Papers

AVS1997 Session VM-MoA: Pulsed Laser Ablation and Ion Beam Processes

Monday, October 20, 1997 2:00 PM in Room F

Monday Afternoon

Start	Invited?	Item
2:00 PM		VM-MoA-1 Vacuum Arc Broad Metal Ion Beams Techniques TAMEK for Material Surface Modification A. Tolopa (Applied Physics Institute, Ukraine Academy of Sciences) This paper reviews the development of vacuum arc metal ion sources and their application to material surface modification. The versatile, compact vacuum arc TAMEK source operated in frequency-pulsed mode is capable of generating a large spot area of 300-2000 cm² metal ion beams for ion implantation E_i<200 keV, dD_i/dt<10¹⁶ ion/cm²/min., or ion deposition dH/dt<50- 200 nm/min. If desired, metal ion implantation, ion deposition, or metal ion beam assisted deposition (IBAD) can be performed without switching off the source. TAMEK source considerably improves IBAD treatment by means of alternation of the ion implantation and ion deposition and provides coatings both on metals and dielectric materials with deeper mutual mixing at low target temperature and simple surface preparation before treatment. TAMEK-M sources operated in pulsed t=1-5 mks mode, U_accel<100 kV, I_i<5 kA are used for increasing microhardness in subsurface layers up to 150 mkm thick after several pulses with an energy input into the surface dW=2-5 J/cm². This permits TAMEK-M source to be used for the treatment of precision and small size products, e.g., drills with diameter smaller than 1-3 mm. TAMEK sources can be successfully used in conventional fields of ion implantation and physical vapor deposition, and some TAMEK applications for treatment of metals, ceramics, glass, polymers are also shown, e.g., tools, construction materials, electrical contacts and electrodes, mirrors, etc. Production potentiality of vacuum arc and other progressive ion sources is also presented. The economical situation does not allow to apply new techniques in the FSU, and we hope that to combine USA and FSU activity it will be possible to apply vacuum arc metal ion sources in world industry, as it was done with the vacuum arc PVD method.
2:20 PM		VM-MoA-2 Improvement of Tribological Properties Using Pulsed High Power Ion Beams D.Cowell Senft, T.J. Renk, M.T. Dugger (Sandia National Laboratories); K.S. Grabowski (Naval Research Laboratory) We report on enhanced tribological properties due to rapid melt and resolidification of surface alloy layers by pulsed high power ion beams. The treated samples are produced at the RHEPP-1 facility at Sandia National Laboratories (.5 MV, 0.5-1 ms at sample location, <10 J/cm2, 1-5 mm ion range). We have treated and tested 440C and 15-5 steel as well as coated Ti samples in which beam treatment is responsible for surface mixing. Tribological testing of these samples is by a linear reciprocating tribometer using a ball-on-flat geometry. Changes in the treated layers are characterized by nanoindentation hardness testing, X-ray diffraction, and optical profiling analysis of the resulting topography. Treated layer thicknesses range from 2-5 microns. Treatment of 440C steel has resulted in increased durability, reduction in size of second phase particles, and other microstructural changes. Hardness of treated 440C increases with ion beam fluence and differs between epoxy-filled groove flashover and MAP gas breakdown anode ion sources. Ion beam treatment of Ti-Pt and Ti-Nb co-sputtered overlayers on Ti substrates is shown to increase the durability of these surfaces over untreated Ti. The effect of the surface mixing on durability and hardness of has been examined as a function of incoming ion species and the number of treatment pulses. In some cases the hardness of the Ti surface has been improved by a factor of 3 by surface mixing. *This work was supported by the United States Department of Energy under Contract DE-AC04-94AL85000. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy.
