bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical vapor deposition and characterization of phosphorus nitride (P3N5) gate insulators for InP metal-insulator-semiconductor devices
Authors: Hirota Yukihiro , Kobayashi Takeshi
Published: February 2003

A new gate insulating film consisting of P3N5 was formed on an InP surface by a new chemical vapor deposition (CVD) technique. A suitable combination of reagents (PH3 and NH3) made P3N5 CVD feasible in an ambient free from oxygen and having excess phosphorus pressure. The new insulator revealed ohmic conduction with a resistivity as high as 104Ω cm. The breakdown field intensity increased up to 107V/cm at room temperature. The low frequency dielectric constant was 3.7 ε0. A very minor hysteresis was seen in the capacitance-voltage curves measured on P3N5- InP metal-insulator-semiconductor diode. The interface state density was reduced to 1012/cm2eV at an energy near the conduction band edge. Photoluminescence spectra were measured before and after CVD to determine the surface passivation effect.
An optical characterization of native oxides and thin thermal oxides on silicon
Authors: Philipp H. R. , Taft E. A.
Published: February 2003

Vacuum ultraviolet reflectance spectroscopy is used to characterize native oxides and thin thermal oxides on silicon. The reflectance of 0–50 Å thick layers of noncrystalline SiO2,SiOx(X∼1.5), SiO, and Si on crystalline Si substrates are calculated for the photon energy range 8.5–12 eV using known optical data for these materials. Reflectance data for native oxide growths and thin thermal oxides are compared to these curves calculated for the ellipsometrically measured layer thickness. Native oxides contain little, if any, SiO2 but can be fitted to curves for SiO or composite SiO-SiOX layers while thermal oxides are essentially all SiO2 exclusive of a thin interfacial layer ∼5 Å in thickness which may exist between Si and SiO2. The technique of vacuum ultraviolet spectroscopy which clearly delineates SiO2 from other silicon-oxygen materials such as SiOX and SiO is capable of extreme precision in the characterization of these layers.
CO2 laser annealing of silicon
Authors: Naukkarinen K. , Tuomi T. , Blomberg M. , Luomajärvi M. , Rauhala E.
Published: February 2003

Boron doped silicon crystals, amorphized by 15N or 121Sb-ion implantation, were annealed with 100-ns CO2 laser pulses. 4He-ion backscattering and channeling spectra, and sychrotron x-ray topographs of heavily doped (1019...1020 atoms/cm3) samples show an almost complete recrystallization at peak intensities of about 40 MW/cm2, caused at 10.6 μm mainly by free carrier absorption. At intensities of about 20–35 MW/cm2, a rapid increase of the reflectivity to almost 100% at 10.6 μm, and a corresponding decrease in the transmitted intensity was observed. Time resolved transmission and reflection measurements at 10.6 μm and reflection measurements at 0.6.3 μm revealed that a liquid layer was formed at the surface of the crystal. Samples doped with 5×1015 and 3×1016 atoms/cm3 were not fully recrystallized. To estimate the annealing threshold at different doping levels, the maximum surface temperature of the sample was calculated as a function of the laser intensity. The calculations are in agreement with the observations. According to ( p,γ) measurements, some nitrogen segregates to the surface or moves out of the sample. Damage produced on the doped bulk silicon by a CO2 laser pulse at intensities of 20...100 MW/cm2 is also shown.
Transient capacitance studies of an electron trap at E
c−E
T = 0.105 eV in phosphorus-doped silicon
Authors: Jellison G. E.
Published: February 2003

A new electron trap has been observed in electron-irradiated n-type silicon at Ec−ET = 0.105 eV using transient capacitance techniques. It is shown that this trap is related to another trap at Ec−ET = 0.172 eV and that one trap can be converted to the other by altering the voltage pulsing scheme across the p-n junction. In particular, the maximum transient capacitance response from the trap at Ec−ET = 0.105 eV occurs when the majority carrier pulse width (tw ) is smaller than some time constant (τw ) and when the time-between-pulses (tp ) is larger than another time constant (τp ). Emission time and capture cross-section measurements indicate that the trap at Ec−ET = 0.172 eV is closely related to the oxygen-vacancy defect (A center). It is believed that both these traps are different configurations of the same defect, the defect possibly being an impurity atom trapped by an A center.
Erratum: Limits of detection for condensation nuclei counters [J. Appl. Phys. 52, 3062 (1981)]
Authors: Carlon Hugh R.
Published: February 2003

This Communication is reprinted in its entirety because the text was disorganized in the original printing. Physical limits restrict the numbers of nuclei that can be detected by cloud chambers and condensation nuclei counters (CNC’s) to about 108–109/cm3. Thus larger numbers will not be detected even when supersaturation s reaches sufficient levels to activate them, e.g., s∼4.85 for Wilson’s ’’cloudlike’’ nuclei from starting temperatures near 0 °C. Recent evidence suggests that water vapor and moist air contain more than 109/cm3 of neutral molecular complexes (water clusters), which were the ’’nuclei’’ observed by Wilson. Thus their true populations cannot be determined by cloud chambers or CNC’s, but they can be inferred by their infrared absorption, suggesting the interesting possibility of an infrared cloud chamber.
Influence of microwave phase noise on Josephson voltage steps
Authors: Bava G. P. , Andreone D. , Bava E. , Godone A.
Published: February 2003

