SPECIAL ISSUE PAPERS
Ion and laser beams are employed in a wide variety of materials ranging from doping, surface modification, film synthesis to development of new materials. This conference brought in a wide variety of related issues including ultra-shallow junction formation and ion-beam synthesis of thin films. In the area of laser processing, special emphasis was given to hard materials such as diamond, diamond-like-carbon and carbon nitride thin films. This symposium was organized by the Thin Films and Interfaces Committee of TMS. The guest editors would like to thank all the participants for this conference.
University of Florida
Oak Ridge National Library
Special Issue Editors
Effect of Ion Dose Rate on Rapid Laser Annealing of Implanted GaAs
K. MASUDA, K. MURAKAMI, and H.Y. NAN
Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305, Japan.
Short-duration laser annealing of localized regions on P+ ion-implanted GaAs wafers has been examined for various doses and dose rates by micro-Raman scattering and Rutherford backscattering measurements. Time required for complete annealing of ion-induced defects varies from 5 ms to 1 s, corresponding to the implanted dose and rate. It is found that the amount of produced defects is enhanced by implantation with higher dose rates and that defects produced with higher dose rates are more easily annealed by the laser irradiation during short durations within a certain dose range.
Ion-implanted GaAs, micro-Raman scattering, rapid laser annealing, Rutherford backscattering (RBS)
Mechanism of Defect Formation in Low-Dose Oxygen Implanted Silicon-on-Insulator Material
S. BAGCHI,1 J.D. LEE,1 S.J. KRAUSE,1 and P. ROITMAN2
1--Department of Chemical, Bio and Materials Engineering, Arizona State University, Tempe, AZ 85287. 2--National Institute of Standards and Technology, Gaithersburg, MD 20899.
The defects and microstructure of low-dose (<0.7 X 1018 cm-2), oxygen-implanted silicon-on-insulator (SIMOX) material were investigated as a function of implant dose and annealing temperature by plan-view and cross-sectional transmission electron microscopy. The threading-dislocations in low-dose (0.2~0.3 X 1018 cm-2), annealed SIMOX originate from unfaulting of long (~10 µm), shallow (0.3 µm), extrinsic stacking faults generated during the ramping stage of annealing, As dose increases, the defect density is reduced and the structure of the buried oxide layer evolves dramatically. It was found that there is a dose window which gives a lower defect density and a continuous buried oxide with a reduced density of Si islands in the buried oxide.
Dislocation half-loop, multiply-faulted defect, silicon islands, SIMOX, stacking fault pyramid, threading dislocation
Thin Film Silicon on Insulator Substrates and Their Application to Integrated Circuits
S.R. WILSON,1 T. WETTEROTH,1 S. HONG,1 H. SHIN,1 B.-Y. HWANG,2 J. FOERSTNER,2 M. RACANELLI,2 M. HUANG,2 and H.C. SHIN2
1--Materials Research and Strategic Technologies, Motorola Semiconductor Products Sector, Mesa, AZ 85202. 2--Advanced Custom Technologies, Motorola Semiconductor Products Sector, Mesa, AZ 85202.
Thin film silicon on insulator (TFSOI) devices have been studied for years. The advantages of TFSOI devices include: a reduction in junction capacitance, potentially lower junction leakage, a simpler process, and many other well documented advantages. However, other than some military/space applications, TFSOI circuits are not currently available in commodity products. One of the reasons TFSOI circuits are not wide spread is that there has not been a reliable source of TFSOI substrates. Recently, however, several suppliers of TFSOI substrates, both SIMOX and bonded and etch-backed wafers (BESOI), have made significant improvements in their material quality and are increasing capacity to meet expected demands. In this paper, we will discuss the major materials issues and how these issues impact either the TFSOI device performance or the process integration. In addition, we will present gate oxide integrity data as well as device results from these TFSOI substrates.
Integrated circuits, Si, thin film silicon on insulator
Synthesis of Metastable Carbon-Silicon-Nitrogen Compounds by Ion Implantation
C. USLU,1 B. PARK,1 and D.B. POKER2
1--School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332. 2--Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
The feasibility of carbon-silicon nitride formation (-Si1.5C1.5N4, the homologue of equilibrium -Si3N4 or hypothetical -C3N4) has been investigated by high dose N+ implantation into polycrystalline -SiC (cubic phase). Thin films were formed using 100 keV implantations with varying ion doses and target temperatures. X-ray diffraction with a position-sensitive detector and cross-sectional transmission electron microscopy revealed that the as-implanted surfaces contained ~0.1 µm thick buried amorphous layers. Rutherford backscattering spectroscopy showed that the peak concentration of nitrogen saturated up to approximately 54 at.% with increasing doses, suggesting formation of a new phase.
