Search

Investigations of the structural properties of ultrasmall Ge dots, grown through a thin silicon oxide layer on Si(001), have been performed by combining (i) grazing incidence x-ray diffraction, (ii) grazing incidence small angle x-ray scattering (GISAXS), and (iii) surface extended x-ray absorption fine structure (SEXAFS). Grazing incidence x-ray diffraction observations show that the dots are highly strained to the Si(001) substrate. The dot shape and composition, as determined by GISAXS experiments and in situ SEXAFS, strongly depend on the thickness and the composition of the silicon oxide layer covering the surface of the silicon substrate. Ge dots grown through 1.2 nm thick SiO2 are round shaped with a Ge content of about 60% whereas dots grown through 0.3 nm thick SiOx are facetted and composed of almost pure Ge. [ABSTRACT FROM AUTHOR]

We investigate the effects of the thickness reduction and specific postannealing treatments in order to improve the electrical properties of yttrium oxide-based metal-insulator-metal (MIM) capacitors. The films were grown on Si/TiSi2/TiN substrates at 350 °C by a low temperature process (pulsed liquid injection plasma-enhanced metal organic chemical vapor deposition). Although the thickness reduction leads to an increase of the capacitance density, the other electrical characteristics (the voltage linearity, the leakage currents, and the voltage breakdown) are seriously deteriorated due to the augmentation of the electric field. Low thermal budget annealing posttreatments (<=450 °C) were carried out in a gas flux (Ar, O2, and H2) and under an ultraviolet (UV) radiation (O2 and N2). We demonstrate that the UV-O2 annealing treatment is particularly efficient in improving the voltage linearity, the leakage currents, and the electric field breakdown. The improved electrical properties after the UV-O2 annealing can be related to chemical modifications (organic content reduction and oxygen content increase). The voltage linearity improvement is most likely due to the presence of a residual oxidized silicon ultrathin layer on the top surface of the yttrium oxide films. Thus, a UV-O2 annealing is an effective postdeposition treatment that is compatible with the low thermal budget, which is required for MIM applications. [ABSTRACT FROM AUTHOR]

Structural properties of high density, nanometric size germanium dots grown on a silicon (001) surface covered by a very thin (1.2 nm thick) silicon oxide layer have been investigated by in-situ grazing incidence x-ray diffraction (GIXD) and ex-situ atomic force microscopy. Growth under molecular nitrogen partial pressure of 10-5 Torr yielded a high density (∼4×1010/cm2) of dots. The dot size can be progressively increased by successive depositions of germanium. GIXD investigations show that dots grow in epitaxial relationship to the silicon (001) substrate and that after few successive depositions, the dots are composed of pure and fully relaxed germanium. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We show that germanium dots can be directly grown by molecular beam epitaxy on a silicon (001) surface covered by a very thin (1.5 nm thick) silicon nitride layer. We describe the experimental procedure, which induces the growth of nano-metric size, isolated germanium dots. The germanium dots are in epitaxy with the silicon substrate. Using grazing incidence x-ray diffraction we show that for very small dots the in-plane lattice parameter inside the dots is very close to the silicon lattice parameter while a strong lattice relaxation and/or silicon inter-diffusion take place with increasing dot size. [ABSTRACT FROM AUTHOR]

We show that germanium dots can be directly grown by molecular beam epitaxy (MBE) on a silicon (001) surface covered by a thin (1.2-nm-thick) thermal silicon oxide layer. We describe the experimental procedure, which induces the growth of a high density (10[sup 11]/cm[sup 2]) of nanometric germanium dots on silicon oxide. Germanium dots grown by MBE exhibit an epitaxial relationship with the underlying silicon substrate. We show that despite the presence of the thin silicon oxide layer, the silicon grown to embed the germanium dots is also single crystal in epitaxy with the silicon substrate. Nanometric size high-density crystalline inclusions in silicon oxide, seen in high-resolution transmission electron microscopy observations, are tentatively proposed as nucleation seeds for germanium dots and silicon lateral overgrowth on silicon oxide. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Ge growth on SiC(0 0 0 1) follows a Stranski–Krastanov mode for Si-rich (3×3) and (√ of 3×√ of 3)R30° reconstructed surfaces. For Ge deposit in particular temperature conditions, a new (4×4) superstructure takes place and the reflection high energy electron diffraction (RHEED) specular spot intensity presents one oscillation proving a wetting layer formation. An island nucleation is then ascertained by the oscillation vanishing and by the appearance of a k⊥-modulated RHEED pattern. On the other hand, on a (6√ of 3×6√ of 3)R30° C-rich surface, a direct Ge island nucleation is observed from the first growth stage. Indeed, for 1 ML Ge, the RHEED diagram consists in spots and rings, and the atomic force microscopy analysis indicates a high density (∼8×1010 cm-2) of small islands (∅∼30 nm, h∼3 nm). The RHEED spot analysis shows a preferential epitaxial relationship with the substrate Ge(1 1 1)//SiC(0 0 0 1). The Ge–C bonding being energetically unfavourable, Ge tends to form islands immediately rather than wetting the graphite-terminated surface. The Ge growth mode on C-rich surface is thus of Volmer–Weber type. [Copyright &y& Elsevier]