bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical and Electrical Characterization of Fluorine Plasma Treated Hafnium Oxide Film for High Density Metal-Insulator-Metal Capacitors
Authors: Ding Shi-Jin , Huang Yu-Jian , Sun Qing-Qing , Zhang Wei
Published: September 2009

Influence of CF4 plasma-treatment (PT) on atomic-layer-deposited HfO2 dielectric has been investigated for high density metal-insulator-metal capacitor applications. X-ray photoelectron spectroscopy analyses reveal that the PT leads to incorporation of fluorine atoms into the HfO2 film by means of forming new chemical bonds of F-Hf-O near the surface. The resulting capacitance density increases up to 10.17fF/&mgrm2 with increasing the PT time to 10min, and the &agr decreases by 50ppm/V2 after the PTs. Further, the PT time of 5min results in a decrease by around one order of magnitude in the leakage current density at -3V, i.e., 3.5X10-8 A/cm2, compared to no PT. The above improvements can be attributed to F-passivation of oxygen vacancies at the interface of HfO2/Al as well as a slight increase in the surface roughness of HfO2 due to the PT.
Group-II Hafnate, Zirconate, and Tantalate High-k Dielectrics for MIM Applications: The Defect Issue
Authors: Dąbrowski Jarek , Dudek Piotr , Kozłowski Grzegorz , Lupina Grzegorz , Lippert Gunther , Schmidt Ronny , Walczyk Christian , Wenger Christian
Published: September 2009

We discuss the role of defects in metal oxides (mostly in strontium hafnate, barium hafnate and barium zirconate). The discussion is based on macroscopic and microscopic (C-AFM) electrical meas-urements, ab initio calculations for formation energies and elec-tronic structure of defects, numerical simulations of trap-assisted leakage, and on additional data provided by SIMS and X-ray tech-niques. We argue that moisture may be a hazardous contaminant.
Small Signal Response of Inversion Layers in High Mobility In0.53Ga0.47As MOSFETs Made with Thin High-k Dielectrics
Authors: Ali A , Madan H , Koveshnikov S , Datta Suman
Published: September 2009

Ultra-high mobility compound semiconductor-based MOSFETs and quantum-well FETs could enable the next generation of logic transistors operating at low supply voltages since these materials exhibit excellent electron transport properties. While the long channel In0.53Ga0.47As MOSFET characteristics exhibit promising characteristics with unpinned Fermi level at the InGaAs-dielectric interface, the high field channel mobility as well as sub-threshold characteristics needs further improvement. There could be contribution from one or several potential scattering processes to cause mobility degradation in surface channel In0.53Ga0.47As MOSFETs such as interface roughness, remote or local optical phonon scattering and remote Coulomb scattering due to charges in the gate oxide. In this work, we present a comprehensive equivalent circuit model that accurately models the experimental small signal response of inversion layers in In0.53Ga0.47As MOSFETs fabricated with LaAlO3 gate dielectric and enables accurate extraction of effective channel mobility. Temperature dependent measurements allow us to identity the various scattering mechanisms.
High-k Dielectrics for Ge, III-V and Graphene MOSFETs
Authors: Banerjee Sanjay K. , Tutuc Emanuel , Kim Seyoung , Akyol Tarik , Jamil M. , Shahredji Davood , Donnelly Joe , Colombo Luigi
Published: September 2009

It is well known that the existence of a high quality oxide on Si has been key to the success of Si metal oxide semiconductor field effect transistors (MOSFETs). Replacing SiO2 with high-k dielectrics in order to reduce gate tunneling currents has proven to be challenging, though it is now a manufacturable technique. Scaling of Si CMOS logic devices to the next level has led to a flurry of activity in enhanced channel mobility MOSFETs, using semiconductors from Column IV such as Ge and graphene, and III-V materials such as GaAs, InGaAs and InP. Since these materials lack a high-quality native oxide, integrating high-k gate dielectrics represents a marriage of necessity and convenience. It is known that atomic layer deposition (ALD) offers precise control over the uniformity and thickness of the deposited high-k films through a self-limiting reaction. Furthermore, ALD can potentially offer the advantage of reducing native oxides by appropriate engineering of the precursor chemistry. Nevertheless, integrating ALD high-k on Ge, graphene and III-V materials necessitates the use of an effective chemical surface treatment protocol. This is to alter the surface properties in order to ensure full surface coverage from the beginning of ALD runs, while preventing the re-oxidation.
Low Temperature Fabrication of AlN/Ge Structure Using Electron Cyclotron Resonance Plasma Nitridation
Authors: Kishiwada Jun , Mohamed Nurbaizura , Oniki Yusuke , Iwasaki Yoshitaka , Ueno Tomo
Published: September 2009

The structural and electronical properties of AlN/Ge(100) fabricated by Al-metal DC sputtering and ECR plasma nitridation were investigated. It was found that the dielectric constant of AlN was 8.9 in this fabrication method. Ge surface potential was controlled by gate voltage, and sharper curve of capacitancevoltage characteristics was obtained by using AlN as the insulator. However, the AlN/Ge structure shows a positive VFB shift which is a characteristic feature using Ge substrate. It was confirmed that the VFB shift occurred due to the effect of plasma irradiation at the interfacial Ge nitride layer.
Nature of Interface Traps in Si/SiO2/HfO2 /TiN Gate Stacks and its Correlation with the Flat-band Voltage Roll-off
Authors: Kar S.
Published: September 2009

