bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of the angular distribution of sputtered neutrals in a planar magnetron geometry
Authors: Eisenmenger-Sittner C. , Bergauer A. , Bangert H. , Bauer W.
Published: July 2002

In the low temperature regime (T<0.3Tm), the microstructure of sputtered films is determined predominantly by the mechanisms of self-shadowing. Shadowing effects are directly related to the angular distribution of incoming sputtered particles. The angular distributions of copper and lead particles sputtered by Ar+ ions in a planar magnetron geometry were measured using a differentially pumped pinhole camera. The pressure in the pinhole camera was lower by a factor of 10 compared to the ambient working gas. Thus it was possible to monitor the angular distribution of the incoming sputter particles for working gas pressures up to 4 Pa. Transparent films of the impinging particles were deposited on semicircular transparent substrates. Their relative thicknesses were measured by optical densitometry, giving a direct representation of the angular distribution at an arbitrarily chosen point of the sputter chamber. A comparison of the measured angular distributions with distributions calculated for the particular geometry of the experimental setup under neglection of gas phase scattering shows that for low gas pressures, the angular distribution is determined mainly by the shape of the target erosion zone, which implies a significant deviation from isotropy. Increasing the gas pressure leads to a broadening of the angular distributions towards isotropy of particle incidence. Nonetheless, the geometry of the erosion zone still has a measurable influence on the shape of the distribution.
Investigation of vapor-deposited polyaniline thin films
Authors: Dillingham T. R. , Cornelison D. M. , Bullock E.
Published: July 2002

X-ray photoelectron spectroscopy (XPS) has been used to investigate the chemical structure of thin polyaniline films grown using a vacuum evaporation process that used chemically prepared polyaniline powder as the starting material. Analysis shows that the as-deposited films are in the completely reduced, leucoemeraldine state. This chemical structure is contrasted with that of the initial and residual powders, which XPS analysis shows are both in a state close to that of protoemeraldine. Thus, the results indicate that the reduction takes place either in the gas phase or, more likely, as a reaction on the surface of the substrate, but does not occur in the quartz crucible as the initial powder is being heated. Results are also presented concerning the oxidation (in pure oxygen and iodine environments) and the protonation (using HCl) of these vapor-deposited polyaniline thin films. Scanning tunneling microscopy was also used to examine the in situ growth of submonolayer coverages of polymer. Evidence for large scale structure growth, possibly resulting from crosslinking of small oligomer components, was observed.
Plasma diagnostics of a direct current arcjet diamond reactor. I. Electrostatic probe analysis
Authors: Reeve S. W. , Weimer W. A.
Published: July 2002

Plasma parameters were determined for a direct current arcjet diamond chemical vapor deposition reactor. Electron temperatures and densities were measured using a floating double probe technique, yielding values ranging from 2.3 eV and 7×1011 cm−3 near the plasma gun nozzle to 0.4 eV and 1×109 cm−3 in the downstream and peripheral regions of the plasma. These results show that the plasma is weakly ionized, indicating that reactions involving electrons play a minor role in the macroscopic gas–phase chemistry though high energy products from these reactions may significantly affect film quality.
Microloading effect prevention in SiO2 contact-hole etching
Authors: Kato Shin-ichi , Sato Masaaki , Arita Yoshinobu
Published: July 2002

The microloading effect in the contact-hole etching below the size of 0.8 μm2 is examined and a multistep etching method that can suppress the effect is proposed. In the initial stages of contact-hole etching, etched SiO2 depth is proportional to etching time and independent of hole size. This is because the polymer layer which prevents etching from proceeding is initially thin. Therefore, the microloading effect can be suppressed by removing the polymer layer before it thickens. We propose a multistep etching method that combines SiO2 reactive ion etching and a polymer layer removal process. Using this method, it is possible to etch small contact holes with little microloading effect, where the difference in the etch depth between 0.2 and 0.8 μm2 holes is within 5%.
Short-gas-residence-time electron cyclotron resonance plasma etching
Authors: Tsujimoto Kazunori , Kumihashi Takao , Kofuji Naoyuki , Tachi Shin’ichi
Published: July 2002

This paper describes short-gas-residence-time electron cyclotron resonance plasma etching for high etch rates, reduced contamination, and highly anisotropic etching. The new high-gas-flow-rate (high-flow) etching system is demonstrated with effective-pumping rate of 2500 ℓ/s. This method produces very high etch rate while maintaining high anisotropy at very low gas pressure below 1 mTorr. The high etch rate is due to the reduction of reaction products density because of the very short gas-residence time of 30 ms. This technique also dramatically reduces the contamination of reaction products. Etching of crystalline Si and n+ polycrystalline Si with the high-flow etching system is demonstrated. For crystalline Si etching with Cl2, a high etch rate up to 1 μm/min is achieved at a high gas flow rate of 90 sccm at 0.5 mTorr.
Microstructural study of sputter-deposited CdTe thin films
Authors: Li X. , Gessert T. A. , Matson R. J. , Hall J. F. , Coutts T. J.
Published: July 2002

