bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Dependence of Kr Precipitation in Ni
Authors: Birtcher R. C. , Liu A. S.
Published: March 2011

The precipitation of Kr injected into Ni at temperatures between 25 and 560 C has been studied with transmission electron microscopy. The Kr precipitates in cavities which increase in size with Kr fluence. Electron diffraction and dark-field imaging demonstrate that small Kr precipitates are solid, fcc crystals aligned with each other and the Ni lattice. The Kr is held in the solid state by the pressure generated by the cavity walls, and this pressure decreases with increasing cavity size. The mismatch between the Kr and Ni lattices is as large as 55%. The average Kr lattice parameter, determined from electron diffraction at room temperature, increases with increasing Kr fluence from 0.515 nm to an asymptotic value of about 0.545 nm for implantations at temperatures of 300 C or less. This increase towards an asymptotic limit is due to expansion of the Kr lattices as precipitates grow, until the decrease in cavity pressures allows melting of solid Kr in large cavities. Diffuse electron scattering was observed from liquid Kr in large precipitates for fluences greater than 5·1020Kr+m−2. Implantations at temperatures of 400 C or higher result in a bi-modal size distribution containing small solid precipitates and an additional population of larger, faceted precipitates, a larger average Kr lattice parameter for a given Kr fluence, and a higher asymptotic lattice parameter of 0.550 nm. Solid Kr seems to inhibit motion of small precipitates, and Kr melting is a precursor to faceting and growth by coalescence.
On the Trapping and Thermal Release of Low Energy Noble Gases Implanted into Silicon
Authors: Veen A. Van , Jong P. C. De , Bijkerk K. R. , Filius H. A. , Evans J. H.
Published: March 2011

Gas desorption spectrometry has been used to study the behavior of implanted noble gas ions in silicon. Results of low dose Ar implants followed by thermal desorption has shown the release of argon in Si from distinct surface related trapping sites, from substitutional argon (ArV) and from larger Ar-V clusters. This information gives an insight into the response of the silicon lattice to the Ar implants. For higher Ar doses, the effects of amorphization are clear in the desorption spectra and lead tò a method of measuring the recrystallization velocity during epitaxial regrowth (v=2×106 exp(−2.8 eV/kT). A similar value was found for thin sputtered Si films. The paper discusses high dose Ar saturation phenomena and describes the use of helium implants to probe defects and defect structures, such as bubbles and voids, in silicon.
Crystallographic Aspects of Low Energy Boron Implantation Into Silicon
Authors: Lever R. F. , Brannon K. W.
Published: March 2011

The computer program MARLOWE has been used to investigate low energy boron implantation into silicon. When implanted in a “random” direction at 5 keV, the most deeply penetrating ions are seen to have spent an appreciable part of their path travelling in <001>, <011> or <112> axial directions or in {111} or {220} planar channels. Channeling was then investigated more directly by observing the mean path travelled by the ions in the direction of incidence as a function of both azimuthal and tilt angles between the direction of incidence and the 001 direction. At 5 keV, {111} planar channeling and <110>, <112>, <111> and <100> axial channeling is prominent, with {220} planar and <310> and <114> axial channeling observed to a lesser degree. Higher order planar channeling such as {400}, {331}, {422} or (511} was not observed at 5 keV. At 0.75 keV only <110>. <100> and <112> axial channeling and {111} planar channeling remained.
Rutherford Backscattering Spectrometry Analysis of Shallow Sb-Implanted Si
Authors: Ridgway Mark C. , Whitton J. L. , Scanlon P. J. , Naem A. A.
Published: March 2011

Rapid thermal annealing (RTA) of shallow Sb-implanted Si has been studied with Rutherford Backscattering Spectrometry (RBS). Single crystal Si wafers were implanted with Sb at energies of 16, 32 and 48 keV and doses of 5×1014 and 1×1015/cm2. RTA and reference furnace anneals in a nitrogen atmosphere were done to activate the dopant and remove implantation damage. Glancing-angle RBS measurements were used to determine the Sb depth distributions. Dopant profiles obtained with RBS analysis were compared with Secondary Ion Mass Spectrometry results and TRIM code calculations. RBS measurements of the projected range and range straggle did not differ significantly from TRIM code calculations. Following annealing, significant Sb diffusion from the as-implanted peak was apparent. Sb accumulation at the substrate surface was pronounced, especially for furnace-annealed samples.
Mechanisms and Kinetics of Iion Beam-Induced Compositional Modifications
Authors: Lam N. Q.
Published: March 2011

Near-surface compositional modification of ion-bombarded alloys results from the dynamic interplay of several atomistic processes. In addition to displacement mixing leading to t randomization of atomic locations, which is dominant at relatively low temperatures, and preferential loss of alloying elements by sputtering, many thermally-activated processes, including radiation-enhanced diffusion, radiation-induced segregation and Gibbsian adsorption, also play important roles. The relative contributions of these processes to the evolution of the target composition profile depends on the target materials and irradiation variables. Although a good understanding of the individual processes has been achieved, information regarding their synergistic effects on alloy surface modification is still limited. In the present article, these processes will be characterized in simple physical terms, and the present understanding of their relative significance and contributions in changing the target composition during ion bombardment will be discussed in view of recent progress in theoretical modeling and experimental study.
Study of Boron Implantation in CdTe
Authors: Jamieson D. N. , Bowman R. C. , Adams P. M. , Knudsen J. F. , Downing R. G.
Published: March 2011

