, graphene, and a substance derived from a photobase generator.
（コンダクタンスと熱起電力の測定）
複合体のグラフェンの光塩基発生剤が設けられていない両端部分は、コンダクタンス測定用の電極および温度計測用の熱電対を接触させる部分である。複合体のグラフェンのコンダクタンスと熱起電力を測定しながら紫外光照射を行ない、照射量の増加によるグラフェンのキャリアのＰ型からＮ型への経時変化を測定した。グラフェンの両端部分に、コンダクタンス測定装置（ケースレーインスツルメンツ製、２４００型ソースメータ）のプローブ電極を接触させ、２端子間において、１ｍＡの一定のバイアス電流を印加しながら、グラフェンのコンダクタンスを測定した。
(Measurement of conductance and thermoelectromotive force)
The ends of the complex graphene where the photobase generator is not provided are the portions where the electrodes for conductance measurement and the thermocouple for temperature measurement are brought into contact with each other. Irradiation with ultraviolet light was performed while measuring the conductance and thermoelectromotive force of the graphene of the complex, and the change over time of the graphene carrier from P-type to N-type due to the increase in the irradiation amount was measured. The probe electrodes of a conductance measuring device (2400 type source meter manufactured by Caseray Instruments) were brought into contact with both ends of the graphene, and the conductance of the graphene was measured while applying a constant bias current of 1 mA between the two terminals.
電気的に絶縁し、離れて設けられた２種の金属板の上に、複合体のグラフェンを載せた。グラフェンの両端部分に温度計測用の薄型Ｋ熱電対をそれぞれ接触させて固定した。この２種の金属板を熱浴として加熱し、互いに異なる温度に制御することで温度差を生じさせて、その際の両端の２つのＫ熱電対による温度差と、２つのＫ熱電対のアルメル線間の熱起電力を、計測装置（日置電機製、ＬＲ８４００型メモリハイロガー）で記録した。 Graphene of the complex was placed on two types of metal plates that were electrically insulated and provided separately. Thin K thermocouples for temperature measurement were brought into contact with each other and fixed to both ends of the graphene. These two types of metal plates are heated as a hot bath and controlled to different temperatures to create a temperature difference. At that time, the temperature difference between the two K thermocouples at both ends and the Almer of the two K thermocouples. The thermoelectromotive force between the lines was recorded by a measuring device (manufactured by Hioki Electric, LR8400 type memory high logger).
（シート抵抗とＨａｌｌ係数の測定）
積層体または複合体のグラフェンの光塩基発生剤が設けられていない四隅に金電極を接触させ、Ｈａｌｌ計測システム（東陽テクニカ製、Ｒｅｓｉｔｅｓｔ８３００型）を用いて、ｖａｎ ｄｅｒ Ｐａｕｗ法でこれら４端子間に対するシート抵抗とＨａｌｌ係数を測定した。すなわち、基材とグラフェンから構成される積層体、基材とグラフェンと光塩基発生剤から構成される複合体、および基材とグラフェンと光塩基発生剤から構成され、光塩基発生剤に紫外光を照射した後の複合体の３種類の試料のグラフェンのシート抵抗とＨａｌｌ係数を測定した。試料への印加電流は０．２〜０．５ｍＡとし、印加磁場は正磁場・負磁場共に０．５５Ｔとした。
(Measurement of sheet resistance and Hall coefficient)
A gold electrode is brought into contact with the four corners of the graphene of the laminate or composite in which the photobase generator is not provided, and a Hall measurement system (manufactured by Toyo Technica, Restist 8300 type) is used to connect between these four terminals by the van der Pauw method. Sheet resistance and Hall coefficient were measured. That is, it is composed of a laminate composed of a base material and graphene, a complex composed of a base material, graphene and a photobase generator, and a base material, graphene and a photobase generator, and the photobase generator is ultraviolet light. The sheet resistance and Hall coefficient of graphene of the three types of samples of the complex after irradiation were measured. The applied current to the sample was 0.2 to 0.5 mA, and the applied magnetic field was 0.55 T for both the positive magnetic field and the negative magnetic field.