We have carried out a detailed experimental investigation of the trap parameters - trap energy, trap density, and hole capture cross-section - in a large number of p-Si/SiO2/HfO2/TaN MOS capacitors fabricated on wafers with graded SiO2 layer, and of the flat-band voltage, using a newly developed admittance spectroscopy technique, which yields accurate values of the surface potential and the flat-band voltage, and makes use of the measured conductance to obtain accurate values of the trap parameters. The correlation between the trap density and the flat-band voltage has been analyzed.
Electrochemical Reactions in Nanoionics - Towards Future Resistive Switching Memories
Authors: Waser Rainer , Valov Ilia
Published: September 2009

Resistive switching random access memory (RRAM) based on electrochemically driven ON/OFF state transitions in metal-solid electrolyte-metal cells appears as an alternative to currently used concepts and materials for RAM i.e. DRAM and Flash. Low power consumption, scalability down to sub 10 nm scales, reliable operation, and long term stability (non volatile) are the key advantages of RRAM. Based on the type of switching mechanism we suggest appropriate classification - VCM for valence change memory and ECM for electrochemical metallization memory. In all three types a switch between a non-conductive and a conductive state affords their application in RAM devices. An electrochemical reaction of growth/rupture of a nanoscale filament, short circuiting/disconnecting the cell is believed to be responsible for the transition between both states in VCM and ECM systems.
MOCVD of Complex Oxide Systems: From Precursor Chemistry to Applications
Authors: Malandrino Graziella , Toro Roberta G. , Lo Nigro Raffaella , Fragalà Ignazio L.
Published: September 2009

Metal complexes bearing linked beta-diketonates and ancillary Lewis ligands have found wide interest as precursors. The relationships involving molecular architectures and mass transport properties of alkaline-, rare-earth and transition metal precursors are discussed. The effects due to the nature of the β-diketonate moiety as well as of the ancillary ligand on mentioned properties have been addressed. The perspectives of applications to MOCVD processes of complex oxide systems are commented, reporting on the in-situ growth of the La1-xSrxMnO3 phase, as a case study. Application of a transition metal precursor to the deposition of NiO films is commented as well.
Mechanism-Based Design of Precursors for MOCVD
Authors: McElwee-White Lisa , Koller Jürgen , Kim Dojun , Anderson Timothy J.
Published: September 2009

A chemistry-based approach to designing precursors for the deposition of inorganic films requires consideration of the physical properties of the precursor compound (e.g., volatility for transport in the reactor) and its probable decomposition pathways, both in the gas phase and on the surface during growth. We have been using Aerosol-Assisted Chemical Vapor Deposition of tungsten carbonitride (WNxCy) films from tungsten imido complexes and tungsten hydrazido complexes as a model system to investigate the relationship between data obtained from conventional organometallic mechanistic study of the precursors and the resulting film deposition kinetics and film properties. Among the typical techniques for the elucidation of decomposition pathways in organometallic compounds that will be discussed in this context are NMR kinetics, mass spectrometry, DFT calculations, and single crystal X-ray diffractometry.
Photoluminescence Properties of Polar and Non-polar ZnO Films Grown by Atmospheric-pressure CVD Using Zn and H2O as Source Materials
Authors: Terasako Tomoaki , Taniguchi Kouta , Taira Keisuke , Yagi Masakazu , Shirakata Sho
Published: September 2009

Photoluminescence spectra of polar ZnO/c-Al2O3 and non-polar ZnO/r-Al2O3 films grown by the atmospheric-pressure CVD using Zn and H2O as source materials have been investigated. For the non-polar films, the I0, I1 and I2 lines on the high energy side of exciton-region were relatively strong. For the polar films, however, these emission lines were very weak. Moreover, several non-polar films exhibited the C-exciton emission. These differences between the polar and non-polar films are probably due to the difference in polarization selectivity resulting from the difference in growth direction. For both the polar and non-polar films, the I4 line attributed to the exciton bound to the H related donor increased with source supply ratio of H2O to Zn. For the non-polar films, the I6, I8 and I9 lines attributed to the group III elements became weaker with increasing Zn source temperature suggesting the possibility of impurity doping under stoichiometry control.
Atmospheric Pressure Chemical Vapour Deposition of Electrochromic Mo-W Oxide Films: Structure and Optoelectronic Properties
Authors: Ivanova Tatyana , Gesheva Kostadinka , Lebedev Oleg , Kalitzova Maria , Bojadjiev Stefan
Published: September 2009

The study deals with the technology and investigation of structure and the optoelectronic properties of tungsten and molybdenum based oxide films showing high electrochromic (EC) performance. MoO3-WO3 films are deposited by atmospheric pressure CVD technique, using pyrolytic decomposition of W and Mo hexacarbonyls mixture in Ar/O2 atmosphere. The high resolution TEM studies showed columnar structure. The grain boundaries this way serve as suitable spaces for ions intercalation. Field Emission SEM was used to study the morphology of obtained mixed oxide films. Optical properties were characterized by UV-VIS Spectroscopy. The excellent colour efficiency and optical modulation of these transition metal oxide films proved for their serving as successful functional layers in electrochromic devices.
AFM Study of PECVD DLC Films for Solar Selective Absorber
Authors: Tinchev Savcho , Gusterov Aleksander , Sharlandzhiev Peter , Nikolova Petranka , Dyulgerska Yuliana
Published: September 2009

Recently we proposed and fabricated solar selective absorber made exclusively from diamond-like carbon films. This absorber consists of five DLC sublayers deposited by PECVD. The necessary variations of the optical parameters of the films were made only by changing the deposition conditions (different bias voltages) of hydrogenated amorphous carbon films. In an absorber beside the optical parameters it is also important the structure and morphology of the absorber surface. We report here the results of AFM (atomic force microscope) studies of the single films and of the whole absorber. Because the surface of the DLC films was found to be very smooth, the whole absorber was deposited on rough aluminum substrate. In the visible range, reflection below 10 % was achieved with minimum of 3.7 % at 780 nm.
Pulsed Spray Evaporation CVD of Functional Complex Oxides: Interplay between the Structure, Electrical Properties and Surface Reactivity
Authors: Bahlawane Naoufal , Tchoua Ngamou Patrick Herve , Kohse-Höinghaus Katharina
Published: September 2009

