bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Implantation Damage and B Diffusion in Low Energy B Implantation with Ge Preimplantation
Authors: Kase M. , Mori H.
Published: April 2011

For low energy B (LEB) implantation into Si, the channeling tail is larger than for BF2+ implantation, so Ge+ preamorphization is expected to provide a shallower junction. We studied the Ge+ and B+ implantation damages and the damage-induced B diffusion. The substrate implanted Ge+ with 2×l014 cm-2, that is, a complete amorphization, retains less residual defects after RTA. However the sheet resistivity (S) is higher than the sample implanted with only LEB. Solid phase epitaxy (SPE) of amorphized layer causes B out-diffusion. The diffusion length of the amorphized substrate is smaller than that of LEB. We expect that the B diffusion is enhanced by the LEB damage, which corresponds to the enhanced diffusion of light damage.
Detailed Analysis and Computationally Efficient Modeling of Ultra-Shallow Dopant Profiles Obtained by Low Energy B, Bf2, and as Ion Implantation
Authors: Parab K. B. , Yang S.-H. , Morris S. J. , Tian S. , Morris M. , Obradovich B. , Tasch A. F. , Kamenitsa D. , Simonton R. , Magee C.
Published: April 2011

With increasing levels of integration, future generations of integrated circuit technology will require extremely shallow dopant profiles. Ion implantation has long been used in semiconductor material processing and will be a vitally important technique for obtaining ultra-shallow dopant profiles. However, implant channeling for low energy ion implantation must be understood and minimized. We report the results of a detailed experimental analysis of 275 ultra-shallow boron, BF2, and arsenic as-implanted profiles, and the development of an accurate and computationally efficient model for ultra-shallow implants.

The ultra-shallow dopant profiles have been modeled by using the Dual-Pearson approach, which employs a weighted sum of two Pearson functions to simulate the profiles. The computationally efficient model covers the following range of implant parameters: implant species B, BF2, As; implant energies from 1 keV to 15 keV; any dose; tilt angles from 0° to 10°; all rotation angles (0°-360°). This experimental analysis is important for the development of scaled devices with ultra-shallow junctions, and the computationally efficient model will enable process simulators to predict ultra-shallow as-implanted profiles accurately.
Mev Ion Induced Damages and their Annealing Behavior in Silicon
Authors: Cho Nam-Hoon , Jang Ki-Wan , Lee Jeong-Yong , Ro Jae-Sang
Published: April 2011

MeV ion induced damage and annealing behavior in Si are reported using 3 ion species such as B, P and Si. Si self implantations were done to reveal the intrinsic behavior of secondary defect formation by excluding the possibility of chemical interactions between substrate atoms and dopant atoms. Experimental results of B and P implantations were compared to those of Si. TEM observations showed that interstitial type secondary defects are exclusively formed at around Rp. DCXRD rocking curve analyses indicated that an isolated layer of (+) strain is built up at around Rp after strain relaxation by annealing. Sources for secondary defects were thought to be Si self interstitials. Atomistic mechanisms of secondary defect formation and the effect of ion species on them are discussed.
The Effects of Low Energy Ion-Beam Milling on the Physical and Electrical Properties of N-GaAs.
Authors: Seng W.F. , Barnes P.A. , Lovejoy M.L. , Fu L.P. , Gilliland G.D. , Ila D.
Published: April 2011

Low energy neutral Ar ion-beam etching of n-GaAs was investigated as a possible “cleaning” procedure prior to contact metallization. The ion-beam source energy was varied between 35 eV and 1200 eV at a fixed current density of 1 mA/cm2. The effects of ion-milling on lightly doped n-GaAs were analyzed electrically by measuring current-voltage (IV) and capacitance-voltage (CV) characteristics of Schottky barriers formed after the ion-milling. The metal semiconductor barriers were prepared immediately following ion-milling without breaking vacuum. Photoluminescence and Rutherford Backscattering (RBS) were used to determine if any physical modification of the surface and near surface region of the ion-milled substrates had occurred.
Annealing Effect of Cd+ Ion-Implanted Liquid Encapsulated Czochralski-GaAs
Authors: Kawasumi Y. , Makita Y. , Kimura S. , Iida T. , Kotani M. , Obara A. , Shibata H. , Kobayashi N. , Tsukamoto T. , Kobayashi E.
Published: April 2011

Furnace annealing (FA) and rapid thermal annealing (RTA) were made for Cd+ ion-implanted GaAs with Cd concentration, [Cd] from 1×1016cm−3 to 3×1021 cm−3. In FA samples, Raman scattering spectra exhibited a single peak at 292 cm−1 for entire [Cd] range which is LO-phonon mode from (100) GaAs. In RTA samples, LO-phonon mode is a single peak for [Cd]<1×1019cm−3 but with growing [Cd], TO-phonon mode appears for [Cd] 1×1020cm3 and becomes a dominant signal for [Cd]=3×1021 cm−3. The quenching of LO-phonon mode with increasing [Cd] was more clearly observed in RTA samples than in FA ones. Hall-effects results, however, showed that activation rate of RTA samples is 6–7 times larger than that of FA ones for [Cd] 1×1021 cm−3. 2K photoluminescence spectra revealed that in FA samples multiple shallow emissions associated with Cd are formed while in RTA ones the dominant emission is the band to Cd acceptor transition.
Ion Mixing in Film-Substrate Systems Under Polyenergetic Ar+Ion Beam Irradiation
Authors: Kalin B.A. , Volkov N.V. , Gladkov B.P. , Sabo S.E. , Atalikova I.H. , Altuhov A.A.
Published: April 2011

