bluuebunny/crossref_metadata_2025 huggingface dataset:
Sputtered high temperature thin film thermocouples
Authors: Kreider Kenneth G.
Published: July 2002

Thin film thermocouples have the advantage of extremely fast response (≤1 ms), low cost, and very fine spatial resolution. These capabilities have permitted measurements never before possible, such as the instantaneous temperature measurements of the inside surfaces of a diesel engine cylinder during operation. Although these type S platinum plus platinum 10% rhodium thermocouples are stable at the 900–1100 °C range, oxidation of rhodium can take place in the 600–800 °C range in air which lessens the thermoelectric potential of the positive element. We evaluated the effect of air exposures to high temperature thin film thermocouples and attempted to find solutions to the problem. We found that after 50 h at 750 °C the Seebeck coefficient of a platinum 10% rhodium element was reduced 50% compared to the as-sputtered condition. The reduction of Seebeck coefficient at 700 and 800 °C was also substantial. This reduction in Seebeck coefficient could be recovered by annealing the thin film at 900 °C. The degradation after 750 °C could be suppressed using a 1 μm sputtered aluminum oxide coating. The reversible behavior suggests the formation of Rh2O3 at 700–800 °C and its subsequent reduction at temperatures at which the free energy of formation is zero or positive. Microstructural evidence confirm these conclusions.
Auger electron spectroscopy electron-beam induced damage of a H2O-covered Si(100) surface
Authors: Viscido L. , Heras J. M.
Published: July 2002

The effect of 2-keV electron-beam irradiation on H2O adsorbed onto a Si(100) single crystal at 300 K was studied using Auger spectroscopy. The incident electron beam induces surface oxidation exclusively in the region irradiated as indicated by measurements of the lateral composition profile. Oxidation ceases when the broad SiLVV Auger peak extending from 74 to 83 eV is ≊5 times higher than the peak at 91 eV, a process which requires ≊80-L H2O exposure (pH2O=1.3×10−7 mbar) using normal beam incidence. The oxygen atomic fraction at this point is ≊0.82. After 15 h at 300 K, the ratio of the normalized peak-to-peak signals at 78 and 511 eV is 1:1. A focused beam of 2-keV 1-mA emission (≊20-μA sample current) in the absence of water is capable of destroying the oxide layer, practically recovering the clean surface after 1 h. Annealing at 800 K has little effect on the oxide. Depth profiling by Ar+ bombardment indicates that the thickness of the oxide film is ≊1.0 nm.
Photoassisted growth of gallium nitride by gas source molecular beam epitaxy
Authors: Paisley M. J. , Davis R. F.
Published: July 2002

Thin films of GaN have been achieved via gas source molecular beam epitaxy with and without substrate illumination from a 500 W Hg arc lamp. X-ray photoelectron spectroscopy showed a nominally stoichiometric GaN film without contaminants regardless of illumination. Illumination and Ga cell temperature changed the texture of the polycrystalline GaN from (0001)∥(100) to (0001)∥(111) and back again. Near single crystal films were deposited with an orientation relationship of w-GaN (0001)∥β-SiC (100) and (101̄0)∥(011̄). Resulting films were characterized by scanning electron microscopy as well as x-ray and electron diffraction.
Compact and inexpensive quartz capillaritron source
Authors: Bautsch Markus , Varadinek Patrik , Wege Stephan , Niedrig Heinz
Published: July 2002

A new durable and reliable capillaritron source for ion and atom beams with particle energies in the range between 1 and 15 keV has been designed using very few and inexpensive components. The quartz capillaritron source may be used for ion and atom beam generation or it can operate as a complete sputter deposition system. The energy spread of argon ions can be adjusted below 10% of the maximum energy of the ions (i.e., 200 eV for 3 keV argon ions). The portion of ions in the particle beam could be varied from 0% to 40%.
Fluorocarbon high-density plasmas. I. Fluorocarbon film deposition and etching using CF4 and CHF3
Authors: Oehrlein G. S. , Zhang Y. , Vender D. , Haverlag M.
Published: July 2002

Fluorocarbon film deposition in discharges used for oxide etching plays a key role in determining the profile shape of contact holes and the etch selectivity with respect to the mask and the underlayer. For low-density capacitatively coupled rf discharges this deposition is due to neutral radicals. We report a study of fluorocarbon film deposition and etching phenomena in electron cyclotron resonance (ECR) discharges of CF4 and CHF3. Plasma operation without rf sample bias in the pressure range below 10 mTorr results in the deposition of fluorocarbon films for both gases, with the highest deposition rate in each case at 2 mTorr (≂120 nm/min for a 1000 W CF4 plasma and ≂180 nm/min for CHF3 using the same conditions). For CF4 this behavior differs dramatically from that seen for conventional rf diode plasmas where no deposition occurs. The deposition is due to the more efficient breakdown and ionization of CF4 and CHF3 in the ECR discharge and the lack of energetic ion bombardment of the substrate as compared to capacitatively coupled rf diode plasmas. We have used a double grid ion energy analyzer in front of a silicon wafer being ellipsometrically sampled to unambiguously demonstrate that in these high-density discharges, fluorocarbon deposition is primarily due to bombardment with low energy ions. The fluorocarbon growth rate dropped by a factor of 5 if positive biasing of the grid prevented ions from reaching the fluorocarbon film surface in a CHF3 plasma at 2 mTorr.