（キャリア濃度と移動度の算出）
グラフェンのキャリア濃度ｎと移動度μは、シート抵抗ＲＳ、Ｈａｌｌ係数ＲＨ、電荷素量ｅ（＝１．６０２×１０−１９Ｃ）用いて、ｎ＝ｔ／（ｅＲＨ）とμ＝ＲＨ／（ｔＲｓ）の式により算出した。ここでｔはグラフェンの厚さであり、単層、２層、１．７層のグラフェンの厚さをそれぞれ０．３ｎｍ、０．６ｎｍ、０．５１ｎｍとした。ＲＨの符号の正負により、グラフェンのキャリアが正孔（Ｐ型）であるか、電子（Ｎ型）であるかを判定した。
(Calculation of carrier concentration and mobility)
The mobility mu and the carrier concentration n of the graphene sheet resistance R S, Hall coefficient R H, elementary electric charge e (= 1.602 × 10 -19 C ) using, n = t / (eR H ) and mu = It was calculated by the formula of RH / (tRs). Here, t is the thickness of graphene, and the thickness of the graphene of the single layer, the two layers, and the 1.7 layer is set to 0.3 nm, 0.6 nm, and 0.51 nm, respectively. It was determined whether the carrier of graphene was a hole (P type) or an electron (N type) based on the sign of RH.
（ラマンスペクトルの測定）
光塩基発生剤の塗布と紫外光照射によるグラフェンの欠陥形成および構造変化を調べるため、レーザラマン分光光度計（日本分光製、ＮＲＳ−２１００型）を用いて、積層体または複合体のグラフェンのラマンスペクトルを測定した。本実験では、グラフェンのラマンスペクトルを明瞭に測定するために、上面が一辺１０ｍｍの正方形で厚さ１．０ｍｍの合成石英基板を基材とした。また、光塩基発生剤自体のラマンスペクトルと、グラフェンのラマンスペクトルの重複が大きいため、合成石英基板上のグラフェンのラマンスペクトルを測定した後、このグラフェンに光塩基発生剤の塗布と紫外光照射を行い、光塩基発生剤をメタノールで洗浄除去してから、グラフェンのラマンスペクトルを再度測定した。
(Measurement of Raman spectrum)
A laser Raman spectrophotometer (NRS-2100, manufactured by JASCO Corporation) was used to investigate the formation of defects and structural changes in graphene due to the application of a photobase generator and irradiation with ultraviolet light. Was measured. In this experiment, in order to clearly measure the Raman spectrum of graphene, a synthetic quartz substrate having a square surface with a side of 10 mm and a thickness of 1.0 mm was used as a base material. In addition, since the Raman spectrum of the photobase generator itself and the Raman spectrum of graphene overlap greatly, after measuring the Raman spectrum of graphene on a synthetic quartz substrate, the graphene is coated with a photobase generator and irradiated with ultraviolet light. After washing and removing the photobase generator with methanol, the graphene Raman spectrum was measured again.
（結果）
図２（ａ）は、ＰＥＴ基材と２層グラフェンの積層体の２層グラフェン上に光塩基発生剤を塗布した後、ＰＥＴ基材に紫外光を照射したときの２層グラフェンのコンダクタンスの経時変化を示している。時刻５０秒で紫外光照射を開始すると、２層グラフェンのコンダクタンスは減少し、時刻７０秒（紫外光照射開始後２０秒）程度で最低値に達した後、再び増加に転じて、時刻３００秒（紫外光照射開始後２５０秒）で飽和に近づいた。この変化は、紫外光によって光塩基発生剤から生じた塩基によるものであると考えられる。
(result)
FIG. 2A shows the time-lapse of the conductance of the two-layer graphene when the PET base material is irradiated with ultraviolet light after the photobase generator is applied on the two-layer graphene of the laminate of the PET base material and the two-layer graphene. It shows a change. When the ultraviolet light irradiation was started at 50 seconds, the conductance of the two-layer graphene decreased, reached the minimum value at about 70 seconds (20 seconds after the start of ultraviolet light irradiation), and then started to increase again, and the time was 300 seconds. It approached saturation (250 seconds after the start of ultraviolet light irradiation). This change is considered to be due to the base generated from the photobase generator by ultraviolet light.
