CNTFET Gas Sensors Using SWCNT Mats: Method for Low-cost Fabrication, Solution to Improve Selectivity, Experimental Results using Interfering Agents

AbstractThe first paper showing the great potentiality of Carbon Nanotubes Field Effect transistors (CNTFETs) for gas sensing applications was published in 2000 [1]. It has been demonstrated that the performances of this kind of sensors are extremely interesting : a sensitivity of around 100ppt (e.g. for NO2 [2]) has been achieved in 2003 and several techniques to improve selectivity have been tested with very promising results [2]. The main issues that have not allowed, up to now, these devices to strike more largely the market of sensors, have been the lack of an industrial method to obtain low-cost devices, a demonstration of their selectivity in relevant environments and finally a deeper study on the effect of humidity and the possible solutions to reduce it. This contribution deals with CNTFETs based sensors fabricated using air-brush technique deposition on large surfaces. Compared to our last contribution [3], we have optimized the air-brush technique in order to obtain high performances transistors (Log(Ion)/ Log(Ioff) ~ 5/6) with highly reproducible characteristics : this is a key point for the industrial exploitation. We have developed a machine which allows us the dynamic deposition on heated substrates of the SWCNT solutions, improving dramatically the uniformity of the SWCNT mats. We have performed tests using different solvents that could be adapted as a function of the substrates (e.g. flexible substrates). Moreover these transistors have been achieved using different metal electrodes (patented approach [4]) in order to improve selectivity. Results of tests using NO2, NH3 with concentrations between ~ 1ppm and 10ppm will be shown during the meeting.

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New Dynamic Air-Brush Technique for SWCNTs Deposition: Application to Fabrication of CNTFETs for Electronics and Gas Sensing

MRS Proceedings ◽

10.1557/opl.2011.800 ◽

2011 ◽

Vol 1283 ◽

Cited By ~ 1

Author(s):

P. Bondavalli ◽

L. Gorintin ◽

P. Legagneux ◽

J.P. Simonato ◽

L. Cailler

Keyword(s):

Carbon Nanotubes ◽

Response Time ◽

Gas Sensors ◽

Field Effect ◽

Gas Sensing ◽

Field Effect Transistors ◽

Specific Interaction ◽

Flexible Substrates ◽

Percolation Effect

ABSTRACTThis contribution deals with Carbon Nanotubes Field Effect transistors (CNTFETs) based gas sensors fabricated using a completely new dynamic spray based technique (patented) for SWCNTs deposition. The extreme novelty is that our technique is compatible with large surfaces, flexible substrates and allows to fabricate high performances transistors exploiting the percolation effect of the SWCNTs networks achieved with extremely reproducible characteristics. Recently, we have been able to achieve extremely selective measurement of NO2, NH3 and CO using four CNTFETS fabricated using different metals as electrodes, exploiting the specific interaction between gas and metal/SWCNT junctions. In this way we have identify an electronic fingerprinting of the gas detected. The response time is evaluated at less than 30sec.

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A Review of Carbon Nanotubes-Based Gas Sensors

Journal of Sensors ◽

10.1155/2009/493904 ◽

2009 ◽

Vol 2009 ◽

pp. 1-24 ◽

Cited By ~ 255

Author(s):

Yun Wang ◽

John T. W. Yeow

Keyword(s):

Carbon Nanotubes ◽

Gas Sensors ◽

Gas Sensing ◽

Low Cost ◽

High Surface ◽

Hollow Structure ◽

Volume Ratio ◽

Fast Response ◽

Sensing Technology ◽

Structure Of Nanomaterials

Gas sensors have attracted intensive research interest due to the demand of sensitive, fast response, and stable sensors for industry, environmental monitoring, biomedicine, and so forth. The development of nanotechnology has created huge potential to build highly sensitive, low cost, portable sensors with low power consumption. The extremely high surface-to-volume ratio and hollow structure of nanomaterials is ideal for the adsorption of gas molecules. Particularly, the advent of carbon nanotubes (CNTs) has fuelled the inventions of gas sensors that exploit CNTs' unique geometry, morphology, and material properties. Upon exposure to certain gases, the changes in CNTs' properties can be detected by various methods. Therefore, CNTs-based gas sensors and their mechanisms have been widely studied recently. In this paper, a broad but yet in-depth survey of current CNTs-based gas sensing technology is presented. Both experimental works and theoretical simulations are reviewed. The design, fabrication, and the sensing mechanisms of the CNTs-based gas sensors are discussed. The challenges and perspectives of the research are also addressed in this review.