The results of alloying Al, Fe, and Mo surfaces by Be, Al, Ni, Sn under polyenergetic Ar+ ion beam irradiation with a mean energy of 10 keV have been presented. It has been shown that along with film and substrate materials sputtering there takes place the penetration of film atoms into substrate materials at a depth which is significantly greater (by a factor of 3… 10) than the projective range of ions in the given materials. The analysis of possible alloying depths with regard to different models (pure radiation range for monoenergetic ion beams; when the decrease of concentration is approximated by the exponential dependence; when the internal forcing out stresses are taken into account) for equal irradiation dose shows that the model, in which the migration of implanted atoms in the fields of forcing out stresses are considered, gives most close agreement between the calculated data and experimental ones.
Alumina-Silicate Glass Interfacial Properties Probed by Micromechanical Testing Techniques
Authors: Zagrebelnya Andrey V. , Nelson John C. , Lilleodden Erica T. , Ramamurthy Sundar , Carter C. Barry
Published: April 2011

Micromechanical properties of the interfaces between alumina and calcium-aluminosilicate (CAS) glasses were tested using various micro/nanoindentation techniques. The interfaces were produced by depositing continuous films of anorhtite (CaAl2Si2O8) onto single-crstal α-Al2O3 of two crystallographic orientations by pulsed-laser deposition (PLD).

The mechanical behavior of the interfaces was examined using two different depthsensing indentation instruments. Three types of tests, namely indentation, microscratch, and in-situ indentation combined with atomic force microscopy (AFM) imaging were conducted using different operating modes. The deformation behavior observed for the indentations and microscratches has been correlated with irregularities observed in the load-displacement curves. In the first two cases, scanning electron microscopy (SEM) has been used to characterize the deformation structures associated with the deformed regions. The in-situ experiments allow force-displacement measurements and AFM imaging immediately before and after indentation. The preindent and postindent morphology of the surface could then be characterized.
Epitaxial Growth and Structure of Cubic and Pseudocubic Perovskite Films on Perovskite Substrates
Authors: Langjahr P. A. , Wagner T. , RÜhle M. , Lange F. F.
Published: April 2011

Cubic and pseudocubic perovskite films on perovskite substrates are used to study the influence of the lattice mismatch on the epitaxial growth of thin films on substrates of the same structure. For the growth of the films, a metalorganic decomposition route (MOD) using 2-ethylhexanoates and neodecanoates as precursors, was developed. The decomposition of the precursors was investigated with thermogravimetric analysis (TGA) and x-ray diffraction (XRD). The films were spin-coated on (001)-oriented SrTiO3- and LaAlO3-substrates, pyrolyzed and afterwards annealed between 600°C and 1200°C. XRD-nvestigations and conventional transmission electron microscopy (CTEM) show, that epitaxial films with the orientation relationship [100](001) film ║ [100](001) substrate can be grown. With XRD, it could be shown, that not only ternary oxide films (SrZrO3, BaZrO3and BaCeO3), but also perovskite solid solution films (SrTi0.5Zr0.5O3and BaCe0.5Zr0.5O3) can be prepared. Strong interdiffusion, detected by a shift of the film lattice parameter towards the substrate lattice parameter was found in SrZrO3- and BaZrO3-films on SrTiO3, annealed at temperatures above 1050°C. High resolution electron microscopy (HREM) studies of SrZrO3on SrTiO3show that a crystalline semicoherent interface with a periodical array of misfit dislocations is present.
Growth and Characterization of Pb-Based Ferroelectric Oxide Thin Films by Mocvd
Authors: Shimizu Masaru , Shiosaki Tadashi
Published: April 2011

Using the MOCVD process to produce Pb(Zr, Ti)O3 (PZT) thin films, control of the film stoichiometry and crystalline phase was achieved. The PZT films obtained showed good step coverage, 67%. Uniform PZT and PLZT thin films with a variation of film thickness of less than ±1.5% were successfully obtained on a 6–8 inch silicon wafer. For the evaluation of the crystallinity and epitaxial relationship of the PZT thin films, the total reflection X-ray diffraction (TRXD) method was used for the first time. Using TRXD, the in-plane orientations of PZT and Pt in PZT/Pt/MgO were evaluated. The growth mechanism of PbTiO3 and PZT thin films at the initial growth stage was also investigated using an atomic force microscope (AFM). The switching characteristics of PZT capacitors using Ir and IrO2 electrodes for memory device applications were also investigated and a PZT capacitor with no fatigue up to a switching cycle of 1011 was obtained.
Structural Control of Epitaxially Grown Sputtered Perovskite Thin Films
Authors: Wasa Kiyotaka , Sato Toshifumi , Adachi Hideaki , Setsune Kentaro , Trolier-McKinstry S. , Schlom Darrell G.
Published: April 2011

Thin films of perovskite Pb–Ti–O3 families were heteroepitaxially grown by sputtering on (0001)sapphire and/or (001)SrTiO (ST). These epitaxial films contained microstructures, although X–ray diffraction analysis suggested formation of single crystal phase with three dimentional crystal orientation. Their microstructures were studied by the electron microscopy, atomic force microscopy, and spectroscopic ellipsometry so as to find factors which influence the formation of the microstructure. It was found that the orientation of the substrate surface and the chemical composition of adatoms during initial film growth strongly affected the formation of the microstructures. Sputtered PbTiO3 (PT) thin films under a stoichiometric condition on a miscut(001) ST(miscut 1.7 degree) realized the growth of continuous single crystal thin films of 10–100nm thick with extremely smooth surface with surface roughness less than 3nm. Deposition on a miscut substrate under a stoichiometric condition is essential to make continuous thin films of perovskite of single crystal phase.
Homo and Heteroepitaxial Growth of LiTaO3 and LiNbO3 by Mbe
Authors: Sitar Z. , Gitmans F. , Liu W. , Günter P.
Published: April 2011