The growth of pure phase of a number of perovskites and spinels is reported using pulsed spray evaporation (PSE) CVD. Beside the near bulk properties of 250 nm-thick perovskites an unusual confinement of the charge transport was observed in ultrathin, < 10 nm, polycrystalline LaCoO3 films resulting in an apparent electrical conductivity that is higher than that of single crystal. In the second part of this report, a doping strategy was used as tool to tune the properties of the spinel structure of cobalt oxide, enabling the establishment of direct correlations between its properties and catalytic activity. Iron doping of Co3O4 has enabled the control of the reducibility of the spinel with direct consequences on the catalytic oxidation of CO, and the control of the abundance of basic adsorption sites which affected the catalytic oxidation of ethanol.
Variation in Properties CVD−ZnSxSe1-x with Composition
Authors: Gavrishchuk Evgeny , Savin Dmitry V. , Ikonnikov Vladimir
Published: September 2009

The investigations of structural, optical, and mechanical properties with uniform composition of zinc sulfoselenides grown by CVD method were carried out. The extreme nature in dependence of the properties upon composition is connected with non-smooth change in the degree of structural defect while changing the ratio of the atoms of sulfur and selenium in solid solutions.
Barium Titanate Thin Film Growth by Low-pressure Metalorganic Chemical Vapor Deposition
Authors: Sekine Tetsuaki , Okumura Yu , Satou Akira , Akiyama Yasunobu
Published: September 2009

Barium titanate (BaTiO3) thin films were prepared from β-diketonate complexes as raw materials (on silicon substrates and into short quartz tubes) in the horizontal tubular hot-wall chemical vapor deposition reactor. The growth conditions, growth rate, and types of films grown were investigated. At high temperature (973 K), BaTiO3 could be prepared at concentrations equal to each of the metalorganic complexes, and its growth rate could be explained by summing the simple oxide growth rates because the growth rate of BaTiO3 is controlled by the mass transfer rate of the precursor. However, at low temperature (773 K), BaTiO3 could grow at a concentration of the Ti source that was richer than that of the Ba source because the growth rate of BaTiO3 is controlled by the rate of the chemical reaction and the Ti source reacts slower than the Ba source.
Chemical Vapour Deposition of Metastable Ni3N
Authors: Lindahl Erik , Ottosson Mikael , Carlsson Jan-Otto
Published: September 2009

Metastable nickel nitride (Ni3N) has been chemically vapour deposited by the use of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)Ni(II) (Ni(thd)2) and ammonia precursors. The growth on both non-etched Si(100) and amorphous SiO2 is polycrystalline at deposition temperatures between 200-290{degree sign}C. However, at the highest temperatures the impurity level of oxygen and carbon originating from the metal precursor ligand, is about 5%. The growth rate dependence of temperature is divided into three different regions with large differences in activation energies, interpreted as different factors controlling the growth. In addition the deposition rate as a function of precursor supply as well as the incubation time for the growth initiation are different at temperatures which are further indications of differences in reaction mechanism. By substitution of NH3 for H2 to the reactant gas the growth mechanism is shown to occur via surface -NHx groups.
In-Situ Investigation of the Processes of Precursor Adsorption by Means of Ellipsometry and Mass Spectrometry
Authors: Igumenov Igor K. , Prozorov Pavel , Semyannikov Pyotr P. , Zhukova Irina N.
Published: September 2009

The processes of palladium bis-trifluoroacetonate physical adsorption are investigated by means of ellipsometry and mass spectrometry in situ. Using the specially developed MO CVD reactor with the ellipsometric control of optical parameters, we carried out investigation of the kinetics of adsorption of palladium complex on silicon, quartz, and copper. On the basis of the measured experimental dependencies, we calculated the lifetimes of the complex molecules on the surfaces of silicon, quartz, and copper at room temperature. The temperature dependence of the lifetime of complex molecules on the surface of silicon was obtained. A special attachment with the mass spectrometric indication of the gas phase was used to carry out experiments aimed at the investigation of the kinetics of physical adsorption of bis-hexafluororacetylacetonate- palladium complex on quartz and copper surfaces. Temperature dependencies of the lifetimes of molecules adsorbed on quartz and copper surfaces were obtained.
Texture and Residual Stress Analysis by XRD on Metastable Tetragonal Zirconia Films Obtained by MOCVD
Authors: Jouili Mohamed , Andrieux Michel , Gallet Isabelle , Prud'Homme Nathalie , Ji Vincent
Published: September 2009

Zirconia films were deposited by MOCVD using Zr2(OiPr)6(thd)2 on silicon substrate under different pressures. They were characterized for crystalline structure, crystallite size (~5-6 nm) by Grazing incidence X-ray diffraction and by FEG-SEM for microstructure and morphology. GIXRD patterns showed the predominance of the tetragonal phase (or cubic). The intensities ratio of the diffraction peaks between (111)t-c and (200)t c lattice planes increased with the pressure and, consequently, with the film thickness. The films morphology, as well as the stress levels in such ZrO2 films were different as a function of their thickness: compressive growth stress in the thinner layers and tensile growth stress for the thick one. A high peak intensity was observed at the center of the {200} pole figures showing that the majority of the surfaces plane were parallel to (100) plane.
Predictable Simple Reaction Model for Poly-Silicon LPCVD Process
Authors: Kaneko Kimihisa , Ogino Masaaki , Shimizu Ryosuke , Shimogaki Yukihiro , Koshi Mitsuo
Published: September 2009

