Browsing by Author "Huang, Chang-Hsun"

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Dependence of the structure and orientation of VSS grown Si nanowires on an epitaxy process
(2019-08-07)
Chiang, Yi-Ting
;
Chou, Yi
;
Huang, Chang-Hsun
;
Lin, Wei-Ting
;
Chou, Yi-Chia
We investigated the vapor-solid-solid growth of Si nanowires from Ni silicides on Si(111), Si(110), and GaN substrates. The morphology and structures of Si on these substrates are distinct, and are dependent on substrate lattices and an epitaxy process during growth. The sidewall facets and epitaxy of silicides and Si were discussed. In addition, Si grown on GaN nanowires was investigated which led to the formation of branched nanowire structures. The Si nanowires/nanodots lie on the surface of GaN nanowires to maintain lower system energy. We manipulated the whole process in a UHV and studied the crystal growth of Si on different lattice substrates. Meanwhile, the process which occurred in a non-UHV led to less regularity on the NiSi2 crystal facets and interface epitaxy between NiSi2 and Si nanowires.
Structure and Strain Relaxation of GaN Nanorods Grown on Homoepitaxial Surface via Controlling Irregular Mask
(2019-02-07)
Huang, Chang-Hsun
;
Pakzad, Anahita
;
Lee, Wei-I
;
Chou, Yi-Chia
;
電子物理學系
We propose a simple and low-cost approach using irregular mask for growing GaN nanorods (NRs) bottom up on a freestanding GaN substrate through hydride vapor-phase epitaxy. The irregular mask consists of uncoalesced SiO2 islands deposited by plasma-enhanced chemical vapor deposition to isolate growth. The selection of the SiO2 amount is investigated to achieve reasonable NR density (high coverage), desired morphology (flat side walls and uniform diameters), and lattice quality (single crystalline; better quality than that of an as-grown layer under the same growth ambient). Using this growth approach with appropriate parameters, we successfully synthesize high coverage of uncoalesced NRs on a homoepitaxial surface in a short growth duration. The morphology, density, and growth rate are controlled by adjusting V/III ratios. The cathodoluminescence and photoluminescence measurements of GaN show that luminescence was obtained near 3.4 eV while the structure was grown with mask but contained defect signals when grown without mask. The residual strain relaxation within the GaN NRs has been confirmed using Raman spectrum and scanning transmission electron microscopy strain mapping. Moreover, we demonstrate the strain distribution between different crystalline qualities and lattice orientations in GaN NR The method provides a quick and inexpensive method for future nanofabrication consideration.