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Physical properties and band structure of reactive molecular beam epitaxy grown oxygen engineered
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10.1063/1.4767379
/content/aip/journal/jap/112/11/10.1063/1.4767379
http://aip.metastore.ingenta.com/content/aip/journal/jap/112/11/10.1063/1.4767379
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Normalized intensities of () and (002) reflections of 50 nm thick hafnia thin films as a function of substrate temperature (Hf-rate 0.7 Å/s, 1.5 sccm oxygen flow rate, 200 W rf-power). Solid lines are guides to the eye.

Image of FIG. 2.
FIG. 2.

Normalized intensities of () and (002) reflections of 50 nm thick hafnia thin films as a function of oxygen flow rate (Hf-rate 0.7 Å/s, , 200 W rf-power), solid lines are guides to the eye. The vertical dashed line indicates approximately the oxygen flow rate corresponding to stoichiometric composition.

Image of FIG. 3.
FIG. 3.

Exemplary image of cathodoluminescence of a reduced thin film on r-cut sapphire irradiated by 30 keV electrons from a RHEED gun. The same effect is also observed for thin films on c-cut substrates.

Image of FIG. 4.
FIG. 4.

(a) -scan for a 50 nm thick hafnium oxide thin film on c-cut sapphire grown under optimized conditions. (b) Corresponding XRR pattern. Inset: Rocking curve of the () peak.

Image of FIG. 5.
FIG. 5.

AFM picture of a 50 nm thick hafnium oxide film grown under optimized conditions with a surface roughness RMS of 0.22 nm in a measured area of .

Image of FIG. 6.
FIG. 6.

RHEED images of on c-cut sapphire during growth; (a) blank c-cut substrate before growth, (b) after 3 nm, (c) after 6 nm film thickness.

Image of FIG. 7.
FIG. 7.

Normalized intensities of () and (002) reflections of 200 nm thick hafnia thin films as a function of oxygen flow rate (Hf-rate 0.7 Å/s, , 200 W rf-power for 0-2.0 sccm, 300 W rf-power for 2.5 sccm). Solid lines are guides to the eye. The vertical dashed line indicates approximately the oxygen flow rate corresponding to stoichiometric composition.

Image of FIG. 8.
FIG. 8.

Diffraction patterns for 200 nm thick hafnia thin films and 50 nm metal Hf demonstrating switching of film orientation as a function of oxidation conditions. (a) 0 sccm oxygen flow rate (metallic Hf); (b) 1.0 sccm, 200 W; (c) 2.5 sccm, 300 W rf-power. Other deposition parameters were 0.7 Å/s Hf-rate, and .

Image of FIG. 9.
FIG. 9.

Photograph of three thin films: 0.3 sccm oxygen flow rate for highly reduced growth conditions; 1 sccm for reduced, and 2 sccm for moderate oxidation conditions. As comparison also a metallic Hf film is shown (0 sccm).

Image of FIG. 10.
FIG. 10.

(a) Transmission vs wavelength spectrum for a 30 nm thick thin film grown under reducing conditions. (b) Corresponding squared absorption coefficient vs. photon energy.

Image of FIG. 11.
FIG. 11.

Band gap vs. oxygen flow rate of thin films. The horizontal line indicates 5.7 eV for stoichiometric .

Image of FIG. 12.
FIG. 12.

Resistivity vs. temperature for 50 nm thick thin films grown (a) under slightly reducing (0.9 sccm oxygen flow), and (b) under highly reducing condition (0.6 sccm oxygen flow)).

Image of FIG. 13.
FIG. 13.

Room-temperature resistivity as a function of oxidation conditions. Films grown below 0.6 sccm oxygen flow rate show metallic , whereas above this threshold no major change in as a function of T is observed.

Image of FIG. 14.
FIG. 14.

Magnetization data obtained at 300 K for a 200 nm thick thin film grown under 0.3 sccm oxygen flow rate on c-cut sapphire. The diamagnetic substrate contribution is not subtracted. All investigated films show diamagnetic behavior, regardless of the oxidation conditions.

Image of FIG. 15.
FIG. 15.

Left side: Band model of stoichiometric . Right side: Simplified band model of oxygen deficient .

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/content/aip/journal/jap/112/11/10.1063/1.4767379
2012-12-06
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Physical properties and band structure of reactive molecular beam epitaxy grown oxygen engineered HfO2±x
http://aip.metastore.ingenta.com/content/aip/journal/jap/112/11/10.1063/1.4767379
10.1063/1.4767379
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