MIDDLE EAST TECHNICAL UNIVERSITY

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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Prof. Dr. Macit ÖZENBAS Surface Sciences Research
Laboratory Dept. of Metallurgical and Materials
Eng. Middle East Technical University Phone 0-31
2-210 25 32 Fax [phone] E-Mail ozenbas
_at_metu.edu.tr
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING

• Main Activities in the Surface Sciences Research
  Laboratory
• Production of metallic and ceramic thin films by
  using different processing techniques such as
  PVD, CVD, and chemical solution deposition.
• Microstructural and property characterization
  of these thin films by microscopy, diffraction,
  electrical, magnetic and optical characterization.

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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
The stages of deposition of Se on a nickel
substrate. Tsubstrate 70ºC Magnification bar
2 ?m
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Se islands on sapphire and nickel
substrates Magnification bar 1 ?m
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING

• Related studies on the formation of thin films
• ? Crystallization of Amorphous Selenium Thin
  Films
• ? Adhesion of Thin Films
• Amorphous to Crystalline Transition of Selenium
  Thin Films Deposited onto Aluminum Substrate
• Effects of Annealing on Electrical Resistivity
  of Aluminum Thin Films
• Effect of Surface Activation on the Adhesion
  Behaviour of Metallic Films

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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SUPERCONDUCTING THIN FILMS In this study, high Tc
superconducting thin films of Y-Ba-Cu-O system
have been prepared by resistive evaporation of
YF3, BaF2, and Cu powders using either one of two
different methods, namely the mixed-powder method
and the sequential-deposition method, and a
subsequent multi-stage annealing. The substrates
employed were polycrystalline ?-Al2O3 and single
crystals of MgO (100), LaAlO3 (100), and SrTiO3
(100).
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrograph of 2 ?m thick film grown onto
?-Al2O3 substrate and annealed in dry oxygen.
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Fully-automated measurement unit using
four-terminal resistivity measurement technique.
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Electrical Resistivity Temperature behavior of
1 ?m thick film grown onto ?-Al2O3 substrate with
a 0.15 ?m Cu buffer layer.
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrograph of the 1 ?m thick films grown by
the sequential-deposition method onto LaAlO3
(100) substrate.
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING

• Related studies on superconducting thin films
• ? Synthesis and Characterization of
  Superconducting Y-Ba-Cu-O Films Prepared by
  Sol-Gel Processing
• ? Effect of Ni and Ti Substitution on the
  Superconducting Properties of YBa2Cu3O7-x System
• ? Characterization of Superconducting Y-Ba-Cu-O
  Thin Films Prepared by Resistive Evaporation
• Characterization of Superconducting
  Bi-Sr-Ca-Cu-O Films Prepared by Sol-Gel Processing

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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
HOT FILAMENT ASSISTED CHEMICAL VAPOR DEPOSITION
OF DIAMOND COATINGS In this study, the gradual
change in crystal structure and morphology of
diamond to DLC during growth on Si (111)
substrates were examined by HFCVD method.
Filament temperature and flow rates were taken as
constant in all experiments. C2H5OH/H2 ratio and
deposition durations were changed for each sample
Cubo-octahedron diamond morphology was observed
in the initial stages of deposition. As the
growth increased, diamond morphology changed to
cauliflower structure.
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Schematic drawing of the hot-filament CVD system
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrographs of the diamond particles
deposited on Si substrate at 650ºC for 1/2 and 2
hours (ethyl alcohol volume percent 1 )
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrographs of the diamond particles
deposited on Si substrate at 650ºC for 4 and 6
hours (ethyl alcohol volume percent 1 )
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrographs of the diamond particles
deposited on Si substrate at 650ºC for 6 hours
(ethyl alcohol volume percent 1 )
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrographs of the diamond particles
deposited on Si substrate at 650ºC for 4 and 6
hours (ethyl alcohol volume percent 1.3 )
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrograph of the diamond particles deposited
on Si substrate at 650ºC for 4 hours (ethyl
alcohol volume percent 1.6 )
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Nucleation and growth kinetics of low-pressure
diamond deposition on a non-reacting surface
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
FERROELECTRIC THIN FILMS (COST 514 PROJECT)
In this study, ferroelectric Pb(Zr,Ti)O3 films
and powders were prepared from metal chlorides
using sol-gel processing method. For powders
homogeneous precipitation from aqueous solution
and for films dip coating just before
precipitation was applied in the presence of
urea, ?(NH2)2CO?. Pt-coated Si (111) wafers, Si
wafers and ?-Al2O3 were employed as substrates.
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
PZT powder prepared using urea, annelaed at
850ºC for 5 hours having spherical and fine
particle size
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrographs of PZT films on PT-coated Si
substrates prepared by no urea and urea, annelaed
at 850ºC for 5 hours
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
PZT FILMS ON METAL SUBSTRATES

• High toughness of the substrate in some
  micromechanical applications.
• To avoid micromachining and brittle silicon
  structures, metal foils can be used as
  substrates.
• High frequency operation, low dielectric loss,
  low electrical series resistance, etc.
• The metal should have a high melting point.
• It should have a similar value of thermal
  expansion coefficient to PZT.
• It should have low reactivity with PZT.
• It should permit good adhesion to PZT.