The influence of microwave phase noise on rf-induced constant voltage steps generated by the ac Josephson effect is studied. Different circuit models for the junction excitation are considered: dc and rf voltage generators, dc and rf current generators, dc current and rf voltage generators. The analysis has been carried out assuming a power and band limited phase noise modulation in the first two cases, while in the last one a white frequency modulation spectrum is required for a treatment based on the Fokker-Planck equation. Some experimental results are reported, in order to display the basic phenomenological behavior.
Silver sensitization of germanium selenide films
Authors: Venkatesan T. , Wilkens B. , Vincent S.
Published: February 2003

Silver sensitization kinetics of germanium selenide films have been studied as a function of the deposition angle of the films. An enhancement in the silver uptake has been found with increasing deposition angle with respect to the surface normal. Scanning electron microscope observations show deep voids with columnar structure in the higher-angle films. Backscattering measurements indicate silver reactions deep into these films. To account for the observed uptake enhancement, the ∼1000 Å columns of the 75° film must consist of smaller substructures. The kinetics of the silver reaction seems to be limited by the penetration times through the voids for the oblique films (60 and 75°) and by the in and/or out diffusion of the Ag and Ge, respectively, through the surface layer for the normal (0°) and near normal (45°) films. The Ag-Ge exchange process, with four silver atoms replacing one germanium atom, has been quantitatively confirmed by x-ray fluorescence measurements.
Comparison of Ar-, O-, and Cl-ion implant-damage gettering of gold from silicon using metal oxide silicon techniques
Authors: Nassibian A. G. , Golja B.
Published: February 2003

Ar-, O-, and Cl-ion implant-damage gettering of gold from silicon has been examined using metal oxide silicon (MOS) techniques. Silicon wafers were intentionally contaminated with gold and then the ion implantations were performed on the back surface of the wafer and the damaged layer subsequently annealed at 1050° for 60 min. All dosages were 1016 atoms/cm2. Comparison of generation lifetime and interface trap density between the variously implanted wafers and the gold-diffused wafer demonstrated the improvement achieved with implant-damage gettering. The relative order of merit for the ions was found to be Ar≳O≳Cl.
Temperature dependent barrier injection in transit time devices: Steady state
Authors: Mustafa M. , Ahmad S.
Published: February 2003

Importance of the incorporation of the temperature dependence in injection of the minority carriers in BARITT (Barrier Injection Transit Time) devices is described here. Exact computer calculation of the steady-state current-voltage characteristics of silicon BARITTs has been performed and the properties of the injection region are presented in terms of few useful parameters, namely the width of the injection region and the mobile carrier density at the injection plane. The plots of current and temperature dependences of these parameters are given in detail. With the help of these results, a more realistic design procedure can be had for BARITT devices, along with a better understanding of the observed steady-state and rf performances.
Minority-carrier diffusion lengths in amorphous silicon-based alloys
Authors: Hack M. , McGill J. , Czubatyj W. , Singh R. , Shur M. , Madan A.
Published: February 2003

In this paper, we present results of collection efficiency versus wavelength measurements on thick (⩾1 μm) amorphous silicon Schottky barrier photovoltaic devices illuminated through both the ohmic and Schottky contacts. These results enable us to infer the zero-field minority carrier diffusion length in amorphous silicon-based alloys by using an appropriate theoretical model. For intrinsic a-Si:H (hydrogen) films produced by the glow discharge of silane this was found to be ∼2,100 Å. Our novel approach of illuminating the devices through the ohmic contact ensures that the collection efficiency results are extremely sensitive to the minority carrier diffusion length, and we also compare this approach to surface photovoltage type experiments which we show can lead to overestimation of this quantity.
Correlation of electrical carrier and atomic profiles of Mg implants in GaAs
Authors: Yeo Y. K. , Park Y. S. , Pedrotti F. L. , Choe Byung Doo
Published: February 2003

A comparative study of secondary ion mass spectrometry (SIMS) atomic profiles and electrical carrier profiles by Hall measurements has been carried out for Mg-implanted GaAs. It has been found that as-implanted Mg profiles in GaAs do not follow simple Gaussian distributions, but can be fitted to type-IV Pearson distributions. For low dose, implanted Mg does not redistribute significantly during annealing at 750 °C, whereas for high dose, Mg is found to diffuse out substantially. In general, the electrical carrier profiles follow roughly the SIMS atomic profiles of annealed samples. It is believed that the outdiffusion of Mg is chiefly responsible for poor electrical activation efficiency at high doses.
Maximum power from a cycling working fluid
Authors: Salamon P. , Band Y. B. , Kafri O.
Published: February 2003

We consider the problem of obtaining maximum work from an arbitrary two degree of freedom working fluid coupled to a periodic source of pumped thermal energy f (t). The working fluid is also coupled to a heat bath of temperature Tex(t) by a conductor of conductance K. We assume that f (t) and Tex(t) are given functions of time which are piecewise continuous but are otherwise arbitrary. For periodic f (t) and Tex(t) we find that the available power is given by the variance of f+KTex over the period. Even with f 0, the result is interesting. It reduces to the Curzon–Ahlborn7 power for step function Tex(t). It also provides a measure of the power available from temperature fluctuations of the atmosphere.
Electron transverse velocity measurements in an intense relativistic electron beam diode
Authors: Davis H. A.
Published: February 2003

