MOCVD growth and characterization of TiO₂ thin films for hydrogen gas sensor application

Advanced development of metal oxide nanomaterials for H2gas sensing applications

“…As shown in Figure 2, when the sensor is placed in the air environment, a number of oxygen molecules are adsorbed on the surface of the material, and form different oxygen anion (O 2 -, O -, O 2-) as well as a space charge depletion layer, which reduce the electrons in the conduction band of the metal 11 oxide nanomaterials, and increase the resistance. 43 When H 2 is introduced into the chamber, it reacts with the oxygen anion and produces H 2 O, resulting in the charge transfer process from the adsorbed oxygen species back to the conduction band of the MOx nanomaterials, and the space charge depletion layer on the surface of the material is reduced, thus the resistance of the sensor is reduced. 127 For p-type semiconductors, the direction of charge transfer is opposite to that of n-type semiconductors, but the basic sensing mechanism is almost similar.…”

“…Pradeep et al 155 43 In addition, the thermal evaporation method is to vaporize precursors in noble gases (or reactive gases) and then form a thin film by collision, cooling, and condensation process. According to the precursors used in the preparation process, the thermal evaporation method can be generally divided into direct evaporation of MOx powder, pure metal powder thermal evaporation, and decomposition of MOx etc.…”

“…[33][34][35][36][37][38] A series of MOx nanomaterials with different morphologies and structures were prepared by a variety of methods for the rapid and efficient detection of H 2 . [39][40][41][42][43] With the development of nanotechnology, the response is much improved. 44 However, the low selectivity, poor stability, and weak durability of the H 2 gas sensors still impede practical applications.…”

Titanium Dioxide Nanoparticles

“…In the preparation of both thick and fine particle size, TiO 2 nanoparticles by chemical vapor deposition and titanium tetraisopropoxide are used as the precursor in an oxygen-containing atmosphere [30]. More recently, modified CVD forms such as plasma-enhanced chemical vapor deposition (PECVD), metal-organic chemical vapor deposition (MOCVD), and low-pressure chemical vapor deposition (LPCVD) have been used in the synthesis of TiO 2 nanoparticles [31][32][33].…”

The effect of graphene nanoplatelets on technical properties of micro- and nano-sized TiO2 matrix: a comparative research study on electrical and optical characteristics

“…Many different methods have been developed for graphene synthesis such as mechanical decomposition, hummers' method, chemical vapor deposition, electrochemical synthesis, and liquid-phase exfoliation [3][4][5][6][7]. In addition to studies of scientists, graphene is used in many devices facilitating our daily life such as gas sensors [8], transistors, batteries [9], and supercapacitors [10].…”