MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Prof. Dr. Macit ÖZENBAŞ Surface Sciences Research Laboratory Dept. of Metallurgical and Materials Eng. Middle East Technical University Phone: Fax:

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Main Activities in the Surface Sciences Research Laboratory : u Production of metallic and ceramic thin films by using different processing techniques such as PVD, CVD, and chemical solution deposition. u Microstructural and property characterization of these thin films by microscopy, diffraction, electrical, magnetic and optical characterization.

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING The stages of deposition of Se on a nickel substrate. T substrate = 70ºC Magnification bar = 2  m

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Se islands on sapphire and nickel substrates Magnification bar = 1  m

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

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING SUPERCONDUCTING THIN FILMS In this study, high T c superconducting thin films of Y-Ba- Cu-O system have been prepared by resistive evaporation of YF 3, BaF 2, 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  -Al 2 O 3 and single crystals of MgO (100), LaAlO 3 (100), and SrTiO 3 (100).

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING SEM micrograph of 2  m thick film grown onto  - Al 2 O 3 substrate and annealed in dry oxygen.

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Fully-automated measurement unit using four-terminal resistivity measurement technique.

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Electrical Resistivity – Temperature behavior of 1  m thick film grown onto  - Al 2 O 3 substrate with a 0.15  m Cu buffer layer.

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 LaAlO 3 (100) substrate.

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

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. C 2 H 5 OH/H 2 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.

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Schematic drawing of the hot-filament CVD system

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 %)

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 %)

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 %)

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 %)

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 %)

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Nucleation and growth kinetics of low-pressure diamond deposition on a non-reacting surface

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING FERROELECTRIC THIN FILMS (COST 514 PROJECT) In this study, ferroelectric Pb(Zr,Ti)O 3 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,  (NH 2 ) 2 CO . Pt-coated Si (111) wafers, Si wafers and  - Al 2 O 3 were employed as substrates.

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

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

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.

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

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING PREPARATION AND PROPERTIES OF Ba 1- x Sr x TiO 3 FILMS DEPOSITED BY THE SOL-GEL TECHNIQUE  Barium strontium titanate [BST : (Ba,Sr)TiO 3 ] 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).

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING SEM micrograph of Ba 0.8 Sr 0.2 TiO 3 film on Pt/Ti/SiO 2 /Si substrate (1.3  m thick)

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Dielectric properties of BST films on Pt/Ti/SiO 2 /Si substrates measured at 1 kHz Film Composition Thickness (  m) Capacitance (nF) Dielectric Constant Ba 0.8 Sr 0.2 TiO Ba 0.75 Sr 0.25 TiO Ba 0.6 Sr 0.4 TiO

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING SUB-MICRON PATTERNING OF Pb(Zr 0.52 Ti 0.48 )O 3 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

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

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING Schematic diagram of the micromolding in capillaries process used in this study

10  m PZT Lines on Silver Foil PZT Silver

10  m 5  m PZT Low and high magnification SEM images of a micropatterned PZT net on a silicon substrate after annealing at 600  C for 3 h.

SEM image of micropatterned PZT on platinum coated silicon wafer after annealing at 600  C for 3 h.

PZT Lines on Silicon Substrate 5  m

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 600°C for 3 h.

2  m PtPbZr TiSiImage EDS of PZT Lines on Platinum coated Silicon Wafer

Electrical Characterization of Patterned PZT

P-E hysteresis loop of patterned PZT film (2  m line widths) on platinized Si wafer, heat treated at C for 3 hours.

Ferroelectric and dielectric properties of patterned PZT films on platinum coated (100) silicon wafers which were heat treated at 600  C, 3 h. Pattern TypeE c (kV/cm) P r (μC/cm 2 )Dielectrictan δ at 1 kHzConstant (%) Different line widths μm line widths μm line widths

P-E hysteresis loop of patterned PZT film (2  m line widths) on stainless steel substrates, heat treated at C for 3 hours.

Ferroelectric and dielectric properties of patterned PZT films on stainless steel substrates which were heat treated at 600  C, 3 h. Pattern Type E c (kV/cm) P r (μC/cm 2 )Dielectrictan δ at 1 kHzConstant (%) Different line widths μm line widths μm line widths

PZT Microcantilever

MIDDLE EAST TECHNICAL UNIVERSITY DEPARTMENT OF METALLURGICAL AND MATERIALS ENGINEERING PHOTOCATALYTIC TiO2 THIN FILMS BY CHEMICAL SOLUTION DEPOSITION In this work, TiO 2 thin films were prepared by using sol-gel processing on soda-lime glass and silicon substrates. Precursor solutions for TiO 2 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 TiO 2 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.

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.