ICMCTF2008 Session B4: Laser and Ion Beam Surface Engineering
Thursday, May 1, 2008 1:30 PM in Royal Palm 1-3
B4-2 Deposition of DNA Thin Films by Through Thin Film Ablation
S. Fairchild (AFRL/MLPS)
There is increasing need for sensors in applications with lightweight and low power requirements and in thin film transistors with high effective charge carrier mobility for switching and communications. Thin films of biopolymers may be well suited for both applications. We have used a recently-developed, novel form of laser ablation, denoted through thin film ablation (TTFA), to deposit thin films of deoxyribonucleic acid (DNA). We have characterized the films by capacitance, Hall, resistivity, dielectric, conversion efficiency and AFM imaging. In addition to forming pin-hole free films, TTFA has potential advantages over other more conventional processing techniques such as spin coating. These advantages include controlled deposition of thinner films, better thickness control and the ability to create layered structures. TTFA is also amenable to the blending of conductive polymers and to incorporating nanoparticles, nanotubes, and nanopearls in bio-organic host films for optimizing device properties. The results of DNA deposition by TTFA will be compared to those formed by other PLD processes including marix assisted pulsed laser evaporation (MAPLE) and conventional PLD.
B4-3 Laser Materials Processing at NRL: From Thin Films to Devices
A. Piqué, H. Kim, R.C.Y. Auyeung, K. Metkus, T. Sutto, M. Osofsky, S. Mathews (US Naval Research Laboratory)
The use of lasers for processing materials in thin film form has been the subject of intense study over the past 20 years. From its early applications in high temperature superconductivity, pulsed laser deposition or PLD, was recognized as an excellent technique for the fast and reproducible growth of thin films of complex oxides. Since then, PLD and other laser-based techniques have been used in the deposition of insulators, semiconductors, metals, superconductors, polymers and biological materials. At the Naval Research Laboratory, we have employed various of these techniques to fabricate structures capable of transmitting both electricity and light such as transparent semiconductive oxides, store energy such as microbatteries, and laser print patterns in non-lithographic ways such as interconnects for microelectronics. All these structures share in common the ability to be finely tuned by adjusting the parameters of the laser processing conditions, thus allowing their adaptation to a specific application. This presentation will provide an overview of recent results at the Naval Research Laboratory in laser deposition of materials in thin film form as well as laser processing of 3-dimensional patterns of nanoparticles. Examples of the various types of devices fabricated from theses structures will be presented and their performance will be discussed. @paragraph@This work was supported by the Office of Naval Research.
B4-5 Effects of Nitrogen Ion Implantation on Plasma Polymerized Tetraisopropxytitanium-Oxygen-Helium Mixtures
N.C. Da Cruz, B.B. Bellotti, E.C. Rangel (Universidade Estadual Paulista, Brazil); M.A.B. Moraes (Universidade Estadual de Campinas, Brazil); S.F. Durrant (Universidade Estadual Paulista, Brazil)
Relatively little is known about the effects of ion implantation on plasma polymers. In this work films were produced by the PECVD of tetraisopropoxytitanium-oxygen-helium mixtures and irradiated with nitrogen ions at fluences, F, between 10@super 14@ and 10@super 16@ ions/cm. Fourier Transform Infrared Spectroscopy (FTIR) revealed the presence of Ti-O groups in all of the films. Present in the as-deposited films were O-H and C-H groups, but both of these decreased with increasing F and were virtually eliminated at high F, indicating the loss of hydrogen. Irradiation also produced compaction, which reached about 40% (measured via the film thickness) at the highest fluence. X-ray Photoelectron Spectroscopy (XPS) analyses revealed a decrease in the O to C atomic ratio as F increased, while the Ti to O ratio hardly altered, remaining at around 0.35. The ratio Ti:C reduced from around 1.5 for the untreated film to around 0.8 at the highest F. The optical gap of the films derived from ultraviolet-visible spectra remained at about 3.6 eV for all fluences except the highest, for which an abrupt fall to around 1.0 eV was observed. The electrical conductivity, measured using the two-point method, showed a systematic dependence on F. We thank the Brazilian agencies FAPESP and MCT/CNPq for financial support.
B4-7 Nanocomposite Metal-S-T Solid-Lubricant Thin Film Coatings Deposited by High-Power Ion Beam Ablation@super 1@
T.J. Renk (Sandia National Laboratories)
Thin-film coatings such as MoS@sub 2@ have been been studied for a number of years as a self-lubricating wear-resistant film for a number of applications. We are exploring the addition of Ti to both MoS@sub 2@ and WS@sub 2@ films in order to improve their friction behavior under humid conditions. The films are formed by ablation of alternating Ti and WS@sub 2@ or MoS@sub 2@ targets by high-power pulsed ion beams from the 750 kV RHEPP-1 facility at Sandia National Laboratories. The individual deposited layers from each pulse are between 5-20 nm in thickness. The beam fluence of up to 10 J/cm@super 2@ is used to ablate either a composite Ti/metalS@sub 2@ target, or ablate alternately two discrete targets. The depositional substrate is either at room temperature, or heated to 350° C. Although Ti is the primary admixed metal, other metals such as Ni may be investigated. When MoS@sub 2@/Ti interlayered films are deposited with a substrate temperature of 350° C, an array of 100 nm-sized single crystal Mo spheres are observed to be formed. Such films demonstrate low wear and good friction behavior under conditions of 50% relative humidity. Films made at room temperature, or from a composite MoS@sub 2@-Ti ablation target do not demonstrate this low-wear/friction behavior. Further Pin-on-disk testing, SEM, and XTEM of these films is planned to determine the cause for the difference in performance. Films of WS@sub 2@/Ti are planned as a comparison. @paragraph@@super 1@Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Co., under US DOE Contract DE-AC04-94AL85000.
B4-8 Ion Beam Sputter Deposited TiAlN Bottom Electrode for the Dielectric and Leakage Characteristics of (Ba,Sr)TiO@sub3@ Thin Film Capacitor
S.-Y. Lee, S.C. Wang, J.S. Chen, J.-L. Huang (National Cheng-Kung University, Taiwan)
(Ba,Sr)TiO@sub3@ (BST) dielectric films have attracted a lot of attention for potential use as capacitors in dynamic random access memory (DRAM) while TiAlN thin film is a strong candidate for barriers because of its good thermal stability, diffusion barrier property, and good oxidation resistance. As far as we know, studies on TiAlN film as bottom electrode and diffusion barrier, a multifunction layer, for BST metal-insulator-metal (MIM) capacitors are rare. Each layer of the Al/BST/TiAlN MIM capacitors were deposited on thermally oxidized n-type Si(100) wafers using a ion beam sputter deposition system from a Ti-Al alloy target (90:10 at%), a (Ba@sub0.5@Sr@sub0.5@)TiO@sub3@ ceramic target and an Al metal target, respectively. As an adhesion layer, thin Ti-Al film was deposited first and N@sub2@ was leaked into the chamber as reactive gas during deposition for the TiAlN films. Al top electrodes patterned using shadow mask were fabricated on post-annealed BST films for I-V and C-V characteristics measurement. Surface morphology and the cross-section structure were observed by a field emission scanning electron microscope. Transmission electron microscopy observations were used to evaluate the film microstructure. The compositions and depth profile of the films were determined using electron spectroscopy for chemical analysis and Auger electron spectroscopy. The phase and crystallinity of films were determined using glancing-angle x-ray diffractometry. The I-V and C-V characteristics of Al/BST/TiAlN MIM capacitors were examined using a PA meter/dc voltage source HP4140 and Precision LCR meter HP4128A.