bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of thermal annealing in the properties of PECVD a-SiC layers
Authors: Marsal L.F. , Pallares J. , Orpella A. , Bardés D. , Puigdollers J. , Alcubilla R. 
Published: April 2011

ABSTRACTEffects of thermal annealing in the properties of PECVD amorphous-Si0.8C0.2:H layers were studied. In order to reduce the density defects and increase the electrical conductivity, some samples were annealed: at 500 °C during 1 hour followed by 15 minutes at 800 °C. The results show that in the course of the thermal process, the hydrogen diffuse outside the film and the annealed Si0.8C0.2:H films tend to segregate in silicon clusters and, as a result, partially crystallize. Electrical dark conductivity shows an increase in more than six orders of magnitude, while the optical bandgap decreases from 1.9 eV to 1.4 eV. Annealed- Si0.8C0.2 films have been used as emitter in silicon bipolar transistors. Results indicate promising features such as low base currents and good emitter Gummel numbers.
Thermal Stabilization and Crystallization of Nanometric Particles of Si-C-N Produced by RF-Plasma Enhanced Chemical-Vapor-Deposition
Authors: Viera Gregorio , Bertran Enric , Polo Mari C. , Garcia-Caurel Enric , Farjas Jordi , Roura Pere 
Published: April 2011

ABSTRACTNanoparticles of Si-alloys were grown at room temperature in a RF-PECVD process from mixtures of SiH4, CH4 and NH3. Quasi-monodisperse nanoparticles were produced in conditions of fast particle development. Among the different conditions for particle formation, we chose moderate low pressure (below 100Pa) and RF-power lower than 200W in all cases. The particle size was controlled through the modulation of the RF power supplied to the discharge. A post-thermal treatment at 800-900°C was used to eliminate the hydrogen of the particles and to stabilize them against environmental oxidation. To study the thermal crystallization of the particles, various thermal-treatments were used. The annealing of these particles at 1400°C for one hour under Ar or N2 led to different results depending on the composition of the samples as revealed by HRTEM and electron-diffraction analysis: SiC particles showed a marked internal crystallization; SiCN particles developed nanocrystals embedded in their amorphous matrix; Si particles crystallized in diamond-like silicon when annealed in Ar, whereas long whiskers of the α-Si3N4 phase, 50-200nm wide, grew from the particles in N2.
AFM and HREM Observation of the Pulse Laser Interference Crystallized a--Si:H/a-SiNx:H Multilayers
Authors: Wang Li , Huang Xinfan , Li Jian , Xu Jun , Yin Xiaobo , Li Qiliang , Li Wei , Zhu Jianming , Wang Mu , Liu Zhiguo , Chen Kunji , Fung Y. M. , Xu J. B. 
Published: April 2011

ABSTRACTThe patterned nc-Si/a-SiNx:H superlattices were fabricated by using laser interference crystallization method and investigated with atomic force microscope (AFM), micro-Raman spectroscope, cross-section transmission electron microscope (TEM) and high resolution electron microscope (HREM). We found that after laser irradiation, self-assembled Si nanocrystallites (nc-Si) are formed within the initial a-Si:H sublayers, moreover, in the plane parallel to the surface of the films, these nc-Si orderly distribute in the certain regions with the same periodicity of 2.0 µm as phase shifting mask grating. Based on the structural analyses, the crystallization mechanism and the origin of the self-assembled phenomena are briefly discussed.
Excimer Laser Recrystallization of a-Si Employing Aluminum Masking Window
Authors: Jeon Jae-Hong , Lee Min-Cheol , Jung Sang-Hoon , Han Min-Koo 
Published: April 2011

ABSTRACTA new excimer laser recrystallization method of amorphous silicon is proposed to increase the grain size and control the grain boundary locations in polycrystalline silicon films. The proposed method is based on the lateral grain growth which occurs at the interface between molten and unmolten regions. To obtain selectively molten regions, the proposed method employs aluminum patterns on amorphous silicon. The aluminum patterns act as the beam shield during the laser irradiation as well as the lateral heat sink during the solidification period. The high reflectance of aluminum at the wavelength of XeCl excimer laser offers stable beam shielding property, and the high thermal conductivity enhances the lateral heat flow by the quick draining of laterally propagated heat. TEM observation has revealed that the well arranged large grains were successfully obtained.
Memory effects in MOS capacitors with silicon rich oxide insulators
Authors: Lombardo S. , Crupi I. , Spinella C. , Bongiorno C. , Liao Y. , Gerardi C. , Vulpio M. , Fazio B. , Privitera S. 
Published: April 2011

