bluuebunny/crossref_metadata_2025_split huggingface dataset:
Boron Diffusion in Polycrystalline Silicon
Authors: Ghannam Moustafa Y. , Dutton Robert W. , Novak Steven W. 
Published: March 2011

ABSTRACTThe diffusion of boron in ion implanted LPCVD polycrystalline silicon is shown to be dominated by grain boundary diffusion at low and moderate concentrations. The diffusion coefficient is 2 to 3 orders of magnitude larger than its value in crystalline silicon. In preannealed polysilicon, the boron diffusion coefficient is found to be 30% smaller than in polysilicon annealed after implantation. This reflects the effect of the grain size in the diffusion coefficient since preannealed polysilicon has larger grains and smaller density of grain boundaries per unit area.
Confinement and Fluorescence of Aromatic Molecules in Microporous Amorphous Superlattices
Authors: Roxlo C. B. , Mitra P. , Deckman H. W. , Abeles B. , Wong P. P. 
Published: March 2011

ABSTRACTWe have investigated molecular confinement in materials with nanometer sized pores, fabricated from amorphous superlattices of a-Si:H/a-SiOx:H, using 1,10-bis(1-pyrenyl)decane as a fluorescent probe. In large (46 Å) pores, the emission and excitation spectra and their time dependence are similar to microcrystalline material, showing the presence of molecules aggregated in the ground state. This dimer emission decreases sharply as the pore size is decreased, showing that the minimum size for aggregate formation is about 20 Å.
High Field Microscopy Studies of Gallium Arsenide-Metal Interface
Authors: Patel Chand 
Published: March 2011

ABSTRACTThe Field Emission Microscope has been extensively used in the study of metal and semiconductor surfaces. The process of Field Emission is, itself, of great interest and a considerable amount of both theoretical and experimental work has been carried out in this field. The Field Emission Microscope also yields useful information of a more practical nature, such as the nature of bulk and surface impurity, diffusion, chemisorption and surface potential barriers. It is essential that the surface to be studieg can be prepared in the form of a high curvature tip, with a radius of 10−5cm and can be cleaned sufficiently well for a symmetrical reproducible pattern to be observed.Field Emission technique has been applied to study the behaviour of thin overlayers of gold on GaAs. Using Fowler-Nordheim plots, change in the work function φ, is examined for temperatures, T=77K and T=300K. φ changes slightly for low doses of gold and significantly for larger ones {φ=4.3 − 3.7 eV}. Desorption of gold is also examined and the results indicate two different adsorbed states in Au-overlayers formed at room temperature. Finally, a brief description of sample preparation is also included.
The Effect of Implant and Rapid Thermal Annealing Temperatures on Ion Beam Mixing of Titanium Silicide
Authors: Mattiussi G. A. , Whitton J. L. , Naem A. A. , Ho V. Q. 
Published: March 2011

ABSTRACTIon beam mixing has been used to form layers of titanium disilicide on Si wafers. Doses of Ge+ up to 1×1016 ions/cm2 were implanted at 140 keV through 51 nm of sputtered Ti. The substrate was held at different temperatures; 150°C, 300°C and 400°C. In addition, some samples were processed without temperature control. Two rapid thermal annealing cycles were used, 800°C for 10 s and 650°C for 50 s in an N2 ambient to form stoichiometric TiSi2. As-implanted samples showed an increase in the number of mixed Ti and Si atoms with higher implant temperature and larger dose. In addition, a thin layer with a Ti/Si ratio of 1:1 as seen in some samples indicating possible TiSi phase formation. Lower implant temperatures, higher doses and higher anneal temperatures all produced greater TiSi2 thicknesses. Ion beam mixing yields thicker. silicide layers than those formed without mixing. The silicide interface smoothness was improved by ion beam mixing although some residual implant damage was observed after annealing. The implanted Ge+ accumulated below the silicide/Si interface and in the surface Ti oxide layer.
The Stability of Ion Projection Lithography Masks
Authors: Randall J. N. , Bellavance D. , Sivasankar R. 
Published: March 2011

ABSTRACTIon projection lithography (IPL) has demonstrated the ability to replicate high resolution patterns with very short exposure times. Computer modeling of masks used in a hypothetical IPL system Is accomplished to estimate mask distortion during fabrication and exposure. Radiation cooling is shown to play an important role in temperature control. Two different methods of mask temperature control are examined. Results suggest a high degree of pattern stability can be expected from this type of mask.
Maskless Patterning of Mo and Si by Focused Ion Beam Implantation
Authors: Gamo Kenji , Yonehara Katsuyuki , Nagatomo Shohei , Namba Susumu 
Published: March 2011