In this investigation, cadmium telluride (CdTe) thin films are deposited by radio frequency (rf)-magnetron sputtering and analyzed structurally. Structural variations with processing parameters are assessed using x-ray diffraction and scanning electron microscopy. Results indicate that the microstructure and stress of the films are sensitive to the deposition conditions and CdCl2/annealing procedures. Films deposited at room temperature are columnar type, demonstrating a mixture of zinc blende (cubic) and wurtzite (hexagonal) phases. These films form with the preferential column axis along the cubic [111] direction. In contrast, films deposited at elevated substrate temperatures consist of a closely packed array of cubic-phase polycrystalline grains. The CdCl2/annealing treatment appears to reorganize CdTe microstructures from a columnar to a granular structure, and changes the preferred orientation. The treatment also appears to reduce the residual stress that accumulates during film formation and thereby improves the crystallinity of the grain. However, it is also observed that the CdCl2/annealing treatment tends to increase the extent of voids formed around grains.
Enhancement of thickness uniformity of thin films grown by pulsed laser deposition
Authors: Fernández Félix E.
Published: July 2002

A peculiarity of the pulsed laser deposition technique of thin-film growth which limits its applicability is the very rapid drop of resulting film thickness as a function of distance from the deposition axis. This is due to the narrow forward peaking of the emission plume characteristic of the laser ablation process. The plume is usually modeled by a cosn θ function with n greater, and in some cases much higher, than 1. Based on this behavior, a method is presented to substantially enhance coverage uniformity in substrate zones of the order of the target-substrate distance h, and to within a specified thickness tolerance. Essentially, target irradiation is caused to form an annular emission source instead of the usual spot. By calculating the resulting thickness profiles, an optimum radius s is found for the annular source, corresponding to a given power in the emission characteristic and a given value of h. The radius of this annulus scales with h. Calculated numerical results for optimal s/h ratios corresponding to a wide range of values for n are provided for the case of ±1% tolerance in deviation from the thickness at deposition axis. Manners of producing annular illumination of the target by means of conic optics are presented for the case of a laser beam with radially symmetric profile. The region of uniform coverage at the substrate can be further augmented by extension of the method to multiple concentric annular sources. By using a conic optic of novel design, it is shown also how a single-laser beam can be focused onto a target in the required manner. Applicability of the method would be limited in practice by the available laser power. On the other hand, the effective emitting area can be large, which favors extremely high growth rates, and since growth can occur uniformly over the whole substrate for each laser pulse, single-shot depositions with substantial thicknesses are possible. In addition, the simultaneity of growth over the complete substrate is desirable when monitoring the growth in situ.
Adsorption of TiCl4 on TiSi2: Application to silicide chemical vapor deposition
Authors: Southwell R. P. , Seebauer E. G.
Published: July 2002

The adsorption/desorption kinetics of TiCl4 on polycrystalline TiSi2 have been measured quantitatively by temperature-programmed desorption in order to better understand the chemical vapor deposition of the silicide from TiCl4 and SiH4. For small exposures, only SiCl2 desorbs near 1150 K. The kinetics are second order with respect to surface chlorine, and the desorption activation energy Ed is 85±4 kcal/mol. As this state approaches saturation, SiCl2 desorbs from a second state near 700 K. The kinetics are also second order, but desorption occurs through a continuum of energetic pathways peaking at 57 kcal/mol. As this state saturates, a third desorption peak consisting of SiCl4 appears near 500 K. The kinetics are first order with respect to surface chlorine and also comprise a distribution of energetic pathways, which peak at 33 kcal/mol. Coadsorption studies with SiH4 were also performed. Surface chlorine appears to bond to Si, not Ti, on the surface. These kinetics are utilized to predictively model the chemical vapor deposition of TiSi2 thin films.
Quantitative spectral measurement of air leaks into plasma reactors
Authors: Barna Gabriel G.
Published: July 2002

An adaptation of the classical ‘‘standard addition’’ technique has been implemented to quantitatively measure the magnitude of an air leak into the gas lines of any plasma reactor. This measurement can be run on any original equipment manufacturer plasma reactor equipped with some means for the spectral analysis of the plasma. The only additional requirement is a mass flow controller used to make the incremental air (or N2) additions to generate an in situ calibration curve. The technique can be readily automated to provide a diagnostic of hardware integrity.
Study of titanium–nitrogen films deposited in an electron beam evaporation unit
Authors: Brown J. D. , Govers M. R.
Published: July 2002

Comparative studies were performed on the chemical composition, crystal structure, adhesion, and color of titanium–nitrogen films prepared by an electron beam thermal evaporation process. Several parameters, deposition rate, nitrogen flow rate, substrate temperature, and nitrogen inlet location, were varied during sample preparation. The composition of the films was determined by electron probe microanalysis, the crystal structure by grazing angle x-ray diffraction, and the adhesion characteristics by scratch test analysis. Glass substrates were used to allow for visual inspection of the substrate–film interface layer. Titanium–nitrogen films with nitrogen contents varying between 7.61 and 32.5 wt % were produced. Over this range, three structures were deposited: α-TiN0.3 for low nitrogen contents, Ti2N for films of 12.2–13.1 wt % nitrogen, and TiN for films with higher nitrogen contents. The films exhibited a wide range of colors that could be related to other properties such as nitrogen content and adhesion.
Real-time monitoring of the deposition and growth of thin organic films by in situ ellipsometry
Authors: Wall J. F. , Clauberg E. , Murray R. W. , Irene E. A.
Published: July 2002