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Improved ambipolar charge injection in organic field-effect transistors with low cost metal electrode using polymer sorted semiconducting carbon nanotubes

Organic Electronics ◽

10.1016/j.orgel.2017.04.004 ◽

2017 ◽

Vol 46 ◽

pp. 28-34 ◽

Cited By ~ 10

Author(s):

Seung-Hoon Lee ◽

Dong-Yu Kim ◽

Yong-Young Noh

Keyword(s):

Carbon Nanotubes ◽

Field Effect ◽

Field Effect Transistors ◽

Low Cost ◽

Charge Injection ◽

Metal Electrode ◽

Organic Field Effect Transistors

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Design Printable Pressure Sensor Based on 3DP Fabrication

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.915-916.1135 ◽

2014 ◽

Vol 915-916 ◽

pp. 1135-1139

Author(s):

Na Li ◽

Ji Quan Yang ◽

Hou Yuan Zhou

Keyword(s):

Pressure Sensor ◽

Inkjet Printing ◽

Field Effect ◽

Field Effect Transistors ◽

Low Cost ◽

Power Level ◽

Dynamic Performance ◽

Flexible Substrates ◽

Experimental Measurements ◽

Pressure Sensitivity

In this paper, a low cost, printable pressure sensor is presented. The pressure sensor will be used in personal navigation system which was designed based on micro jet fabrication structure. Inkjet printing and line patterning methods have been used to fabricate polymer resistors and field effect transistors on flexible substrates. A prototype sensor was designed, and the models of mechnical structure and ditital fabrication was also given, fabricated and tested with standard experimental measurements. Results verify that the pressure sensitivity can be measured for both requency and minimum power level difference in good perforamance. The dynamic performance of pressure sensor was also tested by inkjet printing on to flexible substrates including paper, with high resolution in just seconds.

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Laterally Grown ZnO Nanowires for Sensing Applications

10.26686/wgtn.17067938.v1 ◽

2021 ◽

Author(s):

◽

Campbell Matthews

Keyword(s):

Field Dependence ◽

Gas Sensors ◽

Seed Layer ◽

Field Effect ◽

Field Effect Transistors ◽

Pressure Sensors ◽

Zno Nanowires ◽

Hydrothermal Growth ◽

Maximum Deviation ◽

Sensing Applications

<p>Zinc oxide nanowires are a semiconducting material that has many uses in electronic applications. In particular, ZnO nanowires have been used in field effect transistors and applied as sensors for the detection of gases, biomolecules, UV light and as pressure sensors. ZnO nanowires can be fabricated using many different methods, but most require the use of high tempertures and have extensive setup costs. Hydrothermal growth, however, provides a cheap and low temperture method for growing ZnO nanowires. Much work has been done on the synthesis and charcetristaion of ZnO nanowires grown using hydrothermal growth, in partiuclar for photovoltaic applications. Little work has been done on the performace of hydrothermally grown ZnO nanowires in field effect transtors. This thesis looks at applying hydrothermally grown ZnO nanowires as field effect transistors (FET). The FETs are characterised and developed with the intention of using them in senseing applications. The nanowire FET structure is optimised for sensing by developing a method that constrains the nanowires to exclusively lateral growth. A Ti capping layer is fabricated on top of a ZnO seed layer. The ZnO seed layer is then etched with dilute acid so that the Ti layer overhangs the ZnO. This acts as a physical barrier to vertical wire growth from the ZnO seed layer. The maximum deviation of the nanowires from the horizontal can be controlled by etching for different times. Two device types are fabricated using different size nanowires. One uses large nanowires, or nanorods (diameter 400 nm), while the second device type uses a hybrid structure of large nanorods with much thinner nanowires (diameter 20 nm) growing off them. Both device types are characterised as FETs in dry conditions and also when immersed in a number of different liquids. Two different gating setups are also used with the Si/SiO₂ substrate used as a backgate and a Ag/AgCl electrode inserted into liquid as a topgate. The large nanorods only show field dependence when wet due to the large capacitance of the elctric double layer and enhanced band bending. The wet nanorods can achieve on/off ratios of 10³. In contrast, the thinner nanowires show field dependence both when dry and when wet. On/off ratios of more than 10⁴ are achieved. In general the nanowires have superior on off ratios and smaller off current due to their larger surface to volume ratio. Attempts are made to functionalise the nanowires with aptamers so that they can be used as a biosensor. The functionalisation procedure is documented, however the overall procedure proves to be unsuccessful due to the instability and dissolution of the nanowires in tris buffer. The rate of decay in buffer solution is investigated. Both device types are also tested as gas sensors for humidity and ethanol detection. The nanorods show no apparent detection, while the nanowires show some response to ethanol. Further development of the experimental setup is necessary to better characterise the devices. Finally future work on these nanowires is discussed and possible improvements proposed for future development as biosensors and gas sensors.</p>

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Laterally Grown ZnO Nanowires for Sensing Applications

10.26686/wgtn.17067938 ◽

2021 ◽

Author(s):