Thin films and superlattices of LiTaO3 and LiNbO3 were grown on (0001) LiTaO3 and LiNbO3 wafers by molecular beam epitaxy. Solid sources were employed for the evaporation of Li, Ta, and Nb while oxygen was activated in an ECR plasma source. Samples were completely oxidized during the growth as confirmed by quantitative surface analyses. Crystalline films were obtained on both substrates at a growth rate of 0.1 nm/s and substrate temperature of 900°C. Films were caxis oriented but showed in-plane 60° rotational domains. Superlattice structure with a bilayer period of 10 nm was grown on LiNbO3. It showed well defined interfaces and appeared to be strained.
Optical Properties of Epitaxial Plt Thin Films
Authors: Kim Y. , Erbil A. , Boatner L. A. , Steingart L. , Mensah T. , Hiamang S.
Published: April 2011

Metalorganic chemical vapor deposition (MOCVD) was used to prepare epitaxial or highly oriented PLT (Pb1-xLaxTiO3) thin films with x in the range of 0.21 to 0.34. The growth of PLT films resulted in three-dimensional epitaxial heterostructures on (100) surface of the MgO and the KTaO3 substrates. The PLT film grown on the KTaO3 (100) substrate has a significantly lower minimum channeling yield compared to that on the MgO (100) substrate because of the smaller lattice mismatch. The thickness and the refractive indices in the wavelength range of 435 to 1,523 nm were measured by the prism coupling method. The measured film thickness of 570 nm was in good agreement with that from RBS measurements. The refractive index of PLT film is smaller than that of PbTiO3, its difference at 632.8 nm is about 2.5 %. The dispersion of the refractive index was well fitted to a Sellmeier dispersion formula.
Microstructure of YBa2Cu3O7-δ/Ag Bilayers Grown In Situ on Step-Edge SrTiO3 Substrates
Authors: Gong Z. H. , Grepstad J. K. , Andersen S. , Bardal A.
Published: April 2011

The microstructure of YBa2Cu3O7-δ(YBCO)/Ag bilayers sputter deposited in situ on step-edge SrTiO3 (STO) substrates, was carefully examined by transmission electron microscopy (TEM). Considerable variation in the YBCO film growth morphology is found near steps, including film protrusions beyond the step edges and film growth on slopes. Lattice images recorded near steps unveil a high density of crystalline defects in the film. An increased density of defects is also found near the substrate interface for film grown on etched STO surface. However, these defects are confined to the interface region and do not propagate beyond the scale of the STO surface roughness. Comparison of TEM lattice images of YBCO(100)/Ag and YBCO(001)/Ag junctions from the same specimen unveils a distinct difference in the interfacial microstructure of those two junctions. Whereas the former exhibits a sharp crystalline interface, the latter typically features a thin ( ∼ 20 Å ) interfacial layer of amorphous material. The YBCO film morphology and the high density of defects in the step edge region uncovered in this study suggest that manufacture of reproducible and uniform YBCO/Ag (Au)/YBCO (SNS) Josephson junctions using the step-edge technique, will prove a difficult task.
Microstructure of SrTiO3 Thin Films as Single Layer and Incorporated in Yba2Cu3O7-x/SrTiO3 Multilayers
Authors: Ryen L. , Olssoni E. , Madsen L. D. , Johnson C. N. L. , Wang X. , Jacobsen S. N. , Helmersson U. , Wernlund L.-D. , Rudner S.
Published: April 2011

Epitaxial single layer (001) SrTiO3 films and an epitaxial Yba2Cu3O7-x/SrTiO3 multilayer were dc and rf sputtered on (110)rhombohedral LaAIO3 substrates. The microstructure of the films was characterised using transmission electron microscopy. The single layer SrTiO3 films exhibited different columnar morphologies. The column boundaries were due to the lattice mismatch between film and substrate. The boundaries were associated with interfacial dislocations at the film/substrate interface, where the dislocations relaxed the strain in the a, b plane. The columns consisted of individual subgrains. These subgrains were misoriented with respect to each other, with different in-plane orientations and different tilts of the (001) planes. The subgrain boundaries were antiphase or tilt boundaries.

The individual layers of the Yba2Cu3O7-x/SrTiO3 multilayer were relatively uniform. A distortion of the SrTiO3 unit cell of 0.9% in the ‘001’ direction and a Sr/Ti ratio of 0.62±0.04 was observed, both in correspondence with the single layer SrTiO3 films. Areas with different tilt of the (001)-planes were also present, within each individual SrTiO3 layer.
Effects of Metal Buffer Layer on the Epitaxial Growth of YBa2Cu3O7-y. Superconducting Films by Dipping-Pyrolysis Process
Authors: Manabe T. , Yamaguchi I. , Nakamura S. , Kondo W. , Mizuta S. , Kumagai T.
Published: April 2011

Superconducting Yba2Cu3O7 -x(YBCO) films were prepared by dipping-pyrolysis process on SrTiO3 (001) or on MgO (001) substrates covered with a metal (Au or Ag) buffer layer, and the effects of these metal layers on the growth of YBCO films were investigated. Epitaxial growth of YBCO was found to be suppressed by the Au buffer layer, which crystallized to exhibit (111) orientation, after heat treatment at 700°C and higher. On the other hand, epitaxial YBCO films were obtained starting with Ag buffer layer by heat treatment at 700°C and higher, after which most of Ag was accumulated to particles. It was also found that the annealing temperature required for the epitaxial growth of YBCO films on MgO was lowered to 850°C by adopting the Ag buffer layer.
Magnetic and Structural Properties of MBE-grown Oxidic Multilayers
Authors: Bloemen P. J. H. , van der heijden P. A. A. , Wolf R. M. , de Stegge J. Aan , Kohlhepp J. T. , Reinders A. , Jungblut R. M. , van der Zaag P. J. , de Jonge W. J. M.
Published: April 2011