Polyphenylene oxide (PPO) films have been electrochemically deposited onto gold substrates, yielding ultrathin films on the order of 10 nm. The deposition was monitored by in situ ellipsometry in real time, in order to follow the growth and determine the mechanism. The films were subsequently characterized by ex situ spectroscopic ellipsometry to confirm the final film thickness and growth rate. A combination of ellipsometry and atomic force microscopy observations made in the early and final stages of film formation suggest that a nucleation regime exists. Initially, deposition occurs quickly and is then followed by mass transport controlled growth. A diffusion coefficient of 1.0×10−15 cm2/s was calculated for phenol through a 5 nm PPO film. Two rate constants were determined, one for initial deposition (k1=4.7×10−1 s−1) and another for the diffusion controlled regime (k2=6.8×10−5 s−1).
Control of radio-frequency-plasma process to improve the reproducibility of silicon oxynitride thin film preparation
Authors: Diatezua D. M. , Thiry P. A. , Caudano R.
Published: July 2002

We have performed a calibration process in order to reduce the uncertainty in the radio-frequency (rf)-plasma preparation of silicon oxynitride. Two typical curves were built: the first one gives atomic concentration ratios versus plasma conditions and the second one gives deposition rates versus the atomic concentration ratios. Prior to the calibration process, we determined an optimum plasma working point. Infrared reflection experiments performed on two multilayered devices prepared under identical conditions give similar spectra, and confirm the improvement obtained in the reproducibility of the rf-plasma process. The composition depth profile of another multilayered structure demonstrates the in-depth stoichiometric homogeneity.
Flux distributions and deposition profiles from hexagonal collimators during sputter deposition
Authors: Lin Zhou , Cale Timothy S.
Published: July 2002

We use the Monte Carlo method to simulate transport through a single hexagonal collimator cell and transport from the exit of the cell to the substrate. We assume a distribution function for the species entering the collimator, and that the pressure is low enough so that the transport inside the collimator cells is free molecular flow. Three-dimensional flux distributions of species exiting the collimator cell are obtained as functions of the sticking factor of the sputtered material in the collimator and the collimator aspect ratio. Specular as well as diffuse re-emission, for species which have subunity sticking factors, are considered. The larger the sticking coefficient and the higher the aspect ratio, the higher the ‘‘beaming’’ effect of the collimator and the smaller the fraction of species which make it through the collimator. For nonunity sticking factors, diffuse re-emission produces a more collimated beam than specular re-emission, and the fraction of the species which make it through the collimator are lower for diffuse re-emission. Collisional transport is tracked from the collimator exit to the substrate using Monte Carlo simulations for each species. The deposited film profile from a single collimator cell is computed by assuming a sticking factor of one on the substrate. The film profile over macroscopic regions of the wafer is obtained by summing the fluxes from all the collimator cells. Calculated variations in film thickness are explained in terms of collimator to wafer distance and mean free path of the sputter gas.
Magnetic properties of ion-beam sputter deposited NiFe ultrathin films
Authors: Ueno Masaki , Tanoue Shuji
Published: July 2002

Studies have been made of the magnetic properties of NiFe ultrathin films 15–100 Å thick. The NiFe films were deposited on Cu, Ti, and Ta underlayers by an ion-beam sputtering method. In the NiFe films deposited on the Cu layers, the saturation magnetization shows little change with thickness down to 60 Å, but below this it shows a gradual decrease with decreasing thickness. The coercivity in the hard axis is almost unaltered with the film thickness, whereas the coercivity in the easy axis and the anisotropy field decrease with decreasing film thickness. Both values greatly decrease below 30 Å. Thickness dependence of the induced uniaxial anisotropy constant and the direct-current permeability were obtained from these parameters. Remarkable decreases of these parameters were observed in the films on the Ti and Ta layers likely owing to the formation of fine islands. Magnetic properties and giant magnetoresistance in multilayers are discussed on the basis of the present experimental results.
An x-ray photoelectron spectroscopic study of voltage bias implantation and nitrogen etching of aluminum
Authors: Rooke Michael A. , Rotole John A. , Sherwood Peter M. A.
Published: July 2002

Aluminum nitride (AlN) was produced on the surface of aluminum metal by nitrogen (N2) etching at ion energies of 6–8 keV. An electrical potential bias was applied to the sample during etching to enable a study of the effect of such a bias on the formation of the AlN. The results show that AlN will form during etching, although any oxygen present will preferentially react to form the oxide. We find an unusual peak in the N 1s region, shifted 7.5 eV to higher binding energy from the main peak, when etching is performed with oxygen impurities in the nitrogen supply. It is believed that this peak arises from the implantation of N2 into oxidized aluminum. We believe that voltage biasing does not affect the products of nitrogen etching of aluminum.
Low temperature formation of textured ZnO transparent electrodes by magnetron sputtering
Authors: Minami Tadatsugu , Sonohara Hideo , Takata Shinzo , Fukuda Ichiro
Published: July 2002

This article describes a high pressure magnetron sputtering technique that results in milky transparent conducting Al-doped ZnO (ZnO:Al) films with a textured surface prepared on substrates at a temperature of 200 °C. Large-area milky transparent conducting ZnO:Al films with a uniform spatial resistivity distribution on the substrate were prepared at a sputter pressure of 60–80 Pa by direct current magnetron sputtering. A total transmittance of 72% and a haze factor of 54% at a wavelength of 550 nm as well as a sheet resistance as low as 16 Ω/sq were obtained in milky ZnO:Al films of about 1000 nm thick prepared at a sputter pressure of 80 Pa. In addition, a two step deposition that realizes a high deposition rate and a low sheet resistance was demonstrated. A 1350-nm-thick milky ZnO:Al film with a sheet resistance of 4 Ω/sq and a haze ratio of 13% at a wavelength of 550 nm was prepared that had about a five times greater deposition rate than that observed at a high sputter pressure of 80 Pa.
Photoemission studies of K-promoted nitridation and oxidation of the InP(100) surface using synchrotron radiation
Authors: Zhao T. X. , Ji H. , Liang Q. , Wang X. P. , Xu P. S. , Lu E. D. , Wu J. X. , Hsu C. C.
Published: July 2002