ABSTRACTMaskless patterning of Mo and Si was done by implanting 50 keV focused Ga+ ion beam and by plasma etching using CF4 gas. The implantation is done to modify the chemical properties of the sample surface. It was found that Mo films became etch-resistant for the plasma etching after implantation at a dose higher than 4×1015 /cm2. Si crystals showed a positive tone pattern due to a radiation enhanced etching at a dose lower than 5x1016/cm2. At higher doses, the etching rate decreased and above 8 x 1016/cm2, no etching was observed in the implanted region. Patterns with a thickness of a several hundred nanometers were formed by the present maskless patterning technique.
Fabrication of Encapsulated Indium Films for Melting Experiments
Authors: Scofield John H. , Epworth R. W. , Tennant D. M. 
Published: March 2011

ABSTRACTWe describe the fabrication of submicron, multiprobe thin indium film conductors for electrical measurments above their melting transition. Problems unique to handling liquid films were overcome by using tri-level Si3N4/In/W structures. Tungsten (W) leads made good electrical contact to, yet did not alloy With the liquid indium (In). A silicon-nitride (Si3N4 ) encapsulating layer deposited over the In/W devices prevented the indium from forming islands when liquid. Indium wires were fabricated using e-beam lithography and liftoff. Low temperature reactive sputtering technique was used to deposit the Si3N4 without melting the indium. The technique could be easily adapted to use with other low melting point materials.
Submicron Pattern Delineation Using a Pulsed Electron-Beam in Soft Vacuum
Authors: Krishnaswamy Jayaraxn , Li Lumin , Collins G. J. , Hiraoka H. 
Published: March 2011

ABSTRACTWe describe herein an electron-beam, proximity lithograghic process which operates in soft vacuum (50 mT< p <1 Torr) using highly directed electron emission from a cold cathode. The electron-beam operates with large areas(<10 cm2) and with large total currents (Ipeak< 100A). Using this soft vacuum beam we could replicate feature sizes of ∼0.5 μm on∼3 μm thick PMMA, with a resist layer to stencil mask spacing of 25 to 30 μm. While resist exposed in a helium background showed vertical wall profiles (developed thickness ∼3 ¼m), resists exposed in air showed sloped walls (∼ 60°). Resist behavior also appears to be dependent on the number of pulses used for exposure ranging from simple exposure ( 1 to 5 pulses) to self-development ( >25 pulses).
Characterization of Epitaxial Films by Grazing-Incidence X-Ray Diffraction
Authors: Segmüller Armin 
Published: March 2011

ABSTRACTGrazing-incidence x-ray diffraction, a surface-sensitive technique, has been used to obtain structural details parallel to the interface of an epitaxial system, such as lattice parameters, strain, crystallite size and orientation, on films with thicknesses ranging down to a few mono-atomic layers. Tungsten grows epitaxially on the (1102) plane of sapphire, with the orientation W (001) ∥ Al2O3 (1102) and W [110] ∥ Al2O, [1120]. Sufficient diffraction intensity for characterization could be obtained from ∼30A-thick W films. Layers of GaAs can be grown epitaxially on the basal plane of sapphire with the orientation GaAs(111) ∥ Al2O3(00.1) and GaAs [110] ∥ Al2O3[1120]. Niobium films grow on GaAs (001) and (111) substrates with a (001) plane parallel to the interface, whereas molybdenum films prefer to grow with a (111) plane on both substrates. The best orientation, i. e. the smallest mosaic spread, of the film is obtained when the substrate plane has the same symmetry as the preferred film growth plane. In all these cases with relatively large misfit, the strain observed parallel to the interface is only a small fraction of the theoretical misfit strain, indicating the relief of the misfit strain within the first few atomic layers.
Nexafs Studies of Unsaturated Carboxylic Acids and Alcohols Adsorbed on the Si(111)(7×7) Surface
Authors: Outka D. A. , Stöhr J. , Madix R. J. , Rotermund H. H. , Hermsmeier B. , Solomon J. 
Published: March 2011

ABSTRACTThe adsorption of formic acid (HCOOH), acrylic acid (CH2= CHCO2H), propiolic acid (HC=CCO2H), and the corresponding alcohols on the Si(111)(7×7) surface have been investigated by NEXAFS. In each case, well-defined dipole transitions to σ* and π* molecular orbital s were observed above the C and 0 K-edges and used to probe the orientation and chemistry of these molecules on this silicon surface. Monolayer coverages of these molecules on silicon, bond strongly to the silicon surface via the carboxylic acid or alcohol group. In contrast, the C-C double and triple bonds of these molecules do not react initially with the silicon surface. Upon heating, however, the C-C double and triple bonds which are held in proximity to the surface by the carboxylic acid or alcohol group, are lost either by polymerization on the surface or reaction with the silicon substrate. These results illustrate the capabilities of NEXAFS to investigate molecular orientations on surfaces and the electronic structure of polyatomic adsorbates.
Mixed-Cation Optical Thin Films from Tailored Composition Targets
Authors: Denatale J. F. , Harker A. B. 
Published: March 2011

