ICMCTF2001 Session F4-1: Microstructural, Microanalytical and Imaging Characterization

Monday, April 30, 2001 1:30 PM in Room San Diego

Monday Afternoon

Start	Invited?	Item
1:30 PM	Invited	F4-1-1 In-Situ Observation of Pd Silicide Islands on Si Using UHV-TEM/STM M. Tanaka, M. Takeguchi, H. Yasuda, K. Furuya (National Research Institute for Metals, Japan) It is of great interest to investigate the formation of well-defined silicide phases and to characterize their properties for both technological and scientific sense. We have studied the Pd/Si (111) system with a newly developed UHV-TEM/STM integrated characterization system (UTSICS), which is a multi-chamber, UHV surface characterization and preparation system and is attached to an UHV-TEM and an UHV-STM. Samples were Si (111) and Si (011) prepared for TEM specimens that were treated in the UTSICS with 2kV Ar ions followed by resistive heating at 973-1273 K. Si (111)-7x7 superstructure was confirmed with both STM image and TED pattern. The Pd depositions were done from EB evaporators in deposition chamber at RT and in TEM column at 673 K. After observation, samples were annealed at 673 - 1273 K and studied with microscopes again. RT deposition did not show any TEM or STM images with ordered structure. Annealing of Pd deposited substrates to 573 - 673 K resulted in the formation of Pd2Si islands. When the Pd coverage was 8 ML, formation of (3x3) structure was observed on top of Pd2Si islands with STM. This structure coincides with Si (111) - (3root3x3root3) R30 structure. Annealing of this substrate at 1273 K resulted in the dissipation of most of the Pd islands and the formation of superstructure on terraces that is considered to be (2root3x2root3) structure. Deposition of Pd to TEM substrates at 673 K also resulted in the formation of Pd silicide islands. Structural analysis identified this layer to be Pd2Si. On the surface of the silicide layer, super structure with 3 times periodicity was found. EELS spectra obtained from the Si substrate and the top surface of silicide island showed Si L23 peak at the same energy level, while that of silicide island itself showed energy shift. STM height distribution and EELS analysis suggest that the silicide top structure is rather Si-rich and has sub-surface layer.
2:10 PM		F4-1-3 Characterization of Ge-Sb-Te Thin Films Deposited Using A Composition-Spread Approach S. Kyrsta, R. Cremer, D. Neuschütz (LTH, RWTH Aachen, Germany); M. Laurenzis, P. Haring Bolivar, H. Kurz (IHT II, RWTH Aachen, Germany) Ge-Sb-Te thin films for rewritable phase change optical data storage applications were deposited by magnetron sputtering using a composition-spread approach. The deposition took place in an UHV chamber by cosputtering of three magnetron cathodes equipped with pure Ge-, Sb- and Te-targets in a DC argon plasma. To investigate the influence of the chemical composition of the phase change material on its optical properties, films with lateral compositional gradients of up to 30 at.% were deposited. The composition, binding states and structure of the films were investigated by EPMA mappings, XPS, AES, RHEED and GIXRD on plain Si wafers, whereas the phase change velocity of Ge-Sb-Te was determined on polycarbonate-Al-SiO₂ stacks. The change between amorphous and crystalline phases of the films was induced and characterized with a static tester consisting of an optical microscope with an integrated high power laser diode. The change in reflectivity induced by the laser pulses was measured by a high sensitivity photo detector. Depending on the composition, the duration for the initial crystallization was determined between 220 and 500 ns, while the re-amorphization required between 20 and 120 ns. Structural analyses proved the existence of two crystalline phases with cubic and hexagonal structure in the initialized films.
2:30 PM		F4-1-4 Deposition of Thin Bioceramic Film on Biomedical Implant. M. Hamdi, A.M. Ektessabi (Kyoto University, Japan) Medical and dental implants are often coated with thin layer of calcium phosphate (CaP) bio-ceramics, especially hydroxyapatite (HAp), to improve their biological behavior. The coating of HAp, which is popularly used for dental and orthopaedic prosthesis, were prepared by using electron beam deposition (EBD) method. Electron beam was employed to evaporate stoichiometric HAp target. A constant deposition rate was monitored in-situ by a quartz thickness gauge. The coated samples were heat treated to obtain crystalline phase. The characteristics of the deposited layers were evaluated by x-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive x-ray (EDX) spectroscopy. Scanning scratch test was carried out to evaluate the adhesion strength of the coatings to the substrate. Comparisons with samples produced by ion beam assisted sputter deposition and simultaneous vapor deposition were also performed. XRD analysis revealed that the as-deposited film was amorphous and a HAp-type structure was obtained from the post-heat treatment of the deposited films. SEM observations showed that all the samples were relatively uniform with no occurrence of cracks after annealing. Ca/P ratios for the annealed samples were found to be slightly higher than the stoichiometry, suggesting the dissolution of phosphorus at higher temperature. Adhesion strength of the samples is comparable to other coatings produced by various methods.
