bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Laser-Induced Surface Reactions by Surface Temperature Modulation Techniques
Authors: Comita Paul B. , Strongin Daniel R. , Kodas Toivo T. 
Published: March 2011

ABSTRACTTwo relaxation techniques are described, both of which use surface temperature modulation as their basis. In these techniques, modulation of laser light intensity results in a modulation of surface reaction rates. The first technique, a diffusive transport relaxation technique, has been developed to study the chemical reactions occurring under the high pressure conditions used in laser-induced chemical vapor deposition. Perturbation of the reaction rate in a high pressure reactor produces transients in the gas phase reactant and product concentrations for the case of gas phase transport-limited deposition. The product species are differentiated from species formed from the reactant during ionization and fragmentation due to the phase-sensitive nature of the detection scheme. The system response is examined theoretically by examining the response of the gas phase reactant and product concentrations to the modulated surface reaction. The second technique is a new technique which has been developed for obtaining detailed information concerning reaction energetics and pathways of elementary surface reactions. This technique also employs a laser to generate a surface temperature modulation. The laser light is incident on a pure metal film which is mounted within an ultra high vacuum chamber. By modulating the laser intensity, the surface chemical reaction rates are modulated. The combined use of surface temperature modulation and appropriate linearization methods allows a quantitative analysis of the overall reaction energetics to be made. and is used here to investigate the surface processes in a thermal laser-induced reaction.
Laser Deposition of Gold
Authors: Sell Jeffrey A. , Meyer Martin S. , Meisner Gregory P. 
Published: March 2011

ABSTRACTMetallic gold was deposited on several different substrates by laser pyrolysis of a goldcontaining ink. The gold was deposited in the form of lines by translating the substrate during laser pyrolysis; linewidths ranged from 10 Am to 1.5 mm. This process was performed in open air. Prior to annealing, the films contain 40 to 50 % carbon impurity and the resistivity is extremely high. After a 1 hour anneal in air, the carbon content is reduced to < 5 %, and the resistivity is reduced to roughly 13 times bulk gold. Further improvement may be possible with a different annealing schedule.
Laser Induced Decomposition of Triethylgallium and Trimethylgallium Adsorbed on GaAs(100)
Authors: Mccaulley J. A. , Mccrary V. R. , Donnelly V. M. 
Published: March 2011

ABSTRACTWe report X-ray photoelectron spectroscopy (XPS) studies of excimer laser stimulated decomposition of triethylgallium (TEGa) and trimethylgallium (TMGa) adsorbed on Gastabilized GaAs(100) surfaces in ultrahigh vacuum. TEGa and TMGa dissociatively chemisorb on GaAs at room temperature, whereupon irradiation by an excimer laser (at 193 or 351 nm) leads to further dissociation and desorption of carbon-containing species. The carbon removal rate (per laser pulse) decreases as carbon is removed suggesting multiple reaction sites, coverage dependent Arrhenius parameters, or second-order reactions. Based on the dependence of the rate on laser wavelength and fluence, we conclude that at low fluence, a two-photon electronic excitation of the adsorbate occurs, while at high fluence, laser induced pyrolysis dominates.
Low Temperature Epitaxy of Hg1−xCdxTe
Authors: Cody N. W. , Sudarsan U. , Solanki R. 
Published: March 2011

ABSTRACTMercury cadmium telluride epitaxial layers have been grown using methylallyltelluride (MATe), dimethylcadmium (DMCd), and elemental Hg. Using these precursors high quality films have been achieved over the temperature range of 200-300°C. Comparisons are made between UV photon-assisted and thermally deposited films. Composition, growth rate, and electrical properties are compared for the two processes under various parameter conditions. Properties of films deposited on various substrates including CdTe, GaAs, and GaAs/Si are also described.
Low Temperature OMVPE of ZnSe from Alkyl Sources Using a Plasma Disk Lamp
Authors: Tokuda K. L. , Pihlstrom B. , Kisker D. W. , Schnoes M. Lamont , Collins G. J. 
Published: March 2011

