bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory Investigation into the Radiolytic Gas Generation from Rock Salt. A Study Related to the Disposal of High Level Radioactive Waste
Authors: Jockwer Norbert , Monig Jörg
Published: March 2011

Salt samples of two different mineralogical compositions were subjected to 60Co-γ-irradiation under an air-atmosphere. The resulting gaseous products were analysed from the gas phase above the salt. Additionally, the salt was subsequently heated up to 300 °C in order to liberate adsorbed, less volatile, and polar compounds. The gases CO2, CO, N2O, H2S, SO2, and Cl2 were identified whereas H2 was notably absent. The influence of various parameters, i. e. the total absorbed dose, the dose rate, and the temperature, on the radiolytic gas production was studied in some detail, increasing dose leads to increasing yields in CO2 and N2O. Carbon monoxide is radiolytically destroyed. Since CO2 and CO occur naturally in rock salt, they desorb thermally to some extent during the irradiation. The dose rate does not affect the yields, while the temperature during irradiation has a big effect on the radiolytic CO2 yields. At 250 °C and a radiation dose of 1×106 Gy a maximum CO2 yield of 70 mg gas per kg irradiated salt was observed. Upon heating the sample to 300 °C for 30 min. 47 mg per kg salt are additionally released.
The Effect of Ground Water - Rock Interactions on the Migration of Redox Sensitive Radionuclides
Authors: Suksi Seija , Siitari-Kauppi M. , Kämäräinen E-L. , Lindberg A.
Published: March 2011

Interactions of redox sensitive elements with common Finnish rocks were studied in the laboratory under oxic and anoxic conditions. Sorption and diffusion of technetium, uranium, plutonium and neptunium were studied in drill cores of granites and gneiss. Cylindrical drill core cup samples and plane surfaces sawed from drill cores were exposed for periods from six to eighteen months to synthetic ground water to which Tc-99, U-233, Pu-236 or Np-237 had been added. Identification of the sorption and the diffusion pathways were discovered by qualitative autora-diography. The concentrations of elements versus depth in the drill core were measured radiometrically, by quantitative autoradio-graphy or by both methods. The migration of plutonium was slow in all samples. Technetium, uranium and neptunium were transported effectively under both oxic and anoxic conditions. Transported species of these elements were found throughout the rock matrices investigated - in microfissures, along mineral grain boundaries and in the minerals themselves. The ranges of the measured apparent diffusivities for neptunium were (2.7 – 30) × 10−14 m2/s under oxic conditions and (1.4 – 4.3) × 10−14 m2/s under anoxic conditions. For uranium the range of Da-values under oxic conditions was (3.6 – 5.7) × 10−14 m2/s under anoxic conditions it was (1.1 × 4.3) × 10−14 m2/s in granitic ground water and (1.8 – 5.3) × 10−14 m2/s in bentonite water.
Speciation of Transuranic Ions in Groundwater by Laser-Induced Photoacoustic Spectroscopy (LPAS)
Authors: Klenze R. , Kim J. I.
Published: March 2011

The speciation of the Am(III) ion in various chemical states is illustrated using laser-induced photoacoustic spectroscopy (LPAS). Based on these reference LPAS spectra, the actual chemical states of Am(III) in one of Gorleben groundwaters are systematically verified. The a-radiolytic oxidation of Am(III) to Am(V) in the concentrated NaCl solution and their carbonate complexation are also speciated for the purpose of demonstration.
In Situ Parametric Investigation of the Mechanism of Diamond Film Deposition from Low Energy Ion Beams
Authors: Lifshitz Y. , Kasi S. R. , Rabalais J. W.
Published: March 2011

A general scheme for the analysis of deposition from hyperthermal (10–5000 eV) species is presented. Successful deposition involves consideration of species range, maximum local concentration obtainable, trapping efficiency, radiation damage, and sputtering efficiency. Examples of in situ parametric investigations of carbon deposition performed with a controlled mass selected UHV ion beam facility are presented. A subplantation model for diamond film deposition is discussed. XRD evidence for epitaxial growth of diamond(111) on Si(111) is provided.
Effects of Ionized Cluster Beam Bombardment on Epitaxial Metal Film Deposition on Silicon Substrates
Authors: Yamada Isao
Published: March 2011

The effects of ion beam bombardment during ionized cluster beam (ICB) deposition of metal films on Si(111) and Si(100) substrates have been discussed. In the case of Al deposition, films have been epitaxially deposited on Si(lll) and Si(100) substrates at near room temperature. On Si(111) substrates, nearly perfect Al single crystal films could be formed. On Si(100) substrates, Al bicrystals have been grown epitaxially. A remarkable fact concerning these results is that the epitaxial films could be formed at nearly room temperature and on a large lattice mismatch (25%) substrate surface. Atomic resolution TEM analysis suggests that the epitaxy of Al occurs not only on Si surfaces but also at Al/Al grain boundaries. These epitaxial films exhibit extremely high thermal stability and long electromigration life time. To understand the deposition features and film characteristics, the effects of ICB bombardment on the film growth at the initial stage of the deposition and the resultant film structure have been studied. The results show that the role of very low energy ion bombardment is especially important in forming epitaxial metal films. Depositions of Au and Cu on Si substrates have also been made to understand whether ICB deposition may improve the characteristics of other metal films. Preliminary results of these film depositions are also obtained.
A Thermal Spike Analysis of Low Energy Ion Activated Surface Processes
Authors: Gilmore C. M. , Haeri A. , Sprague J. A.
Published: March 2011