Carbon-silicon nitride, ion-implantation, SiC
Optical Properties of Multicomponent Nanometer Dimension Metal Colloids Formed in Silica by Sequential Ion Implantation of In and Ag and In and Cu
T.S. ANDERSON,1 R.H. MAGRUDER III,1 R.A. ZUHR,2 and J.E. WITTIG1
1--Department of Applied and Engineering Sciences, Vanderbilt University, Nashville, TN 37235. 2--Surface Modification and Characterization Facility, Solid State Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
A series of nanometer dimension colloids in silica have been fabricated by sequential implantation of Ag and In, and a series by sequential implantation of In and Cu. Energies of implantation were chosen using TRIM 89 to overlay the depth distributions of the sequentially implanted ions. The implanted layers were characterized using Rutherford backscattering spectroscopy, transmission electron microscopy, and optical spectroscopy. Nanometer dimension metal multicomponent colloids were formed. The depth distribution, particle size, and optical response of the composites were found to depend strongly on the ion species implanted and the relative ratio of the ion species. The optical responses are correlated with composition of the multicomponent nanoclusters.
Ion implantation, metal colloids, silica
The Development of Biaxial Alignment in Yttria-Stabilized Zirconia Films Fabricated by Ion Beam Assisted Deposition
KEVIN G. RESSLER, NEVILLE SONNENBERG, and MICHAEL J. CIMA
Ceramics Processing Research Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139
Yttria-stabilized zirconia (YSZ) films were deposited using ion assisted, electron beam deposition (IBAD) on Pyrex, quartz, Hastelloy, and polycrystalline zirconia substrates. Film orientation was studied as a function of IBAD fabrication conditions. Film texture from several populations of biaxially aligned grains has been observed. The ion beam is shown to induce biaxial alignment of all grain orientations. Specifically, grains with (200), (311), and (111) normal to the substrate surface are biaxially aligned. The ion beam induces biaxial alignment at all angles of incidence, not just those corresponding to YSZ channeling directions. The development of (200) biaxial alignment on Pyrex is examined as a function of thickness. Biaxially aligned IBAD YSZ films were deposited on amorphous and polycrystalline substrates without active heating. Biaxial alignment development with IBAD is shown to be consistent with a previously proposed growth and extinction model.
Biaxial alignment, ion beam assisted deposition (IBAD), yttria-stabilized zirconia (YSZ)
Visible and Infrared (1.54 µm) Emission From Er-Implanted Porous Si For Photonic Applications
FEREYDOON NAMAVAR1 FENG LU,2 CLIVE H. PERRY,2 ANNMARIE CREMINS,3 NADER KALKHORAN,3 and RICHARD A. SOREF4
1--Spire Corporation, Bedford, MA 01730. 2--Northeastern University, Boston, MA 02115. 3--Spire Corporation, Bedford, MA 01730. 4--Rome Laboratory, Hanscom AFB, MA 01731.
This paper explores the challenges faced in developing efficient room temperature porous Si-based light emitting diodes. We experimentally demonstrate that porous Si is an excellent host material for erbium ions to emit strong, room temperature, sharp-line luminescence at 1.54 µm. A comparison of photo luminescence data for erbium implanted samples of bulk Si, porous Si, and quartz indicate that quantum confinement likely enhances the erbium IR luminescence efficiency. Due to the 650 to 850°C annealing, it is unlikely that the environment of erbium in our samples is amorphous Si.
1.54 µm emission, erbium, porous silicon, room temperature luminescence, Si-based light emitting device
Synthesis of Low Resistivity Complex Oxides on MgO Using Pt as Buffer Layer
P. TIWARI,1,2 X.D. WU,1 S.R. FOLTYN,1 I.H. CAMPBELL,1 Q.X. JIA,1 R.E. MUENCHAUSEN,1 D.E. PETERSON,1 and T.E. MITCHELL3
1--Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, NM 87545. 2-- Current address: IBM Microelectronics, 1000 River St., Essex Junction, VT 05452. 3--Center for Materials Science, Los Alamos National Laboratory, Los Alamos, NM 87545.
