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.
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.
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.
(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.
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 .
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.
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.
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 .
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).
(a) Transmission vs wavelength spectrum for a 30 nm thick thin film grown under reducing conditions. (b) Corresponding squared absorption coefficient vs. photon energy.
Band gap vs. oxygen flow rate of thin films. The horizontal line indicates 5.7 eV for stoichiometric .
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)).
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.
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.
Left side: Band model of stoichiometric . Right side: Simplified band model of oxygen deficient .
Article metrics loading...
Full text loading...