The influence of Al doping on the electrical, optical and structural properties of SnO₂transparent conducting films deposited by the spray pyrolysis technique

Abstract

In this study, the influence of increasing the Al concentration on the electrical, optical and structural properties of spray-pyrolysis-deposited SnO 2 films has been investigated. The SnO 2 : Al films were deposited at a substrate temperature of 480˚C using a hydro-alcoholic solution consisting of tin and aluminium chlorides with various Al-doping levels from 0 to 30 wt% in solution. The [Al]/[Sn] atomic ratios were from 0 to 12.1 in films. The results of x-ray diffraction have shown that the deposited films are polycrystalline without any second phases with preferential orientations along the (110), ( 211) and (301) planes and an average grain size of 28.7 nm. Also, the Hall effect and resistivity measurements of the films show that for a specific acceptor dopant (Al) concentration (8.0 at% in film), majority carriers convert from electrons to holes and p-conductivity dominates. The optical absorption edge for undoped SnO 2 films lies at 4.105 eV, whereas for high acceptor-doped films it shifts towards lower energies (longer wavelengths) in the range of 4.105-3.604 eV.

Investigating the influence of Al-doping and background humidity on NO<sub>2</sub> sensing characteristics of magnetron-sputtered SnO<sub>2</sub> sensors

“…In case of Al doping, it is likely that the Fermi level moves towards the middle of the energy gap and ultimately creates the acceptor level (Mohagheghi and Saremi, 2004;Scanlon and Watson, 2012) below E F similar to the case of TiO 2 (Fig. 7a).…”

“…Moreover, they report that intensities decrease significantly and the peaks are broadened. This may possibly be caused by the replacement of Sn 4+ ions by Al 3+ ions, as already mentioned in Mohagheghi and Saremi (2004). The average grain size of SnO 2 : Al layers (12 nm) is smaller than that of SnO 2 (45 nm); the grain size was estimated by means of the Scherrer formula.…”

Structural and optical properties of SnO2–Al2O3 nanocomposite synthesized via sol-gel route

“…Semiconducting oxides ZnO, SnO 2 , In 2 O 3 and Cd 2 SnO 4 have been widely studied because of their great technological importance and novel properties including the structural, optical, electrical [1][2][3][4]. These nanomaterials exhibit high electrical conductivity, high optical transmittance in the UVVis region and high IR reflectance.…”

Transparent Conducting Oxides Based on Tin Oxide

“…Incorporation of Zn is reported to decrease the electron carrier concentration [21], whereas SnO 2 :Fe gas sensors [23] showed p-type response in an oxygen atmosphere. A few reports on p-type tin oxide use high doping levels (typically >8 at.%) of In [24][25][26], Ga [27] or Al [28] to produce a low hole carrier concentration. It is typically difficult to induce hole carriers in wide band-gap oxide semiconductors.…”