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|Title: ||Theoretical study of electronic and electrical properties of silicon nanowires|
|Other Titles: ||Na mi xi xian dian zi xue ji dian xue xing zhi de li lun yan jiu|
|Authors: ||Lu, Aijiang (陸愛江)|
|Department: ||Department of Physics and Materials Science|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2007|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Nanowires -- Electric properties.|
|Notes: ||xiii, 144 leaves : ill. (some col.) 30 cm.|
Thesis (Ph.D.)--City University of Hong Kong, 2007.
Includes bibliographical references.
CityU Call Number: TK7874.85 .L83 2007
|Abstract: ||Silicon nanowires (SiNWs) are attracting great interest as the most promising
building blocks for future nanoscale electronic devices. Remarkable development has
been achieved toward the goal of application of SiNWs in industry in the past
The small sizes of SiNWs make their electronic and electrical properties strongly
dependent on growth direction, size, morphology and surface reconstruction. A
well-known example is the size dependence of the electronic band gap width of
SiNWs irrespective of wire direction. As the wire diameter decreases, the band gap
of the nanowire widens and deviates from that of bulk silicon gradually. Moreover,
the orientation of the wire axis and the surface have a great effect on the electronic
properties of SiNWs. Further detailed deeper studies on the structural properties are
required to guide the research and application of these nanomaterials.
In this work, systematic studies on the electronic and electrical properties of
SiNWs along different orientations were conducted based on density functional
theoretical (DFT) calculations. Interesting findings include:
(1) Orientation dependences of electronic band structures of hydrogen-terminated
silicon atomic chains: A <110> oriented Si chain showed direct band gap while a
<112> chain showed indirect band gap. In addition, the validity of DFT method was
confirmed by performing additional GW calculations on these chains. (2) Unique, tunable electronic band structures of hydrogen-terminated <112>
SiNWs: It was shown that the hydrogen-terminated <112> SiNWs kept an indirect
gap feature even at extremely small size. Interestingly, the indirect gap of <112>
SiNWs could be tuned to direct gap, through changing the cross section shape.
(3) Effects of adsorption and doping of a single boron atom in <112> SiNWs:
Although the single boron atom doping in <112> SiNWs showed slight influence on
the band structure modification, the atomic adsorption could change the band
structure remarkably. Moreover, different adsorbents modified the electronic
properties of SiNWs differently, with the electronegative value acting as an index to
show the extent of the influence.
(4) Band gap of hydrogen-terminated <112> SiNWs tuned through axial stress:
Through structural deformation, the electronic band structure of SiNWs could be
tuned. It was found that compression facilitated the indirect-direct gap mutation of
<112> wires while extension induced the direct gaps of <110> and <111>wires.
(5) Orientation dependence of transport properties of <112> SiNWs: While
<111> SiNWs are semiconductor-like, <112> SiNWs show characteristics of
conductors. Furthermore, there is a size requirement of both the electrodes and the
conductors placed between the electrodes.
It is expected that this thesis work would be helpful for understanding of both
the electronic and electrical properties of SiNWs and provide experimental guidance
in materials applications.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b2268765|
|Appears in Collections:||AP - Doctor of Philosophy |
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