bluuebunny/crossref_metadata_2025 huggingface dataset:
Interfacial Reactions of Titanium Thin Films on P+-Implanted (001)Si
Authors: Wan M. H. , Lur W. , Cheng H. C. , Chen L. J.
Published: March 2011

Interfacial reactions of titanium thin films on P+-implanted silicon have been studied by transmission electron microscopy.

The presence of titanium thin films on P+-implanted silicon was found to alter the defect configuration in the recrystallized layer. Interfacial reactions of titanium thin films on silicon were also found to be influenced by the presence of dopants as well as changes in the microstructures of the substrate. The results are compared with those found in previous studies of Ti thin films on ion-implanted silicon as well as on unimplanted samples. The mechanisms for the chaiiges in defect configuration and phase formation are discussed.
Optical Considerations for Excimer Projection Systems
Authors: Rothschild M. , Ehrlich D. J.
Published: March 2011

Excimer laser projection systems are expected to become widely used photolithographic tools, capable of high throughputs at resolution well below 0.5 iffli. The design of practical devices must overcome several challenges which are specific to the short wavelength, the laser performance and the photoresist response of such systems. This paper addresses the issues of UV optical materials, the effects of laser bandwidth on optical design, and the interrelationship between resist response, resolution, and laser pulse-to-pulse stability. It is shown how the various parameters are interconnected, and directions for further technological improvements are outlined.
Xps, Ups, and Hreels Studies of Excimer-Laser-Induced Dissociation of Al2(Ch3) Adsorbed on Si(100) Surfaces
Authors: Lubben D. , Motooka T. , Greene J.E. , Wendelken J.F. , Sundgren J.-E. , Salaneck W.R.
Published: March 2011

ArF (193 nm) and KrF (248 nm) laser-induced dissociation of Al2(CH3)6 (TMA) adsorbed on Si(100) surfaces have been investigated using x-ray photo-electron, ultraviolet photoelectron, and high-resolution electron energy loss spectroscopies (XPS, UPS, and HREELS). UPS and XPS valence spectra from the adlayer contained three broad peaks near 4.5, 7.5, and 14.5 eV below the Fermi level whose positions were in agreement, based upon molecular orbital calculations, with those expected for TMA dimers. Angle-resolved XPS measurements indicated a splitting in both the Al 2p and Si 2p levels which was interpreted as evidence for TMA dimer molecules being adsorbed with the long (i.e. Al-Al) axis perpendicular to the surface. The HREELS adlayer spectrum consisted of three clusters of peaks located near 86 meV (methyl rocking and Al-C stretch), 170 meV (methyl deformation), and 362 meV (C-H stretch). Changes in the XPS, UPS, and HREELS spectra were monitored as a function of ArF and KrF laser irradiation. No-changes were observed for KrF irradiation with intensities up to 200 mJ-cm . However, ArF laser irradiation resulted in changes in both the XPS and HREELS spectra which indicated TMA dissociation and the desorption of methyl groups. Nevertheless, even after 104 20 mJ-cm-2 ArF pulses most of the carbon-containing species remained. Higher intensities, up to 200 mJ-cm-2, resulted in the formation of compounds which were stable on the surface.
Low Temperature UV Photodeposition of Aluminum from TMA: Characterization and Control of Deposit Composition
Authors: Orlowski T.E. , Mantell D.A.
Published: March 2011

Laser processing conditions have been discovered which provide high-quality aluminum deposits from the photodecomposition of TMA (trimethylaluminum). Using an ArF excimer laser, AI can be deposited on Si and glass in well defined patterns at high rates (600 A/min) at low TMA pressure (≤ 30 mtorr) if substrate temperature is kept low (≤ 25C). Deposit composition is characterized by x-ray photoelectron spectroscopy (XPS) which shows that deposit carbon content depends upon laser pulse intensity varying nearly quadratically from < 1% at 8 mJ/cm2 to nearly 25% at 80 mJ/cm2. Mass spectroscopie analysis during laser processing identifies methane, ethylene and ethane as primary hydrocarbon photoproducts. Thermal desorption measurements indicate that many adlayers of adsorbed TMA leave the sample surface with only slight heating (35C) providing an explanation for observing higher growth rates at room temperature. Because of the high deposition rate and deposit quality observed, this low temperature process provides an attractive processing alternative for interconnect repair on Si and glass.
XPS Surface Composition Analysis During UV Laser Photodeposition of Al From Tiba on Si (100) Substrates: Direct Observation of the Prenucleation Regime
Authors: Mantell David A. , Orlowski T.E.
Published: March 2011

An in situ XPS study is made of the AI film growth from TIBA using an ArF pulsed laser on Si (100) substrates. It is found that the film is formed by the photochemical decomposition of the organometaliic on the surface. A metallic film is formed by island growth. These islands are covered with an organometaliic fragment layer of partially decomposed TIBA. The consequences of these observations toward understanding how laser processing can create prenucleation regions that catalyze film growth at temperatures below standard CVD temperatures are discussed.
Thermal Stability of Metal Films Deposited by Ionized Cluster Beams
Authors: Yamada I. , Usui H. , Harumoto H. , Takagi T.
Published: March 2011

Our previous experiments have shown that Al and Au films deposited on Si substrates by ionized cluster beams (ICB) exhibit high thermal stability and .long electromigration life time. To understand these characteristics, in-situ XPS measurements during ICB deposition of Au on Si(111) substrate have been made. The results show that at low coverages, the splitting between the two prominent structures in the Au-5d peaks in the valence band becomes closer to those of pure bulk gold when a film is deposited at high acceleration voltages. In contrast to this an appreciable change of the binding energy of the Si-2p state at low coverage and high acceleration voltage could not be observed. These results suggest that a high density layer is formed and any Au-Si interaction is suppressed at the initial stage of film deposition. This could be one of the reasons why ICB-deposited films exhibit high thermal stability.
Laser-Assisted Deposition of Fe and W: Photodecomposition of Fe(CO)5, and W(CO)6 on Si(111)-(7×7)
Authors: Swanson Jon R. , Friend C.M. , Chabal Y.J.
Published: March 2011