The effect of large dose boron implantation in single crystal CdTe has been investigated by Rutherford Backscattering Spectrometry with channeling (RBS), double crystal x-ray diffraction (DCD) and photoreflectance spectroscopy (PR). Comparisons are made with the results of identical B implantations of Si and GaAs crystals. Multiple energy implantations were performed at room temperature and liquid nitrogen temperature with total doses up to 1.5×1016 B+ ions/cm2. The implanted B distribution was measured with neutron depth profiling (NDP) and found to agree well with Monte-Carlo ion range calculations. The RBS results showed that the CdTe crystals had not been rendered completely amorphous even for the highest dose implantation, unlike GaAs and Si. Furthermore, the DCD results showed little implantation induced structure in the rocking curves from the implanted CdTe crystals, in contrast to GaAs. The consequences of annealing at 500°C in an attempt to regrow the crystal structure are also discussed.
Channeling Investigation of the Lattice Location of Ti in Ti-Implanted Optical Waveguides in LiNbO3
Authors: Buchal Ch. , Mantl S. , Thomas D. K.
Published: March 2011

Ion channeling of 3 MeV He ions has been employed to investigate the lattice location of Ti in Ti implanted optical waveguides in LiNbO3 after Solid Phase Epitaxy. Particle-Induced X-rays (PIXE) from Ti at 4.5 keY (K∝) and Nb at 2.2 keV (L∝β) and 16.6 keV (K∝) have been detected and analyzed simultaneously.

All scans yield similar behaviour of the Ti and the Nb signals. This provides clear evidence, that within well annealed implanted waveguides the Ti4+ and the Nb5+ ions occupy equivalent lattice positions.
Photoluminescence Spectra of C+-Implanted GaAs: Experimental Verification on Amphoteric Features of Carbon Impurities in GaAs
Authors: Makita Yunosuke , Shigetomi Shigeru , Mori Masahiko , Ohnishi Nobukazu , Phelan Paul , Matsumori Tokue
Published: March 2011

C+ ion-implantation was carried out for extremely pure GaAs gown by moleplar Ieam epitaxy. The dose was very widely varied from 1×1015 to 1×1020 cm−3. Photoluminescence and Raman scattering measurements were performed at 2 K and room temperature, respectively, both as functions of dose and annealing temperature. The results revealed that for a dose less than 5×1017 cm−3, where the dominant damages are point defects, annealing at 200°C is sufficient to attain a damage-free lattice. When the dose is above that value, where the principal damage is a highly disordered lattice, annealing, at least above 550°C, is required. Photoluminescence spectra showed that the well-defined near-band-gap emission, [g-g], (exclusively inherent to acceptors), was a dominant emission in the above mentioned low dose region, but was strongly suppressed in the higher region. These observations indicate that ion-implanted C atoms in GaAs behave as amphoteric impurities when the dose exceeds a critical value, of around 5×1017 cm−3.
Transition State Model for Grain Boundary Motion During Ion Bombardment
Authors: Atwater Harry A. , Thompsonm Carl V. , Smith Henry I.
Published: March 2011

Ion bombardment of polycrystalline Ge, Si, and Au films leads to rates of grain boundary motion that greatly exceed rates of thermally-induced motion at the same temperature and which exhibit a weak temperature dependence. The enhanced migration rate is proportional to the rate of energy deposition in nuclear collisions at or very near the grain boundary. Experimental work is reviewed, and a transition state model is presented which accounts for the observed kinetics of grain boundary migration during bombardment. This model suggests that the rate limiting step in grain boundary motion may be thermally-induced migration of a bombardment-generated defect across the boundary. Also, the ratio of atomic jumps at grain boundaries to the local collision-induced Frenkel defect generation rate is shown to be characteristic of each material, but independent of ion mass and ion flux. The model is extended to the motion of an interface between two phases, and applications to crystallization during ion bombardment are discussed.
Ion Irradiation Induced Grain Growth in Metal Thin Films
Authors: Liu Joyce. C. , Mayer J. W.
Published: March 2011

The dependence of ion irradiation induced grain growth on collision and material properties were studied in metal and alloy thin films. The uniform grain size increased with ion dose in the low dose regime; and the growth saturated in the high dose regime. The saturated grain size was determined 'by the cascade dimension as well as the atomic mobility. The growth was further influenced by the temperature, composition and impurity.
Amorphization of Silicon by Ion Irradiation: The Role of the Divacancy
Authors: Elliman R. G. , Linnros J. , Brown W. L.
Published: March 2011

Fixed fluence ion irradiation of silicon is shown to produce either defected crystal or amorphous silicon depending on the ion flux employed. The amorphous threshold flux, defined as the minimum flux required to generate a continuous amorphous layer for a fixed fluence irradiation, is measured as a function of irradiation temperature. This critical flux for amorphization is shown to satisfy an Arrhenius expression with a unique activation energy of ∼1.2eV, which corresponds to the migration/dissociation energy of the silicon divacancy. These observations lead to the conclusion that the stability of the silicon divacancy controls the competition between defect production and dynamic defect annealing, and hence the crystalline to amorphous phase transformation.
Pulsed Ion Beam Induced Crystallization and Amorphization of Silicon
Authors: Linnros Jan , Brown W. L. , Elliman R. G.
Published: March 2011

The ion-bombardment-induced movement of an amorphous/crystalline interface in silicon has been studied under pulsed beam conditions. Irradiations were performed with a 1.5 MeV Xe beam at temperatures of 200–300°C which induced a planar motion of the interface, either to epitaxially crystallize the amorphous material or to planar amorphize the crystalline material. It is found that at a fixed peak and average beam current the result of pulsed irradiation can vary from amorphization at low pulse repetition frequency to crystallization at high pulse repetition frequency. The frequency which characterizes this change in behavior is virtually temperature independent but strongly dependent on peak beam flux.
Segregation and Trapping of Gold During Ion-Induced Crystallization of Amorphous Si
Authors: Poate J. M. , Linnros J. , Priolo F. , Jacobson D. C. , Batstone J. L. , Thompson M. O.
Published: March 2011

