bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactive-environment, hollow cathode sputtering: Basic characteristics and application to Al2O3, doped ZnO, and In2O3:Mo
Authors: Delahoy A. E. , Guo S. Y. , Paduraru C. , Belkind A.
Published: July 2004

A method for thin-film deposition has been studied. The method is based on metal sputtering in a hollow cathode configuration with supply of a reactive gas in the vicinity of the substrate. The working gas and entrained sputtered atoms exit the cathode through an elongated slot. The reactive gas is thereby largely prevented from reaching the target. The basic operation of the cathode was studied using a Cu target and pulsed power excitation. These studies included the dependence of deposition rate on power, pressure, and flow rate, film thickness profiles, and film resistivity as a function of substrate conditions. Modeling was conducted to calculate the gas velocity distribution and pressure inside the cavity. Al2O3 films were prepared in a reactive environment of oxygen by sputtering an Al target. It was demonstrated that only a very small amount of oxygen passing through the cathode will oxidize (poison) the target, whereas large quantities of oxygen supplied externally to the cathode need not affect the target at all. A very stable discharge and ease of Al2O3 formation were realized in this latter mode. The method was applied to the preparation of transparent, conductive films of ZnO doped with either Al or B. High deposition rates were achieved, and, at appropriate oxygen flow rates, low film resistivities. High-mobility In2O3:Mo transparent conductors were also prepared, with resistivities as low as 1.9×10−4 Ω cm. Scaling relations for hollow cathodes, and deposition efficiency, and process comparisons between magnetron sputtering and linear, reactive-environment, hollow cathode sputtering are presented.
Organic molecules on zirconium surfaces
Authors: Stojilovic N. , Ramsier R. D.
Published: July 2004

In this work, the behavior of Zr(0001) exposed to benzene (C6H6) and deuterated methanol (CD3OD) is discussed. Relatively simple surface kinetics for the C6H6/Zr(0001) and CD3OD/Zr(0001) systems are observed, with only molecular desorption detected in thermal desorption experiments. We attribute this to the presence of a passivating layer of carbon formed by the initial decomposition of these species on the reactive Zr(0001) surface. Following adsorption at 150 K, benzene desorbs at about 715 K, whereas methanol desorbs near 600 K. An increase in adsorption temperature of 20 K for C6H6 and of 10 K for CD3OD lowers desorption yields significantly. An increase in surface oxygen is observed by Auger electron spectroscopy (AES) after exposure to benzene, possibly due to surface-carbon/subsurface-oxygen exchange. AES indicates that carbon stays in the near-surface region after thermal desorption, but that oxygen diffuses into the bulk in both cases.
50 nm gate electrode patterning using a neutral-beam etching system
Authors: Noda Shuichi , Nishimori Hirotomo , Ida Tohru , Arikado Tsunetoshi , Ichiki Katsunori , Ozaki Takuya , Samukawa Seiji
Published: July 2004

A 50-nm-width metal-oxide-semiconductor (MOS) gate etching process was established using a recently-developed neutral-beam etching system by optimizing the gas chemistry and the electrode bias condition. In a comparison with poly-Si gate etching using either SF6 or Cl2 gas chemistries, opposite etching characteristics were observed in the pattern profile. Consequently, the use of a mixture of these gases was proposed in order to achieve fine control of the etching profiles. The energy of the neutral beam was increased by applying a 600 kHz rf bias to the bottom electrode. The rf bias was very effective in increasing the etch rate and the anisotropy of the poly-Si gates, with no deterioration of the neutralization efficiency. The oxide leakage current achieved for a MOS capacitor etched by the neutral beam was one order of magnitude lower than that achieved by conventional plasma etching.
Coupling reactions of trifluoroethyl iodide on GaAs(100)
Authors: Singh N. K. , Kemp N. T. , Paris N. , Balan V.
Published: July 2004

We report on the reactions of 2-iodo-1,1,1-trifluoroethane (CF3CH2I) on gallium-rich GaAs(100)-(4×1), studied using the techniques of temperature programmed desorption and x-ray photoelectron spectroscopy. The study is to provide evidence for the formation of a higher fluorinated alkene, 1,1,4,4,4-pentafluoro-1-butene (CF2=CHCH2CF3) and alkane, 1,1,1,4,4,4-hexafluorobutane (CF3CH2CH2CF3) from the coupling reactions of covalently bonded surface alkyl (CF3CH2•) moieties. CF3CH2I adsorbs nondissociatively at 150 K. Thermal dissociation of this weakly chemisorbed state occurs below room temperature to form adsorbed CF3CH2• and I• species. The surface CF3CH2• species undergoes β-fluoride elimination to form gaseous CF2=CH2 and this represents the major pathway for the removal of CF3CH2• species from the surface. In competition with the β-fluoride elimination process the adsorbed CF3CH2• species also undergoes, recombination with surface iodine atoms to form recombinative molecular CF3CH2I, olefin insertion reaction with CF2=CH2 to form gaseous CF2=CHCH2CF3, and last self-coupling reaction to form CF3CH2CH2CF3. The adsorbed surface iodine atoms, formed by the dissociation of the molecularly chemisorbed CF3CH2I, and fluorine atoms formed during the β-fluoride elimination reaction, both form etch products (GaI, GaF, AsI, AsF, and As2) by their reactions with the surface layer Ga atoms, subsurface As atoms, and GaAs substrate. In this article we discuss the mechanisms by which these products form from the adsorbed CF3CH2• and I• species, and the role that the GaAs surface plays in the proposed reaction pathways. We compare the reactivity of the GaAs surface with transition metals in its ability to facilitate dehydrogenation and coupling reactions in adsorbed alkyl species.
Deposition of preferred-orientation ZnO films on the ceramic substrates and its application for surface acoustic wave filters
Authors: Chu Sheng-Yuan , Chen Te-Yi , Water Walter
Published: July 2004