The energy distribution of the ions which may be obtained from these data is in good agreement with measurements of the plasma potential. The ion fluxes for CF4 are ≂4–5 times greater than the fluorine and carbon atom fluxes required to explain the deposition rates (assuming a sticking coefficient of 1). Film-growth due to direct ion incorporation rather than ion enhancement can explain the experimental results. For CHF3 plasmas the deposition rates are ≂100 nm/min greater than for CF4 for all conditions. This suggests that neutrals contribute strongly to fluorocarbon film growth for CHF3 since the ion currents are nearly the same as for CF4. The ion enhancement effect of film growth rate decreases at higher pressure and lower microwave powers and mirrors the behavior of the ion current. This finding has important implications for etch selectivity, etching profiles, and the slow-down of the SiO2 etch rates in high-aspect ratio contact holes. Biasing the substrate reduces the net fluorocarbon deposition rate for low rf bias values. At higher rf bias values, etching of the initially deposited film takes place. These threshold voltages for etching are higher for CHF3 than CF4, e.g., 55 versus 35 V for 1 mTorr operation. Oxide etching can only take place for rf bias values equal or greater than these threshold voltages.
Surface reconstructions of (001) CdTe and their role in the dynamics of evaporation and molecular-beam epitaxy growth
Authors: Tatarenko S. , Bassani F. , Klein J. C. , Saminadayar K. , Cibert J. , Etgens V. H.
Published: July 2002

We present studies of the surface reconstruction and chemical analysis of the uppermost atomic layer of thick and thin (001) CdTe layers grown on (001) CdTe and ZnTe by (MBE). Techniques include reflection high energy electron diffraction and x-ray photoelectron spectroscopy (XPS). All the surfaces obtained in the temperature range used (220–300 °C) in MBE are Cd covered with about 50% of undimerized Cd atoms; the peak of the Cd surface is clearly identified by XPS on thin CdTe layers. The surfaces can be (2×1), c(2×2) or (2×1)+c(2×2) reconstructed. Heating these surfaces above 300 °C leads to a (2×1) Te-stabilized surface. A reversible transition occurs between this last surface and the mixed (2×1)+c(2×2) structure: thermal cycling between these two reconstructed surfaces induces the evaporation of half a monolayer per cycle. Tentative models to account for the results are presented and correlation between these results and the properties of the MBE layers is discussed.
Amorphous nitrogenated carbon films: Structural modifications induced by thermal annealing
Authors: Freire F. L. , Achete C. A. , Mariotto G. , Canteri R.
Published: July 2002

Hard amorphous nitrogenated carbon films [a-C:H(N)] deposited by self-bias glow discharge were annealed in vacuum in the temperature range of 300–800 °C. The annealing time was 30 min. The structural and compositional modifications induced by thermal annealing were followed by several analytical techniques: secondary ion mass spectrometry (SIMS), Raman spectroscopy, Rutherford backscattering spectrometry, elastic recoil detection (ERDA), and nuclear reaction analysis. The internal stress of the films was also measured. Nuclear analyses indicate that both nitrogen and hydrogen losses occur for annealing temperatures higher than 300 °C. ERDA and SIMS results suggest that hydrogen and nitrogen out-diffusion occurs by molecular transport through an interconnect network of voids. In the same temperature range, Raman scattering reveals an increase of the number and/or the size of the graphite domains. Internal stress is compressive for the as-deposited films and changes to tensile for samples annealed at 800 °C, indicating the progressive graphitization of films. A comparison with amorphous carbon films (a-C:H) is also made.
Damage and contamination in low-temperature electron cyclotron resonance plasma etching
Authors: Whang Ki-Woong , Lee Seok Hyun , Doh Hyun-Ho , Kim Jae Seong
Published: July 2002

An electron cyclotron resonance (ECR) plasma etching system has been built to study the damage and contamination inherent to the high density ECR etching. The temperature of the substrate can be lowered to −150 °C by the backside cooling of the substrate with the liquid-nitrogen cooled helium. The substrate temperature during etching was monitored by a sheathed thermocouple and IR laser interference thermometry. Gate polysilicon etching by SF6 plasma had been carried out and the effect of the substrate temperature on the anisotropy, selectivity, and etch rate was examined with special emphasis on the damage and contamination incurred by the plasma etching. Secondary ion mass spectroscopy (SIMS) analysis shows that the depth of the contaminated layer decreases when the substrate temperature is lowered to −120 °C. Also, the measurement of the gate oxide breakdown voltage shows much less oxide damage when the substrate temperature is lowered during ECR etching.
Comparative study of the internal structures of Kevlar and spider silk by atomic force microscopy
Authors: Li S. F. Y. , McGhie A. J. , Tang S. L.
Published: July 2002

Atomic force microscopy was used to study the internal structures of Kevlar(R) 49 fibers and spider dragline silk from the microtomed sections of the fibers. Both fibers exhibited fibrillar structures. For Kevlar(R), the fibrils were aligned along the fiber axial direction, tightly packed and braided. In addition, a prominent skin layer was present. For the dragline silk, pleated fibrils that were unfolded upon extension were observed in the core region. The skin appeared to be very thin. These structural features correspond well with the mechanical properties of these high-strength fibers.
Microprofile simulations for plasma etching with surface passivation
Authors: Hamaguchi S. , Dalvie M.
Published: July 2002