Poly-silicon deposition rate profiles on silicon wafers in several temperatures around 873 K along axial direction in commercial low-pressure chemical vapor deposition (LPCVD) reactor were investigated by both experiments and numerical simulations considering coupled computational fluid dynamics (CFD) and chemical reactions. While the chemical reaction processes of poly-silicon film deposition is a complicated system with a huge number of elementary reactions, we could successfully simulate the experimental results with a simplified 2-step surface reaction model of SiH4. Simulated film deposition rate profiles along the axial direction of reactor were in good agreement with experimental results, and the 2-step reaction model was proved to be a good tool for the numerical simulation of poly-silicon deposition process in commercial reactor.
MOCVD of Epitaxial Alkali-Earth Fluorides Thin Films
Authors: Blednov Andrey V. , Gorbenko Oleg , Samoilenkov Sergej , Muydinov Ruslan , Kaul Andrey
Published: September 2009

Thin films of alkali-earth fluorides and multilayer structures including such layers are known as perspective materials for optics, photonics and chemical sensors. They can also be considered as a material for buffer layers for 2G HTSC wires. Here we report on growing epitaxial CaF2 and SrF2 films on different substrates by MOCVD. The films' properties were examined using RBS, SEM, EDX, XRD, EBSD and AFM. The obtained films revealed perfect in- and out-of-plane orientation and had a smooth, crack-free surface. Depending on the substrate and deposition conditions, some films required the recrystallization annealing to form the epitaxial layer or that of good texture. Additionally, a number of multilayer films including MF2 layers were grown. The obtained films were successfully used as substrates for HTS deposition.
Rapid Thermal (RT) MOCVD of Undoped and Al Doped ZnO Thin Films
Authors: Nebatti Abdelkader E. , Pflitsch Christian , Eckert Christopher , Atakan Burak
Published: September 2009

Undoped and aluminum doped zinc oxide thin films were deposited on Si (100) and borosilicate glass substrates by using a novel RT-MOCVD technique, which is based on the use of the thermal radiation of tungsten lamps for substrate heating. The films were deposited from the acetylacetonates of zinc and aluminum which were used as precursors in the presence of oxygen. As result, well ordered and homogeneous ZnO films were grown. The undoped films show a preferred orientation on both substrates while the grains of the polycrystalline aluminum doped films are randomly ordered. Additionally whisker growth was observed for the doped films. As confirmed by EDX analysis, the amount of aluminum dopant was precisely controlled by varying the flows of transport gas through the evaporators. Finally, it was found that all deposited films are optically transparent, with transmittance ratios between 65% and 85% in the visible range.
2D Species Concentration Mapping of Thermal AP-CVD Reactors for Monitoring, Control and Design
Authors: Sawtell David , Kasiutsich Vasili , Holdsworth Robert , Sheel David W. , Martin Philip A.
Published: September 2009

This paper describes progress towards the two-dimensional mapping of chemical species in an atmospheric pressure chemical vapour deposition (AP-CVD) reactor during the deposition process. The approach uses tunable infrared laser absorption spectroscopy to measure line-of-sight optical absorbance data for specific chemical species. 2D distributions can then be obtained by tomographic inversion techniques. The developed techniques will have advantages for monitoring, control and design of reactors.
Reaction Kinetics of GaN Metal-Organic Vapor-Phase Epitaxy Analyzed by Multi-Scale Profiles of Growth Rate
Authors: Sugiyama Masakazu , Yasukochi Satoshi , Shioda Tomonari , Shimogaki Yukihiro , Nakano Yoshiaki
Published: September 2009

The growth mechanism and rate constants of GaN metal-organic vapor-phase epitaxy (MOVPE) have been unclear in spite of the necessity for large-scale production of this material. In this work, the major precursor of GaN has been deduced and its surface reaction rate constant has been obtained through the analysis of multi-scale growth-rate profiles both in the reactor-scale and in the micrometer-scale profiles that were obtained by selective-area growth. Usually, it is difficult to explore surface reaction kinetics, especially for the MOVPE of GaN, because of mass-transfer-limited kinetics. This multi-scale analysis, however, has clarified that a single precursor, the gas-phase reaction product between (CH3)3Ga and NH3, leads to the growth of GaN with a surface reaction probability of approximately 0.4 at 1400 K which is a typical growth temperature. A lumped reaction model of GaN MOVPE was proposed that led to reasonable agreement between the simulated growth-rate profile in the reactor-scale and the corresponding measured profile.
Low-temperature MOCVD of Epitaxial CaF2 and SrF2 Films
Authors: Makarevich Artyom M. , Shсhukin Alexandr , Markelov Anton , Samoilenkov Sergej , Semyannikov Pyotr P. , Kuzmina Natalia P.
Published: September 2009

The deposition of epitaxial CaF2 and SrF2 thin films on (00l)SrTiO3 substrates and textured Ni-W-alloy tapes by low-temperature water assisted MOCVD was studied. Complexes Ca(hfa)2(diglyme)(H2O) and Sr(hfa)2(tetraglyme) (Hhfa = 1,1,1,5,5,5-hexafluoroacetylacetone, diglyme = 1-methoxy-2-(2-methoxyethoxy)ethane, tetraglyme = 2,5,8,11,14-pentaoxapentadecane)) were used as single-source precursors. It was observed that the water presence increased the deposition rate and reduced the activation energy of film deposition process at temperature below 500oC. To estimate a role of water in thermal decomposition of Ca(hfa)2(diglyme) vapor on a heated surface, high temperature mass spectrometry in a vacuum was used. The quality of films was analyzed with XRD, AFM, SEM and EBSD methods. The results obtained may be useful for technology development of high temperature superconducting wires, optical and microelectronic devices.
Crystallization Process of Amorphous Silicon Utilizing A Radio Frequency Thermal Plasma Torch
Authors: Ota Naoki , Haruta Koji , Shimizu Hirokazu , Kobayashi Tomohiro , Shirai Hajime
Published: September 2009

