Effects of Temperature and Ultrasound on Nucleation Behavior during Electrochemical Synthesis of Copper Thin Films

By: Mallik, ArchanaContributor(s): Ray, Bankim Chandra [Supervisor] | Mohanty, Upendra Kumar [Supervisor] | Department of Metallurgical and Material ScienceMaterial type: TextTextLanguage: English Publisher: 2010Description: 138 pSubject(s): Engineering and Technology | Metallurgical and Materials Science | Nanotechnology | Thin Flims | Electrochemical SysthesisOnline resources: Click here to access online Dissertation note: Thesis (Ph.D)- National Institute of Technology, Rourkela Summary: Temperature is an excellent tool for tuning the phase formation kinetics and hence structure and properties of synthesized materials. The effect of the said parameter with adde d sonication impact on the electrochemical synthesis of copper thin films has been investigated in the present study. Copper was electroplated on graphite and aluminum substrates from a simple aqueous binary sulfate electrolyte at sub-ambient temperatures in presence of an ultr asonic horn of 20 KHz frequenc y and 20% output of the total power. The prepared films were characterized by X-ray diffraction and electron microscopic methods i.e. atomic force microscopy (AFM) and sc anning electron microscopy (SEM). Reaction kinetics and nucleation mechanism of film formation was investigated by cyclic voltammetry and chrono- amperometry. Mechanical properties and thermal stabilit y of the films were analyzed by nano-indentation and differential scanning calorimetry. The X-ray diffraction analysis and microscopic stud ies indicate nano-range deposits with decreasing reaction temperature in both silent and sonicati on conditions. Crystallinity of both the deposits was confirmed by the sharp XRD peaks. Synthesis under sile nt conditions had lead to many crystallographic defects as observed by the large peak shifts of X-RD patterns. However, deposits were dendritic powdery and highly scattered in nature in s ilent conditions. Ultrasound was found to have a significant effect on the deposit morphology. The deposit obtained was comp act, uniform and adherent. Energy dispersive spectroscopy result of the deposits revealed an oxidi zed silent deposit along with some adsorbed sulfur onto the electrode surface. In contrary the in-situ cleaning associated with sonication has resulted in cleaner deposits. Correlating the morphological investigations (by SE M and AFM) with cyclic voltammetry (CV) and chronoamperometry (CA), the mechanism and kine tics of ultrasound assisted low temperature copper elctrocrystallization has been tried to be portrayed . The results indicate that ultrasound induces secondary nucleation by breaking of the existing primary nuclei in addition to the primary nucleation. The new understanding of the sonoelectrochemical mechanisms clarifies few unclear issues. It could possibly allow for the better design of sonoelectrochemical s ynthesis. Furthermore it was found that the deposition of copper in the absence of ultrasound had mixed mass and charge transfer kinetics. Copper nucleated according to 3D instantaneous mechan isms for all temperature ranges. The extent of nucleation was found to be increased at low temperatur es with a transition of dendritic type morphology to spherical copper deposition. On the other hand, the deposition kinetics was mainly dominated by charge transfer in presence of ultrasound. Diffusion coefficients and nuc lei population density were calculated for each temperature range for both presence and absence of u ltrasound, both the quantities increased in presence of ultrasound. Sonicated deposits with good surface coverage were found to c onsist of spherical copper agglomerates of nanosized particles. The results suggest that the effect of power ultrasound on electrochemical systems under a wide range of conditions is non-conventional. The ex-situ growth kinetics of low temperature sono-el ectrochemically deposited Cu thin films has been studied under non-isothermal conditions using a diff erential scanning calorimetric (DSC) technique. The analysis focuses on the effect of deposition temperat ure on the DSC results. The grain growth mechanism and mode were discussed by determining the variation of the activation and surface energies of the films. v The kinetic observations were then correlated with the morphological evolution of the films using scanning electron microscopy and atomic force micro scopy. The results suggest a transition of abnormal growth to normal mode of growth behavior as the film synthesis temperature was reduced. Knowledge of internal stresses in thin copper film structures is essential in understanding the film properties, such as stress migration, adhesion, hardness and elasticity. The variation of internal stresses and nano-mechanical properties were studied with decreasing deposition temperature of the films. Irrespective of deposition temperature, the stress was observed to be compressive and increased at low electrolyte temperatures. Hardness and elasticity of the films were found to be increased with reduced deposition temperature. With increasing compressive st ress, the hardness of the films increased. Hence, residual compressive stresses were expected to blunt crack tips and suppress crack propagation . The surface adhesion of the film deposited at 5 °C was minimum, indicating increased cleanliness and chemical stability with low deposition temperatures. The mechanism of electrodeposition of copper thin film on aluminum has been studied under the influence of power ultrasound using cyclic voltammetry . The deposited thin films were characterized by x-ray diffraction, scanning electron microscope and atomic force microscope. Films are crystalline in structure. The spherical copper domains of the de posits without sonication have been converted to mushroom structures in presence of ultrasound. Proper ties, including thermal and mechanical are further analyzed using differential scanning calorimeter and nano-indentation. The films were comparatively stable than the graphite coated films. Further the soft films are found to have good wear properties.
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Thesis (Ph.D)- National Institute of Technology, Rourkela