A numerical algorithm and simulation results are presented for microscopic profile evolution of material surfaces subject to plasma etching (reactive-ion etching) and surface passivation. Surface evolution is calculated by the shock-tracking method, which accurately simulates formation and evolution of facet corners. The angle distribution for the reemission of sputtered materials is assumed to follow an arbitrary cosine law (i.e., ∝cosβ Θ, with Θ being the reemission angle and β≳0). Thickness of sidewall passivation layers and resulting etched profiles are shown to depend sensitively on both the reemission angular distribution and the sticking coefficient.
Coupling of radio-frequency bias power to substrates without direct contact, for application to film deposition with substrate transport
Authors: Smith Donald L. , Alimonda Andrew S.
Published: July 2002

We have demonstrated the coupling of 13.56 MHz rf bias power to an electrically floating substrate platform during aluminum sputter deposition by using an rf-driven electrode spaced 3 mm away from the back of the platform. This electrode gap and the sputtering plasma sheath in series with it form a capacitive voltage divider, so that the peak rf voltage on the platform is 350 V when that on the electrode is 750 V. This amount of coupling produced enough ion bombardment on the aluminum to result in 23% resputtering and an improvement in film sidewall coverage from 10% to 100%. This noncontact, ‘‘proximity’’ method of substrate biasing should greatly facilitate the coupling of rf power into moving substrates in transport-type deposition processes.
Measurement of complete Auger electron emission angular distributions from β-SiC films on Si(100)
Authors: Chyan Oliver M. R. , Frank Douglas G. , Hubbard Arthur T. , Li J. P. , Steckl Andrew J.
Published: July 2002

The structure of epitaxial β-SiC thin films grown on Si(100) has been investigated by measuring Auger electron emission angular distributions over an essentially complete hemisphere of angles of emission above the film surface. The β-SiC films were grown by rapid thermal chemical vapor deposition, in which the heated Si(100) surface was carbonized with propane. Auger emission angular distributions were measured for carbon at 268 eV, and for silicon at 86 and 1605 eV, allowing the film structure to be probed from the viewpoint of each element. The Auger measurements probe the film structure to a depth of several atomic layers. Each of the distributions displayed distinct, fourfold symmetric features, demonstrating the crystalline character of the β-SiC films. Comparison of the measured angular distributions with geometric projections and simulations for the known β-SiC structure indicates that the films consist of interspersed [100] crystalline domains (each domain having twofold symmetry), with 90° in-plane rotational orientations between domains. These findings are consistent with scanning tunneling microscopy observations of the outermost atomic layer.
In situ bend fixture for deformation and fracture studies in the environmental scanning electron microscope
Authors: Kalnas C. E. , Mansfield J. F. , Was G. S. , Jones J. W.
Published: July 2002

A computer controlled loading fixture has been designed to allow in situ observation of fracture processes during bending deformation of metal/ceramic microlaminates in an electroscan environmental scanning electron microscope (ESEM). The stage has the capability of accommodating either three- or four-point bending experiments. A unique design feature of the stage is that the specimen surface remains at a fixed distance from the secondary electron detector and, hence, in focus during bending. The sample rests on the fulcrum which remains in a fixed position while the restraints that grip the ends of the sample descend on a ball slide. The system is controlled by a Macintosh IIci computer and National Instruments NB-MIO-16L-9 data acquisition card. National Instruments LabVIEW(R)2 software is used to control the stage displacement and to record the load cell and transducer outputs. The operation of this instrumentation in the ESEM is illustrated by the study of fracture processes in ceramic and ceramic/metal microlaminate films deposited on ductile metallic substrates.
Fluorocarbon high density plasmas. VIII. Study of the ion flux composition at the substrate in electron cyclotron resonance etching processes using fluorocarbon gases
Authors: Kirmse Karen H. R. , Wendt Amy E. , Oehrlein Gottlieb S. , Zhang Ying
Published: July 2002

An important component in the basic chemical and physical mechanisms which govern etching and deposition processes in high density plasmas is the chemical identity and relative fluxes of ionic species at the substrate surface. Here we report line of sight measurements of relative ion fluxes made with a quadrupole mass spectrometer through an orifice in the substrate holder of an electron cyclotron resonance reactor configured for fluorine-based etching. The relative ion fluxes versus microwave power and pressure for CF4 and CHF3plasmas have been studied. These data have been compared with Si and SiO2 etch rates to determine the effect of ion flux composition changes on etching processes. It was observed that the F+ ion flux increases relative to the fluorocarbon ion fluxes as the microwave power is increased or the chamber pressure is decreased. This relative increase in the F+ ion flux may be caused by the increased dissociation of the source gas. Changes in the ion flux composition seem to have little effect on the Si and SiO2 etch rates. It was also observed that the F+ ion flux increases as the percentage of hydrogen in a CHF3/H2plasma is increased while the neutral fluorine optical emission intensity decreases for the same conditions. The data suggest that for these conditions dissociative ionization reactions involving fluorine containing molecules make a significant contribution to the production of F+, in addition to the ionization of neutral fluorine.
In situ x-ray reflectivity measurements of thin film structural evolution
Authors: Chason Eric , Chason Marc
Published: July 2002

