Novel Materials and Processes
Thursday, May 3, 2001 1:50 PM in Room Sunrise
H4-2-2 Processing/Structure/Property of Coatings and Thin Films Deposited Using a Novel and Cost-Effective Esavd Method
K.L. Choy (Imperial College of Science, Technology and Medicine, United Kingdom)
This paper gives an overview of an emerging novel and cost-effective Electrostatic Spray Assisted Vapour Deposition (ESAVD) process used for the synthesis of coatings and films. The ESAVD process involves spraying atomised precursor droplets across an electric field. The charged droplets undergo heterogeneous chemical reaction near the vicinity of the heated substrate to deposit a stable solid film onto a heated substrate. This is a variant of CVD process which does not require the use of sophisticated reactor and vacuum system. This process can be performed in an open atmosphere for the deposition of highly pure materials with structural control at the nanometer scale level. The structure, stoichiometry, crystallinity, texture and film thickness can be controlled by optimising the deposition conditions. The scientific and technological significance of the ESAVD method to produce a range of thin films and and coatings such as TiO2, Y2O3-ZrO2, Y2O3:Eu, In2O3-SnO2, CdS, ZnS, etc will be presented.The processing/structure/property relationships of the deposited films will be discussed. The advantages of the ESAVD method will be highlighted and compared with other conventional thin film and coating deposition techniques, including Chemical Vapour Deposition and Physical Vapour Deposition.
H4-2-3 Electron Emission Enhanced Chemical Vapor Deposition (EEECVD) for the Fabrication of Diverse Silicon-Containing Thin Films
M.A. Bica de Moraes, S.F. Durrant (Universidade Estadual de Campinas, Brazil)
A vacuum system containing a tungsten filament and a substrate to which a positive bias may be applied to control the filament emission current is currently under development for the chemical vapor deposition of amorphous thin films. Hydrogenated carbon films also containing such elements as nitrogen, oxygen, silicon, or fluorine, may be fabricated using this technique. In this work the feasibility of the production of diverse silicon-containing films from vapor of the monomer tetramethylsilane alone or in mixtures with nitrogen or oxygen is demonstrated. Substrate currents and deposition rates are mapped as a function of the substrate bias voltage (V@sub B@). The chemical structures and compositions of the films are investigated using transmission infrared- and Rutherford backscattering-spectroscopy. It is demonstrated that film fabrication is possible over a wide range of V@sub B@, even when there is no significant contribution of thermal energy from the filament and in the absence of a glow discharge in the filament/substrate region.
H4-2-4 The Titanium Coated Polymeric Membranes for Hydrogen Recovery
Y.K. Vijay, S. Wate, N. Acharya, J.C. Garg (University of Rajasthan, India)
The polymeric membranes are commercially used for gas separation. The important parameters for their commercial application are good permeabilities and permselectivities. These parameters have a strong dependence on the free volume hole properties of the material.@paragrph@The membranes alone are generally not suitable when high product purity and recovery is desired. However, the titanium coated polymeric membranes can effectively solve the problem. Hydrogen molecules when diffuse through metals like titanium and paladium break into atomic form and recombine upon recovery. The binding of the metalic clusters on the polymeric material is improved by heat treatment and swift heavy ion bombardment.@paragraph@The purity of the permeat gas i.e. hydrogen is estimated by the measurement of decrease in the permeabilties of other gases present in the mixture.@paragraph@Results of the study of the permeation properties of polycabonate films coated with 50-100Å thick titanium film show increase in the purity of hydrogen.
H4-2-5 Growth and Characterization of Electrochemically Formed Nanocrystalline Cobalt Ferrite Thin Films
S.D. Sartale, C.D. Lokhande (Shivaji University, India)
Cobalt Ferrite thin films have large scale technological applications as catalyst, magnetic recording media, ferrofluids and in microwave devices. All the methods that have been used to sysnthesis of ferrite thin films often require a high degree sophistication and control and substrate heating during and/or after deposition of the films to obtain the desired characteristics properties in thin film form. An alternative method of producing thin film ferrite by a simple technique will be well received. Wet chemical methods such as electroless and/or electrochemical techniques appear to be an attractive method.@paragraph@This paper reports formation of cobalt ferrite thin films using electrochemcial route. Electrodeposition of CoFe@sub2@ alloy from simple aqueous and nonaqueous sulfate bath was carried out onto various conducting substrates such as tainless steel, brass, copper, titanium and FTO coated glass. The desired thickness was obtained at I1N KOH electryolyte. AAS, XRD, IR absorption and SEM techniques were used for compositional, structural and surface morphological studies. By forming metal-oxide-metal (MOM); cooper-oxide-copper, effect of temperature and frequency on dielectric and conducting properties were studied. The films are nanocrystalline with spinel structure and uniform surface and having low dielectric constant and high electrical resistivity. Thus the feasibility of obtaining cobalt ferrite thin films by electrochemical route is studied.