ABSTRACTThe growth of high quality ZnSe by organometallic vapor phase epitaxy (OMVPE) has generally been hindered because of parasitic source pre-reactions or relatively high source decomposition temperatures. In this work, we have used vacuum ultraviolet photons generated by a disk-plasma lamp to assist the ZnSe growth process using diethylselenium and diethylzinc as source materials. This approach has resulted in satisfactory growth rates and high material quality at temperatures as low as 250°C, without the limitations of prereaction typically observed when H2Se is used for the selenium source material. In addition, the alkyl selenium compound offers advantages due to reduced toxicity compared to H2Se. This new, low-growth-temperature process thus offers the possibility of improved stoichiometry and impurity incorporation control as well as a reduced thermal effect on the underlying substrate during growth. At the same time, the advantages of excellent morphology and uniformity typically exhibited by the alkylbased growth processes are retained.
Photoreactions of Mo(CO)6 on Potassium Precovered Silicon Surface with UV to IR Radiation
Authors: Ying Z. C. , Ho W. 
Published: March 2011

ABSTRACTThe adsorption and photoreactions of Mo(CO)6 coadsorbed with K on Si(111)7×7 at 90 K have been studied under ultra-high vacuum conditions. It is found that dissociative adsorption of Mo(CO)6 on the K preadsorbed surface occurs for coverages below a monolayer. A multilayer of physisorbed Mo(CO)6 molecules is formed on top of the monolayer. Under photon irradiation physisorbed Mo(CO)6 molecules are dissociated and CO desorption is observed. The photoreactions of Mo(CO)6 occur over a wide wavelength range from the UV to IR. In contrast, only UV radiation induces photoreactions of Mo(CO)6 on the K-free Si(111)7×7 surface. Evidently K opens a new channel for the photoreactions of Mo(CO)6 on the surface. A mechanism involving interactions between photogenerated charge carriers and the substrate-adsorbate complex is proposed.
Al Photodeposition and Light-Induced Nucleation on p-Type Si from TMA
Authors: Bouree J.E. , Flicstein J. , Bresse J.F. , Rokmeluere J.F. , Pougnet A.M. 
Published: March 2011

ABSTRACTPhotodecomposition of trimethylaluminum (TMA) flowing with H2 on p-type Si under UV irradiation is shown to be exclusively a reaction confined to surface species. Thus photonucleation and photodeposition of Al on Si is controlled either by Si-H or Si-O and Si-OH bonds. In the regions where Si-O and Si-OH are present, Al-O forms, which inhibits Al deposition either directly or via the adsorption of C containing photoproducts. In the other regions where Si is H terminated, it is assumed that H2 adsorbs dissociatively on Al clusters, thus leading to the formation followed by the desorption of methane from the adsorbed phase. For this reason, Al thin films are C contamination free.
High Resolution Direct - Write Photochemical Etching of InP Using Methyl Iodide
Authors: Durose K. , Summersgill J.P.L. , Aylett M.R. , Haigh J. 
Published: March 2011

ABSTRACTPhotochemical etching of InP using a cw frequency doubled Ar+ laser is evaluated with a view to the production of optoelectronic device features. The diffusion-limited resolution of the unmodified etching process is discussed and a new method of etching high resolution grooves which utilises a native oxide coating is described. Grooves produced in this way have widths comparable to that of the laser beam.
Excimer Laser Induced Etching of Silicon-Carbide
Authors: Murahara M. , Arai H. , Matsumura T. 
Published: March 2011

ABSTRACTResistless photoetching of SiC was performed by using XeF and KrF excimer laser beams. In this method, ClF3 gas was used for etchant. C1F3 gas has a unique absorption band in the range of 300- 430 nm. The strongest absorption band corresponds to the wavelength of the XeF laser (350 nm). So C1F3 gas is decomposed effectively. On the other hand, the absorption factor of SiC is about 30% in the range of 200-400 nm, and the bonding energy of SiC is lower than the photon energy of the KrF laser beam. For these reasons, it is possible to cut the bond of SiC directly. Thus, two laser beams were used. Fluence of the KrF laser beam was 200 mJ/cm2, of the XeF, 50 mJ/cm2. Total flow rates through the cell were 0.05 1/min. We can fabricated the etched feature of reticle pattern by reductive projection. Line and space was 10 μm and etching rate was 50Å/pulse.
Laser Induced Chemical Etching of Composite Structure of Ferrite and Sendust
Authors: Nagatomo S. , Takai M. , Lu Y. F. , Namba S. 
Published: March 2011

ABSTRACTMaskless etching of the composite structure of Mn-Zn ferrite and sendust (Fe-Si-Al alloy) was performed by focused argon-ion-laser irradiation in a CCl4 atmosphere and aqueous solutions. Only a mixture of KOH and NaOH aqueous solutions was found to smoothly etch the composite structure by thermochemical reaction using laser irradiation. A maximum etching rate of 14 μm/sec was obtained for sendust-on-ferrite substrates.
Patterning of High Tc Superconductor Films with a Focussed Excimer Laser
Authors: Hagerhorst J.M. , Mannhart J.D. , Oprysko M.M. , Scheuermann M.R. , Tsuei C.C. 
Published: March 2011

