|
|
CityU Institutional Repository >
Outstanding Academic Papers by Students >
OAPS - Dept. of Physics & Materials Science >
Please use this identifier to cite or link to this item:
http://hdl.handle.net/2031/3778
|
| Title: | Synthesis of oriented silicon nanowires by applying bias voltage |
| Authors: | Chau, Penny Chin Yiu (周展耀) |
| Department: | Department of Physics and Materials Science |
| Issue Date: | 2005 |
| Course: | AP4116 |
| Programme: | BEng (Hons) in Materials Engineering 2004-05 |
| Supervisor: | Prof. S T Lee |
| Subjects: | Nanowires
Silicon
Nanostructure materials
Nanotechnology |
| Abstract: | An electric field is supposed to play a major role in the formation of silicon nanowires by
Oxide-Assisted Growth mechanism. The strong electric field is assumed at the tip of
silicon nanowires. Most of the Silicon-oxide molecules are attracted by this E-field and
then land on the tip of the wire. Therefore, the nanowires growth only occurs on the tip.
Based on this E-field mechanism premise, we hypothesize that, if the formation of silicon
nanowires is related to its emitted E-field feature, growth orientation and speed of the
nanowires can be altered by applying bias voltage (i.e. external E-field). The basic
concept is that a bias voltage is applied to attract the more charges to accumulate on the
particular area of the tip, so that it will accelerate the growth process. If we change the
direction of the external E-field, the growth direction of the nanowires can be altered to
go where we want. Meanwhile, we can synthesize the aligned nanowires.
In our course of experiment, hot filament CVD (chemical vapor deposition) was mainly
used. Additionally, a plate of stainless steel was installed to act as an electrode which
applies bias voltage. A silicon substrate coated with gold was the place for the growth of
silicon nanowires. By vaporizing the starting source - silicon monoxide, the nanowires
can be formed on the heated substrate. During the formation of the nanowires, the
external E-field was applied. As a result, it can be found that the growth orientation of
nanowires can really be altered by the external E-field. However, because of the silicon
nanowires carrying charges feature, the nanowires were easily tangled. Therefore, it is so
difficult to align a large population of the nanowires. In order to prevent from the
VIII
nanowires from being tangled, the metal catalyst should be fine enough. This is because,
if the distance between each of the nanowires is large enough, they would not cross and
attach to each other. At the same time, it can maximize the effect of the external electric
field. An oriented growth direction can be significantly shown.
Different kinds of gold deposition method were used. It has been found that gold pattern
made by electron beam lithography can really show that the growth orientation of silicon
nanowires is affected by the electric field. Since positive and negative bias voltages give
the same effect on the growth orientation, it is reasonable to believe that the silicon
nanowire is an induced dipole. As a consequence, under the electric field, an electrostatic
force continuously pulls the head of the nanowire, so that it becomes oriented and
relatively straight. |
| URI: | http://hdl.handle.net/2031/3778 |
| Appears in Collections: | OAPS - Dept. of Physics & Materials Science
|
Files in This Item:
| File |
Size | Format |
|---|
| fulltext.html | 0Kb | HTML | View/Open |
|
Items in CityU IR are protected by copyright, with all rights reserved, unless otherwise indicated.
|
