Upconversion luminescence from magnetron-sputtered Er3+-doped TiO2 films: Influence of deposition- and annealing temperatures and correlation to decay times

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Upconversion luminescence from magnetron-sputtered Er3+-doped TiO2 films : Influence of deposition- and annealing temperatures and correlation to decay times. / Lakhotiya, Harish; Christiansen, Jeppe; Hansen, John Lundsgaard; BaIling, Peter; Julsgaard, Brian.

In: Journal of Applied Physics, Vol. 124, No. 16, 163105, 28.10.2018.

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@article{cbbc92ba82464b29ae11ddc90bb7f24e,
title = "Upconversion luminescence from magnetron-sputtered Er3+-doped TiO2 films: Influence of deposition- and annealing temperatures and correlation to decay times",
abstract = "The optical properties of radio-frequency magnetron sputtered TiO2 thin films doped with Er3+ are strongly influenced by the deposition and post-annealing temperatures. This has an impact on the applications of the material for upconversion, i.e., the merging of two low-energy photons to one photon of higher energy. Maximum upconversion luminescence (UCL) yield is obtained using a deposition temperature of 350 degrees C without post-annealing. Motivated by the possibilities that become available by sequential depositions (several layers), the effect of post-annealing is systematically investigated. In general, post-annealing treatments reduce the UCL; however, for the lowest deposition temperatures, post-annealing has a positive impact on the UCL provided that the samples are not exposed to ambient air prior to the annealing step. These observations are further analyzed using time-resolved photoluminescence spectroscopy for determining the characteristic decay times of the Er3+ energy levels in the different samples. It is found that the UCL yield scales to a good approximation linearly with the product of the decay times of the two lowest-lying Er3+ excited energy levels (I-4(11/2) and I-4(13/2)). The combined data provide strong evidence that the reduction in UCL is due to the opening of non-radiative decay channels from the Er3+ excited levels. Structural measurements show no change of the amorphous samples upon annealing, so these decay channels are most likely related to energy transfer between Er3+ and defect states in the TiO2 bandgap. The non-radiative decay could possibly be related to the loss of hydrogen termination of dangling bonds or related to the oxygen vacancies in TiO2. Published by AIP Publishing.",
keywords = "THIN-FILMS, OPTICAL-PROPERTIES, SURFACE SCIENCE, SOLAR-CELL, COATINGS, ENHANCEMENT, AMPLIFIERS, TIO2(110), HYDROGEN, DEFECTS",
author = "Harish Lakhotiya and Jeppe Christiansen and Hansen, {John Lundsgaard} and Peter BaIling and Brian Julsgaard",
year = "2018",
month = oct,
day = "28",
doi = "10.1063/1.5037059",
language = "English",
volume = "124",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "AMER INST PHYSICS",
number = "16",

}

RIS

TY - JOUR

T1 - Upconversion luminescence from magnetron-sputtered Er3+-doped TiO2 films

T2 - Influence of deposition- and annealing temperatures and correlation to decay times

AU - Lakhotiya, Harish

AU - Christiansen, Jeppe

AU - Hansen, John Lundsgaard

AU - BaIling, Peter

AU - Julsgaard, Brian

PY - 2018/10/28

Y1 - 2018/10/28

N2 - The optical properties of radio-frequency magnetron sputtered TiO2 thin films doped with Er3+ are strongly influenced by the deposition and post-annealing temperatures. This has an impact on the applications of the material for upconversion, i.e., the merging of two low-energy photons to one photon of higher energy. Maximum upconversion luminescence (UCL) yield is obtained using a deposition temperature of 350 degrees C without post-annealing. Motivated by the possibilities that become available by sequential depositions (several layers), the effect of post-annealing is systematically investigated. In general, post-annealing treatments reduce the UCL; however, for the lowest deposition temperatures, post-annealing has a positive impact on the UCL provided that the samples are not exposed to ambient air prior to the annealing step. These observations are further analyzed using time-resolved photoluminescence spectroscopy for determining the characteristic decay times of the Er3+ energy levels in the different samples. It is found that the UCL yield scales to a good approximation linearly with the product of the decay times of the two lowest-lying Er3+ excited energy levels (I-4(11/2) and I-4(13/2)). The combined data provide strong evidence that the reduction in UCL is due to the opening of non-radiative decay channels from the Er3+ excited levels. Structural measurements show no change of the amorphous samples upon annealing, so these decay channels are most likely related to energy transfer between Er3+ and defect states in the TiO2 bandgap. The non-radiative decay could possibly be related to the loss of hydrogen termination of dangling bonds or related to the oxygen vacancies in TiO2. Published by AIP Publishing.

AB - The optical properties of radio-frequency magnetron sputtered TiO2 thin films doped with Er3+ are strongly influenced by the deposition and post-annealing temperatures. This has an impact on the applications of the material for upconversion, i.e., the merging of two low-energy photons to one photon of higher energy. Maximum upconversion luminescence (UCL) yield is obtained using a deposition temperature of 350 degrees C without post-annealing. Motivated by the possibilities that become available by sequential depositions (several layers), the effect of post-annealing is systematically investigated. In general, post-annealing treatments reduce the UCL; however, for the lowest deposition temperatures, post-annealing has a positive impact on the UCL provided that the samples are not exposed to ambient air prior to the annealing step. These observations are further analyzed using time-resolved photoluminescence spectroscopy for determining the characteristic decay times of the Er3+ energy levels in the different samples. It is found that the UCL yield scales to a good approximation linearly with the product of the decay times of the two lowest-lying Er3+ excited energy levels (I-4(11/2) and I-4(13/2)). The combined data provide strong evidence that the reduction in UCL is due to the opening of non-radiative decay channels from the Er3+ excited levels. Structural measurements show no change of the amorphous samples upon annealing, so these decay channels are most likely related to energy transfer between Er3+ and defect states in the TiO2 bandgap. The non-radiative decay could possibly be related to the loss of hydrogen termination of dangling bonds or related to the oxygen vacancies in TiO2. Published by AIP Publishing.

KW - THIN-FILMS

KW - OPTICAL-PROPERTIES

KW - SURFACE SCIENCE

KW - SOLAR-CELL

KW - COATINGS

KW - ENHANCEMENT

KW - AMPLIFIERS

KW - TIO2(110)

KW - HYDROGEN

KW - DEFECTS

U2 - 10.1063/1.5037059

DO - 10.1063/1.5037059

M3 - Journal article

VL - 124

JO - Journal of Applied Physics

JF - Journal of Applied Physics

SN - 0021-8979

IS - 16

M1 - 163105

ER -