The laser-assisted chemical vapor deposition (LCVD) of Fe and W on Si(lll)-(7×7) was investigated under ultrahigh vacuum conditions at 120 K. Multiple internal reflection Fourier transform infrared and Auger electron spectroscopies and temperature programmed desorption and low energy electron diffraction were used to study the adsorption and decomposition of Fe(C0)5 and w(C0)6 on the surface. Neither of the molecules thermally reacts in temperature programmed desorption experiments. Reversible molecular desorption is exclusively observed. Decomposition of both molecules via electronic excitation was induced by ultraviolet, but not visible photons. This was shown by measuring the photodecomposition yield as a function of wavelength. Visible photolysis (λ=720 nm) had no observable effect on either molecule. No surface stable, partially decarbonylated, Fe(C0), x<5, fragments observable with infrared spectroscopy were produced by photolysis. Also, no new features were observed in temperature programmed desorption experiments and only iron was detected on the surface after photolysis. In contrast, initial results indicate that photolysis of W(C0)fi does produce surface stable, W(C0), x<6, fragments.
Soft Vacuum, Pulsed Electron Beam Processing of Polyimides
Authors: Krishnaswamy J. , Li L. , Collins G. J. , Hiraoka H. , Ann Caolo Mary
Published: March 2011

We report on the successful patterning of polyamic acid over wide areas using 28 kV pulsed electron beams produced in 30 mTorr air. The pattern degradation during the 350°C, 1/2 hr, imidizing thermal cure is prevented by pulsed, flood electron beam hardening of the developed polyamic acid patterns using the same soft vacuum, pulsed electron beam apparatus. It is also shown that a CW, low voltage, 1 to 3 kV electron beam sustained oxygen discharge can be used to completely strip the hardened, imidized material which is difficult to remove by wet methods. We also present, dose versus thickness remaining characteristics as a function of electron source to substrate distance and some examples of polyimide patterning.
Laser Ablation-Molecular Beam System. Reactions of Electrons or Ions From Metal Substrates With Organometallic, Metal Carbonyl and Organic Molecules
Authors: Toya Kenzo , Oka Tadashi , Kawasaki Masahiro , Sato Hiroyasu
Published: March 2011

Laser light (the second or third harmonics from an Nd:YAG laser) was focussed on the metal substrate in vacuum. A pulsed molecular beam of an organometallic compound, a metal carbonyl, or an organic molecule was introduced in the entrance region (the region in front of the ion-lens assembly) of a quadrupole mass filter which was located near the metal substrate. The reaction of the molecules in the beam with either the electrons or ions from the metal substrate was studied by monitoring the product ions by the mass spectrometer.
Laser Enhanced Selective Epitaxy of ιii-V Compounds
Authors: Karam N.H. , Liu H. , Yoshida I. , Katsuyama T. , Bedair S.M. , El-Masry N. , Jaing B. , Salih A.S.M. , Rozgonyi G.
Published: March 2011

Selective epitaxial growth of III-V compounds based on GaAs has been achieved using Ar+ ion laser assisted chemical vapor deposition (LCVD) on GaAs substrates. The growth rate, at carefully selected growth conditions, can be controlled to a few Å/s at bias temperatures as low as 250°C by conventional LCVD multi-scan technique. Typical Gaussian thickness profiles are achieved by this growth technique. On the other hand, flat top thickness profiles are achieved with direct writing of GaAs mono-layers by laser assisted atomic layer epitaxy (LALE). X-ray topography is demonstrated as a powerful tool for characterizing the grown films and photoluminescence shows that the quality of the grown films are comparable with those grown by conventional MOCVD or ALE.
Photodissociation Dynamics of Alkyltellurides
Authors: Brewer P.D. , Jensen J.E. , Olson G.L. , Tutt L.W. , Zinck J.J.
Published: March 2011

The UV photodissociations of dimethyltelluride (CH3)2Te and diethyltelluride (C2Hs)2Te have been investigated by state-selective detection. Nascent populations of Te(5p Pjw) atoms produced by the photodissociation process were monitored using laser-induced fluorescence following excimer laser (248 nm and 193 nm) photolysis. Experimental results for both molecules indicate that the photolysis at 248 nm produces Te atoms via a single photon process and that the liberated Te atoms populate only the 5p3P2 state. The photolysis of diethyltelluride at 193 nm has also been found to be a single photon process producing Te atoms distributed over the 3P2, 3P1, and Pø states in a ratio of 13:2:1, respectively.
Low-Coverage Laser Desorption of Ions on Chlorinated Copper Surfaces
Authors: Chen L. , Liberman V. , O'Neill J.A. , Osgood R.M.
Published: March 2011

Experiments were performed to investigate the pulsed excimer laser etching of a chlorinated copper substrate. Time-of-flight mass spectrometric techniques were employed to characterize the mass and velocity distributions of both neutral and ionic species that desorb at laser fluences less than that required to melt bulk Cu or CuCl substrates. The presence of positively charged ions in this work is examined in terms of both photon and electron mediated desorption mechanisms.
Limiting Steps at Low Temperature in Direct Writing of Al on Si From Tma
Authors: Flicstein J. , Bouree J.E. , Bresse J.F. , Pougnet A.M.
Published: March 2011

