bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxidation Behavior and Electrical Conductivity between Ln0.8Sr0.2MnO3 Cathode and Crofer 22 APU with Spinel Coatings
Authors: Ledukhovskaya Nataliya , Frolova Elena , Korovkin Eugeniy , Sinitsyn Vitaly , Bredikhin Sergey I.
Published: September 2009

The modified method of electrostatic spray pyrolysis was designed to apply protective coatings based on Mn-Co spinel to ferritic stainless steels (Crofer22APU and 08X18T1). The comparative thermogravimetric (TG) studies of ferrite stainless steels with and without protective coatings were carried out. The electrochemical characteristics of protective coatings exposed to long current loading were studied. The formation of the Mn-Cr spinel observed and studied at the contact between the ferrite stainless steel and the Mn-Co spinel. The coatings of Mn-Co spinel were shown preventing formation of continuous Cr2O3 oxide film on the stainless steel surface.
The Influence of Water Vapor and SO2 on the Durability of Solid Oxide Fuel Cell
Authors: Liu Run Ru , Kim S.H. , Shiratori Yusuke , Oshima Toshihiro , Ito Kohei , Sasaki Kazunari
Published: September 2009

The influences of SO2 and water vapor in air were investigated for (La0.8Sr0.2)0.98MnO3 (LSM) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathodes by measuring cell voltage at a constant current density of 200 mA cm-2 and the operational temperature of 800 oC. The results of 1000 h durability tests suggest that SO2 and water vapor in the ambient air little affect the performance of both cathode materials under typical operational conditions.
Degradation of Symmetrical Cathode-Interlayer-Electrolyte Cells
Authors: Martinez-Amesti Ana , Larrañaga Aitor , Rodriguez-Martinez Lide M. , No M.Luisa , Arriortua María Isabel
Published: September 2009

The time dependent degradation of La0.6Sr0.4FeO3 cathode with ceria doped samaria interlayer has been studied. Four cell have been tested over 1000 hours with different interlayer thickness and porosities to investigate the influence of these parameters on the degradation of electrochemical behavior. The cells were kept for 1000 h at 800ºC in air without current. Identical cells were prepared and measured for comparison, showing little or no degradation.
Accelerated Degradation of SOFC Cathodes by Cr Vapors
Authors: Horita Teruhisa , Xiong YuePing , Yoshinaga Masashi , Kishimoto Haruo , Yamaji Katsuhiko , Brito Manuel , Yokokawa Harumi
Published: September 2009

Among the degradation factors of SOFCs, Cr poisoning is one of the important issues for long-term operation. A pre-oxidized Cr metal was used to generate Cr vapors for accelerating the Cr poisoning at cathodes. Cathodic polarization currents decrease with time due to the deposition of Cr at active parts of cathodes. The concentration level of Cr in the porous cathodes (La0.8Sr0.2MnO3 (LSM)) and La0.8Sr0.2FeO3 (LSF)) was determined by secondary ion mass spectrometry (SIMS). The concentration level of Cr was 100-2000 ppm depending on cathode materials and position. For LSM cathode, a maximum of Cr concentration was observed around the LSM/electrolyte interface, while no condensation at the LSF/electrolyte interface. The atomic numbers of Cr deposited in the LSF cathode is estimated to be about 21-25% of the supplied Cr, which is about 1.8 times larger numbers of Cr in LSM. The electrochemical performance of LSF is relatively high compared with that of LSM.
Systematic Study of Chromium Poisoning of LSM Cathodes - Single Cell Tests
Authors: Neumann Anita , Menzler Norbert H. , Vinke Ico , Lippert Hannelore
Published: September 2009

Chromium poisoning of solid oxide fuel cell cathodes is up to now considered as one major factor which limits life-time and is responsible for degradation. Still unclear are to which extend chromium poisoning is responsible and what the basic degradation mechanism is. At Forschungszentrum Jülich this ambiguity should be clarified by two ways: firstly the post-mortem analysis of cells operated within a stack and secondly by carrying out single cell tests with varied chromium releasing sources and operating conditions. This presentation summarizes the results of approximately 60 single cell tests. The experiments were carried out with variation of operation time, current density applied and the chromium source. The cells are characterized for their degree of degradation, for their chromium content and change in microstructure. The results show that cells solely degrade strongly when current density was applied and a strong chromium source was present and support an electrochemical interaction mechanism.
Chromium Poisoning of LSM Cathodes - Results from Stack Testing
Authors: Menzler Norbert H. , Vinke Ico , Lippert Hannelore
Published: September 2009

Chromium poisoning of solid oxide fuel cell cathodes is up to now considered to be a major factor which limits life-time and is responsible for degradation. Still unclear is to which extend chromium poisoning is responsible for degradation and what the basic degradation mechanism is. The Forschungszentrum Jülich tries to clarify this ambiguity in two ways: firstly by post-mortem analysis of cells operated within a stack and secondly by carrying out single cell tests with varied single cell measurement equipment. This presentation summarizes the post-mortem characterization of approximately fifteen stack tests. The two major parameters varied were the applied current density during operation and the operation time. SEM micrographs and wet chemical analysis of the cell materials are presented. Up to now a direct correlation between deposited amount of chromium within the LSM cathode and the degradation rate of the stack could not be established.
Electrochemical Property of Cr-containing Cathode Materials for Metal-supported Solid Oxide Fuel Cell
Authors: Baek Seung-Wook , Jeong Jihoon , Lee Sanghyub , Bae Joongmyeon
Published: September 2009

