Monolayer Organic Field-effect Transistors Research Articles

Sensitivity of gas sensors enhanced by functionalization of hexabenzoperylene in solution-processed monolayer organic field effect transistors.

Solution-processed monolayer films consisting of unfunctionalized and functionalized hexabenzoperylenes in a single homogeneous phase have enabled highly sensitive detection of NH3 and NO2 on the basis of organic field effect transistors.

(Invited) Self-Assembling Organic Semiconductors for Chemical Sensing

Self-assembling monolayers of organic semiconductors are promising for monolayer organic field-effect transistors (OFETs) and various devices based on them, in particular low power consumption integrated circuits and ultrasensitive gas sensors [1]. Recently we have developed highly stable organosilicon derivatives of organic semiconductor benzothieno[3,2-b][1]benzothiophene (BTBT) capable to self-assembly into a monolayer semiconducting film by Langmuir–Blodgett, Langmuir–Schaefer (LS) or spin-coating methods [2,3]. These monolayer films were used for preparation of OFET devices, which demonstrated excellent electrical performance with a hole mobility up to 7 × 10−2 cm2 V−1 s−1, a threshold voltage around 0 V and an on–off ratio of 105 as well as long-term stability of half-year storage under ambient conditions. They were successfully utilized for multiparamertic real time detection of NH3 and H2S in dry air [4]. Modified by additional metal-containing porphyrin receptor layer, two-layer OFETs were investigated as ultrasensitive gas sensors for NH3 and H2S real-time detection in the humid air [5]. Introduction of the receptor layers on top of the LS semiconducting monolayer provides the device sensitivity enhancement as well as allows tuning the sensor selectivity. They demonstrated the improvement of both the limit of detection (down to ca. 60−70 ppb) and sensitivity in the air with relative humidity up to 60 %. Impressive combination of the sensor high sensitivity and reproducibility with fast response and full recovery after finishing the analyte exposure enables utilizing the fabricated two-layer OFETs as chemo-sensors in real gas analyzing systems environmental pollutions control. This work was supported by the Russian Science Foundation (grant 19-73-30028).

NH3 and H2S real-time detection in the humid air by two-layer Langmuir-Schaefer OFETs

Development of highly-sensitive low-power low cost sensors for toxic gas detection is a challenging task for today. Here we present a novel simple and fast approach for fabrication of reusable gas sensors for NH3 and H2S real-time detection based on Langmuir-Schaefer (LS) monolayer organic field-effect transistors with an active layer modified by an additional metal-containing porphyrin receptor layer. The devices prepared worked at room temperature and were found to be highly sensitive to the presence of ammonia and hydrogen sulfide at concentrations lower than 1 ppm. They demonstrated the improvement of both limit of detection (down to ca. 60−70 ppb) and sensitivity in the air with relative humidity up to 60 % as compared to the LS monolayer devices without a receptor layer. Incorporation of the receptor layer on top of the LS semiconducting monolayer does not influence on its electrical performance, response and recovery times, while provides the device sensitivity enhancement as well as allows tuning the sensor selectivity. Impressive combination of the sensor high sensitivity and reproducibility with fast response and full recovery after finishing the analyte exposure enables utilizing the fabricated two-layer OFETs as chemo-sensors in real gas analyzing systems.

Highly Efficient Charge Transport in a Quasi‐Monolayer Semiconductor on Pure Polymer Dielectric

AbstractThe study of monolayer organic field‐effect transistors (MOFETs) provides an effective way to investigate the intrinsic charge transport of semiconductors. To date, the research based on organic monolayers on polymeric dielectrics lays far behind that on inorganic dielectrics and the realization of a bulk‐like carrier mobility on pure polymer dielectrics is still a formidable challenge for MOFETs. Herein, a quasi‐monolayer coverage of pentacene film with orthorhombic phase is grown on the poly (amic acid) (PAA) dielectric layer. More significantly, charge density redistribution occurs at the interface between the pentacene and PAA caused by electron transfer from pentacene to the PAA dielectric layer, which is verified by theoretical simulations and experiments. As a consequence, an enhanced hole accumulation layer is formed and pentacene‐based MOFETs on pure polymer dielectrics exhibit bulk‐like carrier mobilities of up to 13.7 cm2 V−1 s−1 from the saturation region at low VGS, 9.1 cm2 V−1 s−1 at high VGS and 7.6 cm2 V−1 s−1 from the linear region, which presents one of the best results of previously reported MOFETs so far and indicates that the monolayer semiconductor growing on pure polymer dielectric could produce highly efficient charge transport.

Monolayer organic field-effect transistors

Monolayer organic field-effect transistors (OFETs) are attracting worldwide interest in device physics and novel applications due to their ultrathin active layer for two-dimensional charge transport. The monolayer films are generally prepared by thermal evaporation, the Langmuir technique or self-assembly process, etc., but their electrical performance is relatively lower than corresponding thick films. From 2011, the performance of monolayer OFETs has been boosted by using the monolayer molecular crystals (MMCs) as active channels, which opened up a new era for monolayer OFETs. In this review, recent progress of monolayer OFETs, including the preparation of monolayer films, their OFET performance and applications are summarized. Finally, perspectives of monolayer OFETs in the near future are also discussed.