Highly crystalline SrRuO3 (SRO) and La0.5Sr0.5 CoO3 (LSCO) thin films were deposited on (100) Pt/ MgO by pulsed laser deposition. The films were mainly (001) textured normal to the substrate surface with a high degree of in-plane orientation with respect to the substrate's major axes. These films were characterized using x-ray diffraction, Rutherford backscattering, four-point probe resistivity measurement, and transmission electron microscopy. The room temperature resistivity for LSCO and SRO films on Pt/MgO was found to be ~35 and ~40 µ-cm, respectively. An ion beam minimum channeling yield of ~43% and ~33% was obtained for LSCO and SRO films, respectively. The interface between Pt and oxide was found to be smooth and free from any interfacial diffusion. This result showed that high-quality low resistivity oxide thin films can be deposited on Pt.
Low resistivity oxide, Pt/MgO, pulsed laser deposition (PLD), thin films
Pulsed Laser Deposition and Physical Properties of Carbon Nitride Thin Films
Z. JOHN ZHANG, SHOUSHAN FAN, JINLIN HUANG, and CHARLES M. LIEBER
Division of Applied Sciences and Department of Chemistry, Harvard University, Cambridge, MA 02138.
Carbon nitride thin films were grown using an approach that combines pulsed laser deposition and atomic beam techniques. The composition and phases of the carbon nitride materials obtained from the reaction of laser ablated carbon and atomic nitrogen have been systematically investigated. The nitrogen composition was found to increase to a limiting value of 50% as the fluence was decreased for laser ablation at both 532 and 248 nm. Analysis of these experiments show that the growth rate determines the overall nitrogen composition, and thus suggests that a key step in the growth mechanism involves a surface reaction between carbon and nitrogen. Infrared spectroscopy has also been used to assess the phases present in the carbon nitride thin films. This spectroscopic measurement indicates that a cyanogen-like impurity occurs in films with nitrogen compositions greater than 30%. Investigations of the effects of thermal annealing have been carried out, and show that the impurity phase can be eliminated to yield a single phase material. In addition, systematic measurements of the electrical resistivity and thermal conductivity of the carbon nitride films were made as a function of nitrogen content. The implications of these results are discussed.
Carbon nitride, pulsed laser deposition, thin films
Thermal Expansion, Molar Volume and Specific Heat of Diamond from 0 to 3000K
ROBERT R. REEBER and KAI WANG
Department of Geology, University of North Carolina-CH, Chapel Hill, NC 27599-3315.
Thermal expansion is of both practical and theoretical importance and it together with specific heat is essential for predicting a thermodynamic equation of state. We utilize a semi-empirical quasi-harmonic model to evaluate available data for diamond. The model allows us to predict the thermal properties of the metastable diamond polymorph to 3000K. The approach consisting of a simplified frequency spectrum with several Einstein terms provides a convenient mathematical method where a minimum of empirical parameters represent the thermal property.
Diamond, lattice parameter, molar volume, specific heat, thermal expansion
Photolytic Deposition of Aluminum Nitride and Oxy-Nitride Films at Temperatures ¾350K
GOURI RADHAKRISHNAN and JEFFREY R. LINCE
Mechanics and Materials Technology Center, The Aerospace Corporation, P.O. Box 92957, Los Angeles, CA 90009.
Aluminum nitride and oxy-nitride thin films have been deposited on Si(100) substrates at temperatures of 300-350K by gas-phase excimer laser photolysis at 193 nm. The precursors used for this deposition process are trimethylamine alane and ammonia. The properties of these laser-deposited films were studied using scanning electron microscopy, energy dispersive x-ray analysis, and x-ray diffraction. X-ray photoelectron spectroscopy has been extensively used to provide information regarding the chemical compositions on the surface and in the bulk of these laser deposited films, as well as on the chemical states of the components of the films. Well-adhering, smooth, amorphous films of AlN are obtained at a substrate temperature of 350K using this technique.