A thermal spike analysis was utilized to predict the time evolution of energy propagation through a solid resulting from energetic particle impact. An analytical solution was developed that can predict the number of surface excitations such as desorption, diffusion or chemical reaction activated by an energetic particle. The analytical solution is limited to substrates at zero Kelvin and to materials with constant thermal diffusivities. These limitations were removed by developing a computer numerical integration of the propagation of the thermal spike through the solid and the subsequent activation of surface processes.
A Model of a Combined Film Deposition and Ion Bombardment for Coatings Formation
Authors: Iskanderova Z. A. , Radjabov T. D. , Leiderman R. Yu. , Tukfatullin F. K.
Published: March 2011

The mathematical model of a combined film deposition and and high dose ion implantation for coating formation has been developed. Calculations of concentration profiles of implanted element in the film and substrate depending on different parameters of the model have been carried out.
Silicon Homoepitaxy at Low Temperature Using Microwave Multipolar Plasma for Cleaning and Deposition
Authors: Burke R. , Guillermet M. , Vallier L. , Voisin E.
Published: March 2011

The Microwave Multipolar Plasma (MMP) offers unique features for plasma assisted deposition by combining multipolar magnetic confinement and microwave excitation. Independent control of the plasma-surface interaction parameters (neutral flux, ion flux and ion impact energy) has led to low temperature (400–800°C) silicon epitaxial growth in pure or H2 diluted silane MMPs.

Prior to the epitaxial growth of Si, a plasma cleaning is applied to remove 0 and C atoms contaminant from the substrate surface. Ar and H2 were tested on 2 and 4 inch, (100) oriented, silicon wafers loaded “as received” and heated at the deposition temperature. The cleaning is effective in both cases giving a pure Si Auger spectrum. However, a LEED signature is only observed when operating at very low bias of the sample (low energy ions) and the lower the substrate temperature, the lower the energy allowed to obtain a LEED pattern. The cleaning process is also checked and inspected by post-deposition analyses, including TEM, RBS, SIMS and Secco etch.

Various layer thicknesses were grown according to the characterization method. Specular epitaxial films are obtained for a large range of plasma and substrate parameters. The temperature may be as low as 400°C but the best results are obtained in the 600–700°C range. Interestingly, epitaxy is lost when the ion energy is increased. These results show a compromise between ion energy and substrate temperature. One needs to work at low ion energy to enhance the surface reaction while avoiding surface damage, but the temperature has to be sufficiently high to restructure the surface. Preliminary results on intentional doping reveal further potentialities of this low energy controlled interaction for low temperature plasma processing.
Some Recent Results of Fundamental Studies on Beam-Induced Surface Processes
Authors: Dieleman Jan
Published: March 2011

Recent results of studies on the mechanism of processes induced by the interaction of beams of (reactive) particles with surfaces in UHV, often combined with concurrent bombardment of the surface with low-energy ion or excimer laser beams, are reviewed. Angular-resolved mass spectrometry combined with time-of-flight studies on the desorbing products is used as a key diagnostic. A more complete picture is obtained using several other diagnostic tools to characterize the surface before, during or after the interaction. Interactions at Si and Cu surfaces will be emphasized. The review will deal successively with data for interaction with a single beam of Cl2, low-energy noble gas ions or excimer laser pulses, followed by data on the concurrent interaction of crossed beams of Cl2 and low-energy noble gas ions or excimer laser pulses with these surfaces. Some conclusions will be drawn.
Deuterium Interactions with Ion-Implanted Oxygen in Cu and Au
Authors: Myers S. M. , Swansiger W. A. , Follstaedt D. M.
Published: March 2011

The interactions of deuterium (D) with oxygen in Cu and Au were examined using ion implantation, nuclear-reaction analysis, and transmission electron microscopy. In Cu, the reduction of Cu2O precipitates by D to produce D20 was shown to occur readily down to room temperature, at a rate limited by the transport of D to the oxides. The reverse process of D2O dissociation was characterized for the first time below the temperature range of steam blistering. The evolution of the Cu(D)-Cu2O-D2O system was shown to be predicted by a newly extended transport formalism encompassing phase changes, trapping, diffusion, and surface release. In Au, buried 0 sinks were used to measure the permeability of D at 573 and 373 K, thereby extending the range of measured permeabilities downward by about six orders or magnitude.
Phases and Microstructures of Carbon-Implanted Niobium
Authors: Huang J. S. , Musket R. G. , Wall M. A.
Published: March 2011

Polycrystalline niobium was implanted with 200, 100, and 50 keV carbon ions to create a uniform distribution of carbon over a thickness of about 0.25 μm. Samples implanted with calculated carbon content of 0.6, 1.9, 5.8, and 16 atomic percent were prepared, and the uniformity of the carbon distribution with depth was confirmed by Auger electron spectroscopy analysis. Glancing-angle X-ray diffraction analysis and transmission electron microscopy were used to characterize the phases and microstructures formed. The results indicated that no detectable second phases were present except on the surfaces where an amorphous phase and many particles were formed from contamination. Despite the low equilibrium solubility limit of carbon in Nb, we have created metastable solid solutions of Nb and C with carbon contents as high as 16 at.%.
Structural Modifications Induced by the Electronic Slowing Down of Swift Heavy Ions in Matter
Authors: Jousset J. C. , Balanzat E. , Bouffard S. , Toulemonde M.
Published: March 2011

In the last five years, the use of GeV heavy ions, such as those accelerated at GANIL, has lead to a breakthrough in the knowledge of the effects induced by the huge energy deposition which occurs during the slowing down of a swift heavy ion in matter.
Ion Beam Analysis of O, N, and B Compositions in Materials Using Non-Rutherford Scattering of Protons
Authors: Parikh N. R. , Zhang Z. H. , Swanson M. L. , Yu N. , Chu W. K.
Published: March 2011

Elastic scattering of protons with energies from 1.5 MeV to 2 MeV was used to determine the concentration of oxygen in Y-Ba-Cu-O compound, nitrogen in GaN films, and boron in B-Si glass and other materials. Proton scattering from light elements in this energy range exhibits non-Rutherford scattering cross section, which are enhanced by a factor of 3 to 6 or more relative to the Rutherford scattering cross sections. Thus the sensitivity for the light clement detection is considerably larger than that obtained by He ion scattering.