Techniques for making electron transverse velocity measurements on an intense electron beam using thick-target bremsstrahlung emission are presented. The procedure presented here differs from similar previous measurements using thick-target bremsstrahlung in that it allows both time and spatial resolution. Data from the study of a 2.1-MeV, 40-kA, 140-ns-long beam are presented. Measurements on this beam had a transverse velocity resolution of about 0.1 c. The temporal resolution was about 5 ns and the spatial resolution was 6 mm. Techniques used to determine the time-resolved radial current density profile are also presented.
Exchange anisotropy in Cu-Mn-Al alloy
Authors: Koga Shinji , Narita Kenji
Published: February 2003

The 44.7Cu-20.6Mn-34.7Al(at. %) alloy in the composition range between the Heusler phase and the κ phase exhibits remarkably constricted hysteresis loops and high coercive force after annealing at about 300 °C. It has been found that this alloy shows displaced hysteresis loops at room temperature when cooled down from 350 °C in a magnetic field and that the hysteresis loops shift along the magnetization axis, not along the field axis, when the alloy is cooled to 77 K in a magnetic field. Broad rounded maxima of magnetization are observed at about 250 °C for the sample quenched from 380 °C in thermomagnetic measurements. The characteristics of the magnetic behavior are similar to those reported for mictomagnetic alloys, e.g., Cu-Mn alloys. The high coercive forces and the displaced and constricted hysteresis loops observed in the 44.7Cu-20.6Mn-34.7Al alloy are supposed to be attributed to the exchange anisotropy interactions between the ferromagnetic domains of the Heusler phase and the antiferromagnetic Mn-rich domains.
The effect of Cu diffusion in a Cu2S/CdS heterojunction solar cell
Authors: Hsieh H. C.
Published: February 2003

The effect of copper diffusion from the p-Cu2S into the n-CdS region, due to heat treatment, in a Cu2S/CdS heterojunction photovoltaic cell is investigated, using the energy band diagram resulting from a modified Schottky barrier in the CdS and the solution of the one-dimensional Poisson’s equation with appropriately assumed boundary conditions and diffusion model of Gaussian profile for the Cu-acceptor concentration in the CdS. The variation of the short-circuit current density Jsc and that of the fill factor of the device with the copper-diffusion parameters ζ and LA are analyzed. Here ζ denotes the fraction of copper acceptors within the Cu2S region which has diffused into the n-CdS region and LA is the mean diffusion length of copper. It is shown that both Jsc and fill factor decrease with ζ while they increase with LA. The sample calculation, made for room-temperature operation of the device, indicates that the reduction in Jsc and fill factor can be appreciable if the amount of copper diffused is sufficient. This theoretical observation is consistent with some experimental results which have been reported elsewhere.
Image force effects in metal-oxide-semiconductor solar cells
Authors: Ojha V. N. , Bhatnagar P. K. , Dhariwal S. R. , Sharma K. K.
Published: February 2003

Image force effects have been shown to play an important role in deciding the current-voltage characteristics of the Metal-Oxide-Semiconductor (MOS) Solar Cell. Because of reduction in barrier height and the barrier width, the dark saturation current is increased, and thereby the open circuit voltage is greatly affected.
Proton damage effects on light emitting diodes
Authors: Rose B. H. , Barnes C. E.
Published: February 2003

We have studied the effects of 16-MeV proton irradiation on the performance of a variety of light emitting diodes (LED’s) emitting between 820 and 1300 nm. Total light output and current were measured at room temperature as a function of forward bias prior to and following a sequence of room temperature 16-MeV proton irradiations. Our results indicate that the relative amount of proton-induced degradation from one LED type to another is similar to that observed for neutron and gamma irradiations. More specifically, the most sensitive device is the amphoterically Si-doped GaAs LED which is characterized by a long preirradiation minority carrier lifetime. The most resistant LEDs are the high radiance GaAlAs (820 nm) and InGaAsP (1300 nm) LEDs. As in the case of Si devices, the degradation rate per irradiating particle fluence is significantly greater for proton irradiation of these LEDs than it is for neutron exposure. Neutron damage data presented herein indicate that the ratio of proton-to-neutron degradation rates can be as high as 100. Lifetime-damage constant products for constant current operation are calculated for each LED type and vary from 1.5×10−13 cm2/p for the InGaAsP LED to 1.1×10−10 cm2/p for the amphoterically Si-doped GaAs LED.
Generalized formula for curvature radius and layer stresses caused by thermal strain in semiconductor multilayer structures
Authors: Feng Zhe-chuan , Liu Hong-du
Published: February 2003

The generalized formulas have been derived for the curvature radius and layer stresses caused by thermal strain in semiconductor multilayer structure with different elastic moduli and growth temperatures. Several special forms and applications are given.
The role of deep-level centers and compensation in producing semi-insulating GaAs
Authors: Johnson E. J. , Kafalas J. A. , Davies R. W.
Published: February 2003