The crystallization mechanism of hydrogenated amorphous silicon (a-Si:H)has been studied through the real time monitoring of the surface temeparture, transmittance and reflectance (T/R) profiles during the plasma annealing utilizing an rf thermal plasma torch. The correlation among the surface temperature profile, T/R, and film fine structure is discussed. The film crystallization proceeds through the solid phase crystallization followed with the grain growth due to the coalescence of small crystalline grains.
Deposition of WNxCy from the Tungsten Piperidylhydrazido Complex Cl4(CH3CN)W(N-pip) as a Single-source Precursor
Authors: Kim Dojun , Kim Oh Hyun , Ajmera Hiral , Anderson Timothy J. , Koller Jürgen , McElwee-White Lisa
Published: September 2009

The tungsten piperidylhydrazido complex Cl4(CH3CN)W(N-pip) (1) was used as a single-source precursor for growth of tungsten carbonitride (WNxCy) by metal-organic chemical vapor deposition (CVD) in H2 carrier. Multiple spectroscopic techniques were used for preliminary evaluation of the suitability of 1 as a precursor and to suggest possible fragmentation pathways. The effect of growth temperature on film microstructure, lattice parameter, average grain size, chemical composition, chemical bonding states, growth rate, film resistivity, and sheet resistance was studied.
Thermal Properties of Some Volatile Titanium (IV) Precursors
Authors: Filatov Egor S. , Nizard Harry , Semyannikov Pyotr P. , Sysoev Sergey V. , Trubin Sergey V. , Morozova Natalia B. , Zherikova Kseniya V. , Gelfond Nikolay V.
Published: September 2009

The thermal properties of some titanium precursors such as titanium (IV) isopropoxide (Ti[OPri]4 = TTIP); titanium(IV) ethoxide (Ti[OEt]4); titanium tetradimethylaminopropanol (Ti[DMAP]4) have been investigated by complex thermal analysis (thermogravimetric analysis etc.), mass-spectrometry, tensimetric methods (static and flow methods). The temperature dependences of saturated vapour pressure of titanium precursors have been obtained in a wide range of temperatures and thermodynamic parameters of vaporization processes have been calculated. Thermal decomposition of TTIP vapor has been investigated by high temperature mass spectrometry; temperature range and gaseous by-products were determined.
On gaseous phase of ALD precursors by means of thermodynamics
Authors: Violet Perrine , Nuta Ioana , Chatillon Christian , Blanquet Elisabeth
Published: September 2009

The thermal stability of the pentakis(dimethylamino) tantalum (PDMAT) precursor used in the Atomic Layer Deposition (ALD) TaN process has been studied from 343 to 723 K using a specific reactor coupled with a Knudsen cell mass spectrometer. This reactor is built as tandem cells: an evaporation cell and a cracking cell. This reactor tries to simulate the conditions found in the bubbler of the ALD system by the evaporation cell and in the hot reaction zone of ALD by the cracking cell. Experiments showed that the saturated gaseous phase (originated from PDMAT evaporation) is composed of Ta(N(CH3)2)4(g), and in smaller amounts of Ta(N(CH3)2)5(g) and OTaN4C8H24(g). Cracking experiments, performed at different temperatures, showed that PDMAT is a minor component of the gaseous phase, meanwhile Ta(N(CH3)2)4(g), and HN(CH3)2(g), are the major gaseous species that decompose at higher temperatures. Oxygen containing molecules are also observed in all temperature range.
Dimethylgallium Isopropoxide as a New Volatile Source for ALD and MOCVD of Ga2O3
Authors: Lee Heeju , Kim Kunhee , Woo Jeong-Jun , Jun Doo-Jin , Park Youngsoo , Kim Yunsoo , Lee Hong Won , Cho Yong Jai , Cho Hyun Mo
Published: September 2009

Dimethylgallium isopropoxide, Me2GaOiPr, is a gallium analogue of the volatile aluminum source dimethylaluminum isopropoxide, Me2AlOiPr, which was recently commercialized as a precursor for Al2O3. It is a liquid at room temperature and has a reasonably high vapor pressure, high enough for atomic layer deposition and/or metal organic chemical vapor deposition. We employed this precursor in the atomic layer deposition (ALD) and metalorganic chemical vapor deposition (MOCVD) of Ga2O3 thin films. Our ALD process, in which water was used as the oxygen source, showed an apparent ALD temperature window between 300 and 325ºC with a growth rate of ~1.5 Aå/cycle. The MOCVD was performed in the temperature range 450-625ºC with oxygen as the reacting gas. The Ga2O3 films deposited in both processes were found to be stoichiometric and amorphous.
Novel Precursors for the MOCVD of Molybdenum Nitride
Authors: Thiede Tobias , Gwildies Vanessa , Alsamann Louay , Rische Daniel , Fischer Roland
Published: September 2009

Tungsten nitride and molybdenum nitride are electrically conducting refractory metal nitrides. Their applicability as novel gate electrode materials in CMOS technology is actually under investigation. MOCVD is one of the most prominent processes to deposit thin films of these materials. In order to improve the quality of MOCVD grown thin films it is important to optimize the chemical design of the employed precursors. Herein, we report on the synthesis of different imido-guanidinato-molybdenum complexes like [Mo(NtBu)2(X){(iPrN)2CNMe2}], (X = Cl, I, or N3). In particular we want to highlight that we were able to synthesize the new all nitrogen coordinated imido-amidinato-molybdenum complex [Mo(NtBu)2{(iPrN)2CMe}2]. The chemical and thermal properties of these new molybdenum compounds were investigated, to check their potential use as precursors for the MOCVD of molybdenum nitride.
Alkylsilyl Compounds of Selenium and Tellurium: New Precursors for ALD
Authors: Hatanpää Timo , Pore Viljami , Ritala Mikko , Leskelä Markku
Published: September 2009