X-ray reflectivity using energy dispersive x-ray detection has been used to investigate the characteristics of vacuum-deposited thin films. A resolution of 0.3 nm for thicknesses in the range 3–200 nm and of 0.05 nm for roughness in the range 0.1–3 nm has been demonstrated. Furthermore, it is shown that by using energy dispersive detection, spectra can be obtained in less than 500 s allowing real time studies to be performed. Thin, discrete Cr/Al deposits on quartz substrates have been investigated, and the presence of a 1.5 nm thick Al/Cr intermetallic layer formed during room-temperature deposition has been determined. During annealing at 250 °C, the Cr layer thickness decreases linearly with time until approximately 4 nm is consumed in additional intermetallic formation; further annealing does not change the Cr layer thickness.
Multilayer, multicomponent, and multiphase physical vapor deposition coatings for enhanced performance
Authors: Sproul William D.
Published: July 2002

Hard physical vapor deposition (PVD) coatings are widely used today for enhanced performance, and PVD hard coatings have evolved because they can be deposited at temperatures much lower than those commonly needed for the chemical vapor deposition of coatings. Although binary coatings such as TiN are still very popular and are tried in many different applications, new multilayer, multicomponent, or multiphase coatings are finding successful applications. Multicomponent coatings such as TiAlNx or Ti(C,N) are better than TiN in certain tooling applications, and Ti0.5Al0.5N makes an excellent diffusion barrier in microelectronic devices. Reactively deposited coatings such as MoNx, CrNx, and NbNx all form multiple phases, and either individual phases or mixed phases of these materials are now being tested for tribological applications. Many nitride coatings such as β-Mo2N can extend the rolling contact fatigue life of rolling elements such as bearings by a factor of 5 or more. Multilayer polycrystalline TiN/NbN superlattice films have shown hardness as high as 5200 kgf mm−2, and other new superlattice films such as TiN/Ni are being developed. Although many of these new coatings will be tried on tools, the future for them lies beyond tooling. The ability to deposit these new coatings at low substrate temperatures without damaging the properties of the substrate, which can be done with plasma assisted PVD processes, will open up many new tribological and microelectronic applications.
High quality ZnO thin films on InP substrates prepared by radio frequency magnetron sputtering. II. Surface acoustic wave device fabrication
Authors: Chang S. J. , Su Y. K. , Shei Y. P.
Published: July 2002

ZnO/InP based surface acoustic wave (SAW) devices were successfully fabricated. High quality ZnO films were first deposited onto InP substrates by radio frequency magnetron sputtering, and the SAW devices were fabricated on top of ZnO. It was found that the characteristics of the SAW devices depend strongly on the quality of the ZnO thin films and thus on the ZnO deposition parameters. To obtain a low loss SW device, one must have a high quality ZnO thin film. With a type I pattern, we found that the minimum insertion loss is 34 dB. Inserting counter electrodes can further reduce the insertion loss to 23 dB.
Evidence of a simple cubic phase in electron beam vacuum evaporated indium–oxide on a glass substrate
Authors: Abbas M. , Qazi I. A. , Samina A. , Masaood M. , Majeed A. , ul Haq A.
Published: July 2002

Indium oxide normally exists in the body-centered-cubic structure. With thin films of the compound, deposited on a glass substrate by the electron beam vacuum evaporation technique, x-ray diffraction results indicate a simple cubic structure for some films.
Study of microdroplet generation from vacuum arcs on graphite cathodes
Authors: Kandah Munther , Meunier Jean-Luc
Published: July 2002

The emission of microdroplets from the cathode surface in the vacuum arc ion plating deposition technique is the major drawback to the technique’s industrial use. The generation of these particles from graphite cathodes is studied in this article and correlated to the local thermal load in the cathode spot area. A pulse discharge was used for a precise control of this load. Increases in the arc current level, arc duration time, and, more generally, the local temperature of the cathode were found to increase the number and the average size of the emitted particles. Particles under these conditions also show an increase in the width of their size distributions. Increasing the distance between cathode and substrate was found to decrease the number density of particles observed on the substrate according to the solid angle covered. The microdroplets show a graphite structure and diameters between 0.2 and 2.0 μm. Conditions needed to decrease the number of particles emitted to the substrate are given.
X-ray photoelectron spectroscopy study of the difference between reactively evaporated and direct sputter-deposited TiN films and their oxidation properties
Authors: Prieto P. , Kirby R. E.
Published: July 2002

X-ray photoelectron spectroscopy (XPS) is used to study carefully prepared oxide-free titanium nitride (TiN) films of nearly identical stoichiometry, grown by direct sputtering and reactive evaporation. The line shapes and peak positions of the Ti 2p and N 1s transitions are dependent upon the deposition method. The XPS results showed that oxynitrides are present following exposure of either type of film to dry oxygen; however, reactively evaporated films have a considerably higher oxidation rate. Differences in valence band and electron energy loss spectroscopy (EELS) spectra are correlated with the changes observed in the core levels. The EELS spectra detected the presence of a low energy loss, which is correlated with the TiN electron density of states closest to the Fermi level. The secondary electron emission yields for reactively evaporated TiN were also measured before and after dry oxygen and air exposure, and after heating. The maximum yields are about 10% lower for reactively evaporated films than for similarly treated previously measured sputter-deposited layers.
Low resistivity ohmic contacts to moderately doped n-GaAs with low-temperature processing
Authors: Lovejoy Michael L. , Howard Arnold J. , Zavadil Kevin R. , Rieger Dennis J. , Shul Randy J. , Barnes Peter A.
Published: July 2002