Metal-supported solid oxide fuel cell (SOFC) shows innovative advantages to solve the crucial problems of ceramic-supported SOFC such as sealing and mechanical strength. However, fabrication of metal-supported cell is a critical issue to facilitate the technology. Especially, coating and heat treatment of cathode layer is a difficult step due to oxidation and deformation of metal support during sintering of cell to obtain high electrochemical performance. In present research, electrochemical property of several Cr-containing cathode materials is investigated to apply to metal-supported SOFC. Cr-containing cathodes are sintered at reducing atmosphere to minimize oxidation and deformation of metal support.
Work Function Control on High K Metal Gate Stacks
Authors: Robertson John
Published: September 2009

The paper summarizes the development of metal gate materials and the control of the effective work function for use in future Si field effect transistors. The Schottky barrier heights of metals on HfO2 are modeled, for ideal interfaces of various stoichiometries and for interfaces with defects, and also for dipole layers.
Effects of the Semiconductor Substrate Material on the Post-breakdown Current of MgO Dielectric Layers
Authors: Miranda Enrique , O'Connor Eamon , Hughs Greg , Casey Patrick , Cherkaoui Karim , Monaghan Scott , Long Rathnait , O'Connell Dan , Hurley Paul
Published: September 2009

The post-breakdown (BD) current-voltage (I-V) characteristics in MgO/Si and MgO/InP stacks with metal gate were investigated. We show that both stacks exhibit the soft and hard BD conduction modes and that the magnitude of the post-BD currents depends statistically on the substrate material, being larger in the case of the InP samples. This is contrary to what happens with the current in the fresh devices, which irrespective of the InP surface treatment, is larger for the Si samples. A comparative analysis of the post-BD conduction characteristics and direct evidences of the localized thermal effects on the metal gate electrode of both structures are presented.
InAs-Channel Metal-Oxide-Semiconductor HEMTs with Atomic-Layer-Deposited Al2O3 Gate Dielectric
Authors: Chang Chia-Yuan , Chang Edward Yi , Huang Wei-Ching , Su Yung-Hsuan , Trinh Hai-Dang , Hsu Heng-Tung , Miyamoto Yasuyuki
Published: September 2009

The performance of n-type metal-oxide-semiconductor HEMTs with an InAs-channel using atomic-layer-deposited Al2O3 as gate dielectric has been fabricated and evaluated. The device performances of a set of scaled transistors with different gate dielectric thicknesses of 3, 5 and 7 nm have been investigated to determine whether the architecture of Al2O3 dielectric on InAs-channel HEMT can demonstrate good properties at low bias conditions for high-speed, high performance CMOS applications. The results indicate that the high-performance InAs-channel MOS-HEMTs with an ALD Al2O3 gate dielectric are promising candidates for advanced post-Si CMOS applications.
Barrier Characterization at Interfaces of High-Mobility Semiconductors with Oxide Insulators
Authors: Afanas'ev Valeri V. , Stesmans Andre
Published: September 2009

Internal photoemission and photoconductivity experiments are used to characterize interfaces of high-mobility semiconductors GaAs, InxGa1-xAs, Ge, and Si1-xGex with metal oxide insulators. Compared to silicon, formation of a narrow-gap interlayer and composition-sensitive semiconductor band structure are revealed as the most influential factors affecting the interface barriers.
Dielectric Properties of Thin Hf- and Zr-based Alkaline Earth Perovskite Layers
Authors: Lupina Grzegorz , Dudek Piotr , Kozłowski Grzegorz , Dąbrowski Jarek , Lippert Gunther , Müssig Hans-Joachim , Schroeder Thomas
Published: September 2009

Thin layers of high dielectric constant materials are of special interest for memory, logic, and passive microelectronic applications. Memory storage capacitors based on these materials should exhibit high capacitance densities and low leakage currents. Here, we investigate a group of Hf- and Zr-based alkaline earth perovskites for this application. It is found that thin layers of polycrystalline BaHfO3, SrHfO3, and BaZrO3 can provide capacitance densities about 2 times higher than that of amorphous HfO2. Post deposition annealing above ~ 700{degree sign}C is a crucial processing step required for obtaining the cubic perovskite phase with high dielectric constant.
Electron Beam Induced Orientation Selective Epitaxial Growth of CeO2(100)/Si(100) Structures using Absorption Electron Imaging System
Authors: Inoue Tomoyasu , Shida Shigenari
Published: September 2009

After the discovery of orientation selective epitaxy (OSE) of CeO2(100) and CeO2(110) layers on Si(100) substrates by substrate bias control, we have expanded into OSE by electron beam irradiation, instead of substrate bias. In order to control the electron beam irradiation area, we applied an absorbed electron imaging system to the reactive magnetron sputtering equipment. Analyses were made on the absorbed electron current profile along Si substrates and the current components.
Progress Towards Passivation of High-Mobility Channels
Authors: Houssa Michel , Afanas'ev Valeri V. , Stesmans Andre , Meuris Marc , Heyns Marc M.
Published: September 2009

The need for high-k gate dielectrics and metal gates into advanced integrated circuits has re-opened the door to germanium and III-V compounds as potential replacements for silicon channels, offering the possibility to further increase the performances of metal-oxide-semiconductor devices, as well as adding new circuit functionalities. A fundamental issue related to high-mobility channels is the passivation of their interfaces, i.e. achieving a low density of interface defects, approaching state of the art Si-based devices. Promising approaches for the passivation of Ge channels are discussed and insights obtained by combining experimental characterization techniques with first-principles simulations are highlighted.
Interface Engineering of a Metal/ High-k/ Semiconductor Layered Structure by Water Vapor Discharge
Authors: Muraoka Kouichi
Published: September 2009

