JP5056398B2 - Method of using sensor and sensor device - Google Patents
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Description
本発明は、有機材料をチャネル形成層として有する有機電界効果トランジスタを用いた、極性分子を検出するセンサの使用方法及びセンサ装置に関する。 The present invention relates to a method of using a sensor for detecting polar molecules and a sensor device using an organic field effect transistor having an organic material as a channel formation layer.
近年、有機ＥＬ素子が画像表示装置として実用化され、有機半導体が脚光を浴びている。この中で、有機材料をチャネル形成層として有する有機電界効果トランジスタを、悪臭を有するガス或いは有毒なガスの検出器（センサ）として用いうることが報告されている。
特許文献１の発明者は非特許文献１の著者と大部分共通している。特許文献１と非特許文献１では、いずれもオリゴアルキルチオフェンをチャネル形成層とした有機電界効果トランジスタを用いた、極性基を有する有機低分子化合物蒸気のセンサが開示されている。有機低分子化合物の極性基とは、アルコール性又はフェノール性水酸基、カルボキシル基、カルボニル基、アミノ基その他の、有機低分子化合物に極性（双極子モーメント）を付与する原子団を言うものとする。尚、良く知られているように、トルエンもメチル基とフェニル基の間で双極子モーメントが生じており、極性基を有する有機低分子化合物に含まれるものとする。
特許文献１及び非特許文献１にある通り、ドレインに負電位、ゲートに負電位を印加すると、ドレイン電流は減衰曲線を描く。この時ｐチャネルが形成される。また、極性基を有する有機低分子化合物にチャネル形成層が暴露されると、当該有機低分子化合物がチャネル形成層に侵入してドレイン電流が低下し、より低い減衰曲線を描く。
The inventor of Patent Document 1 is mostly in common with the author of Non-Patent Document 1. Patent Document 1 and Non-Patent Document 1 each disclose a sensor for an organic low-molecular-weight compound vapor having a polar group, using an organic field-effect transistor having oligoalkylthiophene as a channel formation layer. The polar group of the organic low molecular weight compound means an atomic group that imparts polarity (dipole moment) to the organic low molecular weight compound, such as an alcoholic or phenolic hydroxyl group, a carboxyl group, a carbonyl group, an amino group or the like. As is well known, it is assumed that toluene also has a dipole moment between a methyl group and a phenyl group and is included in an organic low-molecular compound having a polar group.
As described in Patent Document 1 and Non-Patent Document 1, when a negative potential is applied to the drain and a negative potential is applied to the gate, the drain current draws an attenuation curve. At this time, a p-channel is formed. Further, when the channel forming layer is exposed to the organic low molecular compound having a polar group, the organic low molecular compound enters the channel forming layer, the drain current is reduced, and a lower attenuation curve is drawn.
特許文献１においては、その図９に示される通り、濃度測定状態の前に、ドレインに負電位、ゲートに負電位を印加した後、３段階にドレイン電位及びゲート電位を変化させて初期状態を復活させるようにしている。本発明者らが調べたところ、例えばドレインに負電位、ゲートに負電位を印加した後、ドレインの負電位を保ったまま、ゲートに直前の負電位と絶対値が等しい正電位を加えると、状態が安定しないことが分かった。即ち、ドレインの負電位を保ったまま、ゲートに負電位を印加する測定時と、ゲートに絶対値が等しい正電位を加える状態とを繰り返した場合、有機低分子化合物が低濃度の場合は、例えばゲートを負電位にした直後のドレイン電流は、ほぼ同じ値を示す。一方、有機低分子化合物が高濃度の場合は、例えばゲートを負電位にした直後のドレイン電流は、絶対値が低い値を示した後、ゲート電位の正負を切り替える毎にだんだん上昇して、プラトー状態になるまでに時間がかかった。 In Patent Document 1, as shown in FIG. 9, before the concentration measurement state, a negative potential is applied to the drain and a negative potential is applied to the gate, and then the drain potential and the gate potential are changed in three stages to change the initial state. I am trying to revive. When the inventors investigated, for example, after applying a negative potential to the drain and a negative potential to the gate, applying a positive potential having the same absolute value as the previous negative potential while maintaining the negative potential of the drain, It turns out that the condition is not stable. That is, when the measurement of applying a negative potential to the gate while maintaining the negative potential of the drain and the state of applying a positive potential having the same absolute value to the gate are repeated, when the organic low molecular weight compound has a low concentration, For example, the drain current immediately after the gate is set to a negative potential shows almost the same value. On the other hand, when the organic low molecular weight compound has a high concentration, for example, the drain current immediately after the gate is set to a negative potential increases gradually each time the gate potential is switched between positive and negative after showing a low absolute value. It took time to reach the state.
本発明は、有機電界効果トランジスタを用いたセンサの使用時に、ドレインの電位を保ったままの場合に、ゲート電位をチャネル形成の電位とした直後（オン直後）のドレイン電流の絶対値が、ゲート電位の切り替えを繰り返す初期段階で、極端に低い値をとらないようにするすることを目的とする。 In the present invention, when a sensor using an organic field effect transistor is used, when the drain potential is kept, the absolute value of the drain current immediately after setting the gate potential to the channel formation potential (immediately after turning on) is An object is to prevent an extremely low value from being taken at an initial stage in which potential switching is repeated.
