bluuebunny/crossref_metadata_2025 huggingface dataset:
Differences Between the Growth Kinetics of Thin Film and Bulk Diffusion Couples
Authors: Gösele U. , Tu K. N.
Published: March 2011

It is proposed that interface reaction barriers in binary A/B diffusion couples lead to the absence of phases predicted by the equilibrium phase diagram, provided that the diffusion zones are sufficiently thin (“thin film case”). With increasing thickness of the diffusion zones the influence of interface reaction barriers decreases and the simultaneous existence of diffusion-controlled growth of all equilibrium phases is expected (“bulk case”). First-phase and different modes of second-phase formation in the diffusion zones as well as the influence of impurities are discussed with specific reference to silicide formation. For this discussion the concept of a critical thickness of the first forming phase is introduced, below which a second compound phase cannot grow simultaneously with the first one.
Oxide Barriers to the Formation of Refractory Silicides
Authors: Silversmith D. J. , Rathman D. D. , Mountain R. W.
Published: March 2011

An investigation of the formation of refractory metal (tungsten, molybdenum and tantalum) silicides by reaction of the metal with crystalline and polycrystalline silicon at temperatures above 900°C indicates that WSi2 formation can be inhibited by certain processing techniques. These techniques utilize the growth of an SiO2 diffusion barrier about 20 Å thick on crystalline silicon and the deposition of tungsten films in vacuum ambients that will ensure oxygen incorporation (P ≥ 2 × 10−7 Torr). The reactivity of vacuum-deposited tungsten films results in the formation of an isolating oxide between the deposited silicon and tungsten films and the maintenance of the stability of the SiO2 diffusion barrier between tungsten films and a crystalline silicon substrate. This barrier is effective up to 1050°C in hydrogen ambients containing 15–20 ppm H2O. These procedures, however, are ineffective in preventing the formation of MoSi2 or TaSi2 at or above 900°C. A possible explanation for these results is that the tungsten film contains some level of oxygen due to the gettering of residual oxygen in the vacuum. In addition, the outgassing of the silicon source may enhance the level of oxygen at the evaporated W-Si interface. When the composite layer is annealed at high temperatures in a hydrogen ambient, the oxygen diffuses readily out of the bulk of the tungsten film to the interface, probably forming Sio2 which is more stable than WO3.The resulting thin SiO2 film has sufficient integrity to prevent silicon diffusion into the tungsten, thereby preventing WSi2 formation. This property of tungsten makes it inherently useful for buried-metal films in silicon devices.
Low Temperature Intermixing Reactions Between Silicon and Metals
Authors: Hiraki Akio , Narusawa T. , Gibson W. M.
Published: March 2011

Metal films such as gold, copper, nickel and palladium exhibit an interfacial intermixing reaction at room temperature with semiconductors with energy gaps Eg less than about 2.5 eV or dielectric constants ε larger than about 81. We have proposed a model2 of the triggering mechanism of this interfacial reaction based on the ability of a metal to screen coulombic interaction by its mobile free electrons. Such a screening may disturb the electron distribution responsible for the covalent bonding, and consequently it may make the semiconductor surface reactive towards the metal. In this respect, there must be a critical film thickness for the deposited metal film to behave as a true metal with sufficient mobile free electrons for the screening; therefore the reactivity of the semiconductor surface for the intermixing reaction must be dependent on the thickness of the deposited metal film. In favour of the screening model, we show that the reactivity of a silicon surface for intermixing or silicide formation with a gold or palladium film depends clearly on the film thickness.
Atomistic Simulation of Low-Energy Beam Deposition
Authors: Dodson Brian W.
Published: March 2011

Low-energy (50 eV) homoepitaxial beam deposition of silicon is simulated using many-body silicon potentials and molecular dynamics techniques. Results are presented for the case of a 50 eV neutral silicon beam incident on the (2×1) dimer reconstructed Si(100) surface. The beam is aligned along (110) symmetry directions, which are the most natural channeling directions in the silicon lattice. Roughly 10% of the incident beam atoms are scattered from the surface with a small fraction of their initial energy. About half of the incident atoms penetrate the lattice, but scatter strongly and come to rest within 10–15Å of the surface. The remainder are steered accurately into the bulk (110) channels, where they penetrate some 30–100 Å into the lattice. Those atoms which do not undergo bulk channeling cause considerable lattice damage to the near-surface (depth ≥10Å) region.
The Possible Importance of Pressure in Metastable Precipitate Formation in Ion Implanted Metals
Authors: Evans John H.
Published: March 2011

Prompted by the recent discovery that the heavier inert gas atoms implanted into metals precipitate in the solid phase, indicative of very high pressures (,>,1 GPa), the present paper discusses the conditions under which such pressures might be expected. The metal/inert gas results are briefly described and then used as a model to show that the two essential features apart from low or moderate metal temperatures, are the insolubility of the implanted species in the host matrix and its precipitation on a very fine scale. This combination suppresses the bias-driven cavity swelling that would otherwise control vacancy acquisition in an irradiation environment.

