Anomalous thermal conductivity in amorphous niobium pentoxide thin films: A correlation study between structure and thermal properties
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In: Materialia, Vol. 26.2022, No. December, 101601, 13.10.2022.
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TY - JOUR
T1 - Anomalous thermal conductivity in amorphous niobium pentoxide thin films
T2 - A correlation study between structure and thermal properties
AU - Mitterhuber, Lisa Maria
AU - Kaliyaperumal Veerapandiyan, Vignaswaran
AU - Deluca, Marco
AU - Misture, Scott
AU - Schaeperkoetter, Joe
AU - Tkadletz, Michael
AU - Mitterer, Christian
AU - Spitaler, Jürgen
PY - 2022/10/13
Y1 - 2022/10/13
N2 - Niobium pentoxide (Nb2O5) based thin films are predominantly used in optical filters, solar cells, electrochromic devices, sensors and microelectronic devices. The temperature-dependent thermophysical properties of Nb2O5 films are crucial for the performance and reliability of such devices. Within this work, for the first time, the thermal properties of sputter deposited Nb2O5 films are correlated with their structural properties at different length scales. Thermal measurements were carried out by time-domain thermoreflectance, yielding a thermal conductivity of 3.0±0.3 W/mK at 25 °C for crystalline Nb2O5 films, which decreases to 2.6±0.2 W/mK at 450 °C. In contrast, amorphous Nb2O5 films had a thermal conductivity of 2.2±0.2 W/mK below 275 °C. Above 275 °C, an abrupt increase in thermal conductivity up to a maximum value of 2.8±0.2 W/mK at 325 °C was recorded. The average and local structure are determined by in-situ high-temperature X-ray diffraction and in-situ high-temperature Raman spectroscopy, respectively. These characterization techniques together enable to cross-correlate structural and thermal properties of Nb2O5 thin films highlighting the observed peculiarity of the thermal conductivity. This substantial increase in thermal conductivity cannot be linked to any macroscopic phase change but rather to a local phase rearrangement near the crystallization temperature, evidenced by temperature-dependent Raman spectra analysis. This study serves as a guide to engineering future Nb2O5 based thin film devices and for their reliability optimization.
AB - Niobium pentoxide (Nb2O5) based thin films are predominantly used in optical filters, solar cells, electrochromic devices, sensors and microelectronic devices. The temperature-dependent thermophysical properties of Nb2O5 films are crucial for the performance and reliability of such devices. Within this work, for the first time, the thermal properties of sputter deposited Nb2O5 films are correlated with their structural properties at different length scales. Thermal measurements were carried out by time-domain thermoreflectance, yielding a thermal conductivity of 3.0±0.3 W/mK at 25 °C for crystalline Nb2O5 films, which decreases to 2.6±0.2 W/mK at 450 °C. In contrast, amorphous Nb2O5 films had a thermal conductivity of 2.2±0.2 W/mK below 275 °C. Above 275 °C, an abrupt increase in thermal conductivity up to a maximum value of 2.8±0.2 W/mK at 325 °C was recorded. The average and local structure are determined by in-situ high-temperature X-ray diffraction and in-situ high-temperature Raman spectroscopy, respectively. These characterization techniques together enable to cross-correlate structural and thermal properties of Nb2O5 thin films highlighting the observed peculiarity of the thermal conductivity. This substantial increase in thermal conductivity cannot be linked to any macroscopic phase change but rather to a local phase rearrangement near the crystallization temperature, evidenced by temperature-dependent Raman spectra analysis. This study serves as a guide to engineering future Nb2O5 based thin film devices and for their reliability optimization.
U2 - 10.1016/j.mtla.2022.101601
DO - 10.1016/j.mtla.2022.101601
M3 - Article
VL - 26.2022
JO - Materialia
JF - Materialia
SN - 2589-1529
IS - December
M1 - 101601
ER -