請求項１に係る発明は、一方の面が外部に暴露された状態の膜状に形成された有機材料から成るチャネル形成層を有する有機電界効果トランジスタを用いた、極性分子を検出するセンサの使用方法であって、ゲート電極に、チャネルを形成すべき電位と、チャネルを開放すべき電位の２つの電位を交互に連続的に印加するに際し、ソース電極の電位とドレイン電極の電位を一定に保持して、ゲート電極に印加するチャネルを開放すべき電位を、チャネルを形成すべき電位よりも絶対値が小さく、正負を反転した電位とし、ゲート電極を、チャネルを形成すべき電位にした時刻又は当該時刻から所定の時間経過した後のドレイン電流を検出することで、膜状に形成された有機材料が暴露された空間の、極性分子の不存在を含む濃度を測定することを特徴とするセンサの使用方法である。
本明細書において、チャネルを開放するとは、チャネルが消滅する、又はドレイン電流が極めて小さくなる位にチャネルが薄くなることを意味するものとする。
請求項２に係る発明は、検出すべきドレイン電流は、ピーク値又は瞬間値であり、ゲート電極に、チャネルを形成すべき電位と、チャネルを開放すべき電位の２つの電位を交互に連続的に印加するに際し、当該ドレイン電流のピーク値又は瞬間値を連続的に検出することを特徴とする。
The invention according to claim 1 uses a sensor for detecting polar molecules, which uses an organic field-effect transistor having a channel-forming layer made of an organic material formed in a film shape with one surface exposed to the outside. In this method, when the potential to form a channel and the potential to open the channel are alternately applied to the gate electrode in succession, the potential of the source electrode and the potential of the drain electrode are kept constant. Then, the potential to open the channel to be applied to the gate electrode is set to a potential having an absolute value smaller than the potential to form the channel and inverted between positive and negative, and the gate electrode is set to the potential to form the channel or By detecting the drain current after a lapse of a predetermined time from that time, the concentration including the absence of polar molecules in the space where the organic material formed in the form of a film is exposed can be measured. A method using a sensor according to claim.
In this specification, opening a channel means that the channel is thinned to such an extent that the channel disappears or the drain current becomes extremely small.
According to the second aspect of the present invention, the drain current to be detected is a peak value or an instantaneous value, and two potentials of a potential for forming a channel and a potential for opening the channel are alternately and continuously applied to the gate electrode. When the voltage is applied, the peak value or instantaneous value of the drain current is continuously detected.
請求項３に係る発明は、有機電界効果トランジスタがｐチャネルＦＥＴであることを特徴とする。
請求項４に係る発明は、有機材料がペンタセンであることを特徴とする。
請求項５に係る発明は、一方の面が外部に暴露された状態の膜状に形成された有機材料から成るチャネル形成層を有する有機電界効果トランジスタを用いた極性分子を検出するセンサ装置において、チャネル形成層に接続し、相互に離間したソース電極とドレイン電極と、ソース電極とドレイン電極との間のチャネル形成層に電界を印加するゲート電極と、ゲート電極に、チャネルを形成すべき電位と、チャネルを開放すべき電位の２つの電位を交互に連続的に印加し、ソース電極の電位とドレイン電極の電位を一定に保持して、ゲート電極に印加するチャネルを開放すべき電位を、チャネルを形成すべき電位よりも絶対値が小さく、正負を反転した電位とする電圧印加手段と、ゲート電極を、チャネルを形成すべき電位にした時刻又は当該時刻から所定の時間経過した後のドレイン電流を検出することで、膜状に形成された有機材料が暴露された空間の、極性分子の不存在を含む濃度を測定する測定手段と、を有することを特徴とするセンサ装置である。
The invention according to claim 3 is characterized in that the organic field effect transistor is a p-channel FET.
The invention according to claim 4 is characterized in that the organic material is pentacene.
The invention according to claim 5 is a sensor device for detecting polar molecules using an organic field effect transistor having a channel forming layer made of an organic material formed in a film shape in which one surface is exposed to the outside. A source electrode and a drain electrode which are connected to the channel formation layer and spaced apart from each other; a gate electrode which applies an electric field to the channel formation layer between the source electrode and the drain electrode; and a potential at which a channel is to be formed in the gate electrode; The two potentials of the potential to open the channel are alternately applied continuously, the potential of the source electrode and the drain electrode are kept constant, and the potential to be applied to the gate electrode The voltage application means which makes the absolute value smaller than the potential to form and reverses positive and negative and the time when the gate electrode is set to the potential to form the channel or And measuring means for measuring the concentration including the absence of polar molecules in the space where the organic material formed in a film shape is exposed by detecting the drain current after a predetermined time has elapsed since the time It is a sensor apparatus characterized by these.