The extrapolation to other combinations of implanted ion and metal will be discussed. Where the implanted ion is insoluble and precipitates on a scale similar to the inert gas atoms, exact analogy suggests that the precipitates will again be under high pressure. The formation of high pressure phases might not be unexpected and could be a factor in explaining the presence of phases previously thought to be metastable.
Lattice Mode Study of La2CuO4-y Implanted with Sr
Authors: Ohana I. , Doll G. L. , Lusnikov A. , Withrow S. P. , Picone P. J. , Dresselhaus M. S. , Dresselhaus G. , Jenssen H. P. , Gabbe D. R.
Published: March 2011

Dramatic implantation-induced changes in the Raman and infrared spectra of polycrystalline samples of La2CuO4-y are reported for implantation of Sr in the fluence range 0.5 to 1.5 × 1016/cm2. The Raman and ir-reflectance spectra of the Sr implanted material reveal disorder-induced lines corresponding to breakdown of selection rules and to non-zone-center phonon modes. Whereas the main features in the Raman spectra of the implanted sample are broad disorder-induced lines centered at ∼ 560 ± 5 cm−1, reststrahlen lineshapes are observed above ∼ 800 cm−1 in the ir-reflectance spectra. After thermal annealing (550°C), the multiphonon lines in the ir spectra diminish, and the disorder-induced lines in the Raman spectra split to form well-resolved, sharper lines at 530 and 580 cm−1, identified with maxima in the phonon density of states. The sensitivity and complementarity of Raman and infrared spectroscopy to implantation-induced disorder and subsequent partial recovery by thermal annealing suggest that these techniques can be used to characterize sensitively disorder in ion implanted La2CuO4-y high Tc, materials.
A Study of Damage in Silicon Created By and P+ Implantation
Authors: Ziwei Fang , Chenglu Lin , Shihchang Tsou
Published: March 2011

The damage and annealing behavior of <100> Si implanted at room temperature by and P+ at different energies (5-600KeV) and intermediate dose (∼1014/cm2) has been investigated. Experimental results show that the damage created by implantation is always greater than that of P+ implantation. The ratio of total displaced atoms of the target cuased by molecular and atomic implantation, ND(mol)d/ND(atom) reached a maximal value at 100KeV () and 50KeV (P+) after rapid thermal annealing, the carrier concentration profiles measured by spreading resistance measurements are also different for the and P+ implanted samples. We attribute essentially this phenomenon to the displacement spike, but the multiple collision effect and the interaction between two molecular fragments should be considered while the incident energy is high.
Synthesis of Iron Oxynitride by Nitrogen Ion Implantation of Iron Oxide
Authors: Ogale S. B. , Teli Seema , Chopda Sunita , Phase D. M. , Kanetkar S. M.
Published: March 2011

The effect of N2+ ion implantation in ∝-Fe2O3 has been investigated by means of Conversion Electron Mossbauer Spectroscopy (CEMS). It Is shown that at a dose value of 1×1017 ions/cm2 and 3×1017 Ions/cm2 the samples exhibit new Interesting hyperfine features which can not be ascribed to known oxide or nitride phases. It Is thus concluded that Iron Oxynitrlde Is formed by the nitrogen Implantation process.
Characterisation of Ion Implanted and Thin Epitaxial Layer Structures Using Photoluminescence
Authors: Hamilton B. , Sedgwick T. O. , Gelpey J. C.
Published: March 2011

Photoluminescence (PL) measurements of thin rapidly annealed As implants have been made. The experimental conditions required to enhance the PL signal from the implant region have been established. Our data suggest that residual defects within the implanted volume can completely quench the PL signal. For the range of anneal times investigated (0.3s to 10s) we find that temperatures above 1050°C are needed to remove these defects. Anneal temperatures of 1350°C remove the defects sufficiently to allow us to observe strong PL from the implanted volume..
Solid Phase Epitaxy of Implanted Silicon by Electron Irradiation at Room Temperature
Authors: Lulli G. , Merli P. G. , Antisari M. Vittori
Published: March 2011

Solid-phase epitaxy of implanted Si is observed at room temperature during in situ electron irradiation in a Transmission Electron Microscope. Results obtained from irradiation of cross sections of samples containing different doping species show that: i) the basic mechanism of the process is the migration and recombination at the amorphous-crystalline interface of radiation defects coming both from the amorphous and crystalline side; ii) the diffusion length of such defects is of the order of 40 nm; iii) the regrowth rate is impurity dependent: a factor two exists between the faste
Temperature Dependence of Ion Assisted Epitaxial Growth of Chemical Vapor Deposited Si Layers
Authors: Ferla A. La , Rimini E. , Spinella C. , Ferla G.
Published: March 2011

Thin layers of Si were chemical vapor deposited onto as - received p-type <100> Si wafers and implanted with 80 KeV of As or Ge to a fluence of 1 × 1015 /cm2. Irradiation at 450°C with 600 KeV Kr++ ions causes the epitaxial growth of the entire deposited and amorphized Si layer. At lower irradiation temperatures the regrowth rate of the deposited layers is substantially reduced with respect that of the implanted amorphous layers. The presence of As enhances the regrowth rate of a factor 2.5. The results are explained qualitatively in terms of a dynamical bond breaking of SiO2, and of a dopant influence on the migration energy of the defects responsible for the growth.
Solid Phase Epitaxial Regrowth of Microcrystalline Si Films on a (100) Si Substrate
Authors: Roorda S. , Saito S. , Sinke W. C.
Published: March 2011

Microcrystalline Si, as produced by explosive crystallization of an amorphous Si layer on (100) Si, shows a two-stage annealing behaviour. Initially, solid phase epitaxial regrowth occurs very rapidly at temperatures at, or above 800°C. After a few seconds, the regrowth rate slows down to the value typical for alignment of poly-Si. Solid phase epitaxial regrowth of microcrystalline Si is suggested to be strongly dependent on grain size and structure.
Recrystallization Characteristics of Amorphous Si
Authors: Herring Rodney A. , Fiore Eric M.
Published: March 2011