The effect of a potassium overlayer on nitridation and oxidation of the InP(100) surface is investigated by core-level and valence-band photoemission spectroscopy using synchrotron radiation. In comparison with the K-promoted nitridation of the InP(110) surface obtained by cleavage in situ, we found that the promotive effect for the InP(100) surface cleaned by ions bombardment is much stronger and that the nitridation products consist of two kinds of complexes: InPNx and InPNx+y. The results confirmed that surface defects play an important part in the promotive effect. Furthermore, in contrast with K-promoted oxidation of InP(100) where bonding is observed between indium and oxygen, indium atoms did not react directly with nitrogen atoms during the K-promoted nitridation of InP(100).
Matrix effect of bombardment-induced Gibbsian segregation on Cu depletion at a CuXNi100−X subsurface
Authors: Zheng Li-Ping , Li Ri-Sheng , Xia Xi-Qing , Li Min-Qian , Li Ming-Yao
Published: July 2002

A dynamic Monte Carlo program, including an improved bombardment-induced Gibbsian segregation (BIGS) model was employed to study the matrix effect of BIGS and its influence on Cu depletion at the subsurface under 1 keV Ar ion bombardment of a Cu–Ni alloy. The calculated results show that not only at high fluence (the steady-state) but also at low fluence the Cu subsurface depletion depends on its bulk composition. This is because the atomic jump rate W21 of Cu from the second layer to the first layer is correlated to Cu bulk composition at any fluence. We also found that the product of the nonsegregating species concentration in the first layer with the segregating species concentration in the second layer plays a more important role than other parameters in determining W21 under low current conditions.
Role of chemical bonding in the epitaxial growth of noble metals on ionic crystal substrates
Authors: Yamamoto K. , Kasukabe Y. , Takeishi R. , Osaka T.
Published: July 2002

Thin films of Au were deposited onto MgO substrates cleaved in ultrahigh vacuum. The films, which were examined by transmission electron microscopy and electron diffraction, did not grow with a (111) orientation observed in a Au/NaCl system but with a (100) orientation which had been observed in a Pd/MgO system. In order to obtain some insight into the differences in the epitaxial orientations, we studied interfacial chemical bonding states in Au/MgO(100), Pd/MgO(100), and Au/NaCl(100) systems using total pair-potential calculations and discrete variational Xα calculations. The results show that interfacial interaction in both the Au/MgO and the Pd/MgO system is stronger than that in the Au/NaCl system. The relation between the strength of the interfacial chemical bond and the epitaxial orientation in the above systems is discussed.
Pure and fluorine-doped silica films deposited in a hollow cathode reactor for integrated optic applications
Authors: Bazylenko M. V. , Gross M. , Simonian A. , Chu P. L.
Published: July 2002

Silica films have been deposited in a high density hollow cathode plasma deposition system from silane and oxygen gas mixtures. Additions of carbon tetrafluoride (CF4) were used to fluorine dope the silica. The deposited films were characterized by means of Fourier transform infrared (FTIR) spectroscopy, wavelength dispersive x-ray spectroscopy, chemical etch rate (P etch), stress and refractive index measurements. The pure silica films, though deposited at a high rate (over 1500 Å/min), exhibit a P-etch rate only 1.3 times that of thermal oxide. The refractive index of the as-deposited silica is higher than that of thermal oxide, but reduces to the thermal oxide value after high-temperature (1000 °C) annealing. Based on the thickness change measurements, the higher refractive index was attributed to a higher density of the deposited silica due to a smaller Si–O–Si bond angle, as supported by FTIR data. Fluorine doping results in a reduction in film stress by a factor of 4 over pure silica, as well as a reduction in OH content from about 1 at. % in pure silica to below the FTIR detection limit (0.1 at. %). The refractive index initially decreases with CF4 flow rate, concomitant with an increase in fluorine content, but then rises above the refractive index of pure silica. This increase has been found to be due to the deposition of silicon-rich oxide at the higher CF4 flow rates, which is attributed to an increasingly oxygen deficient discharge resulting from oxygen consumption by the dissociation products of CF4.
Uniformity of radio frequency bias voltages along conducting surfaces in a plasma
Authors: Stevens J. E. , Sowa M. J. , Cecchi J. L.
Published: July 2002

High-density magnetic-field-free plasma sources produce plasmas that are opaque to radio frequency (rf) fields in the 0–200 MHz frequency range. Thus plasma currents from a biased substrate flow to ground along reactor surfaces. We investigate some consequences of this rf skin effect in an inductively coupled plasma source with densities of 1011–1012 cm−3 in argon. Magnetic probe measurements confirm that capacitively coupled rf fields are localized near the reactor surfaces. Electric probes were used to measure the voltage on the surface of a biased platen without a substrate. We find that the rf wavelength and phase velocity along reactor surfaces are reduced by a factor of ∼5 compared to free space. This reduced wavelength is attributed to a surface wave which can be analyzed using a formalism similar to that for Trivelpiece–Gould modes.
Interaction of SiH4 with Si(100)2×1 and with Si(111)7×7 at 690 K: A comparative scanning tunneling microscopy study
Authors: Fehrenbacher M. , Spitzmüller J. , Memmert U. , Rauscher H. , Behm R. J.
Published: July 2002