ソース電極の電位とドレイン電極の電位を一定に保ったまま、ゲート電極に、チャネルを形成すべき電位と、チャネルを開放すべき電位の２つの電位を交互に連続的に印加する方法においては、ゲート電極にチャネルを形成すべき電位を印加した瞬間又は微小な時間経過後のドレイン電流が安定することが好ましい。この場合、下記に示す通り、ゲートに負電位を印加する測定時と、ゲートに絶対値が等しい正電位を加える状態とを繰り返した場合に、特に有機低分子化合物が高濃度の場合に当該ドレイン電流のピークが極端に低い場合がある。
本発明によれば、当該ドレイン電流のピークが極端に低くなることがないため、例えば高濃度で警報を発する目的でセンサを使用する場合に、本来の濃度よりも高い濃度を誤検出するようなことがない。
In a method in which two potentials of a potential to form a channel and a potential to open a channel are alternately and continuously applied to the gate electrode while keeping the potential of the source electrode and the potential of the drain electrode constant, It is preferable that the drain current is stabilized at the moment when a potential for forming a channel is applied to the gate electrode or after a minute time has elapsed. In this case, as shown below, when the measurement of applying a negative potential to the gate and the state of applying a positive potential having the same absolute value to the gate are repeated, particularly when the organic low molecular weight compound has a high concentration, the drain The current peak may be extremely low.
According to the present invention, since the peak of the drain current does not become extremely low, for example, when a sensor is used for the purpose of issuing an alarm at a high concentration, a concentration higher than the original concentration is erroneously detected. There is nothing.
本発明の効果の理由、即ち作用原理は例えば次のように仮定できる。
有機電界効果トランジスタのチャネル形成層の有機材料は、ソース−ドレイン間の電位差が極端に大きいか、ゲートが負電位にならないと帯電しにくく、チャネルも形成されにくい。チャネルは特にｐチャネルの場合に、この傾向が高い。
チャネルが形成される場合は、初期段階で、帯電するためにはじき出された電子によるドレイン電流が多く流れる。この後、純粋なｐチャネルのみとなって、ドレイン電流が正孔によるものみとなり、安定する。この、純粋なｐチャネルになるまでに時間がかかるのでドレイン電流は減衰曲線を描く。
チャネル形成層は完全な単結晶から構成されているのではないので、粒子界面に極性分子が侵入しやすい。これを利用してチャネル形成層を薄く形成すると、極性分子の侵入によりｐチャネルの形成に大きく影響する。例えば極性分子によりｐチャネルを形成する例えばラジカルカチオンが安定化してしまう（トラップされる）と、当該ラジカルカチオンは正孔の輸送に携われないと考えられ、ドレイン電流の減少を引き起こす。
そこで、有機電界効果トランジスタをガスセンサとして用いる場合に、ゲート電位の変化を繰り返して、ｐチャネルを形成／開放を繰り返すことで、例えばチャネルが形成される初期段階のドレイン電流のピーク値を繰り返し検出する手法がある。
この場合に、ｐチャネルの開放（ｐチャネルの消滅）のために、ｐチャネルを形成するときのゲートの負電位と、絶対値の等しい正電位をゲートに印加すると、極性分子の電子密度の多い原子団部分が、ゲート絶縁膜付近に集中し、ｐチャネルの形成を妨げるものと考えられる。この後、ゲート電位の正負の切替えを繰り返してｐチャネルの形成が安定すると、ゲート絶縁膜付近に極性分子が過度に集中することは無くなるが、高濃度の極性分子に暴露されてからしばらくの間は、ゲート電位が負になる瞬間のドレイン電流のピーク値が小さくなる、即ち本来の極性分子濃度に対応すべきドレイン電流よりも、高い濃度に対応する低いドレイン電流が検出されてしまう。
本願発明によれば、ゲートの切替えの際に、極性分子が過度にゲート絶縁膜付近に集中することが無くなり、本来の極性分子濃度に対応すべきドレイン電流よりも、高い濃度に対応する低いドレイン電流が検出されてしまうことはない。
The reason for the effect of the present invention, that is, the principle of operation can be assumed as follows, for example.
The organic material of the channel formation layer of the organic field effect transistor is not easily charged unless the potential difference between the source and the drain is extremely large or the gate does not have a negative potential, and the channel is not easily formed. This tendency is high especially when the channel is a p-channel.
When a channel is formed, a large amount of drain current flows due to the electrons ejected to be charged in the initial stage. After this, only a pure p-channel is obtained, and the drain current is only due to holes, and is stabilized. Since it takes time to become a pure p-channel, the drain current draws an attenuation curve.
Since the channel forming layer is not composed of a complete single crystal, polar molecules easily enter the particle interface. If the channel formation layer is formed thin by utilizing this, the formation of the p-channel is greatly affected by the penetration of polar molecules. For example, if a radical cation that forms a p-channel with a polar molecule, for example, is stabilized (trapped), the radical cation is considered not to be involved in hole transport, causing a decrease in drain current.
Therefore, when an organic field effect transistor is used as a gas sensor, for example, the peak value of the drain current at the initial stage where the channel is formed is repeatedly detected by repeatedly changing the gate potential and repeatedly forming / opening the p-channel. There is a technique.