A low-temperature process for forming ohmic contacts to moderately doped GaAs has been optimized using a PdGe metallization scheme. Minimum specific contact resistivity of 1.5×10−6 Ω cm2 has been obtained with a low anneal temperature of 250 °C. Results for optimizing both time and temperature are reported and compared to GeAu n-GaAs contacts. Material compositions were analyzed by x-ray photoelectron spectroscopy and circuit metal interconnect contact resistivity to the low-temperature processed PdGe contacts is reported. For the lowest-temperature anneals considered, excess Ge on the ohmic contact layer is suspected of degrading interconnect metal contacts, while higher-temperature anneals permitted interconnect metal formation with negligible contact resistivity. Atomic force microscopy measurements showed that the PdGe surface morphology is much more uniform than standard GeAu contacts.
Amorphous oxygen-containing hydrogenated carbon films formed by plasma enhanced chemical vapor deposition
Authors: Durrant Steven F. , Castro Sandra G. , Cisneros Jorge I. , da Cruz Nilson C. , Bica de Moraes Mário A.
Published: July 2002

Films were deposited from glow discharge plasmas of acetylene–oxygen–argon mixtures in a deposition system fed with radio frequency power. The principal variable was the proportion of oxygen in the gas feed, Xox. The chemical structure and elemental composition of the films were investigated by transmission infrared spectrophotometry and x-ray photoelectron spectroscopy. Optical properties—refractive index, absorption coefficient, and optical gap—were determined from transmission ultraviolet-visible spectroscopy data. The latter also allowed the determination of film thicknesses and hence deposition rates. It was found that the oxygen content of the films and, within limits, the refractive index are controllable by the selection of Xox.
Thin polymer films prepared by radio frequency plasma sputtering of polytetrafluoroethylene and polyetherimide targets
Authors: Hishmeh G. A. , Barr T. L. , Sklyarov A. , Hardcastle S.
Published: July 2002

Plasma polymerization is a common technique used for the deposition of thin polymer films. Radio frequency (rf) sputtering may also be employed for plasma polymerization with the principal difference being the introduction of fragmented polymer species (for the latter) rather than gaseous monomer species into the plasma. The thrust of this work is to study the integrity of thin films prepared by rf plasma sputtering of two substantially different polymer systems. Polytetrafluoroethylene (PTFE) has a simple linear chain molecular structure and is noted for its lubrication and nonwetting properties. Conversely, polyetherimide (PEI) possesses a complex ring molecular structure and is known for its dielectric strength and high temperature stability. The techniques utilized to characterize the films were x-ray photoelectron spectroscopy (XPS), DRIFT, UV–Visible, x-ray diffraction, and scanning electron microscopy (SEM). Periodic controlled ion sputter treatment during XPS analysis of both virgin and sputtered deposited films was also found to be a method of inducing simulations of some of the effects of sputter-deposited growth. Thin films prepared from targets of both polymers were found to be amorphous. DRIFT observations showed a dismantling of the PEI molecule with a total elimination of C=O and C—O groups, and fracturing of the imide group. The retention of some benzene groups, with a partial aromatic to aliphatic transition was also observed. These results were supported by XPS findings. Conversely, PTFE films were found to contain CH, CF, CF2, and CF3 structural units like those found in plasma polymerized PTFE films. After nominal sputter treatment, the CH, CF2, and CF3 species were significantly removed while the CF content appeared to increase, indicative of damage from ion beam exposure. For PEI films, further rearrangement of the C(1s), O(1s), and N(1s) peak structures occurs from ion beam exposure resulting in the formation of C and N variants. While PTFE films are similar to their parent material, observations of rf sputtered PEI indicate a very different type of film formation.
Basis for the structure sensitivity of the CO+NO reaction on palladium
Authors: Vesecky S. M. , Rainer D. R. , Goodman D. W.
Published: July 2002

The structure sensitive reaction, CO+NO, has been studied on two crystal planes of palladium. The Pd(111) surface was found to be approximately five times more active than Pd(100) for NO reduction by CO. This structure sensitivity is attributed primarily to the stabilization of molecularly adsorbed NO (NOa) relative to Na on Pd(111) vs Pd(100). It has also been found that the Pd(100) surface is more effective at dissociating NOa than Pd(111). As a result, Pd(100) yields a higher ratio of N2/N2O compared to Pd(111). Pd(100), however, also stabilizes atomic nitrogen on the surface, resulting in the poisoning of subsequent NO adsorption/dissociation and thus inhibiting the overall CO+NO reaction.
Highly transparent and conductive ZnO–In2O3 thin films prepared by atmospheric pressure chemical vapor deposition
Authors: Minami T. , Kumagai H. , Kakumu T. , Takata S. , Ishii M.
Published: July 2002

Highly transparent and conductive ZnO–In2O3 films have been prepared by atmospheric pressure chemical vapor deposition using Zn(C5H7O2)2, In(C5H7O2)3, and H2O as Zn, In, and O source materials, respectively. The obtained minimum resistivity of polycrystalline In2O3 or ZnO films deposited on glass substrates at a temperature of 350 °C using In(C5H7O2)3 or Zn(C5H7O2)2 and H2O, respectively, was 10−2–10−1 Ω cm. The resistivity of ZnO–In2O3 films deposited at 350 °C was strongly dependent on the chemical composition (Zn content) of the films. A resistivity of 4×10−4 Ω cm and an average transmittance above 85% in the visible range were obtained in an amorphous ZnO–In2O3 film with a Zn content (Zn/(In+Zn) atomic ratio) of 0.25.
Tritium permeation and inventory in an international thermonuclear experimental reactor divertor
Authors: Shu W. M. , Watanabe K.
Published: July 2002

