Abstract:
Acoustic effects such as absorption/amplification of acoustic phonons,
Acoustoelectric Effect (AE) and Acoustomagnetoelectric Effect (AME) were
studied in Carbon Allotropes. In this thesis, the Carbon Allotropes considered
are Graphene Nanoribbon (GNR), 2-dimensional Graphene sheet, and Carbon
Nanotubes (CNT). The Boltzmann transport equation (BTE) and the phonon
kinetic equation (PKE) were used. All results were analysed numerically and
graphically presented. Using BTE for Armchair Graphene Nanoribbon
(AGNR), amplification of acoustic waves (G=G0) and acoustomagnetoelectric
field (Esame) were studied in the presence of an external electric and magnetic
fields. G=G0 and Esame were found to depend on the sub-band index (pi), the
nanoribbon width (N), and the dimensionless factor (h = Ωt).
Using the PKE, amplification (absorption) and AE in 2D graphene and Carbon
Nanotubes (CNTs) were studied. On hypersound amplification, a mechanism
due Cerenkov emission was employed where the ratio of the drift velocity (Vd)
to the velocity of sound (Vs) was considered. In both materials, the dependence
of amplification (absorption) on frequency (wq) were analysed. Here the
acoustic waves were considered as phonons in the hypersound regime. In CNT,
it was observed that the maximum amplification was attained as Vd = 1:1Vs
which occurred at E = 51:7 Vcm−1. For n = 2, (where n is an integer) the
absorption obtained qualitatively agree with an experimental measurement.