In this case, when a negative potential of the gate when forming the p channel and a positive potential having an absolute value equal to the absolute value are applied to the gate in order to open the p channel (disappearance of the p channel), the electron density of the polar molecule is large. It is considered that the atomic group portion concentrates in the vicinity of the gate insulating film and prevents the formation of the p channel. After this, if the formation of the p-channel is stabilized by repeatedly switching the gate potential between positive and negative, polar molecules will not be excessively concentrated near the gate insulating film, but for a while after being exposed to a high concentration of polar molecules. The peak value of the drain current at the moment when the gate potential becomes negative becomes small, that is, a lower drain current corresponding to a higher concentration than the drain current that should correspond to the original polar molecule concentration is detected.
According to the present invention, when the gate is switched, polar molecules are not excessively concentrated in the vicinity of the gate insulating film, and a low drain corresponding to a higher concentration than a drain current that should correspond to the original polar molecule concentration. The current is never detected.
図１．Ａ及び図１．Ｂは、現在広く開発されている有機電界効果トランジスタ１００及び２００の構成を示す断面図である。
図１．Ａは素子基板として、導電性の材料を用いる場合の構成の一例である。
図１．Ａの有機電界効果トランジスタ１００は、導電性基板１０表面に絶縁膜２０を形成し、その上にチャネル形成層である有機半導体層３０を形成する。導電性基板１０裏面にはゲート電極４０ｇを形成し、有機半導体表面には、チャネル長を空けてソース電極４０ｓとドレイン電極４０ｄが形成される。各層の膜厚等は任意であるが、絶縁膜２０は例えば１００ｎｍ〜１μｍ、有機半導体層３０は例えば５〜１００ｎｍの範囲で形成すると良い。チャネル長は１０μｍ〜１ｍｍの範囲で設計される。チャネル幅は任意であるが、１００μｍ〜１０ｍｍぐらいとすると良い。
FIG. A and FIG. B is a cross-sectional view showing a configuration of organic field effect transistors 100 and 200 that are currently widely developed.
FIG. A is an example of a configuration in which a conductive material is used as the element substrate.
FIG. In the organic field effect transistor 100 of A, the insulating film 20 is formed on the surface of the conductive substrate 10, and the organic semiconductor layer 30 that is a channel forming layer is formed thereon. A gate electrode 40g is formed on the back surface of the conductive substrate 10, and a source electrode 40s and a drain electrode 40d are formed on the surface of the organic semiconductor with a channel length. The thickness of each layer is arbitrary, but the insulating film 20 is preferably formed in a range of 100 nm to 1 μm, for example, and the organic semiconductor layer 30 is preferably formed in a range of 5 to 100 nm, for example. The channel length is designed in the range of 10 μm to 1 mm. The channel width is arbitrary, but is preferably about 100 μm to 10 mm.
図１．Ｂは素子基板として、誘電体材料を用いる場合の構成の一例である。
図１．Ｂの有機電界効果トランジスタ２００は、誘電体基板１１表面にゲート電極４１ｇを形成し、それを覆うように絶縁膜２１を形成する。表面には、チャネル長を空けてソース電極４１ｓとドレイン電極４１ｄが形成される。こうして、ソース電極４１ｓとドレイン電極４１ｄとに挟まれた絶縁膜２１表面を少なくとも覆うように、有機半導体層３１を形成する。各層の膜厚等は任意であるが、絶縁膜２１のゲート電極４１ｇと有機半導体層３１とで挟まれた領域の厚さは例えば１００ｎｍ〜１μｍ、有機半導体層３１のソース電極４１ｓとドレイン電極４１ｄとに挟まれた絶縁膜２１表面上の厚さは例えば５〜１００ｎｍの範囲で形成すると良い。尚、ソース電極４１ｓとドレイン電極４１ｄとは当該有機半導体層３１の厚さより薄く形成する。チャネル長は１０μｍ〜１ｍｍの範囲で設計される。チャネル幅は任意であるが、１００μｍ〜１０ｍｍぐらいとすると良い。
FIG. B is an example of a configuration in which a dielectric material is used as the element substrate.
FIG. In the B organic field effect transistor 200, the gate electrode 41g is formed on the surface of the dielectric substrate 11, and the insulating film 21 is formed so as to cover the gate electrode 41g. On the surface, a source electrode 41s and a drain electrode 41d are formed with a channel length. Thus, the organic semiconductor layer 31 is formed so as to cover at least the surface of the insulating film 21 sandwiched between the source electrode 41s and the drain electrode 41d. The thickness of each layer is arbitrary, but the thickness of the region sandwiched between the gate electrode 41g of the insulating film 21 and the organic semiconductor layer 31 is, for example, 100 nm to 1 μm, and the source electrode 41s and the drain electrode 41d of the organic semiconductor layer 31. The thickness on the surface of the insulating film 21 sandwiched between the layers is preferably in the range of 5 to 100 nm, for example. The source electrode 41s and the drain electrode 41d are formed thinner than the thickness of the organic semiconductor layer 31. The channel length is designed in the range of 10 μm to 1 mm. The channel width is arbitrary, but is preferably about 100 μm to 10 mm.