The rates of aluminum line growth, assisted by photolysis, in the normal direction to the Si (100) substrate, indicate that, in a trimethyl-aluminum + hydrogen mixture, only the change in the TMA flux and the UV laser power can play a determinant role. Possible explanation is based on the generated methyl radical “blocking” action leading to a self-limiting deposition rate, as opposed to the enhancement of methyl desorption by hydrogenation to methane. It is shown that dilution by hydrogen decreases the carbon contamination in aluminum line.
Compact Laser Source for Metal Deposition
Authors: Arjavalingam G. , Oprysko M.M. , Hurst J.E.
Published: March 2011

For the past few years, there has been considerable interest in using lasers for the directed deposition of metal [1,2,3,4]. Part of this interest is driven by technological applications in microelectronics. In particular, this includes the rapid interconnection of gate arrays [5] and the repair of defects in photomasks [6]. The techniques used for the laser patterning of metal include Laser Chemical Vapor Deposition (LCVD) [7], and the decomposition of spin-coated organometallic inks [8]. In the first process, LCVD, a laser with a power of several hundred milliwatts or more is used to irradiate a substrate in the presence of an organometallic vapor. The substrate is chosen so that it absorbs the the incident laser radiation while, in general, the organometallic vapor is transparent at the laser wavelength. The absorption of the laser energy by the substrate results in a temperature rise which depends on the thermal properties of the substrate. If the temperature rise is sufficient, organometallic molecules impinging on the irradiated area decompose. Non-volatile components (such as metal fragments) remain on the surface and form a deposit. In the second process, decomposition of organometallic films, a substrate which was previously spin coated with an organometallic ink is irradiated wherever metal patterns are desired. The ink decomposes in these areas leaving a film of metal. The unirradiated areas of the ink are then washed away with a suitable solvent. Such processes have been extensively studied and developed using primarily argon, krypton, and CO2lasers [1,2,3,4]. In general these lasers are large, expensive, require maintenance, and raise reliability concerns. These characteristics add to the challenge of introducing laser deposition processes into the manufacturing environment.
ZNSE/III–V Heterostructures Grown in a Multichamber MBE System
Authors: Tamargo M. C. , de Miguel J. L. , Hwang D. M. , Skromme B. J. , Meynadier M. H. , Nahory R. E. , Farrell H. H.
Published: March 2011

We have grown ZnSe epitaxial layers on bulk GaAs substrates and on GaAs epitaxial layers, with both As-rich and Ga-rich surface terminations. We have also grown ZnSe on AlAs epitaxial surfaces with different As to Al ratios. In all cases, abrupt, layer-by-layer growth is observed on the As-rich surfaces, while 3-dimensional nucleation is observed on the group III-rich surfaces. GaAs was also grown on ZnSe layers. In this case, microtwins form at the interface whose density diminishes as the layer is made thicker. A growth model is proposed consistent with these results which requires over-all electronic balance at the interface.
Asymmetric Cracking in Znse/ZnSxSel−x Superlattices Grown by Molecular Bean Epitaxy
Authors: Dalby Richard J. , Petruzzello John
Published: March 2011

Optical and transmission electron microscopy have been used to study cracks appearing in ZnSe/ZnSxSe1−x (x ∼ 0.38) superlattices grown by Molecular Beam Epitaxy. It Is shown that when a fracture occurs it is confined, in most cases, to the superlattice and propagates along <011> cleavage directions in these <001> oriented epilayers. Cracks were not observed in all superlattices and their onset is discussed in relation to sulfur concentration, overall superlattice height, individual superlattice layer thicknesses, and stress, tensile or compressive, due to lattice mismatch and thermal expansion differences between buffer layer and superlattice. It was found that by adjusting the controllable parameters, cracks in the superlattices could be eliminated. Orientation and density of these features have been related to asynnmetric cracking associated with the zincblende structure of these II-VI materials. Experimental results are shown to be in agreement with theoretical predictions of critical heights for the onset of cracking.
Interface Recombination Velocities in Layered GaAs and AlGaAs/GaAs Structures Grown by OMVPE
Authors: Bothra S. , Venkatasubramanian R. , Ghandhi S.K. , Borrego J.M.
Published: March 2011

The interface recombination velocity at n+ GaAs/n GaAs and n+ Al15 Ga85 As/n GaAs are reported for various dopings. It is seen that with an n+ GaAs cap layer it is possible to reduce the interface recombination velocity to ∼ 4.4 × 103 cm/s. This can be further reduced by employing an AlGaAs cap, due to the increased barrier caused by the valence band discontinuity.
Interfacial Reactions Between Ni and GaAs
Authors: Lin J. C. , Zheng X. -Y. , Hsieh K. -C. , Chang Y. A.
Published: March 2011

Interfacial reactions between Ni and GaAs have been studied using bulk diffusion couples of Ni(∼0.5mm thick)/GaAs and thin-film Ni (∼40nm) on GaAs (100) in addition to phase diagram determination at 600° C. On the basis of the phase diagram and the bulk diffusion couples, the ternary phase which forms first in the thin-film couples is Ni3 GaAs. Thinfilm studies show that the epitaxial growth of equilibrium contact phases, i.e., NiAs and β-GaNi, on a GaAs (100) substrate is possible.
Misoriented Epitaxial Growth of (111)CoSi 2 on Offset (111)Si Substrates
Authors: Bai Gang , Jamieson David N. , Nicolet Marc-A. , Vreeland Thad
Published: March 2011