An analytic model taking account of multiple structures and temperature gradient was developed for tritium permeation and inventory in an international thermonuclear experimental reactor divertor. It was applied to calculate the tritium permeation and inventory in Be/Cu and W/Cu options of the divertor components. The total tritium permeation and mobile inventory in the Be/Cu option were calculated to be 0.81 mg/s and 6.0 kg, and those in the W/Cu option were 0.0071 mg/s and 6.7 g. The mobile inventory in the Be/Cu option decreases with increasing operation time, while that in the W/Cu option decreases initially and then increases.
Quenching of electron temperature and electron density in ionized physical vapor deposition
Authors: Dickson M. , Qian F. , Hopwood J.
Published: July 2002

The addition of sputtered metal atoms to a high density plasma results in the ionization of the metal species. The ionized physical vapor deposition technique allows the deposition of metal films from ionic species and is a potential method for the fabrication of integrated circuits with high aspect ratio interconnect features. Maximizing the temperature and density of the plasma electrons is important to optimizing the ionization of metal. The present work reports that the electron temperature and electron density of the plasma decrease with increasing metal density. Direct measurement of electron temperature quenching using a rf compensated Langmuir probe demonstrates a ∼20% decrease in electron temperature due to metal additions of ∼1012 atoms/cm3. The electron density is determined using microwave interferometry and decreases by ∼15% as metal atoms are added to the discharge. A fixed temperature global model, however, indicates that thermalized metal atoms should increase the electron density. Gas heating due to energetic sputtered neutrals is shown to be responsible for the observed decrease in electron density.
In situ measurements of temperature-dependent strain relaxation of Ge/Si(111)
Authors: Deelman P. W. , Schowalter L. J. , Thundat T.
Published: July 2002

We have measured strain relaxation and clustering in Ge films grown by molecular beam epitaxy on Si(111) at substrate temperatures between 450 and 700 °C in real time with reflection high energy electron diffraction (RHEED). At 450 °C, we observe an oscillation of the surface lattice constant for the first 3.5 bilayers [(BLs) thicknesses were calibrated by Rutherford backscattering spectrometry], followed by a sharp two-dimensional–three-dimensional (2D–3D) growth mode transition, when transmission diffraction features appear in RHEED. The surface lattice constant then begins to relax at an initial rate of about 0.5%/BL. The mechanisms of island growth and strain relaxation change with growth temperature. At 500 °C, the surface lattice constant begins to relax after only 1 BL, and at 550 °C relaxation begins immediately. At both temperatures, however, 3D spots do not appear until after 3.5 BL. The initial rate of strain relaxation decreases with increasing temperature until, at 700 °C (when 3D spots never appear), it is only 0.04%/BL. This behavior may be explained by a temperature-dependent roughness length scale. At low temperature, atomic force microscope images show the development of small (∼1000 Å), faceted islands with aspect ratios (height/width) on the order of 0.07. With increasing temperature, the formation of well-defined facets is inhibited. At 700 °C, islands grow very large from the outset, with aspect ratios less than 0.015. The islands are unable to thicken much, because dislocations can glide in easily at the edges, enabling the islands to grow laterally quickly. The strain in the “new” islands is not substantially less than that in the “old” islands. At the highest temperatures used, diffusion becomes a relevant mechanism for strain relief.
Chemistry of cyclopentadiene on a Cu(100) surface: Detection of cyclopentadienyl (C5H5) species as reaction intermediates
Authors: Sun D.-H. , Bent B. E. , Chen J. G.
Published: July 2002

The desorption and reaction of cyclopentadiene on Cu(100) were studied by temperature-programmed desorption and Auger electron spectroscopy. The dehydrogenation of cyclopentadiene is significant at low exposures (⩽0.8 L), producing cyclopentadienyl (C5H5) species as a reaction intermediate at ⩽335 K. The C5H5 groups are stable on the Cu(100) surface up to ∼600 K. At higher temperatures, cyclopentadienyl species undergo a self-hydrogenation reaction, with two-thirds of the C5H5 groups obtaining H from the others, and desorb from the surface as cyclopentadiene (C5H6) at ∼620 K. The remaining one-third of the C5H5 groups dehydrogenates to form hydrocarbon fragments that can be best described as C5H3 species, which further decompose to produce residue surface carbon and molecular H2 at ∼700 K. The implication of the current work to the previous observation of carbon contamination in the chemical vapor deposition of Cu is also discussed.
How to distinguish the Raman modes of epitaxial GaN with phonon features from sapphire substrate—Comments on “Optical properties of GaN film grown by metalorganic chemical vapor deposition” [J. Vac. Sci. Technol. A 14, 840 (1996)]
Authors: Feng Zhe Chuan , Schurman Matthew , Stall Richard A.
Published: July 2002