A novel regime of crystal growth and segregation has been observed. Amorphous Si layers were uniformly doped with Au and epitaxial crystallization was induced in the temperature range 250–420°C using 2.5 MeV Ar ion irradiation. The Au segregation at the amorphous/crystal interface is analogous to behavior at liquid/solid interfaces except that the interfacial segregation coefficient of 0.007 at 320°C is independent of velocity between 0.6 and 6A/sec. This process results in the trapping of Au in crystalline Si at concentrations some ten orders of magnitude in excess of equilibrium concentration.
Amorphous to Polycrystalline Transformation in High Dose Ion Implanted Silicon
Authors: Nygren E. , Mccallum J. C. , Thornton R. , Williams J. S. , Olson G. L.
Published: March 2011

The amorphous to polycrystalline transformation of silicon implanted with high doses of In, Bi, Ga, and Sn is investigated. Each of these elements forms a low temperature eutectic with crystalline silicon and the details of the phase transformations in these systems are found to be very similar. A general model for the transformation based on the nature of the binary solutions is presented.
Precipitation, Phase Transformation, and Enhanced Diffusion in Ion-Implanted Silicon
Authors: Pennycook S. J. , Culbertson R. J. , Berger S. D.
Published: March 2011

Z-contrast scanning transmission electron microscopy has been used to study the connection between dopant precipitation and phase transformation in high dose In+ and Sb+ implanted Si. In the case of In, the observations confirm a heterogeneous nucleation model. Images of the precursor precipitates give the first measurement of the diffusion coefficient in amorphous Si, with an enhancement of 107 over tracer crystalline values. With Sb+ implants enhanced homogeneous nucleation is observed. The connection between these results and the transient enhanced diffusion observed in crystallized Si is discussed.
Time-Resolved Reflectivity Measurement of the Pressure-Enhanced Crystallization Rate of Amorphous Si in a Diamond Anvil Cell
Authors: Lu G. Q. , Nygren E. , Aziz M. J. , Turnbull D. , White C. W.
Published: March 2011

We have measured the pressure dependence of the solid phase epitaxial growth (SPEG) rate of self-implanted Si (100) by using the in-situ time-resolved reflectivity technique [1] in a hightemperature and high-pressure diamond anvil cell (DAC). With fluid argon as the pressure transmission medium, a clean and perfectly hydrostatic pressure environment is achieved around the sample. The external heating geometry employed in the DAC provides a uniform temperature across the sample. At temperatures in the range of 530 – 550 °C and pressure up to 50 kbars (5 GPa), the growth rate is enhanced by up to a factor of ten over that at 1 atmosphere pressure. The results are characterized by a negative activation volume of approximately −3.0 cm3/mole (−27% of the atomic volume). These preliminary results show a significantly weaker pressure dependence than does the previous work of Nygren et al. [2], who found an activation volume of −8.7 cm3/mole. The implications of these results for the nature of the defect responsible for thermal SPEG and irradiation enhanced SPEG is discussed.
Picosecond Laser Induced Melting: The Dielectric Function of Molten Silicon and Superheating in the Liquid Phase
Authors: Fauchet P. M. , Li K. D.
Published: March 2011

The complex dielectric function of molten silicon produced after picosecond illumination is found to be well described by a Drude model from 1.1 eV to 3.5 eV. Close to the melting temperature, we obtain ωp = 2.50 1016rad/s and τ = 212 10−18s. Transiently, the liquid temperature can exceed the melting temperature or even the boiling temperature Tb. We observe this transient heating and model it with a relatively simple computer code which includes superheating of the liquid above Tb. These measurements are possible thanks to a novel pump and probe technique.
Nanosecond Resolved Temperature Measurements Following Pulsed Laser Irradiation
Authors: Thompson Michael O.
Published: March 2011

A transient resistance technique has been developed which allows monitoring the temperature of a thin film sample at a fixed depth from the surface following pulsed laser irradiation. The technique utilizes the temperature dependence of a thin, electrically insulated, semiconducting or metallic layer. Temperature determinations with nanosecond resolution, an absolute accuracy of ±50 K, and a relative accuracy of ±5 K are demonstrated. Combined with simultaneous interface position and velocity measurements, the undercooling at the interface during rapid solidification may be obtained. Preliminary results using this technique during the solidification of thin Ge films are presented.
Computer Simulation of Laser-Induced Ultrarapid Phase Changes
Authors: Maclin Myron T. , Sabochick Michael J. , Mills James P.
Published: March 2011

The results of a molecular dynamics study of phase change in a system of condensed Lennard-Jones atoms is presented. These molecular dynamics results are compared to the rates of phase change predicted by two analytical phase change models. Both analytical models are supported by the molecular dynamics results.
A New Non-Equilibrium Molecular Dynamics Simulation Method for Rapid Solidification
Authors: Chokappa Dhanraj K. , Clancy Paulette
Published: March 2011