Multilayers composed of oxides including Fe3O4, CoxFe3−x, O4, CoO, NiO and MgO have been grown epitaxially by MBE on MgO(100) single crystal substrates. These structures can be grown with a high crystallinity in the form of flat layers having sharp interfaces. RHEED studies which commonly yielded sharp streaks accompanied by Kikuchi lines show that, for instance, growth of CoO on Fe3O4 changes the RHEED pattern from that consistent with a spinel structure to that of a rocksalt structure within about one and a half unit cell of CoO. STM studies on a 400 Å Fe3O4 layer displaying atomic resolution enabled us to identify the origin of the reconstruction that one commonly observes in the RHEED and LEED patterns for magnetite. Regarding important fundamental magnetic parameters, relevant thickness dependencies were mapped out using localized magneto-optical Kerr effect experiments performed on several samples that routinely included one or multiple wedge shaped layers. These studies revealed the existence of a region in the Fe3O4 layer near the interfaces which exhibits no net magnetic moment, strain driven perpendicular orientated magnetization for the CoO/Fe3O4(100) and CoO/CoxFe3−xO4(100) bilayer systems, and information on the thickness dependence of the magnetic interlayer coupling across an MgO spacer layer.
Growth and Stability of MgO/NiO Multilayered Films on Single Crystal NiO(100)
Authors: Imaduddin S. , Lad R. J.
Published: April 2011

The less than 1% lattice mismatch between MgO and NiO makes them ideal candidates for investigating the growth and stability of multilayered oxide films. Ultra-thin multilayers composed of alternating films of MgO and NiO were deposited onto a stoichiometric NiO(100) single crystal substrate at 250°C by evaporating Mg and Ni in 5×10−7 Torr of O2, respectively. The structure of these multilayers was determined using LEED. Reactivity and chemical composition studies of the MgO/NiO interfaces were carried out using XPS and UPS. The MgO/NiO multilayers grow epitaxially on NiO(100), as evidenced by LEED. XPS and UPS analysis indicates attenuation of the NiO or MgO peaks during growth which is consistent with discrete layering. Chemical analysis also reveals negligible intermixing of the MgO and NiO layers during deposition. Results pertaining to the thermal stability of the multilayers show that UHV annealing above 750°C results in significant diffusion of MgO into the NiO(100) substrate.
Localized-Itinerant Electron Transitions in the Orthomanganites
Authors: Goodenough John B.
Published: April 2011

The AMO3 perovskites containing transition-metal atoms M have an MO3 array with M-O-M bond angles 180°-φ in which the angle φ increases with the mismatch of the A-O and M-O equilibrium bond lengths. The tight-binding bandwidths for the π-bonding t and σ-bonding e orbitals of d-orbital parentage are Wπ < Wσ. In the orthomanganites Ln1−xAxMnO3 with A an alkaline earth, the octahedral-site high-spin Mn3+ ions have a d-electron configuration t3e1:5Eg that is orbitally twofold-degenerate, and the on-site electron-electron coulomb energy for adding a fifth d electron is Uσ ≈Wσ > Wπ. Consequently the equilibrium reaction t3e1 ≈ t3 σ*1 for a first-order transition from localized-e to itinerant-σ* electrons is shifted to the left as the bandwidth Wσ ≈ 12 εσλσ2 cos φ is narrowed by increasing φ, by perturbations of the periodic potential of the MO3 array, and/or by increasing spin-disorder scattering; it is shifted to the right by oxidation of the MnO3 array, by application of a magnetic field, and by pressure. Cross-over from polaronic-e to itinerant-σ* electrons at a ferromagnetic Curie temperature Tc or a charge-ordering temperature Tco < Tc can give a “colossal” negative magnetoresistance provided the Fermi energy εF lies below a mobility edge μc in the narrow σ* band of the ferromagnetic phase. Cooperative Jahn-Teller distortions that remove the orbital degeneracy of a localized 5Eg configuration also introduce unusual antiferromagnetic ordering of the manganese-atom spins.
Effect of Growth Conditions and Buffer Layers on the Metal-Insulator Transition in V2O3 Thin Films
Authors: Schuler H. , Weissmann G. , Renner C. , Six S. , Klimm S. , Simmet F. , Horn S.
Published: April 2011

Thin films of V2O3 with thickness from 20 to 450 nm were deposited on (0001) oriented sapphire substrates by reactive e-beam evaporation. LEED, x-ray diffraction and AFM studies show highly oriented grains with a lateral size of 50 to 800 nm, dependent on substrate temperature and deposition rate. The films were characterized by optical and infrared transmission, electrical resistance and Hall effect measurements. Films grown directly on the Al2O3-substrate show a very broad metal-insulator (MI) transition as a function of temperature. The width of the transition decreases with increasing film thickness. The insertion of Cr2O3 buffer layers decreases the transition width by a further factor of three. The electronic properties of the films can be drastically influenced by the growth conditions.
Domain Structure and Colossal Magnetoresistance of La1−xSrxCoO3 and La1−xCaxMnO3
Authors: Wang Z. L. , Zhang Jiming , Berta Y.
Published: April 2011