The suppression of interfacial reactions in a tungsten (W)/hafnia (HfO2)/germanium (Ge) structure by water (H2O) vapor discharge was demonstrated. In the case of a HfO2/Ge dioxide (GeO2)/Ge structure, it was confirmed that the thickness of the interfacial GeO2 layer was decreased by H2O vapor discharge. Moreover, in the case of a W/hafnium (Hf)/Ge structure, it was found that such discharge can also achieve the formation of a W/HfO2/Ge structure with abrupt interfaces, without the oxidation of W or Ge. These results suggest that the selective removal of interfacial reaction layers and residual oxygen atoms in metal gate electrodes by hydrogen (H) radicals and the selective repair of oxygen-deficient high-dielectric-constant (high-k) insulators by hydroxyl (OH) and oxygen (O) radicals occur simultaneously during H2O vapor discharge. This means that thermodynamically selective etching and oxidation conditions can be realized using only H2O discharge.
Annealing-temperature Dependence of Compositional Depth Profiles and Chemical Bonding States of CeOx/LaOx/Si and LaOx/CeOx/Si Structure
Authors: Nohira Hiroshi , Kon Youichirou , Kitamura Koji , Kouda Miyuki , Kakushima Kuniyuki , Iwai Hiroshi
Published: September 2009

We have investigated the influence of post deposition annealing (PDA) on compositional depth profiles and chemical structures of CeOx/LaOx/Si(100) and LaOx/CeOx/Si(100) interfaces by angle-resolved X-ray photoemission spectroscopy. Analyses of Ce 3d and O 1s spectra show that a Ce oxidation state changes from Ce4+ to Ce3+ by PDA in N2 at and above 500{degree sign}C and changes from Ce3+ to Ce4+ by PDA in O2 at 300{degree sign}C. This implies that a Ce oxidation state can be controlled by changing the condition of PDA. The diffusion of Ce and La atom occurs at CeOx/LaOx interface by PDA above 500{degree sign}C.
Comparison of Lateral Non-uniformity Phenomena between HfO2 and SiO2 from Magnified C-V Curves in Inversion Region
Authors: Cheng Jen-Yuan , Huang Chiao-Ti , Lu Hui-Ting , Hwu Jenn-Gwo
Published: September 2009

A methodology to evaluate the non-uniformity phenomena in MOS structure from magnified C-V curve is proposed. With considering the effective oxide charge influence on inversion to deep depletion region, the localized injection of avalanche hot carriers from Si-substrate will induce highly leaky areas at Oxide/Silicon interface. These areas can be evaluated quantitatively via local depletion capacitance model in MOS device. Through fitting C-V curves from inversion to deep depletion region with the uniform area ratio K, the index of oxide quality can be obtained. For SiO2, K values increase with EOTs which means the interfacial quality gets better when SiO2 become thicker. For HfO2, K values decrease with EOT which means thicker HfO2 stack gets poor interfacial quality. The uniform area ratio K of HfO2 is lower than SiO2 due to the inherent property of HfO2 film which contains too many traps because they are not as perfect as SiO2.
Crystallographic Orientation Dependent Electrical Characteristics of La2O3 MOS Capacitors
Authors: Nakayama Hiroto , Kakushima Kuniyuki , Ahmet Parhat , Ikenaga Eiji , Tsutsui Kazuo , Sugii Nobuyuki , Hattori Takeo , Iwai Hiroshi
Published: September 2009

Effect of substrate surface orientation on the properties of La2O3 MOS capacitors was investigated. The dielectric-thickness dependence on VFB indicated that the (110) sample contains smaller amount of fixed charge than the other samples of (100) and (111). The EOT after post-metallization annealing also varied with the orientation: larger value for (111) than the other. The x-ray photoemission spectroscopy revealed that the growth of SiO2-rich silicate phase of low permittivity depends on the orientation and can change EOT. The results suggest that the (110) is preferable for small EOT and adequate VFB value when the interface-state density is significantly reduced.
Solution-Based Fabrication of High-k Dielectrics Using Oxide Nanosheets
Authors: Osada Minoru , Akatsuka Kosho , Ebina Yasuo , Funakubo Hiroshi , Takada Kazunori , Sasaki Takayoshi
Published: September 2009

We report a novel procedure for fabricating high-k dielectric nanofilms by using titania nanosheet as a building block. Langmuir-Blodgett deposition using atomically flat SrRuO3 or Pt substrates is advantageous as a means of fabricating atomically uniform multilayer high-k nanofilms. High-resolution transmission electron microscopy revealed that these multilayer nanofilms are composed of a well-ordered lamellar structure without an interfacial dead layer. These nanofilms exhibited both high dielectric constant (~125) and low leakage current density (J < 10-7 A/cm2) even for thicknesses as low as 10 nm. These results indicate that titania nanosheet is a very promising candidate as a high-k nanoblock, and its bottom-up fabrication provides new opportunities for the development of high-k devices.
Long TDDB Lifetime of SiO2 Film by Controlling Degradation Rate and SiO2/Si Micro-roughness
Authors: Kabe Yoshiro , Kitagawa Junichi , Hirota Yoshihiro , Sato Shinkuro , Sometani Mitsuru , Hasunuma Ryu , Yamabe Kikuo
Published: September 2009

Dielectric characteristics of ~9nm thick SiO2 film formed by the combination of plasma and thermal oxidation were studied. TDDB characteristics were applied to evaluate the degradation rate and breakdown lifetime of the oxides. AFM observation was used to evaluate the roughness of SiO2 surface and interface. The two-dimensional nonuniformity of degradation under current stress was investigated using SISuR method. It was found that the SiO2 film by the combination of plasma and thermal oxidation inherited the advantage of the low degradation rate of thermal oxide and the advantage of flat SiO2 surface and interface of plasma oxide, which led to less localized weak spots under current stress. We conclude that the appropriate mixture of oxidation methods can improve both the degradation and breakdown lifetime of SiO2 film.
DLTS of ALD HfO2 on s-Si/SiGe/Si: Effects of s-Si Thickness and Surface Nitridation
Authors: Yu Liya , George Rozgonyi George , Shrestha Pragya , Gu Diefeng , Baumgart Helmut
Published: September 2009