AlN, laser photolysis, oxy-nitride thin films
Al,Al/C and Al/Si Implantations in 6H-SiC
MULPURI V. RAO,1 PETER GRIFFITHS,1 JASON GARDNER,1 O.W. HOLLAND,2 M. GHEZZO,3 J. KRETCHMER,3 G. KELNER,4 and J.A. FREITAS, JR.5
1--Department of Electrical and Computer Engineering, George Mason University, Fairfax, VA 22030. 2--Oak Ridge National Laboratory, Oak Ridge, TN 37831. 3--GE Corporate Research and Development, Schenectady, NY 12301. 4--Naval Research Laboratory, Washington, DC 20375. 5--SFA, Inc., Landover, MD 20789.
Multiple-energy Al implantations were performed with and without C or Si co-implantations into 6H-SiC epitaxial layers and bulk substrates at 850°C. The C and Si co-implantations were used as an attempt to improve Al acceptor activation in SiC. The implanted material was annealed at 1500, 1600, and 1650°C for 45 min. The Al implants are thermally stable at all annealing temperatures and Rutherford backscattering via channeling spectra indicated good lattice quality in the annealed Al-implanted material. A net hole concentration of 8 X 1018 cm-3 was measured at room temperature in the layers implanted with Al and annealed at 1600°C. The C or Si co-implantations did not yield improvement in Al acceptor activation. The co-implants resulted in a relatively poor crystal quality due to more lattice damage compared to Al implantation alone. The out-diffusion of Al at the surface is more for 5Si co-implantation compared to Al implant alone, where 5Si means a Si/Al dose ratio of 5.
Al, annealing, implantation, SiC
Deposition and Surface Treatment with Intense Pulsed Ion Beams
J.C. OLSON,1 H.A. DAVIS,1 D.J. REJ,1 W.J. WAGANAAR,1 R.W. STINNETT,2 and D.C. MC INTYRE2
1--Los Alamos National Laboratory, Los Alamos, NM 87545. 2--Sandia National Laboratories, Albuquerque, NM 87185.
Intense pulsed ion beams (500 keV, 30 kA, 0.5 µs) are being investigated for materials processing. Demonstrated and potential applications include film deposition, glazing and joining, alloying and mixing, cleaning and polishing, corrosion improvement, polymer surface treatments, and nanophase powder synthesis. Initial experiments at Los Alamos have emphasized thin-film formation by depositing beam ablated target material on substrates. We have deposited films with complex stoichiometry such as YBa2Cu3O7-x and formed diamond-like-carbon films. Instantaneous deposition rates of 1 mm/s have been achieved because of the short ion range (typically 1 µm), excellent target coupling, and the inherently high energy of these beams. Currently the beams are produced in single shot uncomplicated diodes with good electrical efficiency. High-voltage modulator technology and diodes capable of repetitive firing, needed for commercial application, are being developed.
Diamond-like-carbon films, film deposition, intense pulsed ion beams
Strain Evolution and Dopant Activation in P-Implanted Metastable Pseudomorphic Si(100)/Ge0.12Si0.88
D.Y.C. LIE,1 J.H. SONG,1 F. EISEN,1 M.-A. NICOLET,1 and N.D. THEODORE2
1--M/S 116-81, California Institute of Technology, Pasadena, CA 91125. 2--Motorola Inc., Mesa, AZ 85202.
A metastable Ge0.12Si0.88 layer 265 nm thick was deposited pseudomorphically on a Si(100) substrate and then implanted with 100 keV phosphorus ions at room temperature for doses of 5 X 1013/cm2 to 1.5 X 1015/cm2. The ions stop within the epilayer (projected range ~125 nm). MeV 4He backscattering/channeling spectrometry, transmission electron microscopy, and double-crystal x-ray diffractometry were used to characterize the damage and strain in the films. The samples were subsequently annealed in high vacuum from 400-800°C for 30 min at each temperature. For the nonamorphized samples (doses of 5 and 10 X 1013/cm2), most of the implantation-induced damage and strain disappear after annealing at 400-550°C, but the implanted P ions activate poorly. After annealing at 700-800°C, near complete activation is achieved but the strain relaxes. For the amorphized samples (dose of 1.5 X 1015/cm2), the amorphous GeSi regrows by solid-phase epitaxy and the dopants are ~100% activated after annealing at 550°C, but the regrown GeSi relaxes with a high density of dislocations. The strain relaxes more extensively upon annealing in an implanted sample than in a nonimplanted one, other conditions being equal. This effect is more pronounced at higher ion doses, probably due to the increased amount of damage introduced at high doses.
