Abstract
This work reports synthesis, thin film characterizations, and study of an organic semiconductor 2-aminoanthraquinone (AAq) for humidity and temperature sensing applications. The morphological and phase studies of AAq thin films are carried out by scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD) analysis. To study the sensing properties of AAq, a surface type Au/AAq/Au sensor is fabricated by thermally depositing a 60 nm layer of AAq at a pressure of ~10−5 mbar on a pre-patterned gold (Au) electrodes with inter-electrode gap of 45 µm. To measure sensing capability of the Au/AAq/Au device, the variations in its capacitance and resistance are studied as a function of humidity and temperature. The Au/AAq/Au device measures and exhibits a linear change in capacitance and resistance when relative humidity (%RH) and temperature are varied. The AAq is a hydrophobic material which makes it one of the best candidates to be used as an active material in humidity sensors; on the other hand, its high melting point (575 K) is another appealing property that enables it for its potential applications in temperature sensors.
Highlights
Organic semiconductors are revolutionizing the way we manufacture and engage with electronic devices as they enable the fabrication of light-weight, flexible electronic devices with novel form factors [1,2,3]
The dielectric constant of the organic semiconducting sensing layer, more water vapor will be absorbed which will cause to increase capacitance of the materials lies in the range of 4–8 [39] whereas dielectric constant of water is 80.4 [36,37]
The temperature sensing mechanism for an AAq-based sensor can be explained from the effect of temperature on conductivity and mobility of AAq thin film
Summary
Organic semiconductors are revolutionizing the way we manufacture and engage with electronic devices as they enable the fabrication of light-weight, flexible electronic devices with novel form factors [1,2,3]. Low molecular weight organic semiconductors-based capacitive and resistive surface type sensors are of great interest due to their low cost and simple fabrication methods. Organic semiconductors are the alternate materials which are low cost, mostly solution processable, mechanically flexible, light-weight, comparatively low-temperature processed and require simple fabrication techniques for device formation [20]. Surface type sensors are easy to fabricate, are lower cost alternatives and offer simple technology for exploring different properties of organic semiconductors, such as the effect of humidity [29], the effect of temperature [31] and light sensitivity [11]. We fabricate surface type humidity and temperature sensors of the form (Au/AAq/Au) using 2-aminoanthraquinone (AAq) as the organic semiconductor for the first time due to its hydrophobic nature. As the sensitivity of the sensor is frequency dependent, this device was characterized at both 120 Hz and 1 kHz
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