MOS capacitors have been used as depth-dependent probing tools for MOS-DLTS studies of ALD HfO2 on s-Si/SiGe/Si composite samples. Surface nitridation prior to HfO¬2 deposition was carried out to improve the HfO2/s-Si interface by suppressing hafnium silicate interlayer formation. The overall effects of nitridation on the HfO2/s-Si interface and the s-Si/SiGe bulk region with different strained Si layer thicknesses were studied. The relationship between DLTS peak amplitude and pulsing time indicates the emission source in bulk region is related with Ge decorated dislocations and in the interface region it originates from the HfO2/s-Si interface. In the s-Si/SiGe bulk region, nitridation reduces the trap concentration and shifts trap energy level toward mid-gap. For the interface, nitridation shifts trap energy level toward valence band and reduces hole capture cross section significantly.
Effects of the Inductively Coupled Plasma Nitridation Process on the Reliability of HfAlOx Thin Films
Authors: Chang Kow-Ming , Chen Bwo-Ning , Su Ming-Shen
Published: September 2009

High-k dielectric such as Hf-based dielectric has been considered to be inevitable for 45-nm CMOSFET technology node. The incorporation of Al in Hf-based dielectrics has been proven as a solution to the problem about thermal stability. Moreover, there have been some researches which describe that the reliability of the high-k dielectrics could be improved by the nitridation process. In this study, we examine the effect of different inductively coupled plasma (ICP) nitridation processes on the reliability of HfAlOx thin films. The hysteresis, stress induced leakage current (SILC) and constant voltage stress (CVS) characteristics of the nitrided HfAlOx thin films were preformed to prove the improvement effect of the plasma nitridation. Based on our experimental results, the ICP nitridation process would be an effective technology to improve the reliability of HfAlOx thin films.
Transition Metal Binary Oxides for ReRAM Applications
Authors: Spiga Sabina , Lamperti Alessio , Cianci Elena , Volpe Flavio G. , Fanciulli Marco
Published: September 2009

Resistive switching characteristics of polycrystalline nickel oxide were studied for non volatile memory applications. NiO was deposited by atomic layer deposition and electron beam evaporation on silicon and various metal bottom electrodes. After an initial electroforming step, NiO based devices with Pt top electrode and Si, Pt, Ni, TiN or W bottom electrodes exihibit reproducible unipolar switching. The film physical properties as well as electrode combinations influence the programming voltages and resistance window. While Pt and Si electrodes give a reduced dispersion of programming voltages and currents, the largest resistance window (up to four order of magnitude) is obtained when W is used. Preliminary data on the switching properties of amorphous Nb2O5 and polycrystalline ZrO2 films are also discussed.
Improved Device Characteristics in Charge-Trapping-Engineered Flash Memory Using High-k Dielectrics
Authors: Chin Albert , Lin S. H. , Tsai C. Y. , Yeh F. S.
Published: September 2009

The much shallower trap energy in Si3N4 of [poly-Si]-SiO2-Si3N4-SiO2-Si (SONOS) charge-trapping flash (CTF) device than conventional poly-Si floating gate flash is the fundamental challenge for CTF device. We have pioneered the high-k trapping layer CTF memory to increase the trapping energy, where the AlGaN has a large conduction band offset to barrier oxide layer close to conventional poly-Si floating gate. Further device performance improvement is achieved using the novel Charge-Trapping-Engineered Flash (CTEF) device with double barriers for carrier confinements and double shallow-/deep-trapping layers for charge storage. Excellent memory device integrities of large extrapolated 10-year retention of 3.8 V at 150oC, 4 logic levels MLC operation, very fast 100 us write speed and good 100,000 cycling stress are measured at the same time. These excellent results may allow further down-scaling the flash memory for additional nodes.
Failure Analysis of Single and Dual nc-ITO Embedded ZrHfO High-k Nonvolatile Memories
Authors: Yang Chia-Han , Kuo Yue , Lin Chen-Han , Kuo Way
Published: September 2009

The nanocrystaline indium tin oxide (nc-ITO) embedded Zr-doped HfO2 (ZrHfO) high-k dielectric has been fabricated into nonvolatile memories with a low leakage currents, a large charge-storage capacity, and a long charge retention time. Recently, it has demonstrated that the dual-layer nc-ITO embedded capacitor has a charge trapping density more than double that of the single-layer nc-ITO embedded capacitor with a faster charging rate. In this paper, authors investigated the charge transport and the breakdown mechanisms of the single- and dual-layer nc-ITO embedded ZrHfO thin films. The charges transport followed the F-N tunneling mechanism. In addition, the dual-layer nc-ITO embedded capacitor has smaller breakdown strength and a larger leakage current than the single-layer nc-ITO embedded capacitor.
Application of ALD High-k Dielectric Films as Charge Storage Layer and Blocking Oxide in Nonvolatile Memories
Authors: Zhu Xiaoxiao , Gu Diefeng , Li Qiliang , Baumgart Helmut , Ioannou Dimitris , Suehle John , Richter Curt
Published: September 2009

ALD high-k dielectric films of HfO2 were utilized for the charge trapping layer and Al2O3 for the blocking oxide layer during fabrication of several Metal/Al2O3/HfO2/SiO2/Si (MAHOS) non-volatile memory (NVM) cells based on Si nanowire channel. Si nanowires grown from predefined Au catalysts were integrated into memory devices by using a self-aligning approach. For benchmarking and comparison a different Metal/SiO2/HfO2 /SiO2/Si (MOHOS) nonvolatile memory cell with a SiO2 blocking layer was also processed. All the Si nanowire nonvolatile memory cells show a large memory window, good endurance and retention, however, the MAHOS cells with Al2O3 blocking layers outperform the MOHOS cell with SiO2 blocking layer.
Metal/High-k/Metal Nanocrystal/SiO2 Gate Stacks for NAND Flash Applications
Authors: Mahapatra Souvik , Singh Pawan K.
Published: September 2009

