Surface morphology features of point contact gas sensors based on Cu-TCNQ compound

Abstract

The 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anion salt compound was used as the sensitive material of gas point contact sensors. The phase composition and surface morphology of the obtained sensor films were established. It was found correlation between surface morphology of the point-contact transducer and definite type of the sensor response curve observed under action of the human breath gas. If the sensor sample is formed from numerical crystals of the same or similar sizes having a uniform shape, similar to a shell, and clearly defined external borders it indicates to the creation of defect-free Yanson point contacts in the process of soft electrochemical synthesis. As a result, the surface of the sensor is a complex multistructure of a numerous number of Yanson point contacts, which generates a large output signal from the sensor in response to the action of the analyte. When crystals of Cu-TCNQ compound forming samples under investigation have lower density, large size, distorted and full of fractures boundaries, it prevents the formation of high-quality point contacts. These morphologic peculiarities are typical for samples with low level of response signal. In the case of extremely low density of Cu-TCNQ crystals observed in the sample surface the sample does not show any response to the action of the human breath gas.

Self-Powered Photodetector Fabricated from a Single-Charge-Transfer Complex Nanowire Grown In Situ between Prefabricated Electrodes on an Si3N4 Membrane

“…The TCNQ molecules only react with Cu having low ionization potential (∼7.7 eV). Here, Cu acts as a growth-nucleation layer and Au as a protecting layer . During growth, the substrate temperature was maintained at 130 °C.…”

“…Here, Cu acts as a growth-nucleation layer and Au as a protecting layer. 19 During growth, the substrate temperature was maintained at 130 °C. Growth starts from the exposed side of the Cu in the bilayer electrode and a few of the nanowires terminate on the other side on the Au layer that acts as the counter electrode.…”

“…The Cu:TCNQ is a widely explored semiconducting material in the metal-organic charge transfer complex family. − It is mostly known for its electrical resistive state switching and optoelectronic transport properties. The Cu:TCNQ in its NW form has attracted much attention because of its highly anisotropic one-dimensional fascinating structure, unique electronic and optical properties, high mobility, and potential applications in electrical and optical memory devices , like high-mobility field-effect transistors, sensors etc. Although, optical detectors fabricated from a single strand and array of Cu:TCNQ NW, , as well as array of NWs, have been reported, there are no reports on SPOD made from a single NW or arrays of Cu:TCNQ NWs with relatively high responsivity.…”

Noninvasive real-time breath test for controlling hormonal background of the human body: detection of serotonin and melatonin with quantum point-contact sensors

“…The sensing element of a TCNQ-compound point-contact sensor is a mesoscopic point-contact multistructure which consists of mechanically stable elements formed by the lateral surfaces of nanocrystals of the organic conductor [26,40,66]. The point contacts of this nanostructure are Yanson point contacts produced using the Chubov displacement technique [67], which is the most efficient and reliable method for obtaining contacts for the Yanson point-contact spectroscopy [28,68].…”

Quantum mechanisms for selective detection in complex gas mixtures with conductive sensors: analysis of the problem and new results

“…In this way it is possible to obtain a regression equation which can be used as a calibration characteristic to determine the concentration of the desired component of a complex gas mixture. This approach was developed and successfully tested by nding concentrations of such important hormones of the human body as serotonin, cortisol, and melatonin [25,52]. This allowed us to offer simple equations to determine the concentration of those hormones in real time by recording pointcontact pro les of breath.…”