We have studied the interaction of SiH4 with Si(100)2×1 and with Si(111)7×7 utilizing scanning tunneling microscopy. At 690 K Si deposition does not saturate, but the reactive sticking coefficient is considerably larger for Si(100)2×1. On this surface the 2×1 reconstruction is preserved during deposition. The anisotropy of the newly formed islands and the growth process are influenced by the presence of hydrogen from dissociated SiH4. In contrast, the Si(111)7×7 surface is completely restructured by the interaction with SiH4. This results in the formation of a bulklike hydrogen terminated 1×1 structure without any remnants of stacking faults. After exposure to 50 000 L SiH4 at 690 K not more than half a bilayer has grown, forming triangular Si(111)1×1-H islands.
Healing of surface defects in hard materials by thin coatings
Authors: Konyashin I. Yu.
Published: July 2002

Results on improvements in the transverse rupture strength of WC-based cemented carbides, TiCN-based cermets, and Al2O3-based ceramics by the physical vapor deposition of thin coatings are presented. Evaluation of strength decreases in cemented carbides versus the length of half-elliptic cracks in the near-surface layer reveals enhancement of the cracks’ influence of the rupture stress value with decreasing fracture toughness of the cemented carbides. TiCN coatings obtained when simultaneous surface ion etching and depositing lead to healing Palmquist cracks formed near corners of Vickers indentations. The coatings are assumed to heal various defects present at the surface of hard materials, which result in an increase in transverse rupture strength of cemented carbides, cermets, and ceramics. Tool lifetime of Al2O3-based ceramic cutting inserts can be improved by depositing the coatings due to the healing surface defects resulting in retardation of cracks’ initiation and propagation in interrupted cutting.
Evaluation of the dispersive nature of meshes used for the spherical aberration correction of electrostatic lenses
Authors: Kato M. , Sekine T.
Published: July 2002

Although spherical aberration of electrostatic lenses can be corrected in principle by employing meshes, the holes in meshes give rise to local disturbances in the electric field and the performance of mesh lenses deteriorates somewhat due to this effect. The disturbed electric field around mesh holes has a lens action, so a mesh can be regarded as a set of single-aperture lenses. It is shown that the optical properties of single-aperture lenses can be approximated to high precision by means of a transfer matrix. Using this formulation, the lens effect added by the presence of holes is extracted without ambiguity from the action of the total lens field. Moreover, the condition where a single-aperture lens can be regarded as a thin lens with a certain focal length is clarified. An image of a point source is blurred by mesh holes, and the amount of blurring is explained to high precision by their first-order defocusing action as single-aperture lenses; calculations using ray tracing have confirmed this. It is shown that the blurring can be suppressed to an acceptable level in applications such as transfer optics for electron spectrometers.
Low-temperature deposition of cubic BN:C films by unbalanced direct current magnetron sputtering of a B4C target
Authors: Johansson M. P. , Ivanov I. , Hultman L. , Münger E. P. , Schütze A.
Published: July 2002

Controllable-unbalanced dc magnetron sputtering of a B4C target in mixed Ar–N2 discharges has been used to deposit BN:C thin films with carbon concentrations in the range of 5–21 at. % on Si(001) substrates. The variation of the nitrogen gas consumption with nitrogen partial pressure was used to determine the sorption capacity of the sputtering source and was then correlated to the film elemental composition. An additional axially symmetric magnetic field was used to vary the discharge plasma density near the substrate in a wide range. Hence, the ion flux Ji of primary Ar+ and N+2 ions accelerated to the substrate by an applied negative substrate bias could be varied while keeping the deposition flux Jn (the sum of film building species, B, C, and N atoms) near constant. BN:C films were grown at large ion-to-neutral flux ratios 3≤Ji/Jn≤24, ion energies Ei≤500 eV, and substrate temperatures 150≤Ts≤350 °C. The phase and elemental composition of as-deposited BN:C films were characterized by Fourier transform infrared spectroscopy and wavelength dispersive x-ray spectroscopy, respectively. Deposition of cubic phase c-BN:C containing 5–7 at. % of C is demonstrated under conditions of low energy (110 eV) ion bombardment, a high ion-to-atom arrival rate ratio (Ji/Jn∼24), and low growth temperatures (∼150 °C).
Laser desorption study of deuterium implanted in silicon carbide
Authors: Kéroack D. , Terreault B.
Published: July 2002

Laser desorption of deuterium implanted in hot-pressed silicon carbide samples was performed. The samples had been implanted at ion energies ranging from 1 keV/D to 3 keV/D and at fluences from 0.6×1020 m−2 to 1.8×1021 m−2. For the high fluence samples (≥3×1020 m−2), comparison of the experimental data of desorption rate versus laser energy with the results of computer simulations reveals that second order detrapping is the limiting re-emission process. The effective trap activation energy decreases from 0.9±0.1 eV/molecule at 1 keV/D to 0.5±0.1 eV/molecule at 3 keV/D. Blister formation and exfoliation or other forms of radiation damage could explain the energy dependence in the high fluence samples. At low fluence (<3×1020 m−2), most of the D2 re-emission takes place above the melting threshold (12 kJ/m2). Computer simulations, using the thermal properties of the solid phase of SiC extrapolated above the melting point, give information about the nature of the detrapping process. A first order detrapping mechanism with an activation energy of 2.0±0.2 eV was found under those conditions. A comparaison is made with the deuterium laser desorption behaviour in Be, C and Si.
Molecular beam epitaxy growth of CdTe on (211)A GaAs
Authors: Yin Jingjiang , Huang Qi , Zhou Junming , Yin Jingou
Published: July 2002