ABSTRACTTo form crystalline Si dots embedded in SiO2, we have deposited thin films of silicon rich oxide (SRO) by plasma-enhanced chemical vapor deposition of SiH4 and O2. Then the materials wereannealed in N2 ambient at temperatures between 950 and 1100 °C. Under such processing, the supersaturation of Si in the amorphous SRO film produces the formation of crystalline Si dots embedded in SiO2. The narrow dot size distributions, analyzed by transmission electron microscopy, are characterized by average grain radii and standard deviations down to about 1 nm. The memory function of such structures has been investigated in metal-oxidesemiconductor (MOS) capacitors with a SRO film sandwiched between two thin SiO2 layers as insulator and with an n+ polycrystalline silicon gate. The operations of write and storage are clearly detected by measurements of hysteresis in capacitance-voltage characteristics and they have been studied as a function of bias.
Recombination in Tritiated Amorphous Silicon
Authors: Kosteski Tome , Gaspari Franco , Hum David , Costea Stefan , Zukotynski Stefan , Kherani Nazir P. , Shmayda Walter T. 
Published: April 2011

ABSTRACTTritiated amorphous silicon was used for the intrinsic layer of a p-i-n hydrogenated amorphous silicon diode. Current versus voltage measurements were carried out on the diode over time under dark and illuminated conditions. There was a decrease in the forward characteristic of the diode when measured under dark conditions and there was a decrease in photovoltaic power. These changes can be explained by the creation of dangling bonds when bonded tritium atoms decay. By annealing the diode at 125 °C, most of its photovoltaic properties could be recovered. It was also found that luminescence could be recovered in tritiated amorphous silicon by thermal annealing.
Fast Deposition of Microcrystalline Silicon Films Using The High-Density Microwave Plasma Utilizing a Spokewise Antenna
Authors: Shirai H. , Sakuma Y. , Yoshino K. , Ueyama H. 
Published: April 2011

ABSTRACTThe high-density and low temperature microwave plasma utilizing a spokewise antenna was successfully applied to fast deposition of highly crystallized and photconductive microcrystalline silicon (μ-Si:H) films at low temperatures. The deposition rate and film crytstallinity significantly depend on the axial distribution of the plasma parameters. Best crystallinity was obtained at the axial distance Z from the quartz glass plate, where the spread of the ion beam energy impinging to the growing surface was minimum. By optimizing the axial distance Z and total pressure, highly crystallized μ-Si:H films could be fabricated with a high deposition rate of ∼47Å/s in the SiH4 and Ar mixture plasma with no use of the H2 dilution. An intentional control of the ion beam energy is also attempted using a mesh grid electrode to suppress the ion bombardment to the growing surface.
Molecular Beam Epitaxially Deposited Amorphous Silicon
Authors: Lockwood D. J. , Baribeau J.-M. , Noël M. , Zwinkels J. C. , Fogal B. J. , O'Leary S. K. 
Published: April 2011

ABSTRACTWe have deposited a novel form of amorphous silicon through molecular beam epitaxy in an ultra-high vacuum. In particular, by depositing silicon atoms onto an optical quality fused quartz substrate at room temperature we have obtained a silicon-based material that lacks the periodicity that characterizes crystalline silicon but nevertheless has 98% of the density. Spectroscopic studies reveal that there are only trace amounts of hydrogen and other impurity atoms in this novel form of amorphous silicon, this contrasting dramatically with the case of conventional amorphous silicon. The Raman and optical spectroscopic properties of this form of amorphous silicon are contrasted with those of conventional amorphous silicon and sputtered amorphous silicon, and conclusions, regarding the amount of disorder, are drawn. Finally, the device implications of this novel form of amorphous silicon are discussed.
Structure of Si:H Films Fabricated by Plasma-Enhanced Cvd using Hydrogen Diluted Plasma
Authors: Edelman F. , Chack A. , Weil R. , Beserman R. , Werner P. , Rech B. , Roschek T. , Beyer W. 
Published: April 2011