La1−xSrxCoO3 (LSCO) and La1−xCaxMnO3 (LCMO) are a class of magnetic oxides exhibiting the colossal magnetoresistance (CMR) effect. However, the CMR ratio of LSCO is much lower than that of LCMO. Microstructure studies were carried out to understand this difference. In La0.5Sr0.5CoO3 (LSCO), an ordered, anisotropic perovskite-type structure n-LSCO was observed. The ordered structure has a tetragonal cell with a La-Co-Sr-Co- [001] layered atom distribution along the c-axis. This new structure is intrinsic for the LSCO system and is a direct result of the lattice substitution between La and Sr. The entire film is composed of [001], [010] and [100] anisotropic domains with sizes on the order of 30–200 nm. The La0 7Ca0.3MnO3 (LCMO) film, however, does not exhibit a domain structure. It is concluded that the domain structure may have negative effect on the CMR ratio.
The Origin of Resonance Phenomena in Reflection High-Energy Electron Diffraction
Authors: Dudarev S. L. , Whelan M. J.
Published: April 2011

Resonance scattering of high-energy electrons is responsible for the appearance of bright features observed in reflection high-energy electron diffraction (RHEED) patterns and has found numerous applications in reflection electron microscopy and in RHEED studies of dynamics of molecular beam epitaxial growth of semiconductor crystals. In this paper we report on recent developments in theoretical understanding of the processes leading to resonance reflection of high-energy electrons from a crystal surface.
In-Situ Observation of Deformation Associated with R-Phase in NiTi Shape Memory Alloy
Authors: Gao Y. , Liu Y. Q. , Wu K. H.
Published: April 2011

An in-situ straining experiment was performed in a transmission electron microscope (TEM) on the polycrystalline Ti49Ni51 alloy with full R-phase at room temperature. The reorientation of Rphase variants to a single, favorable one was observed under small stress at the beginning of straining, corresponding to the deformation mode of the first yielding stage. During further straining, the observation showed that the reoriented R-phase undergoes a stress-induced martensite transformation, and this dynamic process was considered to contribute to the second stage deformation in the R-phase stress-strain curve. The orientation relationship between the R-phase and stress-induced martensite has been determined and the internal (001)M twins were found in the stressinduced martensite plates.
In-Situ Dynamic Transformation of Vanadyl Hydrogen Phosphate Hydrate, VOHPO4·1/2H2O, to Vanadyl Pyrophosphate Catalyst, (VO)2P2O7
Authors: Gai P. L. , Torardi C. C.
Published: April 2011

We report, for the first time, direct studies of the dynamic VOHPO4·1/2H2O precursor to (VO)2P2O7 catalyst transformation using recently developed in-situ environmental-cell, high-resolution, electron microscopy (in-situ ECELL-HREM) under controlled environments. Our observations provide fundamental evidence concerning the nature of the topotactic transformation and associated temperature regimes critical to the formation of active catalysts. The direct ECELL-HREM studies show that the structural transformation begins at ˜ 400°C, and a mixture of the precursor and pyrophosphate phases exists at ˜ 425°C. At 450°C, most of the conversion to VPO has taken place. These atomic-scale studies reveal no amorphous phases during the transformation, and that the atomic periodicity is maintained throughout. No other phases have so far been identified in the transformation. The direct studies are important in the development of selective catalysts.
Oxygen Related Defect Center Red Room Temperature Photoluminescence in as Made and Oxidized Porous Silicon
Authors: Prokes S. M. , Carlos W. E.
Published: April 2011

Since bulk silicon does not emit light in the visible part of the spectrum, the discovery of strong visible luminescence from porous silicon has been quite surprising and has generated significant interest. This material differs from bulk silicon in that it consists of interconnected silicon nanostructures, having very large surface to volume ratios. The first emission mechanism proposed involved carrier recombination within quantum size silicon particles, but more recent work has shown that surface emission models are more likely. In this paper, an interfacial oxygen center luminescence model will be discussed, with supporting experimental data. A direct correlation between the presence of these centers and the red photoluminescence in both as-made and oxidized PoSi will also be presented.
Substrate Surface Dependence of the Microstructure of μc-Si,Ge:H Deposited by Reactive Magnetron Sputtering (RMS)
Authors: Cho S. M. , Christensen K. , Wolfe D. , Ying H. , Lee D. R. , Lucovsky G. , Maher D. M.
Published: April 2011

We have investigated on the effect of different substrate surfaces in changing the microstructure of μc-SixGe1-x:H films prepared by reactive magnetron sputtering. Films were deposited on hydrogen terminated Si(111), Si(100) surfaces, and surfaces chemical and plasma oxides. The thin film microstructure was characterized by Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Raman scattering.
Nonlinear Optical Properties of CuS Nanocrystals with Modified Surface
Authors: Yumashev K. V. , Mikhailov V. P. , Malyarevich A. M. , Prokoshin P. V. , Gurin V. S. , Artemyev M. V.
Published: April 2011

Nonlinear bleaching and induced absorption effects in CuS microcrystals with modified (after oxidation) surface have been studied. Relaxation times of these processes demonstrate two components - fast (˜ 80 ps) and slow (>>500 ps). Energy level scheme for explanation of these phenomena was proposed. Appearance of bleaching effect in CuS microcrystals due to surface oxidation makes them as perspective materials for saturable absorbers for pico- and femtosecond lasers.
ZnS/Si/ZnS Quantum Well Structures for Visible Light Emission
Authors: Bretschneider Eric , Davydov Albert , McCreary Clint , Wang Li , Anderson Timothy J. , Maruska H. Paul , Norris Peter E. , Goepfert Ian , Moustakas Theodore D.
Published: April 2011

