bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma chemistry in disilane discharges
Authors: Doyle J. R. , Doughty D. A. , Gallagher Alan
Published: July 2002

We have measured the initial silane and polysilane product yields from disilane decomposition in rf and dc discharges, at 25 and 250 °C and 20 Pa (0.15 Torr) pressure as typically used for a-Si:H film deposition. From analyses of these yields we conclude that the initial Si2H6 fragmentation pattern is SiH3+SiH2+H (91±9%) and H3SiSiH+2H (9±9%), that the primary product of the H+Si2H6 reaction is SiH4+SiH3, and that SiH3 is the dominant radical causing film growth. We have measured a radical-surface reaction probability of 0.34±0.03, very similar to that observed for SiH3 in SiH4 discharges. We report a spatial distribution of emission indicative of a γ-regime discharge. From deposition on glass fibers strung between the electrodes, we find that highly strained a-Si:H film is produced everywhere except on or near the electrodes, suggesting that energetic ion impact is necessary to yield useful films in disilane discharges.
Infrared observation of thermally activated oxide reduction within Al/SiOx/Si tunnel diodes
Authors: Brendel R. , Hezel R.
Published: July 2002

Electron-beam-evaporated aluminum/silicon oxide/silicon tunnel diodes with an initial oxide thickness of 1.3 nm have been annealed for up to 1 h at temperatures from 213 to 369 °C. They have been investigated by infrared grazing internal reflection (GIR) spectroscopy and current-voltage measurements. The measured IR spectra were analyzed by computer modeling. All spectral features could be explained self-consistently within a Al/AlOy/SiOx/Si layer model. In the as-deposited state less than 0.6 monolayers of Al—O bonds are formed at the Al/SiOx interface. A thermally activated reduction of the ultrathin oxide film by Al was observed. The changes in the current-voltage curves induced by slight annealing (1 min at 213 °C) are accompanied by changes in the insulator-bonding structure, which GIR is sensitive enough to detect.
Thin-film modeling for mechanical measurements: Should membranes be used or plates?
Authors: Fartash A. , Schuller Ivan K. , Grimsditch M.
Published: July 2002

The two limits for modeling vibrating thin films, viz as a plate or as a membrane, are discussed. In terms of these limits the sources of experimental uncertanties are identified and the advantages of using films which can be modeled as membranes are explained. The mathematical formalism for treating films as vibrating membranes is developed and relations for self-consistency checks are presented. The drive mechanisms used to generate vibrations in the films are also discussed.
Hopping charge transport in molecularly doped polymers: Polymer matrix dependence of the hole drift mobility
Authors: Kanemitsu Yoshihiko
Published: July 2002

Effects of the polymer matrix on the drift mobility of holes in polymers doped with 2-(p-dipropylaminophenyl)-4-(p-dimethylaminophenyl)-5-(o-chlorophenyl)-1, 3-oxazole were studied by means of time-of-flight photoconductivity measurements. The drift mobility at zero field, the activation energy for hopping, and the electric field dependence of the mobility strongly depend on the polymer composition. These polymer matrix dependence of the drift mobility are largely related to energetic disorder of hopping sites in binary solid solution.
Depth profiling of residual stress along interrupted test cuts in machined germanium crystals
Authors: Sparks R. G. , Paesler M. A.
Published: July 2002

Residual stress profiles in machined germanium have been determined by measuring the longitudinal optical phonon spectra using micro-Raman spectroscopy. Lateral spatial resolution of 1 μm results from this direct nondestructive technique. By measuring the Raman spectra with several probe wavelengths, axial resolution of 10 nm is obtained through differential absorption profiling (DAP). The stress field in these machined brittle semiconductors is characterized by a surface layer under compression, an abrupt compressive-to-tensile transition, and a deeper-lying region of tension which ultimately relaxes in the unstressed bulk. The abrupt transition is indicative of a change from plastic to elastic deformation. The DAP technique has been applied to interrupted test cuts in diamond-turned germanium to reveal that fractured regions of the machined surface possess higher tensile stress that occurs at shallower depths than unfractured regions. A qualitative mechanism of the machining process consistent with these residual stress data is presented.
The initial stages of the oxidation of titanium nitride
Authors: Tompkins Harland G.
Published: July 2002

During the study of the oxidation of titanium nitride, we previously identified an initiation period during which oxidation proceeded much more slowly than after the initiation period. In the present work, we measure the kinetics of oxidation during these initial stages. The film growth during this period is roughly an order of magnitude slower than during the ‘‘normal’’ oxidation. No correlation was observed between the amount of oxygen in the bulk of the TiN and the oxidation time/temperature. The film growth kinetics are parabolic with an activation energy of 38.6 kcal/mol.
Effect of carrier concentration on the properties of irradiation-induced defects in p-type indium phosphide grown by metalorganic chemical vapor deposition
Authors: Messenger S. R. , Walters R. J. , Summers G. P.
Published: July 2002

Deep-level transient spectroscopy has been used to monitor the effect of carrier concentration on the properties of radiation-induced defects in InP n+p mesa diodes grown by metalorganic chemical vapor deposition. The activation energy Ea for hole emission from H4 and H5 centers and the injection-enhanced annealing rate of H4 at 200 K have been measured as a function of carrier concentration NA over the range ∼1×1016– 4×1017 cm−3. The measured values of Ea decrease with increasing NA in a way that can be semi-quantitatively explained by a combination of the Frenkel–Poole effect and phonon-assisted tunneling produced by the electric field in the junction. The results suggest that hole emission from H4 and H5 centers takes place to maxima in different valence bands. The injection-enhanced annealing rate of H4 centers increases with increasing NA at low concentrations, but approaches a maximum value near NA ∼ 1017 cm−3, indicating a limiting dopant (Zn) concentration for impurity-enhanced defect annealing.
Schottky barrier height enhancement on n-In0.53Ga0.47As
Authors: Kordoš P. , Marso M. , Meyer R. , Lüth H.
Published: July 2002