CdTe has been grown on (211)A GaAs for the first time in the growth temperature range of 240–310 °C by molecular beam epitaxy. The quality and characteristics of the epitaxial film were studied by photoluminescence spectra, an x-ray double crystal rocking curve, a Nomarski interference microscope, and etching. High quality CdTe films were obtained. For our best film the full width at half maximum of the x-ray double crystal rocking curve was 126 arcsecond, and that of photoluminescence at 77 K was 8.9 meV. The epilayer was always (211)A CdTe with a tilted angle of about 2° around CdTe[01̄1]∥GaAs[01̄1] with respect to the substrate. A model of the initial growth stage of CdTe on (211)A GaAs is presented.
Vacuum performance of the Synchroton Radiation Research Center 1.3 GeV synchrotron light source
Authors: Hsiung G. Y. , Huang J. R. , Shyy J. G. , Wang D. J. , Chen J. R. , Liu Y. C.
Published: July 2002

The operation of the Synchrotron Radiation Research Center 1.3 GeV synchrotron light source vacuum system shows good features of quick beam self-cleaning, low carbonaceous gas desorption, and less dust. The phenomenon of the photon induced desorption (PID) has been studied. Recently, a set of new vacuum chambers for wiggler were installed, and the commissioning of the storage ring was restarted. The pressure rise and the PID coefficients during the beam running both in the straight and bending chambers were compared. The performance of the overall vacuum system is to be described.
Improved substrate temperature stability during molecular beam epitaxy growth using indium free mounting of small substrates of various shapes
Authors: Sieg R. M. , Sacks R. N. , Grillot P. N. , Ringel S. A.
Published: July 2002

Large substrate surface temperature decreases are observed during molecular beam epitaxy growth onto small indium bonded substrates, due to coating of the molybdenum block. These large temperature transients, along with other difficulties associated with indium bonding (e.g., potential substrate surface damage, unwanted indium on the back of the substrate) make indium free substrate mounting desirable, however, indium free mounting systems have previously been restricted to whole standard-sized round wafers. In this study we compare the temperature characteristics of new indium free modular substrate mounting blocks, which can accommodate substrates of various sizes (up to 3 inch diameter) and shapes, with traditional indium mounting of small substrates. Although the new modular indium free holders have a large molybdenum surface area exposed to the molecular beams, we find that the substrate surface temperature transients during growth are reduced to nearly negligible levels versus similar growth on indium bonded substrates, due to the effective thermal isolation of the substrate from the molybdenum. The real effects of these temperature differences observed by in situ pyrometry were confirmed by ex situ deep level transient spectroscopy (DLTS) measurements of homoepitaxial GaAs films, which show a two-to-three order of magnitude trap density increase in films grown on indium bonded substrates versus films grown on substrates mounted without indium bonding. This DLTS result is consistent with a real growth temperature difference between the two mounting techniques as was measured in situ by pyrometry.
Lightly nitrided N2O/O2 gate oxidation process for submicron complementary metal–oxide semiconductor technology
Authors: Roy P. K. , Ma Y. , Weinhoffer M.
Published: July 2002

This works describes the development of a robust high quality N2O/O2-grown thin gate oxide for sub-0.5 μm complementary metal–oxide semiconductor technology. Improvements in gate oxide quality (leakage D0, breakdown Vbd, and wearout Nbd) have been attained without compromising on interface-state density (Dit) of these oxides. Such improvements have been attributed to the light nitrogen incorporation in SiO2 near the Si/SiO2 interface. Optimum lower thermal budget N2O/O2 oxidation process has been achieved by using a N2O/O2 ratio of one in the oxidant ambient.
Epitaxial growth of ZnO thin films on R-plane sapphire substrate by radio frequency magnetron sputtering
Authors: Kim Young Jin , Kim Yoo Taek , Yang Hyung Kook , Park Jong Chul , Han Jung In , Lee Yong Eui , Kim Hyeong Joon
Published: July 2002

ZnO thin films were deposited on a R-plane sapphire substrate. The effects of the thermal energy and the kinetic energy of the sputtered species on the growth of ZnO thin films were investigated. By varying the substrate temperature, chamber pressure, and radio frequency power, the structure of ZnO thin films was transformed from polycrystalline to epitaxial on R-plane sapphire substrates. High quality (110) ZnO epitaxial thin films were grown at the condition of 400 °C, 250 W, and 5 mTorr. According to reflection high energy electron diffraction and reflection electron microscopy observations, there were no double diffraction distortion and any other patterns. Its surface roughness observed by atomic force microscopy was about 27 nm.
Relaxation of interfacial stress and improved quality of heteroepitaxial 3C–SiC films on (100)Si deposited by organometallic chemical vapor deposition at 1200 °C
Authors: Vepřek S. , Kunstmann Th. , Volm D. , Meyer B. K.
Published: July 2002