Silicon multiple quantum wells confined by ZnS barriers have been grown by MOCVD. Calculations indicate that well widths must be less than 15Å for visible light emission, basically independent of the band offsets. No near-infrared photoluminescence (except bulk Si band-edge emission) was observed from samples with 70Å or greater Si layers, using stimulation at 325 nm with a He-Cd laser; hole trapping in ZnS may play a role. However, we found evidence of yellow light emission from samples which possibly contain Si quantum dots embedded in ZnS.
Continuum Elastic Strain Effects at Semiconductor Interfaces
Authors: Pearsall T. P.
Published: April 2011

Heteroepitaxy of semiconductor materials has introduced whole new classes of electronic and optical devices as well as new physical phenomena. Heteroepitaxy always introduces stress in some or all of the deposited material. The resulting strain changes the bandgap of the materials in which it occurs, and changes the conduction and valence band offsets relative to neighboring materials. In all instances studied so far, the effects of strain can be calculated accurately using continuum stressstrain relationships developed for homogeneous, bulk materials.
Desorption and Segregation of Indium and its Dependence on Surface As-coverage
Authors: Ekenstedt M. J. , Yamaguchi H. , Horikoshi Y.
Published: April 2011

We investigate the desorption and segregation rates of Indium atoms on fully strained InxGal-xAs surfaces and their dependence on the surface As-coverage. The results are obtained by measuring the desorption of As using reflection high energy electron diffraction. The desorption rate of As is sensitive to the interaction energies between the group III atoms and the As-atoms. A change in the surface Indium-fraction results in a corresponding change in the desorption behavior of the As-atoms. Information of the surface alloy concentration can thus be obtained. Using this technique we find that segregation and desorption of Indium atoms on strained InxGa1-xAs surfaces is reduced for As-covered 2x4 reconstructed surfaces. The desorption rate of Indium is found to increase with the proximity to an inverted InAs/InxGalxAs interface. In contrast, the normal interface consisting of an InxGal-xAs layer grown on InAs is not seen to influence the desorption rate. This results is attributed to growth related defects specific for the inverted interface.
Surface Effects in Silicon Doping with Boron During Proximity Rapid Thermal Diffusion
Authors: Mone S. , Zagozdzon-Wosik W. , Rastogi M.
Published: April 2011

We investigated effects of surface preparation in doping silicon wafers using proximity rapid thermal diffusion (RTD). This process uses a spin-on-dopant (SOD) as an evaporating source for doping processed wafers. Various cleaning processes were used to study formation of the dopant glass on the silicon wafers during RTD. Doping was evaluated by sheet resistance measurements, dopant profiling using SIMS analyses, carrier distributions using spreading resistance profiling (SRP) or anodic oxidation, and was complemented by the composition analyses of the SOD deposited on the source wafers and of the dopant glass formed on the target wafers using Fourier Transform Infrared Spectroscopy (FTIR) in the transmission and reflection modes, respectively. It was found that the influence of the cleaning steps is much stronger in low temperature doping processes than at high temperatures. In addition, the temperature effect related to the wafer size was also an important factor in determining the doping efficiency in this RTDs.
Cathodoluminescence Study of Diffusion Length and surface Recombination Velocity in III-V Multiple Quantum Well Structures
Authors: Chao L.-L. , Freiler M. B. , Levy M. , Lin J.-L. , Cargill G. S. , Osgood R. M. , Mclane G. F.
Published: April 2011

We describe studies of luminescence and lateral transport properties of excited carriers in GaAs- AIGaAs multiple quantum well (MQW) structures by cathodoluminescence measurements in a scanning electron microscope. We examine the effect of in-plane, etch-defined feature size on MQW luminescence efficiency and variability, and determine the diffusion length and its temperature dependence from ˜ 8K to 250K. Our measurements also provide information about nonradiative surface recombination velocity at the side walls of etch-defined MQW structures.
Uniaxial Stress Applied To p-Type GaAs/AlGaAs Heterostructures: Influence on Heavy Hole Subbandsau
Authors: Hansen Ole P. , Olsen Janus S. , Kraak W. , Saffian B. , Minina N. , Savin A.
Published: April 2011

Quantum Hall effect and Shubnikov-de Haas oscillations in a 2D hole gas at a p-GaAs/Al0.5Ga0 5As (001) interface show, that under in-plane (110) uniaxial compression a redistribution of carriers between the two spin-splitted subbands of the ground heavy hole state takes place. At the maximal compression of 2.5 kbar the carrier density of the most populated subband is decreased by 18%, while the total carrier density remains almost unchanged. A decrease of the spin-splitting under the uniaxial compression is proposed.
Ge-Related Interfacial Defects in Sige Alloy Structures
Authors: Macfarlane Patricia J. , Zvanut M. E. , Carlos W. E. , Twigg M. E. , Thompson P. E.
Published: April 2011

This paper reports etching results supporting the identification of the SG1 center as a germanium dangling bond defect at the interface between an oxide and crystalline SiGe. The presence of this defect is significant because, like an analogous center in Si-based systems, it may alter the operation of any microelectronic or micro-optical device which incorporates an interface between SiGe and an overlying oxide. The samples examined are oxygen implanted SiGe layers in which the SG1 center is believed to occur at the interface between oxide precipitates and SiGe. Because of the center's apparent relation to the oxide precipitates distributed through layers of the sample, a depth profile assists in confirming the interfacial nature of the defect. We obtain a depth profile by comparing electron paramagnetic resonance (EPR) spectra of samples etched to decreasing thickness. EPR spectra indicate that the SG1 center decreases with depth in a manner that when correlated to a cross sectional transmission electron micrograph confirms the association with SiO2 and supports its location at the SiGe/SiO2 precipitate interface.
Stress Evolution in Ultra Thin Sputtered Films
Authors: Su Quanmin , Cammarata R. C. , Wuttig Manfred
Published: April 2011