図１に示すように、２−（９−オキソキサンテン−２−イル）プロピオン酸１，５，７−トリアザビシクロ［４．４．０］デカ−５−エンは、紫外光照射によって、分子Ｂがプロトンを１個放出して分子Ｂ′の塩基となる。そして、この塩基１分子当たり電子１個をグラフェンに供与することで、グラフェンのドーピング状態を変化、つまりＦｅｒｍｉレベルを移動させ、グラフェン特有の電子構造として知られるディラックポイントを横切ることで、グラフェンがＰ型導電体からＮ型導電体に変化すると推測される。
As shown in FIG. 1, 2- (9-oxoxanthen-2-yl)
そこで、図２（ａ）に示す紫外光照射の前後で、２層グラフェンの熱起電力を測定した結果を図２（ｂ）に示す。紫外光照射前後に関わらず、２層グラフェンの熱起電力は、温度変化に対して比例しており、Ｓｅｅｂｅｃｋ係数が求められた。その結果、紫外光照射前の２層グラフェンのＳｅｅｂｅｃｋ係数は＋３０μＶ／Ｋで、紫外光照射前の２層グラフェンはＰ型導電体であった。これに対して、紫外光照射後の２層グラフェンのＳｅｅｂｅｃｋ係数は−５０μＶ／Ｋで、紫外光照射後の２層グラフェンはＮ型導電体となった。したがって、上記の推測どおり、Ｐ型導電体であったグラフェンが、光塩基発生剤の反応によってディラックポイントを横切り、紫外光照射後の２層グラフェンがＮ型導電体に変化することが確認できた。 Therefore, the results of measuring the thermoelectromotive force of the two-layer graphene before and after the ultraviolet light irradiation shown in FIG. 2 (a) are shown in FIG. 2 (b). The thermoelectromotive force of the two-layer graphene was proportional to the temperature change regardless of before and after the irradiation with ultraviolet light, and the Seebeck coefficient was obtained. As a result, the Seebeck coefficient of the two-layer graphene before the irradiation with ultraviolet light was + 30 μV / K, and the two-layer graphene before the irradiation with ultraviolet light was a P-type conductor. On the other hand, the Seebeck coefficient of the two-layer graphene after the irradiation with ultraviolet light was -50 μV / K, and the two-layer graphene after the irradiation with ultraviolet light became an N-type conductor. Therefore, as estimated above, it was confirmed that graphene, which was a P-type conductor, crossed the dilac point due to the reaction of the photobase generator, and the two-layer graphene after ultraviolet light irradiation changed to an N-type conductor. ..
図３（ａ）は、ＰＥＴ基材と単層グラフェンの積層体の単層グラフェン上に光塩基発生剤を塗布した後、ＰＥＴ基材に紫外光を照射したときの単層グラフェンのコンダクタンスの経時変化を示している。図２（ａ）に示す２層グラフェンのコンダクタンスの変化が、単層グラフェンでも同様にみられた。図３（ｂ）は、ＰＥＴ基材と２層グラフェンの積層体の２層グラフェン上に光塩基発生剤を塗布した後、ＰＥＴ基材に紫外光を照射したときの２層グラフェンのコンダクタンスの経時変化を示している。なお、図２（ａ）に示す試料と異なる試料で、２層グラフェンのコンダクタンスを測定した。図２（ａ）および図３（ｂ）に示すように、２層グラフェンのコンダクタンス変化は再現性があった。 FIG. 3A shows the time-lapse of the conductance of the single-layer graphene when the PET base material is irradiated with ultraviolet light after the photobase generator is applied on the single-layer graphene of the laminate of the PET base material and the single-layer graphene. It shows a change. The change in conductance of the two-layer graphene shown in FIG. 2 (a) was also observed in the single-layer graphene. FIG. 3 (b) shows the time lapse of the conductance of the two-layer graphene when the PET base material is irradiated with ultraviolet light after the photobase generator is applied on the two-layer graphene of the laminate of the PET base material and the two-layer graphene. It shows a change. The conductance of the two-layer graphene was measured with a sample different from the sample shown in FIG. 2 (a). As shown in FIGS. 2 (a) and 3 (b), the conductance change of the two-layer graphene was reproducible.
図３（ａ）および図３（ｂ）に示す実験では、紫外光の照射密度を１．３ｍＷ／ｃｍ２としたが、単層グラフェンおよび２層グラフェンのいずれについても、紫外光照射開始後約３００秒程度で、紫外光照射後のコンダクタンス再増加が飽和していた。紫外光照射量に応じて、単層グラフェンおよび２層グラフェンのＮ型ドーピング状態が飽和していると考えられる。 In the experiments shown in FIGS. 3 (a) and 3 (b), the irradiation density of ultraviolet light was set to 1.3 mW / cm 2 , but for both single-layer graphene and double-layer graphene, about after the start of ultraviolet light irradiation. In about 300 seconds, the re-increase in conductance after ultraviolet light irradiation was saturated. It is considered that the N-type doping state of single-layer graphene and double-layer graphene is saturated according to the amount of ultraviolet light irradiation.
