Experimental Determination of the Band Offset of Rare Earth Oxides on Various Semiconductors

Seguini, Gabriele; Perego, Michele; Fanciulli, M.

doi:10.1007/11499893_16

Cited by 4 publications

(2 citation statements)

References 44 publications

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“…From the positions of the Si 2p and Yb 4d given in section 3.1.1, we obtain for the Yb 2 O 3 /Si film a VBO of 2.4 ± 0.2 eV. This is in agreement with values reported in the literature for other RE oxide/Si interfaces [43]. In order to limit leakage currents to acceptable levels, potential barriers for both electrons and holes should be greater than 1 eV.…”

Section: Valence Bandsupporting

confidence: 88%

“…To overcome problems related to low statistics in the valence band and to the overlapping of Yb 4f, O 2p, F 2p and Si 3sp states, which could make it difficult to disentangle unambiguously the position of the VBM of the substrate and of the overlayer in the same spectrum, the VBO is derived in the different cases by monitoring the shifts of Yb 4d and Si 2p core levels and considering the separation of the Si 2p from the Si VBM and of the Yb 4d from the RE oxide VBM in the bulk materials, according to the method described in [43]. From the positions of the Si 2p and Yb 4d given in section 3.1.1, we obtain for the Yb 2 O 3 /Si film a VBO of 2.4 ± 0.2 eV.…”

Section: Valence Bandmentioning

confidence: 99%

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Atomic and electronic structure of ultrathin fluoride barrier layers at the oxide/Si interface

Pasquali¹,

Montecchi²,

Nannarone³

et al. 2011

J. Phys.: Condens. Matter

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A SrF(2) ultrathin barrier layer on Si(001) is used to form a sharp interface and block reactivity and intermixing between the semiconductor and a Yb(2)O(3) overlayer. Yb(2)O(3)/Si(001) and Yb(2)O(3)/SrF(2)/Si(001) interfaces grown in ultra high vacuum by molecular beam epitaxy are studied by photoemission and x-ray absorption fine structure. Without the fluoride interlayer, Yb(2)O(3)/Si(001) presents an interface reacted region formed by SiO(x) and/or silicate compounds, which is about 9 Å thick and increases up to 14-15 Å after annealing at 500-700 °C. A uniform single layer of SrF(2) molecules blocks intermixing and reduces the oxidized Si region to 2.4 Å after deposition and to 3.5 Å after annealing at 500 °C. In both cases we estimate a conduction band offset and a valence band offset of ∼ 1.7 eV and 2.4 eV between the oxide and Si, respectively. X-ray absorption fine structure measurements at the Yb L(III) edge suggest that the Yb oxide films exhibit a significant degree of static disorder with and without the fluoride barrier. Sr K edge measurements indicate that the ultrathin fluoride films are reacted, with the formation of bonds between Si and Sr; the Sr-Sr and Sr-F interatomic distances in the ultrathin fluoride barrier film are relaxed to the bulk value.

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Section: Valence Bandsupporting

confidence: 88%

Section: Valence Bandmentioning

confidence: 99%

Atomic and electronic structure of ultrathin fluoride barrier layers at the oxide/Si interface

Pasquali¹,

Montecchi²,

Nannarone³

et al. 2011

J. Phys.: Condens. Matter

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Conduction band offset of HfO2 on GaAs

Seguini¹,

Perego²,

Spiga³

et al. 2007

Applied Physics Letters

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A detailed analysis of the band alignment between molecular beam deposited amorphous HfO2 and GaAs is reported. The conduction band offset, measured by internal photoemission (IPE), is 1.9±0.2eV. The valence band offset (VBO) is probed by x-ray photoelectron spectroscopy (XPS). The accurate determination of the VBO requires a careful evaluation of differential charging phenomena and consequently a proper correction of the energy scale. The measured VBO value is 2.1±0.1eV. Since the HfO2 gap is 5.6eV, as detected by photoconductivity analysis, the results obtained by IPE and XPS are in excellent agreement.

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Charging phenomena in dielectric/semiconductor heterostructures during x-ray photoelectron spectroscopy measurements

Perego¹,

Seguini²

2011

Journal of Applied Physics

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The determination of the valence band offset (VBO) by x-ray photoelectron spectroscopy (XPS) is commonly performed using the so-called Kraut’s method that was developed for VBO determination in semiconductor/semiconductor heterojunctions. Although the physical model, which is the basis of the method, can be safely extended to dielectric/semiconductor (D/S) heterojunctions, in these systems a careful evaluation of the experimental results is necessary due to the differential charging phenomena originating at D/S interface during x-ray bombardment. As a consequence, precise determination of the VBO requires an accurate calibration of the energy scale in order to remove artifacts induced by the progressive charging of the oxide during the XPS measurement. In this work a detailed analysis of the band alignment between e-beam evaporated amorphous HfO2 films and Si substrates is reported. The HfO2/Si heterojunction was selected as a prototype for this study since HfO2 based dielectrics have already been implemented as gate dielectrics in real devices and have been the subject of a wide number of publications providing controversial results in terms of VBO values. A clear dependence of the binding energy of the Hf 4f and O 1s core lines on the thickness of the HfO2 film is identified. The time evolution of these signals indicates that different steady states are reached after prolonged x-ray bombardment depending on the thickness of the HfO2 films. On the basis of the original work of Iwata et al. [J. App. Phys. 79, 6653 (1996)], a rigorous method to remove these artifacts and empirically determine the real band offsets in D/S heterojunctions is proposed and validated by comparison with internal photoemission and photoconductivity data obtained on the same set of samples.

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Experimental Determination of the Band Offset of Rare Earth Oxides on Various Semiconductors

Cited by 4 publications

References 44 publications

Atomic and electronic structure of ultrathin fluoride barrier layers at the oxide/Si interface

Atomic and electronic structure of ultrathin fluoride barrier layers at the oxide/Si interface

Conduction band offset of HfO2 on GaAs

Charging phenomena in dielectric/semiconductor heterostructures during x-ray photoelectron spectroscopy measurements

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