A mathematical model, involving a set of gap states, is considered for interpreting the unusual properties of semi-insulating GaAs. Although GaAs should be an extrinsic semiconductor at room temperature, often it has carrier concentrations and resistivities which are characteristic of pure intrinsic material, and the electrical properties can be surprisingly uniform. Such behavior is shown to arise if a deep donor level is located close to the center of the gap and if the deep donor concentration is comparable to a net shallow-level concentration (NA−ND) so that compensation exists. It is demonstrated that the present model yields good agreement with presently available experimental data.
Effect of laser irradiation on the electrical properties of polycrystalline p-InSb thin films
Authors: Srivastava G. P. , Tripathi K. N. , Sehgal N. K.
Published: February 2003

Polycrystalline thin films of p–Insb were irradiated with Q-switched Ruby laser. Hall coefficient and dc conductivity studies reveal that the irradiated films have lower value of free carrier concentration and higher values of Hall mobility.
Photovoltaic effect in gold-indium selenide Schottky barriers
Authors: Di Giulio M. , Micocci G. , Rizzo A. , Tepore A.
Published: February 2003

Photovoltaic effect has been extensively investigated in gold-indium selenide Schottky barriers, realized by vacuum evaporation of gold on freshly cleaved surfaces of indium selenide single crystals. Continuous and pulsed excitation has been used to determine the fundamental parameters governing the photovoltaic effect. A barrier height of 0.65 eV has been found from current-voltage (I-V) and capacitance-voltage (C-V) characteristics, and by means of the spectral dependence of the photoemission current. A diffusion length of about 10 μm and a lifetime of about 15 μsec of the minority carriers have been determined by measuring both the spectral response of the short-circuit current and the transient photocurrent decay. Finally, a photovoltaic efficiency for solar energy conversion of about 2% has been evaluated.
Wavelength modification of AlxGa1−xAs quantum well heterostructure lasers by layer interdiffusion
Authors: Camras M. D. , Holonyak N. , Burnham R. D. , Streifer W. , Scifres D. R. , Paoli T. L. , Lindström C.
Published: February 2003

Data are presented showing that thermal annealing (875–-900 °C) can be used to modify the wavelength of a photopumped, low threshold AlxGa1−xAs quantum well heterostructure (QWH) laser from ∼8200 to ∼7300 Å with a threshold change from 150 to 1700 W/cm2. The energy levels of the annealed single quantum well crystal are approximated by fitting a modified Pöschl–Teller potential to the band-edge profile as modified by layer (Al–Ga) interdiffusion. The layer (Al–Ga) interdiffusion coefficient (at 875 °C) is found to be smaller, by a factor of 3–4, than previously reported. We suggest that this is due to the high quality, i.e., low defect density, of the ultralow threshold QWH crystals of this work.
Frequency domain analysis of entropy generation through heat flow
Authors: Leclercq D. , Gaviot E. , Thery P.
Published: February 2003

This paper proposes a new method for analyzing the entropy generation through heat flow in the frequency domain and its application for thermal insulation system optimization under unsteady state conditions. The bulk of the paper is devoted to demonstrating the general applicability of the frequency domain analysis for optimum design of thermal insulation composite slabs. In the typical experimental configuration, the rate of incident entropy flow is accounted for by the rate of entropy generation in the slab. For impressed heat flow, it is apparent that optimum insulation design does induce a large rate of entropy flow; that is, it does have maximum input thermal impedance. The theoretical formulation was limited to the optimum design of ‘‘double layers’’ insulation slabs. It is shown that the frequency dependence of insulation properties strongly varies with the relative layers’ positions when unsteady heating is used. This difference in the thermal insulation properties will clearly appear when comparing the rate of entropy flow entering the composite slabs. Both the theoretical and experimental results show the general interest of the frequency domain analysis of heat transfer. For nonsinusoidal thermal signals, it is shown that there are three steps in calculating the rate of entropy flow entering the insulation system, i.e., (1) resolve the impressed heat flow into a series of simple sinusoidal components, (2) calculate the entropy flow for each component, and (3) add the entropy flows for each separated component.
Quantitative model for current-voltage characteristics of metal point contacts on silicon rectifying junctions
Authors: Marchand J. J. , Truong Van Khiem
Published: February 2003

Metal point contacts on semiconductors result in rectifying contacts whose current-voltage characteristics do not obey the Schottky diode formula. However, the curves under loads varying from 20 to 100 g have been found to be described by a constriction resistance in series with a rectifying device whose law is of the form I=I0 (exp αV−1). The α exponent varies with load and would correspond, as compared to a Schottky diode, to high values of the idealization factor. A brief synthesis of the existing surface mechanic models shows that the real area of contact Ar must be proportional to the load. This is checked with the classical formulation for constriction resistances and so we obtain the measure of Ar . These results allow us to conclude that the deformations of silicon at the interface are mostly plastic. A great number of dislocations appear and cause the existence of many traps which are responsible for a tunneling effect through the metal–semiconductor barrier. This enables us to explain the low values of α and to determine the barrier height. Furthermore, we obtain the formula relating α and I0 to Ar and a plot of Ar versus the load agrees well with the mechanical theory.
Temperature dependence of structural and electrical properties of Ta-Si thin alloy films
Authors: Tien T. , Ottaviani G. , Tu K. N.
Published: February 2003