図１．Ａの導電性基板１０としては、所望の任意の導電性材料から成る基板を用いることができるが、例えば導電性シリコン基板（ｎ型が好ましい）を用いると、絶縁膜２０の形成を熱酸化により形成できるので好適である。
図１．Ｂの誘電体基板１１としては、所望の任意の誘電体材料から成る基板を用いることができる。例えば任意のプラスチック基板、ガラス基板、石英基板、セラミック基板を用いることができる。
図１．Ａの絶縁膜２０及び図１．Ｂの絶縁膜２１としては、ＳｉＯ2、Ｓｉ3Ｎ4、ＳｉＯＮ、Ａｌ2Ｏ3、Ｔａ2Ｏ5 アモルファスシリコン、ポリイミド樹脂、ポリビニルフェノール樹脂、ポリパラキシリレン樹脂、ポリメチルメタクリレート樹脂等の材料を用い、真空蒸着法、電子ビーム蒸着法、ＲＦスパッタ法、陽極酸化法または印刷法等の周知の膜作製方法により形成することもできる。
図１．Ａの有機半導体層３０及び図１．Ｂの有機半導体層３１としては、ペンタセン、チオフェン、ポリチオフェン、フタロシアニンなどの既に公知となった有機半導体を用い得ることは勿論、任意の有機半導体を適用し得る。また、有機半導体層は、真空蒸着法、スピンコート法、インクジェット法、印刷法等の周知の膜作製方法により形成できる。
図１．Ａのゲート電極４０ｇ及び図１．Ｂのゲート電極４１ｇとしては、アルミニウム、金、白金、クロム、タングステン、タンタル、ニッケル、銅、銀、マグネシウム、カルシウム等の金属、あるいはそれらの合金、およびポリシリコン、アモルファスシリコン、グラファイト、酸化インジウムスズ（ＩＴＯ）、酸化亜鉛、導電性ポリマー等の材料を用い得る。これらを、真空蒸着法、電子ビーム蒸着法、ＲＦスパッタ法または印刷法等の周知の膜作製方法によりゲート電極４０ｇ及び４１ｇを形成することができる。
ドレイン電極４０ｄ、４１ｄおよびソース電極４０ｓ、４１ｓも、ゲート電極と同様の材料から選択し、同様の形成方法から選択することで、形成可能である。密着性をあげるために、積層構造としても良い。
FIG. As the conductive substrate 10 of A, a substrate made of any desired conductive material can be used. For example, when a conductive silicon substrate (preferably n-type) is used, the insulating film 20 is formed by thermal oxidation. Since it can form, it is suitable.
FIG. As the dielectric substrate 11 for B, a substrate made of any desired dielectric material can be used. For example, any plastic substrate, glass substrate, quartz substrate, or ceramic substrate can be used.
FIG. A insulating film 20 and FIG. As the insulating film 21 of B, materials such as SiO 2 , Si 3 N 4 , SiON, Al 2 O 3 , Ta 2 O 5 amorphous silicon, polyimide resin, polyvinyl phenol resin, polyparaxylylene resin, polymethyl methacrylate resin, etc. The film can be formed by a known film production method such as vacuum vapor deposition, electron beam vapor deposition, RF sputtering, anodic oxidation, or printing.
FIG. A organic semiconductor layer 30 and FIG. As the organic semiconductor layer 31 for B, an organic semiconductor that has been publicly known, such as pentacene, thiophene, polythiophene, and phthalocyanine, can be used, and an arbitrary organic semiconductor can be applied. The organic semiconductor layer can be formed by a well-known film manufacturing method such as a vacuum deposition method, a spin coating method, an ink jet method, or a printing method.
FIG. A gate electrode 40g and FIG. As the B gate electrode 41g, metals such as aluminum, gold, platinum, chromium, tungsten, tantalum, nickel, copper, silver, magnesium, calcium, or alloys thereof, and polysilicon, amorphous silicon, graphite, indium tin oxide, etc. Materials such as (ITO), zinc oxide, and conductive polymer can be used. With these, the gate electrodes 40g and 41g can be formed by a well-known film manufacturing method such as a vacuum evaporation method, an electron beam evaporation method, an RF sputtering method, or a printing method.
The drain electrodes 40d and 41d and the source electrodes 40s and 41s can also be formed by selecting from the same material as the gate electrode and selecting from the same formation method. In order to increase the adhesion, a laminated structure may be used.