Temperature is an excellent tool for tuning the phase formation kinetics and hence structure and
properties of synthesized materials. The effect of
the said parameter with adde
d sonication impact on the
electrochemical synthesis of copper thin films has
been investigated in the present study. Copper was
electroplated on graphite and aluminum substrates from
a simple aqueous binary sulfate electrolyte at
sub-ambient temperatures in presence of an ultr
asonic horn of 20 KHz frequenc
y and 20% output of the
total power. The prepared films were characterized by X-ray diffraction and electron microscopic
methods i.e. atomic force microscopy (AFM) and sc
anning electron microscopy (SEM). Reaction kinetics
and nucleation mechanism of film formation was
investigated by cyclic voltammetry and chrono-
amperometry. Mechanical properties and thermal stabilit
y of the films were analyzed by nano-indentation
and differential scanning calorimetry.
The X-ray diffraction analysis and microscopic stud
ies indicate nano-range deposits with decreasing
reaction temperature in both silent and sonicati
on conditions. Crystallinity of both the deposits was
confirmed by the sharp XRD peaks. Synthesis under sile
nt conditions had lead to many crystallographic
defects as observed by the large peak shifts of X-RD
patterns. However, deposits
were dendritic powdery
and highly scattered in nature in s
ilent conditions. Ultrasound was found to
have a significant effect on
the deposit morphology. The deposit obtained was comp
act, uniform and adherent. Energy dispersive
spectroscopy result of the deposits revealed an oxidi
zed silent deposit along with some adsorbed sulfur
onto the electrode surface. In contrary the in-situ
cleaning associated with sonication has resulted in
cleaner deposits.
Correlating the morphological investigations (by SE
M and AFM) with cyclic voltammetry (CV) and
chronoamperometry (CA), the mechanism and kine
tics of ultrasound assisted low temperature copper
elctrocrystallization has been tried to be portrayed
. The results indicate that ultrasound induces secondary
nucleation by breaking of the existing primary nuclei
in addition to the primary nucleation. The new
understanding of the sonoelectrochemical mechanisms
clarifies few unclear issues. It could possibly
allow for the better design of sonoelectrochemical s
ynthesis. Furthermore it was found that the deposition
of copper in the absence of ultrasound had mixed mass
and charge transfer kinetics. Copper nucleated
according to 3D instantaneous mechan
isms for all temperature ranges. The extent of nucleation was found
to be increased at low temperatur
es with a transition of dendritic type morphology to spherical copper
deposition. On the other hand, the deposition kinetics
was mainly dominated by charge transfer in
presence of ultrasound. Diffusion coefficients and nuc
lei population density were calculated for each
temperature range for both presence and absence of u
ltrasound, both the quantities increased in presence
of ultrasound. Sonicated deposits with good surface
coverage were found to c
onsist of spherical copper
agglomerates of nanosized particles. The results
suggest that the effect of power ultrasound on
electrochemical systems under a wide range
of conditions is non-conventional.
The ex-situ growth kinetics of low temperature sono-el
ectrochemically deposited
Cu thin films has been
studied under non-isothermal conditions using a diff
erential scanning calorimetric (DSC) technique. The
analysis focuses on the effect of deposition temperat
ure on the DSC results. The grain growth mechanism
and mode were discussed by determining the variation
of the activation and surface energies of the films.
v
The kinetic observations were then
correlated with the morphological evolution of the films using
scanning electron microscopy and atomic force micro
scopy. The results suggest a transition of abnormal
growth to normal mode of growth behavior as the film synthesis temperature was reduced.
Knowledge of internal stresses in thin copper film
structures is essential in understanding the film
properties, such as stress migration, adhesion, hardness
and elasticity. The variation of internal stresses
and nano-mechanical properties were studied with
decreasing deposition temperature of the films.
Irrespective of deposition temperature, the stress was
observed to be compressive and increased at low
electrolyte temperatures. Hardness and elasticity of
the films were found to be increased with reduced
deposition temperature. With increasing compressive st
ress, the hardness of the films increased. Hence,
residual compressive stresses were expected to
blunt crack tips and suppress crack propagation
. The
surface adhesion of the film deposited at 5 °C was minimum, indicating increased cleanliness and
chemical stability with low deposition temperatures.
The mechanism of electrodeposition of copper thin
film on aluminum has been studied under the
influence of power ultrasound using cyclic voltammetry
. The deposited thin films were characterized by
x-ray diffraction, scanning electron microscope and
atomic force microscope. Films are crystalline in
structure. The spherical copper domains of the de
posits without sonication have been converted to
mushroom structures in presence of ultrasound. Proper
ties, including thermal and mechanical are further
analyzed using differential scanning calorimeter and
nano-indentation. The films were comparatively
stable than the graphite coated films. Further the
soft films are found to have good wear properties.

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