Schottky barrier height enhancement on n-InGaAs is studied on structures with thin surface layers of different compositions. Counter-doped p+-InGaAs layers, as well as layers of n- and p-InP, n-GaAs, and n-InGaP of different thicknesses and dopant densities, respectively, were used to enhance the barrier. Titanium was used as a barrier metal to prepare Schottky diodes of different areas and the barrier height is analyzed by current-voltage measurements. It is observed that the barrier height enhancement by p+-InGaAs layers increases with the layer thickness and dopant density, respectively, and effective barrier heights up to 0.63–0.68 eV, i.e., higher values than previously reported, have been measured. The barrier height enhancement by counter-doped p+-InGaAs layers on n-InGaAs can be described by the two-carrier model. Schottky diodes with extremely low reverse current densities have been prepared, JR(1 V) =4.5×10−6 A/cm2. It is shown that lattice-matched InP surface layers can be used as an alternative to enhance the barrier height on n-InGaAs. The barrier height increases with the layer thickness up to φB=0.53–0.55 eV, i.e., up to values previously reported as barrier heights on thick n-InP. Additional barrier enhancement can be achieved by counter doping of the InP surface layer and barrier heights of 0.66 eV have been obtained by p-InP surface layers on n-InGaAs. On structures with barrier-enhanced n-GaAs layers, a remarkable decrease of the reverse current density is observed if the layer thickness is reduced to the critical layer thickness, but the barrier height is very low due to the small n-GaAs thickness. For structures with slightly lattice-mismatched n-InGaP layers (xGaP=0.11) measured barrier heights are similar to those for n-InP enhancement layers of the same thicknesses.
Degradation and subsequent healing by electromigration in Al-1 wt % Si thin films
Authors: Li Z. , Bauer C. L. , Mahajan S. , Milnes A. G.
Published: July 2002

Electrical resistance of Al-1 wt % Si thin-film conductors has been measured as a function of time t, temperature, and current polarity in order to investigate both generation and recovery of (microstructural) damage caused by electromigration. The fractional change of electrical resistance ΔR/R is characterized by three distinct stages: (i) undetectable ΔR/R during an incubation period τ; (ii) linear increase of ΔR/R with t−τ; and (iii) abrupt decrease of ΔR/R when polarity is reversed, followed by gradual resumption of the previous linear increase. Examination of the conductor surface during these three stages by scanning electron microscopy reveals: (i) undetectable microstructural damage; (ii) generation of (first) holes and (then) hillocks; and (iii) recovery followed by further generation of microstructural damage. Results are interpreted by (i) generation of stress σ in grain boundaries; (ii) formation of holes when σ exceeds a critical tensile stress σ+c and hillocks when σ exceeds a critical compressive stress σ−c (‖σ+c‖ < ‖σ−c‖), and (iii) interchange of tensile and compressive stress by polarity reversal. The last stage, in fact, represents superposition of a continuation of the linear increase (degradation) of ΔR/R due to the applied current and an exponential decrease (healing) of ΔR/R, characterized by τ, due to stress relaxation. In general, damage and subsequent healing by electromigration involve a delicate balance between applied current, time, and spatial distribution of (elastic) tensile and compressive stress, (anelastic) formation of holes, and (plastic) formation of hillocks, as dictated by the concomitant microstructure.
Lateral spreading of focused ion-beam-induced damage
Authors: Bever T. , Jäger-Waldau G. , Eckberg M. , Heyen E. T. , Lage H. , Wieck A. D. , Ploog K.
Published: July 2002

We study the lateral spreading of implantation-induced damage and measure the position dependence of the cathodoluminescence intensity of GaAs/AlAs heterostructures patterned by a focused Ga+ ion beam. Two luminescence lines, one from a buried AlGaAs/GaAs quantum well and the other from a deeper lying AlAs/GaAs short period superlattice are detected. Implantation doses in the range 1012–1015 cm−2 are investigated. We find that the lateral spreading of implantation induced damage considerably exceeds the implanted region in the case of the quantum well (50 nm below the surface), but is well limited to the implanted region in the case of the superlattice (250 nm below the surface). Micro-Raman measurements allow us to locally probe the degree of crystallinity at a certain point of the sample.
Resistance and structural stabilities of epitaxial CoSi2 films on (001) Si substrates
Authors: Hsia S. L. , Tan T. Y. , Smith P. , McGuire G. E.
Published: July 2002

