Papers

ICMCTF1999 Session H1-2: New Horizons in Thin Films and Coatings

Monday, April 12, 1999 1:30 PM in Sunrise Room

Monday Afternoon

Start	Invited?	Item
1:30 PM		H1-2-1 Parallel Synthesis and Screening of Combinatorial Thin Film Libraries B. Symyx Corporation, B. Haushalter (Symyx Corporation) This talk will discuss the type of information that can be extracted from the application of combinatorial synthesis and screening techniques to thin film libraries. Two of the main points to be emphasized are (1) the profound need to fully integrate the parallel synthesis and rapid screening at the beginning of the experiment and (2) the necessity of making the library elements self consistent within the libraries as opposed to making a single sample with certain properties. Examples to illustrate the techniques involved, and the type of information available from libraries of materials such as luminescnet materials, heteogeneous catalysts and electronic materials, will be presented.
2:10 PM		H1-2-3 Combinatorial Synthesis and Characterization of Metal Oxide Thin Film and Device Libraries I. Takeuchi, H. Chang, C. Gao, J. Wang, Y.K. Yoo, P.G. Schultz, X.-D. Xiang (Lawrence Berkeley National Laboratory) In order to address materials issues of increasingly complex functional metal oxides, we have developed comprehensive combinatorial synthesis and evaluation methods targeting a variety of electronic thin film applications. Thousands of different compositions are created on individual chips by successive deposition of precursors through in-situ metal masks and/or lithographic lift-off steps with rapid turn-around. Our film deposition methods include a high-vacuum multi-target pulsed laser deposition system equipped with automated high-precision in-situ shutters. In order to efficiently survey a diverse variation of compositions in a given library, various masking schemes are used to design high density libraries (e.g. 1024 samples in 1 cm²). The in-situ shutters are also used for creating controlled gradient composition samples for optimizing the composition of lead compounds selected from the libraries. Following the depositions, samples undergo various annealing processes for interdiffusion of precursors and crystal growth of the materials. X-ray diffraction reveals that predominantly single phase epitaxial films with good crystallinity can be obtained in the libraries. Libraries are then screened for desired physical properties using different scanning measurement techniques including scanning evanescent microwave microscopy. We have fabricated various ferroelectric/dielectric libraries for DRAM and high frequency agile applications. Investigation of thin film phase diagrams using the gradient deposition technique will also be discussed.
2:50 PM		H1-2-5 Biocompatible Surfaces by Immobilization of Heparin on Diamond-like Carbon Films R. Stenzel, J. Schmidt, H. Steffen (Mannheim University of Applied Sciences, Germany); A. Rar, S. Hofmann (National Research Institute for Metals, Japan) Although graphitic carbon has been known and used as a biomaterial for a very long time, the excellent biocompatibility of DLC films has been addressed only in a few cases. We anticipate the combination of bioinert DLC films and surface-immobilized bioactive biomolecules with antithrombogenic properties, like the polysaccharide heparin or various special proteins, as a straightforward concept to optimize the haemocompatibility of a wide variety of materials. Therefore, to assess this property in view of an application as vascular grafts, in-vitro studies on DLC-coated and heparinized polymer substrates were performed. DLC films were deposited on UHMW-PE, PTFE, PET and PES in a RF plasma of acetylen and argon and subsequently exposed to an ammonia plasma before heparin was covalently coupled to such functionalized surfaces by different methods. The biochemical characterization by toluidin blue, antithrombin III and L929-cell cytotoxicity tests revealed in accordance with XPS measurements the high amount of heparin on the surface, an extended blood coagulation time and cell vitality on hydrophilic surfaces. Thus, the efficiency of the plasma treatment for functionalization and successful improvement of the haemocompatibility of DLC films could be shown.
3:30 PM		H1-2-7 Future Directions For Magnetic Data Storage Media D.N. Lambeth (Carnegie Mellon University) The demonstration of 13 Gigabit/in2 indicates that the 60%/yr. areal density growth rate remains unabated. The spin valve technology may be extendible beyond the 100 Gigabit/in2 regime, but Lu and Charap have indicated that due to thermal relaxation isotropic longitudinal media will show data retention problems at about 1/3 of this value. While appearing at different areal densities, the thermal instability issues are non-discriminatory as to the magnetic recording modality: longitudinal, perpendicular, magnetooptic, near field, etc. To attack this fundamental limitation a systematic design approach toward media invention is possible which should not, initially, require a revolutionary new physical recording system. To achieve the coercivity and noise requirements for an initial doubling of areal density (25 Gbit/in2), very small, near perfect crystalline grains are required. For another quadrupling, not only will crystalline