Quantitative analysis by proton scattering is discussed and compared with other methods.
Effects of Sputtered Particle Energy on the Properties of SiO2 Films
Authors: Taga Yasunori , Ohwaki Takeshi
Published: March 2011

The secondary ion energy distributions (SIED) emitted from Si under various conditions of targets (Si, SiO2) and primary ions (Ar+, O+) were measured and the thin SiO2 films were deposited by magnetron sputtering techniques under the corresponding conditions to the SIED experiments. The most probable energies of silicon oxygen cluster ions of SimOn+ (m, n=l, 2,…) are equal to those of Al+ thermal ions, while those of Siℓ+ (ℓ=l, 2,…) remain unchanged with the introduction of oxygen in chamber during Ar+ ion bombardment. The currentvoltage plots of SiO2 films are also measured and found to be influenced by the deposition conditions.

It is concluded that the differences in current-voltage characteristics of SiO2 films prepared under various sputtering conditions can be reasonably explained in terms of the changes in the most probable energy of the sputtered particles.
Friction Characteristics of B+- and N2+-Implanted Fe-Cr Alloys
Authors: Sasaki Jun , Iwaki Masaya
Published: March 2011

A study has been made on friction and hardness of boron and nitrogen ion implanted Fe-Cr alloys. Ion implantation has been carried out with doses ranging from 5 wt% up to 20 wt% at energies of 50, 100 and 150 keY at room temperature. Reciprocal traces for friction coefficient measurements were performed by using a Bowden-Leben tester at a low speed without lubricant. Hardness was measured by using a micro-Vickers tester at a load of 2gf. Hardness of the specimen increases after the implantation with either of ion species. Friction measurements with reciprocal sliding show that a life-time of decreased friction coefficient depends on implanted ion species, Cr concentrations and acceleration energies. For B+- implantation, the lower the chromium contents are, the longer a decreased friction coefficient lasts. Meanwhile, the friction reduced by nitrogen implantation lasts longer for higher chromium content substrates. Dependence of friction coefficient on an acceleration energy is discussed for B+-implantation.
The Friction and Wear Behavior of Ion Beam Assisted Nitride Coatings
Authors: Tetreault Thomas G. , Hirvonen J. K. , Parker G. , Hirvonen J. P.
Published: March 2011

The method of Ion Beam Enhanced Deposition, (IBED), was used to produce hard films of i-BN, i-SixNy and i-TixNy. The friction, hardness, adhesion, and wear behavior of these nitride coalings were examined using a ball-ondisc Friction/wear tester. The friction and wear results were sensitive to stoichiometry and the presence of impurities (e.g., hydrogen) in the film as well as the choice of ball material (400C stainless steel or silicon nitride).
Surface Mechanical Properties of Ti Alloys Produced by Excimer Laser Mixing of Ti on AISI 304 Stainless Steel
Authors: Jervis T. R. , Hirvonen J-P. , Nastasi M. , Zocco T. G. , Martin J. A. , Pharr G. M. , Oliver W. C.
Published: March 2011

We have investigated the properties of surface alloys of Ti formed by excimer laser melting and mixing of Ti overlayers on AISI 304 stainless steel substrates.The thickness of the initial Ti surface layers and the fluence and number of pulses used to mix the surface were varied to investigate a broad range of processing conditions. Samples were uniformly translated at different speeds under repetitive pulses of homogenized laser radiation at 308 nm to vary the number of pulses incident on the sample. We investigated the surface structure and composition, the wear and friction behavior, and the surface hardness of the resulting alloys.

The extent of mixing is observed by Rutherford backscattering spectroscopy to be proportional to the number of pulses incident on the sample. Amorphous surface layers are formed at some mixing levels with a composition which indicates that Ti substitutes for Fe in the stainless steel on a one to one basis. Incorporation of C from surface and interface contamination is observed but at a level much below that found in comparable ion implanted materials.

Friction coefficient measurements indicate that there exists an optimum level of mixing for each layer thickness. Excessive mixing degrades both the coefficient of friction and the wear performance in dry sliding tests.