H4-2-6 Nanostructured Oxide Interfaces and Thin Films
D. Norton (University of Florida)
For complex material systems, the ability to investigate and manipulate structure and defects in thin films at the nano- to micro-scale is one of the fundamental challenges in materials research. Conceptually, one can envision the engineering of material properties at the atomic level so as to tailor to the specific functions relevant to material performance. However, this requires an understanding of the material properties at the nanoscale, as well as development of advanced synthesis and measurement techniques suitable to produce and characterize the appropriate structures. In recent years, research in the synthesis of complex oxide thin films has begun to explore the atomic-level control of structure that is necessary to realize nanostructured materials and interfaces. This has enabled investigations of oxide materials, including ferroelectrics, superconductors, and dielectrics, as a function of defect structure and dimensionality. In this presentation, the synthesis, properties, and application of epitaxial oxides will be discussed, focusing on recent efforts control nucleation and epitaxy at the atomic scale.
H4-2-8 Effects of Rapid Infrared Anneal on Boron Carbide Nanostructure Coatings,
M.Y. Chen (Air Force Research Laboratory, Materials Directorate, USAF); J.H. Li, J.W. Seok, R.Y. Lin (University of Cincinnati)
Boron carbide in bulk ceramic or powder form has demonstrated extreme hardness and chemical inertness due to its covalent bonding. There is strong interest in boron carbide coatings for protective, wear, or corrosion resistance applications. However, the inherent brittleness of this material requires special designs of the coating nanostructure to achieve high fracture toughness. In this study rapid infrared heat treatment is applied to bilayer coatings consisting of boron carbide and a metal (Mo or Ti) which are deposited using d.c. magnetron sputtering with substrates held at ambient temperatures. A combination of analytical techniques including x-ray photoelectron spectroscopy, standard x-ray diffraction, and SEM/EDS analysis are used to determine the composition, chemical bonding, phase structure, and morphology of the films before and after thermal treatment. Mechanical testing includes nanoindentation, scratch testing, and pin-on-disc tribotesting. The effects of rapid infrared thermal anneal on the microstructure, composition, chemical structure, morphology and tribological property of the boron carbide/metal bilayer coatings will be presented.
H4-2-9 Ti/Al@sub 2@O@sub 2@/Si Nanostructures: Fabrication and Application in Nanoelectronics
S.A. Gavrilov (Loukin's Research Institute of Physical Problems, Russia); A.V. Emelyanov, R.V. Lapshin (State Scientific Center, Research Institute of Physical Problems, Russia)
Formation of Ti/Al@sub 2@O@sub 3@/Si multilayered nanostructure was developed. A two-chamber ultra-high vacuum technological unit allowed us to fabricate the structure in single cycle. A 4 inch n-type Si wafer with resistivity 0.01 @ohm@cm was used as a substrate. The first chamber was used for laser evaporation of Al@sub 2@O@sub3@ to form 20 nm gate insulator. In the second camber Ti film 8 nm of thick was deposited onto the insulator film. @paragraph@Conditions (substrate temperature and deposition velocity) were determined on the basis of a volumetric agreement principle. The principle allowed us to form both of Ti/Al@sub 2@O@sub 3@ and Al@sub 2@O@sub 3@/Si interfaces with low concentration of surface states. @paragraph@ After formation of the sandwich nanostructure a standard photolitography processing was used to form narrow (1 µm of width)and long (10 µm of lenght)pattern of the Ti film. Al contacts with area of 20x20 µm were formed at the ends of the Ti pattern. @paragraph@ To fabricate channel of a creating field effect transistor we used a technique of SPM tip-induced nanoxidation of the Ti film. Regimes of the nanooxidation were optimized on the basis of a model wich describes the tip-induced oxidation kinetics. Influence of the Ti film thickness and electrical regimes of the oxidation on the resolution, reproducibility and productivity was disscussed. The nanooxidation technique allowed us to form the transistors with TiO@sub 2@ channel 8, 10, 20 nm of width and 1 µm of length. The Si substrate with ohmic contact on the back-side was a gate electrode. @paragraph@ Electrical measurements allowed o investigate physical characteristics of the nanoscale transistors. It was shown that developed technological technique is suitable for fabrication of single-electron devices.
H4-2-10 Characteristics of Tini Alloy Thin Films
J. Ting, P. Cheng (National Cheng Kung University, Taiwan)
TiNi alloy thin films were prepared using a dc magnetron sputter deposition technique. The working pressure (P), target to substrate distance (D), and applied power (W) were varied to examine their effect on the characteristics of the as-deposited and heat treated TiNi films. The heat treatment was carried out at 550 deg.C and 600 deg.C for 30 minutes. The as-deposited TiNi thin films were amorphous and crystallized after the heat treatment. The amorphous to crystalline (A/C) transformation behavior was investigated using X-ray diffractometry (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The kinetic parameters of the transformation were determined from the DSC signal and analyzed using the Kissinger's method and the Aavrami's method, from which the activation energy was calculated and compared to literature data. The film composition was also examined and found to depend on all the above parameters in a way that the concentration of Ti increased with the pressure p, distance D, and the power W. The dependence was more significant at low pressures.