Single crystal epitaxial films of CoSi2 were grown by MBE on various (111)Si single crystal substrates, whose surfaces were purposely tilted towards the < 110>>g, direction by small angles ϕg,†, 0°, ≤ϕg, ≤, 4° measured between the surface normal and the < 111>>g, direction of Si. The actual offset angle, .ϕ8,, was determined by back Laue reflection method. The average perpendicular strain of the CoSi2 epilayer, ε┵, and the < 111 >f orientation of the epitaxial CoSi2 film were determined by double crystal diffractometry. We find that the misorientation angle, a, measured between the Si < 111>g, and CoSi2 < 111>f directions, increases linearly with the offset angle, ϕg, up to ϕg, = 4°. A simple geometrical model is developed which predicts that α = ε┵ × tan ϕg,. The model agrees quantitatively with the experimental data. The equivalent strain energy associated with the misorientation is approximated by that of a low angle tilt boundary. The misorientation angle α of the equilibrium state, determined by minimizing the total strain energy of the epitaxial film, is nonzero in general.
Epitaxial Growth of Thick Ag/Si(111) Films
Authors: Park K.-H. , Jin H.-S. , Luo L. , Gibson W.M. , Wang G.-C. , Lu T.-M.
Published: March 2011

600∼4000Å thick Ag films grown on 3∼4· misoriented Si(111) substrates by molecular beam epitaxy (MBE) technique have been studied by using x-ray pole-figure analysis and MeV He+ Rutherford Backscattering Spectrometry (RBS)/channeling technique. X-ray pole-figure measurements revealed that despite the large lattice mismatch (∼25%) between Ag and Si, Ag films with epitaxial relationship Ag(111)//Si(111):Ag[011]//Si[011] were grown with a small quantity (15∼20%) of twin structure. The <111> axial channeling minimum yield (Xmin) is reduced at the Ag surface as the Ag film thickness increases. These films were thermally stable up to 500°C annealing but the twinning disappeared after annealing
RBS/Chainneling and Ten Analysis of Heteroepitaxial Ge Films on GaAs Crown by Remote Plasma Enhanced Chemical Vapor Deposition
Authors: Parikh N.R. , Hattangady F V , Posthill J.B. , King M.L. , Rudder R.A. , Vitkavage D.J. , Markunas R.J. , Chu W.K.
Published: March 2011

We have deposited thin Ge films on GaAs(111) crystals over a temperature range of 250-400° C by Remote Plasma Enhanced Chemical Vapor Deposition (RPECVD). Rutherford Backscattering (RBS)/channelinf analysis of these heteroepitaxial films were carried out using 2.07 MeV He ions channeled along the <111> axis. RBS/channeling analysis showed that the best Ce films were grown at a substrate temperature of 300° C. The minimum yield for <111> channeling on films deposited at 300° C was 0.08, slightly greater than that of the GaAs crystal. Films grown at temperatures below 300° C showed poor epitaxy. No channeling was observed for the film grown at 250° C. Films grown at substrate temperatures above 350° C showed high dechanneling near the interface and poor epitaxy indicating films are highly defective. The RBS/channeling results are correlated with microstructural characterization using transmission electron microscopy of these films.
X-Ray Diffraction and Sims Studies of Mbe Grown Doping Superlattices in Silicon
Authors: Brown G T , Barnett S J , Blackmore G W , Courtney S J , Houghton D C
Published: March 2011

Si-Si(B) doping superlattices (pipi structures) were grown by MBE and studied using double crystal x-ray diffraction and SIMS. Detailed analysis of the complex x-ray rocking curves required comparison of experimental data with theoretically simulated data. It is demonstrated that this technique is sensitive to irregularities in the dopant composition, dopant distribution and superlattice period. The B concentration profile is shown to spread well into the intrinsic layers and the extent and magnitude of the dopant distribution has been quantified. A comparison of this data with SIMS showed good agreement for the distribution of B and reasonable agreement for the peak values of B concentration.
Oxidation of Strained Si-Ge Layers Grown by MBE
Authors: Patton G.L. , Iyer S.S. , Delage S.L. , Ganin E. , Mcintosh R.C.
Published: March 2011

The oxidation of strained SiGe alloy layers grown by Molecular Beam Epitaxy (MBE) was studied. An initial fast growth regime was identified for 800°C steam oxidations, where the growth rate is 2.5 times that of silicon. The oxides formed on SiGe were found to be essentially Ge-free: Ge present in the material is rejected by the oxide, resulting in the formation of a Ge-rich epitaxial layer at the oxide/substrate interface.
Pulsed Laser Crystallization of GexSi1−x Alloy Films on Si(100) Substrates
Authors: Abelson John R. , Weiner Kurt H. , Kim Ki-Bum , Sigmon Thomas W.
Published: March 2011

We demonstrate the fabrication of high quality GexSi1−x heteroepitaxial alloy layers on Si(100) substrates by pulsed laser melting of a-Ge/Si(100) layered structures. First, 50–200Å of germanium are evaporated onto a chemically cleaned silicon wafer. Next, an excimer laser pulse is used to melt the sample surface to a depth of 200–2500Å. Finally, the melt solidifies in 20–100ns producing a heteroepitaxial alloy layer. By varying the thickness of the evaporated Ge film and the laser energy, alloys of 500–1500Å thickness and Ge fraction x=3–20% are obtained. The crystallinity of the layer and interface are found to be excellent as evaluated by Rutherford Backscattering Spectrometry (RBS), ion channeling, and high resolution cross sectional TEM. This technique for producing GexSi1−x alloy layers is insensitive to minor levels of contamination because the original Ge/Si interface is melted through during the laser processing
Photoluminescence of MBE and MOCVD ZnTe Films on GaAs
Authors: Wilson B. A. , Bonner Carl E. , Feldman R. D. , Austin R. F. , Kisker D. W. , Krajewski J. J. , Bridenbaugh P. M.
Published: March 2011