As with the tribological measurements, the surface hardness showed a dependence on amount of mixing. The surface hardness of the as deposited samples was higher than that of the laser mixed samples, initially decreased with mixing, and finally increased with further mixing.
Combined Oxygen - Nitrogen Ion Implants Into Ti6A14V
Authors: Greenwald Anton , Daly James , Meroth John , Oliver Richard , Sioshansi Piran , Clayton Clive
Published: March 2011

The alloy preferred for medical protheses, Ti6A14V, was ion implanted with oxygen and nitrogen alone and in combination at varying energies, 25 to 120 keV, and varying dose levels, 1017 to 1018 ions/cm2. Measurements were made of microhardness, corrosion resistance, chemical bonding of implanted species, and (with UHMWpo lyethylene) pin-on-disk wear and friction. The addition of oxygen to nitrogen implants now used in production was found to have little effect on wear or any other parameter.
Metal Silicides Formed by Direct Ion Beam Deposition
Authors: Zuhr R. A. , Pennycook S. J. , Haynes T. E. , Holland O. W.
Published: March 2011

Thin films of transition metal silicides have been produced at low temperatures on Si substrates by direct ion beam deposition (IBD) of the metal ion. Using a mass-analyzed beam of metallic ions rastered over the target at energies on the order of 100 eV and at substrate temperatures near 500°C, stoichiometric silicide films of varying thicknesses up to 300 nm have been formed on both n- and p-type Si. The advantages of this technique over other methods for silicide formation include good control of thickness by current integration, high purity due to the mass analysis, and control of incident ion energy which permits formation of the disilicide phase at low temperatures, thereby minimizing the thermal budget and the associated dopant diffusion in the underlying substrate. Films were characterized by Rutherford backscattering, transmission electron microscopy, and electrical measurements. Co, Fe, Ni, Ti, and W silicides have been formed by this direct deposition process. The effectiveness of the technique has been found to be dependent upon the diffusion characteristics of the particular metal/Si couple involved, with systems in which Si is the dominant diffuser, such as Ti/Si, giving the best results. Stoichiometric TiSi2 films produced at 550°C by this process show low bulk-like resistivity (15 μΩ-cm) without subsequent high-temperature annealing. All of these characteristics make silicide formation by IBD attractive for integrated circuit fabrication and shallow junction technology.
Ion Beam Processing of Optical Materials
Authors: Williams F. L. , Boyer L. L. , Reicher D W. , McNally J. J. , Al-Jumaily G. A. , McNeil J. R.
Published: March 2011

We have deposited thin films of optical materials using ion beam sputtering and ion assisted deposition techniques. It is possible to obtain good quality film material deposited on substrates at temperatures lower than normally required. Ion assisted deposition influences film stoichiometry and packing density, which in turn determine optical and mechanical properties of the film material. We discuss two general indicators which appear helpful in predicting the degree to which these occur.
Thermal Annealing Investigation of the Optical Properties of Si1-xNx Films Fabricated by Ion Beam Assisted Deposition
Authors: Donovan E. P. , Carosella C. A. , Vechten D. Van
Published: March 2011

The annealing behavior of the optical properties of silicon nitride films (Si1-xNx) is described for films fabricated by ion beam assisted deposition. The data are needed for the precise manufacture of optical filters, where the index of refraction must be predicted from deposition parameters and film annealing history.

The reflection of homogeneous, amorphous samples deposited on (100) silicon substrates was measured from 500 to 3120 nm. Fits to the interference spectra were obtained over the range 1000 to 3120 nm to obtain the index of refraction vs wavelength as a function of film nitrogen content. Nitrogen atom fraction was varied from.2 to.58 by variation of the incident relative fluxes of nitrogen ion beam current to evaporant silicon flux. The films were annealed in argon at 450 C, 600 C, 750 C, and 1100 C and the measurements repeated. The systematic shifts in index of refraction with annealing temperature are described.
Microtopography of Ion Beam Etched NiP Films.
Authors: Noguchi Kazuhiko , Ueda Ryuzi , Maeyama Yoshitaka
Published: March 2011

The microtopography of NiP films ( P content, 8.7–12wt.%; thickness, 40–50 μm ) prepared by electroless plating on 18–8 stainless steel plates for molds and etched with a 10 keV Ar+ ion beam was studied both by SEM observations and Talystep surface profile measurements. With films containing less than 9.6wt.%P, which is supposed to have a transient structure between the supersaturated solid solution and the amorphous solid, smooth surfaces were obtained down to a few micrometers of etch depth and after that craters were formed. As for the mechanism of crater formation, it is considered that Ni crystallites locally precipitate by ion bombardment and then are etched selectively. With amorphous films containing 10.6wt.%P, microcavities less than 0.02 μmRmax instead of craters were observed regardless of the etch depth. The ion beam etching of NiP films has been found to be very promising for the preparation of precision molds of various grades, e.g. for plastic lenses used in opto-electronics, by selecting P content according to the desired surface roughness and etch depth of a particular application.
Micro-RBS Analysis of Masklessly Fabricated Structures
Authors: Kinomura A. , Takai M. , Matsuo T. , Satou M. , Kiuchi M. , Fujii K. , Namba S.
Published: March 2011

Rutherford backscattering (RBS) analysis of small-sized structures, fabricated by laser chemical vapor deposition (LCVD) with a focused laser beam and ion implantation with a focused ion beam (FIB), has been performed by a microprobe with focused 1.5 MeV helium ions. Micro-RBS spectra and RBS-mapping images revealed a local distribution of masklessly deposited Mo layers on GaAs and local doses of masklessly implanted Au atoms in Si.
Modelling of Pyrolytic Laser Direct-Writing from Thin Metalorganic Films
Authors: Price Peter E. , Jensen Klavs F.
Published: March 2011

