Metal-oxide-semiconductor based gas sensors: screening, preparation, and integration

Abstract

Metal-oxide-semiconductor (MOS) based gas sensors have been considered a promising candidate for gas detection over the past few years. However, the sensing properties of MOS-based gas sensors also need to be further enhanced to satisfy the higher requirements for specific applications, such as medical diagnosis based on human breath, gas detection in harsh environments, etc. In these fields, excellent selectivity, low power consumption, a fast response/recovery rate, low humidity dependence and a low limit of detection concentration should be fulfilled simultaneously, which pose great challenges to the MOS-based gas sensors. Recently, in order to improve the sensing performances of MOS-based gas sensors, more and more researchers have carried out extensive research from theory to practice. For a similar purpose, on the basis of the whole fabrication process of gas sensors, this review gives a presentation of the important role of screening and the recent developments in high throughput screening. Subsequently, together with the sensing mechanism, the factors influencing the sensing properties of MOSs involved in material preparation processes were also discussed in detail. It was concluded that the sensing properties of MOSs not only depend on the morphological structure (particle size, morphology, pore size, etc.), but also rely on the defect structure and heterointerface structure (grain boundaries, heterointerfaces, defect concentrations, etc.). Therefore, the material-sensor integration was also introduced to maintain the structural stability in the sensor fabrication process, ensuring the sensing stability of MOS-based gas sensors. Finally, the perspectives of the MOS-based gas sensors in the aspects of fundamental research and the improvements in the sensing properties are pointed out.

Structural, Topography, and Optical Properties of Ba‐Doped Mn3O4 Thin Films for Ammonia Gas Sensing Application

“…Nowadays, nanocrystalline metal oxide semiconductor thin film (MOSTF) gas sensors have attracted interests due to its notable characteristic physical and chemical properties; furthermore, metal oxide semiconductor (MOS) gas sensors are extensively investigated based on different sensing materials, for example, SnO 2 , WO 3 , ZnO, In 2 O 3 , TiO 2 , NiO, CuO, and Co 3 O 4 . [1][2][3] These sensors are classified into two categories, namely, n-type and p-type semiconductors, commonly the conductivity of n-type (MOS) gas sensor increases toward reducing gases such as NH 3 , CO, H 2 , H 2 S, CH 4 , etc. and decreases in p-type (MOS) gas sensor, whereas toward oxidizing gases (Cl 2 , O 2 , O 3 , NO x , CO 2 , SO 2 , etc.)…”

“…the effect is vice versa. [4,5] Various metal oxide materials were used to sense efficiently ammonia [1,4,5] as well as organic materials. [6] N-type (MOS) gas sensors have been widely investigated in the last decades while p-type (MOS) gas sensors have attained less attention.…”

Metal oxide semiconductor-based Schottky diodes: a review of recent advances

“…The core of these devices are the physical characteristics of the semiconductor material; including its integration of electronic and optical properties which allows interaction and regulation of the photon, electrons, and holes using different electronic infrastructure and operating environments. Most studies confirm the metal-semiconductor (MS) as a prime component of the modern electronic components [2][3][4]. Initially, the metal-semiconductor solid-state device was discovered in 1874 and referred as whisker contact rectifier, which included a wire tip pressed onto a lead sulfide crystal.…”

Controlled Carbon Doping in Anatase TiO2 (101) Facets: Superior Trace‐Level Ethanol Gas Sensor Performance and Adsorption Kinetics

“…[17][18][19][20] But most of these cases, metal oxide sensors have to be operated at high temperature or under UV irradiation conditions because of their large bandgap. [26][27][28][29][30] In general, carbon has inherent advantages, such as stability, low cost, sustainable, and ecofriendly preparation. [21][22][23][24][25] Many studies have demonstrated that metal and nonmetal doping in TiO 2 hinders the recombination rate of charge carriers by creating or modifying the bandgap with introduction of several sub-bandgap energy levels.…”

“…Recently, nonmetal doping has attracted wider attention rather than the transition metal doping owing to their increased thermal stability, enhanced selectivity, sensitivity, and drastic reduction in working temperature by simple modifications of additional impurity levels in the bandgap of TiO 2 . [26][27][28][29][30] In general, carbon has inherent advantages, such as stability, low cost, sustainable, and ecofriendly preparation. Carbon doping can lower the bandgap and create oxygen vacancies, leading to enhanced intrinsic conductivity.…”