We were able to significantly improve the quality of the heteroepitaxial films of the cubic modification of silicon carbide, 3C–SiC, by the use of organosilicon precursors and a careful control of the initial stage of the growth. The films were prepared by chemical vapor deposition from an organometallic precursor, methyltrichlorosilane. It is shown that the interfacial stress, which originates from the large lattice mismatch between the silicon substrate and the SiC film, efficiently relaxes with increasing distance between the interface yielding thick films of high quality for a thickness of ⩾20 μm.
Use of laser reflectometry for end-point detection during the etching of magnetic thin films
Authors: Khamsehpour B. , Wilkinson C. D. W. , Chapman J. N.
Published: July 2002

Laser reflectometry at a wavelength of 679 nm has been employed for monitoring and detection of the end point during the etching of thin films of magnetic materials. Oscillations in the detected reflected signal due to the periodicity of multilayer structures for Pt/Co and Cu/Co with periods as small as 3 nm have been recorded. Known details of the structures have been used to model the normal incidence reflectance to compare with the observed results. This technique allows the etching to be stopped after removal of the thin magnetic multilayer film to an accuracy of better than 5 nm in the cases cited.
Chemisorption of CO on the Ir(111) surface: Adsorption and desorption kinetics measured with in situ vibrational spectroscopy
Authors: Sushchikh M. , Lauterbach J. , Weinberg W. H.
Published: July 2002

The kinetics of adsorption and desorption of carbon monoxide on Ir(111) have been investigated using the well-defined and carefully calibrated IR absorption peak position of the CO intramolecular stretching vibration as a nonintrusive coverage probe. Experiments were performed with time-resolved Fourier transform infrared reflection–absorption spectroscopy (TR-IRAS), which allows high-resolution measurements over a large pressure range between 1×10−8 and 1×10−5 mbar and surface temperature range between 390 and 500 K. The rate of desorption into vacuum is compared with the rate of desorption in the presence of a finite pressure of the desorbing gas. In this case, a flux-dependent enhancement of the desorption rate has been observed previously, which, if existent, should have an important impact on heterogeneously catalyzed reactions performed under high-pressure conditions. Most of these experiments, however, were performed using thermal desorption spectroscopy, a nonequilibrium method. We have been able to measure all rate parameters that are essential to describe the desorption in situ with TR-IRAS and have, thereby, clarified the disagreements that exist in the literature.
Characterization of a solid fluorocarbon film on magnetic recording media
Authors: Karis T. E. , Tyndall G. W. , Fenzel-Alexander D. , Crowder M. S.
Published: July 2002

Fluorocarbon films were deposited on carbon overcoated magnetic recording media from monomers using an ion beam apparatus. The films were characterized using sensitive surface analytical and spectroscopic methods. These include nuclear magnetic resonance spectroscopy, dielectric spectroscopy, infrared spectroscopy, x-ray photoelectron spectroscopy, scanning Kelvin probe, ellipsometry, Rutherford backscattering, Auger electron spectroscopy, secondary ion mass spectroscopy, contact angle, and nanoindentation. The film thickness, chemical composition, hardness, and surface potential were measured across the media surface. The fluorocarbon film was insoluble and no melting or glass transition was observed up to 220 °C. Ambient organic adsorbates are detected on the surface, and the film undergoes a relaxation process that occurs over about 20 days time following deposition. The initial advancing water contact angle is controlled through surface modification by a plasma treatment in the final deposition stage.
Core–electron excitation for Si photochemical process using high intensity monochromatized synchrotron radiation
Authors: Iba Yoshihisa , Sugita Yoshihiro , Nara Yasuo
Published: July 2002

We developed a low-resolution, high intensity monochromator composed of one multilayer mirror, two plane Pt mirrors, and a filter to investigate core-electron excitation effects induced by a photochemical reaction. We used a Mo/B4C multilayer mirror, which exhibits a high reflectivity at the L-shell absorption edge of Si (100 eV). We also examined the photoinduced fragmentation of SiH4 and Si2H6 molecules at the absorption edge using a synchrotron radiation beam. We confirmed that core–electron excitation initiated the fragmentation of these molecules into multiple ionization particles.
Search for coupling in ferromagnetic/superconducting multilayers: Fe4N/NbN
Authors: Mattson J. E. , Potter C. D. , Conover M. J. , Sowers C. H. , Bader S. D.
Published: July 2002

Structural, magnetic, and superconducting properties of ferromagnetic/superconducting multilayers of Fe4N/NbN are examined. The onset of superconductivity occurs at NbN layer thickness of ∼100 Å. Below this thickness ferromagnetism of the Fe4N layers is observed. Above this thickness superconductivity of the NbN is also observed, but there is no evidence for interlayer magnetic or superconductive coupling. The results are used in the formulation of guidelines for future searches of novel interlayer coupling phenomena. The superconducting critical field curves are reasonably well described within the framework of the theory for ferromagnetic/superconducting multilayers.
Structure of fluorine-doped silicon oxide films deposited by plasma-enhanced chemical vapor deposition
Authors: Yoshimaru M. , Koizumi S. , Shimokawa K.
Published: July 2002

