**3. Formation of sol-gel-derived ZrO2 on Si(001) wafers fired in air**

The XPS spectra of the Zr 3d and O 1s emissions from sol-gel-derived ZrO2 thin films fired at 350 °C are shown in [Figure 3(a)] and [Figure 3(b)], respectively. ZrO2 thin films fired at 450, 550, and 700 °C were also evaluated and similar results were obtained. The Zr 3d 5/2 line was at 182.1±0.1 eV, which is in good agreement with that of the bulk ZrO2 (182~182.5 eV) (Moulder et al., 1995). The O 1s spectrum at 350 °C was separated into two Gaussian-Lorentzian features corresponding to two chemical states by the nonlinear least-squares method [Figure 3(b)].

Fig. 3. XPS spectra of sol-gel-derived ZrO2 thin films: (a) XPS Zr 3d spectrum and (b) XPS O 1s spectrum. Solid lines are the observed XPS spectra and dashed lines are for Zr 3d and O 1s spectra, which have two Gaussian peaks fitted by the nonlinear least-squares algorithm (Shimizu et al., 2009).

from the sol-gel-derived HfO2 film fired at 450 °C indicated that the HfO2 film was amorphous. The Hf 4f 7/2 line was determined to be at 16.2±0.1 eV, which is in good

Crystallized HfO2 films fired at temperatures of 550 and 700 °C showed similar XPS spectra regardless of whether they were amorphous or crystalline. The crystallization of sol-gelderived HfO2 films will be discussed later. The O 1s spectrum at 450 °C [Figure 2(b)] was separated into two Gaussian-Lorentzian features corresponding to two chemical states by using the nonlinear least-squares method. One large peak at 530.1 eV (designated as the low-binding-energy component: LBC) was from Hf-O bonds and the other low peak at 531.8 eV (designated as the high-binding-energy component: HBC) was from Hf-OH bonds near the bulk at the surface area. However, since the binding energy of H2O was slightly larger (533.2 eV) than that of OH, the peak due to physisorbed H2O may have been included in

The XPS spectra of the Zr 3d and O 1s emissions from sol-gel-derived ZrO2 thin films fired at 350 °C are shown in [Figure 3(a)] and [Figure 3(b)], respectively. ZrO2 thin films fired at 450, 550, and 700 °C were also evaluated and similar results were obtained. The Zr 3d 5/2 line was at 182.1±0.1 eV, which is in good agreement with that of the bulk ZrO2 (182~182.5 eV) (Moulder et al., 1995). The O 1s spectrum at 350 °C was separated into two Gaussian-Lorentzian features corresponding to two chemical states by the nonlinear least-squares

> O 1s O 1s

O 1s

O 1s

(ZrO2)

O 1s

LBC

 (ZrO2) 530.2 eV

(OH)

 (OH) 532.0 eV

HBC

(a) (b)

Intensity (arb. unit)

534 532 530 528

Binding Energy (eV)

Fig. 3. XPS spectra of sol-gel-derived ZrO2 thin films: (a) XPS Zr 3d spectrum and (b) XPS O 1s spectrum. Solid lines are the observed XPS spectra and dashed lines are for Zr 3d and O 1s spectra, which have two Gaussian peaks fitted by the nonlinear least-squares

agreement with that of the bulk HfO2 (Chiou et al., 2007, Moulder et al., 1995).

**3. Formation of sol-gel-derived ZrO2 on Si(001) wafers fired in air** 

**Zr 3d 5/2 182.1 eV**

HBC in the present XPS measurements.

method [Figure 3(b)].

Zr 3d Zr 3d 5/2

Zr 3d 3/2

Intensity (arb. unit)

algorithm (Shimizu et al., 2009).

190 188 186 184 182 180 178 176

Binding Energy (eV)

One large peak at 530.2 eV (designated as the low-binding-energy component: LBC) was from Zr-O bonds and the other low peak at 532.0 eV (designated as the high-binding-energy component: HBC) was from Zr-OH bonds near the bulk at the surface area. However, since the binding energy of H2O was slightly higher (533.2 eV) than that of OH, the peak due to physisorbed H2O may [have been included in HBC?] in the present XPS measurements.