perfection and narrow size distribution be required, but singly oriented and magnetically saturated grains are needed. While low magnetization, high anisotropy energy, partially oriented, exchange coupled longitudinal media may approach this density, it will probably come at the expense of an improved head field gradient. Beyond these densities, self assembled order grain structures appear to be essential. The first goals can be accomplished by controlled growth of the magnetic microstructure. For the later goals epitaxial growth of thin film structures on single crystalline Si provides a pathway to various highly oriented thin films. For hcp Co-alloys, well defined axial directions are determined by the substrate and multiple thin film epitaxial relationships. Here we provide an overview of the recording system challenges which are guiding our media design philosophy, discuss materials issues, processes and multi-layered thin film material structures used to control the microstructure and magnetic properties of Co-alloy films.
4:10 PM		H1-2-9 Applications of Magnetic Thin Films in Hard Disk Drive Recording Heads R.P. Michel, S. Bozeman (Seagate Recording Heads) Advanced hard disk drive recording heads consist of an inductive write head merged with a magnetoresistive readback head. An overview will be presented of the role of magnetic thin films in this device. These magnetic films cover a wide range of thicknesses: 2 microns to 2 nanometers, and magnetic properties: soft ferromagnetic, hard ferromagnetic, and antiferromagnetic. These layers are optimized for performance and manufacturability using a wide variety of PVD and electroplating techniques. Particular focus will be placed in the following three areas: (1) thick soft magnetic films used for shield and pole materials, (2) hard magnetic films used for sensor stabilization, and (3) thin magnetic multilayer stacks used as magnetoresistive readback sensors.
4:50 PM		H1-2-11 Studies of Ferroelectric Thin Film Growth Processes and Domain Dynamics Using in Situ Analytical Techniques O. Auciello, A.R. Krauss, J. Im, D.M. Gruen, A. Munkholm, G.B. Stephenson, J.A. Eastman, S.K. Streiffer (Argonne National Laboratory); E.A. Irene (University of North Carolina); C. Thompson (Northern Illinois University & Argonne National Laboratory); V.P. Dravid, R.P.H. Chang (Northwestern University); A. Gruverman (Sony Research Center, Japan); S. Aggarwal, R. Ramesh (University of Maryland) The science and technology of ferroelectric thin films has experienced an explosive development during the last ten years. Low-density memories are now being incorporated in devices such as cellular phones and "smart cards". However, substantial work remains to be done to develop materials integration strategies for high-density non-volatile ferroelectric random access memories (NVFRAMs). We have demonstrated that the implementation of a variety of complimentary in situ or in situ, real-time characterization techniques is critical to understand film growth and device related processes. We are using a unique time of flight ion scattering and recoil spectroscopy (TOF-ISARS) technique to perform in situ, real-time studies of film growth processes. TOF-ISARS involves three distinct but closely related experimental methods, namely: ion scattering spectroscopy (ISS), direct recoil spectroscopy (DRS) and mass spectroscopy of recoiled ions (MSRI), which are capable of providing monolayer-specific information on film growth and surface segregation processes under the ambient conditions required for growing ferroelectric and other thin films. TOF-ISARS can "see" the surface of thin films, but not buried interfaces. Therefore, we have combined TOF-ISARS with Spectroscopic Ellipsometry, which permits the investigation of buried interfaces as they are being formed. The polarization state and polarization reversal in ferroelectric thin films are naturally linked to domain arrangements and their transformations. Therefore, direct imaging of domain structures and investigation of their behavior under an applied electric field can provide valuable information for a general understanding of switching phenomena and the role domains play in degradation effects such as polarization fatigue and retention loss in ferroelectric films. We are using scanning force microscopy (SFM) to perform in situ nanoscale imaging of polarization domains in ferroelectric thin films to study polarization reversal and retention loss. We are also investigating domain dynamics using in situ TEM analysis. Synchrotron X-ray scattering is another powerful technique for in situ, real-time studies of film growth and device related processes. We have begun programs to study film growth processes and switching phenomena in ferroelectric thin films using MOCVD film growth and capacitor testing systems located at one of the ports of the Advanced Photon source in Argonne National Laboratory. The work to be discussed will include studies of growth processes and microstructure-property relationships of layered perovskite SrBi2Ta2O9 (SBT) films, currently included in commercially available "ferroelectric smart cards", and nanoscale studies of domain dynamics in Pb (ZrxTi1-x)O3 (PZT) capacitors. The results will be discussed in the context of the basic scientific and technological implications.