Realizing low-voltage operating crystalline monolayer organic field-effect transistors with a low contact resistance

Monolayer crystals of 1,4-bis((5′-hexyl-2,2′-bithiophen-5-yl)ethynyl)benzene (HTEB) and their applications in low-voltage operating OFETs with a low bulk injection resistance (Rc,bulk) are presented.

Highly Sensitive Air-Stable Easily Processable Gas Sensors Based on Langmuir–Schaefer Monolayer Organic Field-Effect Transistors for Multiparametric H2S and NH3 Real-Time Detection

A combination of low limit of detection, low power consumption, and portability makes organic field-effect transistor (OFET) chemical sensors promising for various applications in the areas of industrial safety control, food spoilage detection, and medical diagnostics. However, the OFET sensors typically lack air stability and restoration capability at room temperature. Here, we report on a new design of highly sensitive gas sensors based on Langmuir-Schaefer monolayer organic field-effect transistors (LS OFETs) prepared from organosilicon derivative of [1]benzothieno[3,2- b][1]-benzothiophene. The devices fabricated are able to operate in air and allow an ultrafast detection of different analytes at low concentrations down to tens of parts per billion. The sensors are reusable and can be utilized in real-time air-quality monitoring systems. We show that a direct current response of the LS OFET can be split into the alteration of various transistor parameters, responsible for the interactions with different toxic gases. The sensor response acquiring approach developed allows distinguishing two different gases, H2S and NH3, with a single sensing device. The results reported open new perspectives for the OFET-based gas-sensing technology and pave the way for easy detection of the other types of gases, enabling the development of complex air analysis systems based on a single sensor.

Organosilicon dimer of BTBT as a perspective semiconductor material for toxic gas detection with monolayer organic field-effect transistors

Monolayer organic field effect transistors (OFETs) based on novel BTBT dimer demonstrate excellent electrical performance and fast response to ammonia vapours.

Easily processable highly ordered Langmuir-Blodgett films of quaterthiophene disiloxane dimer for monolayer organic field-effect transistors.

Self-assembly of highly soluble water-stable tetramethyldisiloxane-based dimer of α,α'-dialkylquaterthiophene on the water-air interface was investigated by Langmuir, grazing incidence X-ray diffraction, and X-ray reflectivity techniques. The conditions for formation of very homogeneous crystalline monolayer Langmuir-Blodgett (LB) films of the oligomer were found. Monolayer organic field-effect transistors (OFETs) based on these LB films as a semiconducting layer showed hole mobilities up to 3 × 10(-3) cm(2)/(V s), on-off ratio of 10(5), small hysteresis, and high long-term stability. The electrical performance of the LB films studied is close to that for the same material in the bulk or in the monolayer OFETs prepared from water vapor sensitive chlorosilyl derivatives of quaterthiophene by self-assembling from solution. These findings show high potential of disiloxane-based LB films in monolayer OFETs for large-area organic electronics.

Oligothiophene-based monolayer field-effect transistors prepared by Langmuir-Blodgett technique

Quinquethiophene-based monolayer organic field-effect transistors (OFETs) prepared by Langmuir-Blodgett (LB) technique show hole mobilities up to 10−2 cm2/Vs and On/Off ratios up to 106. Functional logic LB monolayer devices operating in air have been demonstrated. The performance of LB OFETs is comparable to self-assembled monolayer field-effect transistors (SAMFETs) devices prepared by self-assembly from solution using the same organosilicon oligothiophene despite the LB OFET monolayer is weakly bounded to the dielectric surface. Taking into account that the LB technique is a fast and rather easy process, these findings highlight a high potential of LB technique for ultrathin organic electronics.

Retraction: Self-assembled monolayer organic field-effect transistors.

Nature 413, 713–716 (2001); correction Nature 414, 470 (2001). This manuscript was, in part, the subject of an independent investigation conducted at the behest of Bell Laboratories, Lucent Technologies. The independent committee reviewed concerns related to the validity of data associated with thedevice measurements described in the paper.

Self-assembled monolayer organic field-effect transistors.

The use of individual molecules as functional electronic devices was proposed in 1974 (ref. 1). Since then, advances in the field of nanotechnology have led to the fabrication of various molecule devices and devices based on monolayer arrays of molecules. Single molecule devices are expected to have interesting electronic properties, but devices based on an array of molecules are easier to fabricate and could potentially be more reliable. However, most of the previous work on array-based devices focused on two-terminal structures: demonstrating, for example, negative differential resistance, rectifiers, and re-configurable switching. It has also been proposed that diode switches containing only a few two-terminal molecules could be used to implement simple molecular electronic computer logic circuits. However, three-terminal devices, that is, transistors, could offer several advantages for logic operations compared to two-terminal switches, the most important of which is 'gain'-the ability to modulate the conductance. Here, we demonstrate gain for electronic transport perpendicular to a single molecular layer ( approximately 10-20 A) by using a third gate electrode. Our experiments with field-effect transistors based on self-assembled monolayers demonstrate conductance modulation of more than five orders of magnitude. In addition, inverter circuits have been prepared that show a gain as high as six. The fabrication of monolayer transistors and inverters might represent an important step towards molecular-scale electronics.