ABSTRACTLaser ablation using focussed excimner light has been found to be an effective technique for the direct, maskless patterning of High Tc superconductor films. The apparatus used in the work consists of an adjustable aperture which is illuminated by a 193 nm excimer laser beam. The aperture is imaged by a microscope onto the substrate into an area as large as 200 × 200 to an area as small as 2 × 2 square microns. The superconductor films are placed on a 0.5 micron resolution, computer controlled x-y stage. Laser fluences up to 5 J/cm2 and repetition rates of 10 Hz were found to be sufficient to ablate (pattern) the High Tc films with no apparent effect on their superconducting properties as evidenced by the films′ resistance as a function of temperature (R vs T) before and after patterning.The technique and apparatus are flexible enough to allow patterning across entire substrates and/or the definition of isolated features as small as one micron. To date, the technique has been successfully used to pattern a wide variety of films (based on material and thickness), to fabricate transmission lines several millimeters long, to pattern superconducting quantum interference devices (SQUIDs) which operate at liquid nitrogen temperatures, and to study the behavior of individual grain boundaries within films.
Epitaxial Relationships in Esd Processes on Oxide Surfaces
Authors: Mccartney M.R. , Smith David J. 
Published: March 2011

ABSTRACTDuring intense electron irradiation inside the electron microscope, the electron—stimulated desorption of oxygen from the surfaces of several maximally—valent transition—metal oxides (TiO2, V2O5, Nb2 O5 and WO3) has been observed [1]. The irradiatedsurfaces become covered with a crystalline layer of the corresponding monoxide phase. These reduced phases, which are all based on cubic structures and have metallic conductivity, grow with a well— defined epitaxial relationship with the bulk oxide. Computer—drawn models of the crystal structures have been used to study the atomic arrangements implied by the epitaxial relationship, and certain structural features were found to be common to the oxides studied.
Process Margins for Laser Planarization of 1 to 5 µm Gold Films
Authors: Bernhardt A. F. , Contolini R. J. , Tuckerman D. B. , Weisberg A. H. 
Published: March 2011

ABSTRACTA pulsed excimer laser or flashlamp-pumped dye laser is used to melt 1 to 5 µm Au layers. The size of feature which can be filled by laser planarization is limited because of the finite melt duration, but the basic goal of levelling local surface topography is accomplished.Laser reflow of thicker films reveals fundamental differences between the excimer laser and the flashlamp-pumped dye laser, resulting from the order-of-magnitude difference in pulse duration. The excimer pulse is short compared to the thermal diffusion time of the metal layer and this can create voids and craters in the metal above discontinuities in the underlying structure. For Au thicknesses greater than about 3 µm, void formation occurs at fluences at or below that necessary to planarize the film. The dye laser has a planarization threshold similar to that of the excimer but it takes over 60% greater energy to create voids than to planarize a 5 µm film.A second damage mode, common to both laser sources, occurs where adjacent planarization zones overlap in a patterned area: thin spots can be created by the first planarization pulse which are vaporized by the second pulse.
Laser Surface Modification for Copper Deposition on Polyimide
Authors: Liu Y.S. , Cole H.S. 
Published: March 2011

ABSTRACTSelective modification of surface reactivities with lasers, using either direct writing or projection method, is intrinsically a sensitive method to prepare a surface for highresolution and high-speed area selective thin film deposition. In this paper, we demonstrated the use of laser direct-writing and projection patterning techniques for selective modification of the electrochemical property of a polyimide surface. High quality and highresolution copper patterns on polyimide surfaces are produced when the surface-modified sample is subsequently placed in an electroless plating solution. These results demonstrated that the use of laser-selective-modification of surface properties in conjunction with other batch thin film deposition processes provides an attractive approach for area-selective metallization for a variety of applications in which high writing speed and high sensitivity are required.
Patterned Excimer Laser Etching of GaAs Within a Molecular Beam Epitaxy System
Authors: Maki P. A. , Ehrlich D. J. 
Published: March 2011