The resistance and structural stabilities of the epitaxial CoSi2 films, grown on (001) Si substrates using sequentially deposited Ti-Co bimetallic layer source materials, have been investigated by further anneals under extended conditions. In contrast to reported polycrystalline silicide film cases, the epitaxial CoSi2 films are very stable under the additional rapid thermal annealing treatment at 1100 °C for times from 10 to 60 s. This means that such CoSi2 films are able to stand the further heat treatment required in the ultralarge-scale integration regime of Si integrated circuit fabrication. The quality of the further annealed films has been actually improved: The film resistivity has decreased to reach a value as low as 10 μΩ cm, and the film structure has become more perfect, e.g., the densities of antiphase domains and film-Si interface facets have been decreased. For technological applications, it is necessary to remove the Ti-Co-Si alloy layer formed concomitantly on top of the as-grown CoSi2 film. This has been accomplished by chemical etching using the standard buffered oxide etch solution. In the present experiment, as-grown epitaxial CoSi2 films with and without the Ti-Co-Si alloy top layers have been both included and the same film resistance and structural stabilities have been observed. Thus, the excellent resistance and structural thermal stabilities of the present CoSi2 films result from the single-crystal nature of the films and not the effect of the top Ti-Co-Si capping layer. Mechanisms responsible for the excellent quality of the epitaxial CoSi2 films, as well as for the unacceptable quality of the polycrystalline silicide films, have been discussed.
Thermally induced stacking faults distributed inhomogeneously in Czochralski silicon crystals
Authors: Shimura Fumio
Published: July 2002

Inhomogeneous but symmetrical distribution of bulk stacking faults in Czochralski silicon crystals has been attributed to the corresponding distribution of self-interstitials, which greatly depends on the crystal growth conditions. The inhomogeneous distribution of self-interstitials is not affected by the shape of the solid-melt interface, which greatly affects growth striations. Consequently, it has been proved that silicon self-interstitials depress oxygen precipitation and the growth of surface oxide layer in silicon.
Epitaxial silicon growth conditions and kinetics in low-temperature ArF excimer laser photochemical-vapor deposition from disilane
Authors: Fowler B. , Lian S. , Krishnan S. , Jung L. , Li C. , Samara D. , Manna I. , Banerjee S.
Published: July 2002

Homoepitaxial Si films were deposited using an ArF excimer laser beam parallel to the substrate to photodissociate Si2H6 at low temperatures (250–350 °C) under laser intensity and Si2H6 partial pressure conditions that result in low initial photofragment concentrations (< 1013 cm−3). Total pressure and flow conditions were chosen such that there is little secondary photolysis of the initial photofragments. The deposition yield of solid Si from photoexcited Si2H6 is estimated to be 0.20±0.04, indicating that in order for film growth to result solely from the primary products in ArF laser (193 nm) photolysis of Si2H6, a sticking coefficient ≥0.6 must be assigned to the dominant growth precursor. Growth rates vary linearly with laser intensity and Si2H6 partial pressure over a range of 1–15 mJ/cm2 pulse and 5–40 mTorr, respectively. Increasing the distance between the laser-beam axis and the silicon substrate results in a reduction of the growth rate that can be explained by gas-phase chemical reaction of the growth precursors as they diffuse to the substrate. Epitaxy is maintained for temperatures above the threshold for thermal decomposition of surface (SiH2)n chains at ∼250 °C, and for temperatures below the onset of Si2H6 pyrolysis and rapid thermal desorption of surface H2 at ∼350 °C.
Monte Carlo simulations of secondary electron emission from CsI, induced by 1–10 keV x rays and electrons
Authors: Akkerman A. , Gibrekhterman A. , Breskin A. , Chechik R.
Published: July 2002

A model for electron transport and emission in CsI is proposed. It is based on theoretically calculated microscopic cross sections for electron interaction with the nuclear and the electronic components of the solid. A Monte Carlo program based on this model was developed to simulate secondary electron emission induced by x rays and electrons in the energy range of 1 to 10 keV. The calculated secondary emission yields agree with existing experimental data. The model provides all necessary characteristics for the design of radiation detectors based on secondary electron emission. It can be expanded to higher incident energies and other alkali halides.
Characteristics of periodically domain-inverted LiTaO3
Authors: Mizuuchi Kiminori , Yamamoto Kazuhisa
Published: July 2002

A periodically domain-inverted structure in LiTaO3 has been fabricated for quasiphase-matched (QPM) second-harmonic generation (SHG). Uniform proton exchange is achieved with pyrophosphoric acid. Using this technique with a Ta mask followed by heat treatment, the periodically domain-inverted structure for quasiphase matching is realized over large areas. The effect of fabrication conditions on the domain-inverted profile is investigated to form a periodic structure having a considerable depth and a short inversion period. Consequently, a third-order QPM-SHG device can be fabricated by using this periodically domain-inverted structure and proton-exchanged waveguide. To investigate period regularity of the domain-inverted structure and nonlinearly of the inverted region, phasematching characteristics and conversion efficiency of this device are examined. The formation mechanism of the domain inversion is also discussed.
Charging damage to gate oxides in an O2 magnetron plasma
Authors: Fang Sychyi , McVittie James P.
Published: July 2002

A model is developed to explain how plasma etching/ashing can damage gate covered oxides via plasma nonuniformity. In addition, the role of antenna structure parameters on this damage is examined. Plasma nonuniformity leads to a local imbalance between electron and ion currents from the plasma. This imbalance of local particle currents from the plasma leads to gate charging and subsequent thin oxide degradation. This article discusses a sheath model for this charging where measurements of plasma potential nonuniformity are used to calculate the peak surface charging potential and subsequent thin oxide tunneling current. It is this oxide tunneling current that generates the surface states at the Si/SiO2 interface and the trapped charge in the oxide that degrades oxide yield and reliability. This model is applied to analyze oxide damage in an O2 magnetron plasma, via the simulation program with integrated circuits emphasis, Langmuir probe measurements, and antenna capacitor breakdown measurements. The oxide current derived from this model shows good agreement with experimental damage data of antenna capacitors. Finally, oxide damage is shown to depend on antenna structure parameters and is explained by this model.
Analysis of transmission in polytype interband tunneling heterostructures
Authors: Yang Rui Q. , Xu J. M.
Published: July 2002