The viability of metal / Al2O3 / metal (Au, Pt) nanocrystal / SiO2 gate stacks as a NAND Flash memory is studied. Fabrication of metal NC and electrical characterization of write/erase performance, retention and cycling endurance is studied.While stacks having single layer Au and Pt dots do not show proper reliability, dual layer Pt stacks show excellent reliability. The viability of MLC operation is also studied.
Hot Wire Chemical Vapor Deposition: Recent Progress, Present State of the Art and Competitive Opportunities
Authors: Schropp Ruud E.
Published: September 2009

Hot Wire CVD (also called Catalytic CVD or initiated CVD) is an elegant low pressure deposition technique for the deposition of functional films, both inorganic and organic, based on the decomposition of precursor sources at a heated metallic surface. The conformal deposition of thin films on rigid substrates or flexible foil substrates, whether in-line or batch type, is very straightforward, since it is plasma-free (i.e. without the risk of a damaging bombardment of energetic ions) and it is easily scalable. An increasing variety of thin film materials can be obtained with this method, with good feedstock gas utilization and high deposition rate. Progress has been made in establishing stable and reproducible conditions for the hot catalytic wires used for efficient decomposition of the source gases. In this paper we discuss some of the current research issues in this field.
Gas Phase Deposition and Characterization of (Si)-B-C Ceramics
Authors: Chollon Georges , Langlais Francis , Berjonneau Jerome
Published: September 2009

B-C and Si-B-C coatings have been prepared by chemical vapour deposition (CVD) respectively from CH4/BCl3/H2 and MTS/BCl3/H2 precursor mixtures at low temperature (800-1050{degree sign}C) and reduced pressure (12kPa). The kinetic laws (including apparent activation energy and reaction orders) related to the deposition process were determined within the regime controlled by chemical reactions. A wide range of coatings, prepared in various CVD conditions, were characterized in terms of morphology (SEM), structure (TEM, Raman spectroscopy) and elemental composition (Auger electron spectroscopy), in the as-deposited state and after heat treatment. A correlation between the various experimental approaches has supported a discussion on the chemical steps involved in the deposition process.
Electrical Properties of Plasma-Deposited Silicon Oxide Clarified by Chemical Modeling
Authors: Kovalgin Alexey , Boogaard Arjen , Brunets Ihor , Aarnink Tom , Wolters Rob
Published: September 2009

Our study is focused on Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon dioxide films at low temperatures (< 150 oC) using Inductively Coupled (IC) High-Density (HD) plasma source. We recently fabricated Thin Film Transistors (TFTs) with high-quality ICPECVD gate oxides, which exhibited a competitive performance. For better understanding of the influence of deposition parameters on both the deposition kinetics and oxide quality, we have modeled the Ar-SiH4-N2O plasma system with 173 chemical reactions. We simulated concentrations of 43 reactive species (such as e.g. SiHx radicals and SiHx+ (x=0-3) ions, polysilanes, SiO, SiN, SiH3O, SiH2O, HSiO, etc., as well as atomic hydrogen, nitrogen and oxygen) in plasma. We further used our simulations to qualitatively explain (in terms of concentrations of the reactive species) the influence of SiH4/N2O gas-flow ratio and total gas pressure on film electrical properties and deposition rate.
A Density Functional Theory Study of Chlorosilanes Polymerization in Silicon Epitaxy
Authors: Moscatelli Davide , Dossi Marco , Fiorucci Alessandro , Masi Maurizio
Published: September 2009

The decomposition kinetics of chlorosilanes have been so far investigated up to the lower molecular weight fragments, not regarding the generation of telomeres. In this work Quantum Chemistry was employed to investigate gas phase polymerization of chlorosilanes in operating conditions proper to silicon epitaxy. Thermodynamic and kinetic parameters, molecular structures and transition state geometries were determined with Density Functional Theory (DFT), resulting in a series of fast condensation-reactions bringing to the production of telomeres. In particular, a large number of linear, branched and cyclic silicon- compounds were analyzed (up to Si6Clx species). Finally the kinetic scheme was embedded in a reactor simulation code, where significant amounts of such species were obtained.
Investigation of the Thermal Decomposition of Triethylgallium Using in situ Raman Spectroscopy and DFT Calculations
Authors: Lee Jooyoung , Kim Young Seok , Anderson Timothy J.
Published: September 2009

Homogeneous thermal decomposition pathways (C2H5)3Ga (TEGa) were followed using in situ Raman spectroscopy measurement in an up-flow, cold-wall CVD reactor. The results of Density Functional Theory (DFT) calculations were used to assign measured Raman bands to the decomposition products (Et)3Ga, (DEGa)2, (Et)GaH-Ga(Et)2 and (Et)GaH-GaH2. The results of this study are consistent with both β-hydride elimination and homolysis pathways. The measured composition and temperature profiles were used to estimate rate constants using a 2-D detailed reactor model. DFT calculations using B3LYP/LanL2DZ model chemistry were performed to screen possible routes and estimate their reaction rate parameters.
N-doped Titania Thin Films, Prepared by Atmospheric Pressure Chemical Vapour Deposition: Enhanced Visible Light Photocatalytic Activity and Anti-microbial Effects
Authors: Dunnill Charles W. , Aikin Zoie Aikin , Pratten Johnathan , Wilson Michael Wilson , Parkin Ivan
Published: September 2009

