High-Resolution p-Type Metal Oxide Semiconductor Nanowire Array as an Ultrasensitive Sensor for Volatile Organic Compounds

Abstract

The development of high-performance volatile organic compound (VOC) sensor based on a p-type metal oxide semiconductor (MOS) is one of the important topics in gas sensor research because of its unique sensing characteristics, namely, rapid recovery kinetics, low temperature dependence, high humidity or thermal stability, and high potential for p-n junction applications. Despite intensive efforts made in this area, the applications of such sensors are hindered because of drawbacks related to the low sensitivity and slow response or long recovery time of p-type MOSs. In this study, the VOC sensing performance of a p-type MOS was significantly enhanced by forming a patterned p-type polycrystalline MOS with an ultrathin, high-aspect-ratio (∼25) structure (∼14 nm thickness) composed of ultrasmall grains (∼5 nm size). A high-resolution polycrystalline p-type MOS nanowire array with a grain size of ∼5 nm was fabricated by secondary sputtering via Ar(+) bombardment. Various p-type nanowire arrays of CuO, NiO, and Cr2O3 were easily fabricated by simply changing the sputtering material. The VOC sensor thus fabricated exhibited higher sensitivity (ΔR/Ra = 30 at 1 ppm hexane using NiO channels), as well as faster response or shorter recovery time (∼30 s) than that of previously reported p-type MOS sensors. This result is attributed to the high resolution and small grain size of p-type MOSs, which lead to overlap of fully charged zones; as a result, electrical properties are predominantly determined by surface states. Our new approach may be used as a route for producing high-resolution MOSs with particle sizes of ∼5 nm within a highly ordered, tall nanowire array structure.

The Electrostatically Formed Nanowire: A Novel Platform for Gas-Sensing Applications

“…The MOS measures the change in the electrical resistance of the device upon an interaction with the target analyte. Recently, Cho et al demonstrated a patterned p-type polycrystalline MOS nanowire array with an improved sensitivity and response time toward various volatile organic compounds (VOCs) [23], and Katwal et al fabricated a novel zinc oxide nanowire–nanotube hybrid-based sensor with a good response to specific VOCs that serve as markers for breast cancer [24]. Similarly, various other studies demonstrated the outstanding sensing potential of MOS technology for VOC detection [25,26,27].…”

Highly Sensitive Sensors Based on Metal-Oxide Nanocolumns for Fire Detection

“…They are induced from the adsorption and desorption of the gases when specific gases interact with its surface, which is affected by three basic factors, namely the transducer function, utility factor, and receptor function [17,18,19]. For these reasons, various chemoresistive gas sensors with large surface-area-to-volume ratios such as nanotubes [20,21,22], nanobamboos [23], nanowalls [24], nanospheres [25,26], and nanocolumns [27] have been studied based on the three basic factors to enhance the gas-sensing properties. Further, it is well known that highly ordered one-dimensional nanostructures, which show extremely large surface-to-volume ratios, are the most promising material platform for a good gas-sensing performance due to the excellent accessibility of target gases and aggregation-free geometry [19].…”

Discrimination of 1‐ and 2‐Propanol by Using the Transient Current Change of a Semiconducting ZnFe2O4 Chemiresistor

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A semiconducting metal oxide (SMO) chemiresistor (ZnFe 2 O 4 ) is used for discriminating two isomeric volatile organic compounds (VOCs), namely 1-and 2-propanol. [7][8][9][10] Unlike physisorption based charge transfer sensors, semiconducting metal oxide (SMO) based chemiresistors are mostly operative at high temperature and their resistance/conductance changes in exposure to reducing gases or vapors. The changes in transient current of the ZnFe 2 O 4 chemiresistor are measured at different temperatures (260-320°C) for detecting equal concentrations (200 ppm) of the two structural isomers of propanol.

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“…The changes in transient current of the ZnFe 2 O 4 chemiresistor are measured at different temperatures (260-320°C) for detecting equal concentrations (200 ppm) of the two structural isomers of propanol. [4][5][6][7][8][9]15] In the present work, we have studied the response of ZnFe 2 O 4 based SMO chemiresistor towards equal concentrations (200 ppm) of two isomeric VOCs namely 1-propanol and 2-propanol at four different operating temperatures (i. e. 260, 280, 300 and 320°C). First-principles calculations and kinetic studies on the interaction of 1-and 2propanol over ZnFe 2 O 4 provide further insight in support of the experimental evidence.…”

“…catalyzed aerobic oxidations of organic molecules are attractive as a cost-effective and greener route for the synthesis of fine chemicals as compared to the traditional liquid phase reactions. [4][5][6][7][8][9]15] In the present work, we have studied the response of ZnFe 2 O 4 based SMO chemiresistor towards equal concentrations (200 ppm) of two isomeric VOCs namely 1-propanol and 2-propanol at four different operating temperatures (i. e. 260, 280, 300 and 320°C). [7][8][9][10] Unlike physisorption based charge transfer sensors, semiconducting metal oxide (SMO) based chemiresistors are mostly operative at high temperature and their resistance/conductance changes in exposure to reducing gases or vapors.…”