The microstructure of high-energy (0.5–6.0 MEV) As-ion implanted Si and rapid thermal annnealed (RTA'd) Si has been studied by transmission electron microscopy (TEM). The implantations formed buried amorphous layers that recrystallized during RTA at different temperatures and became either single crystal or polycrystalline depending on their implation energy and fluence. At energies > 2.5 MeV and fluences < 1015cm−2, recrystallization occurred below 400°C and regowth was single crystal. At an energy of 6 MeV and fluence of 5 × 1015cm−2recrystallization occurred above 600°C and regrowth was polycrystalline. When the implantation energy and fluence were reduced to 0.5 MeV and 2 × 1014cm−2, respectively, recrystallization occurred above 600°C and regrowth was polycrystalline. The above results are explained by both the formation mechanisms of amorphous Si resulting from ion implantation and the structural order of a-Si.
On the Role of Interfacial Defect Sites During Solid Phase Epitaxial Regrowth of Implantation Amorphized Silicon
Authors: Adekoya W. O. , Hage-Ali M. , Muller J. C. , Siffert P.
Published: March 2011

We have studied the solid phase epitaxial regrowth (SPER) of implantation (31P+11B+ (73Ge+ preamorphized)) amorphized silicon in the temperature range 500–600°C induced by Rapid Thermal Annealing (RTA) using Rutherford Backscattering and channeling measurements (RBS). Our results show rate enhancements (≃ 3.5–6.5) of the velocities of regrowth in all studied cases with respect to literature-reported values for furnace-induced SPER. Also, the ratio VB/VP (velocity of regrowth in the presence of boron with respect to phosphorus) gives a value of approximately 3 in both RTA and furnace-induced kinetics. These results are explained by a model which takes into account the role of electrically-active interfacial defect sites during SPER.
Supercooling of Silicon and Germanium after Laser Melting
Authors: Stiffler S. R. , Thompson Michael O. , Peercy P. S.
Published: March 2011

Following pulsed laser melting, supercoolings of 505 K in Si and 430 K in Ge were observed prior to bulk nucleation. These large supercoolings are obtained because of the extremely high thermal quench which follows laser irradiation. Nucleation rates were estimated to be ∼1029 events/m3/s. Assuming that homogeneous nucleation was achieved, surface energies are estimated to be 0.34 J/m2 for Si and 0.24 J/m2 for Ge. These results are in reasonable agreement with traditional homogeneous nucleation experiments sensitive to rates of only ∼1010 events/m3/s. This laser melting technique is applicable to nucleation studies in a wide variety of materials.
Elastic Instability During Amorphization of Internetallic Compounds by Charged-Particle Beams
Authors: Okamoto P. R. , Rehn L. E. , Pearson J. , Bhadra R. , Grinsditch M.
Published: March 2011

Transmission electron microscopy (TEN) and Brillouin scattering methods were used to determine the lattice dilatation and shear elastic constant as a function of the degree of long-range order during room temperature irradiation of Zr3Al with 1.0-MeV Kr+. The results indicate that the onset of amorphization in Zr3Al is triggered by an elastic shear instability, and that the instability is directly related to the volume dilatation associated with the destruction of long-range order. It is also shown that the volume dependence of the shear elastic constant associated with radiation-induced disordering and amorphization is virtually identical to that associated with the heating to melting of many metals.
The Projectile Mass Dependence of the Amorphization Process and the Critical Temperature in the Ion Irradiated CuTi
Authors: Koike J. , Okamoto P. R. , Meshii M.
Published: March 2011

CuTi was irradiated with 1MeV Ne+ and Kr+ at various temperatures in the Argonne-HVEM interfaced to a tandem accelerator. The integrated intensity of diffuse ring was measured by a microdensitometer and analyzed by Gibbons model for the dose dependence of the amorphous volume. The results indicate that the direct amorphization occurs in a single damage zone with Kr+, but the overlapping of three damage zones is necessary with Ne+. The critical temperature for amorphization was 401±22K for Ne+ and 543±20K for Kr+, respectively. With Kr+, the critical temperature was nearly equal to the thermal crystallization temperature of an amorphous zone embedded in the crystalline matrix. Using the present observations, the relation between the amorphization process and the critical temperature is discussed.
Application of Onsager's Reciprocity Relations to Alloy Solidification
Authors: Kaplan Theodore , Aziz M. J. , Gray L. J.
Published: March 2011

A requirement of any theory for the kinetics of interface motion during a phase transformation is that the force law which relates fluxes to thermodynamic forces satisfies Onsager's reciprocity relations. In this paper we show how to apply Onsager's relations to a phase transformation mediated by a moving interface in a two-component system. We use the result to evaluate two proposed models for interface motion during alloy solidification.
Excimer Laser Etching of Cupric Oxide
Authors: Veen G. N. A. van , Vrijmoeth W. , Baller T. S. , Dieleman J.
Published: March 2011

Polycrystalline CuO samples are irradiated in UHV by excimer laser pulses at 308nm. Mass spectrometry combined with time-of-flight measurements is used to determine the composition of the desorbing particles and the desorption mechanisms. Additional information is provided by Scanning-Electron-Microscopy of the etched surfaces. At fluences below 1.8 J cm−2 the products Cu, O and O2 are desorbed by a purely thermal mechanism at temperatures up to 6000 K and a copper rich surface mask is formed. At higher power densities an additional ablative contribution is monitored which increases with power density, and much less surface area is covered by a Cu-rich mask.
Key Issues Related to the Self-Aligned Formation of CoSi2 in a Salicide Process
Authors: Hove L. Van Den , Wolters R. , Geyselaers M. , Keersmaecker R. De , Declerck G.
Published: March 2011