2:40 PM		VM-MoA-3 Pulsed Electron-Beam Technology for Surface Modification of Metallic Materials D.I. Proskurovsky, V.P. Rotshtein (Institute of High Current Electronics, Russia); V.A. Shulov (Moscow Aviation Institute, Russia); G.E. Ozur (Institute of High Current Electronics, Russia); Yu.F. Ivanov (Tomsk State University of Architecture and Building, Russia); R.G. Buchheit (Sandia National Laboratories); A.B. Markov, D.S. Nazarov (Institute of High Current Electronics, Russia) The surface modification of materials by their fast melting and subsequent cooling is a promising technique for improving the performance of articles. To make this technology practical, pulsed intense laser, ion, electron and plasma beams are used. We have developed a technology for pulsed e-beam surface modification of materials, based on the use of original sources of low-energy high-current electron beams (LEHCEBs). Electron guns with a plasma anode and an explosive-emission cathode are used in this type of sources. The sources have the following parameters: eV = 10-40 keV, T = 0.5-5 µs, W = 0.5-40 J/cm², S = 10-50 cm². These sources are simple in design, low-cost, X-radiation safe, and simple to service. We have investigated the regularities of the modification of the structure and properties of the surface layers of steels, Ti- and Al- alloys, and hard alloys exposed to LEHCEBs in various modes. It has been shown that the quenching from melt and the strain processes in the substrate result in the formation of high-strength states that provide substantial enhancement of the strength properties of the material. The liquid-phase dissolving of second phases improve significantly the corrosion resistance. The results obtained are interpreted based on the data of a numerical simulation of temperature and stress fields. It has also been shown that using LEHCEBs it is possible to produce high concentrated surface alloys, to clean and smooth the surface. In their totality, these results suggest that this type of treatment shows promise for the improvement of the performance of machine parts and tools.
3:20 PM		VM-MoA-5 Metal Vapor Source with High Intensity Flow for Thin Film Technology A.S. Zolkin (Novosibirsk State University, Russia) The creation of metal vapor sources with high vapor jet intensity is connected with the solution of numerous problems¹. The main attention is paid to stabilization of expansion parameters: pressure and temperature of the vapor flow. Stracturelly, new source consists of two basic part: a crucible with metal and special vapor superheater (thermal radiation heater) where the liquid drops move in a circle for effective evaporation in it. Vapor is superheated before expansion in order to decrease or eliminate condensation in the nozzle region. These source allow to handle the characteristics of vapor. The intensity of the metal flow (Mg) from the nozzle is approximately 10²³ atom/cm² near the nozzle. The design and testing of a source for Ionized Molecular Beam (IMB) method are described in detail. The vaporized atoms (Ag,Pb,Mg) are partially ionized by electrons (ionizer with radial convergent beam is developed and described in detail) at the crusible exit, then accelerated in electric field up to 10 kV and deposited at 200 nm/min (and more) on the substrate of HTSC/Y-Ba-Cu-O film, CdHgTe cristals, metals, polimers. The measurements of the molecular beam have been performed by means of the mass-spectr. and electrostatic energy analyzer. In the region, near P=510⁴ Pa the clusters Mg_n (3 < n < 10) have been registered. Thin (100-200 nm) and thick films with high adhesion, density and low-resistance contacts Ag/Y-Ba-Cu-O (10^-5 - 10^-8 Ohmcm²) were fabricated by IMB. The surface of the films was analyzed by SEM(SE,BSE) with computer analyzer. The Mg films on the glass, metals, mica, ceramics, Si, Ge were fabricated by IMB and showed high corrosion-resistant. ¹A.S.Zolkin. Metal vapor Sources for Scientific Research and thin film Technology. A Review. J.Vac.Sci. and Tech. May/June, 1997 (is accepted to publish).
3:40 PM		VM-MoA-6 Ion Beam Sputter Deposition and Characterization of Aluminum Oxide and Aluminum Nitride Thin Films for Gap Dielectrics and Spin Tunneling Devices A.V. Hayes, K. Williams, H. Hegde, B. Druz, V. Kanarov, S. DiStefano, A. Boccanfuso (Veeco Instruments); R.J. Gambino (State University of New York, Stony Brook) The production and characterization of high quality Aluminum oxide and Aluminum nitride ultrathin films for application as gap dielectrics and spin tunneling devices is described. The dual ion beam deposition system incorporates two RF 1.8 MHz inductively coupled ion beam sources. This approach has major advantages for reactive deposition and production of low defect density coatings¹. One of the ion sources is used to sputter the deposition target, while the other is aimed at the substrate and is used as an ion assist source. For most of the work, an aluminum target is used and the oxide or nitride is formed reactively at the substrate surface by flowing oxygen or nitrogen, respectively, through the ion assist source. This allows for relatively high but still controllable deposition rates (10 - 20 nm/min) while achieving less than 3% nonuniformity over substrates up to 200 mm diameter. The deposited films have been characterized by physical, optical and electrical methods and by X-ray diffraction. The optical characterization (n and k) indicates the quality of the films and provides accurate indication of the film thickness down to the subnanometer levels. A multiangle multiwavelength ellipsometer was used for this analysis. High quality aluminum oxide films with no measurable extinction coefficient have been produced. Film stress in AlN coatings was characterized. Both the index of refraction of the films and stress levels were found to be controllable over a fairly wide range by adjusting the deposition parameters. ¹S.P. Vernon, et al, Optical Society of America Trends in Optical Photronics, 4 (1996).
