A Highly Selective and Self-Powered Gas Sensor Via Organic Surface Functionalization of p-Si/n-ZnO Diodes (original) (raw)

Novel Approaches Towards Highly Selective Self-Powered Gas Sensors

Procedia Engineering, 2015

The prevailing design approaches of semiconductor gas sensors struggle to overcome most of their current limitations such as poor selectivity, and high power consumption. Herein, a new sensing concept based on devices that are capable of detecting gases without the need of any external power sources required to activate interaction of gases with sensor or to generate the sensor read out signal. Based on the integration of complementary functionalities (namely; powering and sensing) in a singular nanostructure, self-sustained gas sensors will be demonstrated. Moreover, a rational methodology to design organic surface functionalization that provide high selectivity towards single gas species will also be discussed. Specifically, theoretical results, confirmed experimentally, indicate that precisely tuning of the sterical and electronic structure of sensor material/organic interfaces can lead to unprecedented selectivity values, comparable to those typical of bioselective processes. Finally, an integrated gas sensor that combine both the self-powering and selective detection strategies in one single device will also be presented.

New approaches for improving semiconductor gas sensors

Sensors and Actuators B: Chemical, 1991

It is demonstrated that the sensing characteristics of a semiconductor gas sensor using SnO, can be improved by controlling fundamental factors which affect its receptor and transducer functions. The transducer function is deeply related with the microstructure of the elements, i.e., the grain size of SnO, (D) and the depth of the surface space-charge layer (15). The sensitivity is drastically promoted when D is made comparable to or less than 2L, either by control of D for pure SnO, elements or by control of the Debye length for impurity-doped elements. On the other hand, the receptor function is drastically modified by the introduction of foreign receptors on the surface of SnO,. In the particular cases of Pd and Ag promoters, the oxides (PdO and Ag,O) formed in air interact with the SnO, surface to produce an electron-deficient space-charge layer, and this contributes much to promoting the gas sensitivity. For a test gas having a specific reactivity, such specificity can be utilized for exploiting gas-selective receptors, as exemplified by CuO-SnO, and La,O,-SnO, elements, which detect H,S and ethanol gas respectively very sensitively.

Highly sensitive and selective gas sensors using p-type oxide semiconductors: Overview

2014

Ag-and Pd-loaded SnO 2 nanowire network sensors were prepared by the growth of SnO 2 nanowires via thermal evaporation, the coating of slurry containing SnO 2 nanowires, and dropping of a droplet containing Ag or Pd nanoparticles, and subsequent heat treatment. All the pristine, Pd-loaded and Ag-loaded SnO 2 nanowire networks showed the selective detection of C 2 H 5 OH with low cross-responses to CO, H 2 , C 3 H 8 , and NH 3 . However, the relative gas responses and gas selectivity depended closely on the catalyst loading. The loading of Pd enhanced the responses(R a /R g : R a : resistance in air, R g : resistance in gas) to CO and H 2 significantly, while it slightly deteriorated the response to C 2 H 5 OH. In contrast, a 3.1-fold enhancement was observed in the response to 100 ppm C 2 H 5 OH by loading of Ag onto SnO 2 nanowire networks. The role of Ag catalysts in the highly sensitive and selective detection of C 2 H 5 OH is discussed.

Shape-controlled ZnO Nanostructures for Gas Sensing Applications

Procedia Engineering, 2014

In order to increase the sensitivity and selectivity of semiconducting gas sensors, we have integrated three different ZnO nanostructures as sensitive layers on silicon chips: cloudy-like nanoparticles, isotropic nanoparticles and nanorods. We have compared their response towards three gases, namely CO, C3H8, and NH3. The morphology of ZnO nanostructures significantly influences the sensors responses to the reducing gases. These results demonstrate that sensor performance can be improved using the same sensitive material and by modifying only its shape this opens the way to new arrays of selective gas sensors.