Dopant activation, implantation, silicon-germanium, solid-phase epitaxy, strain relaxation
SIMOX Research, Development, and Manufacturing
LISA P. ALLEN, THEODORE H. SMICK, and GEOFFREY RYDING
Ibis Technology Corporation, 32A Cherry Hill Dr., Danvers, MA 01923.
Research and development on SIMOX silicon-on-insulator material is rapidly increasing due to exciting applications for low power, low voltage, and advanced, high performance circuitry. Consistency in wafer uniformity and interface smoothness, reduction of metallic contamination, and a drive toward lower substrate cost have all contributed to the use of SIMOX as a starting substrate for production devices and circuits. Considerations for new implanter development, product material improvement, and worldwide market expansion are discussed.
Manufacturing, silicon-on-insulator, SIMOX
Implantation of Si under Extreme Conditions: The Effects of High Temperature and Dose on Damage Accumulation
O.W. HOLLAND,1 LING XIE,1 BENT NIELSEN,2 and D.S. ZHOU1
1--Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, TN 37831-6048. 2--Brookhaven National Laboratory, Upton, Long Island, NY 11973.
The accumulation of lattice damage in Si(100) during ion irradiation at extreme dose and temperature was investigated. Irradiation above the ion-induced, crystal-to-amorphous transition temperature (~200°C) enabled damage growth to be studied to arbitrarily high dose. Electron microscopy and Rutherford backscattering spectrometry were used to characterize the growth of damage under these extreme conditions, as well as its microstructural evolution. These observations are correlated both to irradiation conditions and the effects of ion-solid chemistry associated with the use of atomic ions dissimilar to the bulk atoms. These chemical effects are isolated by comparing results for Si+- with P+- ion irradiations, and As+- with Ge+- irradiations. Each combination includes an isoelectric and dopant ion of nearly identical mass for separating out the effects of the ion-solid chemistry. A mechanism to account for the formation of the ion-induced morphology under extreme irradiation conditions is presented.
Ion implantation, lattice damage, Si
Dose-Rate Effects in Silicon-Implanted Gallium Arsenide From Low to High Doses
C. JASPER,1 R. MORTON,2 S.S. LAU,2 T.E. HAYNES,3 J.W. MAYER,4 and K.S. JONES5
1--Compound Semiconductor One, Motorola, Inc., Tempe, AZ 85202. 2--Department of Electrical and Computer Engineering, University of California, La Jolla, CA. 3--Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN. 4--Department of Chemical, Bio and Materials Engineering, Arizona State University, Tempe, AZ. 5--Department of Materials Science and Engineering, University of Florida, Gainesville, FL.
For implantation of silicon dopant into gallium arsenide, sheet resistance and damage increase as the ion dose rate increases in the high-dose regime (>5.0 X 1013 cm-2). But, in the low-dose regime (<5.0 X 1012 cm-2), although damage still increases with dose rate, the sheet resistance decreases. This qualitative difference implies that there must be a crossover point between the low- and high- dose regimes in the effect of damage and defect formation on dopant activation. This paper describes experiments in which damage and silicon dose were independently varied through the crossover point. Thermal wave, ion channeling, Hall effect measurements, and transmission electron microscopy were used to characterize structural and electrical changes that occur near the crossover. In GaAs implanted with silicon (29Si+) at doses between 3 X 1012 and 6 X 1013 cm-2, it is shown that electrical activation for low dose rates first begins to exceed that for high dose rates at a dose of 2 X 1013 cm-2. Rapid growth of Type I dislocations also begins near this same dose, suggesting that there may be a link between defect formation and the crossover to negative dose-rate effects in the high-dose regime.
Electrical activation, GaAs, implantation, implantation damage
Low Energy Ion Bombardment Effects in Gold/Aluminum Nitride/Silicon Junctions
T. STACY, B.Y. LIAW, and A.H. KHAN
Department of Electrical and Computer Engineering, University of Missouri, Columbia, MO 65211.
Aluminum nitride was grown on n-type silicon substrates utilizing chemical vapor deposition. Low energy (5 keV) ion bombardment of methane, argon, and nitrogen was investigated as a method for surface modification prior to metal deposition. Gold contacts were deposited on ion bombarded and as-grown material and a back ohmic contact was formed to the silicon. Current-voltage measurements indicate that bombarded regions exhibit rectifying behavior. Interpretation of these results is presented with comparison of measurements on areas with and without implantation. Samples were also characterized with Raman scattering, x-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), and photoelectric measurements.