The stress and microstructure of growing thin films evolve with time if the deposition is interrupted or terminated. To establish the parameters which control both kinetic processes ultra thin Au, Cu and Al layers were sputter deposited on Si membranes and the stress evolution was monitored by a vibrating membrane technique. The related surface morphology was studied by scanning tunneling microscopy. Aging after each deposition causes stress evolution towards higher tension and the evolution of the stress with time follows an exponential law with a characteristic relaxation time of the order of tens of seconds. This time was found to depend strongly on the accumulated film thickness as well as the surface morphology. The intrinsic stress of the growing layer increases with the coverage of the film on substrate. Scanning Tunneling Microscopy (STM) shows that the film grows in a Volmer-Weber (VW) mode and the stress reaches a maximum as the film become continuous.
Crystalline Structure and Morphology of the Phases in MgO, TiO2 and ZrO2 Prepared by the Sol-Gel Technique
Authors: Bokhimi  , Boldu J. L. , Muñoz E. , Novaro O. , Lopez T. , Gomez R.
Published: April 2011

The temperature evolution of the crystalline structure of the nanophases found in sol-gel MgO, TiO2 and ZrO2 systems was analyzed by performing x-ray powder diffraction. The structure and concentration of each phase was determined by using the Rietveld technique. The effect of doping MgO and TiO2 systems with platinum was also studied.
Real-time Optical Monitoring of GaxIn1−xP/GaP Heterostructures on Silicon
Authors: Dietz N. , Rossow U. , Aspnes D. E. , Sukidi N. , Bachmann K. J.
Published: April 2011

In this paper we report the combined application of p-polarized reflectance spectroscopy (PRS), reflectance difference spectroscopy (RDS), and laser light scattering (LLS) to investigate the heteroepitaxy of GaxIn 1−xP/GaP on Si by pulsed chemical beam epitaxy (PCBE) with tertiarybutylphosphine (TBP), triethylgallium (TEG), and trimethylindium (TMI) precursors. Both, PRS and RDS follow the growth process with submonolayer resolution utilizing a periodic fine structure signal, which is caused by a periodic alteration of thickness and composition of an ultra-thin surface reaction layer during the periodic TEG and TBP exposure of the surface. After the transition from GaP growth to GaxIn 1−xP growth, the RDS oscillations are reoriented after about five precursor cycles in a new oscillation periodicity, where the response to the TBP pulse has the opposite direction. The ratio of the changes in the amplitudes of RDS signals as a response to TEG and TMI surface exposure is used to estimate the composition fo GaxIn 1−xP. The PRS fine structure is maintained after switching to GaxIn 1−xP growth with a separate feature for each TEG and TMI surface exposure. The amplitude ratio of these features changes during growth.
Temperature Measurements Using In Thermocouple In The Mocvd Rotating Disk Reactors
Authors: Gurary A. I. , Stall R. A.
Published: April 2011

Rotating Disk Reactors used for Metalorganic Chemical Vapor Deposition have evolved into a leading manufacturing technology for several materials, including nitrides, compound semiconductors, metals, and oxides. One of the major issues to be resolved in bringing this technology into routine high yield manufacturing has been precise and repeatable wafer temperature measurement and control. The conventional approach to the rotating wafer temperature measurements by a stationary thermocouple located near the rotating wafer carrier suffers from low accuracy and repeatability. We have implemented a rotating thermocouple with a junction located close to the wafer for the temperature measurements in the MOCVD Rotating Disk Reactor. This approach allowed us to obtain reliable and accurate wafer temperature measurements with minimum dependence upon variable process parameters and to protect the thermocouple from degradation in the aggressive reactor environment. The temperature difference between wafer and thermocouple for the rotating and stationary thermocouple designs as a function of process parameters will be discussed.
Real-Time Monitoring Of GaAs(100) Etching By Surface Photoabsorption
Authors: Eng Joseph , Fang Hongbin , Su Chaochin , Vemuri Sujata , Herman Irving P. , Bent Brian E.
Published: April 2011

Surface photoabsorption (SPA) has been applied to monitor, in real time, the surface of GaAs(100) during chemical dry etching by a molecular beam of HCl. Changes in the HCl flux to the surface at a constant temperature (840 K) have been used to induce changes in the Ga:As ratio on the surface. These changes in surface stoichiometry have been detected in situ via SPA measurements of the transient fractional change in the reflectance of p-polarized, 488 nm light that is incident onto the surface near the pseudo-Brewster angle. On the basis of results from prior applications of SPA to the study the atomic layer deposition of GaAs, the changes in the SPA signal as a function of the etching parameters can be correlated with changes in the relative surface densities of Ga and As. The findings are confirmed by independent determinations of the changes in surface stoichiometry made by measuring the time-integrated difference in the fluxes of Ga- and As-containing etching products evolved from the surface as a function of the HC1 flux.
Afm Probe Tip and Image Reconstruction from Noisy Measurements
Authors: Fischer H. , Nittmann J.
Published: April 2011

We have tested the application of a recently developed probe tip reconstruction method to AFM images from semiconductor surfaces. The method by Villarrubia is the first to enable the construction of a probe tip from the AFM measurements alone. Here is a summary on how this method can be implemented. Experience shows that for some real surface data, experimental noise prevents the reconstruction of realistic tips. Therefore we present some preliminary results of how noise reduction methods applied to the measurements can provide access to more realistic tip shapes which are the basis for a useful image reconstruction.
AFM Analysis of ECR Dry-Etched Ingap, Alinp and Algap
Authors: Ren F. , Hobson W. S. , Lothian J. R. , Lopata J. , Caballero J. A. , Lee J. W. , Pearton S. J. , Cole M. W.
Published: April 2011