図１．Ａに示す積層構造の有機電界効果トランジスタ１００を作製した。導電性基板１０にはアンチモン（Ｓｂ）がドープされ，抵抗率が０．０２Ωｃｍ以下のシリコン（Ｓｉ）ウェハを用いた。シリコン（Ｓｉ）から成る導電性基板１０の表面を熱酸化して、厚さ３００ｎｍのＳｉＯ2から成る絶縁膜２０を形成した。絶縁体容量は１０ｎＦ／ｃｍ2であった。有機半導体として、ペンタセン（Ｃ22Ｈ14）を真空蒸着法により３０ｎｍの厚さで成膜し、有機半導体層３０を形成した。有機半導体層３０上に、メカニカルマスクを用いて金（Ａｕ）を蒸着し、各々厚さ３０ｎｍのソース電極４０ｓならびにドレイン電極４０ｄを形成した。チャンネル長は０．２ｍｍ、チャンネル幅は５ｍｍとした。この後、シリコン（Ｓｉ）から成る導電性基板１０裏面にアルミニウム（Ａｌ）を蒸着し、厚さ１００ｎｍのゲート電極４０ｇを形成した。 FIG. An organic field effect transistor 100 having a laminated structure shown in A was produced. The conductive substrate 10 was a silicon (Si) wafer doped with antimony (Sb) and having a resistivity of 0.02 Ωcm or less. The surface of the conductive substrate 10 made of silicon (Si) was thermally oxidized to form an insulating film 20 made of SiO 2 having a thickness of 300 nm. The insulator capacity was 10 nF / cm 2 . As an organic semiconductor, pentacene (C 22 H 14 ) was formed into a film with a thickness of 30 nm by a vacuum vapor deposition method to form an organic semiconductor layer 30. Gold (Au) was deposited on the organic semiconductor layer 30 using a mechanical mask to form a source electrode 40s and a drain electrode 40d each having a thickness of 30 nm. The channel length was 0.2 mm and the channel width was 5 mm. Thereafter, aluminum (Al) was vapor-deposited on the back surface of the conductive substrate 10 made of silicon (Si) to form a gate electrode 40g having a thickness of 100 nm.
図１．Ａの有機電界効果トランジスタ１００の特性を次のように調べた。
まず、有機電界効果トランジスタ１００を、エタノール蒸気を導入可能な密閉容器に配置した。この際、有機半導体層３０の表面３０ｓは当該密閉容器内の気体に暴露された状態となった。
次に、ソース電極４０ｓを接地電位とし、ドレイン電極４０ｄに−５０Ｖ印加し、保持した。
ゲート電極４０ｇには、有機半導体層３０にｐチャネルが形成されてトランジスタがオンとなる負電位として−５０Ｖの印加と、有機半導体層３０からｐチャネルが消滅する電位の印加とを、各々１秒ずつ連続的に印加した。
この後、エタノール蒸気を順次密閉容器に導入して、密閉容器内のエタノール濃度を、０ｐｐｍ、２００ｐｐｍ、５００ｐｐｍ、１０００ｐｐｍ、２０００ｐｐｍ、５０００ｐｐｍと段階的に上昇させた。
こうして、ゲート電極４０ｇが−５０Ｖになった後のドレイン電流のピーク値を、２秒毎に測定し、プロットした結果を図２に示す。
FIG. The characteristics of the organic field effect transistor 100 of A were examined as follows.
First, the organic field effect transistor 100 was placed in a sealed container into which ethanol vapor could be introduced. At this time, the surface 30s of the organic semiconductor layer 30 was exposed to the gas in the sealed container.
Next, the source electrode 40 s was set to the ground potential, and −50 V was applied to the drain electrode 40 d and held.
For the gate electrode 40g, -50V is applied as a negative potential at which a p-channel is formed in the organic semiconductor layer 30 and the transistor is turned on, and a potential at which the p-channel disappears from the organic semiconductor layer 30 is 1 second each. They were applied continuously.
Thereafter, ethanol vapor was sequentially introduced into the sealed container, and the ethanol concentration in the sealed container was gradually increased to 0 ppm, 200 ppm, 500 ppm, 1000 ppm, 2000 ppm, and 5000 ppm.
Thus, the peak value of the drain current after the gate electrode 40g becomes -50V is measured every 2 seconds, and the plotted result is shown in FIG.
図２は、有機電界効果トランジスタ１００の特性を３つの使用方法により調べた特性を示すグラフ図である。
図２においてはゲート電極４０ｇに印加した電位として３つの場合を示している。
実験１は、ゲート電極４０ｇに印加する、有機半導体層３０からｐチャネルが消滅する電位を３０Ｖとした場合である。これは有機半導体層３０にｐチャネルが形成されてトランジスタがオンとなる電位−５０Ｖよりも絶対値が小さく、正負が反転した電位であり、本願発明に含まれる。
実験２は、ゲート電極４０ｇに印加する、有機半導体層３０からｐチャネルが消滅する電位を０Ｖとした場合である。
比較例は、ゲート電極４０ｇに印加する、有機半導体層３０からｐチャネルが消滅する電位を５０Ｖとした場合である。これは有機半導体層３０にｐチャネルが形成されてトランジスタがオンとなる電位−５０Ｖの正負が反転した電位であり、本願発明に含まれない。
FIG. 2 is a graph showing characteristics obtained by examining the characteristics of the organic field effect transistor 100 by three usage methods.
FIG. 2 shows three cases as potentials applied to the gate electrode 40g.
Experiment 1 is a case where the potential at which the p-channel disappears from the organic semiconductor layer 30 applied to the gate electrode 40g is 30V. This is a potential having an absolute value smaller than the potential −50 V at which the p-channel is formed in the organic semiconductor layer 30 and the transistor is turned on, and the polarity is inverted, and is included in the present invention.
Experiment 2 is a case where the potential at which the p-channel disappears from the organic semiconductor layer 30 applied to the gate electrode 40g is 0V .