ABSTRACTThe structure of undoped Si:H films deposited at a high rate of 6-9 Å/s in an RF (13.56 MHz) plasma from hydrogen-silane gas mixtures at various substrate temperatures was studied using TEM (with in-situ annealing), XRD, Raman spectroscopy, optical absorption and hydrogen effusion. It is found that under our conditions the amorphous to crystalline transition occurs in a relatively narrow range of parameters, influenced mainly by hydrogen dilution and to a lesser degree by the substrate temperature. In the crystalline range the material is found to be nanocrystalline (average grain size 20 nm) and the crystals are essentially stable up to 800°C annealing. The crystal structure of a mixed amorphousnanocrystalline phase of samples deposited near the edge of crystallinity is also found to be rather stable. Nanocrystalline Si films deposited under these latter deposition conditions reveal in hydrogen effusion a relatively compact material and show high solar cell efficiencies (6-8%) when incorporated as i-layers in pin solar cells.
High Resolution Electron Microscopy (HREM) Study of Chemically Vapor Deposited Polycrystalline Si1-xGex Thin Films
Authors: Qin W. , Ast D. G. , Kamins T. I. 
Published: April 2011

ABSTRACTThe microstructure of polysilicon and Si0.69Ge0.31 thin films, grown by chemical-vapordeposition (CVD) on oxidized silicon wafers covered with a very thin polysilicon seed layer, was investigated using high-resolution electron microscopy (HREM). The plan-view HREM images showed that polysilicon films contained less substructure inside grains and had fewer multiple twins and more extended twin bands than Si0.69Ge0.31. On the other hand, only SiGe contained multiple twins with five-fold symmetry. The atomic model of the second-order symmetric twin boundary proposed for Si and based on the insertion of five-member and seven-membered rings was found to describe the atomic structures of second-order symmetric twin boundaries in Si0.69Ge0.31 as well. Within the accuracy of HREM, the repeat unit of the boundary was the same in Si0.69Ge0.31 and Si.
Localized Measurement of Strains in Damascene Copper Interconnects by Convergent-Beam Electron Diffraction
Authors: Nucci Julie A. , Keller Robert R. , Krämer Stephan , Volkert Cynthia A. , Gross Mihal E. 
Published: April 2011

AbstractConvergent beam electron diffraction (CBED) was used to measure localized lattice strains in damascene copper interconnects. This method provides data from areas of approximate diameter 20 nm, enabling evaluation of strain states within individual grains. Lattice parameters were determined by measuring the deficient higher order Laue zone (HOLZ) line positions in experimental zone axis patterns and subsequently comparing them to kinematical and dynamical simulations. Quantitative comparison was accomplished using a least squares analysis of distances between line intersections. Deposition-induced strains between 0.06% and 0.14% were measured in 2.0 µm wide lines. The uncertainty in strain determination was approximately 0.02%, as limited by the precision in HOLZ line detection. In addition to enabling localized analysis of strain states, another advantage of using CBED is that the microstructure can be fully evaluated. Used in conjunction with global methods such as X-ray diffraction, CBED may provide unique insight into localized failure phenomena such as electromigration void formation in damascene copper.
Studies of Copper Surfaces modified by Thermal and Plasma Treatments
Authors: Beyer G.P. , Baklanov M. , Conard T. , Maex K. 
Published: April 2011

AbstractIt was found that copper surfaces, which had been exposed to a clean room atmosphere, were covered by a layer, whose chemical composition can be described by Cu(OH)2·CuCO3. This layer can effectively be removed by either a short thermal treatment in vacuum at 350°C, a hydrogen plasma treatment, or a combination of both. Ex-situ photoelectron spectroscopy measurements show little difference of the chemical composition of the surface after the respective treatments. The thermal treatment, however, gives rise to re-crystallisation of the copper film due to the difference in temperature of deposition and the anneal. Ex-situ ellipsometry measurements indicate that the hydrogen plasma not only removes Cu(OH)2·CuCO3 but also passivates the copper surface.
Formation of AlxOyNz Barriers for Advanced Silver Metallization
Authors: Wang Y. , Alford T.L. 
Published: April 2011

AbstractSilver has been explored as a potential candidate for future advanced interconnects due to its lowest electrical resistivity, when compared with Al and Cu. As in the case of Cu metallization, an additional layer between the Ag film and underneath dielectric is necessary in order to improve adhesion and to block the diffusion of Ag atoms. In this study, thin aluminum oxynitride (AlxOyNz) diffusion barriers have been formed in the temperature range of 400-725 °C by annealing Ag/Al bilayers on oxidized Si substrates in ammonia ambient. Rutherford backscattering spectrometry showed that the out-diffused Al reacted with both the ammonia and oxygen in the ambient and encapsulated the Ag films. Higher process temperatures and thinner original Al layers showed to improve the resistivity of the encapsulated Ag layers. The resulting Ag resistivity values are ∼1.75 ± 0.35 µΩ-cm. The thermal stability test of these diffusion barriers showed that these barriers sustained the interdiffusion between Cu and Ag up to 620 °C at least for 30 min in either vacuum or flowing He-0.5% H2. This temperature is a 200°C improvement over previously reported values for the self-encapsulated Cu and Ag films. X-ray diffraction spectra showed no formation of any high resistive intermetallic compounds, i.e., Ag3Al, Ag2Al, and AlAg3.
Morphological, Chemical and Structural Study of Sputtered Al/Al2O3 Multilayers
Authors: Paven-Thivet C. Le , Aubert P. , Fusil S. , Zozime A. , Malibert C. , Houdy Ph. 
Published: April 2011

