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A strain-relieved, dislocation-free InxGa1−xAs layer is selectively grown on nanoscale SiO2-patterned GaAs(001) by molecular beam epitaxy. By localizing the epitaxial area to a periodic array of nanoscale circular holes opened in a SiO2 mask and allowing the InxGa1−xAs epilayers selectively grown on adjacent holes to coalesce over the SiO2 mask by lateral overgrowth, the strain of the resulting InxGa1−xAs layer (x=0.06) is relieved with a dramatically decreased generation of misfit dislocations. These experimental results qualitatively support the basic idea of the Luryi-Suhir proposal [Appl. Phys. Lett. 49, 140 (1986)].

We demonstrate that high-quality Ge can be grown on Si covered with a thin layer of chemical SiO2. When the oxidized Si substrate is exposed to Ge molecular beam, 7-nm-wide seed pads form in the oxide layer and “touchdown” on the underlying Si. Upon continued exposure, Ge selectively grows on the seed pads rather than on SiO2, and the seeds coalesce to form an epitaxial lateral overgrowth (ELO) layer. The Ge ELO layer is characterized by transmission electron microscopy and etch-pit density (EPD). The Ge ELO layer is free of dislocation network, but stacking faults exist near the Ge-SiO2 interface. A fraction of these stacking faults propagate to the surface, resulting in EPD less than 2×106cm−2. The high quality Ge ELO layer is attributed to a high density of nanoscale Ge seed pads interspaced by 2–12-nm-wide SiO2 patches.

We demonstrate that Ge can be selectively grown on Si(100) through openings in a SiO2 nanotemplate by solid source molecular beam epitaxy. The selectivity relies on the thermal instability of GeO and SiO near 650 °C. Ge islands grow in the template windows and coalesce on top of the template, forming an epitaxial lateral overgrowth (ELO) layer. Cross-sectional transmission electron microscopy images show that the Ge seeds and the ELO layer are free of threading dislocations. Only stacking faults are generated but terminate within 70 nm of the Ge–Si interface, while twins along {111} planes are observed in the ELO layer. The threading-dislocation-free Ge seeds and ELO layer are attributed to epitaxial necking as well as Ge–Si intermixing at the interface.

The incorporation of In on the non-polar, piezoelectric-free (001) facet of cubic (c-) GaN epitaxially grown over a Si(001) substrate by metal-organic vapor phase epitaxy is reported. Relying on a hexagonal (h-) to c-phase transformation during epitaxy on an 800 nm-wide, Si(111)-faceted v-groove patterned into the substrate, the GaN epilayer at cross sectional view retains a triangular c-phase inside a chevron-shaped h-phase that results in a top surface bounded by a (001) facet parallel to Si(001) at the center and ( 11¯01) facets at both edges. A stack of five, ∼3 nm-thick, InxGa1−xN/GaN quantum wells (QWs) was deposited on the double-phased top surface. The c-phase region up to the QWs keeps extremely small misfit (∼0.002) to the fully relaxed h-GaN underneath it and is in tensile stress implying undefected by the h-c phase interface. The In incorporation on a strained non-polar (001) of c-GaN is comparable with that on totally relaxed semi-polar ( 11¯01) of h-GaN without noticeable adatom migration ac...

GaInN/GaN light-emitting diodes free of piezoelectric polarization were prepared on standard electronic-grade Si(100) substrates. Micro-stripes of GaN and GaInN/GaN quantum wells in the cubic crystal structure were grown on intersecting {111} planes of microscale V-grooved Si in metal-organic vapor phase epitaxy, covering over 50% of the wafer surface area. Crystal phases were identified in electron back-scattering diffraction. A cross-sectional analysis reveals a cubic structure virtually free of line defects. Electroluminescence over 20 to 100 μA is found fixed at 487 nm (peak), 516 nm (dominant). Such structures therefore should allow higher efficiency, wavelength-stable light emitters throughout the visible spectrum.

We report the fabrication of TiO2 nanostructures with lithographically defined templates. Interferomeric-lithography was used to define soft templates (polymer posts), and a sol-gel solution was deposited on a patterned surface. In the final step, calcination was employed to form uniform low aspect-ratio crystalline nonclose-packed TiO2 nanotube arrays over a large area. Similarly, nanotree arrays and parallel nanotunnels were prepared as well. The position and morphology of TiO2 nanostructures were well controlled. These TiO2 nanostructures have a potential technological importance in clean energy, biosensor, and drug release.

Domain-switching in BaTiO3 single crystal under an antiparallel electric field was investigated in this paper by polarized light microscope. It was found that 180° domain-switching consisted of two 90° switching steps. The polarization reversal of domains took place when an antiparallel electric field was applied to the BaTiO3 single crystal. The domain-switching process was different under different field intensities. Under a low field, all domains switched 180° through two 90° domain-switching steps. However, under a high field, only some 90° domains were nucleated in the initial period and subsequently all domains switched to the direction of the external field quickly.

In [Pt(5A)∕Co(tCoA)]3∕NiO(11A)∕[Co(tCoA)∕Pt(5A)]3 multilayers, the out-of-plane antiferromagnetic interlayer coupling between the Co∕Pt multilayers can be tailored via varying the Co layer thickness tCo. The coupling strength increases with increase of tCo, but after reaching a maximum at tCo=4.5A, it decreases with further increase of tCo. At tCo>6A, no out-of-plane antiferromagnetic interlayer coupling has been observed. This nonmonotonic dependence on tCo of the coupling strength can be attributed to variation of the out-of-plane effective magnetic anisotropy in Co∕Pt multilayers with tCo.

Nanoscale patterned growth of GaAs on Si(111) by molecular beam epitaxy is examined. A 355 nm period two-dimensional array of circular holes (diameter ∼200–250nm) is fabricated into a 45-nm-thick SiO2 film on a Si(111) substrate by large-area interferometric lithography and dry etching. For 300 nm deposition, the GaAs epilayer selectively deposited within each hole on the patterned substrate is surrounded by {11¯0}-type sidewalls perpendicular to Si(111), resulting in a hexagon-based prismatic pillar, without significant lateral overgrowth. At the initial stage of growth, twins parallel to Si(111) and an aperiodic mixture of cubic and hexagonal phases are observed but most of the GaAs pillars are terminated with a cubic phase region. Raman scattering reveals that the individual nanoscale GaAs pillars are completely strain relaxed.