Study on MBE technologies and optical properties of novel optical functional GeC/Si thin -epitaxial films and nanocrystal assemblies.

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As an aim at Si-compatible light emitting or quantum information devices, we have developed new nanotechnologies of forming precisely 2-D nano-crystal (NC) assemblies of GeC, β-FeSi_2 or Si on Si (100) substrates by fusing unique bottom-up-type and top-down-type nanotechnologies such as molecular beam epitaxy (MBE), solid phase epitaxy (SPE) or ion-implantation method, respectively. The microscopic structural and optical properties of their NC assemblies were evaluated. The brief results of this research project are as follows;(1) For the fused nanotechnology, a novel 'nanomask' of an ultra-thin (〜2 nm thick) Si film with 2D-assembled via-holes 7±2 nm in diameter on a Si (100) wafer was developed by means of a self-assembled bio-nanoprocess using proteins 'ferritin'. It was used successfully for conventional MBE, SPE and low-energy ion-implantation techniques.(2) Through very small and almost 2D-ordered via-holes of the Si nanomask on the Si (100) substrate, very small-size and 2-D ass … More embled Ge_<1-x>C_x NCs were grown by solid-source MBE with an arc-plasma gun as a C molecular beam source. The MBE-grown Ge1_<-x>Cx NCs were obtained up to a substitutional C content of x=3.2%. In the photoluminescence (PL) spectra at 7K, a PL peak appeared around 1.3 μm due to the quantum confinement effect. We could not make clear the origin of the extremely large band bowing so far.(3) 2-D Si-NC assemblies in SiO_2 thin films were synthesized by using very-low-energy Si^+ ion-implantation (down to 0.6keV) and sequential annealing with a Nd:YAG pulsed laser. As a result, almost ordered Si-NC assemblies with very small and uniform size (3.0±0.3 nm in diameter) and inter-particle separation (5 to 6 nm) were obtained by the transcription of the Si nanomask pattern. The PL spectra of Si-NCs implanted at 0.6keV were observed with a peak of 2lleV and an FWHM of 78 nm.(4) Very smallsize and high-density β-FeSi_2 NC assemblies were formed on a Si (100) substrate using an embedded solid-phase epitaxy (SPE) and bio-nanoprocess with proteins 'ferritin' containing Fe_2O_3 cores 7 nm in diameter. The β-FeSi_2 NCs were grown by SPE at 500-800℃ for 1 hr in an ultra-high vacuum chamber after embedded in an amorphous Si thin film. The β-FeSi_2 NC assemblies were almost 2D-ordered with a uniform diameter 6.3±0.3 nm and a density 6.2×10^ (11) dots/cm^2, and their PL spectra with a peak 0.91 eV were obtained Less