図４は、ＰＥＴ基材と２層グラフェンの積層体の２層グラフェン上に光塩基発生剤を塗布した後、ＰＥＴ基材に紫外光を照射したときの２層グラフェンの熱起電力の経時変化を示している。この実験では２層グラフェンに６Ｋの一定の温度差を付与して、熱起電力を計測した。その結果、紫外光照射を開始すると速やかに熱起電力の符号が正から負に反転し、２層グラフェンがＰ型導電体からＮ型導電体へ変化した。Ｈａｌｌ係数についても同様に、単層グラフェンと２層グラフェンの両方で、紫外光照射による符号の反転（Ｐ型からＮ型へ変化）を確認した。 FIG. 4 shows the time course of the thermoelectromotive force of the two-layer graphene when the PET base material is irradiated with ultraviolet light after the photobase generator is applied on the two-layer graphene of the laminate of the PET base material and the two-layer graphene. Is shown. In this experiment, the thermoelectromotive force was measured by applying a constant temperature difference of 6K to the two-layer graphene. As a result, when the ultraviolet light irradiation was started, the sign of the thermoelectromotive force was immediately reversed from positive to negative, and the two-layer graphene changed from a P-type conductor to an N-type conductor. Similarly, regarding the Hall coefficient, the sign inversion (change from P-type to N-type) due to ultraviolet light irradiation was confirmed for both single-layer graphene and double-layer graphene.
図５は、ＰＥＴ基材上の２層グラフェンのシート抵抗およびＨａｌｌ係数の測定結果と、それらによって算出されるキャリア濃度および移動度の値を、２層グラフェンへの光塩基発生剤塗布前（処理前）、２層グラフェンへのＰＢＧ塗布後紫外光未照射の状態、ＰＥＴ基材側からＰＢＧに紫外光を照射した後の３つの過程でそれぞれ示した。この実験では、紫外光の照射密度を１．３ｍＷ／ｃｍ２、照射時間を３００秒とした。 FIG. 5 shows the measurement results of the sheet resistance and Hall coefficient of the two-layer graphene on the PET substrate, and the values of the carrier concentration and mobility calculated by them before applying the photobase generator to the two-layer graphene (treatment). (Before), the state of not irradiating ultraviolet light after applying PBG to the two-layer graphene, and the three processes after irradiating PBG with ultraviolet light from the PET substrate side are shown. In this experiment, the irradiation density of ultraviolet light was 1.3 mW / cm 2 , and the irradiation time was 300 seconds.
処理前の２層グラフェンは、従来よく知られているように、Ｐ型（Ｈａｌｌ係数の符号が正）であり、キャリア（正孔）濃度が約２．０×１０１３ｃｍ−２、移動度が約１２００ｃｍ２／Ｖｓであった。これに対して、２層グラフェンにＰＢＧを塗布した直後では、２層グラフェンはＮ型（Ｈａｌｌ係数の符号が負）に転じたが、そのまま暗中でＨａｌｌ係数測定を続けると、ＰＢＧ塗布５０分後には再びＰ型に戻った。 As is well known in the past, the untreated two-layer graphene is P-type (the sign of the Hall coefficient is positive), the carrier (hole) concentration is about 2.0 × 10 13 cm- 2 , and the mobility is high. Was about 1200 cm 2 / Vs. On the other hand, immediately after applying PBG to the two-layer graphene, the two-layer graphene turned to N-type (the sign of the Hall coefficient is negative), but if the Hall coefficient measurement was continued in the dark as it was, 50 minutes after the application of PBG. Returned to P type again.
ＰＢＧ塗布直後の２層グラフェンのキャリア濃度の絶対値は、ＰＢＧ塗布前の２層グラフェンのキャリア濃度の絶対値と比べて約１／１０に低下し、移動度は１．５〜２．０倍に増加した。ＰＢＧ塗布のみでも、２層グラフェンはＮ型に変化した。これは、自然の屋内光が存在する実験室でＰＢＧ塗布工程を行っているために、一部のＰＢＧが反応して、塗布直後に２層グラフェンがＮ型となったものの、紫外光照射量が少なくＮ型ドーピング状態が不安定で、２層グラフェンがすぐにＰ型に復帰したと考えられる。 The absolute value of the carrier concentration of the two-layer graphene immediately after the application of PBG is reduced to about 1/10 of the absolute value of the carrier concentration of the two-layer graphene before the application of PBG, and the mobility is 1.5 to 2.0 times. Increased to. Even with PBG application alone, the two-layer graphene changed to N-type. This is because the PBG coating process is performed in a laboratory where natural indoor light exists, so some PBGs reacted and the two-layer graphene became N-type immediately after coating, but the amount of ultraviolet light irradiation It is considered that the two-layer graphene immediately returned to P-type because the N-type doping state was unstable.