Polycrystal ZnO films with c-axis (002) orientation have been successfully grown on the lead-based ceramic substrates by rf magnetron sputtering technique. The deposited films were characterized as a function argon-oxygen gas flow ratio and rf power. Crystalline structures of the films were investigated by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. Highly oriented films with c-axis normal to the substrates can be obtained by depositing under a total pressure of 10 mTorr containing 50% argon and 50% oxygen and rf power of 70 W. The phase velocity, electromechanical coupling coefficient, and temperature coefficient of frequency of surface acoustic wave (SAW) device with ZnO/IDT/PT (IDT: interdigital transducer; PT:PbTiO3 ceramics) structure were investigated. It shows that the preferred oriented ZnO film is beneficial for improving the electromechanical coupling coefficient of SAW device.
Simulation of SiO2 and Si feature etching for microelectronics and microelectromechanical systems fabrication: A combined simulator coupling modules of surface etching, local flux calculation, and profile evolution
Authors: Kokkoris G. , Tserepi A. , Boudouvis A. G. , Gogolides E.
Published: July 2004

A combined simulator linking gas flux data from a plasma reactor (experimental or simulated) to the feature profile evolution during etching/deposition processes is described. This combined simulator results from the coupling of surface etch, local flux calculation, and profile evolution modules. It is a modular tool, in the sense that different phenomena, surface models, and structures can be incorporated. In this work the combined simulator is applied in two processes: (a) in SiO2 feature etching to simulate reactive ion etching (RIE) lag and inverse RIE lag and (b) in etching of high aspect ratio Si trenches using the Bosch process. The profile evolution algorithm of the combined simulator, namely, the level set method, is applied to a process where etching and deposition occur, and tracking of two materials (Si and polymer formed during the Bosch deposition step) is needed.
Anisotropic deposition of Cu in trenches by H-assisted plasma chemical vapor deposition
Authors: Takenaka Kosuke , Kita Makoto , Kinoshita Toshio , Koga Kazunori , Shiratani Masaharu , Watanabe Yukio
Published: July 2004

We have realized anisotropic deposition of Cu, for which Cu is filled preferentially from the bottom of trenches without being deposited on their sidewall, using H-assisted plasma chemical vapor deposition. The anisotropic deposition has two interesting features. One is the fact that the narrower the width of trench, the faster the deposition rate on its bottom becomes. The other is the self-limiting characteristic, that is the deposition in the trench stops automatically just after filling it completely. Such a type of deposition has a potential to overcome common problems associated with conformal filling: namely, small crystal grain size below half of the trench width, and formation of a seam with residual impurities of relatively high concentration.
Growth of diamond film on single crystal lithium niobate for surface acoustic wave devices
Authors: Jagannadham K. , Lance M. J. , Watkins T. R.
Published: July 2004

Single crystalline lithium niobate thin films on diamond are useful for surface acoustic wave devices that operate at gigahertz frequency. The differences in the atomic bonding and crystalline structure between the lithium niobate and diamond and the high interfacial energy were responsible for formation of microcrystalline films of lithium niobate deposited on polycrystalline diamond. We have carried out growth of continuous diamond layer on single crystal lithium niobate by microwave chemical vapor deposition to overcome the above deficiencies. The temperature of the substrate during deposition has been maintained near 700 °C to reduce the loss of lithium from lithium niobate and to reduce the thermal stresses. Characterization by x-ray diffraction and Raman spectroscopy showed that the lithium niobate lattice is preserved without incorporation of carbon and the diamond layer is free from graphitic carbon. The integrated lithium niobate-diamond layered structure is shown to be suitable for surface acoustic wave devices.
Effects of annealing temperature on the characteristics of HfSixOy/HfO2 high-k gate oxides
Authors: Kim H. D. , Roh Y. , Lee Y. , Lee J. E. , Jung D. , Lee N.-E.
Published: July 2004

We have investigated the effects of annealing temperature on the physical and electrical properties of the HfSixOy/HfO2 thin film for high-k gate oxides in a metal-oxide-semiconductor device. The oxidation and subsequent postoxidation N2 annealing at 500 °C of Hf deposited directly on the Si substrate results in the HfSixOy/HfO2 stack layer with excellent electrical properties. For instance, we observe a negligible hysteresis window, an excellent equivalent oxide thickness (1.2 nm), and a low leakage current density (⩽4×10−5 A/cm2 at 2 V after compensating the flatband voltage shift). However, the formation of an interfacial SiOx layer enhances as annealing temperature increases. Based on current observation, we suggest that annealing temperature must be carefully controlled to obtain the excellent electrical properties of HfO2/HfSixOy high-k gate oxides.
Physical self-assembly and the nucleation of three-dimensional nanostructures by oblique angle deposition
Authors: Karabacak T. , Wang G.-C. , Lu T.-M.
Published: July 2004