◽

Campbell Matthews

Keyword(s):

Field Dependence ◽

Gas Sensors ◽

Seed Layer ◽

Field Effect ◽

Field Effect Transistors ◽

Pressure Sensors ◽

Zno Nanowires ◽

Hydrothermal Growth ◽

Maximum Deviation ◽

Sensing Applications

<p>Zinc oxide nanowires are a semiconducting material that has many uses in electronic applications. In particular, ZnO nanowires have been used in field effect transistors and applied as sensors for the detection of gases, biomolecules, UV light and as pressure sensors. ZnO nanowires can be fabricated using many different methods, but most require the use of high tempertures and have extensive setup costs. Hydrothermal growth, however, provides a cheap and low temperture method for growing ZnO nanowires. Much work has been done on the synthesis and charcetristaion of ZnO nanowires grown using hydrothermal growth, in partiuclar for photovoltaic applications. Little work has been done on the performace of hydrothermally grown ZnO nanowires in field effect transtors. This thesis looks at applying hydrothermally grown ZnO nanowires as field effect transistors (FET). The FETs are characterised and developed with the intention of using them in senseing applications. The nanowire FET structure is optimised for sensing by developing a method that constrains the nanowires to exclusively lateral growth. A Ti capping layer is fabricated on top of a ZnO seed layer. The ZnO seed layer is then etched with dilute acid so that the Ti layer overhangs the ZnO. This acts as a physical barrier to vertical wire growth from the ZnO seed layer. The maximum deviation of the nanowires from the horizontal can be controlled by etching for different times. Two device types are fabricated using different size nanowires. One uses large nanowires, or nanorods (diameter 400 nm), while the second device type uses a hybrid structure of large nanorods with much thinner nanowires (diameter 20 nm) growing off them. Both device types are characterised as FETs in dry conditions and also when immersed in a number of different liquids. Two different gating setups are also used with the Si/SiO₂ substrate used as a backgate and a Ag/AgCl electrode inserted into liquid as a topgate. The large nanorods only show field dependence when wet due to the large capacitance of the elctric double layer and enhanced band bending. The wet nanorods can achieve on/off ratios of 10³. In contrast, the thinner nanowires show field dependence both when dry and when wet. On/off ratios of more than 10⁴ are achieved. In general the nanowires have superior on off ratios and smaller off current due to their larger surface to volume ratio. Attempts are made to functionalise the nanowires with aptamers so that they can be used as a biosensor. The functionalisation procedure is documented, however the overall procedure proves to be unsuccessful due to the instability and dissolution of the nanowires in tris buffer. The rate of decay in buffer solution is investigated. Both device types are also tested as gas sensors for humidity and ethanol detection. The nanorods show no apparent detection, while the nanowires show some response to ethanol. Further development of the experimental setup is necessary to better characterise the devices. Finally future work on these nanowires is discussed and possible improvements proposed for future development as biosensors and gas sensors.</p>

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Thiazolothiazole‐Based Quinoidal Compounds for High‐Performance n‐Channel Organic Field‐Effect Transistors with Low‐Cost Metal Electrodes

Advanced Electronic Materials ◽

10.1002/aelm.201901443 ◽

2020 ◽

Vol 6 (6) ◽

pp. 1901443

Author(s):

Yan Feng ◽

Xiaolan Qiao ◽

Guangcheng Ouyang ◽

Guohua Liu ◽

Hongxiang Li

Keyword(s):

Field Effect ◽

High Performance ◽

Field Effect Transistors ◽

Low Cost ◽

Organic Field Effect Transistors ◽

Metal Electrodes

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Electrical transduction in phthalocyanine-based gas sensors: from classical chemiresistors to new functional structures

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s108842460900019x ◽

2009 ◽

Vol 13 (01) ◽

pp. 84-91 ◽

Cited By ~ 30

Author(s):

Marcel Bouvet ◽

Vicente Parra ◽

Clémentine Locatelli ◽

Hui Xiong

Keyword(s):

Present Article ◽

Gas Sensor ◽

Gas Sensors ◽

Field Effect ◽

Gas Sensing ◽

Field Effect Transistors ◽

Real Gas ◽

Sensor Applications

Phthalocyanines are organic-based materials which have attracted a lot of research in recent times. In the field of sensors, they present interesting and valuable potentialities as sensing elements for real gas sensor applications. In the present article, and taking some of our experiments as representative examples, we review the different ways of transduction applied to such applications. Some of the new tendencies and transducers for gas sensing based on phthalocyanine derivatives are also reported. Among them, electrical transduction (resistors, field-effect transistors, diodes, etc.) has been, historically, the most commonly exploited way for the detection and/or quantification of gas pollutants, vapors and aromas, according to the conducting behavior of phthalocyanines. We will focus precisely on these systems.

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