また、大気中のグラフェンは、表面に吸着した酸素分子や水分子の影響を受けて、正孔が大量にドーピングされた状態である。このグラフェンに光塩基発生剤を塗布することによって、グラフェンの表面に吸着していたこれらの分子がある程度除去され、ＰＢＧ塗布後のキャリア濃度の絶対値が１／１０程度に低下したと考えられる。つづいて、ＵＶ照射後の２層グラフェンのＨａｌｌ係数の符号は再度負に転じ、２層グラフェンがＮ型である状態は、ＵＶ照射後１５０分経過後、さらには２か月経過後も維持された。 In addition, graphene in the atmosphere is in a state in which a large amount of holes are doped due to the influence of oxygen molecules and water molecules adsorbed on the surface. It is considered that by applying the photobase generator to the graphene, these molecules adsorbed on the surface of the graphene were removed to some extent, and the absolute value of the carrier concentration after the application of PBG was reduced to about 1/10. Subsequently, the sign of the Hall coefficient of the two-layer graphene after UV irradiation turned negative again, and the state in which the two-layer graphene was N-type was maintained 150 minutes after UV irradiation and further two months later. It was.
キャリア（電子）濃度は、ＵＶ照射直後に２．１×１０１２ｃｍ−２で、１５０分後にいったん増加したものの、２か月後もＵＶ照射直後とほぼ同じ電子濃度を保っていた。また、ＵＶ照射後の２層グラフェンの電子の移動度は、２３２０〜３５６０ｃｍ２／Ｖｓとなり、ＰＢＧ塗布前の正孔の移動度の２倍以上の値を２か月維持した。 The carrier (electron) concentration was 2.1 × 10 12 cm- 2 immediately after UV irradiation, and although it increased once 150 minutes later, it maintained almost the same electron concentration as immediately after UV irradiation two months later. The electron mobility of the two-layer graphene after UV irradiation was 2320 to 3560 cm 2 / Vs, which was more than twice the mobility of holes before PBG application for 2 months.
単層グラフェンについて、図５に示す実験と同じ実験を行った結果を図６に示す。処理前の単層グラフェンは、２層グラフェンと同様に、Ｐ型（Ｈａｌｌ係数の符号が正）であり、キャリア（正孔）濃度が約１．６×１０１３ｃｍ−２、移動度約１０００ｃｍ２／Ｖｓであった。これに対し、ＰＢＧ塗布後はＮ型導電体（Ｈａｌｌ係数の符号が負）に転じた。これは、自然の屋内光が存在する実験室でＰＢＧ塗布工程を行っているために、一部のＰＢＧが反応して、塗布直後に単層グラフェンがＮ型導電体となったものの、紫外光照射量が少なくＮ型ドーピング状態が低く不安定であった。 FIG. 6 shows the results of performing the same experiment as that shown in FIG. 5 for single-layer graphene. Like the two-layer graphene, the single-layer graphene before treatment is P-type (the sign of the Hall coefficient is positive), the carrier (hole) concentration is about 1.6 × 10 13 cm- 2 , and the mobility is about 1000 cm. It was 2 / Vs. On the other hand, after applying PBG, the conductor turned into an N-type conductor (the sign of the Hall coefficient is negative). This is because the PBG coating process is performed in a laboratory where natural indoor light exists, so some PBGs reacted and the single-layer graphene became an N-type conductor immediately after coating, but ultraviolet light. The irradiation amount was small, the N-type doping state was low, and it was unstable.