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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrographs of PZT films on stainless steel
showing the pyrochlore-perovskite transformation
and the crystallized film
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
PREPARATION AND PROPERTIES OF Ba1-xSrxTiO3
FILMS DEPOSITED BY THE SOL-GEL TECHNIQUE

• Barium strontium titanate BST (Ba,Sr)TiO3 has
  been extensively studied for advanced dynamic
  random access memory (DRAM) and
• uncooled infrared detector applications
• because of
• its high dielectric constant and
• composition-dependent Curie temperature (from 30
  to 400 K).

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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrograph of Ba0.8Sr0.2TiO3 film on
Pt/Ti/SiO2/Si substrate (1.3 ?m thick)
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Dielectric properties of BST films on
Pt/Ti/SiO2/Si substrates measured at 1 kHz
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SUB-MICRON PATTERNING OF Pb(Zr0.52Ti0.48)O3
USING SOL-GEL PROCESSING NSF PROJECT

• To pattern piezoelectric ceramics on a variety of
  substrates
• To pattern at the micron length scale
• To fabricate micron-sized piezoelectric
  cantilever sensors
• Gravimetric Measurements
• Chemical Sensing
• Damping Effects

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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Current Technology of Patterning Oxide

• Two steps of forming and patterning
• Uniform deposition by vapor phase techniques
  (PVD, CVD, MOCVD, RF Sputtering)
• Photolithography and post-deposition etching
• Disadvantages
• Expensive equipment and clean room environment
• Non-uniform etching rates, etch resistant
  materials
• One exposure per structure
• Difficulties with sharp geometry

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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
Schematic diagram of the micromolding in
capillaries process used in this study
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PZT Lines on Silver Foil
PZT
Silver
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PZT
10 mm
5 mm
Low and high magnification SEM images of a
micropatterned PZT net on a silicon substrate
after annealing at 600?C for 3 h.
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SEM image of micropatterned PZT on platinum
coated silicon wafer after annealing at 600?C for
3 h.
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PZT Lines on Silicon Substrate
5 mm
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Cross-sectional TEM images of micropatterned PZT
lines on a silicon substrate (A) bright field
image of one PZT line (B) dark field image of
the same line and (C) bright field image of an
array of lines at low magnification. The insert
shows the electron diffraction pattern for the
perovskite phase at the zone axis of 011. The
dotted line in (C) corresponds to the interface
between PZT lines and the Si substrate. The TEM
sample was prepared by ion milling of a
cross-sectioned sample that was annealed at 600C
for 3 h.
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EDS of PZT Lines on Platinum coated Silicon Wafer
Pt
Pb
Zr
2 mm
Ti
Si
Image
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Electrical Characterization of Patterned PZT
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P-E hysteresis loop of patterned PZT film (2 ?m
line widths) on platinized Si wafer, heat treated
at 6000C for 3 hours.
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  Ferroelectric and dielectric properties of
patterned PZT films on platinum coated (100)
silicon wafers which were heat treated at 600 ?C,
3 h. Pattern Type Ec (kV/cm) Pr
(µC/cm2) Dielectric tan d at 1
kHz Constant ()   Different line widths
41.96 38.94 560 5.73 2 µm line
widths 52.36 28.66 421 5.14 1 µm
line widths 48.40 26.53
426 5.28    
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P-E hysteresis loop of patterned PZT film (2 ?m
line widths) on stainless steel substrates, heat
treated at 6000C for 3 hours.
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Ferroelectric and dielectric properties of
patterned PZT films on stainless steel substrates
which were heat treated at 600 ?C, 3 h. Pattern
Type Ec (kV/cm) Pr (µC/cm2) Dielectric tan d
at 1 kHz Constant ()   Different line
widths 20.87 12.48 416 5.64 2
µm line widths 19.25 16.22
534 5.12 1 µm line widths 30.00 14.09
363 6.46  
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PZT Microcantilever
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
PHOTOCATALYTIC TiO2 THIN FILMS BY CHEMICAL
SOLUTION DEPOSITION
In this work, TiO2 thin films were prepared by
using sol-gel processing on soda-lime glass and
silicon substrates. Precursor solutions for TiO2
films were prepared by using the proper amounts
of titanium tetraisopropoxide, diethanolamine and
ethanol. The resulting alkoxide solution was kept
standing at room temperature for hydrolysis
reaction for 2 hours. The films were formed on
the glass and silicon substrates from the
precursor solution by spin coating at 2000 rpm in
an ambient atmosphere. These films were dried at
300?C for 10 minutes followed by a heat treatment
cycle at 500?C for 1 hour. The thickness of the
TiO2 films was adjusted by repeating the spin
coating cycle before the final heat treatment.
Finally, various amounts of polyethylene glycol
(PEG) were added to the above solution to observe
its effect on the film morphology.
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MIDDLE EAST TECHNICAL UNIVERSITY
DEPARTMENT OF METALLURGICAL AND MATERIALS
ENGINEERING
SEM micrographs of TiO2 films deposited on Si
substrates by spin coating showing the effect of
the addition of PEG to yield pores to increase
the photocatalytic activity.