Growth front morphology of a thin film formed by physical vapor deposition is controlled by many factors including surface diffusion and shadowing effects. Instabilities can occur if shadowing is more dominant compared to other surface effects and can lead to many diverse physically self-assembled three-dimensional nano-size structures. In this article, we explore the fundamental nucleation and growth mechanisms of the nanostructures during oblique angle deposition. Monte Carlo simulations were carried out to predict the island density, island size distribution, and island–island correlation during the initial stages of growth. The results were compared to that obtained by the oblique angle sputter deposited tungsten films imaged by atomic force microscopy and scanning electron microscopy. Isolated islands with quasiperiodic distribution were formed as a natural consequence of the shadowing effect. Isolated columnar structures are shown to grow on these islands and the width W of the columns is predicted to grow as a function of column length d in a power law form, W∼dp, where the exponent p is between 0.3 and 0.5. The predicted p is consistent with the experimentally determined exponent values for growth of column widths from a variety of materials such as W, Co, Cu, and Si. The exponent values calculated from a derived continuum equation were also consistent with the experimental results.
Pumping characteristics of metal films in a vacuum glass vessel: Experimental and theoretical issues
Authors: Bonucci Antonio , Giannantonio Roberto , Carretti Corrado , Longoni Giorgo , Caterino Anna Lisa , Urbano Marco
Published: July 2004

The evaluation of the pumping characteristics of metallic films deposited onto glass surfaces in a vacuum environment is a very important issue for several industrial and research applications. Many years ago, an optimized experimental setup and method were defined to measure the pumping characteristics of barium films inside cathode ray tubes (CRTs). [P. della Porta and F. Ricca, Advances in Vacuum Science and Technology (Pergamon, New York, 1960), Vol. II, p. 661 and P. della Porta and L. Michon, Vacuum 15, 536 (1965)]. However, some technological limitations, related both to the particular experimental configuration and to the method used, prevented the possibility of extending this approach to a more general case, including adsorbing materials different from barium, deposited onto surfaces having a geometry different from that of a CRT. The progress in vacuum technology makes it possible today to use a large variety of components to assemble an experimental vacuum apparatus. Moreover, the availability of powerful computational tools allows the design of the best experimental configuration for any specific purpose. In this work, an approach to the study of the pumping characteristics of an adsorbing film in a vacuum is discussed. An improved experimental configuration is described and a mathematical method, based on the angular coefficients approach, able to suitable calculate the gas distribution inside a vacuum vessel, is proposed. The agreement between the experimental data and the theoretical results obtained in the case of carbon monoxide sorption onto a barium getter surface deposited into spherical glass bulbs having different dimensions is discussed.
Ferroelectric properties of lanthanide-doped Pb(Zr0.6,Ti0.4)O3 thin films prepared by using a sol-gel method
Authors: Son Young-Hoon , Kim Kyoung-Tae , Kim Chang-Il
Published: July 2004

Ln (Er, Eu, Tb, Yb)-doped lead zirconate titanate [Pb1.1(Zr0.6Ti0.4)O3; PZT] thin films on Pt/Ti/SiO2/Si substrates prepared by a sol-gel method. Films have a Zr/Ti ratio of 60/40 and perovskite phase polycrystalline structure. The effect on the structural and electrical properties of films was measured according to additive compound. Dielectric and ferroelectric properties of PZT thin films were altered significantly by Ln-doping. A PZT thin film with higher dielectric constant and improved leakage current characteristic was obtained by adding 0.3 mol % of Ln. Ln-doped PZT thin films showed improved fatigue characteristics compared to the undoped PZT thin film.
Effect of plasma flux composition on the nitriding rate of stainless steel
Authors: Muratore C. , Walton S. G. , Leonhardt D. , Fernsler R. F. , Blackwell D. D. , Meger R. A.
Published: July 2004

The total ion flux and nitriding rate for stainless steel specimens exposed to a modulated electron beam generated argon-nitrogen plasma were measured as a function of distance from the electron beam axis. The total ion flux decreased linearly with distance, but the nitriding rate increased under certain conditions, contrary to other ion flux/nitriding rate comparisons published in the literature. Variation in ion flux composition with distance was explored with a mass spectrometer and energy analyzer as a possible explanation for the anomalous nitriding rate response to ion flux magnitude. A transition in ion flux composition from mostly N2+ to predominantly N+ ions with increasing distance was observed. Significant differences in molecular and atomic nitrogen ion energy distributions at a negatively biased electrode were also measured. An explanation for nitriding rate dependence based on flux composition and magnitude is proposed.
Iron-carbide cluster thermal dynamics for catalyzed carbon nanotube growth
Authors: Ding Feng , Bolton Kim , Rosén Arne
Published: July 2004

Molecular dynamics simulations have been used to study the thermal behavior of FeN−mCm clusters where N, the total number of atoms, extends up to 2400. Comparison of the computed results with experimental data shows that the simulations yield the correct trends for the liquid–solid region of the iron-carbide phase diagram as well as the correct dependence of cluster melting point as a function of cluster size. The calculation indicates that, when carbon nanotubes (CNTs) are grown on large (>3–4 nm) catalyst particles at low temperatures (<1200 K), the catalyst particles are not completely molten. It is argued that the mechanism of CNT growth under these conditions may be governed by the surface melting of the cluster.
Morphological evolution of III–V semiconductors and SiO2 during low energy electron enhanced dry etching
Authors: Lee S. H. , Ho R. M. , Goorsky M. S. , Gillis H. P. , Margolese D. I. , Demine M. A. , Anz S. J.
Published: July 2004