AbstractFor purpose of enhancement of mechanical properties, Al/Al2O3 films, with thickness A in the nanometric scale, were deposited on silicon substrate by reactive rf sputtering, at substrate temperatures Ts ranging from −90°C to 600°C. The characterisation (FEG-SEM, AFM, SIMS, XRR) has shown that Al/Al2O3 films are granular and rough, in correlation with the behavior of single alumnium films. The minimal roughness values are obtained at low Ts (−90°C and 25°C). The Λ = 20 rim-films are real multilayers, as confirmed by SIMS and XRR. Nevertheless, the multilayering character, i.e. the existence of multilayers, decreases when Ts increases. At low Ts, the relevant parameter to explain the weakness of stratification of Al/Al2O3 films is the roughness of layers, while at high Ts, the chemical interdiffusion clearly dominates, resulting in a no periodic structure at Ts = 600°C.
Deposition Of Nanotubes and Nanotube Composites Using Matrix-Assisted Pulsed Laser Evaporation
Authors: Wu P. K. , Fitz-Gerald J. , Pique A. , Chrisey D.B. , McGill R.A. 
Published: April 2011

AbstractUsing the Matrix-Assisted Pulsed Laser Evaporation (MAPLE) process developed at the Naval Research Laboratory, carbon nanotubes and carbon nanotube composite thin films have been successfully fabricated. This process involves dissolving or suspending the film material in a volatile solvent, freezing the mixture to create a solid target, and using a low fluence pulsed laser to evaporate the target for deposition inside a vacuum system. The collective action of the evaporating solvent desorbs the polymer/nanotube composite from the target. The volatile solvent is then pumped away leaving the film material on the substrate. By using this technique singlewall- nanotubes (SWN) have been transferred from the target to the substrate. The SWN sustain no observable damage during the deposition process. Using SWN in combination with polymers as the target material, SWN/polystyrene and SWN/polyethylene glycol composite films were made. These films can be deposited on a variety of substrates, e.g., Si, glass, plastic, and metal, using the same target and deposition conditions. SEM micrographs show that the SWN were uniformly distributed in the film. Using a simple contact mask, SWN composite films 20 um diameter patterns can be produced.
Electroluminescent Oxide Phosphor Thin Films Prepared by a Sol-gel Process
Authors: Minami Tadatsugu , Miyata Toshihiro , Shirai Tetsuya , Nakatani Toshikuni 
Published: April 2011

ABSTRACTGa2O3:Mn and (Ga2O3-SnO2):Eu thin films have been prepared by a sol-gel process. High luminance emissions were obtained in TFEL devices: green using a Ga2O3:Mn and red using a Ga2O3:Eu or a SnO2:Eu thin-film emitting layer. These sol-gel prepared devices were produced without using any vacuum processes and always exhibited higher luminances than equivalent devices prepared by r.f. magnetron sputtering: 40, 309 and above 1000 cd/m2 using SnO2:Eu, Ga2O3:Eu and Ga2O3:Mn phosphor thin films, respectively, in TFEL devices prepared by the sol-gel process and driven at 1kHz.
Effect of Excimer Laser Fluence Gradient on Lateral Grain Growth in Crystallization of a-Si Thin Films
Authors: Lee Minghong , Moon Seungjae , Hatano Mutsuko , Suzuki Kenkichi , Grigoropoulos Costas P. 
Published: April 2011

ABSTRACTIn order to clarify the relationship between excimer laser fluence gradient and the length of lateral grain growth, the laser fluence is modulated by a beam mask. The fluence distribution is measured by using a negative UV photoresist. The lateral growth length and the grain directionality are improved with increasing fluence gradient. Lateral growth length of about 1.5 [.proportional]m is achieved by using a single laser pulse without substrate heating on a 50 nm-thick a-Si film by enforcing high fluence gradient. Electrical conductance measurement is used to probe the solidification dynamics. The lateral solidification velocity is found to be about 7 m/s.
Fabrication of High-Density Carbon-Nanotube Coatings on Microstructured Substrates
Authors: Chen Zheng , Tzeng Yonhua , Liu Chao 
Published: April 2011

