ICMCTF1999 Session B6: Laser Assisted Deposition

Tuesday, April 13, 1999 1:30 PM in Room Forum/Senate/Committee
Tuesday Afternoon

Time Period TuA Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF1999 Schedule

Start Invited? Item
1:30 PM Invited B6-1 In Situ Plasma Diagnostics of Laser Ablated Carbon Plumes for Optimized Deposition of Novel Carbon and CN Coatings
D.B. Geohegan, A.A. Puretzky, C. Chi, G.E. Jellison, V.I. Merkulov, D.H. Lowndes (Oak Ridge National Laboratory)

Laser ablation of graphite is one of the most versatile techniques for the synthesis of novel carbon coatings. Ablation in vacuum can be optimized to produce hard amorphous diamond coatings, while low pressures of nitrogen can be introduced to reactively produce CNx films. Higher pressures of inert gas can be used during laser ablation to induce clustering for fullerene and carbon nanotube production.

In this paper, in situ plasma diagnostics are employed to understand and control the fundamental processes responsible for the optimized deposition of novel carbon coatings by the laser ablation of graphite. Several techniques (including intensified CCD-array photography, fast ion probe measurements, optical absorption spectroscopy, optical emission spectroscopy, Rayleigh-scattering, and laser-induced luminescence) are combined to form a coherent picture of the processes occurring during laser ablation, transport to the substrate, and deposition of thin films.

Amorphous diamond film properties vary with the laser energy density at the target and can be conveniently characterized by spectroscopic ellipsometry. Increasing the laser intensity at the target results not only in increased plume ionization and kinetic energies as measured by an ion probe, but in a redistribution of the species comprising the multicomponent plume (C3, C2, and C) arriving at the substrate. Gated imaging is utilized to reveal the interactions of the ablation laser pulse with the initial ejecta at different energy-density thresholds for 248-nm and 193-nm excimer laser wavelengths, and how gas-dynamic processes affect the transport of these species to the substrate. These fundamental studies are correlated with the film properties to understand the optimal conditions for pulsed laser deposition of amorphous diamond and carbon nitride thin films.

Background-gas interactions, particulates ejected from the target, clustering, and plasma manipulation techniques will also be discussed. This research was sponsored by the Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp., for the U.S. Department of Energy, under contract DE-AC05-96OR22464.

2:10 PM B6-3 Studies of the Ablation Plume Arising in 193 nm Laser irradiationof Graphite in Vacuo
R.J. Lade, K.N. Rosser, M.N.R. Ashfold (University of Bristol, United Kingdom)
We report results from a range of complementary studies of ArF (193nm) laser ablation of graphite and poly-(methylmethacrylate) (PMMA) in vacuo, and in low pressures of Ar, He and H2, designed to identify correlations between the properties o f the plume and the as deposited material. Investigations of the ablation plume itself include: wavelength dispersed optical emission spectroscopy (OES) of electronically excited species like H*, C*, C+*, C2* and CH*; time resolved studies of the evolution of selected chemiluminescent species (using narrow band interference filters in conjunction with a time gated CCD camera); and recoil velocity measurements (by time-of-flight methods) of the positive and neg ative ablated particles, all as a function of process condition. Films grown by pulsed laser deposition following 193 nm ablation of these target materials have been analysed by FTIR, SEM, laser Raman spectroscopy and their field emission properties inve stigated.
2:30 PM B6-4 Studies Of Laser Ablated Plumes For Fuzzy Controlled Film Deposition
J.G. Jones, R.R. Biggers, A.A. Voevodin (Air Force Research Laboratory)
Process control is a critical element in all deposition techniques. It is especially elusive in the versatile and efficient deposition technique known as pulsed-laser-deposition (PLD). Signal processed emissions from ionized species from copper components in the plume from a YBa2Cu3O7-x (YBCO) target and C targets are utilized for process control feedback. Manual and fuzzy-logic based regulation of laser energy based on this plume emission feedback resulted in improved film quality and repeatability of the PLD thin-film depositions.
2:50 PM B6-5 Tunable Magnetoresistance and Elevated Curie Points of La0.7√sub 0.3MnO3 Films Made by Pulsed Laser Deposition
F.J. Cadieu, L. Chen, T. Theodoropoulos, R. Rani (Queens College of CUNY)

Magnetoresistive La0.7√sub 0.3MnO3 polycrystalline films have been deposited by pulsed laser deposition that exhibit an extreme variability in the temperature of the resistance maximum as a function of the deposition conditions. Films have been deposited that exhibit the resistance maximum at temperatures ranging from 155 to 320 K as a function of laser pulse energy and shadowing conditions. An excimer laser using λ = 248 nm with pulse energies from 500 to 1250 mJ and λ = 193 nm with pulse energies from 400 to 650 mJ has been used to deposit mirror-like fine grained La0.7√sub 0.3MnO3 polycrystalline films. Films directly crystallized onto polycrystalline alumina substrates at 750 C and subsequently annealed at 750 C in 200 Torr oxygen were very highly (220) textured. Curie point measurements were deduced from hysteresis loops measured at different constant temperatures in a vibrating sample magnetometer with a high temperature oven. The temperature was sufficiently regulated that the loops could be repeatedly retraced at a given temperature. Ferromagnetic Curie points up to 398 K have been measured. This is 34 K higher than the value reported in Ref. 1 for bulk samples produced from powders. The magnetoresistance exhibits both low field and high field components. Suitable circuits have been constructed that give a temperature independent sensitivity of 60 mV/T for applied magnetic fields less than 0.015 T in the vicinity of room temperature.