In this work, based on a two-band k⋅P theory formulation, the transmission properties of polytype interband tunneling heterostructures are analyzed. The expressions for the continuity equation and the conservation of particle in the two-band picture of the interband tunneling are rigorously derived. A general and explicit relation between the quasibound state and the transmission resonance is established. Close-form analytical expressions for the transmission coefficient and the resonant condition are also derived. Our analysis provides reasonable explanations to all available experimental results in the polytype interband tunnel heterostructures, and insight to the design of the interband tunnel devices. In particular, the double quantum well structure is examined in detail for achieving strong resonances and multiple negative differential resistances.
Assessment of local variations in the coercivity of magneto-optical media
Authors: Bernacki Bruce E. , Wu Te-ho , Mansuripur M.
Published: July 2002

Locally varying deposition conditions and substrate characteristics of magneto-optic media may alter the domain nucleation, growth, and collapse mechanisms of the film. The use of a static tester and basic image processing equipment permits qualitative observations of anomalous domain nucleation, growth, and collapse phenomena. We present example images for a Co/Pt sample and several TbFeCo films that depict symmetrical domain expansion and collapse, directional preference for domain wall motion, domain collapse from submicroscopic domain remnants, and anomalous domain nucleation and expansion as a function of position on the sample.
Theory of anisotropy in strained superlattices
Authors: Victora R. H. , MacLaren J. M.
Published: July 2002

Expressions for the magnetic anisotropy energy of strained fcc, bcc, and simple cubic superlattices are obtained for the (100), (011), and (111) orientations. The theory is based on summing pair interactions using the potential (M⋅R)2, where M is the magnetization and R is the vector connecting the two atoms. The theory is shown to predict the orientation independence of the interface anisotropy in a system of Co/Pd superlattices, in agreement with experiment and detailed electronic structure calculation.
Effect of atomic hydrogen and oxygen on diamond growth
Authors: Sun Biwu , Zhang Xiaopin , Zhang Qinzhe , Lin Zhangda
Published: July 2002

High-resolution electron energy loss spectroscopy has been used to investigate the effect of atomic hydrogen and oxygen on diamond growth. For a totally desorbed diamond (100) surface, atomic hydrogen corrodes carbon atoms on the surface first, then saturates the dangling bonds of sp3 hybridized carbon atoms on the next layer of diamond surface. But for the monohydrogenated dimerized surface, atomic hydrogen opens the elongated surface C—C dimer bonds. Oxygen abstracts adsorbed hydrogen at low substrate temperature, and makes all of the adsorbed hydrogen become abstracted if the reaction time is long enough. But this desorbed surface differs from that by heating to 1300 °C. For diamond (111) facets, atomic deuterium first abstracts the hydrogen atoms adsorbed on (111) faces, and then replaces the hydrogen atoms adsorbed on {110} steps.
Investigation of the micromagnetic structure of cross-tie walls in permalloy
Authors: Ploessl R. , Chapman J. N. , Thompson A. M. , Zweck J. , Hoffmann H.
Published: July 2002

The modified differential phase contrast (MDPC) mode of Lorentz electron microscopy was used to study the micromagnetic structure of cross-tie walls in permalloy. The distribution of magnetic induction along these walls is characterized and studied in detail by vector mappings calculated from MDPC image pairs. The wall thickness of the cross-tie wall is determined by fitting the calculated image signal of an analytical function to the MDPC wall profiles. A pronounced dip in the wall width is found at the center of the vortex structure of the cross-tie wall. The results are compared to theoretical calculations by Nakatani, Uesaka, and Hayashi, Jpn. J. Appl. Phys. 28, 2485 (1989).
An oligosilane bridge model for the origin of the intense visible photoluminescence of porous silicon
Authors: Takeda Yasuhiko , Hyodo Shi-aki , Suzuki Noritomo , Motohiro Tomoyoshi , Hioki Tatsumi , Noda Shoji
Published: July 2002

Oligosilanes bridging microgaps between silicon microcrystallites were investigated as a possible model for the origin of the intense visible photoluminescence of porous silicon by means of the semiempirical molecular-orbital method. The incomplete structural relaxation of the oligosilane bridge after the photoexcitation was found to be a key factor to give the visible photoluminescence. The calculated structure-insensitive photoexcitation energy around 3.3 eV and the structure-sensitive light emission energy around 1.2–2.1 eV are consistent with the experimental evidence. The sufficient transition probabilities between the concerning electronic states support the high efficiency of photoluminescence. Durabiliy of the structure under the photoexcitation was also suggested. The model is valid even if the silicon microcrystallites are partly or thoroughly replaced by silicon oxides particles as is more realistic for the porous silicon exposed to the air.
Sectional structures and electrical properties of ultrathin NbN/MgO bilayers on Si(100)
Authors: Ishiguro Takashi , Matsushima Kazuo , Hamasaki Katsuyoshi
Published: July 2002

