Phonon scattering from substitutional impurities and lattice defects in cadmium sulfide
Moore, Glenn Ellis
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/25748
Description
Title
Phonon scattering from substitutional impurities and lattice defects in cadmium sulfide
Author(s)
Moore, Glenn Ellis
Issue Date
1968
Doctoral Committee Chair(s)
Klein, Miles V.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Date of Ingest
2011-07-11T14:48:06Z
Keyword(s)
phonon scattering
substitutional impurities
lattice defects
cadmium sulfide
thermal conductivity
Language
en
Abstract
"The thermal conductivity as a function of temperature has been
measured from 1.4°K to 80 0K for doped and pure cadmium sulfide single
crystals of the wurtzite structure. The crystals were grown by a modified
Bridgeman technique under 100 atmospheres of argon at 1100°C by the
Eagle Picher Corporation.
The experimental results for the pure crystals indicate the heat
flow is isotropic in the crystal; the thermal conductivity parallel to
the c-axis is identical to the conductivity perpendicular to the c-axis.
It is also found that etching the crystals in HC1 gives a ""perfectly
rough"" surface for boundary scattering of phonons.
A theoretical analysis utilizing the Debye thermal conductivity
integral was successfully applied to the data for the pure crystal.
Coefficients derived from computer fits to the data agree with those
calculated from theoretical phonon scattering rates.
Isoe1ectronic, substitutional impurities (Co, Mn, Ni, Se, and Zn)
were introduced in the melt in concentrations up to 500 ppm. A Debye fit,
using only enhanced point defect scattering, to the thermal conductivity
data for the doped crystals works well except at the lowest temperatures.
To match the low temperature data it was necessary to include a term Ym
in the inverse of the phonon relaxation time.
It i$ suggested that lattice imperfections, in particular dislocations,
may cause the low temperature depression of the thermal conductivity.
Theoretical studies by Klemens, Carruthers, and Ohashi of phonon
scattering by dislocations were compared and the re5lUlts applied to
cadmium sulfide. Dislocation densities determined from etch pit counts
on the doped crystals were a factor of 10 lower than those predicted by
the above theories and computer fits to the data.
Phonon scattering by magnetic levels of the transition metal
dopants (Co, Mn, and Ni) was also considered. The low temperature
depression of the thermal conductivity of the 500 ppm Co-doped sample may
be due to the splitting of the magnetic energy levels in the cobalt ion
by the electric field of the cadmium sulfide lattice. Magnetic level
scattering was not detected in the Mn-and Ni-doped crystals.
Heat treatments were used to study the effects of stoichiometry
and electronic compensation on the thermal conductivity of the pure and
doped samples. Heating in flowing argon does not change the electrical
or thermal conductivity of the sample. It is postulated that this
indicates the crystals are stoichiometric. Heating the samples in a
sealed sulfur atmosphere induces photoconductivity but has no effect on
the thermal conductivity."
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