We present correct assignments to the Raman spectrum of an epitaxial hexagonal GaN film grown on (0001) sapphire, published by Zhang et al. [J. Vac. Sci. Technol. A 14, 840 (1996)]. These assignments are supported by our additional polarization and incident angle-varied Raman measurements. A method to distinguish the Raman features of the epitaxial GaN thin layer from those of the sapphire substrate is presented.
Mechanical and fracture toughness studies of amorphous SiC–N hard coatings using nanoindentation
Authors: Scharf Thomas W. , Deng Hong , Barnard John A.
Published: July 2002

a: SiC x – N y films were deposited on Si(111) and sapphire substrates at ambient temperatures by reactive magnetron sputtering of SiC in a mixed Ar/N2 discharge. Nanoindentation was used to characterize the mechanical (hardness and elastic modulus) and fracture (toughness) properties. A conventional sharp Berkovich diamond indenter (three-sided pyramid) was used to assess the mechanical properties. The hardness and elastic modulus slightly increased from 23 and 220 GPa to 27 and 270 GPa with incorporation of N2 (up to 4.4%). The fracture toughness (Kc) was characterized by replacing the aforementioned indenter with a cube corner indenter, which also is trigonal but has the geometry of a cube corner with a smaller angle between the axis of symmetry and a face. The purpose of the switch was to reduce the much higher cracking thresholds associated with the Berkovich and Vickers indenters. The smaller volume of thin films requires this reduction for reliability. The nucleation and propagation of median-radial indentation cracks was made feasible by the cube corner geometrically displacing more volume than the Berkovich under similar loads. A substrate fracture toughness effect was observed dependent upon indenter penetration depth. Fracture toughness was relatively constant (≈3.1 MPa√m) from 19 (threshold load) to 40 mN; however, loads ⩾50 mN resulted in a decrease to ≈2.4 MPa√m since the greater penetration depths approaching the sapphire substrate played a role. The structure, composition, and bonding of the films were qualitatively and quantitatively assessed by x-ray diffraction, energy dispersive x-ray spectroscopy, and micro-Raman spectroscopy, respectively, and subsequently correlated to the overall film properties.
Energy spectra of secondary neutrals obtained by means of the electrostatic energy filter of a commercial low-pressure HF-plasma secondary neutral mass spectrometer
Authors: Jenett Holger , Hodoroaba Vasile-Dan
Published: July 2002

The ion optics system of the commercially available HF-plasma secondary neutral mass spectrometry apparatus INA3 was found to enable ion energy spectroscopy with good performance: for sufficiently high (2 keV) primary ion energies, the energy distributions of postionized Cu, Al, and Mo atoms almost show the theoretically expected behavior up to 300 eV. Maxima are found at the energies expected from collision cascade emissions. Since ionization occurs on a plasma potential between +35 and 40 V, all ion energies are shifted accordingly. Tuning of the ion optics was accomplished in the secondary ion mass spectroscopy mode by using a sputtered H3BO3/Cu powder pellet as a B+ and BO2− ion source.
High rate reactive dc magnetron sputter deposition of Al2O3 films
Authors: Kharrazi Olsson M. , Macák K. , Helmersson U. , Hjörvarsson B.
Published: July 2002

Aluminum oxide films were produced by reactive dc magnetron sputtering of Al in Ar+O2. The composition of the films was characterized by Rutherford backscattering measurements. Stoichiometric films possessed excellent optical properties with a refractive index of ∼1.6 for visible and near-infrared light. It was possible to produce stoichiometric films while keeping the target in the metallic mode of operation; the resulting deposition rate was 23 nm min−1, as compared to 0.95 nm min−1 for films grown from an oxidized target. An O/Al arrival rate ratio exceeding ∼17 was required for stoichiometric films to be grown at room temperature. The success of the present high-rate deposition strategy hinges on the use of a suitable deposition system geometry — including a large target-to-substrate distance and a small target size — and on the use of sufficient Ar pressure. Monte Carlo simulations are presented; they can be reconciled with our empirical data.
A plasma-polymerized protective film for transmission electron microscopy specimen preparation by focused ion beam etching
Authors: Kato N. I. , Miura N. , Tsutsui N.
Published: July 2002

Focused ion beam (FIB) milling has been widely used for the preparation of cross-sectional transmission electron microscopy (X-TEM) specimens. In FIB fabrication, a protective layer is normally formed on the specimen surface by ion-beam-assisted metal deposition to avoid the damage caused by highly accelerated ion beams. However, the metal deposition itself induces damage in the specimen. This problem is especially serious when the region near the surface of a specimen is of interest. Investigation of subsurface damage through X-TEM observations showed that, for 30 keV FIB, the defects induced by ion-beam-assisted deposition extend about 400 Å from the surface. In the case of single-crystalline silicon, a several-hundred-angstrom layer just below the surface is converted into an amorphous layer. We propose the use of a plasma-polymerized organic film which is formed by plasma polymerizing of methane and ethylene, instead of the metal deposit. We used the film as a protective layer and fabricated TEM specimens without damaging the fine subsurface structures. In the case of single-crystalline silicon, no amorphous layer was observed. In addition, a subsurface structure in an aluminum sample prepared by the FIB method was successfully observed by TEM.
Preparation of (001) cube textured CeO2 buffer layers on rolling-textured substrates by ion beam assisted pulsed laser deposition
Authors: Xiong X. M. , Wang R. P. , Zhou Y. L. , Guo X. X. , Lu H. B. , Pan S. H. , Yang G. Z. , Liu C. F. , Wu X. , Zhang X. P. , Zhou L.
Published: July 2002

An approach to deposit (001) oriented, in-plane-aligned CeO2 buffer layer on rolling-assisted biaxially-textured nickel tapes by ion beam assisted deposition is reported. The CeO2 films grown on the rolling-textured nickel tapes by pulsed laser deposition without ion bombardment show (111) orientation. CeO2 films grown on the rolling-textured nickel tapes by ion beam assisted pulsed laser deposition without introducing hydrogen are (001) oriented at deposition temperature below about 380 °C. The full width at half maximum of (111) φ-scan of the (001) cub textured CeO2 films is 9°. The films growing at higher temperature are (111) orientation, no matter they are deposited with ion bombardment or without ion bombardment.
Energetic ion bombardment of SiO2 surfaces: Molecular dynamics simulations
Authors: Abrams Cameron F. , Graves David B.
Published: July 2002