I n situ electrical resistivity measurement and structural analysis methods including MeV 4He+ ion backscattering, x-ray diffraction, Auger electron spectroscopy combined with Ar+ sputtering, scanning and transmission electron microscopies have been used to investigate the properties and characteristics of the Ta-Si thin alloy film system as a function of temperature. Stoichiometric TaSi2 films were deposited by double electron-gun coevaporation on Si, oxidized Si, and sapphire substrates. A distinct drop in resistivity near 300 °C has been determined to be a transformation of the amorphous to crystalline phase. The kinetics of the transformation has been obtained by isothermal treatment over the temperature interval of 240–280 °C. The results are interpreted in terms of a classical solid-state phase transformation model with a t4 (time) dependence and an apparent activation energy of 1.85 eV. Subsequent annealing causes further decrease of resistivity. The microstructures of films at various stages of annealing have been studied by x-ray diffraction and transmission electron microscopy. Correlation between the resistivity and microstructure is given and discussed. In situ resistivity of annealed films below room temperature has been measured. Crystalline TaSi2 thin films do not become superconductive at 1.5 °K. Ion-beam mixed, coevaporated TaSi2 film and films varying in composition from TaSi3.4 to TaSi1.2 prepared by cosputtering have also been studied. The results are compared and discussed.
Boron, fluorine, and carrier profiles for B and BF2 implants into crystalline and amorphous Si
Authors: Wilson R. G.
Published: February 2003

Depth distributions, measured by secondary ion mass spectrometry (SIMS), and carrier profiles, measured by differential capacitance-voltage (C-V) profiling, of boron and fluorine implanted as B, F, BF, or BF2 ions into random and channeling orientations of crystalline silicon, and into silicon amorphized by silicon ion implantation are reported. Low boron energies of 8 and 10 keV and the corresponding energies of 36 and 45 keV for BF2 ions are emphasized because of their use for high resolution device and circuit applications in silicon and silicon-on-sapphire. Amorphizing crystalline silicon prior to boron implantation eliminates the significant channeling tails on 8- or 10-keV boron profiles. Fluorine penetrates more deeply into crystalline silicon than boron does. Both boron and fluorine redistribute during annealing at 925 °C/20 min for B, F, BF, or BF2 implants, but with quite different characteristics as illustrated, and depend on the implantation fluence (5×1014 and 2×1015 cm−2 reported here). The fluorine redistribution profiles are strongly influenced by the magnitude and distribution of damage that remains after annealing. Fair agreement is shown between boron atom depth distributions measured by SIMS and C-V electrical profiles measured for a fluence of 1.5×1012 cm−2. Differential C-V profiles indicate that the entire ion spectrum from BF3 can be implanted and electrically activated (for a fluence of 1.5×1012 cm−2), as can a BF2 implant. Implantation through a 20-nm layer of SiO2 has no significant effect on the boron depth distribution in crystalline silicon. Pearson IV moments are given for the low energy boron profiles. The use of these profiles for modeling calculations is discussed. The suprem model of an exponential for the channeling tail of boron implants in crystalline silicon is fairly good for fluences greater than about 1015 cm−2, but poorer for lower fluences, but the slope and matching to the random portion of the profiles are difficult to predict. In order for modeling calculations to reasonably represent boron profiles, either the silicon substrate should be amorphized prior to boron implantation, or the modeling should be modified to use experimental data measured for the implant and silicon conditions.
Measurements of the energy deposition profiles of an intense light ion beam in target using neutron time-of-flight
Authors: Ozaki T. , Miyamoto S. , Ogawa F. , Yoshinouchi A. , Imasaki K. , Nakai S. , Yamanaka C.
Published: February 2003

A new diagnostic method for target deposition profiles of light ion beams is described. The deposition profile can be determined from the incident deuteron and the D-D reaction neutron energy distributions. Plasma effects on beam deposition profiles in high-temperature targets can be investigated by applying this method to focused beam-target experiments.
Characterization of a hybrid plasma and its application to a chemical synthesis
Authors: Yoshida Toyonobu , Tani Toshihiko , Nishimura Hirobumi , Akashi Kazuo
Published: February 2003

A numerical model has been developed for predicting the two-dimensional flow and temperature fields in a hybrid plasma which is characterized by the superposition of an rf plasma and an arc jet. Calculations have been made for the confirmation of a prominent feature of the hybrid plasma. As might be expected, the derived results suggested that the hybrid plasma has a possibility to offer higher efficiencies for practical processing than other conventional plasmas. Particularly noteworthy is the disappearance of a recirculation eddy found in a usual rf plasma, by the presence of the high velocity and high-temperature channel caused by an arc jet flow. Moreover, the relative insensitive character of the exit gas enthalpy to the rf input power was found. Based on the theoretical investigations, a reactor was designed to confirm the effectiveness of the hybrid plasma for chemical syntheses. Using the reactor, ultrafine amorphous Si3N4 with the nitrogen content of 37±0.5 wt. % and the size of 10–30 nm, which can meet the purity and size requirements of an ideal Si3N4 powder, could be prepared successfully by a reaction of SiCl4 and NH3. These theoretical and experimental investigations confirmed that the hybrid plasma torch is an effective reactor for the preparation of ultrafine refractory compounds by plasma chemical vapor deposition (CVD) processes.
High energy ion implantation effects in silicon
Authors: Byrne P. F.
Published: February 2003