NbN/MgO bilayers deposited on Si(100) substrates by rf-sputtering were studied using cross-sectional transmission electron microscopy (XTEM). The XTEM results reveal that the 10-nm-thick MgO layer forms two layers of different structures, i.e., an amorphous layer (∼4 nm) and a highly (100) oriented polycrystalline layer (∼6 nm). We also found that the structure of MgO underlayers exhibits a strong effect on Tc of on-deposited NbN layers.
Pinning fields in amorphous materials
Authors: Polak Ch. , Sinnecker J. P. , Grössinger R. , Knobel M. , Sato Turtelli R. , Kuss C.
Published: July 2002

The stress and field dependence of the pinning field Hp of ribbons of the composition Fe73.5Cu1Nb3Si13.5B9 and Co73.5Cu1Nb3Si13.5B9 is compared with that of the coercivity HC. The similar character of HC(σ) and Hp(σ) indicates a strong correlation between these two properties. At higher external stresses HC(σ) and Hp(σ) depend on a premagnetizing procedure. This can be explained assuming a different domain structure.
Effects of platinum content and substrate bias on the structure and magnetic properties of CoCrPt/Cr thin films
Authors: Glijer Pawel , Sivertsen John M. , Judy Jack H.
Published: July 2002

The effects of the Pt content (0–40 at. %) and the developed dc substrate bias voltage (0 to −190 V) on the magnetic properties and structure of rf sputtered CoCrPt/Cr films with two different remanent magnetization-thickness products Mrδ (0.7 and 2.3 memu/cm2) were studied. It was demonstrated that a wide range of in-plane coercivities (500–3450 Oe) can be easily obtained in these films. The addition of Pt affected the magnetic properties of the films through changes of the lattice parameter, texture, and phase composition. A maximum in the in-plane coercivity exists for moderate amounts of Pt. The saturation magnetization decreased monotonically with increasing Pt content. rf substrate bias increased the in-plane coercivity and altered the character of the magnetic interactions through changes of the stress, texture and microstructure of the magnetic layer.
Electron-spin polarization in photoemission from thin AlxGa1−xAs
Authors: Maruyama T. , Garwin E. L. , Mair R. A. , Prepost R. , Smith J. S. , Walker J. D.
Published: July 2002

The polarization of photoemitted electrons from thin AlxGa1−xAs layers grown by molecular-beam epitaxy has been studied as a function of Al concentration by varying x in steps of 0.05 from 0.0 to 0.15. As the fraction x is increased, the wavelength dependence of the polarization shifts toward shorter wavelengths, permitting wavelength tuning of the region of maximum polarization. A maximum electron polarization of 42%–43% is obtained for AlxGa1−xAs samples with x≥0.05 while the maximum polarization of GaAs (x=0) samples reaches 49%. To investigate the lower polarization of AlxGa1−xAs, additional samples have been studied, including a short-period superlattice (GaAs)7 - (AlAs)1 .
Investigation of the oxide surface layer on fine iron particles
Authors: Huang Runsheng , Xiong Hongqi , Lu Qingyou , Hsia Yuanfu , Liu Rongchuan , Ji Rongfu , Lu Huaixian , Wang Lianwei , Xu Yuxiong , Fang Guosheng
Published: July 2002

The spin pinning in the oxide surface layer has been observed directly, and it is considered a possible reason why the oxide layer leads to the decrease of the specific saturation magnetization for fine iron particles. The pinning depth has been estimated by means of a Mössbauer effect under an applied field of 6 T in a thermal-cycle process. The Debye temperature of the oxide layer and the temperature dependence of f2/f1 have been obtained, where f1 and f2 are the Mössbauer recoilless fractions for the inner α-Fe core and the oxide layer, respectively. Furthermore, the estimation for the thickness of an oxide layer has been improved.
Characterization of Si–SiO2 interface states: Comparison between different charge pumping and capacitance techniques
Authors: Autran J. L. , Seigneur F. , Plossu C. , Balland B.
Published: July 2002

The three-level and spectroscopic charge pumping techniques, deep level transient spectroscopy and capacitance-voltage measurements are both used to determine the energy distribution of Si–SiO2 interface states on submicrometer metal–oxide–semiconductor field-effect transistors and metal–oxide–semiconductor capacitors. This study is a systematic comparative analysis between charge pumping techniques and capacitance measurements. The measurements have been performed on different structures (n- and p-type materials, low and high interface states densities) and the performances of each technique have been compared.
Phase formation and microstructure changes in tantalum thin films induced by bias sputtering
Authors: Catania Philippe , Roy Ronnen A. , Cuomo Jerome J.
Published: July 2002

The effects of argon-ion bombardment on the structure and properties of sputtered tantalum films have been studied. Applied substrate bias voltage was used to control the bombardment energy in a hollow-cathode-enhanced low-pressure magnetron sputtering system. The films were characterized by x-ray diffraction, electrical measurements, Rutherford backscattering spectrometry, and stress measurements. The findings concerning the effects of negative substrate bias on film resistivity and structure run counter to earlier work. In particular, as opposed to results found in many early studies, which primarily involved higher-pressure discharges, at zero bias voltage the films have low resistivity and contain the bcc phase. Increasing the bias to −100 V, increases the resistivity dramatically, and induces formation of β-Ta, with no significant change in film impurity levels. The difference from earlier work is attributed to the lower relative impurity flux, as well as more energetic substrate bombardment in low-pressure magnetron sputtering. Energetic substrate bombardment is clearly demonstrated by the high level of argon content in films deposited with no applied bias (2%). At very high bias voltage, argon incorporation increases dramatically and resistivity increases in the β phase. Additionally, a decrease in the compressive stress and change in preferred orientation occur. The results suggest that the formation of the β phase is not controlled by impurity effects, but by Ta forward scattering and related stress changes.
The effect of fluorine on the redistribution of boron in ion-implanted silicon
Authors: Krasnobaev L. Ya. , Omelyanovskaya N. M. , Makarov V. V.
Published: July 2002