We present low-temperature photoluminescence (PL) spectra of MBE and MOCVD ZnTe layers deposited on (100) GaAs substrates under different growth conditions. Strong bands associated with Zn vacancies are observed in the MBE materials, while the MOCVD spectra are dominated by sharp impurity-related lines. Stress levels less than 0.1 kbar are determined for both the MBE and MOCVD layers. A study of the effects of the Zn:Te ratio in the MBE growth chamber reveals an optimal value of −2.2 for a growth temperature of 325°C.
Epitaxial Growth of CdTe on (100) GaAs/Si and (111) GaAs/Si Substrates Using Molecular Beam Epitaxy and Metalorganic Chemical Vapor Deposition
Authors: Radhakrishnan G. , Nouhi A. , Katz J.
Published: March 2011

CdTe is a very important semiconductor with versatile applications extending from solar energy conversion to optoelectronics. In addition, both the close lattice match between CdTe and HgCdTe and the immunity of CdTe to autodoping of the HgCdTe make CdTe the substrate of choice for the growth of HgCdTe. However, CdTe is extremely difficult to grow and the nonavailability of good quality, large area, inexpensive, single crystal CdTe has slowed the development of HgCdTe detectors. Infrared device processing requires large areas of single crystal material and the problems associated with CdTe have called for alternative substrates for growing HgCdTe.
Layered Structures Composed of Si, Ge, GaAs, and Fluorides
Authors: Ishiwara H. , Asano T. , Tsutsui K. , Lee H. C. , Furukawa S.
Published: March 2011

Recent progress in the heteroepitaxial growth of layered structures of Si, Ge, GaAs, and alkaline earth fluorides is reviewed. Effectiveness of the predeposition technique, in which a thin Si layer is deposited on the CaF2 surface at room temperature prior to the growth of a thick Si film at 800°C, is shown for the growth of Si films on CaF2/Si structures. In case of the overgrowth of Ge and GaAs films on (111) substrates, modification of the fluoride surface by electron beam exposure is effective to increase the wettability between fluoride and semiconductor films and to improve the crystallinity and surface morphology of the films. Finally, antiphase disorder in the GaAs(l00) films grown on fluorides is experimentally studied and the generation mechanisms are discussed.
Buried Silicide Synthesis and Strain in Cobalt-Implanted Silicon
Authors: Barbour J.C. , Picraux S.T. , Doyle B.L.
Published: March 2011

Silicon (001) substrates were implaynted with 350 keV Co at room temperature and 450°C with fluence of from l×l017 Co/cm2 to 6×1017 Co/cm . All samples were annealed at 1000°C in order to form the CoSi2 phase Concentration profiles were determined with Rutherford backscattering spectrometry (RBS), and the associated strain profiles were analyzed with double-crystal X-ray rocking curve measurements. Ion channeling was also used to characterize the silicide formation and crystal quality. An implantation of 6×1017 Co/cm2 at 450°C forms a single-crystal CoSi2 layer while lower fluences do not. A continuous, buried CoSi2 single-crystal layer is formed for the 3×1017 Co/cm2 sample implanted at 450°C and annealed at 1000°C. The continous CoSi2 layer is thicker than the critical layer thickness for a fully coherent film, and therefore the layer partially relaxes. A relaxation of 50% of the fully coherent value is observed for this buried silicide system.
Nucleation and Growth of Cosi2 on (001) and (111) Si
Authors: Bulle-Lieuwma C.W.T. , Van Ommen A.H. , Hornstra J.
Published: March 2011

Nucleation and growth of epitaxial CoSi2 on Si by the thermal reaction of vapour deposited Co on (001) and (111) Si have been studied by transmission electron microscopy (TEM). On (001)-Si the layer consists of CoSi2 grains. Apart from an aligned (a)-orientation, CoSi2 occurs in a number of orientations, including a (110) preferential (b)-orientation. On (111) Si, single-crystalline layers are obtained, predominantly in the B-type orientation, which is rotated through 180° relative to the aligned (111)-orientation (A-type). The interfacial defect structure consists of misfit dislocations of edge-type with Burgers vector b=a/6<112>, running in <110> directions. The observations for both (001) and (111) Si are related to geometrical lattice match between CoSi2 and Si. In addition to the experimental results, a computer program has been made which calculates the matching between various orientations of CoSi2 and Si. The nucleation of B-type CoSi2 for (111) Si and the different oriented grains for (001) Si are discussed in terms of a nucleation mechanism at steps at the interface in combination with a relatively large mismatch.
The Effect of Formation Conditions on the Structural and Electrical Properties of Ultrathin Cobalt Silicide Films
Authors: Phillips Julia M. , Batstone J. L. , Hensel J. C. , Cerullo M. , Unterwald F. C.
Published: March 2011

We have studied the dependence of the structural and electrical properties of ultrathin cobalt silicide films on the annealing temperature and deposited Co thickness.

We recently reported that coherent, electrically continuous films of CoSi2 could be grown on Si(111) with thicknesses as small as 1 nm.1 The thinnest of these films had a high density of pinholes which covered about 20% of the area of the substrate. The resistivity of the films increased dramatically with decreasing thickness in a manner which was qualitatively consistent with quantum size effects. In order to investigate the dependence of both the pinhole density and the resistivity of ultrathin CoSi2 films on Si(111), we have deposited different thicknesses of Co onto near room temperature (<100°C) Si(111) substrates and have annealed the samples at different temperatures in order to study the effect of silicide formation conditions on the structural and electrical properties of the resulting films.

Co layers were deposited onto Si(111) wafers in a molecular beam epitaxy apparatus as described previously.1 In our earlier work, CoSi2 was formed by heating the sample to ∼600°C for a few seconds after Co deposition. Because higher temperature anneals are known to lead to pinhole formation in thicker films,2 annealing temperatures in the present experiments were constrained to be 600° or less. The reaction time was on the order of 5 minutes. The layers were examined using plan-view transmission electron microscopy (TEM) in order to avoid beam heating and ion beam mixing effects which might cause artefacts in cross-section TEM observation.