4:00 PM		VM-MoA-7 Femtosecond Laser Ablation Processes and Deposition of Thin Films D.R. Alexander, D.W. Doerr, S.L. Rhode (University of Nebraska, Lincoln) A Ti:sapphire regenerative amplified femtosecond laser operating at a central wavelength of 795 nm with a pulse length of 150 fs is used to ablate both metal as well as glass materials. Results will be presented on the deposition of plasma plumes on silicon substrates. A number of different materials have been deposited and the ablated surface characterized. In this particular paper the results for tungsten and quartz will be emphasized. Results are also present on using the femtosecond laser along with the ion sputtering to produce unique magnetic films. The femtosecond laser is thought to produce a very high precursor flux of energetic materials for the later accumulation of ion sputtered ions. Results of the films produced and the characteristics of the sputtered surface will be presented. In addition, we will present results on the femtosecond machining of ultra thin quartz crystals which are 75 microns thick. Results indicate that it is possible to machine very thin materials with femtosecond lasers with minimum amount of surface damage to the remaining materials.
4:40 PM		VM-MoA-9 Structural and Electrical Properties of Biaxially Oriented Conductive La_{0.5√sub 0.5}CoO₃ Thin Films on SiO₂/Si Q.X. Jia, P. Arendt, J.F. Groves, S.R. Foltyn (Los Alamos National Laboratory) There have been many recent studies on the deposition and characterization of conductive La_{0.5√sub 0.5}CoO₃ (LSCO) thin films due to their potential applications as bottom electrodes for ferroelectric thin film capacitors and sensors. For a number of applications, well textured or epitaxial LSCO thin films are preferable. We have grown biaxially textured LSCO thin film on technically important SiO₂/Si substrate by pulsed laser deposition, where yttria-stabilized zircornia (YSZ) produced by ion-beam-assisted-deposition (IBAD) is used as a template to enhance the texture of LSCO on SiO₂/Si. The degree of in-plane alignment of LSCO is directly related to the quality of IBAD-YSZ. The smaller the value of full width at half maximum of the (220) IBAD-YSZ peak, the higher the crystallinity of the LSCO film. Electrical measurement shows that the biaxially oriented LSCO is highly conductive at room-temperature. The electrical and structural properties of the LSCO will be discussed in detail with respect to the quality of IBAD-YSZ.
5:00 PM		VM-MoA-10 Growth and Characterization of Epitaxial SrRuO₃ Thin Films on SrTiO₃ MgO and Al₂O₃ by Pulsed Laser Ablation. C.L. Chen, Z.J. Huang, Q.D. Jiang, Y Chao, Z.H. Zhang, W.N. Kang, L.M. Dezaneti, Unknown Sun, Y.Y., C.W. Chu, W.K. Chu (University of Houston) Highly conductive metallic oxide thin films of SrRuO₃ with single crystalline quality have been grown on (001), (011) and (111) SrTiO₃, (001) MgO and (012) Al₃O₃ by using pulsed laser deposition. The as-grown films have systematically been characterized by X-ray diffraction, pole figure study, Rutherford back scattering, and resistivity measurements. The films have a [00l] orientation with an in-plane relationship of [110]_SRO //[100]_STO on (001) SrTiO₃ and [110]_SRO //[100]_STO on (001) MgO, and have a [112] oriented normal to the substrate surfaces on (011) and (111) SrTiO₃ and (012) Al₃O₃. They have excellent metallic behavior with room temperature resistivity of ~ 310 mW-cm and a residual resistance ratio of about 7 at 4.2 K. A clear ferromagnetic transition at ~ 147 K was detected by resistivity and magnetic and magnetic-opital measurements on all of the films. However, the transition becomes blurred as the density-of-point defects increases in the films following a 400 KeV proton irradiation with an accumulative dose up to ~ 6.0x10¹⁶ ions/cm².