Elektronske i optičke osobine deformisanih grafitnih i helikalnih nanotuba
Electronic and optical properties of defformed graphitic and helical nanobutes
Author
Dmitrović, Saša S.
Mentor
Milošević, Ivanka
Committee members
Damnjanović, Milan
Radović, Zoran
Popović, Zoran V.

Metadata
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Motivacija
U ovoj tezi su prezentovani rezultati iscrpne analize elektronskih i optičkih osobina
dva tipa ugljeničnih nanotuba. Prvi deo se odnosi na homogeno deformisane
jednoslojne ugljenične nanotube (tj. grafitne nanotube), dok su u drugom delu
rezultati za nedeformisane i podužno istegnute helikalne ugljenične nanotube. Konfiguracije
nedeformisanih grafitnih nanotuba su dobro poznate: sa izuzetkom tuba
jako malog dijametra, odgovara grafenskoj ravni urolovanoj na specifičan način. Sa
druge strane, možemo smatrati da su helikalne nanotube rezultat periodičnog umetanja
sedmougaonih i petougaonih defekata u grafensku rešetku, što prouzrokuje
njihovu karakterističnu helikalnu morfologiju. Od svih nanomaterijala baziranih na
ugljeniku ove nanotube imaju najsloženiju i najraznovrsniju strukturu. Pored tri
”globalna” geometrijska parametra, koje je moguće direktno meriti u ogledima, postoje
i ”lokalni” parametari koji opisuju položaj defekata unutar monomera. Zbog
toga se kod ovog tipa t...uba očekuju i raznovrsnije elektronske osobine. U tezi je
razmotren uticaj globalnih i lokalnih parametara, kao i moguće modifikacije elektronskih
osobina pomoću mehaničkih napona.
Kod nanotuba efekti deformacionog sprezanja na fizičke osobine nisu do sada
sistematski analizirane. Za uspešnu primenu u različitim nano-elektromehaničkim
uređajima detalno poznavanje efekata deformacionog sprezanja je od velike važnosti.
Tendencija smanjivanja mehaničkih i elektronskih uređaja ka nanometarskoj skali,
nameće potrebu za izradom efikasnih senzora za merenje i kontrolu ponašanja odgovaraju
ćih nanouređaja. Postojeće mikrosenzore je nemoguće skalirati na nanodimenzije,
a da ne dođe do drastičnog smanjenja dinamičkog opsega senzora. U
cilju prevazilaženja prepreke nametnute skaliranjem 3D materijala, potrebno je razmotriti
mogućnosti primene inherentnih 2D materijala, posebno onih baziranih na
kompozitnim filmovima od grafitnih nanotuba kod kojih efekti skaliranja daleko
manje utiču na promenu karakteristika...
Motivation
Results of the comprehensive study of electronic and optical properties of two
types of carbon nanotubes are presented in this thesis. First part considers homogenously
deformed single-wall carbon nanotubes(i.e. graphitic nanotubes), while
the second one contains results for non-deformed and uniaxially strained helically
coiled carbon nanotubes. Configurations of non-deformed single-wall carbon nanotubes
are well known: with exception of extremely narrow tubes, it corresponds to
specifically rolled up graphene plane. On the other hand, helically coiled carbon
nanotubes can be understand as the result of periodic insertion of heptagonal and
pentagonal defects in graphene lattice which results in their characteristic helical
morphology. Among all carbon based nanomaterials, these tubes have the most
complex and most diverse structures. Besides three ”global” geometric parameters
of helical coil, which can be directly measured in experiments, there are a number of
”local” param...eters that describe position of defects within the monomer. Therefore,
more diverse electronic properties are expected for these type of tubes. Influence
of global and local parameters and possible modification of electronic properties by
mechanical stress are addressed in this research study.
For the nanotubes effects of strain coupling on its physical properties has not been
systematically analyzed. For successful application in various nano-electromechanical
devices, detailed knowledge of effects of strain coupling on electronic and optical
properties are of the most importance. The tendency of decreasing mechanical and
electronic devices to the nanometer scale, imposes need to develop effective sensors
to measure and control the behavior of various nanodevices. However, without a
drastic reduction of the basic characteristics of the existing micro-sensors it is impossible
to scale them down to nanodimension. In order to overcome the barriers
imposed by scaling of 3D materials, it is necessary to consider the possible application
of inherent 2D materials, especially those based on composite films of carbon
nanotubes where the change in characteristics are far less affected by scaling...