加えて、ＵＶ照射後１５０分経過後、さらには２か月経過後も、単層グラフェンがＮ型の状態が維持され、キャリア（電子）濃度は、２．０×１０１２ｃｍ−２前後（１．３〜２．９×１０１２ｃｍ−２）の値を示した。電子の移動度は、ＰＢＧ塗布後ＵＶ照射前で３６１０〜４２４０ｃｍ２／Ｖｓ、ＵＶ照射後で２１２０〜２７５０ｃｍ２／Ｖｓとなり、ＰＢＧ塗布前の正孔の移動度の２倍以上の値を２か月維持した。
In addition, the monolayer graphene remains in the N-
石英基板上の１．７層グラフェンのラマンスペクトルを図７に示す。処理前の１．７層グラフェンでは、１３３０ｃｍ−１付近のＤバンド、１５８０ｃｍ−１付近のＧバンド、２７００ｃｍ−１付近の２Ｄバンドの３つの特徴的なピークが、石英基板のスペクトルに影響を受けることなく測定できた。ＰＢＧ塗布およびＵＶ照射（照射密度１．３ｍＷ／ｃｍ２、照射時間３００秒）後に、光塩基発生剤を除去して測定した石英基板上の１．７層グラフェンのラマンスペクトルは、処理前の１．７層グラフェンのラマンスペクトルから大きな変化がなかった。特に、グラフェンに生じる欠陥形成に起因するＤバンドの相対強度は変化がなかった。これは、ＰＢＧ塗布およびＵＶ照射による１．７層グラフェンの欠陥形成が認められなかったことを示している。
The Raman spectrum of 1.7-layer graphene on a quartz substrate is shown in FIG. The 1.7-layer graphene pretreatment, D band near 1330 cm -1, G band near 1580
また、このことは、２層グラフェンおよび単層グラフェンが、光塩基発生剤塗布前に比べて約２倍以上高いキャリア移動度を２か月維持している図５および図６の結果を裏付けるものである。図２から図７に示す実験結果から、以下の４つが確認できた。
（１）光塩基発生剤塗布および紫外光照射によって、２層グラフェンおよび単層グラフェンがＰ型からＮ型に変化することを熱起電力（Ｓｅｅｂｅｃｋ係数）およびＨａｌｌ係数の符号変化で確認し、Ｎ型導電体の状態を２か月保持できた。
（２）２層グラフェンおよび単層グラフェンのＮ型への変化後の電子濃度は、照射密度１．３ｍＷ／ｃｍ２、照射時間３００秒の紫外光照射により、光塩基発生剤塗布前の正孔濃度に比べて約１／１０に低下した。
This also supports the results of FIGS. 5 and 6 in which the two-layer graphene and the single-layer graphene maintain the carrier mobility about twice or more higher than that before the application of the photobase generator for two months. Is. From the experimental results shown in FIGS. 2 to 7, the following four were confirmed.
(1) It was confirmed by the sign change of the thermoelectromotive force (Seebeck coefficient) and the Hall coefficient that the two-layer graphene and the single-layer graphene changed from P-type to N-type by applying a photobase generator and irradiating with ultraviolet light, and N The state of the mold conductor could be maintained for 2 months.
(2) The electron concentration of the two-layer graphene and the single-layer graphene after the change to the N-type is as follows: holes before application of the photobase generator by irradiation with ultraviolet light having an irradiation density of 1.3 mW / cm 2 and an irradiation time of 300 seconds. It decreased to about 1/10 of the concentration.
（３）グラフェンのＮ型への変化後のキャリア移動度は、照射密度１．３ｍＷ／ｃｍ２、照射時間３００秒の紫外光照射により、光塩基発生剤塗布前のキャリア移動度に比べて約２倍以上増加した。
（４）グラフェンの欠陥形成に起因するラマンスペクトルのＤバンド強度の変化は、光塩基発生剤塗布および紫外光照射後（ＰＢＧ塗布＆ＵＶ照射→ＰＢＧ除去後）でも観測されず、これらの処理によるグラフェンの欠陥形成が認められなかった。
(3) The carrier mobility after the change of graphene to N-type is about about the carrier mobility before application of the photobase generator by irradiation with ultraviolet light with an irradiation density of 1.3 mW / cm 2 and an irradiation time of 300 seconds. It increased more than twice.
(4) Changes in the D-band intensity of the Raman spectrum due to the formation of graphene defects were not observed even after the application of the photobase generator and the irradiation with ultraviolet light (after the application of PBG & UV irradiation → after the removal of PBG), and the graphene due to these treatments was not observed. No defect formation was observed.
ここで、光塩基発生剤がグラフェンのドーピング状態を紫外光照射によってＰ型からＮ型に変化させるメカニズムと、Ｎ型状態が２か月にわたり安定に保持されていた原因について考察する。グラフェン上に塗布された光塩基発生剤に紫外光が照射されると、図１に示すように、分子ＡからＣＯ２が分離し、さらに分子Ｂから分離したプロトンが結合した分子Ａ′に変化し、非イオン化して安定化する。一方、分子Ｂからプロトンを１個放出した分子Ｂ′は塩基となり、１分子当たり電子１個をグラフェンに供与して、正イオン化した塩基誘導体である分子Ｂ′′となり安定化する。 Here, the mechanism by which the photobase generator changes the doping state of graphene from P-type to N-type by ultraviolet light irradiation and the reason why the N-type state is stably maintained for 2 months will be considered. When the photobase generator coated on graphene is irradiated with ultraviolet light, as shown in FIG. 1, CO 2 is separated from the molecule A and further changed to the molecule A'with the protons separated from the molecule B bonded. And deionize and stabilize. On the other hand, the molecule B ′ that releases one proton from the molecule B becomes a base and donates one electron per molecule to graphene to become a molecule B ″ which is a positively ionized base derivative and stabilizes.