ABSTRACTAmorphous optical thin films of mixed oxides have been fabricated whose composition and optical index of refraction have been varied in a controlled manner as a function of film thickness using a single ion beam source with tailored composition targets. The microstructure, transformation behavior, and stress in the films are being studied for the systems Al2O3-TiO2, TiO2-SiO2, and ZrO2-SiO2. The technique has been found to be a convenient means of producing gradient index optical structures.
High Temperature Implantation of Single Crystal Beta Silicon Carbide Thin Films
Authors: Edmond J. A. , Withrow S. P. , Wadlin W. , Davis R. F. 
Published: March 2011

ABSTRACTIons of aluminum, gallium and nitrogen were implanted into (100) oriented β-SiC thin films at temperatures of 623K, 823K and 1023K. Rutherford backscattering/ion channeling analyses revealed that implantation of any one of the ionic species at 623K resulted in only slight crystal lattice damage. In comparison, implantation conducted using the same dosimetry and energy at room temperature resulted in extensive lattice damage; in the case of gallium, amorphization occurred. The backscattered yield from samples implanted at 1023K was nearly that of a virgin aligned spectra. This in situ annealing effect did not, however, result in the complete electrical activation of implanted species. In order to increase the percent of electrical activation, samples were annealed at 1473K for 1800s following implantation. Differential capacitance-voltage, spreading resistance and sheet resistance measurements were made in order to electrically characterize these layers. These measurements indicated the activation of p-type and n-type species in samples implanted with aluminum or gallium and nitrogen, respectively. The authors have previously reported p-type formation in β-SiC implanted with aluminum at room temperature following a 2073K - 300s anneal. By heating to 1023K during implantation and annealing at 1473K after implantation, improved structural and electrical properties have been achieved.
Theoretical Investigation of Twist Boundaries in Germanium
Authors: Payne M. C. , Bristowe P. D. , Joannopoulos J. D. 
Published: March 2011

ABSTRACTResults of the first completely ab-initio investigation of the microscopic structure of a grain boundary in a semiconductor are presented. Using the molecular dynamics simulated annealing method for performing total energy calculations within the LDA and pseudopotential approximations, the σ=5(001) twist boundary in germanium is studied. A low energy structure is identified which exhibits a rigid body translation and a small contraction at the boundary.
a-Si:H Films Prepared by Ecr Plasma Enhanced CVD
Authors: Yamamoto H. , Hine S. , Yamakawa S. , Tubouchi N. , Miyamura M. 
Published: March 2011

ABSTRACTHydrogenated amorphous silicon (a-Si:H) films prepared by electron cyclotron resonance plasma enhanced CVD (ECR PECVD) were investigated electrically and optically. The electrical and optical properties of a-Si:H were strongly dependent on magnet coil current, microwave power, and substrate temperature. A high deposition rate of a-Si:H up to 150 nm/min was realized by this technology. The photoconductive characteristics prepared at 300°C are comparable to those obtained by glow discharge PECVD (GD PECVD).
Elastic Properties of Superlattices
Authors: Grimsditch M. 
Published: March 2011

ABSTRACTA calculation of the effective elastic moduli of a super-lattice, in terms of the elastic moduli of its constituents, is presented. Contrary to what has been found in many real systems, these calculations show that in the long wavelength limit the effective elastic moduli are independent of the modulation wavelength. A discussion of the experimental results on Nb/Cu, Mo/Ni and Au/Cr shows that the elastic anomalies can be understood on the basis of concomitant changes in lattice spacings.
Effect of Si Implantation and Rapid Thermal Annealing on GaAs/AlGaAs Superlattice Disordering.
Authors: Flood J. D. , Bahir G. , Merz J. L. , Kobayashi J. , Fukunaga T. , Ishida K. , Nakashima H. 
Published: March 2011