Several alkylsilyl compounds of selenium and tellurium were synthesized and characterized. Crystal structures of (tBuMe2Si)2Se and (tBuMe2Si)2Te were solved. Thermal properties of the compounds were studied with TGA. It was found that these compounds are very volatile and thermally stable therefore suitable ALD precursors. Reactivity of the compounds was preliminarily studied by mixing the compounds with different metal precursors in solution. It was found that the compounds are highly reactive against many metal halides and other metal compounds. They have also been tested successfully in ALD. For Ge2Sb2Te5 low growth temperature (60-90 oC) was found the most suitable while ZnSe and ZnTe films were grown at 400 {degree sign}C.
MOCVD Of Gallium Oxide Thin Films Using Homoleptic Gallium Complexes: Precursor Evaluation and Thin Film Characterisation
Authors: Hellwig Malte , Xu Ke , Barreca Davide , Gasparotto Alberto , Niermann Benedikt , Winter Jörg , Becker Hans-Werner , Rogalla Detlev , Fischer Roland , Devi Anjana
Published: September 2009

This work is focused on the evaluation of different Ga(III) precursor (conventional acetylacetonates, malonates and amides) for the MOCVD of Ga2O3 thin films. In particular, the attention is devoted to a thorough comparison of the precursor qualifying properties (volatility, thermal stability under the vaporization conditions) and their interrelations with the features of the obtained deposits. Samples were grown by thermal CVD and characterized by means of a multi-technique approach (X-ray diffraction {XRD}, scanning electron microscopy {SEM}, atomic force microscopy {AFM}, energy dispersive X-ray spectroscopy {EDXS}, X-ray photoelectron spectroscopy {XPS}, Rutherford backscattering spectrometry {RBS}, spectroscopic ellipsometry {SE}) to elucidate their microstructure, morphology and chemical composition, as well as their mutual interrelations with the synthesis conditions.
Tuning the Thermal Properties of Hafnium Precursors by Tailoring the Ligands
Authors: Xu Ke , Milanov Andrian P. , Devi Anjana
Published: September 2009

The volatility and thermal stability of a series of hafnium complexes with guanidinates and amidinate ligand systems have been investigated. In particular thermogravimetric analysis which also includes isothermal studies were carried out to measure the temperature onset of volatilization, temperature range of decomposition and sublimation or evaporation rate of the precursors at different temperatures. The thermal stability of the hafnium compounds was investigated by carrying out NMR studies at fixed temperatures over prolonged time period to check for any degradation of the precursor. In addition, the half life of the compounds was also determined. Among all the Hf compounds investigated in this study, the mixed bis-amide-bis-guanidinate compound of hafnium (compound 4) displays very promising thermal characteristics in terms of volatility, clean vaporization as well as shows enhanced thermal stability at temperatures as high as the evaporation and deposition temperatures during an ALD process compared to the parent hafnium alkylamides.
Tungsten Coatings as a Protective Layer on Surfaces in Contact with Molten Metals
Authors: Cosemans Patrick , Lauwerens Walter , Mampaey Frans
Published: September 2009

Hot wall low temperature (500{degree sign}C) Chemical Vapour Deposition (CVD) is used to coat steel surfaces with a W or WC coating to protect the steel substrate against the attack of molten metals. Wettability measurements show that the W coating is almost not wetted by Zn, indicating excellent barrier properties against corrosion and soldering. It was also found that surface roughness influences the thermal barrier properties of the W(C) coating which can be beneficial to minimize heat checking.
Controlled Synthesis of Carbon Nanotubes by Various CVD and PECVD Methods
Authors: Ionescu M. I. , Liu H. , Zhong Y. , Zhang Y. , Li R. , Sun X. , Kpetsu J.-B. , Côté C. , Jedrzejowsk P. , Sarkissian Andranik , Merel P. , Laou P. , Paradis S. , Désilets S.
Published: September 2009

In this paper, we review and present the results of carbon nanotubes syntheses using variety of CVD and PECVD techniques that are available in our laboratories. The techniques included Joule-heating CVD, floating catalyst CVD, conventional thermal CVD, aerosol-assisted CVD, spray pyrolysis CVD, radio frequency plasma enhanced CVD (PECVD) and microwave plasma enhanced CVD. Influences of synthesis methods on the CNTs growth have been compared and discussed. The synthesized CNTs have been characterized by various techniques, including Raman Spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These studies are expected to pave the way to develop strategies for controlled synthesis of CNTs tailored for specific applications, including sensors and nanodevices.
Optimization of Solar Cell Performance using Atmospheric Pressure Chemical Vapour Deposition deposited TCOs
Authors: Yates Heather M. , Evans Philip , Sheel David W. , Hodgkinson John L. , Sheel Paul , Dagkaldiran Umit , Gordijn Aad , Finger Friedhelm , Remes Zdenek , Vanecek Milan
Published: September 2009