The self-alignment of the Co-Si interaction at the edge of a Si-SiO2 transition has previously been ascribed to the fact that Co is the main moving species during silicide formation. However, the reactions in the Co-Si system are more complex. The phenomena of lateral silicidation and encroachment are therefore investigated at various stages of the Co/Si reaction using samples starting either from sputtered Co layers or from cosputtered Co-Si multilayers with varying average stoichiometries. The mechanisms resulting in the absence of lateral silicidation are clarified.
Initial Stages of Silicon Growth on the (100) Surface of Silicon By Localized Laser Cvd
Authors: Kotecki David E. , Herman Irving P.
Published: March 2011

This paper reports initial results of an experimental study of the early stages of silicon thin film growth on well prepared (100) c-Si surfaces by pyrolytic deposition from silane (SiH4) during localized laser chemical vapor deposition (LLCVD). The rate of silicon thin film growth during low pressure (< 10 Torr) deposition using tightly focussed laser beams (514.5 nm, ∼ 2.5 μm FWHM) is characterized and is shown to be much slower than expected based on the previously measured silane decomposition rate. Hybrid-heating experiments, in which laser heating induces a slight temperature increase on a uniformly heated substrate in the presence of silane gas, shows that growth is inhibited within the laser irradiation region. This result suggests that a nonpyrolytic mechanism contributes to silicon growth in laser CVD. Possible explanations for this nonpyrolytic growth mechanism are discussed.
Surface Chemical Reactions in the Mocvd of Aluminum Films
Authors: Bent Brian E. , Nuzzo Ralph G. , Dubois Lawrence H.
Published: March 2011

We have studied the deposition of aluminum films by triisobutylaluminum (TIBA) pyrolysis on clean and oxidized Si(lll) (7×7), Si(100) (2×1), and an evaporated aluminum film on silicon. On all of the silicon surfaces, HBA has a very low reaction probability (<0.01). On aluminum, the reaction probability is much higher, and the rate of steady state aluminum deposition is limited by β-hydride elimination from surface-bound isobutyl species to give isobutene and hydrogen. In the steady state deposition of aluminum on top of silicon, gas phase silanes such as isobutyl- and diisobutylsilane are also evolved. This clearly indicates that hydrogen and alkyl ligand transfer from aluminum to silicon (which has diffused up through the growing aluminum film) can occur. We have also found that alkyl species generated on aluminum surfaces by. the adsorption of alkyl iodides have surface chemistries analogous to the aluminum alkyl ligands.
Surface Chemical Modification for Via-Hole Filling Using Tri-Isobutylaluminum Chemical Vapor Deposition
Authors: Fleming C. G. , Blonder G. E. , Higashi G. S.
Published: March 2011

Tri-isobutylaluminum decomposition occurs preferentially on aluminum rather than silicon oxide surfaces. This preference might be exploited to fill via holes for multi-level integrated circuit metallizations. Initially a KrF excimer laser (248 nm) was used to sensitize aluminum pads in the base of the via holes. However, depending on the chemical treatment of the surface, it was discovered that laser enhanced activation was not required to obtain nucleation. At 240”C spontaneous aluminum growth can be made to occur exclusively in the via holes simply by utilizing appropriate cleaning methods. This technique was used successfully to fill via holes 1 μπι in diameter and 0.7 μπι deep with aluminum plugs. Selectivity is excellent, but chamber contamination can result in random nucleation. Technical problems still to be over come include grain growth morphology, 100 % via hole activation and better control of nucleation selectivity.
Al/Si Interface Characteristics Formed by Partially Ionized Beam Deposition at 2.5Kv
Authors: Wong J. , Lam C. , Lu T.-M.
Published: March 2011

Partially ionized beam (PIB) deposition technique was used to deposit Al thin film on Si(n) substrate. The fabricated Schottky diodes showed an anomalous C-V characteristics for the Al films deposited with a bias potential equal to 2.5kV. The 1/C2 vs. V plot showed a drastic decrease in the slope as compared to the diodes deposited without the bias potential. Further measurements showed a frequency dependence in the C-V characteristics. This anomalous C-V characteristics can be explained by the formation of a p-n junction diode underneath the Si surface. A model of self-ion implantation which explains the formation of this surface p-layer on the Si(n) substrate is proposed and tested.
Laser-Stimulated Noble Metal Deposition From Gaseous and Condensed Acetylacetonates. Photoreactions in the Supersonic Jet and Above Silicon
Authors: Heidberg Joachim , Daghighi-Ruhi Rahman , Von Weyssenhoff Hanns , Habekost Achim
Published: March 2011

Laser-stimulated deposition from the acetylacetonates of Pt and Ir has been found to take place on silicon surfaces. The gas phase photoreactions have been observed in a supersonic free jet TOF mass spectrometer and above silicon. The bare metal ions and metal cluster ions are formed from the complexes in the gas by multiphoton excitation. On the substrates deposits are detected by microprobe analysis with a metal content higher than 95 %.
Also from condensed complexes laser-induced metal deposition, and as competitive process photodesorption, takes place.
Laser Induced Forward Transfer
Authors: Baseman R.J. , Gupta A. , Sausa R.C. , Progler C.
Published: March 2011

The laser induced forward transfer (LIFT) technique employs a pulsed laser to transfer material, originally precoated as a thin film on a transparent support, from that support onto a selected target substrate. LIFT has been used to deposit a variety of thin films, thick films through the repetitive transfer of thin films, multilayer structures through the transfer of appropriately layered precoated films, and metal silicon alloys.
An Analysis of the Effect of System Variables on the Quality of Thin Films and Powders Produced by Laser-Breakdown Chemical Vapor Deposition
Authors: Joyce E.L. , Jervis T.R.
Published: March 2011