A one-dimensional model for pyrolytic laser direct-writing of metal features from thin metalorganic films is presented. The model extends previous results for scanning laser crystallization by including separate but coupled mass and energy balances and allowing for variations in the optical properties and thermal conductivity in the film as it decomposes. A finite element approach is used to obtain solutions to the steady state and transient model forms. The model predicts the existence of multiple steady states for a range of laser powers when the optical absorbance is a nonlinear function of the fractional conversion in the film. These predictions agree qualitatively with multiple steady states that have been observed in direct-writing of palladium features from palladium acetate films. Experimental results that demonstrate multiplicity in the palladium acetate system are presented. The model also predicts the existence of periodic solutions that correspond to the periodic features that have been reported for direct-writing of gold features from organogold films.
Laser-Induced Chemical Vapor Deposition of High Purity Aluminum
Authors: Baum Thomas H. , Larson Carl E. , Jackson Robert L.
Published: March 2011

The laser-induced chemical vapor deposition (LCVD) of aluminum metal has been achieved via the pyrolytic decomposition of trimethylamine aluminum hydride (TMAAH). This material is a volatile, crystalline solid which is non-pyrophoric, in contrast to many other aluminum precursors. Laser-driven pyrolysis of TMAAH enables the selective deposition of high purity, highly conducting aluminum deposits. The volatility of the TMAAH precursor is directly responsible for the rapid rates of aluminum deposition and permits rapid scan velocities to be utilized. The relationship between the chemical structure of TMAAH and the high purity of the aluminum deposits is described.
Ion Beam Processing of Optical Materials
Authors: Williams F. L. , Boyer L. L. , Reicher W. , McNally J. J. , Al-Jumaily G. A. , McNeil J. R.
Published: March 2011

We have deposited thin films of optical materials using ion beam sputtering and ion assisted deposition techniques. It is possible to obtain good quality film material deposited on substrates at temperatures lower than normally required. Ion assisted deposition influences film stoichiometry and packing density, which in turn determine optical and mechanical properties of the film material. We discuss two general indicators which appear helpful in predicting the degree to which these occur.
Patterned Crystal Growth of GaAs by Laser Assisted Atomic Layer Epitaxy
Authors: Iwai Sohachi , Meguro Takashi , Aoyagi Yoshinobu , Namba Susumu
Published: March 2011

Atomic layer epitaxy (ALE) of GaAs is achieved by metalorganic vapor phase epitaxy (MOVPE) under irradiation by Ar ion laser. The self-limiting mechanism for gallium deposition at one atomic layer on an arsenic atomic surface is realized by the site-selective decomposition of triethylgallium on the arsenic surface. A patterned growth of ALE is obtained by scanning a laser beam on a substrate.
Laser Patterning of II-VI Epitaxial Thin Films
Authors: Irvine S.J.C. , Hill H. , Hails J.E. , Blackmore G.W. , Mullin J.B.
Published: March 2011

The laser induced photo-MOVPE (photolytic-metal organic vapour phase epitaxy) technique has been used to grow epitaxial films onto CdTe or GaAs substrates (with a 257nm frequency doubled Argon ion laser). The growth temperature was chosen to be below the normal pyrolysis temperature so that decomposition of the metal-organics will only occur within the illuminated parts of the substrate. A measure of enhancement of growth rate by UV illumination is the photo-enhancement factor which has been determined for CdTe deposits onto Si(100) substrates using the precursors dimethyl cadmium (Me2Te) together with either diethyl telluride (Et2Te) or dimethyl ditelluride (Me2Te2). For patterned epitaxial layers at 300°C, Et2Te was preferable to Me2Te2 because Et2Te was more stable, yielding a higher photo-enhancement factor. A 2-D array of CdTe mesas (60 × 60μm) has been deposited onto a GaAs (100) substrate. Using imaging SIMS (secondary ion mass spectrometry) the distribution of major elements and impurities have been studied.
A Comparison of the Gas Phase Processes Resulting from SiH4 and Si2H6 Photodissociation with a Pulsed ArF Excimer Laser
Authors: Boch E. , Fuchs C. , Fogarassy E. , Siffert P.
Published: March 2011

We present in this paper a comparison of the photodissociation processes of SiH4 and Si2H6 under pulsed excimer laser at 193 nm. The experimental curves of the gas composition as a function of laser energy density show that the dissociation of Si2H6 results from both one and two-photon absorption whereas SiH4 only absorbs two photons. The deposition yield of Si2H6 has also been determined as a function of the number of laser pulses or initial pressure. These experimental results show the establishment of a stationary state in the gas phase and prove the existence of reverse reactions in the disilane kinetic model. The photodissociation of Si2H6 under UV laser excitation (193 nm) presents, therefore, similar properties to those of SiH4.
Selective Photochemical Dry Etching of Compound Semiconductors: Enhanced Control Through Secondary Electronic Properties
Authors: Ashby Carol I. H.
Published: March 2011

When laser-driven etching of a semiconductor requires direct participation of photogenerated carriers, the etching quantum yield will be sensitive to the electronic properties of a specific semiconductor material. The band-gap energy of the semiconductor determines the minimum photon energy needed for carrier-driven etching since sub-gap photons do not generate free carriers. However, only those free carriers that reach the reacting surface contribute to etching and the ultimate carrier flux to the surface is controlled by more subtle electronic properties than the lowestenergy band gap. For example, the initial depth of carrier generation and the probability of carrier recombination between the point of generation and the surface profoundly influence the etching quantum yield. Appropriate manipulation of process parameters can provide additional reaction control based on such secondary electronic properties. Applications to selective dry etching of GaAs and related materials are discussed here.
Mass Spectrometric Probing of Laser-Induced Materials Vapor Transport: Graphite and Superconducting YBa2Cu3Ox
Authors: Bonnell David. W. , Schenck P. K. , Hastie J. W.
Published: March 2011

A very high pressure-sampling mass spectrometer has been used to identify the vapor transport species and determine the thermochemistry and kinetics of laser-induced plumes produced from graphite and superconducting composition YBa2Cu3Ox targets (x = 6.5 to 7). An electron impact ion source was used for the ionization and detection of neutral plume species. The plumes initially contain -1 atm (1 atm = 101.325 kPa) of neutral and charged atomic and molecular species in a vacuum of <10−7 atm. Time resolved mass spectra were obtained with graphite targets for the neutral plume species Cn (n = 1-9) for varying laser fluence, laser-surface interaction geometry, vapor plume-sampling geometry, and target surface morphology. Relatively low abundance charged species C1+, C2+, C3+, and impurities Na+ and K+ were also observed in the laser-induced plume.