Evolution of surface morphologies of GaAs, GaP, InP, GaN, and SiO2 during dry etching is studied. Etching was carried out in Cl2/H2/Ar plasmas with electron enhancement. No structural damage was introduced during etching. Etched surface morphologies were observed with scanning electron microscopy and roughness values were obtained using atomic force microscope. Depending on binding energies, each material showed a different morphology evolution and final surface. Materials with low binding energies (GaAs, GaP, and InP) form pits or ridges early, and become rougher over time. Increasing electron flux to the surface overcomes the tendency to roughen and produces very smooth surfaces. Materials with high binding energies (GaN, SiO2) do not form pits or ridges early. They quickly form and maintain extremely smooth surfaces with little dependence on electron flux.
Spectroscopic characterization of high k dielectrics: Applications to interface electronic structure and stability against chemical phase separation
Authors: Krug C. , Lucovsky G.
Published: July 2004

Extensive spectroscopic characterization of high k materials under consideration for replacing Si oxide as the gate dielectric in Si-based microelectronic devices has been accomplished. Band offset energies of Zr silicates with respect to Si have been determined as a function of silicate alloy composition by combining near-edge x-ray absorption fine structure spectroscopy, vacuum-ultraviolet spectroscopic ellipsometry, x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and ab initio calculations on cluster models. These studies provide insight that applies to both transition metal- and rare earth-based dielectrics, including binary oxides and silicate and aluminate alloys. Results have been used to estimate the electronic conduction through Hf silicate films as a function of alloy composition. Thermally induced chemical phase separation in Zr silicate films has been characterized using XPS, Fourier transform infrared spectroscopy, x-ray diffraction, high-resolution transmission electron microscopy, and extended x-ray absorption fine structure spectroscopy. Our results indicate separation into a noncrystalline, Si-rich phase and either nano- or microcrystalline ZrO2, depending on the original film stoichiometry.
Deposition and field-emission characterization of electrically conductive nitrogen-doped diamond-like amorphous carbon films
Authors: Kinoshita Haruhisa , Ikuta Ryo , Murakami Satoshi
Published: July 2004

For the fabrication of high performance field emitters, diamond-like amorphous carbon films doped with nitrogen (DAC:N) were formed using an intermittent supermagnetron plasma chemical vapor deposition technique. DAC:N films were deposited using isobutane plasma to investigate the influence of discharge-off time and electrode spacing on the physical properties of the films at upper- and lower-electrode radio frequency (rf) powers (LORF) of 800 W/50–800 W. At LORF of 100 W, a discharge-on time of 1 min, and a discharge-off time (cooling time) of 30 s–10 min, resistivity was decreased with a decrease of the cooling time. By reducing the electrode spacing from 60 to 20 mm at a LORF of 50 and 800 W, the optical band gap of DAC:N film was decreased from 0.85 and 0.23 eV to 0.6 and 0 eV, respectively. A flat DAC:N film of 700 Å thickness was deposited on a n-Si wafer at rf powers of 800 W/800 W. Using this flat DAC:N film, a threshold electric field of 18 V/μm was observed and maximum field-emission current density of 2.2 mA/cm2 was observed at the electric field of 32 V/μm.
Large magnetic field effects in organic light emitting diodes based on tris(8-hydroxyquinoline aluminum) (Alq3)/N,N′-Di(naphthalen-1-yl)-N,N′diphenyl-benzidine (NPB) bilayers
Authors: Davis Albert H. , Bussmann Konrad
Published: July 2004

Magnetic field effects (MFEs) in the luminescence and photoconductivity of organic crystals such as anthracene have been known since the 1960s. While engaged in a project to use spin polarized current to manipulate electroluminescence (EL) in organic light emitting diodes based on a bilayer of tris(8-hydroxyquinoline) aluminum (Alq3) and N,N′-Di(naphthalen-1-yl)-N,N′diphenyl-benzidine (NPB), we observed MFE similar to those reported in anthracene. The MFE consist of an increase in EL with increasing magnetic field of a few percent for small magnetic fields, a decrease in EL of greater than 20% at high fields and an increase in conductivity, i.e., negative magnetoresistance (MR), for all magnetic fields. The high field effect (HFE) is enhanced at lower temperatures and higher current densities and is similar to that reported for delayed luminescence in anthracene single crystals suggesting that triplet–triplet annihilation (TTA) influences light emission in Alq3. Transient EL studies were performed in an attempt to identify a delayed component for the MFE with a time scale appropriate for triplets in Alq3, but the MFE develops at least ten times faster than that expected using a recently published triplet lifetime for Alq3. However, the temperature and drive dependence of the HFE suggests that TTA involving triplet entities with shorter lifetimes might be responsible for the HFE. In contrast, the low field effect (LFE) is insensitive to temperature and drive conditions and exists even when the HFE does not, indicating that the LFE is caused by a separate mechanism.
Metallic tin reactive sputtering in a mixture Ar–O2: Comparison between an amplified and a classical magnetron discharge
Authors: Snyders R. , Gouttebaron R. , Dauchot J. P. , Hecq M.
Published: July 2004