The results of our experiments are summarized in Figure 1. The figure indicates the silicide phases found in a film as a function of deposited Co thickness and annealing temperature. The numbers in each square correspond to the residual resistivity, ρo, measured for each film. Perhaps the most striking finding of this study is the abrupt change in the structure of the films between 0.7 and 1.4 nm of deposited Co. For all temperatures investigated (including near room temperature), films formed by depositing less than 1 nm of Co form CoSi2 immediately upon deposition. (For films approaching this thickness, there is also a small amount of Co2Si which persists at all temperatures
Molecular Beam Epitaxial Growth Over Multiple Wafers Using an Indium-Free Mounting Technique
Authors: Igarashi T. , Saito J. , Okamoto Y. , Ishikawa T. , Kondo K.
Published: March 2011

An indium-free substrate mounting technique was developed for a 190-mm diameter substrate holder on which three 3-inch GaAs substrates are mounted. Reduction of the heat conduction between the substrates and the holder kept the temperature variation in the substrate within ±5° C. Highly uniform epitaxial layers were grown with low residual impurity concentrations using this technique. The variations in layer thickness and carrier concentration of Si-doped GaAs and AlGaAs epitaxial layers were within ±1% over the substrate holder. High mobility of a two-dimensional electron gas in a selectively doped GaAs/N-AlGaAs heterostructure was obtained uniformly over three 3-inch wafers. Since the holder was designed to hold the wafers without stress, no stress-related degradation of the surface morphology was observed.
Observation of GaAs/Si Interface by Tem: Effect of Annealing on the Structure
Authors: Heral H. , Rocher A. , Charasse M. N. , Georgakilas A. , Chazelas J. , Hirtz J. P. , Blancka H. , Siejka J.
Published: March 2011

We present in this paper the effect of heat treatments applied to a 400 nm GaAs layer grown by MBE on a (001) Silicon substrate. These heat treatments have been applied during or after the growth of the GaAs, in order to improve the crystalline quality of the layer. RBS and TEM observations have been performed to study the improvement of the crystalline quality of the GaAs layer. Specimens, prepared by cross-section technique along both (110) and (170) planes and plane view, have been studied by TEM. Observations of cross-section by HREM show an interface roughness of about 1.5 nm before and after heat treatments. A roughness, observed also by RHEED, appears in the first stage of growth. Although the density of threading dislocations decreases after heat treatments.
The Growth of AIGaAs/GaAs Heterostructures By Atomic Layer Epitaxy
Authors: Denbaars S. P. , Hariz A. , Beyler C. , Maa B. Y. , Chen Q. , Dapkus P. D.
Published: March 2011

The kinetics of atomic layer epitaxy (ALE) of GaAs utilizing trimethylgallium and arsine are described. The results show that saturated monolayer growth can be achieved-in the temperature range 445°C -485°C and that high quality materials can be grown.. Hybrid A1GaAs/GaAs heterostructures have been grown utilizing ALE for the active regions and conventional metalorganic chemical vapor deposition (MOCVD) for the confining regions that yield high quality quantum wells and low threshold quantum well lasers.
TEM and TED Studies of Ordering in GaInP
Authors: Coral J. P. , Al-Jassim M. M. , Olson J. N. , Kibbler A.
Published: March 2011

Transmission electron microscopy (TEM) and transmission electron diffraction (TED) studies have shown the presence of long range CuPt-type cationic ordering 4n GaInP grown by MOCVD on (001) GaAs. Domains regions (on order of 104nm2) exhibit a double periodicity along the [111] and [110] directions.
Transmission Electron Microscope Study of An Ordered Structure in GaAs0.5 Sb0.5 Grown By Molecular Beam Epitaxy
Authors: Ihm Y. E. , Otsuka N. , Hirotsu Y. , Klem J. , Morkoc H.
Published: March 2011

The ordered structure in a (100) GaAs0.5 Sb0.5 epilayer grown by molecular beam epitaxy has been studied by transmission electron microscopy. Domain structures are observed in dark field images of superstructure reflections. The ordered structure is derived by the analysis of diffraction patterns taken from single domains. The ordered structure is described as an alternate stacking of As and Sb planes in the <111> direction of the FCC sublattice. The alternate stacking of As and Sb plane is directly observed by high resolution electron microscopy.
Pre-Cracking and Plasma Enhanced Metalorganic Chemical Vapor Deposition Processes for Epitaxial Hg1−xCdxTe and HgTe-CdTe Superlattice Growth
Authors: Lu P.-Y. , Williams L. M. , Wang C.-H. , Chu S. N. G. , Ross M. H.
Published: March 2011

Two low temperature metalorganic chemical vapor deposition growth techniques, the pre-cracking method and the plasma enhanced method, will be discussed. The pre-cracking technique enables one to grow high quality epitaxial Hg1−xCdxTe on CdTe or CdZnTe substrates at temperatures around 200–250°C. HgTe-CdTe superlattices with sharp interfaces have also been fabricated. Furthermore, for the first time, we have demonstrated that ternary Hg1−xCdTe compounds and HgTe-CdTe superlattices can be successfully grown by the plasma enhanced process at temperatures as low as 135 to 150°C. Material properties such as surface morphology, infrared transmission, Hall mobility, and interface sharpness will be presented.
Glancing Angle EXAFS Studies of Tungsten-Carbon Multilayers
Authors: Lamble G. M. , Heald S. M. , Sayers D. E. , Ziegler D E.
Published: March 2011

Results are presented from glancing angle EXAFS studies of three tungsten-carbon multilayer systems, of different W/C thickness ratios, by monitoring the fine structure above the tungsten L3-edge. The purpose of the investigations was to determine the structural changes occurring in the multilayer as a result of moderate annealing. Surprisingly, dramatic changes are observed in the structural environment of the W atoms as a result of heating to temperatures as low as 350°C for 3 hours. It is found that, when the W layer is sufficiently thick, and the W/C layer thickness favorable, W2C is preferentially formed and crystallization is extensive.