A new non-equilibrium Molecular Dynamics (NEMD) computer simulation method has been developed to study ultra-rapid melting and resolidification processes, e.g. laser annealing, ion implantation, etc. An atomic-level description of the material is combined with a new simulation technique to produce thermodynamic, structural and kinetic information as a function of time. Experimentally realistic values of the energy fluence, pulse duration and substrate temperature are used as input to the simulation. Rapid heat transfer simulating the action of the energy input is then set up allowing a complete prediction of the undercooling and associated kinetic properties. As such this new method offers the most realistic simulation model for rapid thermal processing to date.
Transient Structural Relaxation and Melting Temperature of Amorphous Silicon
Authors: Sinke W. C. , Warabisako T. , Miyao M. , Tokuyama T. , Roorda S. , Saris F. W.
Published: March 2011

The structure of ion-implanted a-Si has been studied using Raman spectroscopy. It is shown that the average bond-angle distortion and the strain energy stored in the random network vary drastically upon annealing. Relaxation is enhanced in the case of heating by laser irradiation. The results imply that the apparent melting temperature of a-Si may vary from one experiment to another, depending on the heating rate and -method.
Amorphous Phase Formation During Ion Mixing of Ti/Si Bilayers at Elevated Temperature
Authors: Maex K. , Keersmaecker R. F. De , rossum M. Van , Weg W. F. Van Der
Published: March 2011

The amorphous phaseformation in Ti-Si bilayers upon ion mixing at elevated temperatures and in Ti-Si multilayers upon thermal treatment was studied. In the case of ion mixing with 5×1015 cm−2 Xe atoms at temperatures around 240°C a 100nm thick amorphous Ti-Si alloy is formed with a very homogeneous Ti:Si=3 :4 composition. Thermal treatment of the Ti-Si multilayer structure at similar temperatures also yields amorphous silicide layers. The results are interpreted according to the evolution in a planar binary diffusion couple, where the Si and Ti concentrations in the reacted layer are dictated by thermodynamic and kinetic arguments.
Pulsed Laser Mixing of Metal Overlayers on Ceramics
Authors: Singh R. K. , Biunno N. , Narayan J.
Published: March 2011

Pulsed laser mixing has been used as surface modification technique for the improvement in the mechanical properties of ceramics. Thin metallic layers of nickel were deposited on structural silicon nitride and were irradiated with Xenon Chloride (XeCl) laser pulses. The laser parameters were optimized to lead to the formation of mixed layers. The mixed interfacial layers were analyzed using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Rutherford Backscattering (RBS) techniques. Detailed heat flow calculations were performed to simulate the effects of intense laser irradiation on metal coated ceramic structures. The melt lifetimes and the interfacial temperatures obtained using these calculations, were applied to understand the laser mixing phenomena occuring in these layered structures. Thermodynamics of chemical reactions between the metal overlayers and the substrate were done to predict the formation of mixed interfacial layers during laser irradiation.
Activation Characteristics of Implanted Dopants in InAs, GaSb and GaP After Rapid Thermal Annealing
Authors: Neida A. R. Von , Short K. T. , Brown J. M. , Pearton S. J.
Published: March 2011

We have studied in some detail the activation of implanted Si and Mg ions in InAs, GaSb and GaP after rapid thermal annealing. Even at doses of 1015 cm−2, the activation percentage of Mg is relatively high after optimum anneals -80% in GaP, 55% in GaSb and 45% in InAs. There is considerable outdiffusion of Mg in all three semiconductors for extended heat treatments. The amphoteric species Si shows good activation (60% for 1015 cm−2 dose) in InAs, a saturation electrically active concentration of ∼3 × 1013 cm−2 in GaP, and very low electrical activity in GaSb. The regrowth and damage removal characteristics in the three materials are similar to those of GaAs and InP.
Diffusion of Au in Amorphous Si During Ion-Beam Irradiation
Authors: Priolo F. , Poate J. M. , Jacobson D. C. , Linnros J. , Batstone J. L. , Campisano S. U.
Published: March 2011

We have measured the radiation-enhanced diffusion of Au in amorphous Si in the temperature range 77–700 K. Gold was implanted to depths of 500Å at concentrations of an atomic %. The samples were than amorphized to depths of -2μm using MeV Ar implants at liquid nitrogen temperature. Radiation-enhanced diffusion was induced by a 2.5 MeV Ar beam at doses of 2×1016−2×1017/cm2 and dose rates of 7×1012−7×1013/cm2sec. The diffusion coefficients show three well defined regions. At temperatures <400K diffusion is essentially athermal and due to ballistic mixing. At temperatures between 400K and 700K the diffusion, which is considerably enhanced over the usual thermal values, has an Arrhenius behavior with an activation energy of 0.37 eV. At higher temperatures thermal diffusion, with an activation energy of 1.42 eV, dominates.
Stokes/Anti-Stokes Raman Microprobe Analysis of Laser-Heated Silicon Microstructures on Silicon Dioxide
Authors: Pazionis Gregory D. , Tang Hua , Ge Lei , Herman Irving P.
Published: March 2011

Temperatures of laser-heated silicon microstructures on fused silica were determined by Stokes/anti-Stokes scattering using the 4880Å and 5145Å argon-ion laser lines, either separately or together to heat and probe the structure. Phonon shifts and broadening gave consistent measurements of temperature. Evaluation of temperatures from the ratio of Stokes/anti-Stokes intensities was shown to be sensitive to the details of scattering, collection, and detection.
Localized Laser-Assisted Deposition of Silicon,Silicon Nitride and Silicon Dioxide
Authors: Auvert Geoffrey , Pauleau Yves , Tonneau Didier
Published: March 2011