A gas phase process for large area depositions on an ambient temperature substrate using laser-induced dielectric breakdown of gas phase precursors has recently been developed.1 Deposits of nickel alloys show excellent grain refinement (<10 nm) and metastable phase incorporation due to rapid quenching from the gas phase. Particle size distribution and compositional variance within the deposited films have been studied using electron microscopy and electron diffraction. Kinetic expressions to explain homogeneous gas phase nucleation and growth of the deposited materials have been developed in an effort to better understand this process. The effect of system variables on film and powder grain sizes has been studied. This analysis gives insight into the fluid flow/heat transfer patterns involved in the system and their effect on the final deposited material. The effect of system pressure, gas phase composition, and laser pulse energy, on particle size, surface area coverage, and deposition thickness are discussed.
Two-Photon Absorption Cross Section for Silane Under Pulsed Arf (193 nm) Excimer Laser Irradiation
Authors: Fuchs C. , Boch E. , Fogarassy E. , Aka B. , Siffert P.
Published: March 2011

We have determined for the first time, the two-photon absorption cross-section of silane at 193 nm, by measuring directly the fraction of incident light absorbed in the gas phase during the irradiation with a pulsed ArF excimer laser.
Deposition of Amorphous Carbon Films by Laser Induced CVD
Authors: Tachibana H. , Nakaue A. , Kavate Y.
Published: March 2011

Amorphous carbon (a-C) films were prepared by photodissociation of C2H3Cl or CCl4 gas using a pulsed ArF excimer laser (193nm). An increase in the substrate teiperature decreased the deposition rate. For C2H3Cl4 the maximum deposition rate of 10Å/min was attained at a partial pressure of 0.1 Torr and room temperature. In contrast, for CCl4, the maximum deposition rate of 10Å/Min was obtained at a partial pressure of 3 Torr and room temperature. This difference may be attributed to the different absorption cross sections for the two gases. The structural and mechanical properties were leasured. An Auger analysis showed the chlorine content in the a-C film deposited at room temperature to be 1% for C2H3Cl and 8% for CCl4. The Mohs hardnesses of the a-C filis deposited at room teiperature were 7 and 2 for C2H3Cl and CCl4, respectively. It was concluded that both sp2 and sp3 bonds existed between neighboring C atoms at low temperatures, whereas SP2 bond was predominant at temperatures higher than 300°C.
Multispectral Spectroscopic Ellipsometry-A New Tool for In Situ Surface Analysis
Authors: Ferrjeu F. , Stehle J.L. , Bernoux F. , Thomas O.
Published: March 2011

Spectroscopie ellipsometry is a non-destructive tool for physical characterization without prior preparation of materials.Real time, in-situ measurements can be applied to analyze surface problems, to optimize thin film processing and even to monitor epitaxial growth or thin film deposition. Spectroscopie Eilipsometers built by SOPRA are described. A new instrument using Optical Multi-channel Analysis,(OMA), with a spectral range from 1.1 ev up to 4.8 ev which gives up to 11 ellipsometry spectra per second has been developed. Applications using Spectroscopie Ellipsometry are also discussed .
Laser-Induced Surface Modification and Etching of Materials
Authors: Bauerle D. , Eyett M. , Kolzer U. , Kullmer R. , Mogyorosi P. , Piglmayer K.
Published: March 2011

Laser-induced surface reduction and ablation of piezoelectric oxides is described for the examples of BaTi03 and LiNb03.

The microscopic mechanisms involved in the laser-induced etching of single-crystal (100) Si in Cl2 atmosphere are investigated for the regime of low laser powers.
Schottky Contact Characterization of Thin, Excimer Laser Grown Gaas Oxides
Authors: Schmidt M.T. , Yu C.F. , Podlesnik D.V. , Yang E.S. , Osgood R.M.
Published: March 2011

Thin GaAs-oxide layers have been formed on GaAs (100) surfaces using deep UV light to enhance the oxidation reactions. Two different oxidation reactions were compared by using UV light of wavelengths below and above the O2 dissociation limit, viz, 248 nm and 193 nm respectively. For the light above the O2 dissociation limit which causes ozone formation, oxides formed by direct surface illumination were compared to oxides formed by illumination parallel to the GaAs surface. Metal contacts were deposited in situ to study the effect of the various thin oxides on the Schottky barrier height of contacts to GaAs.
Surface Synthesis Via Laser-Liquid Reactions
Authors: Partridge Julian P. , Strutt Peter R.
Published: March 2011

The phenomena occurring when laser radiation interacts with a material submerged in a liquid depend on the power, wavelength, pulse duration, and liquid dielectric properties. Present studies, involving two distinctly different physical situations, show how some interaction modes can be used for surface modification. In the first, a continuouswave CO2laser-beam progressively pyrolyzes a liquid precursor to form a surface coating. Hexamethylcyclotrisilazane, for example, dissociates to produce highly adherent Si3N4 layers containing 200nm spherical particles. In the second physical situation, intense excimer laser radiation produces dielectric breakdown of the liquid, thus creating a high-temperature plasma and a high-pressure shock wave. Under these conditions, precursor decomposition products alloy the substrate to a depth of lum. Experiments above and below the substrate melt threshold have been used to determine the effects of processing in different power density regimes. A variety of analytical techniques have been employed to determine the compositions of the as-synthesised layers and mechanisms related to the observed phenomena are discussed.
Focused Ion Beam Sims for Micromachining Applications
Authors: Harriott L. R. , Vasile M. J.
Published: March 2011