ABSTRACTThe enhanced disordering of GaAs/AlGaAs superlattices by diffusion of Zn or Si has been reported by many authors. In the case of Si diffusion, the Si can be introduced during epitaxial growth, by implantation, or by diffusion from a sputtered Si mask. In this paper ion implantation is investigated, and the effect of rapid thermal annealing (RTA), used to minimize Si diffusion while eliminating the implant damage, is compared with furnace annealing (FA). Using low temperature photoluminescence (PL) and SIMS, it is found that no disordering of a GaAs/Al0.5Ga0.5As superlattice takes place for a 2 sec anneal at 900°C, and very minimal partial disordering is observed (reproducibly) for a 10 sec anneal at 970°C. This is in sharp contrast with the FA case (850°C for 30 min), for which significant disordering occurs. The PL spectra show luminescence from both GaAs and GaAs/Al0.5Ga0.5As layers in the case of high-temperature RTA suggesting that recrystallization has occurred without disorder, whereas strong emission is observed after FA which corresponds to a disordered layer of average-composition GaAs/Al0.15Ga0.25As In both cases, PL indicates that annealing of the implant damage has occurred. Thus, damage can be eliminated either with or without disordering the superlattice by using FA or RTA, respectively. This is important for 2-D electron gas structures, for which no broadening of the hetero-interface is desired.
Electron Transport Through Epitaxial Metal/Semiconductor Heterostructures
Authors: Levi A. F. J. , Tung R. T. , Batstone J. L. , Gibson J. M. , Anzlowar M. , Chantre A. 
Published: March 2011

ABSTRACTAbrupt, epitaxial silicide/silicon heterostructures may be grown so that, for the first time, the physics of electron transport across near perfect, single crystal, metal/semiconductor interfaces may be probed experimentally. Transport measurements through type-A and -B oriented NiSi2 layers on Si(111) substrates have revealed Schottky barrier heights differing by 140 meV. In this paper we present results of experiments designed to explore the possible role of bulk and interface defects in determining the potential barrier at these near ideal epitaxial metal-semiconductor contacts. We have found little evidence for the presence of defects and the Schottky barrier is insensitive to details of the microscopic interfacial perfection. By contrast we find that both the electrical quality and magnitude of the barrier occurring at the NiSi2 /Si(100) heterojunction are dependent upon details of the microscopic interfacial perfection.
The Composition Dependence of the Interdiffusivity in Artificial Amorphous Si/Ge Multilayers
Authors: Prokes S. M. , Spaepen F. 
Published: March 2011

ABSTRACTThe interdirfusivity in artificial amorphous Si/Ge multilayers is found to be strongly dependent on the average composition of the films. The interdirfusivity of films with different average composition was determined from the decay of the first X-ray satellite. The nonlinear diffusion resulting from the composition dependence was observed by the evolution of the higher-order satellites.
Properties of MoO3 Thin Film Polymorphs
Authors: McCARRON E. M. , Carcia P. F. 
Published: March 2011

ABSTRACTThin film polymorphs of molybdenum trioxide have been synthesized by RF sputtering. Films deposited on thermally floating substrates are polycrystalline and exhibit preferred orientation. Depending upon the oxygen partial pressure maintained during sputtering, the films can be made to crystallize in either the thermodynamically stable orthorhombic a MoO3 form (unique 2D-layered structure) or the metastable monoclinic /3 MoO3 phase (3D ReO3-related structure). Metastable β films can be converted thermally to the a phase and the transformation appears topotactic. Films deposited on cooled substrates are amorphous. A correlation between the particular phase formed and adatom mobility is noted.
Dopant Diffusion in TiSi2
Authors: d'Heurle F. M. , Michel A. E. , LeGoues F. K. , Scilla G. , Wetzel J. T. , Gas P. 
Published: March 2011

ABSTRACTDopant elements, B and Ga, P, As and Sb, and Ge as well, have been implanted into thick (350–400 nm) layers of TiSi2 prepared by Ti-Si reaction. Both B and Sb appear to be immobile, this behavior is thought to result from very small solid solubilities, rather than from very small diffusion coefficients. The other elements display about the same behavior, with detectable grain boundary diffusion at temperatures as low as 600°C, and lattice diffusion becoming considerable at 750°C, so that with the cooperation of both phenomena almost complete homogenisation of these relatively thick layers occurs in 30 minutes at 800°C. Germanium is used in lieu of a Si radioactive tracer because it can be analyzed by Secondary Ion Mass Spectroscopy. Its behavior is thought to imply that there is little equilibrium adsorption of the dopant elements at the Si/TiSi2 interface. The comparable values of the diffusion coefficients for the mobile elements confirm the anticipation that the dopants move as substitutional atoms on the Si sublattice. Results obtained with some samples implanted with both dopant and Ti indicate that in these silicon-saturated suicide layers the diffusion process is not significantly affected by small changes in stoichiometry.
X-Ray-Optical Multilayer Structures Studied Using High Resolution Electron Microscopy.
Authors: Stearns Mary Beth , Petford-Long Amanda K. , Chang C.-H. , Stearns D. G. , Ceglio N. M. , Havryluk A. M. 
Published: March 2011