Aluminum nitride, ion bombardment, rectifying, Schottky barrier
A Study of the Ion Implantation Damage and Annealing Behavior in GaSb
S. IYER,1 R. PARAKKAT,1 B. MANGALAM,1 B. PATNAIK,2 M. FALVO,2 and N. PARIKH2
1--Department of Electrical Engineering, North Carolina A&T State University, Greensboro, NC 27411. 2--Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599.
The effects of damages produced by implantation of Te, Er, Hg, and Pb ions into undoped (100) GaSb single crystals and their recovery by Rutherford backscattering (RBS)/channeling were investigated. The implantations with dosages in the range of 1013 to 1015 ions/cm2 were carried out at liquid nitrogen temperature, at energies corresponding to a projected range of 447Å in GaSb. Near surface damage equivalent to that of an amorphous layer was observed even at lower doses. The samples were annealed at 600°C for different durations, with the Te implanted sample of the lowest dosage exhibiting the best recovery (Xmin = 11%) compared to others. This value of Xmin nearly corresponds to that of the virgin crystal. Examination of the surface morphology as a function of mass, dosage, and annealing duration revealed that it was strongly influenced by the dosage of the implanted ions.
Annealing, GaSb, ion implantation damage
Transient Plasma Shielding Effects During Pulsed Laser Ablation of Materials
RAJIV K. SINGH
Materials Science and Engineering, University of Florida, Gainesville, FL 32611-2066.
The absorption of laser energy by the plasma during pulsed laser deposition of thin films has been analyzed theoretically. The amount of laser energy absorbed in the plasma termed as the "plasma shielding factor" is a function of the incident laser wavelength, and time dependent plasma dimensions and electron density. Due to time varying parameters, a quantitative analysis of the plasma absorption is difficult. A model which takes into account the absorption of laser energy by the plasma has been developed. In this model, the time-dependent plasma dimension is replaced by the time dependent ablation depth. Using simulated absorption coefficient values, the ablation characteristics of silicon and high Tc superconductors are computed and compared with experimental results. The plasma shielding factor was found to vary approximately linearly with absorbed laser energy. The calculations also showed that the plasma shielding was strongly dependent on the laser fluence but varies very weakly with the simulated plasma absorption coefficient values. Experimental results on plume shielding showed good agreement with the calculations.
Ablation, plasma shielding, pulsed laser deposition
Study of High-Quality Epitaxial YBCO Thin Films Grown Directly on Y-Cut LiNbO3
P. TIWARI, X.D. WU, S.R. FOLTYN, R.E. MUENCHAUSEN, P.N. ARENDT, I.H. CAMPBELL, Q.X. JIA, D.E. PETERSON, and T.E. MITCHELL
Superconductivity Technology Center, Center for Materials Science, Los Alamos National Laboratory, Los Alamos, NM 87545.
Pulsed laser deposition was used to deposit high-quality YBa2Cu3O7-[Delta] (YBCO) thin films directly on y-cut LiNbO3 substrates. The as-deposited YBCO films had a high degree of in-plane orientation and showed superconducting transition temperature (Tco) at 91K with a transition width of less than 1K. Transport critical current densities were found to be ~106 A/cm2 at 77K and zero field. An ion beam minimum channeling yield of 16% was obtained for YBCO films, indicating high crystallinity. High-resolution transmission electron microscopy studies showed that the interface between the film and the substrate was quite smooth and free from interfacial interdiffusion. The defects in thin films are also identified. The work showed that high-quality high Tc thin films can be deposited directly on LiNbO3. Novel devices based on the properties of both YBCO and LiNbO3 could be realized based on these results.
High resolution transmission electron microscopy (HRTEM), pulsed laser deposition, YBCO
Excimer Laser-Assisted Planarization of Thick Diamond Films
RAJIV K. SINGH and DONG-GU LEE
University of Florida, Department of Materials Science and Engineering, Gainesville, FL 32611.
