The Preparation of Titanium Dioxide Gas Sensors by the Electric Field Assisted Aerosol CVD Reaction of Titanium Isopropoxide in Toluene

Abstract

Thin films of titanium dioxide are deposited on gas-sensor substrates at 450 8C from the aerosol-assisted (AA)CVD of titanium isopropoxide solutions in toluene under the influence of electric fields. Electric fields are generated by applying a potential difference between the inter-digitated electrodes of the gas-sensor substrate during the deposition. The deposited films are analyzed and characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). It is found that an increase in electric field strength during deposition causes changes in the film microstructure, preferential orientation, and growth rate. The gas-sensor properties of the films are also examined. It is found that applying an electric field during the deposition improves the film microstructure and leads to a two-fold enhancement in the sensing properties of the film.

Aerosol-assisted chemical vapor deposition of metal oxide thin films for photoelectrochemical water splitting

“…In addition, Panjawi et al reported the fabrication of TiO 2 thin films on gas-sensor substrates at 450 C via the AACVD of titanium isopropoxide solutions in toluene [94]. As shown in Fig.…”

Electric field assisted aerosol assisted chemical vapour deposition of nanostructured metal oxide thin films

“…Indeed it is well known that sensor microstructure plays an important role in determining the gas response of a gas sensing material [24]. We have suggested previously that a variety of phenomena may be occurring when an electric field is applied to CVD growth [10][11][12][13]. Applied electric fields can cause an increase in growth rate and nucleation rate leading to pseudo dendritic type morphologies as a result of accelerating gas phase species towards the surface [10].…”

“…In these cases, we feel this is unlikely to occur as a result of a gas phase effect given that the tungsten hexaphenoxide and titanium tetraisopropoxide precursors are electrically symmetrical. The changes in surface feature scale length hints at a surface effect where growth is directed through a localised electric field rather than as a result of solely gas phase effects [13].…”

“…Previous investigations [10][11][12][13] have shown that the application of an electric field during a CVD reaction influences the crystallographic orientation, microstructure and subsequent properties of the deposited materials. Indeed it is well known that sensor microstructure plays an important role in determining the gas response of a gas sensing material [24].…”

“…The effect of an electric field in chemical vapour deposition reactions of any kind is largely unknown; Williams et al noted that whilst trying to follow WO 3 film growth from an aerosol assisted chemical vapour deposition (AACVD) using impedance measurements, the bias of the measuring circuit led to a change in film microstructure [9]. We have conducted a number of studies on the effect of electric fields in the chemical vapour deposition reactions to produce various metal oxides [10][11][12][13]. In this paper we describe the use of electric field assisted chemical vapour deposition to produce thin films of vanadium, titanium and tungsten oxides and their application as metal oxide gas sensors.…”