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Dielectric Relaxation of La-Doped Zirconia Caused by Annealing Ambient

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ABSTRACT

La-doped zirconia films, deposited by ALD at 300°C, were found to be amorphous with dielectric constants (k-values) up to 19. A tetragonal or cubic phase was induced by post-deposition annealing (PDA) at 900°C in both nitrogen and air. Higher k-values (~32) were measured following PDA in air, but not after PDA in nitrogen. However, a significant dielectric relaxation was observed in the air-annealed film, and this is attributed to the formation of nano-crystallites. The relaxation behavior was modeled using the Curie–von Schweidler (CS) and Havriliak–Negami (HN) relationships. The k-value of the as-deposited films clearly shows a mixed CS and HN dependence on frequency. The CS dependence vanished after annealing in air, while the HN dependence disappeared after annealing in nitrogen.

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Frequency dependence of k-value of La0.35Zr0.65O2 dielectric for as-deposited and PDA samples. Significant dielectric relaxation was observed in the air-annealed sample. Solid lines are the fitting results using equations (1) and (2).
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Figure 6: Frequency dependence of k-value of La0.35Zr0.65O2 dielectric for as-deposited and PDA samples. Significant dielectric relaxation was observed in the air-annealed sample. Solid lines are the fitting results using equations (1) and (2).

Mentions: The relationship between the extracted k-value and test frequency shown in Figure 6 indicates that significant dielectric relaxation only occurs in the air-annealed sample. Parasitic effects could not be the cause of the frequency dispersion observed because of the sample preparation and measurement procedures described earlier. Significant frequency dispersion was not seen in other MOSCs fabricated using the same substrates prepared and measured in exactly the same way. We conclude therefore that the frequency dispersion observed in the La0.35Zr0.65O2 film annealed in air is a real material property of this dielectric. There are two important observations in Figure 6: (1) PDA in air increases the k-value of the La0.35Zr0.65O2 dielectric significantly (k-value reaches 32 at 1 kHz), along with a significant dielectric relaxation. (2) There is less of an effect on the k-value for the film annealed in N2, with a small increase in k-value at some frequencies and a flatter frequency response compared to the as-deposited sample. Both effects of temperature/ambient and causes of dielectric relaxation are discussed later.


Dielectric Relaxation of La-Doped Zirconia Caused by Annealing Ambient
Frequency dependence of k-value of La0.35Zr0.65O2 dielectric for as-deposited and PDA samples. Significant dielectric relaxation was observed in the air-annealed sample. Solid lines are the fitting results using equations (1) and (2).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211993&req=5

Figure 6: Frequency dependence of k-value of La0.35Zr0.65O2 dielectric for as-deposited and PDA samples. Significant dielectric relaxation was observed in the air-annealed sample. Solid lines are the fitting results using equations (1) and (2).
Mentions: The relationship between the extracted k-value and test frequency shown in Figure 6 indicates that significant dielectric relaxation only occurs in the air-annealed sample. Parasitic effects could not be the cause of the frequency dispersion observed because of the sample preparation and measurement procedures described earlier. Significant frequency dispersion was not seen in other MOSCs fabricated using the same substrates prepared and measured in exactly the same way. We conclude therefore that the frequency dispersion observed in the La0.35Zr0.65O2 film annealed in air is a real material property of this dielectric. There are two important observations in Figure 6: (1) PDA in air increases the k-value of the La0.35Zr0.65O2 dielectric significantly (k-value reaches 32 at 1 kHz), along with a significant dielectric relaxation. (2) There is less of an effect on the k-value for the film annealed in N2, with a small increase in k-value at some frequencies and a flatter frequency response compared to the as-deposited sample. Both effects of temperature/ambient and causes of dielectric relaxation are discussed later.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

La-doped zirconia films, deposited by ALD at 300°C, were found to be amorphous with dielectric constants (k-values) up to 19. A tetragonal or cubic phase was induced by post-deposition annealing (PDA) at 900°C in both nitrogen and air. Higher k-values (~32) were measured following PDA in air, but not after PDA in nitrogen. However, a significant dielectric relaxation was observed in the air-annealed film, and this is attributed to the formation of nano-crystallites. The relaxation behavior was modeled using the Curie–von Schweidler (CS) and Havriliak–Negami (HN) relationships. The k-value of the as-deposited films clearly shows a mixed CS and HN dependence on frequency. The CS dependence vanished after annealing in air, while the HN dependence disappeared after annealing in nitrogen.

No MeSH data available.


Related in: MedlinePlus