The distributions of B atoms in samples previously implanted with F+ and Ne+ with doses of 1.2×1013 cm−2 and 1.5×1015 cm−2 before and after annealing were investigated by secondary ion mass spectrometry. After annealing at 900 °C, a strong dependence of B redistribution rate on F concentration was shown. The presence of F decreased B redistribution, while that of Ne (close to F in the periodic table, but inert) did not. When postimplantation annealing was carried out at 1000 °C, the B distribution did not depend on the type of the previously implanted ions. At this temperature F atoms exit the crystal. The experiment showed that the redistribution of B implanted in Si depended on the chemical activity of the impurity present in a crystal and on its concentration.
Mechanisms of amorphization in crystalline silicon
Authors: Battaglia A. , Campisano S. U.
Published: July 2002

The process of ion-beam-induced amorphization is studied for 600 keV Kr irradiations performed at different substrate temperatures and for different ion fluxes. In particular both the nucleation of the amorphous phase and the planar amorphization, from a pre-existing crystal-amorphous (c-a) interface, are explored. It is found that the amorphization kinetics depends on the substrate temperature and on the ion flux. A phenomenological model is proposed to explain the experimental data; the movement of the c-a interface is ascribed to the balance between two terms, amorphization and crystallization, both dependent upon flux and temperature. In this framework the proposed model can embody literature data concerning both the crystallization and amorphization processes and the onset of amorphous nucleation.
Nonstoichiometry and dopants related phenomena in low temperature GaAs grown by molecular beam epitaxy
Authors: Missous M. , O’Hagan S.
Published: July 2002

The growth of GaAs at low temperatures (LT GaAs) at or below 250 °C, under standard molecular beam epitaxy growth conditions usually results in a massive incorporation of excess As in the lattice which then totally dominates the electrical and optical characteristics of the as grown material resulting in almost electrically and optically inactive material (or at least defects controlled). We report on new phenomena associated with the growth of GaAs at 250 °C and we show data on highly electrically active doped material. The electro-optical properties of this material are literally undistinguishable from material grown at 580 °C. By careful control of the growth conditions, material in which total defect concentrations of less than 1017 cm−3, well below the huge 1020 cm−3 that is normally obtained in LT GaAs, can be achieved therefore demonstrating that high quality GaAs can in effect be grown at extremely low temperatures. The implications for such material are far reaching and these will be discussed in the light of these new results.
The effects of ion bombarding energy on the structure and properties of TiN films synthesized by dual ion beam sputtering
Authors: Li Wenzhi , He Xiaoming , Li Hengde
Published: July 2002

TiN films have been synthesized by dual ion beam sputtering (DIBS) deposition at the temperature below 100 °C. Ion bombardment influenced the metallographic morphology and crystalline orientation of TiN films. TiN film formed under N+ bombardment at low energy (<1 keV) consisted of fine crystal particles without texture. The film bombarded at 300 eV exhibited a hardness of 2750 kgf/mm2, which was an extremely high value for TiN films currently obtained by ion beam assisted deposition. The tribological tests demonstrated that TiN film synthesized by DIBS possessed good wear resistance.
Domain inversion in LiTaO3 using proton exchange followed by heat treatment
Authors: Mizuuchi Kiminori , Yamamoto Kazuhisa , Sato Hisanao
Published: July 2002

We report on fabrication of a first-order periodically domain-inverted structure in −Z-cut LiTaO3 using proton exchange followed by heat treatment. The expansion of the domain inversion width can be suppressed within the first-order intervals by shortening the heat-treatment time. To perform this suppression, we propose quick heat treatment, which features rapid rising rate and short soak time. This technique was used to study the formation process and the expansion characteristics of domain inversion during heat treatment. This produced a periodically domain-inverted structure with interval of 4 μm and depth of 1.8 μm over a 10 mm length in the LiTaO3. The potential for this structure was evaluated by examining the characteristics of a first-order quasi-phase-matched second-harmonic generation device with a proton-exchanged waveguide. We also discuss the nucleation and expansion of domain inversion, based on experimental studies.
High dose Cl implantation in ZnSe: Impurity incorporation and radiation damage
Authors: Yu Kin Man , Ager J. W. , Bourret E. D. , Walker J. , Walukiewicz W.
Published: July 2002

The structural characteristics of ZnSe thin films grown by organometallic vapor phase epitaxy and implanted heavily with Cl ions (5×1015 and 1×1016/cm2) were investigated using ion beam techniques, x-ray diffraction, and Raman spectroscopy. We have found that although the as-implanted ZnSe layers were severely damaged, no amorphous layer was formed with an implant dose as high as 1×1016 Cl ions/cm2. Crystalline damage in the ZnSe layers was not fully removed even after annealing at 700 °C for 10 s. Ion channeling reveals that after annealing over 50% of the Cl atoms sit substitutionally in the lattice and they are preferentially located in the Se site. However, a significant fraction of the substitutional Cl are found to be slightly displaced from the normal Se sites. The projected displacement was found to be ≊0.2 Å. Electrical measurements and Raman spectroscopy results suggest that a large concentration of Zn vacancies (VZn) are present in the annealed samples. We believe that the Cl displacement and the low conductivity in these samples are due to the formation of (ClSe−VZn) complexes.
Influence of Ni impurities at the Si-SiO2 interface on the metal-oxide-semiconductor characteristics
Authors: Honda Kouichirou , Nakanishi Toshiro
Published: July 2002