A secondary ion mass spectrometry (SIMS) system has been incorporated into the AT&T-BL second generation focused ion beam (FIB) micromachining system. The primary applications are end-point detection and topographical element mapping. End-point detection of Cr micromachining on photomasks was done with raster sizes ranging from 10 μm x 10 μm to 3 μm x 3 μm. SIMS end-points, total ions images, and transmitted light measurements show that the ion-milling can be controlled to stop prior to or after the Cr/glass interface. Mass selected secondary ion images have been obtained for high yield ions such as52Cr+ and27 A1+ on raster fields of 25 μm in time intervals ranging from 20 to 100 sec. Al+ SIMS images of 1 μm lines and spaces from a VLSI test pattern have been obtained.
Room Temperature Uv Laser Continuous Direct Writing of Al From Tma
Authors: Bouree J.E. , Flicstein J.
Published: March 2011

Aluminum lines have been drawn at a writing speed of 3.8 μm/s on (100) p-type Si by UV laser-assisted chemical processing, from a flow of TMA diluted in H2. These results are the experimental proof of direct writing at room temperature due to a single-step deposition process induced by a single light source. The useful (30 μQ-cm) ohmic-type resistivity obtained depends strongly on the photolytic process parameters.
Photoluminescent Properties of ZnO Layers Prepared by Organometallic Chemical Vapor Deposition
Authors: Bethke S. , Pan H-C , Wessels B. W.
Published: March 2011

ZnO layers have been heteroepitaxially deposited on sapphire using organometallic chemical vapor deposition at atmospheric pressure. The quality of the layers was assessed using photoluminescence spectroscopy at 16K. The layers exhibited strong ultraviolet near bandedge luminescence. The dependence of near bandedge and deep level photoluminescence emission on deposition conditions was examined.
DCD and Low T Pl Determination of Bandgap Dependence on Composition for Mocvd Grown InGaAs/InP
Authors: Bassignana I. C. , Miner C. J. , Puetz N.
Published: March 2011

This work reports a detailed study of the bound exciton recombination energy measured by low temperature (7K) photoluminescence, as a function of the relative lattice mismatch between the InGaAs epitaxial layers and the substrate measured by double crystal x-ray diffraction. Nominally undoped lμm and 2μm epitaxial layers of InGaAs/InP were grown by metal organic chemical vapor deposition (MOCVD). All InGaAs epitaxial layers used in this study show a single narrow rocking curve peak (FWHM < 25 arc-sec) and only a single narrow PL peak (FWHM < 2.5 meV). Near lattice match the PL energy varies linearly with the mismatch but the absolute value of the PL energy at lattice match is a function of the type of substrate used.
Tem Studies of GaAs/AlGaAs Heterostructures Grown on Patterned Substrates
Authors: Hwang D. M. , Kapon E. , Tamargo M. C. , Harbison J. P. , Bhat R. , Nazar L.
Published: March 2011

Epitaxical growth rates depend strongly on the crystalline orientations of substrate surfaces. Multilayer growth on pre-patterned substrates with various crystal facets exposed results in a large variation of layer thicknesses in the lateral direction. This lateral definition can be used in device applications. Alternating layers of GaAs and AIGaAs were grown by molecular beam epitaxy on (100) GaAs substrates patterned with grooves and ridges along the [01T] and [011] directions by chemical etching. The results were analyzed with transmission electron microscopy using vertical cross-section techniques. Examples of using this method to fabricate ridges with tips of atomic sharpness and quantum-well lasers are presented.
X-Ray Diffraction Study of a Thin GaAs Film on Si(100)
Authors: Bommannavar Arun S. , Sparks C. J. , Habenschuss A. , Ice G. E. , Dhere A. , Morkoc H. , Zabel H.
Published: March 2011

A 900A single crystalline GaAs film deposited by molecular beam epitaxy (MBE) on a silicon crystal cut 4.1° from (001) surface was characterized with X-ray diffraction measurements of the mosaic spread, particle size and strain distribution, and lattice parameter. The GaAs film had a larger mosaic spread in the direction of the steps of the silicon surface and coherent particle sizes of about 900 Å compared to the estimated film thickness of approximately 1000 Å. Superlattice reflections gave an ordered domain size of about 330 Å. There is a residual strain gradient in the film which is nearly linear with the lattice constant differing by about 0.044 Å between the surface of the film and its interface with the silicon substrate. Lattice parameter measurements indicate a small expansion of 0.13% perpendicular to the plane of the film.
The Influence of Current Stressing on the Structure of Ag Contacts to GaAs
Authors: Liliental-Weber Z. , Miret-Goutier A. , Newman N. , Jou C. , Spicer W.E. , Washburn J. , Weber E.R.
Published: March 2011

The stability of Ag Schottky contacts on GaAs after voltage and current stressing has been investigated. The barrier height and its stability against voltage and current stressing were found to depend on the diode fabrication method (metal deposition onto either air-exposed or ultrahigh vacuum cleaved (UHV) substrates). The barrier height of Ag diodes formed on air exposed surfaces is 0.96 eV, and a significant decrease of 70 meV was found upon exposure to voltage and current stressing. In contrast, the barrier height of Ag diode formed on UHV cleaved samples is 0.89 eV, and no significant change was found upon exposure to stressing. The structure of the contacts was studied by transmission electron microscopy. Ag deposited on UHV cleaved substrates shows an epitaxial relationship to GaAs and atomically flat interfaces. Exposure to air before the metal deposition led to nonuniform reactions and compound formation at the interface as compared to UHV samples. After current stressing, void formation and electromigration of Ag was observed in the air-exposed contacts. Ag contacts formed on UHV-cleaved GaAs (110) were stable during current stressing.
Islanding and Surface Diffusion in Semiconductor Heteroepitaxy: Ge on Si
Authors: Fisanick G. J. , Gossmann H.-J. , Kuo P.
Published: March 2011

