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ABSTRACT: In this work, Gd2O3 thin films grown by molecular beam epitaxy on Si(1 1 1) substrates were investigated by various diffraction methods. The Gd2O3 layers exhibit a highly perfect cubic bixbyite structure with a single domain orientation, low lattice mismatch with Si and good crystallinity. Threefold in-plane symmetry and bright streaky patterns were observed during the oxide growth by in situ high-energy electron diffraction. X-ray diffraction results demonstrate that Gd2O3 on Si(1 1 1) is fully epitaxial with a single domain orientation with aandepitaxial relationship. The lattice parameter of Gd2O3 is slightly smaller than the one of the Si substrate. In the in-plane direction, the Gd2O3 layer is only −0.1% mismatched with the Si substrate (relative to 2aSi). This indicates a pseudomorphic growth of Gd2O3 on Si(1 1 1), where the Gd2O3 layer experiences tensile strain in the in-plane direction and compressive strain in the out-of-plane direction.
Semiconductor Science and Technology 03/2009; 24(4):045021. · 1.72 Impact Factor
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ABSTRACT: The ability to integrate crystalline metal oxide dielectric barrier layers into silicon structures can open the way for a variety of novel applications which enhances the functionality and flexibility ranging from high-K replacements in future MOS devices to oxide/silicon/oxide heterostructures for nanoelectronic application in quantum-effect devices. We present results for crystalline gadolinium oxides on silicon in the cubic bixbyite structure grown by solid source molecular beam epitaxy. Additional oxygen supply during growth improves the dielectric properties significantly. Experimental results for Gd2O3-based MOS capacitors grown under optimized conditions show that these layers are excellent candidates for application as very thin high-K materials replacing SiO2 in future MOS devices. Epitaxial growth of lanthanide oxides on silicon without any interfacial layer has the advantage of enabling defined interfaces engineering. We will show that the electrical properties of epitaxial Gd2O3 thin films on Si substrates can further be improved significantly by an atomic control of interfacial structures. Finally, we will present a new approach for nanostructure formation which is based on solid-phase epitaxy of the Si quantum-well combined with simultaneous vapor-phase epitaxy of the insulator on top of the quantum-well. Ultra-thin single-crystalline Si buried in a single-crystalline insulator matrix with sharp interfaces was obtained by this approach on Si(111). In addition, structures consisting of a single-crystalline oxide layer with embedded Si nanoclusters for memory applications will also be demonstrated. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Physica Status Solidi (A) Applications and Materials 03/2008; 205(4):695 - 707. · 1.46 Impact Factor
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ABSTRACT: We investigate the impact of rapid thermal anneals on structural and electrical properties of crystalline Gd2O3 layers grown on Si with different orientations. Due to additional oxygen from the annealing ambient, a structureless two-layer stack (silicon-oxide-like and silicate-like) between the silicon and the crystalline oxide will be formed. The degradation of layers can be significantly reduced by sealing the layer with a-Si prior to annealing. For the capped layers, the effective capacitance equivalent thickness increases only slightly even after a 1000 °C anneal.
Semiconductor Science and Technology 02/2008; 23(3):035010. · 1.72 Impact Factor
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ABSTRACT: We will present results for crystalline gadolinium oxides on silicon in the cubic bixbyite structure grown by solid source molecular beam epitaxy. Additional oxygen supply during growth improves the dielectric properties significantly. Experimental results for Gd 2 O 3 -based MOS capacitors grown under optimized conditions show that these layers are excellent candidates for application as very thin high-k materials replacing SiO 2 in future MOS devices. We also will present a new approach for nanostructure formation which is based on solid-phase epitaxy of the Si quantum-well combined with simultaneous vapor-phase epitaxy of the insulator on top of the quantum-well. Ultra-thin single-crystalline Si buried in a single-crystalline insulator matrix with sharp interfaces was obtained by this approach on Si(111). Finally, the incorporation of crystalline Si islands into single-crystalline oxide layers will be demonstrated.
Microelectronic Engineering 01/2007; 84:2222-2225. · 1.56 Impact Factor
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ABSTRACT: The ability to integrate low-dimensional crystalline silicon into crystalline insulators with high dielectric constant (high-k) can open the way for a variety of novel applications ranging from high-k replacement in future nonvolatile memory devices to insulator/Si/insulator structures for nanoelectronic applications. We will present an approach for nanostructure fabrication by incorporation of crystalline silicon into epitaxial oxide that is based on a solid-phase epitaxy of Si. In dependence on the preparation conditions we obtained nanostructures containing an either ultra-thin single-crystalline Si quantum-well buried in single-crystalline oxide matrix with sharp interfaces or Si-nanocrystals (ncs) embedded into single-crystalline oxide layer. As an example, we demonstrate the growth of Si buried in Gd2O3 and the incorporation of epitaxial Si clusters into single-crystalline Gd2O3 on silicon as well as silicon carbide substrates using molecular beam epitaxy. The leakage current of the obtained nanostructures exhibited negative differential resistance at lower temperatures. For structures containing Si-ncs a large hysteresis in capacitance–voltage measurements due to charging and discharging of the Si-ncs was obtained.
Microelectronics Journal.
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ABSTRACT: We investigate molecular beam epitaxial overgrowth of Si template layers produced by different approaches on single-crystalline oxide grown on Si(111). Three approaches based on modified solid-phase epitaxy were found to be suitable for the subsequent Si epitaxial overgrowth. The crystalline quality and interface properties of single-crystalline silicon on single-crystalline oxide grown on Si(111) make the obtained structures suitable for silicon-on-insulator applications. First measurements of electrical properties of p-type samples indicate good electrical properties of the top Si layer. Supplemental investigations demonstrate that Si layers with thickness in the range of 10 nm remain stable during thermal annealing up to 900 °C in an ultra-high vacuum.
Thin Solid Films.