The experiment demonstrates the suitablility of the EXAFS technique for the study of multilayer systems since, 1) contribution to the signal from the interface is significant and 2) the phenomenon is not dependent on the existence of long range order.
X-Ray Scattering (Modeling and Experiment) of InxGa1-xAs/GaAs Multiple Quantum Wells
Authors: Jeong Jichai , Lee J. C. , Shahid M. A. , Schlesinger T. E. , Milnes A. G.
Published: March 2011

X-ray diffraction, transmission electron microscopy (TEM), and photoluminescence measurements have been made on strained InxGa1-xAs/GaAs quantum well structures. The well widths measured from TEM are 187, 115 and 69 Å for an interrupted growth, and 218, 126, 60 Å for a non-interrupted growth. In the measured x-ray diffraction patterns, the Pendellosung fringes due to GaAs barriers are modulated by a broad weak peak mostly coming from the thickest InxGa1-xAs well layer and is fairly symmetric for the noninterrupted sample. For the interrupted quantum well, the x-ray diffraction pattern is less symmetric, since there is further modulation by another broader and weaker peak. This results show that the In content in the InxGa1-xAs well layers are not well controlled for the interrupted quantum well. Using actual thickness measured from TEM, x-ray diffraction patterns are calculated and good agreement is obtained between the measured and the calculated x-ray diffraction patterns. The three strained InxGa1-xAs/Gaks quantum wells grown without interruption produce high intensity and narrow full-width at half-maximum (FWHIM) of 2.9 meV of the photoluminescence peak. The photoluminescence peaks for the interrupted quantum well are relatively broad and asymmetric, and have lower intensities, indicating that better quality InxGa1-xAs/GaAs quantum wells can be grown without interruption.
Fe-W Supernirrors for Polarizing Neutrons
Authors: Majkrzak C. F. , Neumann D. A. , Copley J. R. D. , Dinardo R. P.
Published: March 2011

Thin film bilayers of ferromagnetic Fe and nonmagnetic W have been deposited by sputtering on flat glass substrates according to a sequence of gradually varying bilayer thicknesses which in effect extends the critical angle for external mirror reflection for neutrons of one spin state when the Fe is magnetized in the plane of the film. The measured reflectivity of this Fe-W multilayer system is compared with that of other supermirror polarizers consisting of different materials and layer sequences.
Techniques for Characterising Artificial Layer Structures using Transmission Electron Microscopy
Authors: Stobbs W. M.
Published: March 2011

T.E.M. methods are described for the quantitative characterisation of the compositional and structural changes at interfaces and in homo- and hetero-phase multilayer structures. Many of the newer approaches described including the Fresnel and Centre Stop Dark Field Imaging Methods were developed specifically for such characterisations. The range of applications of each of the techniques is assessed as is the importance of delineating the limiting effects of inelastic and inelastic/elastic multiple scattering.
Evidence for Instability in Pb1-x EuxTe Alloys
Authors: Salamanca-Young L. , Wuttig M. , Partin D. L. , Heremans J.
Published: March 2011

We have used transmission electron microscopy to study the structure of Pb1-xEuxTe alloys grown by molecular beam epitaxy. We have observed ordered solid solutions of the Pb1-x EuxTe alloys as well as spinodal decomposition for 0.35≤x<0.75. The spinodal decomposition corresponds to a modulation of both the composition and the lattice spacing of the Pb1-x EuxTe alloy. These modulated structures have periodicities of ∼18Å along the <111> and <110> directions and indicate that the solid solution of Pb1-x Eux Te is unstable in this range of compositions.
Interface Structure and Solid State Reactions of Fe/Zr Multilayers
Authors: Clemens Bruce M. , Williamson D. L.
Published: March 2011

Iron zirconium multilayer films were prepared by electron beam evaporation and by sputter deposition. Layer thicknesses were varied from 50 monolayers of each constituent down to 2 monolayers. Conversion electron Mössbauer spectroscopy, x-ray diffraction, and Auger spectroscopy have been used to characterize multilayers in the as-deposited and annealed state. Amorphous phase formation occurs during thermal anneals, and samples with layer thicknesses of 5 monolayers or less of each constituent are amorphous as deposited. Amorphous interfaces are observed in all samples, with this interface region being larger in the electron beam evaporated samples than in the sputter deposited samples.
Epitaxial Growth of Rare Earths on Rare Earth Fluorides and Rare Earth Fluorides on Rare Earths: Two New Epitaxial Systems Accessed by MBE
Authors: Farrow R. F. C. , Parkin S. S. P. , Lang M. , Roche K. P.
Published: March 2011

We report two new epitaxial systems, prepared by MBE: basal plane epitaxy of the rare earth metal Dy onto LaF3 films and vice versa. SQUID magnetometry studies indicate that buried epitaxial Dy films, of ∼300Å thick, order ferromagnetically at similar temperatures to bulk Dy crystals.These epitaxial systems are one member of a new family of epitaxial systems of basal plane epitaxy of rare earth metals on rare earth fluorides and vice versa. Such systems may be used to probe the effects of strain and dimensionality on magnetic ordering in rare earth metal films and multilayers.
A Solid State Amorphisation Reaction in Ti-Si Diffusion Couples: The Phase Field
Authors: Raaijmakers Ivo J. M. M. , Oosting Piet H. , Reader Alec H.
Published: March 2011

The reactions in sputter deposited Si-Ti-Si diffusion couples were investigated with X-ray diffraction, Auger electron spectroscopy and cross-section transmission electron microscopy. Anneals at a temperature of 400°C resulted in the growth of an amorphous phase at the Si-Ti interfaces. Crystalline silicides were only found after an anneal at temperatures of 500°C or higher.