The Fourier transform infrared (FTIR) spectra and Raman spectra of fluorine-doped silicon oxide films capped by silicon nitride thin film to prevent water absorption from the air were measured as a function of the fluorine concentration in the films. It was found that fluorine doping diminishes the Si–OH bonds in films. Films without fluorine show a clear OH band attributable to Si–OH bonds, but films with 7.6 at % (F) or more exhibit no OH band in FTIR spectra. The FTIR spectra also show that fluorine in films forms new absorption bands at frequencies ranging from 990 to 920 cm−1. These absorption bands are assigned as silicon monofluoride sites (940 cm−1) and as silicon difluoride sites (925 and 985 cm−1). While the silicon difluoride sites increase linearly with increasing fluorine source gas flow, the increase in silicon monofluoride sites saturate at a certain fluorine source gas flow [i.e., a fluorine concentration in film of about 7.6 at % (F)]. The Raman spectra show that fluorine doping reduces the planar threefold ring structures in the films. It is surmised that fluorine interchanges preferentially with oxygen in strained Si–O–Si bonds, forming silicon monofluoride and silicon difluoride sites.
Deposition of GaAs (111) epilayers on BaF2 (111)/Si (100) heterostructures by molecular beam epitaxy
Authors: Stumborg M. F. , Santiago F. , Chu T. K. , Boulais K. A.
Published: July 2002

The epitaxial deposition of (111)-oriented GaAs on substrates consisting of BaF2 (111)/Si (100) heterostructures has been investigated. The temperature dependence (from 575 to 650 °C in 25 °C steps) of the initial stages of deposition was examined. Substrates were exposed to Ga and As fluxes simultaneously during these depositions. In situ x-ray photoelectron spectroscopy and reflection high-energy electron diffraction showed that the GaAs grows epitaxially between 575 and 625 °C. The amount of material adhering to the surface during deposition decreases as the substrate temperature increases. GaAs does not adhere to the surface at 650 °C. Analysis of the Ba 3d5/2 photoelectron peak indicated a surface chemical reaction between Ba and the GaAs. In order to determine which species was reacting with the Ba atoms, a BaF2 (111) surface was exposed separately to Ga and As fluxes at 625 °C and to Ga at 650 °C. No chemical interactions were observed, indicating that the presence of both species is required before the chemical reaction and subsequent epitaxial deposition will occur. A chemical reaction that produces a gaseous GaF byproduct resulting in a Ba “template” layer is proposed. This Ba layer facilitates the epitaxial deposition of the GaAs layer.
Spectroscopic studies of native oxide formation on a SiO2–InSb interface
Authors: Valcheva E.
Published: July 2002

Parallel investigations of Raman scattering and spectroscopic ellipsometry of plasma-enhanced chemical vapor deposited SiO2 on InSb was carried out. The purpose was to obtain more comprehensive information about the structure and composition of the deposited layers. These consist of stoichiometric and homogeneous SiO2. An interface layer of a significant thickness of 130 Å whose optical constants differ from those of the basic film is observed. The interlayer is composed of sublayers as a result of a chemical reaction of the InSb natural surface oxide and the plasma environment during deposition.
Surface analysis study of the oxidation of organotin films deposited by ArF excimer laser chemical vapor deposition
Authors: Larciprete R. , Borsella E. , De Padova P. , Perfetti P. , Crotti C.
Published: July 2002

ArF excimer laser photolysis of gas phase tetramethyltin was used to deposit thin organotin films on Si. In situ Auger electron spectroscopy and x-ray photoelectron spectroscopy (XPS) film analysis, showed the presence of C and Sn, which, according to C 1s and Sn 3d5/2 peak deconvolution, were organized in highly branched polymeric chains likely containing H as well. The film was oxidized at room temperature by exposure to controlled quantities of O2 up to 5.4×1012L. Sn 3d5/2, C 1s, and O 1s XPS peaks monitoring allowed us to follow the sequence of the oxidative reactions. It resulted that oxygen attacks first the Sn–H and Sn–C sites leading to the elimination of H2O and C containing volatile compounds, which determines a rearrangement of the cleaved bonds and an overall decrease of the measured C content. After this fast phase, oxygen is inserted in the Sn–Sn and Sn–C bonds, with formation of Sn–O–Sn, Sn–O–C, and Sn–C–O species. At the highest oxygen doses the dominating SnO2 component shows that almost all available Sn bonds are oxidized to Sn4+. However, either core level or valence-band spectroscopy demonstrated that below the near-surface layer the tin oxide phase remains substoichiometric, as if the SnO2 at the surface behaves as a passivating agent toward further oxidation.
Chemical vapor deposition of diamond films on hydrofluoric acid etched silicon substrates
Authors: Schelz S. , Borges C. F. M. , Martinu L. , Moisan M.
Published: July 2002

The effect of silicon substrate pretreatment by hydrofluoric acid (HF) upon nucleation density (ND), surface roughness, and crystal quality of polycrystalline diamond films obtained by chemical vapor deposition has been investigated. Si(100) substrates, initially pretreated classically by ultrasonic scratching with a diamond grit suspension in a methanol bath, have been submitted to HF (50%) etching and subsequent water rinsing prior to plasma exposure. Provided the rinsing time was short, the value of ND was found to be up to 30% higher and the surface roughness as much as 30% lower than on unetched substrates, while the diamond film quality remained unaffected. Longer rinsing times in water after HF etching led to a lower ND than on unetched substrates. The increase in nucleation density on the HF-etched substrates has been correlated with an increased plasma etching during the first moments of the deposition process. The increased roughening of the surface due to plasma etching is believed to be responsible for the observed increased nucleation density.