The localized laser-induced deposition of an insulator for silicon-based microelectronics seems to be an unsolved problem. In order to understand the limiting mechanism in the deposition, the formation kinetics of silicon, silicon oxide and silicon nitride using various laser wavelengths and gas mixtures have been studied Depending upon wavelength and laser-induced temperature, various chemical reactions are involved. In the presence of ammonia, the growth rate of silicon nitride dots was found to be lower than the corresponding silicon deposition rate, indicating that deposition starts with silane decomposition followed by nitridation of silicon. By evaluating the influence of the wavelengths, the existence of a photolytic aided reaction is detected in the presence of 2.4 eV photons. In the presence of oxygen molecules and under most experimental conditions, no deposition occurs. The formation of volatile intermediate compounds can explain the difficulty of locally depositing silicon dioxide.
Fundamentals of Laser Photochemistry for Surface Modification
Authors: Stake M. , Zhang Y. , Küper S.
Published: March 2011

Examples for the role of elementary photochemical processes for laser induced modification of surfaces by deposition - using aluminum-alkyls -, and etching - using excimer induced ablation - are described.
Adsorbed Tma on Dielectric Oxide Surfaces
Authors: Engelsberg A. C. , Chera J. J. , Korenowski G. M.
Published: March 2011

Trimethyl aluminum vapor is found to chemisorb on the surface of silicon dioxide and aluminum oxide via reaction with surface hydroxyl groupe. In addition to the chemisorbed layer, trimethyl aluminum also forms a weakly bound multilayer consisting of molecular dimers.
Distinguishing Laser Induced Thermal and Photochemical Surface Reactions by Photodeposit Morphology
Authors: Natzle Wesley C.
Published: March 2011

Cr containing deposits were formed by focussing a chopped (2000Hz) 325nm CW He-Cd laser on the inner surface of the quartz window of a cell containing 110-150 mTorr of Cr(C0)6 precursor. The deposit thickness and the chemical identity of contaminants were determined by stylus profilometry and attenuated total reflectance IR spectrometry. In certain regimes of incident laser power density, deposits exhibit a dual morphology, with a narrow inner deposit up to several microns in thickness on top of a wider deposit less than 0.16 microns in thickness. Changes in the morphology with incident power density and changes in transmitted and reflected light during the deposition enables assignment to photothermal and photochemical mechanisms. A deposition rate for each mechanism and an optical attenuation coefficient for the photochemical deposit at 325nm were determined from the deposit thicknesses as a function of time.
Excimer Laser Photolysis of Organometallic Compounds Adsorbed on Substrates
Authors: Suzuki Hideyuki , Mori Koji , Kawasaki Masahiro , Sato Hiroyasu
Published: March 2011

Excimer laser photolysis at 248 nm of trimethylgal1ium (TMG) was studied by probing gallium atoms by laser induced fluorescence (LIF) technique. From the dependence of LIF intensity on the excitation wavelength, temperature and pressure, a thermally assisted photodissociation in the chemisorbed state was concluded.
Mass Spectrometric Study of Laser-Induced Chemical Vapor Deposition of Gold
Authors: Kodas Toivo T. , Comita Paul B.
Published: March 2011

A modulated surface temperature technique was used to study the surface chemical reactions occurring during the laser-assisted deposition of gold from dimethyl gold hexafluoroacetylacetonate. An argon ion laser was chopped and used to modulate the surface temperature on an area roughly 1 mm in diameter on an alumina substrate. Reactant and products of the photothermal reaction were sampled through an orifice located at the center of the deposit and were then introduced directly into a quadrupole mass filter. Since the reactant concentration at the surface decreased when the laser turned on while the product concentration at the surface increased when the laser turned on, modulating the surface reaction rate and employing phase-sensitive detection allowed the identification of reaction products.
Excimer Laser Induced Micron-Size Pattern Etching By Image Projection
Authors: Brannon James H.
Published: March 2011

Patterned fine-line features as small as 0.8 microns have been etched in polyimide, silicon, and copper by use of ablative and chemical techniques. KrF excimer laser pattern etching was accomplished by use of a Kohler-type projection system employing a Uv refracting microscope objective. Ablative etching of polyimide was accomplished in air, while silicon and copper were chemically etched using the vapor of chlorine or carbon tetrachloride.
Effects of Excimer Laser Irradiation on Mbe and Mo-Mbe Growth of (Al)Gaas On Gaas And (Ca,Sr)F2/Gaas Substrates
Authors: Donnelly V. M. , Tu C. W. , Beggy J. C. , McCrary V. R. , Harris T. D. , Lamont M. G. , Baiocchi F. A. , Farrow R. C.
Published: March 2011

We report the growth of GaAs by laser-assisted molecular beam epitaxy, using As4 and either elemental Ga or triethylgallium (TEG) sources, and a 193 nm ArF excimer laser. Laser irradiation of (Al)GaAs has no effect on the growth rate or Ga-to-Al incorporation, when GaAs substrates and elemental group-III sources are used. When GaAs is grown from TEG, laser irradiation results in a selective-area film growth at temperatures below 450°C, where growth due to pyrolytic decomposition of TEG is very slow. The process is extremely efficient, with roughly unit probability for impinging TEG molecules sticking and being dissociated by laser radiation to form GaAs. From the strong dependence on laser fluence, the growth enhancement process appears to be pyrolytic in nature (due to rapid transient healing by the pulsed laser), and not photolytic. The cross section for photolysis must be at least ten times lower than the gas-phase value (9x10-18cm2). Using either Ga source, laser irradiation improves surface morphology and photoluminescence yields, compared to areas receiving less intense laser radiation.