ABSTRACTWe have utilized an ArF excimer laser in a projection imaging geometry to etch GaAs layers grown in situ within a molecular beam epitaxy (MBE) system. Clean epitaxial surfaces were prepared using standard MBE growth procedures, then etched in a second chamber isolated by a gate valve. We report studies of the etching dependence on pulse rate (0.2 Hz to 150 Hz) and chlorine pressure (10−6, 10−4, and 5×10−3 Torr). We discuss the etching mechanism in terms of previous studies of the reaction between GaAs surfaces and molecular chlorine under high vacuum conditions. We show that the pulse rate and Cl2 pressure dependencies of the etching can be explained by the progress of the reaction at the instant of pulse exposure. Etch morphology is found to vary with the repetition rate, with the smoothest surfaces obtained at low repetition rates. We discuss the implications of the results in the context of in situ thin layer processing and epitaxial overgrowth.
Tunable Uv Laser Photolysis of Organometallic Compounds with Product Detection by Laser Mass Spectroscopy
Authors: Beuermann Th. , Stuke M. 
Published: March 2011

ABSTRACTWe use tunable UV laser light in the region 200-320 nm, produced by frequency doubling the output of a dye laser for the decomposition of organometallic compounds. This method has been applied to TMA, trimethylaluminum AI(CH3)3. Only theTMA monomer absorbs UV light for λ>220nm. TMA decomposes by one-photon absorption mainly into two channels: aluminum plus organic fragments and aluminummonomethyl plus organic fragments. The ratio [A1]/[AICH3] is wavelength dependent. Finally, we present a mechanism to explain the photolysis of trimethyl compounds of group III elements (Al,Ga,In).
Fine Metal Particle Formation from Organometallic Compounds by Laser Ignited Mild Explosive Reaction
Authors: Shimo Nobuo , Yoshihara Keitaro 
Published: March 2011

ABSTRACTFine metal particles are deposited on a surface by explosive decomposition of organometallic compounds with single pulse laser irradiation. This new technique has the following characteristics:(1) High quantum efficiency of ca. 105, that depends on the size of the reaction chamber used and the concentration of organometallic compounds.(2) Formation of uniform spherical particles of ca. 0.3 µm size under some reaction conditions.(3) Rapid formation of metal particles. Most of the starting materials are decomposed within a few miliseconds.The key points of this decomposition reaction are:(1) Formation of high density active species in the gas phase by the irradiation with high power lasers.(2) Propagation of a thermal chain reaction.
Indentation Technique to Investigate Elastic Moduli of Thin Films on Substrates
Authors: Stone D. S. , Wu T. W. , Alexopoulos P.-S. , Lafontaine W. R. 
Published: March 2011

AbstractClosed-form elasticity solutions are introduced, that predict the average displacement beneath square and triangular, uniformly loaded areas at the surface of a bilayer. The solutions aid in the application of depth-sensing indentation techniques for measuring thin film elastic moduli. The elasticity solutions agree closely with experimental data of Al, Si, 1 μm Al on Si, and 2 μm Cr on Si. The case of poor adhesion between the film and substrate is briefly examined.
Substrate Step Induced Strain in Heteroepitaxial Growth
Authors: Lambrecht W. R. L. , Segall B. , Pirouz P. 
Published: March 2011

AbstractDuring epitaxial growth of lattice-mismatched materials, substrate surface steps induce vertical misfit between substrate and epilayer. It is shown that the resulting strain is accomodated by an interface dislocation, which is of the Read-Shockley type for a complete step and supplemetary displacement type for a demistep, using R.C. Pond's classification. Alternative models for the strain accomodation are considered. A localized “displacement boundary” is shown to be unfavorable irrespective of the film-thickness. Residual shear strain in the film requires debonding from the substrate, which is shown to be unfavorable with respect to the dislocation model. The distribution of strain between film and substrate is shown to depend weakly on film-thickness but strongly on the material's elastic constants.
Delamination of LPD Tungsten Films by Residual Stress
Authors: Borer A. , Derby B. , May I. 
Published: March 2011

AbstractThin tungsten films have been deposited on sapphire and glass substrates using laser photolytic deposition from a tungsten hexa-fluoride precursor. Failure of the films is caused by the presence of large residual stresses (1–5 GPa). Compressive and tensile stresses are found at different stages of film growth and either may be responsible for delamination. Early compression is caused by oxidation and impurity influenced intrinsic stress. Tensile stress occurs with microstructural changes but is not maintained with film growth. Large stress gradients, indicative of up to 0.75–1.2% lattice strain difference across the film, are found through both compressive and tensile films and are not explained.
Ion Channeling Studies of CdTe Films on GaAs
Authors: Wilkens Barry 
Published: March 2011