A Novel Type Room Temperature Surface Photovoltage Gas Sensor Device 

In this paper a novel type of a highly sensitive gas sensor device based on the surface photovoltage effect is described. The developed surface photovoltage gas sensor is based on a reverse Kelvin probe approach. As the active gas sensing electrode the porous ZnO nanostructured thin films are used deposited by the direct current (DC) reactive magnetron sputtering method exhibiting the nanocoral surface morphology combined with an evident surface nonstoichiometry related to the unintentional surface carbon and water vapor contaminations. Among others, the demonstrated SPV gas sensor device exhibits a high sensitivity of 1 ppm to NO2 with a signal to noise ratio of about 50 and a fast response time of several seconds under the room temperature conditions.

Voltage-controlled NiO/ZnO p–n heterojunction diode: a new approach towards selective VOC sensing

Microsystems & Nanoengineering

Metal oxide resistive gas sensors suffer from poor selectivity that restricts their practical applicability. Conventional sensor arrays are used to improve selectivity which increased the system complexity. Here, we have proposed a novel NiO/ZnO-based p–n junction single-diode device for selective sensing of several volatile organic compounds (VOCs) simultaneously by tuning bias voltage. The operating voltage was varied between 3 and 5 volts to achieve selective sensing of 2-propanol (19.1 times for 95 ppm with response and recovery times of 70 s and 55 s respectively‚ at 3 volts), toluene (20.1 times for 95 ppm with response and recovery times of 100 s and 60 s respectively, at 4 volts), and formaldehyde (11.2 times for 95 ppm with response and recovery times of 88 s and 54 s respectively, at 5 volts). A probable mechanism of the tunable selectivity with operating bias voltage due to increase in surface carriers with increasing voltage was hence put forth. Thus, this device may pla...

Organic Thin-Film Transistors as Gas Sensors: A Review

Materials, 2020

Organic thin-film transistors (OTFTs) are miniaturized devices based upon the electronic responses of organic semiconductors. In comparison to their conventional inorganic counterparts, organic semiconductors are cheaper, can undergo reversible doping processes and may have electronic properties chiefly modulated by molecular engineering approaches. More recently, OTFTs have been designed as gas sensor devices, displaying remarkable performance for the detection of important target analytes, such as ammonia, nitrogen dioxide, hydrogen sulfide and volatile organic compounds (VOCs). The present manuscript provides a comprehensive review on the working principle of OTFTs for gas sensing, with concise descriptions of devices’ architectures and parameter extraction based upon a constant charge carrier mobility model. Then, it moves on with methods of device fabrication and physicochemical descriptions of the main organic semiconductors recently applied to gas sensors (i.e., since 2015 bu...

Investigation of gas–surface interactions at self-assembled silicon surfaces acting as gas sensors

Applied Surface Science, 2003

This paper reports the results of an investigation aimed at using self-assembled monolayers to modify the supramolecular interactions between Si surfaces and gaseous molecules. The specific goal is that of employing molecularly imprinted silicon surfaces to develop a new class of chemical sensors capable to detect species with enhanced selectivity. Single-crystal p-type (0 0 1) silicon has been modified by grafting organic molecules onto its surface by using wet chemistry synthetic methods. Silicon has been activated toward nucleophilic attack by brominating its surface using a modified version of the purple etch, and aromatic fragments have been bonded through the formation of direct Si-C bonds onto it using Grignard reagents or lithium aryl species. Formation of self-assembled monolayers (SAMs) was verified by using vibrational spectroscopy. Porous metal-SAM-Si diodes have been successfully tested as resistive chemical sensors toward NO x , SO x , CO, NH 3 and methane. Current-voltage characteristics measured at different gas compositions showed that the mechanism of surface electron density modulation involves a modification of the junction barrier height upon gas adsorption. Quantum-mechanical simulations of the interaction mechanism were carried out using different computational methods to support such an interaction mechanism. The results obtained appear to open up new relevant applications of the SAM techniques in the area of gas sensing. #