Mass spectra obtained with superconducting YBa2Cu3Ox targets showed a variety of species in the laser-induced plumes including both neutral and ionic Y, Ba, and Cu. In addition, molecular species such as O2, BaO, CuO+, YO and bimetallics (BaCu, YCu) were observed.
Ejected Product Energy Distributions from Laser Ablated Solids
Authors: Helvajian H. , Welle R. P.
Published: March 2011

At laser threshold fluences near ion product formation, we have measured the ejected ion kinetic-energy distributions from the UV laser ablation of crystalline aluminum and silver targets. The mean kinetic energy is found to be hyperthermal.
Laser-Induced Reactive Evaporation and Condensation
Authors: Chow Gan-Moog , Struti Peter R.
Published: March 2011

A study of laser-induced reactive evaporation-condensation is presented. This considers coevaporation of metallic, and non-metallic species, by a cw carbon dioxide laser beam, within a reducing environment (98.5% hydrogen, 1.5% methane). A heated W filament placed in proximity of the laser beam-substrate interaction zone produces W for deposition via chemical vapor transport reactions. Composite thin films of a W matrix containing amorphous silica fibers have been deposited on nickel alloy substrates. These films form at rates of about 1 micron/sec, and are found to be adherent to the substrates. The diameter of the fibers is between 25 nm and 120 nm, depending on the interaction time. Various analytical techniques have been employed to characterize as-synthesized layers. Mechanisms of this process are discussed.
Ablation of Polymers with Pairs of Ultraviolet Laser Pulses with Controlled Temporal Separation
Authors: Braren Bodil , Srinivasan R.
Published: March 2011

The dependance on the pulse width of the ultraviolet laser ablation and etching of poly(methyl methacrylate) was examined using 40-100 ns pulses. These pulses were created by stitching together two identical pulses, each of 40 ns half-width, which were separated by a set time interval from 0 to 380 ns. The etch depth/pulse is sensitive to the pulse width and, therefore, the power density in this polymer.

The response of PMMA to etching by pairs of pulses suggests that short-lived species which may be electronic states (e.g., triplets) and/or radicals play an important role in the ablation. The shape of the pulse was also found to influence the etch depth/pulse.

The etching of polyimide by these extended pulses shows trends that are opposite to those observed in poly(methyl methacrylate). In this instance the shielding of the latter portion of the incoming pulse by the products that are ablated by the front portion is probably a serious effect.
Ultrathin Silicon Dioxide Films: Photo-Induced Growth
Authors: Boyd Ian W.
Published: March 2011

The reaction of oxygen with silicon induced by intense photon beams at different wavelengths is described. We find different enhancement rates applying to UV and visible radiation, which can be as high as 400% for thin film growth at low temperatures. Often, however, they can be so small that they may be completely overshadowed at high temperatures by the rapid oxidation rates arising from thermal contributions. By using UV radiation projected through a mask to induce low temperature photonic oxidation of silicon, we have grown directly patterned oxide structures dispensing with the need for conventional photolithographic etching.
Reversible Laser Modification of High Temperature Superconducting Y-Ba-Cu-O Films
Authors: Krchnavek Robert R. , Chan Siu-Wai , Rogers C.T. , Rosa F. De , Miceli P.F. , Allen S.J.
Published: March 2011

We describe a reversible technique for locally modifying the oxygen stoichiometry and electrical transport properties of superconducting thin films. A focused argon ion laser beam is scanned across the surface of a YBa2Cu3O7-x thinfilm, contained in a vacuum, at incident power levels well below those necessary for ablation. The change in oxygen stoichiometry is monitored in-situ by the room temperature electrical resistance. We have measured the superconducting properties of these locally modified films. The resulting R vs T curve for the composite structure (film/laserstripe/film) shows the expected double transition. The first transition, corresponding to the unmodified film, occurs at 87 K while the second transition, corresponding to the modified stripe, occurs at a lower temperature and is a function of the laser induced change in the room temperature electrical resistance. The critical current for the composite structure is depressed from the original film. The laser writing can be erasedor bleached out by room temperature exposure to an oxygen plasma.
The Spectroscopy and Surface Chemistry of Metal-Alkyl Molecules
Authors: Shaw P. , O'Neill J. , Sanchez E. , Wu Z. , Osgood R.W.
Published: March 2011

metal-alkyl molecules provied an early source molecule for photodeposition of metal. They continue to be of interest for patterned and unpatterned laser deposition and for conctact formation on compound semiconductors. This article provides a brief review of what has been learned about the surface photo-physic of this class of molecules based on several years of study with uV and iR absorption spectroscopy, UHV surface analysis, and thermal and photodesorption amass spectroscopy.
Pulsed Laser Processing of Targets Immersed in Liquid Media
Authors: Partridge Julian P. , Strutt Peter R. , Klemens Paul G.
Published: March 2011

This report describes a study of the formation of TiN thin films produced by laser irradiation of titanium targets immersed in liquid nitrogen. Three fluence thresholds have been determined, corresponding to: (i) surface melting in gaseous nitrogen (0.7 J/cm2) (ii) surface melting under liquid nitrogen with TiN formation (1.2 J/cm2) and (iii) gross melting accompanied by the generation of periodic surface structures ( >2.0 J/cm2). Data obtained from transmission electron microscopy, Auger spectroscopy, and XPS studies show that the rapid solid-statecooling rates ( l010deg/sec ) result in a supersaturated, twinned hcp structure with solute contents up to 40 at% nitrogen.