AbstractThin films of [111] oriented CdTe have been MOCVD grown onto [111] GaAs substrates. When thicknesses exceed 1000Å the epitaxy is quite good (backscattering minimum yield of approximately 15%) in spite of a 14% lattice mismatch. A narrowing of the Cd angular scan suggests a displacement of some of the Cd atoms in the lattice. A model based on a Te vacancy is presented to describe the data.
The Effects of Intrinsic In-Plane Stress on the Local Atomic Structure of Thermally Grown SiO2
Authors: Fitch J. T. , Bjorkman C. H. , Sumakeris J J , Lucovsky G. 
Published: March 2011

AbstractThe effect of thermal history on the local atomic structure of thermally grown and annealed SiO2 films is discussed. Thin films of SiO2 were prepared for study by (1) thermal oxidation of silicon at 850°C and 1050°C in a dry oxygen ambient and, (2) by subsequent rapid thermal annealing at temperatures between 850°C and 1200°C. After thermal processing, the film thickness was reduced incrementally by a wet chemical etchback technique to within 50 Å of the growth interface. Relief of intrinsic growth stress by viscous flow was investigated, at each thickness increment, on a local atomic scale by infrared spectroscopy and on a macroscopic scale by beam-bending type stress measurements. Results were analyzed in terms of a Maxwell model. Changes in film thickness and refractive index resulting from viscous flow during annealing were shown to obey a Clausius-Mossotti relationship. Local atomic strain values, calculated from shifts in the IR bond-stretching frequency, showed a linear correlation with measured stress values giving a value for a plane-strain Young's modulus of 4.7 × 1011 dynes/cm2. This compares favorably with the literature value of 8.8 × 1011 dynes/cm2.
X-Ray Diffraction Determination of Stresses in Thin Films
Authors: Vreeland T. , Dommann A. , Tsai C.-J. , Nicolet M.-A. 
Published: March 2011

AbstractThis paper presents the methodology employed in the determination of the stress tensor for thin crystalline films using x-ray rocking curves. Use of the same equipment for the determination of the average stress in poly- or non-crystalline thin films attached to a crystalline substrate is also discussed. In this case the lattice curvature of the substrate is determined by measurement of the shift In the Bragg peak with lateral position in the substrate.Strains in single crystal layers may be measured using Bragg diffraction from the layers and from the substrate or a reference crystal, with the highest strain sensitivity of any known technique. The difference in Bragg angles for a strained and an unstrained crystal is related to the change in d spacing of the Bragg planes, and the elastic strain is related to'this angular difference. The separation of two peaks on an x-ray rocking curve is generally not equal to the difference in Bragg angles of two diffracting crystals, so diffractometer measurements must be carefully Interpreted in order to obtain x-ray strains in crystalline films (x-ray strains are strains relative to the reference crystal). The unstrained d spacings of the film and the d spacings of the reference crystal must be known to obtain the elastic strains in the film, from which the stress tensor is determined.
Intrinsic Stress in a-Germanium Films Deposited by RF-Magnetron Sputtering
Authors: Fahnline D. , Yang B. , Vedam K. , Messier R. , Pilione L. 
Published: March 2011

AbstractThin a-Ge films deposited by rf-magnetron sputtering undergo a change from compressive to tensile stress as the argon gas pressure is increased. Spectroscopic ellipsometry, neutron activation analysis, and a dual laser beam reflection technique were used to determine the film's void fraction content, Ar/Ge atomic percent, and stress, respectively. The results of these three measurements indicate that as the film's Ar/Ge content increases, the void fraction decreases and the intrinsic stress becomes compressive. These findings are consistent with currently accepted bombardment mechanisms.
Behavior of Defects Related to Interface-Stresses in Model Submicron Soi Structures
Authors: Theodore N. D. , Carter C. B. , Arney S. C. , MacDonald N. C. 
Published: March 2011

AbstractThe origin and propagation of defects in novel submicron SOI structures have been investigated by transmission electron microscopy. The majority of the defect configurations observed could be explained in terms of dislocations generated as a result of stresses induced by the oxidation process. Dislocations were found to propagate into the silicon along particular {111} planes in conformity with stress-modelling. The examination of particular dislocation configurations allowed an estimation of the stresses at the silicon/ silicon dioxide interface. Defect densities were observed to depend on the geometry of the structures.