Photovoltaic cell performance can be greatly improved by optimising the transparent conducting oxide used as the front contact. We have developed an advanced atmospheric pressure chemical vapour deposition (APCVD) process, by applying fast experimentation and using a combinatorial chemistry approach to aid the studies. By use of this process, F-doped SnO2 has been deposited using either monobutyl tin trichloride or tin tetrachloride with aqueous HF or trifluoro-acetic acid as the dopant source. The deposited films were characterised for crystallinity, morphology, resistivity and growth rate to aid optimisation of material suitable for solar cells. The results from use of the different tin precursors and dopants were compared. The most striking changes were related to resistivity and surface morphology. Compared with commercially available TCO CVD coated glasses, our coatings show excellent performance resulting in a high quantum efficiency yield for a-Si:H solar cells.
Comparative Study of SiNx and BNx Nanolayers Prepared by Different Chemical Vapor Deposition Methods
Authors: Beshkov Georgi , Nedev Nikola , Spassov Dencho , Terrazas Juan , Salas Benjamin V. , Krastev Veselin
Published: September 2009

In this work IR and EDX spectra, SEM micrographs as well as etching rates of silicon nitride films deposited by different Chemical Vapor Deposition (CVD) processes are presented. SiNx layers were obtained by Atmospheric Pressure CVD (APCVD), Low Pressure CVD (LPCVD), Micro Pressure CVD (μPCVD) and Plasma Enhanced CVD (PECVD). BNx films fabricated by Rapid Thermal Process (RTP) are also studied. The nitride films were deposited under optimal technological conditions for each type of industrial reactor system. The positions of the IR peaks and nitrogen concentration of investigated in this work dielectric films depend on performed method of deposition. A correlation between the nitrogen concentration and the etching rate was found. BNx layers with ratio B/N close to stoichiometric (0.75) were obtained at 1400o C for 180 s.
Resistive Switching in Metal Oxide Films Deposited by Metalorganic Chemical Vapor Deposition
Authors: Nakamura Toshihiro , Onogi Keita , Homma Kohei , Tachibana Kunihide
Published: September 2009

Pr1-xCaxMnO3 (PCMO) films were deposited by metalorganic chemical vapor deposition using in situ infrared spectroscopic monitoring. The I-V characteristics were investigated in the PCMO-based devices exhibiting electrical-pulse-induced resistive switching. The frequency response analysis suggested that the resistance switching in the PCMO-based devices was mainly due to the resistance change in the interface between the film and the electrode.
Pulse CVD Deposition of Ru Films from Ru(II) ή3-Allylic Complex
Authors: Trubin Sergey V. , Morozova Natalia B. , Semyannikov Pyotr P. , Bessonov Alexandr , Gelfond Nikolay V. , Igumenov Igor K.
Published: September 2009

A ruthenium(II) ή3-allylic complex Ru(nbd)(allyl)2 (nbd = norbornadiene) was used as precursor for pulse CVD thin Ru films on silicon substrates. Preliminary study of thermal behavior of precursor was carried out: temperature dependence of vapor pressure was measured by means of Knudsen method with mass spectrometric analysis of gas phase composition; thermodynamic parameters of sublimation process were calculated. By means of high temperature mass spectrometry in situ the process of vapor thermo destruction was investigated in vacuum: vapor decomposition starts at relatively low temperature (about 180оC); the major gas by-products are the radicals of ligands - allyl, norbornadiene and their combinations. Deposition of Ru films was carried out in vacuum and hydrogen. XPS, AFM and HREM study have shown metal state of Ru in films. In the presence of hydrogen the film consists of Ru particles with size of 3.5 nm. Sample surface is smooth; mean square roughness is 0.17 nm.
The Synthesis of Tantalum (V) Oxide Using Atmospheric Pressure Chemical Vapour Deposition for the Purposes of Photo-activated Water Splitting
Authors: Hyett Geoffrey , Darr Jawwad , Mills Andrew , Parkin Ivan
Published: September 2009

This paper reports upon the deposition of tantalum (V) oxide thin films using dual source atmospheric pressure chemical vapour deposition. A range of precursors were used; Ta (V) chloride and tantalum (V) ethoxide as metal sources with water, ethanol and methanol, as oxygen sources. Optimum conditions were found in the reaction of tantalum (V) ethoxide and water, where a maximum growth rate of 553 nm min-1 was observed at 600ºC. Film depositions were carried out onto glass and metal coupons. The films on metal were tested for their ability to photo-oxidise water with a sacrificial electron acceptor under 254 nm light.
Synthesis of ZnS Nanoparticles by Spray Pyrolysis: Morphology Control Using the Same Precursors in Different Reactor Systems
Authors: Liu Sha , Swihart M. T.
Published: September 2009

Nanoparticles of zinc sulfide, a II-VI semiconductor with a band gap in the near UV region, have potential applications in solar cells, displays, photocatalysis, bioimaging, and other fields. We have prepared ZnS nanoparticles through spray pyrolysis using zinc acetate and thiourea as precursors. For these same precursors, we used different reaction systems to produce nanoparticles with different size and properties. In one system, the precursors were premixed and heated together in a single reaction line. The particles produced in this system ranged from tens to hundreds of nanometers in diameter, and in most cases they were hollow or porous. In the other system, two separate atomizers and reaction lines have been used for the two precursors. Therefore, the two precursors were evaporated and heated in different lines and were mixed as vapors. Smaller (below 20 nm diameter), dense particles of irregular geometry were obtained in this system. Moreover, in this second system, ZnO, ZnS, and intermediate composition particles can be produced.
Exploring Multiple Precursors in Pulsed Pressure-MOCVD
Authors: Clearwater Deborah , Hartshorn Richard M. , Krumdieck Susan
Published: September 2009

Pulsed pressure-MOCVD (PP-MOCVD) is a new technique that is less dependent on the volatility of precursors than MOCVD because precursors are introduced into the reaction chamber as an aerosol rather than by sublimation. It also allows more than one precursor to be employed. We have explored use of methanolic solutions of calcium lactate and trimethylphosphate as a PP-MOCVD precursor system for hydroxyapatite films. TGA experiments have been used to follow reactions of the precursors at high temperatures and a range of techniques (FTIR, SEM, EDS) have been used to characterise the materials that result from the TGA and deposition experiments.
Pulsed-Pressure MOCVD Processing Investigation for TiO2 Films on Si3N4 Substrate from TTIP
Authors: Siriwongrungson Vilailuck , Krumdieck Susan , Alkaisi Maan
Published: September 2009

