Issue 21, 2024

Contactless analysis of surface passivation and charge transfer at the TiO2–Si interface

Abstract

Transition metal oxides are pivotal in enhancing surface passivation and facilitating charge transfer (CT) in silicon based photonic devices, improving their efficacy and affordability through interfacial engineering. This study investigates TiO2/Si heterojunctions prepared by atomic layer deposition (ALD) with different pre-ALD chemical and post-ALD thermal treatments, exploring their influence on the surface passivation and the correlation with the CT at the TiO2–Si interface. Surface passivation quality is evaluated by the photoconductance decay method to study the effective carrier lifetime, while CT from Si to TiO2 is examined by transient reflectance spectroscopy. Surprisingly, the as-deposited TiO2 on HF-treated n-Si (without interfacial SiOx) demonstrates superior surface passivation with an effective lifetime of 1.23 ms, twice that of TiO2/SiOx/n-Si, and a short characteristic CT time of 200 ps, tenfold faster than that of TiO2/SiOx/n-Si. Post-ALD annealing at temperatures approaching the TiO2 crystallization onset re-introduces the SiOx layers in HF-treated samples and induces chemical and structural changes in all the samples which decrease passivation and prolong the CT time and are hence detrimental to the photonic device performance.

Graphical abstract: Contactless analysis of surface passivation and charge transfer at the TiO2–Si interface

Supplementary files

Article information

Article type
Paper
Submitted
06 Marts 2024
Accepted
03 Maijs 2024
First published
03 Maijs 2024
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2024,26, 15268-15276

Contactless analysis of surface passivation and charge transfer at the TiO2–Si interface

R. Khan, X. Liu, V. Vähänissi, H. Ali-Löytty, H. P. Pasanen, H. Savin and N. V. Tkachenko, Phys. Chem. Chem. Phys., 2024, 26, 15268 DOI: 10.1039/D4CP00992D

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