Theoretical estimates suggest that the majority of the incident excimer laser radiation is absorbed by the target with subsequent thermal transfer to the liquid producing a highpressure shock wave originating at the liquid-solid interface. Pressures up to 4.3 GPa are predicted with the expanding vapor layer reaching a terminal velocity after 5 μs and a total lifetime of 28 μs. Such a lifetime is considerably longer than the thermal pulse in the substrate (from a I-dimensional heat flow analysis). The results are discussed with reference to such estimates. Because the thermal diffusivity far exceeds that of the solute, the extent of nitridation is determined predominantly by the first 200 ns of the thermal pulse experienced by the target.
Physical and Chemical Sputtering at Very Low Ion Energy: the Importance of the Sputtering Threshold
Authors: Steinbruchel Christoph
Published: March 2011

A variety of data for physical etching (i.e. sputtering) and for ion-enhanced chemical etching of Si and SiO2 is analyzed in the very-low-ion-energy regime. Bombardment by inert ions alone, by reactive ions, and by inert ions in the presence of reactiveneutrals is considered. In all cases the etch yield follows a square root dependence on the ion energy all the way down to the threshold energy for etching. At the same time, the threshold energy has a non-negligible effect on the etch yield even at intermediate ion energies. The difference between physical and ion-enhanced chemical etch yields can be accounted for by a reduction in the average surface binding energy of the etch products and a corresponding reduction in the threshold energy for etching. These results suggest that, in general, the selectivity for ion-enhanced etch processes relative to physical sputtering can be increased significantly at low ion energy.
On the Use of MÖssbauer Nuclei as Probes of Radiation Induced Effects at Interfaces
Authors: Ingemarsson P. A. , Ericsson T. , Possnert G. , Wappling R.
Published: March 2011

Conversion electron M6ssbauer spectroscopy was used as a means of investigating radiation induced changes at thin film interfaces. 25 Å thick layers of 57Fe were evaporated onto substrates of Si,SiO2 and A12O3 andcovered with 150 Å 56Fe. Samples were then subjected to ion irradiation with 20 MeV C14+ to doses ranging from 1012 to 2x 1014 ions/cm2 and subsequently annealed in vacuum at 450 ºC. Mössbauer spectra were recorded before and after each step. The analysis revealed chemical alterations, induced by the ion bombardment, indicative of film-substrate bond formation and reconstruction of residual surface hydrocarbons. The results are interpreted in view of accompanying enhancements in thin film adhesion.
Heavily Doped Ultra-Shallow Junctions Formed by an ArF Excimer Laser
Authors: Yoshioka S. , Wada J. , Saeki H. , Matsumoto S.
Published: March 2011

Boron doping of single crystal silicon using an argon fluoride excimer laser with diborane gas has been performed. Diborane gas has an absorption at 193nm, which leads to gas phase photodecomposition of the diborane. Utilizing the photolyic effect, we obtained high surface concentration and ultrashallow junctions of 5×1020 cm−3 and 0.1 µm, respectively. The photolytic effect enhances the incorporation of the dopant species.
Laser Patterning of High Temperature Superconducting Oxide Films
Authors: Gupta A. , Hussey B. W. , Jagannathan R. , Cooper E. I. , Giess E. A.
Published: March 2011

A focused argon ion laser (514 nm) beam has been used for patterning superconducting lines of YBa2Cu3O7–δ using films prepared from metal trifluoroacetate solution precursors. A stoichiometric mixture of the precursors is dissolved in methanol, and the solution is spun on yttria-stabilized zirconia substrate to form a film. The film is patterned by irradiating in selected areas by direct laser writing to convert the irradiated layers to an intermediate fluoride state, the nonirradiated areas being unchanged. The nonirradiated areas are then dissolved away, leaving a pattern of the fluoride material. This patterned layer is converted to the superconducting oxide in a subsequent high temperature step involving reaction with water vapor.
Photochemical Vapor Deposition of Aluminum Thin Films
Authors: Hanabusa Mitsugu , Oikawa Akira , Cai Peng Ying , Furuno Shigeo , Iguchi Satoshi
Published: March 2011

Using dimethylaluminum hydride as the source gas and an ArF laser as the light source, aluminum thin films with low electrical conductivity were deposited via photochemical reactions. To emphasize surface reactions, vapor pressure was kept low with a t pical value of 6.7×10−3 Pa. The laser energy density was typically 23 mJ/cm2 per pulse. The deposition rate of aluminum films became reasonably high above a substrate temperature of 90 °C and increased thereafter with substrate temperature. The electrical resistivity was about four times greater than the bulk aluminum value. A strongly nonlinear dependence of the deposition rates on laser energy density was observed. The incremental change in thickness per pulse increased with the inverse of the pulse repetition rate, which indicated, together with area selectivity, the importance of surface photolysis of absorbed molecules.
Licvd of Cr(C,O) Films from Cr(CO)6 at 248 NM: Gas-Phase and Surface Processes
Authors: Nowak R. , Konstantinov L. , Hess P.
Published: March 2011