In this work, we have studied the tin reactive sputtering in a pure magnetron and an amplified (rf coil located between the target and the substrate) magnetron discharge. The rf coil allows us to increase the plasma reactivity (plasma amplification) and consequently to favor the substrate oxidation process. It is known that the thin film synthesis occurs by sputtered material condensation on the substrate followed by the condensed material oxidation by the reactive species present in the discharge, especially the atomic oxygen. In this study, we show by deposition rate and discharge voltage measurements that the transition between the metallic and the poisoned mode of the target is not influenced by the plasma amplification (40% O2 in our experimental conditions). Nevertheless, we have observed that the discharge composition (mass spectrometry) and the films stoichiometry (x-ray photoelectron spectroscopy) depend on the amplification. We observe clearly an increase of the oxidation process on the substrate when the plasma is amplified (magnetron+coil). Consequently, it is concluded that it is possible to prepare fully oxidized tin film while the target is still in the metallic mode. For example, for a gas mixture of 10% in O2, we get in a pure magnetron discharge a film stoichiometry corresponding to SnO1.0, while in an amplified discharge with 200 W rf power applied to the coil, we obtain a more oxidized film with the SnO1.8 stoichiometry.
Highly transparent and conductive ZnO:Al thin films prepared by vacuum arc plasma evaporation
Authors: Miyata Toshihiro , Minamino Youhei , Ida Satoshi , Minami Tadatsugu
Published: July 2004

A vacuum arc plasma evaporation (VAPE) method using both oxide fragments and gas sources as the source materials is demonstrated to be very effective for the preparation of multicomponent oxide thin films. Highly transparent and conductive Al-doped ZnO (AZO) thin films were prepared by the VAPE method using a ZnO fragment target and a gas source Al dopant, aluminum acethylacetonate (Al(C5H7O2)3) contained in a stainless steel vessel. The Al content in the AZO films was altered by controlling the partial pressure (or flow rate) of the Al dopant gas. High deposition rates as well as uniform distributions of resistivity and thickness on the substrate surface were obtained on large area glass substrates. A low resistivity on the order of 10−4 Ω cm and an average transmittance above 80% in the visible range were obtained in AZO thin films deposited on glass substrates.
Characteristics of Pt/Bi3.25La0.75Ti3O12/ZrO2/Si structures using ZrO2 as buffer layers for ferroelectric-gate field-effect transistors
Authors: Lee Jung-Mi , Kim Kyoung-Tae , Kim Chang-Il
Published: July 2004

We investigated the structural and electrical properties of Bi3.25La0.75Ti3O12 (BLT) films grown on Si covered with ZrO2 buffer layer. The BLT thin film and ZrO2 buffer layer were fabricated using a metalorganic decomposition method. The electrical properties of the metal–ferroelectric–insulator–semiconductor (MFIS) structure were investigated by varying thicknesses of the ZrO2 layer. The width of the memory window in the capacitance–voltage curves for the MFIS structure decreased with increasing thickness of the ZrO2 layer. It is considered that the memory window width of MFIS is not affected by remanent polarization. Leakage current density decreased by about 4 orders of magnitude after using ZrO2 buffer layer. Transmission electron microscopy shows no interdiffusion and reaction that was suppressed using the ZrO2 film as a buffer layer.
Exploration of the chemical bonding forms of alkoxy-type organic monolayers directly attached to silicon
Authors: Saito Nagahiro , Lee Sun-Hyung , Maeda Noriya , Ohta Riichiro , Sugimura Hiroyuki , Takai Osamu
Published: July 2004

Alkoxy-type organic monolayers on hydrogen-terminated silicon were prepared from 1-undecanol (UN), 1-nonanol (NO), 1-heptanol (HP), and 4-phenylphenenol (PP). These monolayers were characterized based on x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). XPS spectra showed that the lowest amount of SiOx oxide on the sample of the UN monolayer. On the other hand, a SiOx peak was clearly observed for the HP, NO, and PP monolayers. The generation of SiOx in the PP monolayer may have been due to steric hindrance of the aromatic rings. The–CH2–region in the FT-IR spectra showed that shorter alkyl chains promoted the formation of gauche conformers in the monolayer. This increase of gauche conformers was determined to have caused the generation of SiOx in the alkyl monolayers.
Characteristics of high-k gate dielectric formed by the oxidation of sputtered Hf/Zr/Hf thin films on the Si substrate
Authors: Kim H. D. , Roh Y. , Lee J. E. , Kang H.-B. , Yang C.-W. , Lee N.-E.
Published: July 2004

We have investigated the effects of high temperature annealing on the physical and electrical properties of multilayered high-k gate oxide [HfSixOy/HfO2/intermixed-layer(IL)/ZrO2/intermixed-layer(IL)/HfO2] in metal-oxide-semiconductor device. The multilayered high-k films were formed after oxidizing the Hf/Zr/Hf films deposited directly on the Si substrate. The subsequent N2 annealing at high temperature (⩾ 700 °C) not only results in the polycrystallization of the multilayered high-k films, but also causes the diffusion of Zr. The latter transforms the HfSixOy/HfO2/IL/ZrO2/IL/HfO2 film into the Zr-doped HfO2 film, and improves electrical properties in general. However, the thin SiOx interfacial layer starts to form if annealing temperature increases over 700 °C, deteriorating the equivalent oxide thickness.
Experiments and theoretical explanation of droplet elimination phenomenon in pulsed-bias arc deposition
Authors: Lin Guoqiang , Zhao Yanhui , Guo Huimei , Wang Dezhen , Dong Chuang , Huang Rongfang , Wen Lishi
Published: July 2004