Numerous profile evolution simulation studies strongly suggest that ions reflecting with glancing angles from etched feature sidewalls are responsible for microtrench formation at the feature bottom. Within these studies such reflections are traditionally assumed specular, where the ion retains all of its incident energy. In this study, we gauge the validity of that assumption by describing the distributions of reflected ion energies, Er, reflected ion angles (polar, θr; azimuthal, φr; and total scatter, αr), obtained via MD simulations of Ar+ bombardment of model SiO2 surfaces. We modeled the physics of the surface atom interactions using an empirical interatomic potential energy function developed by Feuston and Garofalini [J. Chem Phys. 89, 5818 (1988)]. We considered Ar+ ion energies, Ei, of 100 and 200 eV, and incident polar angles, θi, of 0°, 30°, 45°, 60°, 75°, and 85°, measured from the macroscopic surface normal. Each (Ei,θi) combination was used to generate a unique roughened model oxide surface by repeated ion bombardment of an initially crystalline configuration. We observed that the degree to which a surface is roughened (as measured by the fractal dimension of the surface height distribution function, Δbc[h]) is a weak function of bombarding ion incident angle for angles less than 85°. We discuss the sensitivity of the (Er,θr,φr) distributions to incident ion energy and angle, and to roughness characteristics of the target surface. We compare the reflection data to the predictions of the binary collision model. We report sputter yields as functions of incident angle and energy, and discuss the distributions in energy of the sputtered products. We discuss the implications of the reflection distributions and surface character for feature scale simulation.
Ni content and grain size dependency of perovskite structure La0.8Sr0.2Co1−xNixO3−δ thin films for CO gas sensor
Authors: Chiu C. M. , Chang Y. H.
Published: July 2002

La 0.8 Sr 0.2 Co 1−x Ni x O 3−δ perovskite films prepared by the radio frequency sputtering technique in a wide range of Ni content (x⩽0.6) were studied. The microstructure of the films determined by scanning electron microscopy showed the changing of grain size after heat treatment at different temperature for 5 h. The effect of Ni doping on the sensitivity to CO was studied. The La0.8Sr0.2Co0.6Ni0.4O3−δ film treated at 700 °C for 5 h shows the best improvement of sensitivity to CO. The CO–O2 reaction on the surface of film can be indirectly probed by electron spectroscopy for chemical analysis. The sensitivity dependence affected by grain size is also investigated. The combination of binding energy to the adsorbed oxygen and the connecting condition of the adjacent grains would dominate the sensing property. The results, show the La0.8Sr0.2Co0.6Ni0.4O3−δ film treated at 700 °C for 5 h yields the maximum sensitivity of 10.1% in 50 ppm of CO.
Effects of Ar dilution on the optical emission spectra of fluorocarbon ultrahigh-frequency plasmas: C4F8 vs CF4
Authors: Nakano Toshiki , Samukawa Seiji
Published: July 2002

The Ar dilution effects on the ultrahigh-frequency (UHF) plasmas through C4F8 and CF4 are studied by optical emission spectroscopy and Langmuir probe measurement. For the C4F8 plasma, the Ar dilution is found to extend the electron energy distribution function (eedf) toward the higher energy and increase the electron density, ne. The ne-normalized CF2 emission intensity is decreased proportionally with the partial pressure of the C4F8 feedstock gas. Thus, the Ar dilution increases the ratio of the ion density to the CF2 density, which changes the balance between the etching and the polymer deposition and affects the SiO2 etching characteristics significantly. The polymer deposited on the reactor wall is found to affect the emission spectra of the C4F8 plasma. For the CF4 plasma, the Ar dilution does not change the eedf probably because of approximately the same threshold energy for the ionization processes between Ar and CF4. However, the Ar dilution increases the ne in the CF4/Ar plasma. Since CF2 radicals are inferred to be the higher order dissociation products of CF4 molecules, the increased ne results in the enhanced production of CF2 radicals. Approximately the same ratio of the ion density to the CF2 density in the CF4/Ar plasma as that in the C4F8/Ar plasma suggests that in the SiO2 etching process by high-density, low-pressure plasmas, the CF4/Ar plasma chemistry can be a substitution for the C4F8/Ar plasma chemistry.
Evidence for germanium phosphide dots on Ge(001)
Authors: Bottomley D. J. , Iwami M. , Uehara Y. , Ushioda S.
Published: July 2002

The Ar ion sputtered and annealed (001) surface of a 0.2 Ω cm resistivity P doped Ge crystal has been investigated in ultrahigh vacuum using scanning tunneling microscopy (STM), STM light emission, x-ray photoelectron spectroscopy, Auger electron spectroscopy, and low energy electron diffraction. The preparation procedure results in an areal concentration of 1.0±0.5 at % of P, ≈70% of which is in compound form and the remainder in elemental form. The P atoms diffuse to the surface and subsurface regions during annealing to 880 K. The evidence is that the compound is most probably metallic GeP3 which forms nm scale dots on the surface, while the elemental P is most probably in the subsurface region. The existence of the metallic phase is consistent with the presence of large (∼10–100 kbar) compressive heteroepitaxial stress induced in the dots by the substrate.