Titanium dioxide (TiO2) films have been highly commercialized as photocatalyst coatings with applications in technologies such as self-cleaning glass. There is however interest in developing superior coatings that operate under domestic lighting conditions for cleaning and anti-microbial applications in healthcare environments. One such approach to improve on TiO2 is to shift the band-gap from UV into the visible region of the spectrum, thus harvesting a greater proportion of solar energy and allowing the films to work under indoor-lighting conditions. This paper shows an example of the selective doping of TiO2 with beneficial results in the quest for visible light photocatalyst with anti-microbial properties.
A Comparative Study of the Photoinduced Properties of TiO2/SiO2 and TiO2/ZnO/SiO2 Layers Prepared by Chemical Routes
Authors: Vernardou Dimitra , Spanakis Emmanouil , Vlachou Katerina , Kalogerakis Giannis , Costello Justin , Koudoumas Emmanouil , Katsarakis Nikos , Pemble Martyn
Published: September 2009

Μetal oxide layers (TiO2 and TiO2/ZnO) are deposited via chemical routes on SiO2-precoated glass substrates and their properties were examined. As shown, TiO2/ZnO/SiO2 can be an ideal 'sandwich structure' exhibiting both reversible photoinduced hydrophilicity, reaching a near zero contact angle, and enhanced photocatalytic activity, degrading stearic acid by almost 52 %. The results indicate that the coexistence of anatase TiO2 and high surface area ratio is necessary for the good photoinduced properties of the samples. The capability to control the photoinduced properties of the layers can be significant for certain applications such as self-cleaning windows.
Selective Growth of B- and C-doped SiGe Layers in Unprocessed and Recessed Si Openings for pMOSFET Application
Authors: Kolahdouz Mohammadreza , Tabib Zadeh Adibi Pooya , Afshar Farniya Ali , Trybom Erik , Di Benedetto Luigi , Shayestehaminzadeh Mohammad , Radamson Henry H.
Published: September 2009

This work presents pattern dependency of selective epitaxial growth of boron- or carbon-doped SiGe layers in recessed or unprocessed openings. The layer profile and quality of epi-layers were found to be dependent on chip layout and the growth parameters. Carbon- and boron-doping compensated the strain in SiGe layers and when both dopants are introduced the strain reduction was additive. The incorporation of boron and carbon in SiGe matrix showed to be a competitive action. The concentration of carbon decreased when the boron amount increased in SiGe layers with higher Ge content.
An Investigation of the Gas Phase and Surface Chemistry Active During the PECVD of nc-Silicon: A Detailed Model of the Gas Phase and Surface Chemistry
Authors: Cavallotti Carlo , Rondanini Maurizio , Moiseev Tamara , Chrastina Danny , Isella Giovanni
Published: September 2009

In this work we present a detailed model that is able to describe the elementary chemistry active in the gas phase and on the surface during the plasma deposition of nc-Silicon films. The model is validated by comparison with mass spectrometry data measured in situ in a low energy PECVD plasma reactor. It was found that the main growth precursors are SiH3, SiH2 and SiH radicals, with the more dehydrogenated radicals becoming dominant at high hydrogen dilution, and that during the film growth more than 90% of the surface is covered by hydrogen.
Multiscale Simulation and Optimization of an Atomic Layer Deposition Process in a Nanoporous Material
Authors: Dwivedi Vivek , Adomaitis Raymond A.
Published: September 2009

A multiscale simulator for alumina film growth inside a nanoporous material during atomic layer deposition (ALD) is developed. The model combines a continuum description at the macroscopic level of precursor gas transport inside a nanopore during exposure to each of the two precursor species (trimethyaluminum and water) with a kinetic Monte Carlo (kMC) simulation of the film growth on the microscopic scale. Simulation results are presented for both the kMC simulation and for the multiscale system, the latter illustrating how nonuniform deposition along the nanopore can occur when insufficient precursor exposure levels are used.
CaCu3Ti4O12 Thin Films for Capacitive Applications: MOCVD Synthesis and Nanoscopic/microscopic Characterization
Authors: Lo Nigro Raffaella , Toro Roberta G. , Catalano Maria Rita , Malandrino Graziella , Fragalà Ignazio L. , Fiorenza Patrick , Raineri Vito
Published: September 2009

CaCu3Ti4O12 (CCTO) thin films have been successfully deposited by Metal Organic Chemical Vapor Deposition (MOCVD) technique. An appealing approach based on a molten multi-component precursor source has been applied. The molten mixture consists of the Ca(hfa)2•tetraglyme, Ti(tmhd)2(O-iPr)2, and Cu(tmhd)2 [Hhfa= 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme= 2,5,8,11,14-pentaoxapentadecane; Htmhd= 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr= iso-propoxide] precursors. Film complete structural and morphological characterizations have been carried out using several techniques [X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM)].The dielectric properties have been evaluated at microscopic as well as at nanoscopic scale by scanning impedance microscopy.
Rare-Earth Based Oxide and Nitride Thin Films Employing Volatile Homoleptic Guanidinate Precursors
Authors: Milanov Andrian P. , Thiede Tobias , Hellwig Malte , Parala Harish , Bock Claudia , Becker Hans-Werner , Ngwashi Divine , Cross Richard , Paul Shashi , Kunze Ulrich , Fischer Roland , Devi Anjana
Published: September 2009

The application of the metalorganic compound tris(N,N'-diisopropyl-2-dimethlyamidoguanidinato)gadolinium(III) (1) as a precursor for MOCVD of Gd2O3 is discussed. Depositions were carried out in the presence of oxygen at reduced pressure and varying the substrate temperature in the range 300 - 700{degree sign}C. Employing a multi-technique approach (XRD, SEM, AFM, EDX, RBS, SNMS, SE, C-V), variations of the growth characteristics and film properties with deposition temperature are studied in terms of crystallinity, structure, surface roughness, composition, optical and electrical properties. In addition, the use of 1 as single source precursor for the MOCVD of GdN thin films is also demonstrated.
Remarkable Influence of molecular structure of N,N'-unsymmetrically substituted 1,3-amidinate and -guanidinate on the Volatility and the Thermal Stability of Precursors for HfO2 Films via Liquid Injection-MOCVD
Authors: Eleter Mohamad , Daniele Stephane , Brize Virginie , Dubourdieu Catherine , Lachaud Christophe , Blasco Nicolas , Pinchart Audrey
Published: September 2009

