This poster presented the deposition of metallic thin film by the wet-chemistry methods, i.e. the galvanic displacement and the electrodeposition. The methods offered not only the simplicity and low-cost of the experimental setup, but also certain levels of control over the morphology, density, and size of the deposited metallic nanostructures. Several characterization methods were applied to examine the thin films, including the SEM, AFM, XRD, and XPS. Furthermore, thin film deposition by physical and chemical vapor deposition will be outlined for future work. Finally, the samples were tested for their applicability for Surface Enhanced Raman Spectroscopy (SERS) in which low concentrations of Rhodamine 6G (R6G) dye and paraoxon, a highly toxic organophosphate pesticide, were detected. They showed promising results.

1. Metallic Thin Film Deposition for Sensing Applications
Minh Tran
Materials Science and Engineering Research Institute (MSERI), American University of Sharjah, University City, Sharjah, UAE
Motivation
• Surface Enhanced Raman Spectroscopy (SERS) is a simple, inexpensive, and rapid
analytical technique with excellent sensitivity
• SERS is a surface-sensitive method, which depends on material, morphology, size, and
density of surface nanostructures
• We have several modern instruments available at MSERI to characterize and deposit
metallic thin films with controlled properties.
Thin Film Deposition by Wet Chemistry
• Two methods:
 Electrodeposition
 Electroless deposition / Galvanic displacement
• Advantage:
 Simple & inexpensive
 Can be performed at ambient condition
• Disadvantage:
 Difficult to control thin film thickness, morphology, size, and density
 Poor adhesion
Experimental Setup for Wet Chemistry Method
• Electrodeposition:
• Electroless Deposition / Galvanic Displacement:
Selected Characterization Results
• From Electroless Deposition / Galvanic Displacement:
 Au Deposition
 Cu Deposition
 Pd Deposition  Pt Deposition
• From Electrodeposition:
1 μm
Thin Film Deposition by Vapor Deposition Methods
• Three methods:
 Pulsed laser deposition
 Thermal evaporation
 Atomic layer deposition
• Advantage:
 Capable of depositing thin films with precise control of properties
 Capable of depositing thin films with multiple metallic components with ease
 Hybrid thin film structures are possible by these methods, which can enhance SERS
signal intensity, such as by the effects of 3D surface structures or charge transfer.
 Applicable to various depositing and substrate materials
Future Work on Thin Film by Vapor Deposition
 Several process parameters are available to improve thin film properties, including
Pulsed laser deposition: gas chamber pressure, number of laser pulses on target,
target to substrate distance, laser fluence, incidence angle, and laser wavelength
Thermal evaporation: substrate temperature, deposition angle, relative position of
the substrate to the evaporation source
 Metallic thin film can be deposited on carbon-based substrate to fabricate flexible
SERS
 Surface patterning of thin film by deposition on a template
• Pulsed laser deposition: • Thermal evaporation:
• Atomic layer deposition:
 Capable of depositing very thin (sub-
nanometer) film
 Can be used for depositing a thin, pin-
hole free overlayer to protect the surface
of SERS substrate and make it reusable
Selected SERS Results
Step-by-step one-cycle deposition (1x)
Left: SEM images of Au nanostructures deposited on Si substrate after one (1x), five
(5x), and ten (10x) deposition cycles. Right: XRD pattern of Au nanostructures on Si
substrate. The pattern suggests FCC structure
AFM maps and RMS roughness. Scan size of 2 μm x 2 μm. Height scale is in nm. Mean
values from five different locations on each sample are shown. Error bars represent 95%
confidence intervals.
Top: SEM of Cu-based
nanostructures (5x). Bottom:
XRD of Cu-based
nanostructures, suggesting
FCC structure
XPS spectra showing Cu oxidation states, oxide species,
carbon bonds, and Auger electron spectroscopy showing
Cu oxidation states. The dashed curves were
deconvoluted from the solid curves.
Left: SEM image of dendritic Pd
nanostructures on Si (10x). Right: EDX
patterns of Pd nanostructures on Si (5x). EDX
patterns recorded from individual
nanostructures presented as spots 1 & 2
Left: SEM image of Pt nanoparticles on Si
(10x). Right: EDX patterns of Pt nanoparticles
on Si (5x). EDX patterns recorded from
individual nanoparticles presented as spots 1,
2, and 3
SEM images of Au nanostructures electrodeposited at varying
potentials of -0.4 V, -0.6 V, -0.8 V, and at pH 3, pH 8, without
using L-cysteine. The insets show photographic images of the
corresponding SEM images.
XRD of Au nanostructures
deposited on ITO glass
substrate at a potential of -
0.8 V with pH 3 and 8 in
the presence and absence
of L-cysteine
Raman spectra of 10-4 M and 10-5
M Rhodamine 6G (R6G)
adsorbed on Cu-based and Au
nanostructures on Si, respectively
(left), and 10-2 M paraoxon
adsorbed on Au nanostructures on
Si (right). Raman spectra of R6G
and paraoxon adsorbed on bare Si
substrates are shown for
comparison.