A model is proposed for a new damage creation mechanism in a silicon crystal during ion implantation when the incoming ion has a very high energy. This damage is created through scattering by electrons as opposed to the screened coulomb scattering by the incoming ion which accounts for conventional damage creation. The model is based on relativistic kinematics and the threshold energies for the damage created in this manner are compared with other high energy effects for a standard set of dopant atoms. This damage mechanism is shown to not constitute a problem for envisioned device applications of high energy ion implantation.
Diffusion of beryllium into GaAs during liquid phase epitaxial growth of p-Ga0.2Al0.8As
Authors: Masu Kazuya , Konagai Makoto , Takahashi Kiyoshi
Published: February 2003

The diffusion of beryllium and zinc into GaAs substrates during liquid phase epitaxial growth of p-Ga0.2Al0.8As layers was investigated. The diffusion coefficients were determined from the profile of free-carrier concentration in the p-GaAs region. Comparing the diffusion coefficients of Be and Zn, the diffusion coefficient of Be was found to be about ten times higher than that of Zn in the temperature range above 750 °C. For Be diffusion, if the surface free-carrier concentration in the p-GaAs layer is lower than about 6×1018 cm−3, the diffusion can be expressed as diffusion from a semi-infinite source and the free-carrier concentration profiles are represented by the error function complements. With regard to temperature dependence, the diffusion coefficient takes the form D=D0 exp(−E0/kT), where D0=0.66 cm2 s−1 and E0=2.43 eV in the temperature range 700–900 °C. If the surface free-carrier concentration was higher than about 6×1018 cm−3, anomalous behavior was observed; i.e., the diffusion could be no longer represented by a constant diffusion coefficient.
Preparation of doped amorphous silicon films by ionized-cluster beam deposition
Authors: Yamada I. , Nagai I. , Horie M. , Takagi T.
Published: February 2003

Hydrogenated amorphous silicon alloy films were formed by ionized-cluster beam deposition of silicon in relatively low gas pressure of hydrogen, in a range of 10−5–10−4 Torr. Films with optical band gap of 1.3–1.9 eV could be formed. Effective hydrogenation seems to be due to the enhanced adatom migration effect and to the kinetic and the ionic charge effects of the clusters which are characteristics of the ionized cluster beam deposition. For doped film deposition, hydrogen gas mixed with phosphine or diborane was used. By this method, pure n- and p-type films could be reproducibly formed at practical deposition rates by changing gas flow into the deposition chamber. The deposited films have good adhesion and show smooth surface and thermally stable characteristics. The p-i-n diodes formed by this method showed good performance.
10-μm samarium based quantum counter
Authors: Krasutsky N. J.
Published: February 2003

Quantum counter action has been demonstrated at 10 μm. A LaBr3:Sm crystal shows a detectivity of 6.7×107 cm Hz1/2/W in the 9.6–10.3 μm region. The same crystal system is also sensitive to infrared radiation in several other bands between 2 and 10 μ. The relative sensitivity for different wavelengths is in agreement with the absorption strengths of the samarium transitions involved. By using a single laser pump line but switching input filters this multicolor sensitivity was used to determine the temperature of the blackbody target used. At very high pump powers there is a large increase in fluorescence output. This output is the result of a ‘‘photon avalanche’’ effect similar to that recently discovered in LaBr3:Pr. The slow buildup and rapid decay of this output provides strong evidence that a multi-ion process is involved.
Surface restoration of oxygen-implanted silicon
Authors: Kim M. J. , Brown D. M. , Garfinkel M.
Published: February 2003

The effects of oxygen implantation and annealing conditions on surface crystal restoration were studied as a function of temperature, by means of infrared spectroscopy, ultraviolet reflectance, electron microscopy, and secondary ion mass spectroscopy analysis. The oxygen interstitial absorption band shifts from 1020 to 1100 cm−1 with annealing temperature, and, the structure of the buried oxide changes with annealing condition. The restoration process is enhanced by defects formed during implantation. The binding energy of the oxygen-vacancy complex was found to be (0.48±0.03) eV from kinetic analysis. Low-temperature implanation combined with a long-term single-stage annealing is found to be suitable for good surface restoration.
Langmuir probe characteristic modulated with random fluctuations
Authors: Matsumoto Kazunori , Sato Masumi
Published: February 2003

Distortion of the Langmuir probe characteristic due to random fluctuations is investigated theoretically and experimentally. A statistical method is newly introduced to reasonably take account of the effects of statistically random processes. When the fluctuations in the plasma parameters and the current flowing to a Langmuir probe are ergodic, the time-averaged probe current is obtained by taking an ensemble average of the probe current weighted by the probability density function of fluctuating parameters. Therefore, the analysis is valid only for fluctuation spectra with frequencies small compared with the ion plasma frequency. Calculations are made for the distortion of the electron probe current due to Gaussian or periodic fluctuations in number density, space potential, and electron temperature. Previous results based on the usual time average can be deduced from the statistical method as special cases. The method is also examined experimentally by applying broadband Gaussian or periodic potential fluctuations to the plasma of a mercury discharge tube. It is found that Gaussian fluctuations in the plasma parameters bring about greater distortion to the electron probe characteristic than periodic ones, such as sinusoidal, rectangular, triangular waves.
Energy band-gap shift with elastic strain in GaxIn1−xP epitaxial layers on (001) GaAs substrates
Authors: Asai Hiromitsu , Oe Kunishige
Published: February 2003