グラフェンの代わりに色素であるフェノールレッドを用いて、ＰＢＧ塗布とＵＶ照射を行った。ＰＥＴ基材上にフェノールレッド膜を形成し、フェノールレッド膜上の光塩基発生剤を塗布し、ＰＥＴ基材側からフェノールレッド膜に紫外光を最大１０分間照射した。紫外光照射時間が長いほど、フェノールレッド膜の赤色が強くなったことを、光塩基発生剤を塗布したフェノールレッド膜の光吸収スペクトルで確認した。フェノールレッドは電子が供与されると赤色を帯びる。つまり、光塩基発生剤を塗布したフェノールレッド膜は、紫外光照射によって分子Ｂ′から電子を供与された。これより、電子を受容できる膜上に光塩基発生剤を塗布し、紫外光照射すると、光塩基発生剤から生じた塩基がこの膜に電子を供与して、塩基誘導体となって膜上に存在すると考えられる。 PBG coating and UV irradiation were performed using phenol red, which is a dye, instead of graphene. A phenol red film was formed on the PET substrate, a photobase generator on the phenol red film was applied, and the phenol red film was irradiated with ultraviolet light for a maximum of 10 minutes from the PET substrate side. It was confirmed by the light absorption spectrum of the phenol red film coated with the photobase generator that the red color of the phenol red film became stronger as the ultraviolet light irradiation time became longer. Phenol red becomes reddish when electrons are donated. That is, the phenol red film coated with the photobase generator was donated with electrons from the molecule B'by irradiation with ultraviolet light. From this, when a photobase generator is applied on a membrane that can accept electrons and irradiated with ultraviolet light, the base generated from the photobase generator donates electrons to this membrane and becomes a base derivative and exists on the membrane. It is thought that.
図８に、表面に光塩基発生剤を塗布し、裏面から紫外光を照射したグラフェンの構造モデルを示す。裏面から炭素系薄膜を通過して光塩基発生剤層に紫外光が届いた際に、図１に示した反応によって分子Ｂ′と分子Ａ′に変化する。ただし、光塩基発生剤層の厚みによっては、グラフェンの表面近傍で光反応が完了した領域（光反応領域）だけでなく、その上に堆積する未反応の領域（未反応領域）が存在する場合もある。光反応領域では、分子Ｂ′が供与した電子によって、Ｐ型導電体であるグラフェンは、正孔が消去された後、電子ドープ状態（Ｎ型導電体）になる。 FIG. 8 shows a structural model of graphene in which a photobase generator is applied to the front surface and ultraviolet light is irradiated from the back surface. When ultraviolet light reaches the photobase generator layer from the back surface through the carbon-based thin film, it changes into molecules B'and A'by the reaction shown in FIG. However, depending on the thickness of the photobase generator layer, not only the region where the photoreaction is completed (photoreaction region) near the surface of graphene but also the unreacted region (unreacted region) deposited on it may exist. There is also. In the photoreaction region, graphene, which is a P-type conductor, is put into an electron-doped state (N-type conductor) after holes are eliminated by electrons donated by the molecule B'.
なお、図８には示していないが、電子を供与した分子Ｂ′は、塩基誘導体である分子Ｂ′′に変化する。分子Ａ′は不活性でありドーピングには寄与しない。分子Ｂ′、分子Ｂ′′、および分子Ａ′は、空気中の酸素または水分等がグラフェン表面に侵入してグラフェンのＮ型状態を損なうのを防ぎ、大気中でのＮ型導電体の安定性を与えていると考えられる。加えて、未反応領域も、空気中の酸素または水分等が光反応領域またはグラフェン表面に侵入してＮ型状態を損なうのを防ぎ、大気中でのＮ型導電体の安定性を与えていると考えられる。 Although not shown in FIG. 8, the molecule B ′ donating an electron changes to the molecule B ″ which is a base derivative. The molecule A'is inert and does not contribute to doping. Molecule B ′, molecule B ″, and molecule A ′ prevent oxygen or moisture in the air from invading the surface of graphene and impairing the N-type state of graphene, and stabilize the N-type conductor in the atmosphere. It is thought to give sex. In addition, the unreacted region also prevents oxygen or moisture in the air from invading the photoreactive region or the graphene surface and impairing the N-type state, and provides stability of the N-type conductor in the atmosphere. it is conceivable that.