In growth of GaAs from elemental sources on (Ca, Sr)F2 lattice-matched to GaAs, laser irradiation inhibits growth due to laser-induced thermal desorption of adsorbed Ga atoms, which are relatively weakly bound to (Ca,Sr)F2 compared to GaAs surfaces.
Recent Progress in Excimer Laser Lithography
Authors: Higashikawa I. , Nonaka M. , Sato T. , Nakase M. , Ito S. , Horioka K. , Horiike Y.
Published: March 2011

A KrF excimer laser exposure method has been developed for laboratory use, which employs 10 to 1 achromatic projection lens of 0.37 NA and 5x5 mm field size , and a TTL alignment system using the double diffraction method, which was realized by the use,of the achromatic lens. Novolak type mid-UV resists, such as AZ-5214 and PR-1024, were best suited for use in 248 nm exposure, considering the sensitivity and etching resistance from a practical viewpoint, and an additional post exposure baking process also improved the resist profile. The dependences of the exposure characteristics on the energy density per pulse and pulse frequency of these resists were not observed in the region of the practical exposure conditions. An alignment precision of x±30-= 0.2 μm was achieved for the alignment mark consisting of poly Si pattern. Thus, a 0.3 μm line and space pattern was realized by using tri-level resist process and a 0.2 μm gate pattern was successfully fabricated on the coplanar pattern with a 0.4 μm step.
Reactions in Omcvd: Detection of Gas Phase Radicals In Gaas Deposition Under Single Gas-Surface Collision Conditions
Authors: Squire D.W. , Dulcey C.S. , Lin M.C.
Published: March 2011

Laser ionization mass spectrometry has been used to study the deposition of gallium from trimethylgallium with and without AsH3. The apparent Arrhenius activation energy for the production of gas-phase methyl radicals from trimethylgallium is measured to be 28 ± 2 kcal/mol in the presence of AsH3, about the same value as measured in the absence of AsH3. At a substrate temperature of 1150 K where gallium desorption is substantial, addition of AsH3 is found to increase methyl radical yield but drastically decrease gallium atom desorption. A mechanism is presented to describe the deposition of GaAs at low pressures under single gas-surface collision conditions.
Excimer Laser Irradiation Effect on Metalorganic Molecular Beam Deposition of Al and Alas : Prospects for Laser-Assisted Epitaxial Growth of Gaalas
Authors: Tokumitsu Eisuke , Yamada Takumi , Konagai Makoto , Takahashi Kiyoshi
Published: March 2011

Triisobutylaluminum (TIBA) was used as an aluminum source for metalorganic molecular beam epitaxy (MOMBE). The optical absorption coefficient for TIBA was found to be larger than both tri ethyl aluminum and triethylgallium. TIBA was introduced into a laser-induced MOMBE system and selective deposition of Al and AlAs was carried out. Al metal was deposited on the area where the ArF excimer laser was irradiated and no deposition was observed without the excimer laser irradiation at a substrate temperature of 350 C. Furthermore, a laser large enhancement of the growth rate of AlAs was observed at 350 C.
Photo-Cvd Silicon Nitride for Gaas Mesfet Passivation
Authors: Padmanabhan R. , Miller B. J. , Tam G.
Published: March 2011

Silicon nitride films were deposited using a photochemical vapor deposition method. The defect density in these films was under 100/cm2 and the film adhesion was in excess of 104 psi. No lift-off was observed at power densities of up to 10 A/cm2 at applied voltages of up to 100. The film stress was compressive and under 5x103 psi. Total mobile ion concentration in the films did not exceed 109/cm2. Device analysis was carried out using Motorola dual gate MESFETs. Device degradation was evaluated in terms of surface potential sensitive parameters like source-drain current and resistance, by making comparisons in these parameters before and after passivation. Some degradation (up to 17 %) occurred in some of these parameters subsequent to device passivation. These results are comparable to or better than those encountered in most other low temperature films (like plasma enhanced CVD and polyimide films). The observed device properties are explained in terms of the film composition and the applicability of photo-CVD nitride films for MESFET passivation is discussed.
Laser-Assisted Liquid-Phase Etching of Copper Conductors and its Application to Advanced Integrated Circuit Interconnect
Authors: Miracky Robert F. , Doss Kantesh
Published: March 2011

We have demonstrated a method f or the selective-area, laser-assisted liquid-phase etching of 6-μm thick copper conductors, by focusing the 488-μm line of an argon ion laser onto the surface of samples immersed in a dilute solution containing sulfuric acid and hydrogen peroxide. Average etch rates of up to 5.0 μm/s have been achieved, in the process of completely severing 14-μm wide copper lines, with little attendant damage to the underlying layer of polyimide. Two etchant formulations were identified which exhibited large etch rates at elevated temperatures and low enough background etch rates (approximately 1 μm/hr at 0 °C) to be useful in practical applications.
Laser Chemical Etching of Metals in Neutral Salt Solutions
Authors: Datta M. , Romankiw L. T. , Vigliotti D. R. , von Gutfeld R. J.
Published: March 2011

We report the first results of experiments using a focused argon ion laser to locally induce chemical etching of steel and stainless steel in neutral salt solutions for maskless patterning. The solutions include sodium chloride, sodium nitrate and potassium sulfate. Vertical etch rates up to 4 microns/s are observed.
Control of Etching of LiNbO3, by Implant Damage Profile Tailoring
Authors: Brannon P. J. , Ashby C. I. H. , Arnold G. W.
Published: March 2011

