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Optical properties and bandgap evolution of ALD HfSiOx films.

Yang W, Fronk M, Geng Y, Chen L, Sun QQ, Gordan OD, Zhou P, Zahn DR, Zhang DW - Nanoscale Res Lett (2015)

Bottom Line: Hafnium silicate films with pure HfO2 and SiO2 samples as references were fabricated by atomic layer deposition (ALD) in this work.Experimental results show that optical constants and bandgap of the hafnium silicate films can be tuned by the film composition, and a nonlinear change behavior of bandgap with SiO2 fraction was observed.This phenomenon mainly originates from the intermixture of d-state electrons in HfO2 and Si-O antibonding states in SiO2.

View Article: PubMed Central - PubMed

Affiliation: Institute of Advanced Nanodevices, School of Microelectronics, Fudan University, No. 220 Handan Road, Shanghai, 200433 China.

ABSTRACT
Hafnium silicate films with pure HfO2 and SiO2 samples as references were fabricated by atomic layer deposition (ALD) in this work. The optical properties of the films as a function of the film composition were measured by vacuum ultraviolet (VUV) ellipsometer in the energy range of 0.6 to 8.5 eV, and they were investigated systematically based on the Gaussian dispersion model. Experimental results show that optical constants and bandgap of the hafnium silicate films can be tuned by the film composition, and a nonlinear change behavior of bandgap with SiO2 fraction was observed. This phenomenon mainly originates from the intermixture of d-state electrons in HfO2 and Si-O antibonding states in SiO2.

No MeSH data available.


Determination of the optical bandgap.
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Fig3: Determination of the optical bandgap.

Mentions: Optical bandgap of the films were determined by plotting the empirical expression (nαhν)1/2 versus hν, as shown in Figure 3, where n, α, and hν stand for the index of refraction, the absorption coefficient, and the photon energy, respectively. The absorption coefficient α can be easily obtained by the equation α = 4πk/λ, where λ is the wavelength of the incidence light [25]. By extrapolating the straight near the band edge to zero, the crossing point with the x-axis is considered to be the optical bandgap of the film. To make it clear, bandgap determination of HfO2 is taken as an example and is shown in the inset of Figure 3. The extracted bandgap of pure HfO2 film is 5.64 eV, in good agreement with the previously reported values 5.25 to 5.8 eV for HfO2 [23,26,27].Figure 3


Optical properties and bandgap evolution of ALD HfSiOx films.

Yang W, Fronk M, Geng Y, Chen L, Sun QQ, Gordan OD, Zhou P, Zahn DR, Zhang DW - Nanoscale Res Lett (2015)

Determination of the optical bandgap.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385042&req=5

Fig3: Determination of the optical bandgap.
Mentions: Optical bandgap of the films were determined by plotting the empirical expression (nαhν)1/2 versus hν, as shown in Figure 3, where n, α, and hν stand for the index of refraction, the absorption coefficient, and the photon energy, respectively. The absorption coefficient α can be easily obtained by the equation α = 4πk/λ, where λ is the wavelength of the incidence light [25]. By extrapolating the straight near the band edge to zero, the crossing point with the x-axis is considered to be the optical bandgap of the film. To make it clear, bandgap determination of HfO2 is taken as an example and is shown in the inset of Figure 3. The extracted bandgap of pure HfO2 film is 5.64 eV, in good agreement with the previously reported values 5.25 to 5.8 eV for HfO2 [23,26,27].Figure 3

Bottom Line: Hafnium silicate films with pure HfO2 and SiO2 samples as references were fabricated by atomic layer deposition (ALD) in this work.Experimental results show that optical constants and bandgap of the hafnium silicate films can be tuned by the film composition, and a nonlinear change behavior of bandgap with SiO2 fraction was observed.This phenomenon mainly originates from the intermixture of d-state electrons in HfO2 and Si-O antibonding states in SiO2.

View Article: PubMed Central - PubMed

Affiliation: Institute of Advanced Nanodevices, School of Microelectronics, Fudan University, No. 220 Handan Road, Shanghai, 200433 China.

ABSTRACT
Hafnium silicate films with pure HfO2 and SiO2 samples as references were fabricated by atomic layer deposition (ALD) in this work. The optical properties of the films as a function of the film composition were measured by vacuum ultraviolet (VUV) ellipsometer in the energy range of 0.6 to 8.5 eV, and they were investigated systematically based on the Gaussian dispersion model. Experimental results show that optical constants and bandgap of the hafnium silicate films can be tuned by the film composition, and a nonlinear change behavior of bandgap with SiO2 fraction was observed. This phenomenon mainly originates from the intermixture of d-state electrons in HfO2 and Si-O antibonding states in SiO2.

No MeSH data available.