In the comparative example, the potential at which the p-channel disappears from the organic semiconductor layer 30 applied to the gate electrode 40g is 50V. This is a potential obtained by reversing the positive / negative potential of −50 V at which the p-channel is formed in the organic semiconductor layer 30 and the transistor is turned on, and is not included in the present invention.
図２に示された通り、トランジスタがオンとなる電位−５０Ｖの正負が反転した電位をオフ時にゲート電位とした場合（比較例）、エタノール濃度が上昇してから一定時間、ドレイン電流のピークが大きく減少する（エタノール濃度を実際よりも大きいと検出する）過渡応答が見られる。これは、ドレイン電流のピーク（オン時の初期電流）が安定するまでに数分待たなければいけないことを示し、エタノールセンサとして使いづらいことがわかる。
実験１のように、トランジスタがオンとなる電位−５０Ｖよりも絶対値が小さく、正負が反転した電位をオフ時にゲート電位とした場合、やはり過渡現象が見られるが、比較例よりも改善されている。
実験２のように、接地電位をオフ時にゲート電位とした場合、エタノール濃度が２０００ｐｐｍ以上では過渡現象が見られるものの、比較例よりも改善されている。また、エタノール濃度が１０００ｐｐｍ以下では過渡現象は見られない。特に、エタノール濃度を実際よりも大きいと検出することが無い。即ち、エタノールセンサとして使い安いことがわかる。
As shown in FIG. 2, when the potential at which the transistor is turned on, which is the inverted potential of −50 V, is set as the gate potential when turned off (comparative example), the drain current peak is maintained for a certain time after the ethanol concentration increases. There is a transient response that greatly decreases (detects that the ethanol concentration is greater than actual). This indicates that it is necessary to wait several minutes for the drain current peak (initial current at the time of on-state) to stabilize, and it can be seen that it is difficult to use as an ethanol sensor.
As in Experiment 1, when the absolute value is smaller than the potential -50V at which the transistor is turned on and the potential that is inverted between positive and negative is used as the gate potential at the time of turning off, a transient phenomenon can still be seen, but this is an improvement over the comparative example. Yes.
As in Experiment 2, when the ground potential is set to the gate potential when OFF, a transient phenomenon is observed when the ethanol concentration is 2000 ppm or more, but this is an improvement over the comparative example. Further, no transient phenomenon is observed when the ethanol concentration is 1000 ppm or less. In particular, it is not detected that the ethanol concentration is larger than the actual concentration. That is, it can be seen that it is cheap to use as an ethanol sensor.
このように、本発明によると、例えば一定以上の極性ガス濃度を検出した場合に警報を発するためのセンサとしては、ガス濃度を実際よりも大きいと検出する過渡現象が生ぜず、極めて好適である。 As described above, according to the present invention, for example, a sensor for issuing an alarm when a polar gas concentration of a certain level or more is detected does not cause a transient phenomenon to detect that the gas concentration is larger than the actual concentration, and is extremely suitable. .
図１．Ｂに示す積層構造の有機電界効果トランジスタ２００を作製した。誘電体基板１１には厚さ０．１ｍｍのポリエチレンテレフタレート（ＰＥＴ）を用いた。
ＰＥＴから成る誘電体基板１１表面に、ＩＴＯから成る厚さ１００ｎｍのゲート電極４１ｇを形成した。この際、ＩＴＯターゲットを用い、１％の酸素を含むアルゴンガス（３．０×１０-3Ｔｏｒｒ）中、２００Ｗでスパッタ成膜を実施した。
ＩＴＯから成るゲート電極４１ｇの上に、ポリビニルフェノールコポリマーから成る絶縁膜１１を形成した。濃度２００ｇ／ＬのＮ−メチルピロリドン溶液を用いたスピンコート法を用いた。回転数は２０００ｒｐｍ、１５０℃の熱処理を行った。絶縁体容量は９．２ｎＦ／ｃｍ2であった。この上に、メカニカルマスクを用いてクロム（Ｃｒ）、金（Ａｕ）の順に蒸着し、各々厚さ５ｎｍ、２５ｎｍの二重層であるソース電極４１ｓならびにドレイン電極４１ｄを形成した。チャンネル長は０．２ｍｍ、チャンネル幅は５ｍｍとした。最後にペンタセンを０．１ｎｍ／分で２０ｎｍの厚さに蒸着して、有機半導体層３１を形成した。
有機電界効果トランジスタ２００のセンサ特性を調べたところ、実施例１と同様の傾向が見られた。
FIG. An organic field effect transistor 200 having a laminated structure shown in B was produced. Polyethylene terephthalate (PET) having a thickness of 0.1 mm was used for the dielectric substrate 11.
On the surface of the dielectric substrate 11 made of PET, a gate electrode 41g made of ITO and having a thickness of 100 nm was formed. At this time, using an ITO target, sputter film formation was performed at 200 W in an argon gas containing 1% oxygen (3.0 × 10 −3 Torr).