Damage-profile tailoring using multi-energy ion implants can produce smooth side walls and deeper etched features with ion-bombardment-enhanced wet etching of LiNb03 than is possible with a single-energy implant. High ion fluences can produce buried microcracks which may contribute to propagation losses commonly observed in ion-implanted waveguides.
Laser-Initiated Aluminothermic Reaction Applied to Preparing Mo-Si Film on Silicon Substrates
Authors: Ding Li , Xuebiao Lu , Zhengzhuo Zhou , Mingxin Qiu , Chenglu Lin
Published: March 2011

Mo-Si films on silicon substrates has been prepared by the CO2 laser-initiated aluminothermic reaction. The features of these films have been characterized by RBS, AES, etc. The formation mechanism is discussed.
Rapid Thermal Annealing of Fib-Implanted Ga Shallow Impurity Profiles
Authors: Lin C-M. , Steckl A.J. , Chow T.P.
Published: March 2011

In this paper, we present the results of a study to fabricate shallow p+ n junction using Ga FIB implantation in conjunction with rapid thermal annealing (RTA). A focused 75 KeV ion beam with BO mA/cm2 current density and 0.5 μm beam diameter was used to implant Ga into (100) Si substrates at the doses from 1E13 to 5E15/cm2. The annealing temperature is from 600 °C to 1000 °C for various times, 10–30 sec. Secondary ion mass spectrometry (SIMS) and spreading resistance profiling (SRP) were used to measure the implanted Ga atomic and carrier concentration depth profiles. As compared to the conventional broad beam (BB) implantation, the FIB implanted impurity concentration depth profile has a longer tail and thus a deeper p+n junction. The damage generated by the high dose rate implantation is possibly responsible for this phenomenon. The results of SRP measurements of the FIB as-implanted samples show no Scif-anneal ing occured during implantations. p+n diodes fabricated using FIB exhibit good junction properties: ideality factor of 1.1, reverse–bias leakage current of below 5 nA/cm2 at -IV, and breakdown voltage of about 35 V.
Laser-Induced Metal Deposition on Silicon Membranes for X-Ray Lithography
Authors: Petzold H.-C. , Putzar R. , Weigmann U. , Wilke I.
Published: March 2011

The repair of clear defects on X-ray masks (2 urn Si membranes) requires the localized deposition of metal films with high aspect ratios and high X-ray opacity. Laser-induced heavy metal deposition from organometal-lic gas atmospheres has been investigated with respect to these requirements. An experimental comparison of pyrolytic (W) and photolytic (esp. W, Sn) depositions on thin Si membranes was performed to find out which of these two mechanisms is more favourable for X-ray mask repair. Using a simple model, the laser-induced temperature distribution in the membrane was calculated which strongly affects pyrolytic deposition. Although photolytic deposition tends to yield X-ray opacities below corresponding bulk values, this process turned out to be more suitable due to its better spatial resolution in this case of Si membranes used as substrates.
Direct Writing of Copper Lines From Copper Formate Film
Authors: Gupta Arunava , Jagannathan Rangarajan
Published: March 2011

The focused output from an argon ion laser (514 nm) has been used for direct writing of copper by photothermal decomposition of copper formate film on quartz and silicon substrates. The low decomposition temperature of the metallo-organic (∼200°C) allows deposition of fairlys thick copper lines at writing speeds as high as 10 mm/sec. The processing can be done in air since the rapid decomposition and cooling under scanning condition results in minimal oxidation of the deposited copper. The temperature distribution produced during laser writing on silicon substrate has been calculated to help explain some of the observed results.
Scanning Tunneing Microscope Study of Cadmiun Telluride
Authors: Kim H. S. , Zheng Y. C. , Bryant P. J.
Published: March 2011

Layered samples of cadmium telluride grown epitaxially on gallium arsenide substrates have been investigated by means of scanning tunneling microscopy (STM). The surface geometric and electronic structures are both of interest. Techniques were developed to remove the native oxide by etching, or to create a fresh surface by cleaving, and to protect them from oxidation by employing mineral or paraffin oil media. STM studies were conducted within the protective medium. These techniques were adapted and tested for both etched and cleaved samples of Si, CdTe and HgTe. The currentvoltage characteristics of the CdTe surface were investigated during dynamic changes of the tunnel current and barrier height while the probe-to-sample separation (gap) was static. Recorded values are shown for current versus bias for several constant gap values. A range of bias values has been employed to test a possible solution for the problem of interference between the contributions from geometric and electronic structure factors.
II–VI / III–V Heterostructures
Authors: Kolodziejski L. A. , Gunshor R. L. , Otsuka N. , Nurmikko A. V.
Published: March 2011

The integration of several optoelectronic device functions onto a common substrate material is an area which is currently being actively pursued. In an effort to achieve this objective, experiments are under way to examine the epitaxial growth and material properties of a variety of both II–VI and III–V compounds grown on a substrate where the II–VI/III–V heterostructure can be utilized. This paper describes some recent developments involving the molecular beam epitaxial (MBE) growth and characterization of two important II–VI/III–V heterostructures: ZnSe/GaAs and InSb/CdTe;. a comparison is made between epitaxial layer/substrate interfaces and epilayer/epilayer interfaces for both heterostructures. The ZnSe/GaAs heterointerface, having a 0.25% lattice constant mismatch, has potential for use in passivation of GaAs devices. The InSb/CdTe heterointerface possesses an even closer lattice match, ∼0.05% (comparable to the (Al,Ga)As/GaAs material system), and is motivated by possible device applications provided by InSb/CdTe quantum wells.
Room Temperature Optical Studies of GaAs/AlGaAs Coupled Double Quantum Wells
Authors: Jagannath C. , Elman B. , Koteles Emil S. , Chen Y. J. , Brown S. , Armiento C. A.
Published: March 2011