Islanding and surface diffusion for Ge on Si(111)7×7 and Si(100)2×1 surfaces were examined in a UHV apparatus with in situ scanning Auger/SEM capabilities. At room-temperature uniform growth is observed, while elevated temperatures lead to Stranski-Krastanov growth with complex island size distributions. Extensive surface diffusion is observed on Si(100)2×l; however, surface diffusion is demonstrated to be extremely sensitive to contamination with carbon on the order of ≈0.05 ML, as well as to e-beam irradiation.
Epitaxial Growth and Band Structure Effects at the Si/Ge(111) Interface
Authors: Woicik J.C. , List R.S. , Pate B.B. , Pianetta P.
Published: March 2011

X-ray absorption fine structure, Auger electron spectroscopy and low energy electron diffraction have been used to study the evolution of the lattice constant and the degree of intermixing of thin (∼5 Å) silicon films grown on the germanium(111) surface by solid phase epitaxy. Our results indicate that as the system is annealed, the silicon intermixes with the germanium at elevated temperatures to form a pseudomorphic Si-Ge alloy with the germanium bulk lattice constant. We further observe a splitting of the ‘white line’ Is absorption edge in crystalling Si, SiGe and dilute (<10% silicon) SiGe. The measured splittings agree with band structure calculations for Si, SiGe, and Ge, respectively, indicating that the density of conduction band states of SiGe behaves as the interpolation between the states of Si and Ge. Qualitatively, our spectra may be interpreted in terms of a one electron picture without invoking many body excitonic effects. The absorption edge of amorphous silicon is also presented and the features of the density of states due to long versus short range order are extracted.
The Atomistic Nature of Compound Semiconductor Interfaces and the Role of Growth Interruption
Authors: Madhukar Anupan
Published: March 2011

An overview of the current understanding of the structural and chemical nature of interfaces involving an alloy layer, as revealed in photoluminescence and excitation spectra, is presented. Systematic studies, including reflection-highenergy- electron-diffraction measurements and computer simulations, reveal in-plane fluctuations in the alloy composition arising from the growth kinetics to be the dominant feature controlling the nature of the confining potentials in high quality samples grown without growth interruption. The role of surface kinetics in relaxing dynamic growth fronts to structurally smoother surfaces upon growth interruption is summarized and its pragmatic consequences for improving interface quality discussed.
Atomic Configuration of Coherent and Semicoherent Si/Ge Interface
Authors: Nandedkar A.S. , Narayan J.
Published: March 2011

Atomic positions near interfaces and defects are required to assess their physical properties. Their electronic properties can be calculated only after fixing the positions of atoms. The determination of atomic positions consists of three parts: (1) Theoretical calculations of atomic positions with appropriate interatomic potentials, (2) simulation of positions of atoms in the electron microscope, and (3) comparison of experimental results with the calculations. We have performed these three operations to determine atomic structures of coherent and semicoherent interfaces in Si/Ge systems. A coherent Si/Ge interface is simulated using a computer program. An edge dislocation is introduced at this interface with the help of elasticity theory. Energy minimization calculations are then carried out using interatomic potentials for germanium and silicon. The positions of atoms at the interface are thus determined. Critical phenomena in coherent and semicoherent interfaces are examined in relation to the strain energy of the system. For semicoherent interface containing dislocations, we can determine the critical thickness at which dislocations are generated. Energy minimization computations are found to play a major role in establishing critical phenomena. A model is also developed for the distribution of boron atoms near this dislocation. Isotropic elasticity theory is used for boron-dislocation interaction with correction factors inside the core to avoid singularities. Occupation probabilities of the atomic sites in the computational cell are calculated using the Fermi-Dirac distribution function. Interaction between boron atoms is neglected in the present analysis. Two configurations: 1. Si/Ge interface with a impurity free dislocation, and 2. the dislocation with boron impurities are then used to simulate high resolution images using the SHRLI computer program.
Investigation of the Promotion Effect of Germane in Low Temperature Uhv-Cvd Silicon
Authors: Uram Kevin J. , Meyerson Bernard S.
Published: March 2011

High quality, low defect density, single crystalline silicon/germanium alloys have been grown on Si(100) substrate wafers in a low temperature UHV-CVD reactor. Using a silane/germane gaseous source, the growth rate of the epitaxial layer increases from 4 angstroms/minute with no germane present to 82 angstroms/minute with 12.7% germane present in the reaction gas mixture at 550C. The germanium/silicon ratio in the deposited alloy is a factor of two greater than the germane/silane ratio in the reaction gas mixture. The kinetics of this effect are studied and correlation to UHV hydrogen thermal desorption from single crystal silicon-germanium alloys are made.
Stress Distribution and Critical Thickness of Thin Epitaxial Films
Authors: Sharan S. , Narayan J. , Jagannadham K.
Published: March 2011