ABSTRACTThe technique of high resolution electron microscopy has been used to examine the structure of several multilayer systems (MLS) on an atomic scale. Mo/Si multilayers, in use in a number of x-ray optical element applications, and Mo/Si multilayers, of interest because of their magnetic properties, have been imaged in cross-section. Layer thicknesses, flatness and smoothness have been analysed: the layer width can vary by up to 0.6nm from the average value, and the layer flatness depends on the quality of the substrate surface for amorphous MLS, and on the details of the crystalline growth for the crystalline materials. The degree of crystallinity and the crystal orientation within the layers have also been investigated. In both cases, the high-Z layers are predominantly crystalline and the Si layers appear amorphous. Amorphous interfacial regions are visible between the Mo and Si layers, and crystalline cobalt suicide interfacial regions between the Co and Si layers. Using the structural measurements obtained from the HREM results, theoretical x-ray reflectivity behaviour has been calculated. It fits the experimental data very well.
Growth of Epitaxial CoSi2/Si Multilayers
Authors: Runt B. D. , Lewis N. , Schotalter L. J. , Hall E. L. , Turner L. G. 
Published: March 2011

ABSTRACTEpitaxial CoSi2/Si multilayers have been grown on Si(111) substrates with up to four bilayers of suicide and Si. To our knowledge, these are the first reported epitaxial metal-semiconductor multilayer structures. The growth of these heterostructures is complicated by pinhole formation in the suicide layers and by nonuniform growth of Si over the suicide films, but these problems can be controlled through nse of proper growth techniques. CoSi2 pinhole formation has been significantly reduced by utilizing a novel solid phase epitaxy technique in which room-temperature-deposited Co/Si bilayers are annealed to 600–650δC to form the suicide layers. Islanding in the Si layers is minimized by depositing a thin (<100Å) Si layer at room temperature with subsequent high temperature growth of the remainder of the Si. Cross-sectional transmission electron microscopy studies demonstrate that these growth procedures dramatically improve the continuity and quality of the CoSi. and Si multilayers.
Interfacial Reactions in Titanium - Silicon Multilayers
Authors: Holloway Karen , Sinclair Robert 
Published: March 2011

ABSTRACTWe have used cross-section and through-foil TEM, RBS, and x-ray diffraction to investigate reactions upon rapid thermal annealing of sputtered Ti-Si multilayers of various compositions and bilayer spacings. This study addresses the behavior of the Ti-Si interface at low annealing temperatures (T< 600δC) to determine the extent to which interdiffusion occurs prior to suicide formation, and to detect the formation of the first suicide at an early stage. Whereas most previous work studied a single Ti-Si interface, we have used multilayer films because a reaction occurs at many interfaces, allowing detection of a phase even if it is formed to a very limited extent.The silicon layers in the as-deposited films are amorphous; the titanium layers are polycrystalline hep. The compositions of the samples are 40 at.% Ti, 60 at.% Si and 60 at.% Ti, 40 aL% Si, and the bilayer periodicity is about 10 nm. After a 30 second anneal at 455°C, significant interdiffusion occurs and we observed the formation of an amorphous Ti-Si alloy by interfacial reaction. The metastable disilicide, C49 TiSi2, nucleated along with a small amount of TiSi in the sample with higher silicon content (60%) upon annealing at 550°C for 10 seconds, but the amorphous alloy remained as the only product of reaction in the 40 at. % Si sample. Cross-section TEM of a sample fabricated at 60°C suggests that interdiffusion had begun during deposition of the films.
A High Schottky Barrier Contact of Metallic Amorphous Si-P on P-Type Si
Authors: Ogino T. , Sakaue M. , Amemiya Y. 
Published: March 2011

ABSTRACTA high Schottky barrier contact is formed when amorphous Si-P solid solution film and p-type Si are brought into contact. Amorphous Si-P films were deposited by thermal decomposition of a Si2H6-PH3 mixture at 500°C. It was found that conductivity increases rapidly when PH3/Si2H6, is increased from 0.2 to 2. When PH3/i2H6 = 2, conductivity is 0.15 S/cm, and the dominant conduction mechanism is variable-range hopping. Barrier height of amorphous Si-P/p-type Si Schottky contact is estimated to be 0.8 – 0.85 V. This value exceeds the barrier height formed by any normal metal.