The planarization of polycrystalline diamond films is criticalfor a large number of industrial applications. We have investigated a laser-assisted method for planarization of thick diamond films. This method is based on the application of excimer laser combined with simultaneous rotation of the sample. Thick diamond films (average surface roughness: ~20 µm and thickness ~500 µm) were fabricated by plasma jet chemical vapor deposition process. The planarization of diamond films was found to be critically dependent on the angle of incidence of laser beam. Smoother surfaces were obtained at higher incidence angles ( = 80°). However, by combination of sample rotation with laser irradiation at higher incidence angles ( = 80°), maximum surface planarization was achieved. Under optimum conditions, the surface roughness of the samples were reduced from 20 to 0.1 µm. The mechanisms for surface planarization of thick diamond films are discussed.
Diamond, laser-assisted method, planarization, surface roughness
Laser Processing of BN and AlN Films
J. NARAYAN, H. WU, and R.D. VISPUTE
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7916.
We have formed cubic boron nitride (c-BN) and hexagonal aluminum nitride (h-AlN) using novel pulsed laser processing methods. To synthesize c-BN, the boron target was evaporated by pulsed KrF laser ( = 248 nm) with simultaneous bombardment with nitrogen ions. On the other hand, epitaxial deposited h-AlN on silicon and sapphire substrates was accomplished by pulsed laser evaporation of AlN target. The films of c-BN were polycrystalline on Si(100) and Si(111) substrates, and high-quality epitaxial h-AlN film was grown on (0001) sapphire with a following in-plane alignment of AlN  || Al2O3  and AlN  || Al2O3 . This is equivalent to 30° rotation of the film with respect to the substrate in the basal c-plane. The absorption edge measured by ultraviolet-visible spectroscopy for the epitaxial AlN film was sharp and the band gap was found to be 6.1eV. Details of microstructure-property correlation of these films and possible applications are discussed.
c-BN, h-AlN, pulsed laser processing, pulsed laser evaporation
Pulsed Laser Deposition of Titanium Nitride and Diamond-Like Carbon Films on Polymers
R.D. VISPUTE, J. NARAYAN, and K. JAGANNADHAM
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7916.
We have investigated the deposition of titanium nitride (TiN) and diamond-like carbon (DLC) films on polymethylmethacrylate (PMMA) substrates using pulsed laser deposition (PLD) technique. The TiN and diamond-like films were deposited by laser ablation (KrF excimer laser = 248 nm, pulse duration ~25 X 10-9 s, energy density ~2-15J/cm2) of TiN and graphite targets, respectively, at room temperature. These films were characterized by transmission electron microscopy, scanning electron microscopy, x-ray diffraction, Auger electron spectroscopy, UV-visible absorption spectroscopy, and Raman spectroscopy. The TiN films were smooth and found to be polycrystalline with average grain size of 120Å. The diamond-like carbon films were amorphous with a characteristic Raman peak at 1550 cm-1. The TiN films are highly adherent to the polymer substrates as compared to DLC films. The adhesion strength of DLC films on polymers was increased by interposing thin TiN layer (200Å) on polymers by in-situ pulsed laser deposition. The DLC films were found to be amorphous with good adhesion to TiN/PMMA substrates.
Diamond-like carbon, pulsed laser deposition, TiN
Cavity Formation and Impurity Gettering in He-Implanted Si
D.M. FOLLSTAEDT, S.M. MYERS, G.A. PETERSEN, and J.W. MEDERNACH
Sandia National Laboratories, Albuquerque, NM 87185-1056.
Cavity microstructures formed in Si after ion implantation of He (30 or 130 keV) and annealing at 700°C or above are examined with cross-section transmission electron microscopy. A threshold concentration of 1.6 at.% He is identified as required to form cavities that survive such anneals. The cavities coarsen with a constant volume corresponding to ~0.75 lattice sites per implanted He atom and have surface areas 3-7 times that of the wafer area for fluences of 1 X 1017 He/cm2. Transition metal atoms (Cu, Ni, Co, Fe, Au) are shown to be strongly trapped (1.5-2.2 eV) on the cavity walls by chemisorption. Whereas Cu, Au, and Ni are bound more strongly to the cavity sites than to their respective precipitated phases, Co and Fe are more strongly bound to their silicides; nonetheless, appreciable trapping of Co and Fe does occur in equilibrium with the silicides. Cavity trapping appears to be an effective gettering mechanism at low impurity levels, as needed to meet future microelectronics device requirements.
Gettering, He-implanted, ion implantation, Si
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