TiN films on stainless steel have been synthesized by arc deposition with dc and pulsed biases. We show that at the same bias (−300 V), coarse particles on the film surface are significantly decreased both in size and in amount if the bias is pulsed. In order to clarify the related process, we have analyzed, using orthogonal design, the influences from different working parameters. We show that the parameters related to the pulsed bias such as magnitude and duty cycle have important effects on the size distribution of the particles. According to our theoretical calculations based on plasma sheath and dust plasma theories, the origin of the droplet elimination lies in enhanced repulsion of the negatively charged droplets in pulsed plasma.
Spectroscopic-ellipsometry characterization of the interface layer of PbZr0.40Ti0.60O3/LaNiO3/Pt multilayer thin films
Authors: Hu Z. G. , Huang Z. M. , Wu Y. N. , Wang G. S. , Meng X. J. , Shi F. W. , Chu J. H.
Published: July 2004

The PbZr0.40Ti0.60O3/LaNiO3 multilayer thin films with different LaNiO3 film thickness were deposited on Pt/Ti/SiO2/Si substrates by a modified sol-gel technique. The optical properties of the PbZr0.40Ti0.60O3 thin films, LaNiO3 thin films, and the interface layers between them have been investigated using spectroscopic ellipsometry in the wavelength region of 400–1700 nm. For fitting the ellipsometric data to interpret the optical constants of the multilayer films, the unknown dielectric function of the PbZr0.40Ti0.60O3 films, LaNiO3 films, and the interface layers were constructed using a single-Lorentz oscillator. It is noted that the shapes of the optical constants are different for the three different layers because the fitted values of the model parameters are markedly different. It is found that the PbZr0.40Ti0.60O3 films are entirely transparent (namely the extinction coefficient κ=0) in the 400–1700 nm wavelength region. Moreover, the optical constants of the interface layer and the LaNiO3 films are focused on and discussed.
Microelectromechanical system device for calibration of atomic force microscope cantilever spring constants between 0.01 and 4 N/m
Authors: Cumpson Peter J. , Hedley John , Clifford Charles A. , Chen Xinyong , Allen Stephanie
Published: July 2004

Calibration of atomic force microscope (AFM) cantilevers is necessary for the measurement of nano-newton and pico-newton forces, which are critical to analytical application of AFM in the analysis of polymer surfaces, biological structures and organic molecules. Previously we have described microfabricated array of reference spring (MARS) devices for AFM cantilever spring-constant calibration. Hitherto, these have been limited to the calibration of AFM cantilevers above 0.03 N/m, although they can be used to calibrate cantilevers of lower stiffness with reduced accuracy. Below this limit MARS devices similar to the designs hitherto described would be fragile and difficult to manufacture with reasonable yield. In this work we describe a device we call torsional MARS. This is a large-area torsional mechanical resonator, manufactured by bulk micromachining of a “silicon-on-insulator” wafer. By measuring its torsional oscillation accurately in vacuum we can deduce its torsional spring constant. The torsional reference spring spans the range of spring constant (from 4 down to 0.01 N/m) that is important in biological AFM, allowing even the most compliant AFM cantilever to be calibrated easily and rapidly.
Studies of the electronic structure at the Fe3O4–NiO interface
Authors: Wang Hui-Qiong , Gao Weiwei , Altman Eric I. , Henrich Victor E.
Published: July 2004

The interfacial electronic structure between the metallic ferrimagnet Fe3O4 and the insulating antiferromagnet NiO is investigated in the lattice matched heteroepitaxial system Fe3O4 (100)–NiO (100) by growing ultrathin NiO films on single-crystal Fe3O4 (100) substrates. The Fe3O4 (√2×√2)R45° surface is characterized prior to growth by low-energy electron diffraction, reflection high-energy diffraction, scanning tunneling microscopy, ultraviolet photoelectron spectroscopy (UPS), x-ray photoemission spectroscopy (XPS) and Auger electron spectroscopy. UPS and XPS, which sample several monolayers in the substrate–overlayer structure, are used to monitor near-surface electronic properties versus NiO overlayer thickness. Comparison of experimental He II UPS spectra of the valence band electronic structure with a simple model of substrate–overlayer emission indicates that the electronic transition from Fe3O4 to NiO is nearly atomically sharp.
Correlation between volume fraction of clusters incorporated into a-Si:H films and hydrogen content associated with Si–H2 bonds in the films
Authors: Koga Kazunori , Kaguchi Naoto , Shiratani Masaharu , Watanabe Yukio
Published: July 2004

A downstream-cluster-collection method of high sensitivity has been developed to obtain information on size distribution, density, shape, and structure of clusters formed in reactive plasmas. The method have been applied together with a cluster-suppressed plasma chemical vapor deposition method in order to study a correlation between a volume fraction Vf of clusters incorporated into a-Si:H films and a hydrogen content CH(SiH2) associated with Si–H2 bonds in the films. The CH(SiH2) value decreases almost linearly from 0.6 at. % to 0.05 at. % with decreasing Vf by about one order of magnitude. The result indicates that the incorporation of clusters, above about 1 nm in size, of amorphous structure into a-Si:H films is an important origin of Si–H2 bonds in the films.
Stoichiometry dependence of hardness, elastic properties, and oxidation resistance in TiN/SiNx nanocomposites deposited by a hybrid process
Authors: Haug F.-J. , Schwaller P. , Wloka J. , Patscheider J. , Karimi A. , Tobler M.
Published: July 2004