Behavior of Ni impurities at the Si-SiO2 interface of metal-oxide-semiconductor (MOS) was studied with electrical measurements and transmission electron microscopy. Ni impurities were introduced in silicon wafers by ion implantation to the doses of 1.0×1015 and 1.0×1014 cm−2, then the MOS capacitors were fabricated on these wafers. The Ni impurities either nucleated (1.0×1015 cm−2), or scattered uniformly (1.0×1014 cm−2) at the Si-SiO2 interface. The nucleated Ni precipitate is in a metallic B-NiSi2 phase, and penetrates the silicon oxide. The precipitate is thought to make a weak spot in the silicon oxide, where the electric field is strengthened. Uniformly scattered Ni impurities near the Si-SiO2 interface increase the surface state density because they combine with the small steps caused by ion implantation damage. The increase in the leakage current with the Si-SiO2 interface roughness can be semiquantitatively explained by averaging Fowler–Nordheim currents through the Si-SiO2 interface roughness.
Giant magnetoresistance with low saturation field in (NixCo100−x/Cu) multilayers
Authors: Bian X. , Ström-Olsen J. O. , Altounian Z. , Huai Y. , Cochrane R. W.
Published: July 2002

We have investigated giant magnetoresistance (GMR) in NixCo100−x/Cu multilayers for x in the range 20–100. The GMR at room temperature is greater than 12% for magnetic alloys with x near 80, where the magnetocrystalline anisotropy is small. The smallest saturation fields are found near x=60 in the region where the magnetostriction vanishes. This combination of large GMR and small saturation field results in large MR field sensitivities up to 0.16%/Oe at room temperature. In order to maximize these parameters, we have also studied the dependence of the MR on the magnetic layer thickness and the number of bilayers.
Visible photoluminescence in Si+-implanted silica glass
Authors: Shimizu-Iwayama Tsutomu , Fujita Katsunori , Nakao Setsuo , Saitoh Kazuo , Fujita Tetsuo , Itoh Noriaki
Published: July 2002

We have investigated visible photoluminescence excited by Ar-ion laser (488 nm, 2.54 eV) at room temperature from Si+-implanted silica glass, as-implanted and after subsequent annealing in vacuum. We found two visible luminescence bands: one peaked around 2.0 eV, observed in as-implanted specimens and annealed completely after heating to about 600 °C, the other peaked around 1.7 eV observed only after heating to about 1100 °C, the temperature at which Si segregates from SiOx. It was found that the 2.0 eV band anneals parallel to the E′ centers, as detected by electron spin resonance studies. It was also found that Raman lines around 520 cm−1, due to Si—Si bonds, grow and that interference patterns are induced by annealing Si+-implanted silica glass. Based on these studies, we ascribe the 2.0 eV band to the electron-hole recombination in Si-rich SiO2 and the 1.7 eV band to the electron-hole recombination in the interface between the Si nanocrystal and the SiO2 formed by segregation of crystalline Si from SiOx.
Structural properties of deuterated germanium nitrogen alloys
Authors: Vilcarromero J. , Marques F. C.
Published: July 2002

An infrared analysis of nonstoichiometric hydrogenated and deuterated germanium-nitrogen alloys is presented. The films were prepared by rf reactive sputtering of a c-Ge target in a gas mixture of Ar+N2+(H2 or D2). The isotopic effect was used to identify the absorption bands associated with the alloy elements bonded to hydrogen. Its infrared spectra pattern depends strongly on the preparation condition. Samples prepared in the 100–300 °C temperature range are stable, while those prepared at temperatures lower than 100 °C show spontaneous atmospheric contamination. In this case, the evolution of the infrared spectra with the atmosphere exposing time for hydrogenated and deuterated films was analyzed.
Magnetic and structural properties of CoNiPt(SiO2) alloy films for high-density longitudinal recording
Authors: Murayama Akihiro , Miyamura Masao , Kondoh Shinji
Published: July 2002

Magnetic and structural properties of sputtered CoNiPt(SiO2) alloy films have been studied for high-density longitudinal recording media. In-plane coercivity remarkably increases from 1400 to 2500 Oe with an increase of SiO2 content up to 4 at. % and coercive squareness S* slightly decreases from 0.90 to 0.87, while the perpendicular magnetic anisotropy is not changed significantly. Media noise is markedly reduced by the addition of SiO2. Si in the film is shown to be in the form of SiO2 by x-ray photoelectron spectroscopy. In x-ray diffraction, hcp-CoNiPt lattice is observed and the lattice constants of this hcp structure are expanded by the SiO2 addition. Relative integrated intensities of the diffraction peaks from (100) and (002) planes to (101) plane are not dependent on the SiO2 content, which indicates that the average orientation of the c axis of the hcp lattice is not influenced by the SiO2 addition. This agrees with the result that the perpendicular anisotropy is not significantly changed. From the transmission electron microscopy and high-resolution scanning electron microscopy analyses, grain size decreases with the SiO2 addition. Moreover, the outline and shape of crystal grains become sharper with the SiO2 addition of 2 at. % than those in pure CoNiPt. With the 4 at. % SiO2, clear separation among each crystal grain is observed. These changes of the grain structure by the SiO2 addition are attributed to the chemical segregation of the SiO2 at the grain boundary. It is concluded that the development of this grain separation is a major reason for remarkable increase in the coercivity and reduction of the media noise by the SiO2 addition.
Dynamic force microscopy in liquids
Authors: Dreier M. , Anselmetti D. , Richmond T. , Dammer U. , Güntherodt H.-J.
Published: July 2002