It is demonstrated that the energy band gap in epitaxial layers is changed by biaxial elastic strains which are produced by lattice mismatches in heterostructures. The epitaxial layers used in this work were Gax In1−xP layers grown on (001) GaAs substrates by liquid phase epitaxy. The energy band-gap shifts were determined by comparing the photoluminescence peak energies of the as-grown GaxIn1−xP layers with those from free-standing layers removed from the GaAs substrates. It was experimentally found that the energy band gap shifts linearly with the elastic strain in the layer. Assuming that the lattice mismatch was accommodated only by the elastic distortion, the energy band-gap shifts in Ga0.5In0.5P alloys were also calculated. The calculated results are 6.0 eV or 4.9×10−12 eV/dyn cm−2 per unit strain or stress, respectively, for the [100] and [010] biaxial elastic stress. These values are in quite good agreement with the experimental results.
Effect of phosphorus doping on stress in silicon and polycrystalline silicon
Authors: Murarka S. P. , Retajczyk T. F.
Published: February 2003

An investigation of the polysilicon stress properties as a function of film thicknesses and phosphorus doping showed that as-deposited films are moderately compressive, and become less compressive with increasing film thickness. High temperature PBr3 diffusion in silicon produces wafer bending corresponding to a tensile stress in wafer. Following a PBr3 diffusion, polysilicon films, however, become less compressive. Subsequent oxidation introduces an additional compressive stress component of the order of 2−3×109 dyne/cm2 for oxidation temperatures between ∼900−1000 °C. The thermal expansion coefficients were similar for doped and undoped films (α∼2.9 ppm/°C) and slightly less than for 〈100〉 silicon, while the doped films were found to be less stiff than undoped ones but both were less stiff than 〈100〉 silicon. The observed changes in polysilicon stress due to film thickness and phosphorus doping have been interpreted in terms of a grain growth model wherein those factors which lead to enhanced grain growth also result in reduced compressive stresses.
Some maximal thermodynamic efficiencies for the conversion of blackbody radiation
Authors: Landsberg P. T.
Published: February 2003

Two efficiency formulas are derived for the conversion of blackbody radiation and their relationship is briefly discussed. It enables one to give an analytical expression for the entropy generation rate, obtained previously by microscopic considerations.
Ice crystal morphology and growth rates at low supersaturations and high temperatures
Authors: Colbeck S. C.
Published: February 2003

At an excess vapor density (supersaturation of about 10−4) adjacent to the ice crystal surface of 5–6×10−10 g/cc, there is a transition between the highly faceted kinetic growth form and the rounded equilibrium form at temperatures above –6 °C. At lower temperatures there is a transition in the equilibrium form to hexagonal prisms because of a reduction in the disordered surface layer. The growth rate of ice crystals from the vapor is analyzed by a simple model which accounts for vapor flow and surface processes separately. The conditions for highly temperature sensitive growth are identified from the model.
An analysis of the process of recrystallization of silicon thin films with either a scanning laser or strip heater
Authors: Cline H. E.
Published: February 2003

An analysis of the temperature, stress distribution, and crystal growth was made to model the process of recrystallization of silicon thin films with either a scanning laser or strip heater. The temperature distribution of a wafer with one or more thin film layers was calculated using both Green’s function and Fourier series methods. With increasing velocity, the temperature profile becomes asymmetric and the maximum temperature decreases. Heat flow is influenced by the applied heat profile, the layer thicknesses, thermal properties, heat transfer coefficient between the wafer and substrate, and the velocity of the heat zone. If the heat zone is wider than the wafer thickness the temperature profile may be approximated using a one-dimensional model. Thermal stresses are generated by either a nonuniform temperature or differential thermal expansion between layers. Temperature differences along the film that are greater than 10 °C may plastically deform the silicon film. To crystallize cell-free single-crystal thin films a critical ratio of the thermal gradient to the solidification velocity must be exceeded. The criterion for the crystallization of defect-free material is derived in terms of the solidification rate, heat transfer, and stability of the planar solid-liquid interface during crystal growth. It is predicted that defect-free silicon films are possible at rates below 0.005 cm/sec from a comparison with conventional growth of silicon single crystals.
Influence of dioxygen on the junction properties of metallophthalocyanine based devices
Authors: Martin Michel , André Jean-Jacques , Simon Jacques
Published: February 2003

The electrical properties of Au/PcZn/M devices are studied both in the dark and under illumination. The nature of the semitransparent metallic electrode M is varied. When the sandwiches are made and studied entirely under vacuum (10−7–10−8 Torr), no rectifying effect is observed in the dark and the open circuit voltage under illumination (Voc) shows no correlation with the work function of M. On the contrary, when the organic layer is exposed to air, a strong rectifying effect is found and Voc seems to be correlated with the work function of the semitransparent metallic electrode. A chemical scheme is proposed to rationalize these results.
Incorporation rates of gallium and aluminum on GaAs during molecular beam epitaxy at high substrate temperatures
Authors: Fischer R. , Klem J. , Drummond T. J. , Thorne R. E. , Kopp W. , Morkoç H. , Cho A. Y.
Published: February 2003