An insulating film 11 made of polyvinylphenol copolymer was formed on the gate electrode 41g made of ITO. A spin coating method using an N-methylpyrrolidone solution having a concentration of 200 g / L was used. Heat treatment was performed at a rotational speed of 2000 rpm and 150 ° C. The insulator capacity was 9.2 nF / cm 2 . On top of this, chromium (Cr) and gold (Au) were deposited in this order using a mechanical mask to form a source electrode 41s and a drain electrode 41d, which are double layers of 5 nm and 25 nm, respectively. The channel length was 0.2 mm and the channel width was 5 mm. Finally, pentacene was deposited at a thickness of 20 nm at a rate of 0.1 nm / min to form the organic semiconductor layer 31.
When the sensor characteristics of the organic field effect transistor 200 were examined, the same tendency as in Example 1 was observed.
本発明は、極性低分子有機化合物の検出、特に呼気からエタノール濃度を測定するためのセンサの使用方法として好適である。 The present invention is suitable as a method for using a sensor for detecting a polar low molecular weight organic compound, particularly for measuring ethanol concentration from exhaled breath.
１００、２００：有機電界効果トランジスタ
１０：導電性基板
１１：誘電体基板
２０、２１：絶縁膜
３０、３１：有機半導体層（有機材料からなるチャネル形成層）
４０ｇ、４１ｇ：ゲート電極
100, 200: Organic field effect transistor 10: Conductive substrate 11: Dielectric substrate 20, 21: Insulating film 30, 31: Organic semiconductor layer (channel forming layer made of organic material)
40g, 41g: gate electrode
Claims (5)
ゲート電極に、チャネルを形成すべき電位と、チャネルを開放すべき電位の２つの電位を交互に連続的に印加するに際し、
ソース電極の電位とドレイン電極の電位を一定に保持して、前記ゲート電極に印加する前記チャネルを開放すべき電位を、前記チャネルを形成すべき電位よりも絶対値が小さく、正負を反転した電位とし、
前記ゲート電極を、前記チャネルを形成すべき電位にした時刻又は当該時刻から所定の時間経過した後のドレイン電流を検出することで、前記膜状に形成された有機材料が暴露された空間の、前記極性分子の不存在を含む濃度を測定することを特徴とするセンサの使用方法。 A method of using a sensor for detecting polar molecules using an organic field-effect transistor having a channel forming layer made of an organic material formed into a film with one surface exposed to the outside,
When two potentials, that is, a potential at which a channel is to be formed and a potential at which a channel is to be opened, are alternately and continuously applied to the gate electrode,
Holding the potential of the potential and the drain electrode of the source electrode to a constant, pre-Symbol potential to be opening the channel to be applied to the gate electrode, before Symbol smaller absolute value than the potential to form the channel, negate Potential ,
By detecting the drain current after the gate electrode is set to the potential at which the channel is to be formed or a predetermined time has elapsed from the time, the space where the organic material formed in the film shape is exposed, A method for using a sensor, comprising measuring a concentration including the absence of the polar molecule.
前記ゲート電極に、前記チャネルを形成すべき電位と、前記チャネルを開放すべき電位の２つの電位を交互に連続的に印加するに際し、当該前記ドレイン電流のピーク値又は瞬間値を連続的に検出することを特徴とする請求項１に記載のセンサの使用方法。 The drain current to be detected is a peak value or an instantaneous value,
When the two potentials of the potential to form the channel and the potential to open the channel are alternately and continuously applied to the gate electrode, the peak value or instantaneous value of the drain current is continuously detected. The method of using the sensor according to claim 1.
前記チャネル形成層に接続し、相互に離間したソース電極とドレイン電極と、A source electrode and a drain electrode connected to the channel formation layer and spaced apart from each other;
前記ソース電極と前記ドレイン電極との間の前記チャネル形成層に電界を印加するゲート電極と、A gate electrode for applying an electric field to the channel formation layer between the source electrode and the drain electrode;
前記ゲート電極に、チャネルを形成すべき電位と、チャネルを開放すべき電位の２つの電位を交互に連続的に印加し、前記ソース電極の電位と前記ドレイン電極の電位を一定に保持して、前記ゲート電極に印加する前記チャネルを開放すべき電位を、前記チャネルを形成すべき電位よりも絶対値が小さく、正負を反転した電位とする電圧印加手段と、Two potentials, that is, a potential for forming a channel and a potential for opening a channel are alternately and continuously applied to the gate electrode, and the potential of the source electrode and the potential of the drain electrode are held constant, Voltage application means for setting the potential to open the channel to be applied to the gate electrode to a potential having an absolute value smaller than the potential to form the channel and inversion of positive and negative;
前記ゲート電極を、前記チャネルを形成すべき電位にした時刻又は当該時刻から所定の時間経過した後のドレイン電流を検出することで、前記膜状に形成された有機材料が暴露された空間の、前記極性分子の不存在を含む濃度を測定する測定手段と、By detecting the drain current after the gate electrode is set to the potential at which the channel is to be formed or a predetermined time has elapsed from the time, the space where the organic material formed in the film shape is exposed, Measuring means for measuring the concentration including the absence of the polar molecule;
を有することを特徴とするセンサ装置。A sensor device comprising:
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