We have calculated the stress distribution and critical thickness for the growth of strained epilayers having various values of misfit between the epilayer and the substrate. During formation of epitaxial films, the growth (pseudomorphic) occurs upto a certain thickness with planar spacing normal to the interface being essentially the same both in the substrate and the film. Above a critical thickness it becomes energetically favorable for the film to contain dislocations. This occurs usually by generating glide dislocations near the free surface because there is a lack of dislocation sources in mostly “defect-free” semiconductor materials. We present an analysis of the critical phenomena in semiconductors based upon this experimental fact. In all the previous analyses, the critical step associated with the generation of dislocations was neglected. We also consider finite (island) growth of thin films and its effect on critical phenomena. The experimental results show the presence of glide dislocations in Ge/Si with the extra half planes in silicon substrate.
Clustering in the Epitaxial Growth of GaAs ON Si
Authors: Zinke-Allmang Martin , Feldman L.C. , Nakahara S. , Patel J.R.
Published: March 2011

We report ion scattering and TEM investigations of the first layers of GaAs grown on clean Si(111). Based on observations of pure Ga cluster growth on As terminated Si(111) we propose a model for GaAs growth on Si, where Ga atoms are mobile and tend to cluster, but are immobilized by arriving As. These results establish conditions necessary for uniform film growth of GaAs/Si at the important film/substrate interface.
Chemical Beam Epitaxial Growth and Capacitance-Voltage Characterization of Si δ-Doped GaAs
Authors: Chiu T. H. , Schubert E. F. , Cunningham J. E. , Tsang W. T. , Tell B.
Published: March 2011

High quality GaAs layers have been grown by chemical beam epitaxy using triethylgallium and arsine. Undoped GaAs epilayer with net acceptor concentration NA - ND = 3}10 14cm-3 has been obtained at a low growth temperature of 500°C. Si dopant diffusion at such low temperature during growth is negligible. Using monolayer doping technique epilayers with Si impurities localized in a 2-dimensional plane were prepared. Capacitance-voltage profiling showed a high sheet electron concentration of lx1013cm-2 and peak widths of 22Å and 18Å at 300K and 77K, respectively, which are the narrowest ever reported. For samples grown or annealed at higher temperatures, significant impurity diffusion was observed.
Enhancements in Two Dimensional Electron Gas Density and Mobility in δ-Doped AiGaAs Heterostructures
Authors: Cunningham J. E. , Timp G. L , Schubert E. F. , Tsang W. T. , DeVegvar P. G. N. , Chiu T. H. , Agyekum E.
Published: March 2011

We report our recent investigations of a new structure formed by b-doping the barrier of an AlGaAs/GaAs heterostructure. In this new structure we have observed both a mobility of 1.9×lO6cm2/Vsec and the fractional quantum hall effect. We compare low temperature mobilities and densities achieved with the δ-doped heterostructure with corresponding high values reported in the literature for the homogeneously- doped heterostructure. We show that systematic enhancements in both density and mobility occur in the b-doped heterostructure. By δ-doping both barriers of a quantum well we have also achieved electron concentrations of 4×1012cm -2 in the well.
Comparative Study of Interface Structure in GaAs/AlAs Superlattices By Tem and Raman Scattering
Authors: Nakamura T. , Ikeda M. , Muto S. , Komiya S. , Umebu I.
Published: March 2011

Transition layers in GaAs/AlAs superlattices were studied by high resolution transmission electron microscopy (HRTEM) observations and Raman scattering measurements. We clarified that arrays of bright spots at the interface in the TEM image is a good indicator of the interfacial configuration and that a high atomic step density with intervals of less than 10 nm is necessary for Raman characterization using confined LO phonons.

We characterized the growth temperature dependence of the transition layers at the GaAs/AlAs interfaces. For a sample grown at 500'C, the extent of the transition layers is about one monolayer and that of the interfacial step intervals is more than 10 nm. For a sample grown at 700 0 C, these values are about two monolayers and less than 3 nm, respectively.
The Organometallic Epitaxy of Hgcdte for Infrared Detector Applications
Authors: Ghandhi S.K.
Published: March 2011

This paper reviews the requirements for mercury cadmium telluride material which is suitable for far infrared detectors. This is followed by substrate and reactor considerations, leading to its direct alloy growth by organometallic vapor phase epitaxy.

It is shown that HgCdTe can now be grown with electrical properties and areal compositional uniformity that are suitable for focal plane arrays, operating in the 10.6 Am range.
A Comparison of (100) Hg1−x Cdx Te and Hg1−x ZnxTe Grown By Molecular Beam Epitaxy
Authors: Feldman R. D. , Austin R. F. , Bridenbaugh P. M.
Published: March 2011

Films of HgCdTe with x < 0.6 and of HgZnTe with x < 0.26 have been grown by molecular beam epitaxy (MBE). Very high electron mobilities have been achieved for both materials in the small bandgap region. Hall mobilities at 77K reach 4.8 × 105 cm2 /V-s for Hg0 87 Zn0.13 Te, and 3.1 × 105 cm2/V-s for Hg0.87 Zn0.13 Te. HgCdTe growth was easily extended to the 1.5 – 3 μm wave length range. Attempts to extend HgZnTe to these bandgaps were unsuccessful due to defects that are induced by surface roughness in high Zn-content films. These results suggest that HgCdTe is the more suitable material for MBE growth for near infrared applications.
Role of Film-Substrate Interaction in Determining the Morphology of Thin Films
Authors: Grabow Marcia H. , Gilmer George H.
Published: March 2011

The equilibrium structure and metastable states of thin films have been investigated using molecular dynamics computer simulations. The energy as a function of coverage for a variety of film/substrate systems has been determined, and this information has been used to determine the growth mode and the conditions under which the film is dislocation free. In particular, the influence of the strength of the film-substrate binding will be discussed.