The etch rates of InGaP, AlInP and AlGaP increases dramatically with microwave power in ECR BCl3- or CH4/H2-based discharges, reaching values near 1μm·min−1at 1000W, The surface morphologies of these materials however behave much differently as the microwave power is increased. For BCl3 etching of InGaP the surface RMS roughness decreases from 36nm at 250W to 2nm at 1000W. For AlInP, there is little change in surface morphology, whereas for the common binary component of these two materials, InP, the surface becomes very rough at high powers (>60nm RMS). By contrast, the morphologies of the three ternaries remain smooth over a wide range of conditions with CH4/H2/Ar. The AFM analysis, coupled with AES enables us to understand these different responses in terms of volatility of the respective chloride, metalorganic and hydride etch products.
Response Time For Optical Emission And Mass Spectrometric Signals During Etching Of Heterostructures
Authors: Thomas S. , Chen H. H. , Pang S. W.
Published: April 2011

Plasma etching of III-V heterostructures has been monitored using optical emission spectroscopy and mass spectrometry. For the Ga optical emission signal at 417.2 nm, a response time as fast as 0.2 s has been measured. The response time of the mass spectrometer is limited by the transit time of etch products from the wafer surface to the ionizer. A minimum response time of 0.9 s was measured by reducing the signal integration time of the mass spectrometer. Saturation of the optical emission signal has been shown to be related to the residence time of etch gases by varying the flow rate or pressure. Decreasing residence time by reducing the pressure from 6 to 2 mTorr and maintaining a constant flow rate caused the Ga emission signal saturation time to decrease from 7 to 3 min. The 145ASC12+ signal saturated before the Ga emission signal at 417.2 nm. Endpoint detection for etching an AlInAs emitter and stopping on a GaInAs base was studied. By monitoring the changes in the Ga emission intensity, only 2 nm of the GaInAs base layer had been removed when the emitter etch was stopped.
Investigation of Passivation Effects in InP Hemt Layers
Authors: Hove M. Van , Finders J. , Zanden K. Van Der , Geurts J. , Rossum M. Van
Published: April 2011

We have investigated the influence of the deposition of a passivating silicon nitride layer on the electron transport in InAlAs/InGaAs/InAlAs quantum wells capped with a thin InGaAs layer. This structure is grown by Molecure Beam Epitaxy lattice-matched on InP substrates for the fabrication of High Electron Mobility Transistors. The InGaAs cap layer is added to reduce the ohmic contact resistance. In a first step to illuminate the complicated structural changes involved when passivating fully processed devices, we studied the influence of silicon nitride layer deposition on the virgin epilayers. The electrical transport properties were characterised by resistance, mobility, carrier concentration and magnetoresistance measurements, while Raman spectroscopy was used to probe the vibrational properties which are influenced by the free carriers. Because of the small penetration depth of the laser light mainly the lattice vibrations in the InGaAs ohmic contact layer were observed in the Raman spectra. Before passivation this thin highly doped cap layer is depleted, as confirmed by magnetoresistance measurements, that show a single conducting path in the two-dimensional electron gas formed in the InAlAs/InGaAs/InAlAs QW, and only bulk-like InGaAs phonons are observed in the cap layer. After passivation a shift to lower frequencies of the GaAs-like mode indicates a high electron concentration in the InGaAs cap. The results of the Raman analysis are in good agreement with the electrical transport data that show a considerably lower resistance after passivation. Magnetoresistance measurements on passivated layers confirmed the creation of an additional conducting path in the InGaAs cap layer introduced by the silicon nitride deposition process.
Optical And Mass Spectrometric Diagnostic Methods For Plasma Etching
Authors: Donnelly V. M.
Published: April 2011

Optical emission and line-of-sight mass spectrometry were used to monitor Cl, Cl2 and SiClx reaction products during etching of Si(100) in a high density (1–2 × 1011 ions/cm3) chlorine plasma. Emission from atomic Cl, and from ion-pair states of C12 at 7.2 – 9.4 eV were monitored, along with emission from a small amount of Xe that was added to the gas to sense changes in the electron energy distribution (i.e. actinometry). In this manner, the normalized emissions provide a measure of relative number densities of C12 and Cl. These measurements were converted into absolute numbers by extending the measurements to extremely low powers, where C12 and Xe number densities are known. These results are compared with those recorded with a differentially pumped, line-of-sight mass spectrometer. At power densities of ˜0.5 W/cm3, the discharge is almost completely dissociated in the plasma source region (˜90%), while above the wafer and downstream of the plasma, the percent consumption of Cl2 drops to 75%. A long term upward drift in the percent dissociation in the source was observed, attributable to a time-dependent decrease in the rate of Cl-atom recombination on the glass walls. These results are compared with recent model predictions and are also discussed in terms of their significance for surface etching reactions, and real-time control.
Electron Density Effects in the Modulation Spectroscopy of Strained and Lattice-Matched InGaAs/InAlAs/InP HEMTs.
Authors: Dimoulas A. , Davidow J. , Giapis K. P. , Georgakilas A. , Halkias G. , Kornelios N.
Published: April 2011

The effects of the channel electron density on the interband optical transitions of strained (x = 0.6 and 0.65) and lattice-matched (x = 0.53) lnxGa1−xAs/In0.52Al0.48As/InP high electron mobility transistor structures have been investigated by phototransmittance at room temperature. Analysis of the ground and first excited transitions for low and high densities, respectively, enabled a separate estimation of the electron densities occupying each one of the first two subbands. It was found necessary to include the modulation of the phase-space filling in the analysis of the spectra, especially for the samples with a high electron density, in which case this mechanism becomes dominant.