The identification of appropriate ligand-metal combinations, which successfully present the features of : (i) having acceptable melting point, (ii) being more thermally stable than hafnium alkylamides, (iii) having sufficient volatility for vapor phase distribution and (iv) enabling the deposition by LI-MOCVD and ALD of hafnium containing thin films, should go through new generations of well-behaved molecular precursors. We report herein the chemical design and full characterizations of a portfolio of novel mono- and di- amidinate and guanidinate alkylamide hafnium complexes of N,N'-unsymmetrically substituted 1,3-amidinate and 1,3-guanidinate [R'-N=CX-NR"]xHf(NR2)4-x (R'≠ R" = Et, iPr, tBu ; R = Me or Et ; X = Me or NMe2 ; x = 1 or 2). We will exemplify the remarkable influence of the molecular structure on the melting point, the volatility and the thermal stability (see figure 1) and the nature (cubic, monoclinic) of HfO2 thin films by LI-MOCVD.
Atomospheric Pressure SiC Film Deposition at Low Temperatures Using SiH3CH3 and HCl Gases
Authors: Habuka Hitoshi , Ohmori Hiroshi
Published: September 2009

Silicon carbide (SiC) film is formed at the temperatures lower than 800 oC on a silicon surface by means of chemical vapor deposition using monomethylsilane (MMS) gas along with hydrogen chloride gas in ambient hydrogen at atmospheric pressure. A 0.2 um-thick SiC film, obtained at 800 oC and at the hydrogen chloride gas concentration larger than that of MMS gas, showed specular surface having the root-mean-square microroughness of 0.7 nm. At this temperature, the film formation saturated within 10 seconds. At the temperatures lower than 600 oC, SiC film could be formed at the silicon surface, which was cleaned in ambient hydrogen at 1100 oC immediately before the film deposition.
Influence of N2 and H2 Gas Flow Rates on Properties of N-type Nanocrystalline 3C-SiC:H Thin Films Prepared by Hot-wire Chemical Vapor Deposition
Authors: Tabata Akimori , Hoshide Yoshiki , Kondo Akihiro
Published: September 2009

N-type nanocrystalline cubic SiC:H thin films were prepared by a hot-wire chemical vapor deposition from SiH4/CH4/H2/N2 and the structural and electrical properties were investigated. As the N2 gas flow rate, F(N2), was increased, the intake of N atoms into the films increased, which caused the degradation of the crystallinity of the films. Therefore, in the region of the small intake of N atoms the conductivity of the N-doped films increased with the increase in F(N2), though, in the region of the large intake of N atoms the conductivity reduced, resulting from the pronounced degradation of the crystallinity. An increase in the H2 gas flow rate resulted in the improvement of the crystallinity and, consequently, the conductivity.
Morphological and Structural Study of CVD MoO3-Cr2O3 Films
Authors: Ivanova Tatyana , Gesheva Kostadinka , Hamelmann Frank
Published: September 2009

The paper presents the deposition of mixed molybdenum - chromium oxide films and characterization of their morphology, structure and the optoelectronic properties. The thin films are obtained by atmospheric pressure CVD technique at relatively low substrate temperatures. Raman and FTIR analyses are applied for structural transformation changes, induced by thermal treatments. Electron microscopy study reveals their morphology. Optical properties were characterized by UV-VIS spectroscopy. An improvement of films optical and electrochromic performance has been observed in comparison with the single Cr2O3 oxide films. The results are encouraging for successful preparation of good MoO3 - Cr2O3 electrochromic electrodes.
PECVD Deposition of nc-Si, μc-Si, and a-Si of Different Isotopic Composition in Form of Films and Bulk Material from SiF4 Precursor
Authors: Sennikov Petr , Golubev Sergey , Shashkin Vladimir , Pryakhin Dmitry , Andreev Boris , Drozdov Mikhail , Pohl Hans-Joachim
Published: September 2009

The results on production of films and bulk silicon samples of different isotopic composition by PECVD method are reported. The samples are investigated by the methods of X-ray diffraction, Raman scattering, secondary-ion mass spectrometry, IR spectroscopy. The photoluminescence spectra are measured at room temperature. Depending upon experiment the phase composition of samples is represented by nano-, micro-crystalline and amorphous silicon.
PEALD ZrO2 Films Deposition on TiN and Si Substrates
Authors: Monnier Denis , Gros-Jean Mickael , Deloffre Emilie , Doisneau Béatrice , Coindeau Stéphane , Crisci Alexandre , Roy Jérôme , Mi Yanyu , Detlefs Blanka , Zegenhagen Jorg , Wyon Christophe , Martinet Christine , Volpi Fabien , Blanquet Elisabeth
Published: September 2009

The substrate influence on the structure of 60nm-thick ZrO2 films deposited by Plasma Enhanced Atomic Layer Deposition (PEALD) is reported. Films were grown either on TiN/Si(100) or on Si(100) substrates. TiN layers (45nm thick) were PVD-deposited. High Resolution Transmission Electron Microscopy (HRTEM) micrographs show that ZrO2 films display a microstructure made of columnar grains with a diameter of 15-20 nm and extended throughout the whole film thickness. An interfacial layer between ZrO2 films and TiN substrates was detected by Synchrotron Radiation X-Ray Photoelectron Spectroscopy and HRTEM. According to thermodynamics simulations, this interfacial layer should be a ternary Zr-Ti-O compound.
Effect of H2 on the Microstructure and Properties of TiO2 Films Grown by Atmospheric Pressure MOCVD on Steel Substrates
Authors: Duminica Dan , Maury Francis , Hausbrand Rene
Published: September 2009