TiN/SiN x nanocomposite layers with Si contents between 0 and 25 at. % were deposited by a reactive arc-magnetron sputtering hybrid process. The stoichiometry of the SiNx phase was found to be related to the silicon sputter target state, i.e., elemental or nitrided. TiN/SiNx layers with a Si:N ratio close to 0.75 (silicon nitride) show a hardness maximum at overall Si contents between 5 and 7 at. %. The hardness maximum is absent for nitrogen deficient stoichiometries of SiNx. The oxidation resistance of the composite layers is three to five times better than that of pure TiN. In contrast to the effect of the stoichiometry on hardness, the oxidation resistance depends on the overall silicon content only, regardless of stoichiometry.
Effects of oxygen contents on the electrical and optical properties of indium molybdenum oxide films fabricated by high density plasma evaporation
Authors: Sun Shi-Yao , Huang Jow-Lay , Lii Ding-Fwu
Published: July 2004

Indium molybdenum oxide (IMO) films were made from an oxidized target with In2O3 and MoO3 in a weight proportion of 99:1 by using a high density plasma evaporation with the substrate maintained at room temperature. Effects of the oxygen contents of 1%–28.6% on the structural and optoelectronic properties of the IMO films have been investigated. Results revealed that the addition of oxygen showed an increase in the mobility of the IMO films. Optimized oxygen vacancies and high mobility could dominant the conducting mechanism. X-ray photoelectron spectroscopy and x-ray diffraction analyses indicated that enhanced crystalline structure improved the mobility and transmittance of the film. Uniform IMO films with resistivity of 3.56×10−4 Ω cm and average transmittance of 85.06% over the wavelength of 450–800 nm were obtained.
Internal structure of TiAlN/VN coating deposited on sharp edges by ion-assisted physical vapor deposition
Authors: Macak E. B. , Rodenburg J. M.
Published: July 2004

We examine the detailed structure of ion-assisted physical vapor deposited coatings applied to sharp edges, with particular emphasis on the region at the tip of the edge. The problem is studied on the example of a 30° wedge coated with TiAlN/VN deposited by unbalanced magnetron sputtering at a substrate bias −75 V. Cross-sectional TEM analysis shows that the grain structure of the coating on top of the wedge is different than in the case of a flat surface. Simulations of the ion transport across the plasma sheath and of the ion impact at the surface describe the characteristics of the ion bombardment at the edge. In the vicinity of the edge, the ions enter at very steep angles of incidence, which increases the energy deposited into the growing layer and thus promotes the growth of larger crystallites. An exception is the region right at the very tip of the edge where, due to the nonzero radius of curvature, the incidence of the ions at the growth surface is perpendicular—this region is shown to have a different microstructure. Additional changes in the internal structure are due to the curvature of the coating at the tip of the edge.
Microstructure and mechanical properties of Ir–Ta coatings on nickel-base single-crystal superalloy TMS-75
Authors: Kuppusami P. , Murakami H. , Ohmura T.
Published: July 2004

In the present study, a methodology for the controlled addition of tantalum in iridium—alloy coatings prepared by dc magnetron sputtering from a composite target has been proposed. Ir–Ta coatings with 16.2, 23.9, 40.7, and 65.1 at. % Ta were deposited at 573 K on the 〈100〉 oriented nickel-base single-crystal superalloy, TMS-75, by suitably selecting the ratio of the surface area of the iridium target to the surface area of the tantalum target on the basis of reported values of the sputtering yield of the respective elements. The microstructural analysis indicates that pure coatings of iridium and tantalum form polycrystalline films with rms roughness of ∼5 nm, while the Ir–Ta coatings form a nanocrystalline structure whose crystallite size and rms roughness decrease with the increase in tantalum content. Measurement of mechanical properties using the nanoindentation technique shows that the Young’s modulus and hardness of the coatings generally decrease with the increase in the tantalum content. However, there is a peaking of hardness in the composition range 16.2–23.9 at. % tantalum. This could be due to the formation of the nanocrystalline Ir3Ta phase. The data on the mechanical properties are presented to explore the possibility of using Ir–Ta as an oxidation-resistant material on nickel-base single-crystal superalloy.
Analysis and modeling of low pressure chemical vapor deposition of phosphorus-doped polysilicon in commercial scale reactor
Authors: Shimizu Ryosuke , Ogino Masaaki , Sugiyama Masakazu , Shimogaki Yukihiro
Published: July 2004

In a commercial scale low pressure chemical vapor deposition (CVD) reactor, we analyzed the elementary reaction of silane based CVD with the doping gas of phosphine. The variation of conductivity in the radial direction over a monitor wafer became significant as the phosphine gas partial pressure decreased, and it reached up to about 30% at 6.5×10−4 Pa. The radial distribution of phosphorus fraction in a film, however, was smaller than 7%. On the basis of the diffusion model of chemical species into the wafer gaps, we found that the sticking probability of phosphine is 2–5×10−5, which is 1 order of magnitude larger than the one of silane. The reaction kinetics of both silane and phosphine seems almost linear, but slight nonlinearity at high phosphine concentration range was also indicated.
Luminescence behavior of Li-doped Gd2O3:Eu3+ thin film phosphors grown by pulsed laser ablation
Authors: Yi S. S. , Bae J. S. , Seo H. J. , Jeong J. H. , Holloway P. H.
Published: July 2004