The influence of laser fluence and carbon monoxide partial pressure on the deposition rate of thin Cr(C,O) films was investigated. The films were deposited from Cr(CO)6 mixtures with CO and Ar using a KrF excimer laser. The observed results are discussed with respect to the relative importance of gasphase and surface processes. The results reveal that under the present experimental conditions chromium atoms produced in the gas phase play only a minor role as direct film precursors in KrF laser-induced film deposition.
Laser Induced Temperature Rise In Semiconductors : Analytical Solutions, Application to the Transient
Authors: Maruani Alain , Nissim Y.I. , Bonnouvrier F. , Paquet D.
Published: March 2011

It is shown how the systematic use of the method of integral transforms greatly simplifies the calculation of the temperature rises in laser irradiated media. In general, this method leads ultimately either to analytical results or to very simple numerical integrals (e.g. no poles, exponential kernels). We focus here on the analytical results, and discuss some aspects of CW laser heating, for large surface absorption, including radial dependance, depth dependance and transient nonlinearities. The new results derived in this treatment are in good agreement with experimental data from other studies.
Survey of the Thermodynamics and Kinetics of Crystallization of Si and Ge
Authors: Turnbull D.
Published: March 2011

The thermodynamic interrelations of the crystalline (c-sc), amorphous semiconducting (a-sc) and liquid metal (lm) states of Si and Ge, based on the existing thermal data, are reviewed. Then the kinetics of the interfacial processes in the growth of c-sc and a-sc into undercooled lm and the conditions for transition from c-sc to a-sc growth are discussed.
Laser-Induced Surface Defects
Authors: Moison Jean-Marie , Bensoussan Marcel
Published: March 2011

The influence of pulsed laser processing (PLP) on the structure and composition of Si, GaAs, Inp and au surfaces has been investigated as a function of the laser fluence. Above a threshold fluence, all initial structures turn into a (1×1) structure and the V-element content of the compound surfaces is decreased. The structure change is shown to be related to the existence of a number of atomic steps on the Plp surface (up to 10114 /cm2 equivalent broken bonds). These defects can be eliminated by further annealings. On the other hand, the stoechiometry defects, which are less numerous (1012−1013/cm2) cannot be eliminated. A model for the mechanisms of defect creation and annihilation during PLP is outlined. The incidence of PLP-induced defects on device technology is evaluated.
Applications of a Continuous Wave Incoherent Light Source (Cwils) to Semiconductor Processing
Authors: Harrison H.B. , Johnson S.T. , Cornish B. , Adams F.M. , Short K.T. , Williams J.S.
Published: March 2011

We present results which highlight applications of a continuous wave incoherent light source in the processing of semiconductor devices. In particular, damage removal and activation of ion implanted gallium arsenide is demonstrated for both capless and capped annealing of low dose implants at temperatures of > 800°C for times < 10 s. For gallium arsenide FET applications, we demonstrate that it is possible to simultaneously carry out activation, contacting and interconnection steps by utilizing thermomigration processes which are not available with conventional furnace processing. In silicon we demonstrate that shallow multi layer bipolar structures can be successfully fabricated with anneal cycles that lead to supersaturation effects and negligible diffusion.
Beam Processing of Silicon With a Scanning CW Hg Lamp
Authors: Stultz Tim , Sturm Jim , Gibbons James
Published: March 2011

A scanning arc lamp annealing system has been built using a 3” long mercury arc lamp with an elliptical reflector. The reflector focuses the light into a high intensity narrow line source. Silicon wafers implanted with 100 Kev 75As+ to 1×l015 cm−2 have been uniformly annealed with a single scan, resulting in complete activation and negligible redistribution of the implanted species. Using a scan rate of 1cm/s, entire 3” wafers have been annealed in less than 10 seconds with this system. The system has also been used to recrystallize thin films of polysilicon deposited on thermally grown silicon dioxide. The recrystallized films contain grains that are typically 0.5–1 mm in width and several centimeters long. Surface texture measurements show the crystallites to be almost entirely (100) in the plane of the film with the orthogonal <100>direction closely paralleling the scan direction. Mosfets were fabricated in these films with surface mobilities 66% of ones fabricated in single crystal silicon. An epitaxial layer with the same crystallographic features as the recrystallized film was grown on the film itself.
Oxygen and Nitrogen Incorporation During Cw Laser Recrystallization of Polysilicon
Authors: Drowley C.I. , Kamins T.I.
Published: March 2011

The incorporation of nitrogen and oxygen in polysilicon has been examined by SIMS. The analysis, combined with C-V measurements and ion implantation, has been used to correlate the incorporation of the two species with the fixedcharge density at the back polysilicon/Si02 interface. Laser recrystallization with a silicon-nitride encapsulation layer results in the inclusion of 2–4 × 1017 cm−3 nitrogen atoms in the polysilicon; if an oxide capping layer is used, the nitrogen level observed is at the background of the SIMS system (~1015cm−3). Either type of capping layer results in 3−4×1018cm−3 oxygen atoms being incorporated into the polysilicon. Implantation of nitrogen into the polysilicon before recrystallization increases the fixed-charge density Nf,b) at the back interface, while implanted oxygen decreases Nf, b. The high Nf, b found with a nitride capping layer is attributed to deposition of nitrogen or SiNx at the back interface.