The relationship between processing parameters and microstructures of as-deposited thin titanium dioxide (TiO2) on silicon nitride substrate was investigated for pulsed-pressure metalorganic chemical vapor deposition (PP-MOCVD). Titanium tetra-isopropoxide (TTIP) dissolved in toluene was the precursor. The processing parameters investigated were a range of base pressures from 50 to 200 Pa and relaxation time of 0, 2.5, 5 and 10 sec. The deposition temperature, precursor concentration and injection volume were kept constant at 450{degree sign}C, 0.015 M and 50 µl, respectively. The deposited films were analyzed using SEM, EDS, AFM, and XRD. The films have columnar growth anatase phase with the maximum growth rate of 3.0 nm/pulse. The grain sizes were between 59 and 236 nm and the maximum roughness was 5.75 nm. Growth rate and surface roughness was not affected by base pressure, but decreased with increased relaxation time. Grain size increased with base pressure and decreased with increased relaxation time.
Doped Iron Oxide Thin Films for Photoelectrochemical Generation of Hydrogen from Water
Authors: Sheel David W. , Lewis Joe , Robinson Alan , Yates Heather M.
Published: September 2009

Generation of hydrogen from solar irradiation has been identified as an attractive concept for many years and many studies have focused on photo-catalytic water splitting into H2 and O2 using semiconductor photo-catalysts. In this paper we report the deposition of Iron (III) oxide (Fe2O3) as the oxide semiconductor photo-catalyst. Fe2O3 is a low-cost semiconductor having high stability. We show that atmospheric pressure thermal CVD can achieve high growth rates and good control toward required material structures. Initial photo-response measurements are encouraging.
Tailoring of Optical Properties of Alumina films deposited by High Vacuum CVD (HV-CVD)
Authors: Multone Xavier , Afra Bamdad , Kuzminykh Yury , Hoffmann Patrik
Published: September 2009

The deposition of amorphous alumina (Al2O3) films on four inch wafers with high deposition rate (up to 50 nm/min) by an advanced HV-CVD technique is discussed. Amorphous nature of the films is confirmed by X-ray diffraction. Refractive index of the deposited alumina can be adjusted in the large range (1.3-1.62@633 nm) by varying the substrate temperate during the deposition. The films are highly transparent. The density and stoichiometry of the deposits are also influenced by deposition conditions. Presence of -OH groups is observed in some cases.
Thin Films of Tb(pobz)3 (Hpobz = 2-phenoxybenzoic acid): Reactive CVD and Optical Properties
Authors: Kotova Oxana , Utochnikova Valentina , Samoilenkov Sergej , Kuzmina Natalia P.
Published: September 2009

Thin films of aromatic terbium carboxylates are promising materials for application in different optical devices. However, thin films deposition of these compounds by common methods is almost impossible due to their low solubility in most common organic solvents and nonvolatility. In our previous work it was shown that thin films of one of the simplest aromatic terbium carboxylate Tb(bz)3 (Hbz - benzoic acid) can be obtained by the original approach based on the exchange reaction between volatile precursors - reactive CVD (RCVD). Herein we improved this approach and demonstrated its possibilities and advantages on deposition of thin films of new emissive material - Tb(pobz)3 (Hpobz - phenoxybenzoic acid). The bulk products and thin films of Tb(pobz)3, obtained by RCVD method were characterized by elemental analysis, IR-, Raman and photoluminescent spectroscopy as well as thin films were studied by AFM and SEM techniques.
Processing and Characterization of Nanocomposite Coatings using Aerosol-assisted Chemical Vapor Deposition (AACVD) Method
Authors: Hou Xianghui , Choy Kwang-Leong , Serín Virginie , Fleischer Niles
Published: September 2009

This paper presents the use of a variant of the CVD process called aerosol-assisted chemical vapor deposition (AACVD) for the fabrication of nanocomposite coatings. AACVD involves the generation and delivery of aerosol precursors to the deposition region. The flexibility of atomizing precursor solution or suspension in the AACVD process makes it possible for the incorporation of pre-formed nanoparticles in the precursor solution and to co-deposit the particles and matrix concurrently on the substrate surface to form the desired nanocomposite coatings. Our recent results have demonstrated that AACVD is a promising method for the synthesis of nanocomposite coatings with the incorporation of nanoparticles into ceramic matrices. The synthesis of inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles, as well as the processing and deposition mechanism of IF-WS2/Cr2O3 will be presented. The microstructure and properties of IF-WS2 and IF-WS2/Cr2O3 will also be highlighted.
Chemical Vapor Deposition of Silica Nanowires using Heteroleptic Bis(ethylmethylamino)silane Precursor
Authors: Kim Hyeong Joon , Park Sanghyun , Heo Jaeyeong
Published: September 2009

In the present study, silica nanowires were synthesized by employing inherent directionality of chemical vapor reaction between heteroleptic bis(ethylmethylamino)silane ((H2Si[N(C2H5)(CH3)]2) precursor and water without a metal catalyst at room temperature. The conceptual scheme used here is that the difference in the oxidation reactivities between Si-H and Si-N groups with water leads the formation of linear shaped products. The optimized pressure and temperature to obtain straight silica nanowires were 7 Torr and 25oC. The diameter and length of the silica nanowires were ~ 60-80 nm and ~ 1.9 µm, respectively. TEM revealed that nanowire is amorphous. FTIR, XPS, and EDX analyses indicated that the estimated composition was very close to SiO2.