This research is supported by DARPA and the Office of Naval Research under contract ONR-N00014-96-1-0767 and in part by PSC-CUNY FRAP.

1. Y. Moritomo, A. Asamitsu, and Y. Tokura, Phys. Rev. B 51, 16491 (1998).

3:30 PM Invited B6-7 Laser Deposition of Hard Carbon Coatings
D. Martin (Bayerische Motoren Werke AG, Germany)

The use of the laser-induced vacuum arc technique (laser arc) to deposit thin films in a large scale industrial process is described.

The deposition method is based on a pulsed arc discharge ignited by a laser pulse between an anode and a rotating cylindrical cathode consisting of the material to be deposited. By using a pulsed laser, the motion of the arc spot on the cathode can be controlled in position, velocity and time. To make the deposition method efficient for industrial applications, the deposition window of a small scale research coating unit1 with a size of about 100cm2 has been scaled up to around 1000cm2. The industrial version allows the coating of larger batches of up to several 100 components (few 10cm2) with independent two- or three-fold rotation.

The mechanical and tribological properties of the films obtained from the laboratory unit have already been described1. The industrial equipment allows a wider variation of the coating parameters in order to optimize the film properties for a particular application. The laser arc technology described allows the deposition of thin films at very low temperatures, so that the coatings of temperature sensitive materials and of engine components with high quality films is now possible.

Examples of the application of laser arc deposited films will be presented.

1 Scheibe, Drescher, Schultrich, Falz, Leonhardt and Wilberg in Surface and Coatings Technology 85(1996)209-214

4:10 PM B6-9 Ceramic Thin Film Deposition by Nanosecond, Picosecond and Femtosecond Lasers
R. Teghil (University of Basilicata, Italy); A. Giardini Guidoni, C. Flamini (University of Rome I, Italy); M. Ricci (University of Basilicata, Italy); V. Marotta (National Research Council, Italy)
The study of ceramic coatings has become an increasing area of chemical interest due to several applications in many fields. Metal oxide coatings are widely used, for example, as antireflecting and high refraction index materials for optical application or diffusion barriers in microelectronics as well as protective layers against aggressive media. Applications in liquid crystal displays, solar cells and gas sensors have also been exploited. Oxide films suitable for electrochemical cycling are also used in the production of the cathode materials in rechargeable batteries. An attractive choice for preparation of these films is the reactive pulsed laser ablation deposition (RPLAD). Pulsed laser ablation has been applied successfully, by us, in the past to deposit many materials as semi and superconductors, nitrides and oxides. This technique relies on photoablation of pure elements or a mixture of materials with simultaneous exposure to a reactive atmosphere. In case of oxides reactions between the laser vaporised metals and oxygen lead to the formation of intermediate complexes and finally to oxide thin films. Recently experiments on laser ablation of solid targets with short pulse lasers have been performed and the advantages of use of femtosecond and picosecond lasers on materials processing have been demonstrated. In this paper we present results on laser ablation and deposition of ceramic materials (oxides, carbides, nitrides) by femtosecond, picosecond and nanosecond lasers. The dynamics of particle emission and velocity distribution is studied by mass spectrometry and optical emission and imaging. The characteristics of the films deposited in the different regimes are compared and discussed.
4:30 PM B6-10 Laser-induced Surface Modifications of Uncoated and Alumina Coated WC-Co Substrates
K.E. Khor, A.P. Malshe, S.N. Yedave (Materials and Manufacturing Research Laboratory (MRL), University of Arkansas); D.G. Bhat (UES, Inc.)
Preliminary study showed the possibility of efficient cleaning of damaged surface of the coated cemented carbide tools. In this research, we have investigated the interaction of UV laser radiation with uncoated and alumina coated WC-Co substrates. The present work goes deeper into an understanding of the laser:material interaction. A pulsed UV excimer laser at 193 nm at various energy densities has been used for the surface modifications. We have explored the influence of various laser parameters on microstructural, chemical, and mechanical surface modifications using scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), and other related analytical techniques. The fundamental understanding gained in the study is instrumental in designing the processes for the machining of hard-to-machine materials.
4:50 PM B6-11 Magnetron Assisted Pulsed Laser Deposition of W-C and W-C-S Coatings
J.P. Neill, A.A. Voevodin, J.S. Zabinski (Air Force Research Laboratory)
Magnetron assisted pulsed laser deposition of nanocomposite coatings in the W-C and W-C-S material systems is considered. Pulsed laser ablation was used to produce highly energetic carbon plasma plumes, while magnetron sputtering was used to produce fluxes of W and W-S plasmas. These plasmas were intersected on the steel substrate surface to form wear protective nanocomposite coatings. Initially, coatings consisted of nanocrystalline WC grains embedded in DLC matrix were prepared. They were further modified with the addition of sulfur to form WS2 phase, improving friction and wear characteristics of the coatings. This resulted in the fabrication of three phase composites, consisting of nanocrysalline WC, WS2 and amorphous DLC. The deposition process of these coatings is analyzed. The importance of high energy laser carbon plumes for the formation of nanocrystalline materials at low substrate temperature is highlighted. Methods for coating stoichiometry control and regulation of crystallite sizes are discussed.
Time Period TuA Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF1999 Schedule