38,190 research outputs found
Pulsed PECVD growth of silicon nanowires on various substrates
Silicon nanowires with high aspect ratio were grown using PPECVD and a gold catalyst on a variety of different substrates. The morphology of the nanowires was investigated for a range of crystalline silicon, glass, metal, ITO coated and amorphous silicon coated glass substrates. Deposition of the nanowires was carried out in a parallel plate PECVD chamber modified for PPECVD using a 1kHz square wave to modulate the 13.56MHz RF signal. Samples were analyzed using either a Phillips XL20 SEM of a ZEISS 1555 VP FESEM. The average diameter of the nanowires was found to be independent of the substrate used. The silicon nanowires would grow on all of the substrates tested, however the density varied greatly. It was found that nanowires grew with higher density on the ITO coated glass substrates rather than the uncoated glass substrates. Aligned nanowire growth was observed on polished copper substrates. Of all the substrates trialed, ITO coated aluminosilicate glass proved to be the most effective substrate for the growth of silicon nanowires
Integrated Freestanding Single-Crystal Silicon Nanowires: Conductivity and Surface Treatment
Integrated freestanding single-crystal silicon nanowires with typical dimension of 100 nm × 100 nm × 5 µm are fabricated by conventional 1:1 optical lithography and wet chemical silicon etching. The fabrication procedure can lead to wafer-scale integration of silicon nanowires in arrays. The measured electrical transport characteristics of the silicon nanowires covered with/without SiO2 support a model of Fermi level pinning near the conduction band. The I–V curves of the nanowires reveal a current carrier polarity reversal depending on Si–SiO2 and Si–H bonds on the nanowire surface
Directed deposition of silicon nanowires using neopentasilane as precursor and gold as catalyst
In this work the applicability of neopentasilane (Si(SiH3)4) as a precursor for the formation of silicon nanowires by using gold nanoparticles as a catalyst has been explored. The growth proceeds via the formation of liquid gold/silicon alloy droplets, which excrete the silicon nanowires upon continued decomposition of the precursor. This mechanism determines the diameter of the Si nanowires. Different sources for the gold nanoparticles have been tested: the spontaneous dewetting of gold films, thermally annealed gold films, deposition of preformed gold nanoparticles, and the use of “liquid bright gold”, a material historically used for the gilding of porcelain and glass. The latter does not only form gold nanoparticles when deposited as a thin film and thermally annealed, but can also be patterned by using UV irradiation, providing access to laterally structured layers of silicon nanowires
Modulation of Thermal Conductivity in Kinked Silicon Nanowires: Phonon Interchanging and Pinching Effects
We perform molecular dynamics simulations to investigate the reduction of the
thermal conductivity by kinks in silicon nanowires. The reduction percentage
can be as high as 70% at room temperature. The temperature dependence of the
reduction is also calculated. By calculating phonon polarization vectors, two
mechanisms are found to be responsible for the reduced thermal conductivity:
(1) the interchanging effect between the longitudinal and transverse phonon
modes and (2) the pinching effect, i.e a new type of localization, for the
twisting and transverse phonon modes in the kinked silicon nanowires. Our work
demonstrates that the phonon interchanging and pinching effects, induced by
kinking, are brand new and effective ways in modulating heat transfer in
nanowires, which enables the kinked silicon nanowires to be a promising
candidate for thermoelectric materials.Comment: Nano. Lett. accepted (2013
Understanding of the Retarded Oxidation Effects in Silicon Nanostructures
In-depth understanding of the retarded oxidation phenomenon observed during
the oxidation of silicon nanostructures is proposed. The wet thermal oxidation
of various silicon nanostructures such as nanobeams, concave/convex nanorings
and nanowires exhibits an extremely different and complex behavior. Such
effects have been investigated by the modeling of the mechanical stress
generated during the oxidation process explaining the retarded regime. The
model describes the oxidation kinetics of silicon nanowires down to a few
nanometers while predicting reasonable and physical stress levels at the
Si/SiO interface by correctly taking into account the relaxation effects
in silicon oxide through plastic flow
The impacts of surface conditions on the vapor-liquid-solid growth of germanium nanowires on Si (100) substrate
The impacts of surface conditions on the growth of Ge nanowires on a Si (100) substrate are discussed in detail. On SiO2-terminated Si substrates, high-density Ge nanowires can be easily grown. However, on H-terminated Si substrates, growing Ge nanowires is more complex. The silicon migration and the formation of a native SiO2 overlayer on a catalyst surface retard the growth of Ge nanowires. After removing this overlayer in the HF solution, high-density and well-ordered Ge nanowires are grown. Ge nanowires cross vertically and form two sets of parallel nanowires. It is found that nanowires grew along ?110? direction
Theoretical Study of Carbon Clusters in Silicon Carbide Nanowires
Using first-principles methods we performed a theoretical study of carbon
clusters in silicon carbide nanowires. We examined small clusters with carbon
interstitials and antisites in hydrogen-passivated SiC nanowires growth along
the [100] and [111] directions. The formation energies of these clusters were
calculated as a function of the carbon concentration. We verified that the
energetic stability of the carbon defects in SiC nanowires depends strongly on
the composition of the nanowire surface: the energetically most favorable
configuration in carbon-coated [100] SiC nanowire is not expected to occur in
silicon-coated [100] SiC nanowire. The binding energies of some aggregates were
also obtained, and they indicate that the formation of carbon clusters in SiC
nanowires is energetically favored.Comment: 6 pages, 5 figures; 8 pages,
http://www.hindawi.com/journals/jnt/2011/203423
Measurement of thermal conductance of silicon nanowires at low temperature
We have performed thermal conductance measurements on individual single
crystalline silicon suspended nanowires. The nanowires (130 nm thick and 200 nm
wide) are fabricated by e-beam lithography and suspended between two separated
pads on Silicon On Insulator (SOI) substrate. We measure the thermal
conductance of the phonon wave guide by the 3 method. The cross-section
of the nanowire approaches the dominant phonon wavelength in silicon which is
of the order of 100 nm at 1K. Above 1.3K the conductance behaves as T3, but a
deviation is measured at the lowest temperature which can be attributed to the
reduced geometry
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