TiO2 thin films were deposited under atmospheric pressure by MOCVD in the range 400-600 {degree sign}C on various steel substrates under hydrogen ambiance. It is unusual to study the growth of functional oxide layers under H2 partial pressure, i.e. a reactive gas generally used as reductive atmosphere in CVD. Titanium tetra-iso-propoxide was used as single source precursor of Ti and O. The growth rate of TiO2 layers grown under nitrogen increases with the temperature and reaches a maximum in the range 500-550 {degree sign}C. At these temperatures the diffusion of substrate ions enhances the formation of rutile leading to a lower UV photocatalytic activity. Addition of H2 in the input gas phase during the deposition (i) reduces the formation of interface oxide layer, (ii) prevents the diffusion of cations from the steel substrate toward the TiO2 layer and (iii) favors the growth of anatase. This leads to an increase of photocatalytic efficiency under UV irradiation.
Correlation between Plasma OES and Properties of B-doped Diamond Films Grown by MW PE CVD
Authors: Belousov Maxim , Krivchenko Victor , Minakov Pavel , Pal Alexander , Rakhimov Alexander , Suetin Nikolay , Sen' Vasiliy
Published: September 2009

Boron doped polycrystalline diamond films were grown using MW PE CVD method. Optical emission spectra (OES) of MW-plasma in the region from 200 nm to 800 nm during boron doped polycrystalline diamond films growth were in situ investigated. Raman spectroscopy method was used for morphology investigation of grown polycrystalline diamond films. Also, absorption spectroscopy method was used for optical properties investigation of all grown films.
Online Control by IR Pyrometry of Nanostructured Multilayer CrCx/CrN Coatings Grown by MOCVD
Authors: Douard Aurelia , Samelor Diane , Delclos Sophie , Tendero Claire , Maury Francis
Published: September 2009

Online control of a deposition process is an important issue since it permits to check that everything is going well and it can contribute to elucidate the growth mechanism of the film. Results concerning real time analysis by IR pyrometry during CVD of nanostructured multilayer CrCx/CrN coatings are presented. The temporal variation of the emitted signal depends on the optical properties of the deposited material. In the case of CrCx coating, the emissivity behaves as for metal-like material: the resulting pyrometric signal changes sharply before stabilizing. With CrN, damped oscillations due to interferences resulting from multi reflection at interfaces are observed in the early stages. The signal recorded during deposition of CrCx/CrN multilayer coating is the combination between the two precedent phenomena: it perfectly follows the multilayer stacking as shown by comparison with TEM and SIMS profile analyses.
Preparation and Physical Characterization of SnO2:Sb
Authors: Haireche Sofiane , Boumeddiene A. , Guittoum A. , El Hdiy A. , Boufelfel Ahmed
Published: September 2009

We have used a fully controlled APCVD set up to prepare solid thin film samples of SnO2:Sb in different ratios. We used non destructive techniques to characterize our samples. X-ray diffraction was used to study the influence of Sb concentration on the lattice parameters and phase orientations. We have found that sample of concentration 4% showed a (200) preferred orientation. The chemical composition was determined with Rutherford Backscattering Spectroscopy (RBS) within an error of 1%. The AFM and SEM images showed that the surface roughness of our samples was very little influenced by the doping concentrations. An electrical surface resistance value of 8.0 Ohm/[] for a 3% concentration was the lowest versus oxygen and antimony variations. We found that the influence of oxygen on the metallic state is more important than the doping Sb.
Microstructural Control of Zirconium Carbide Coating Prepared by Chemical Vapor Deposition
Authors: Sun Wei , Xiong Xiang , Huang Baiyun , Li Guodong , Zhang Hongbo , Xiao Peng , Chen Zhaoke , Zheng Xianglin
Published: September 2009

To obtain Zirconium Carbide (ZrC) coating with columnar structure, which is optimal for resistance to heat shocks, chemical vapor deposition was used. Three series of multi-steps were carried to decrease the degree of supersaturation of active [C]: reducing concentration of C3H6, substituting C3H6 by lower-carbon-content hydrocarbons and the last increasing the flow rate of H2. Scanning electron microscopy show the morphology evolution of ZrC coatings from two-dimensional platelets, to fine grains, to polycrystals with different shapes and to columnar with domed tops. When the flow rate of H2 reach maximum (0.3m3/h), the columnar grains have a width of 1-2μm and a preferred orientation of (220). It is regarded as the change of limiting step of active [C] involving the reaction of formation of ZrC is the key factor for evolution.
In Situ Doped Si Selective Epitaxial Growth at Low Temperatures by Atmospheric Pressure Plasma CVD
Authors: Ohnishi Takayuki , Kirihata Yutaka , Ohmi Hiromasa , Kakiuchi Hiroaki , Yasutake Kiyoshi
Published: September 2009

We have investigated characteristics of in situ B-doped and selective Si epitaxial growth by atmospheric-pressure plasma chemical vapor deposition (AP-PCVD) at VHF frequency. Using B2H6 as a doping gas, defect-free in situ B-doped epitaxial Si films were grown by AP-PCVD at 570ºC. A high carrier concentration up to 1020 cm-3 was achieved at a high growth rate of 0.20 μm/min. The hole mobility of highly B doped Si films is the same as that of bulk Si single crystals, demonstrating that the electrical quality of AP-PCVD Si film is high enough for semiconductor device applications. Si selective epitaxial growth by AP-PCVD has also been studied using atomic hydrogen as etchant species. Highly selective epitaxial growth of Si with good film quality has been observed at 470ºC by increasing H2 gas concentration in the plasma.