Claims (9)
前記炭素系薄膜上に設けられ、光塩基発生剤に由来する塩基の誘導体で、正電荷を帯びた塩基誘導体と、
前記炭素系薄膜上に設けられ、前記光塩基発生剤から前記塩基が脱離した物質に由来する酸誘導体と、
を有する複合体。 N-type doped carbon thin film and
A base derivative provided on the carbon-based thin film and derived from a photobase generator, which is a positively charged base derivative and
An acid derivative provided on the carbon-based thin film and derived from a substance from which the base has been eliminated from the photobase generator, and
Complex with.
前記塩基誘導体および前記酸誘導体の上に、前記光塩基発生剤をさらに有する複合体。 In claim 1,
A complex further comprising the photobase generator on the base derivative and the acid derivative.
紫外光を透過する基材をさらに有し、前記炭素系薄膜が前記基材上に設けられている複合体。 In claim 1 or 2,
A complex having a base material that transmits ultraviolet light and having the carbon-based thin film provided on the base material.
前記炭素系薄膜が、層数の平均値が０．８以上１．２以下である単層グラフェン、層数の平均値が１．８以上２．２以下である２層グラフェン、および層数の平均値が０．８以上２．２以下である２層グラフェン中に部分的に単層グラフェンの領域が混在するグラフェンのいずれかである複合体。 In any of claims 1 to 3,
The carbon-based thin film has a single-layer graphene having an average number of layers of 0.8 or more and 1.2 or less, a two-layer graphene having an average number of layers of 1.8 or more and 2.2 or less, and a number of layers. A complex that is one of graphenes in which regions of monolayer graphene are partially mixed in two-layer graphene having an average value of 0.8 or more and 2.2 or less.
前記光塩基発生剤が２−（９−オキソキサンテン−２−イル）プロピオン酸１，５，７−トリアザビシクロ［４．４．０］デカ−５−エンである複合体。 In any of claims 1 to 4,
A complex in which the photobase generator is 2- (9-oxoxanthene-2-yl) propionic acid 1,5,7-triazabicyclo [4.4.0] deca-5-ene.
光塩基発生剤層形成工程後、前記積層体の前記基材側から紫外光を照射する紫外光照射工程と、
を有する複合体の製造方法。 A photobase generator layer forming step of forming a photobase generator layer on the carbon-based thin film of a laminate having a base material that transmits ultraviolet light and a carbon-based thin film provided on the base material.
After the photobase generator layer forming step, an ultraviolet light irradiation step of irradiating ultraviolet light from the base material side of the laminate, and an ultraviolet light irradiation step.
A method for producing a complex having.
前記光塩基発生剤層形成工程では、弾性体の表面に形成した光塩基発生剤層を、前記炭素系薄膜上に転写する過程を備える複合体の製造方法。 In claim 6,
The method for producing a composite, which comprises a process of transferring a photobase generator layer formed on the surface of an elastic body onto the carbon-based thin film in the photobase generator layer forming step.
前記炭素系薄膜が、層数の平均値が０．８以上１．２以下である単層グラフェン、層数の平均値が１．８以上２．２以下である２層グラフェン、および層数の平均値が０．８以上２．２以下である２層グラフェン中に部分的に単層グラフェンの領域が混在するグラフェンのいずれかである複合体の製造方法。 In claim 6 or 7,
The carbon-based thin film has a single-layer graphene having an average number of layers of 0.8 or more and 1.2 or less, a two-layer graphene having an average number of layers of 1.8 or more and 2.2 or less, and a number of layers. A method for producing a complex which is one of graphenes in which a region of monolayer graphene is partially mixed in bilayer graphene having an average value of 0.8 or more and 2.2 or less.
前記光塩基発生剤が２−（９−オキソキサンテン−２−イル）プロピオン酸１，５，７−トリアザビシクロ［４．４．０］デカ−５−エンである複合体の製造方法。 In any of claims 6 to 8,
A method for producing a complex in which the photobase generator is 2- (9-oxoxanthene-2-yl) propionic acid 1,5,7-triazabicyclo [4.4.0] deca-5-ene.
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