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Tuning the band gap and carrier concentration of titania films grown by spatial atomic layer deposition: a precursor comparison.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Armstrong, Claire 
Delumeau, Louis-Vincent  ORCID logo  https://orcid.org/0000-0003-1700-0536
Muñoz-Rojas, David  ORCID logo  https://orcid.org/0000-0003-1234-0814
Kursumovic, Ahmed 
MacManus-Driscoll, Judith 

Abstract

Spatial atomic layer deposition retains the advantages of conventional atomic layer deposition: conformal, pinhole-free films and excellent control over thickness. Additionally, it allows higher deposition rates and is well-adapted to depositing metal oxide nanofilms for photovoltaic cells and other devices. This study compares the morphological, electrical and optical properties of titania thin films deposited by spatial atomic layer deposition from titanium isopropoxide (TTIP) and titanium tetrachloride (TiCl4) over the temperature range 100-300 °C, using the oxidant H2O. Amorphous films were deposited at temperatures as low as 100 °C from both precursors: the approach is suitable for applying films to temperature-sensitive devices. An amorphous-to-crystalline transition temperature was observed for both precursors resulting in surface roughening, and agglomerates for TiCl4. Both precursors formed conformal anatase films at 300 °C, with growth rates of 0.233 and 0.153 nm s-1 for TiCl4 and TTIP. A drawback of TiCl4 use is the HCl by-product, which was blamed for agglomeration in the films. Cl contamination was the likely cause of band gap narrowing and higher defect densities compared to TTIP-grown films. The carrier concentration of the nanofilms was found to increase with deposition temperature. The films were tested in hybrid bilayer solar cells to demonstrate their appropriateness for photovoltaic devices.

Description

Keywords

34 Chemical Sciences, 3406 Physical Chemistry, 40 Engineering, 4016 Materials Engineering, 4018 Nanotechnology

Journal Title

Nanoscale Adv

Conference Name

Journal ISSN

2516-0230
2516-0230

Volume Title

3

Publisher

Royal Society of Chemistry (RSC)
Sponsorship
European Commission (219332)
European Commission Horizon 2020 (H2020) ERC (882929)
Royal Academy of Engineering (RAEng) (CiET1819\24)
Engineering and Physical Sciences Research Council (EP/P007767/1)