Gallium arsenide, aluminum arsenide, and aluminum gallium arsenide epitaxial layers were grown by molecular beam epitaxy in the substrate temperature range 590–720 °C. The incorporation rates of Ga and Al in this temperature range were studied by means of thickness measurements. The growth rates of GaAs and AlxGa1−xAs were observed to be dependent on growth temperature above 640 °C while the AlAs growth rate was observed to be independent of growth temperature in the range investigated. The reduction of the GaAs growth rate at a growth temperature above 640 °C was found to be lessened by the presence of minute amounts of Al and excess As. For the fixed Ga flux and a growth temperature of 700 °C the GaAs growth rate and the Ga contribution to the growth rate of Al0.3Ga0.7As were 0.50 and 0.89 times their low temperature values, respectively, while at 680 °C these values were 0.88 and 0.99, respectively.
Magnetic properties of amorphous Co and Ni alloys
Authors: Buschow K. H. J.
Published: February 2003

The magnetic properties of amorphous alloys of the type Mg1−xNix, Zr1−xNix, Hf1−xCox, and Nb1−xCox were studied in the temperature range 4.2–300 K. The saturation moments in these alloys and other Co-base amorphous alloys were analyzed in terms of a model proposed earlier, where account is taken of the size difference of the constituent metal atoms and the presence of compositional short-range ordering. It is shown that an additional moment reduction can be expected in amorphous alloys in which the 3d metal is combined with Ti, Nb, Ta, W, or Mo.
Palladium- and platinum-related levels in silicon: Effect of a hydrogen plasma
Authors: Pearton S. J. , Haller E. E.
Published: February 2003

The neutralization of deep-level centers associated with palladium and platinum in silicon after exposure to a low-pressure hydrogen plasma has been observed using transient junction-capacitance spectroscopy. In n-type silicon, a palladium-related level at Ec −0.22 eV and platinum-related level at Ec −0.28 eV were neutralized by a low-temperature (300 °C) plasma treatment. In p-type silicon, a palladium-related level at Ev +0.32 eV was also neutralized by this treatment, but a platinum-related level at Ev +0.33 eV was unaffected by hydrogen plasma exposure. Possible mechanisms for the observed reduction in defect electrical activity are discussed.
Application of energy balance to compute plasma pinch ratios
Authors: Lee S.
Published: February 2003

From energy balance the pinch ratio rp/r0 (where rp = equilibrium pinch radius and r0= original radius) may be directly computed for the case of a constant current electromagnetic pinch. For the case of a varying current, to solve the energy integral requires the current as a function of the pinch radius. To achieve this an approximate pinch trajectory is first estimated using a snow-plow model. This trajectory by itself gives a zero pinch ratio but it enables the energy integral to be performed. The theoretically predicted values of rp/r0 for several cases are found to be in satisfactory agreement with experimental values. This procedure would be useful for designers of pinch devices.
Interaction of reactively sputtered titanium carbide thin films with Si, SiO2Ti, TiSi2, and Al
Authors: Eizenberg M. , Murarka S. P. , Heimann P. A.
Published: February 2003

The interactions of reactively sputtered titanium carbide (TixC) films with Si, SiO2, Ti, TiSi2, and Al have been studied using Auger electron spectroscopy, x-ray diffraction, and four-point probe resistance. The TixC films react with Si leading to silicide phases that are not observed when pure Ti reacts with Si. The interaction of TixC with Si is delayed to higher temperatures with increasing carbon content. For x≤1, no interaction is observed even after 900 °C-30 min anneal. For x≥1, the silicide formation leads to phase separation with TiSi2 near the silicon substrate plus an outer titanium carbide layer, which, like all other TixC films investigated, is found to be an effective diffusion barrier to Al penetration up to 500 °C. For x≤1, no interaction with SiO2 is observed up to 900 °C. However, Ti-rich films interact with SiO2 to form titanium oxide. The stoichiometric film adheres to Ti and TiSi2 much better than to Si and SiO2. It does not react with Ti or TiSi2 up to 750 °C. At 900 °C TiC is unstable on TiSi2.
Transient capacitance measurements on resistive samples
Authors: Broniatowski A. , Blosse A. , Srivastava P. C. , Bourgoin J. C.
Published: February 2003

Peculiar features of Deep Level Transient Spectroscopy (DLTS) measurements on resistive samples are pointed out. Depending on the value of the sample resistance in series with the diode capacitance, the DLTS signal can be strongly reduced and even its sign may be reversed, entailing a possible confusion between majority and minority carrier traps. Means of detecting these effects are discussed and a correction procedure is proposed, based on varying the circuit impedance by means of an additional resistance in series with the sample. Illustrative examples include ion implanted silicon and the case of a germanium bicrystal.
Large-bore copper-vapor lasers: Kinetics and scaling issues
Authors: Kushner M. J. , Warner B. E.
Published: February 2003

The scaling characteristics of large diameter (6≤d≤12 cm) high repetition-rate copper-vapor lasers are investigated using a radially dependent laser-discharge model. Results of the model are verified with experimental data obtained on several devices including an 8-cm-diam 100-W copper-vapor laser. Two effects, penetration of the applied electric field into the plasma and gas heating, which we show are the primary considerations in volumetric scaling, are discussed in detail. Thermal constriction of the discharge resulting from gas heating is prevented by plasma skin effects that allow stable performance at large diameters. These same effects are shown to explain the sequential excitation of the laser levels, resulting in both temporally and spatially dependent behavior of the laser pulse. Projections of output power and light-pulse characteristics are made for lasers up to 12 cm in diameter.