It was demonstrated that an amorphous layer of approximately 8 nm thickness sustained a concentration gradient from about 73% Si at the Si side to about 28% Si at the Ti side of the diffusion couple. The measured width of the phase field agreed with the width predicted from a calculated free energy versus composition diagram. Actually the observed phase field was found to be so wide, that it contains the stoichiometry of all equilibrium silicides. The consequences of our results for the explanation of silicide first phase nucleation were discussed.
Light Scattering Analysis of Strained-Layer Superlattices
Authors: Schwartz G. P. , Gualtieri G. J. , Sunder W. A.
Published: March 2011

Raman scattering has been used to examine strained-layer GaSb/AlSb superlattices for a variety of growth imperfections. Analysis of zone-folded acoustic phonon spectra permit a determination of the superlattice period, the individual layer widths, some estimate of the interfacial widths, and evidence for variations in layer thicknesses.
Combined Microstructure X-Ray Optics; Multilayer Diffraction Gratings
Authors: Barbee Troy W.
Published: March 2011

Multilayers are man-made microstructures engineered to vary in depth that are now of sufficient quality to be used as x-ray, soft x-ray and extreme ultraviolet optics. Gratings are in-plane man-made microstructures which have been used as optic elements for most of this century. Joining of these two optical elements to form combined microstructure optics has the potential for greatly enhancing both the resolution and the throughput attainable in these spectral ranges. Experimental results for multilayer gratings are presented and discussed. It will be demonstrated that multilayer diffraction gratings act as x-ray prisms and are high efficiency dispersion elements.
Magnetic Superlattices
Authors: Schuller Ivan K.
Published: March 2011

Magnetic superlattices serve as model systems for the study of thin film, interfacial, proximity, coupling and superlattice phenomena. Due to these phenomena, the physical properties of magnetic superlattices can be tuned in a reproducible fashion by proper control of the preparation process.

Magnetic measurements in conjunction with detailed structural characterization provide a fruitful area of research, especially in understanding basic phenomena in magnetism. We describe here briefly a few experimental examples from our work which illustrate the possibilities magnetic superlattices offer for the study of basic phenomena in magnetism.
On the Existence of Multiple Equilibrium States in Strained-Layer Superlattices
Authors: Johnson William C.
Published: March 2011

Using recent results from the thermodynamics of stressed solids, two-phase coexistence in a simple binary strained-layer superlattice is examined. We show that for a given temperature and overall composition of the superlattice, there can exist more than one linearly stable, equilibrium thermodynamic state. That is, there may exist several combinations of relative thickness of the phases and corresponding phase compositions that minimize the free energy of the system. The equilibrium state observed experimentally can, therefore, be influenced by the processing path.
Spectroscopy of Impurities and Complex Defects in Silicon in Zlectric and Microwave Fields
Authors: Godlewski M. , Weman H. , Wang F. P. , Monemar B. , Chen W. M. , Zhao Q. X.
Published: March 2011

We report a detailed study of the photoluminescence (PL) intensity of bound excitons (BE:s) in silicon, related to shallow impurities and deep complex defects, as a function of DC and high frequency AC (9GHz) electric fields. Two experimental approaches are presented. The first involves a simultaneous recording of PL and photocurrent under pulsed DC excitation. The second utilizes the optically detected cyclotron resonance (ODCR) technique, which allows detection of cyclotron resonance (CR) via the resonancetransition- induced changes of BE PL intensity. The mechanism responsible for the PL changes is shown to be the impact ionization of BE:s by hot free carriers. Effects of sample inhomogeneities in these experiments are also discussed.
Dislocation Dynamics During the Czochralski Growth of Silicon
Authors: Tsai C. T. , Dillon O. W. , Angelis R. J. De
Published: March 2011

The thermal stresses induced by temperature variations that exist during steady-state Czochralski growth produce plastic deformations in the crystal by dislocation motion and generation. The temperature variations in the crystal are calculated numerically by the finite element method (FEM). Employing the Haasen-Sumino viscoplastic response function for silicon and the calculated temperature profile, the thermal stresses, the dislocation densities, and the residual stresses in the crystal are also calculated. Only low dislocation densities are of interest and hence the associated viscoplastic deformations are found to be small. The assumption is made that there is a very low dislocation density along the solid-melt interface. The Haasen-Sumino material model is modified to include a back-stress to account for the locking effects due to the impurity concentration in the crystal. This analysis provides guidance for growing large diameter crystal of materials with known constitutive relations which have a low dislocation density and low thermal stresses.
Influence of Oxygen and Boron on Defect Production in Irradiated Silicon
Authors: Drevinsky P. J. , Caefer C. E. , Tobin S. P. , Mikkelsen J. C. , Kimerling L. C.
Published: March 2011

Introduction rates of dominant defects have been determined for electron-irradiated, p-type silicon as a function of oxygen and boron concentration. Samples included those with oxygen content ranging from 8 × 1015 to 7 × 1017 cm−3. Initial results are described for samples with measured carbon content varying from 2 × 1015 to 6 × 1016 cm−3. Competing defect reactions involving the interstitial defects, Bi and Ci, and oxygen, boron, and carbon are observed. The identities of an electron trap (Bi-Oi) and a hole trap (Bi-Bs) have been clarified.