We applied dynamic force microscopy in a liquid environment to silanized and derivatized glass surfaces, InGaAs, as well as to biological materials such as hexagonally packed intermediate layers of deinococcus radiodurans. The vertical and lateral resolution were estimated to be <1 Å and 7–10 nm, respectively. Upon immersing the cantilever into water, the resonance frequency was found to be reduced by a factor of two and the Q factor was lowered to 20–30. The experimental working distance between sensor and sample was determined with approach curves indicating that the range of interaction in water is much shorter compared to air.
Gettering of copper by bulk stacking faults and punched-out dislocations in Czochralski-grown silicon
Authors: Shen B. , Sekiguchi T. , Jablonski J. , Sumino K.
Published: July 2002

The characteristics of Cu precipitation on various types of defects associated with oxygen precipitation in Czochralski-grown silicon are investigated by transmission electron microscopy and the electron-beam-induced-current technique. Specimens containing dominantly either punched-out dislocations or bulk stacking faults were intentionally contaminated with Cu at various temperatures and cooled at three different rates. Colonies of Cu precipitates developed irrespective of cooling rate, apparently originating from punched-out dislocations developed around oxygen precipitates. In heavily contaminated specimens cooled fast from the contamination temperature, Cu also precipitates on Frank partial dislocations bounding stacking faults. During slow cooling, precipitation of Cu takes place on Frank partials only in lightly contaminated specimens but never in heavily contaminated specimens. Cu precipitates in colonies are thermally more stable than those formed on Frank partials. It is concluded that punched-out dislocations are more favorable precipitation sites for Cu than Frank partials.
Ferromagnetic La0.6Pb0.4MnO3 thin films with giant magnetoresistance at 300 K
Authors: Manoharan S. Sundar , Vasanthacharya N. Y. , Hegde M. S. , Satyalakshmi K. M. , Prasad V. , Subramanyam S. V.
Published: July 2002

Highly textured, as-deposited La0.6Pb0.4MnO3 thin films have been grown on LaAlO3 by pulsed laser deposition. The films are ferromagnetic metals below 300 K. Giant negative magnetoresistance of over 40% is observed at 300 K at 6 T.
Theoretical investigation of wave-vector-dependent analytical and numerical formulations of the interband impact-ionization transition rate for electrons in bulk silicon and GaAs
Authors: Kolník Ján , Wang Yang , Oğuzman Ismail H. , Brennan Kevin F.
Published: July 2002

The electron interband impact-ionization rate for both silicon and gallium arsenide is calculated using an ensemble Monte Carlo simulation with the expressed purpose of comparing different formulations of the interband ionization transition rate. Specifically, three different treatments of the transition rate are examined: the traditional Keldysh formula, a new k-dependent analytical formulation first derived by W. Quade, E. Scholl, and M. Rudan [Solid State Electron. 36, 1493 (1993)], and a more exact, numerical method of Y. Wang and K. F. Brennan [J. Appl. Phys. 75, 313 (1994)]. Although the completely numerical formulation contains no adjustable parameters and as such provides a very reliable result, it is highly computationally intensive. Alternatively, the Keldysh formula, although inherently simple and computationally efficient, fails to include the k dependence as well as the details of the energy band structure. The k-dependent analytical formulation of Quade and co-workers overcomes the limitations of both of these models but at the expense of some new parameterization. It is found that the k-dependent analytical method of Quade and co-workers produces very similar results to those obtained with the completely numerical model for some quantities.

Specifically, both models predict that the effective threshold for impact ionization in GaAs and silicon is quite soft, that the majority of ionization events originate from the second conduction band in both materials, and that the transition rate is k dependent. Therefore, it is concluded that the k-dependent analytical model can qualitatively reproduce results similar to those obtained with the numerical model yet with far greater computational efficiency. Nevertheless, there exist some important drawbacks to the k-dependent analytical model of Quade and co-workers: These are that it does not accurately reproduce the quantum yield data for bulk silicon, it requires determination of a new parameter, related physically to the overlap integrals of the Bloch state which can only be adjusted by comparison to experiment, and fails to account for any wave-vector dependence of the overlap integrals. As such the transition rate may be overestimated at those points for which ‘‘near vertical,’’ small change in k, transitions occur.
Effect of plasma-surface interactions on the radial variation of H atom density in a hydrogen radio frequency discharge
Authors: Ganguly B. N. , Bletzinger P.
Published: July 2002

The effect of plasma surface interactions on the radial variation of H atom density has been measured in a low pressure pure H2 rf discharge by two-photon (electric quadrupole and magnetic dipole) allowed laser induced fluorescence using a standard reference cell. Measurements were made in the pressure range from 0.5 to 7 Torr and at a rf power of 35 W into the plasma. The influence of different electrode materials on the H atom density close to the electrode surface and in the discharge volume was measured. The data shows that the radial density distribution, under our discharge conditions, is primarily determined by the plasma-surface interactions and not by the discharge current uniformity (or nonuniformity). We have clearly demonstrated the ability of this measurement technique to monitor in situ, plasma induced surface property changes.