ABSTRACTFabrication and characterization of carbon nanotubes deposited on microstructured Ni substrate are presented. The highly active surface-area of the microstructured Ni substrate provides highdensity nucleation sites for carbon nanotubes. Coated fine Ni powder also serves as a catalyst for the nanotube growth. Hydrocarbon mixtures were used as the carbon source for the chemical vapor deposition process. Carbon nanotubes deposited on the microstructured Ni substrate were examined by SEM. An ultra high vacuum chamber was used to characterize the field emission properties of carbon nanotube coatings.
Raman Study of Single Wall Carbon Nanotube Doped by Alkali Metals
Authors: Bendiab N. , Anglaret E. , Righi A. , Sauvajol J.L. 
Published: April 2011

AbstractSingle wall carbon nanotube (SWNT) doped by alkali-metals are investigated by Raman scattering. For saturation-doped compounds, the most striking intrinsic features are two low-frequency peaks assigned to modes involving both radial motions of tubes and alkali-atoms vibrations. On the other hand, the evolution of the Raman spectra with doping was studied in-situ. Two different stable phases are identified and associated to distinct organizations of the tubes and of the alkali-atoms.
Anodized Aluminum Oxide Films as Nanostructured Template for the Grow of Carbon Nanotubes
Authors: Sui Y.C. , González-León J.A. , Bermùdez A. , Acosta D.R. , Feuchtwanger J. , Flores J.O. , Cui B.Z. , Mata-Zamora M.E. , Saniger J.M. 
Published: April 2011

AbstractA summary of our recent work related to the growth of carbon nanotubes (CNTs) inside the pores of anodized alumina oxide (AAO) films is presented. The surface topography of the AAO film was studied by atomic force microscopy, while the internal pore structure of the AOO templates was concluded from the shape of the CNTs obtained. The effect of the different experimental approaches and of the anodization voltage value on the features of the pores and CNTs is also discussed, as well as the catalytic effect in the acetylene pyrolysis of the Co particles and internal alumina walls. The CNTs wall structure observed by HRTEM and its implication on some physico-chemical properties of the CNTs are also presented.
Mechanical and Tribological Properties of Carbon Nanotubes Investigated with Atomistic Simulations
Authors: Ni Boris , Sinnott Susan B. 
Published: April 2011

AbstractAtomistic simulations are used to better understand the behavior of bundles of single- walled carbon nanotubes that have been placed between two sliding diamond surfaces. A many-body reactive empirical potential for hydrocarbons that has been coupled to a Lennard-Jones potential is used to determine the energies and forces for all the atoms in the simulations. The results indicate that the degree of compression of the nanotube bundle between the nanotubes has a significant effect on the responses of the nanotubes to shear forces. However, no rolling of the nanotubes is predicted in contrast to previous studies of individual nanotubes moving on graphite.
Evaluating the Purity of Single-Wall Nanotube Materials
Authors: Dillon A.C. , Gennett T. , Parilla P.A. , Alleman J.L. , Jones K.M. , Heben M.J. 
Published: April 2011

AbstractCarbon single-wall nanotubes (SWNTs) have a variety of unique physical, electronic and mechanical properties. However, the SWNTs must be thoroughly purified if they are to be used in the wide array of projected applications and basic studies. Although numerous purification schemes have been employed in the literature, none of them provides an accurate estimate of the SWNT content in the final materials. Here we describe a simple 3-step purification process coupled to an accurate method for determining SWNT wt.% contents in both the crude and purified samples. We employ a laser vaporization synthesis technique and take care to avoid both forming graphite-encapsulated metal particles and incorporating sputtered target material into the collected soot. It is then possible to employ a dilute nitric acid reflux to digest the metal particles and to functionalize and redistribute the non-nanotube carbon fractions in the soots forming a uniform and reactive coating on the SWNTs. This coating is selectively removed by oxidation in air at 550 °C. Thermogravimetric analysis (TGA) and inductively coupled plasma spectroscopy (ICPS) are used to evaluate the purity of the material at each step of the process, and illustrate that the crude materials contain 6 wt.% metal and 10-35 wt.% SWNTs. The purified materials are found to be >98 wt.% pure with metal contents of < 1 wt.%. Using the 98 wt.% pure materials as a yardstick, we are able to evaluate the accuracy of several other methods commonly employed in determining nanotube purity levels including transmission and scanning electron microscopies (TEM and SEM) and Raman spectroscopy. We show that determining nanotube contents in various materials requires careful scrutiny and the application of multiple techniques.