Room temperature photoreflectance (PR) spectroscopy has been utilized to study the effect of electric fields on the optical properties of GaAs/AlGaAs coupled double quantum wells (CDQWs). The behavior of optical transitions when subjected to electric fields ranging from 0 to 2×105V/cm, was found to be similar to that observed at low temperatures using photoluminescence excitation spectroscopy. Large shifts in the energies of spatially indirect transitions were observed when the CDQW was subjected to modest bias voltages.
Superlattice Optical Properties Measured by Variable Angle Spectroscopic Ellipsometry
Authors: Snyder P. G. , Merkel K. G. , De B. N. , Woollam J. A. , Langer D. W. , Stutz C. E. , Jones R. , Rai A. K. , Evans K.
Published: March 2011

Variable Angle of incidence Spectroscopic Ellipsometry (VASE) is a sensitive, nondestructive method of determining optical constants, layer thicknesses, alloy compositions and other parameters. We model the VASE data for a sample containing a 20 period Al0 5Ga0 5As-GaAs superlattice, to obtain the effective index of refraction (n) and e tinction coefficient (k) of the superlattice layer. The room temperature VASE spectra contain strong, sharp features at the e-hh(1), e-lh(1) and e-hh(2) excitonic tran-sition energies. In addition, VASE was used to characterize more compli-cated layered structures, which also contained superlattices.
Raman Scattering Characterization of GaAs-AlAs Superlattices Grown Along the [110] Direction
Authors: Kirillov D. , Pao Yi-Ching
Published: March 2011

Raman spectra of the GaAs-AlAs superlattice grown by molecular beam epi-taxy along the [110] direction were studied for the first time. The spectra were compared with spectra of the [100] superlattice and differences due to different crystallographic structure were analyzed. It was found that the energies of folded acoustical modes are higher in the [110] superlattice due to higher sound velocity in the [110] direction. Confined transverse optical phonons were a dominant feature of the spectrum of the [110] superlattice which allowed observation of the folding of transverse optical phonons. Stronger intensity of interface modes and lower intensity of folded acousti-cal modes in the [110] superlattice indicated that the quality of the layer interfaces was worse than in the [100] superlattice.
RHEED Intensity Oscillation Studies of the Kinetics of GaAs Deposition During Chemical Beam Epitaxy(CBE)
Authors: Robertson A. , Chiu T.H. , Tsang W.T. , Cunningham J.E.
Published: March 2011

Recently we have reported the measurement of RHEED intensity oscillations during Chemical Beam Epitaxy(CBE) of GaAs using triethylgallium(TEG) and As2 derived from an arsine cracker(Appl. Phys. Lett. 50(19), May 11,1987). The existence of RHEED intensity oscillations during CBE growth of GaAs indicates that over the range of conditions studied, growth proceeds via nucleation of islands which grow two-dimensionally as opposed to a vicinal step propagation mechanism. In the same study we observed a significant variation of the GaAs growth rate with substrate temperature at constant flux. In addition, the variation of growth rate with incident flux at constant temperature was found to be non-linear below approximately 500°C and linear above 500'C for incident fluxes yielding maximum growth rates between.2 and 1.8 monolayers/sec. Additional measurements of the dependence of the damping of RHEED intensity oscillations on V/11 ratio have indicated much less sensitivity of the growth front morphology to group V flux in CBE. This behavior is thought to reflect the role of highly mobile, partially saturated ethyl-gallium radicals in epitaxial growth by CBE. Measurements of As2 arrival rate limited intensity oscillations on gallium rich surfaces prepared by pyrolyzing TEG in the absence of As2 have shown that the pyrolysis of TEG is not self-limiting at 500°C and that excess gallium can be deposited on gallium rich surfaces. This paper also describes a simple model of the surface pyrolysis of TEG which is consistent with the above experimental observation.
Characterization and Physics of Threshold Voltage Dependence on Defect Related Properties of Channel-Buffer (Substrate) Interfaces in GaAs MESFET's Fabricated By Molecular Beam Epitaxy
Authors: Shenai K.
Published: March 2011

A fundamental understanding of the channel-buffer (substrate) interface is obtained from the experimental and theoretical investigation of long channel GaAs MESFET's fabricated by molecular beam epitaxy (MBE). The threshold voltage dependence on the semiconductor crystal lattice temperature indicates that the steady-state carrier trapping and accumulation of negative charge in donor-like states at the channel-buffer (substrate) interface play a detrimental role both in the linear and saturated regimes of device operation. The variations of the threshold voltage and gate capacitance with substrate bias are consistent with each other and suggest that significant reduction in the channel charge occurs with increased reverse bias on the substrate. The threshold voltage is found to decrease significantly as the sample temperature is increased both in the linear and saturated regimes of device operation.
Characterization of Mn-Doped in 1−x GaxAsyP1−y Grown By Lpee
Authors: Iyer Shanthi N. , Abul-Fadl Ali , Collis Ward J. , Khorrami Mohammad N.
Published: March 2011

Mn-doped In1−x GaxAsyP1−y epilayers lattice matched to InP substrate have been grown by the liquid phase electroepitaxial (LPEE) technique. The variation of growth velocity of the epilayers with current density and the doping characteristics of Mn in the epilayer has been studied. The temperature dependence of the hole concentration and the mobility has been analysed to determine the donor and acceptor densities, thermal activation energy of the level associated with Mn and the dominant scattering mechanisms that limit the hole mobility. The photoluminescence spectra of the doped epilayers are examined at 10K as a function of the excitation level.