Gd 2 O 3 : Eu 3+ and Li-doped Gd2O3:Eu3+ luminescent thin films have been grown on Al2O3(0001) substrates at substrate temperatures in the range of 500–700 °C and oxygen pressure in the range of 100–300 mTorr using a pulsed laser deposition technique. The films grown under different deposition conditions have been characterized using microstructural and luminescent measurements. The photoluminescence brightness data obtained from Li-doped Gd2O3:Eu3+ films grown under optimized conditions have indicated that sapphire is a good substrate for the growth of high quality Li-doped Gd2O3:Eu3+ thin film red phosphor. The luminescence of the Gd2O3:Eu3+ films is highly dependent on the crystallinity and surface roughness of the films. In particular, incorporation of Li+ ions into the Gd2O3 lattice induces a remarkablly enhanced crystallinity and photoluminescence. The full width at half maximum of the diffraction peaks is narrower (∼20%) for films grown with versus films grown without Li doping. The root mean square roughness of these films was found to vary from 7.5 to 16.1 nm depending upon the Li doping. The highest emission intensity of Li-doped Gd2O3:Eu3+ films was increased by a factor of 2.3 in comparison with that of Gd2O3:Eu3+ films. This phosphor is promising for the flat panel displays.
Electronic and optical properties of GaAsN/GaAs quantum wells: A tight-binding study
Authors: Shtinkov N. , Turcotte S. , Beaudry J.-N. , Desjardins P. , Masut R. A.
Published: July 2004

We present empirical tight-binding (TB) calculations of the electronic structure of GaAs1−xNx/GaAs (001) quantum wells (QWs) with small N concentrations (0<x<0.045). We use a recently developed TB model for the electronic structure of dilute GaAs1−xNx [Shtinkov et al., Phys. Rev. B 67, 081202R (2003)] without introducing any additional parameters apart from the valence band offset (VBO) between GaAs and GaAs1−xNx. The dependences of the bound states energies on the QW width and on the N concentration x are investigated and the nature of the lowest-energy optical transitions is analyzed, showing that the knowledge of the first two optical transitions is sufficient to determine the value of the VBO. Our results are compared with experimental data from the literature, revealing good agreement for x⩽0.02. For larger concentrations, we find that the agreement is greatly improved if the concentrations determined from x-ray diffraction data are corrected for deviations from Vegard’s rule. The comparison with experimental results suggests that the unstrained GaAs/GaAs1−xNx VBO is close to zero, in agreement with other studies.
Selective plasma-induced deposition of fluorocarbon films on metal surfaces for actuation in microfluidics
Authors: Bayiati P. , Tserepi A. , Gogolides E. , Misiakos K.
Published: July 2004

The present work focuses on the selective deposition of fluorocarbon (FC) films on metal surfaces, aluminum in specific, over SiO2 surfaces, in order to obtain surfaces of distinct wettability. If this is achieved, hydrophobic/hydrophilic patterning of substrates would be feasible by means of a self-aligned and relatively simple method. For the selection of conditions appropriate for selective deposition of FC films on Al over SiO2, plasma parameters such as plasma power, bias voltage, electrode temperature, and gas composition were varied. The selectivity of the deposition is optimized through proper selection of the deposition conditions, mainly gas mixture composition and deposition time, and is demonstrated by means of contact angle measurements on Al and SiO2 surfaces. Contact angles are measured without and with voltage application between the droplet and the surface to induce electrowetting. Contact angles vary as a function of the applied voltage and in combination with measured contact angle hysteresis dictate the voltage range necessary for droplet actuation. The results demonstrate that optimization of the electrowetting properties of such plasma-deposited films is necessary for rendering feasible the use of such films in electrowetting-based actuation of microfluidic devices with application of relatively small voltages.
Growth condition dependence of structure and surface morphology of GaN films on (111)GaAs substrates prepared by reactive sputtering
Authors: Guo Q. X. , Lu W. J. , Zhang D. , Tanaka T. , Nishio M. , Ogawa H.
Published: July 2004

GaN films were grown on (111)GaAs substrates by radio frequency magnetron sputtering in an ambient of nitrogen using a pure gallium target. The effect of the growth condition including the substrate temperature and the sputtering pressure on the structural properties of GaN films was investigated in relation to the surface morphology. It was found that both the substrate temperature and the sputtering pressure strongly affect the surface morphology and crystalline quality. High-quality crystalline GaN film with smooth surface could be obtained at a substrate temperature of 700 °C with a sputtering pressure of 45 mTorr. Based on the experimental results, the growth mechanism for reactive sputtered GaN films was discussed.
Multivariate statistical analysis for x-ray photoelectron spectroscopy spectral imaging: Effect of image acquisition time
Authors: Peebles D. E. , Ohlhausen J. A. , Kotula P. G. , Hutton S. , Blomfield C.
Published: July 2004

The acquisition of spectral images for x-ray photoelectron spectroscopy (XPS) is a relatively new approach, although it has been used with other analytical spectroscopy tools for some time. This technique provides full spectral information at every pixel of an image, in order to provide a complete chemical mapping of the imaged surface area. Multivariate statistical analysis techniques applied to the spectral image data allow the determination of chemical component species, and their distribution and concentrations, with minimal data acquisition and processing times. Some of these statistical techniques have proven to be very robust and efficient methods for deriving physically realistic chemical components without input by the user other than the spectral matrix itself. The benefits of multivariate analysis of the spectral image data include significantly improved signal to noise, improved image contrast and intensity uniformity, and improved spatial resolution—which are achieved due to the effective statistical aggregation of the large number of often noisy data points in the image. This work demonstrates the improvements in chemical component determination and contrast, signal-to-noise level, and spatial resolution that can be obtained by the application of multivariate statistical analysis to XPS spectral images.