2:50 PM	Invited	F4-1-5 Determination of the 3D-Distribution of Trace Elements in Coatings by SIMS H Hutter (Vienna University of Technology, Austria) The characterisation of thin layers is a challenge to physical analytics. Not only the composition of thin layers but also the spatial distribution of trace elements within the layer and at the interface between layer and material are decisive for their characteristics. The potential of physical analytics has constantly increased over the last years. Analysis methods have evolved from simply recording surface spectra to measuring complex distributions of elements even in lowest concentrations. The 3-D trace analysis with SIMS is currently one of the most powerful analytical tools available. Laterally resolved secondary ion signals are measured during sputter removal of the material, thus yielding signals with n chemical and three spatial dimensions. Imaging SIMS is capable of producing two and three-dimensional spatially resolved information of the element distribution of a significant and therefore representative volume (150 x 150 x 20 Âµm3) in a relatively short time (1 hour). The lateral resolution is about 1 Âµm, the depth resolution about 20 nm. One of the most important advantages of SIMS is the ability to detect all elements which is of great value, also in the higher concentration ranges. It is demonstrated by measurements of the boron distribution in CVD-diamond films. The bulk concentration of B is about 5 % (measured by EPMA). Single diamond crystals have a content of B below 1% according to the EPMA results. 3D-SIMS gives the quantitative distribution of B also in these low concentration areas. Beyond this SIMS also provides the distribution of H and Li. Furthermore quantitative analysis of BCN, CrN, TiN and AlTiN coatings are presented. 3D-SIMS measurements show directly the distribution of elements in two-component metal coatings (Al/Sn). Investigations on the thermal cycling stability of SiFeCr coated refractory metal alloys are presented where the different chemical phases are characterized which came into being during the heating periods.
3:30 PM		F4-1-7 Microstructure and Mechanical Properties of Nanocomposite (Ti,Si,Al)N Coatings S. Carvalho, L. Rebouta, C.J. Tavares (Universidade do Minho, Portugal); A Cavaleiro (Universidade de Coimbra, Portugal); L.A. Rocha (Universidade do Minho, Portugal) Superhard nanocomposite coatings are currently of great interest for tooling applications to improve the mechanical properties and functionality of several engineering materials. In this work (Ti,Si,Al)N coatings were produced by reactive magnetron sputtering using DC and RF power sources. Rutherford Backscattering and Electron Microprobe Analysis measured the atomic composition of the samples. X-ray diffraction and subsequent Fourier analysis of those X-ray profiles was used to investigate the structure and grain size and its correlation with hardness. XRD results enabled conclusions to be drawn about the formation of a mixture of two phases whose structure is similar to TiN. Phase 1 has a lattice parameter of 0.429 nm and develops only in the case of intense ion bombardment. This behaviour can be associated with the segregation of the SiNx phase, though the formation of an amorphous AlN phase cannot be excluded. Phase 2, with a lattice parameter 0.419 nm, develops in situations of low surface mobility. For intermediate levels of adatom surface mobility, textures with an intermediate lattice parameter (0.424 nm) were obtained. Regarding the results of ultramicrohardness tests, a hardness value of about 60 GPa was obtained for samples with a composition of about 28.5 at. % Ti, 12 at. % Al, 9,5 at. % Si and 50 at. % N. A small increase in hardness, after one hour of vacuum annealing at 800 °C, is observed. The adhesion behaviour, the wear coefficient and the friction coefficient of these coatings were also studied.
3:50 PM		F4-1-8 Microstructure of Surface and Interfaces of TiAlN/Mo Multilayers C.J. Tavares, L. Rebouta (Universidade do Minho, Portugal); E. Alves (Departamento de Física, Portugal); J.P. Rivière, H. Garem (LMP, Université de Poitiers, France) Nanocomposite multilayers were fabricated by reactive magnetron sputtering with modulation periods between 1.5 and 6 nm. The structure and composition of the TiAlN/Mo multilayers was studied by X-ray diffraction (XRD) and Rutherford Backscattering Spectroscopy (RBS), while the interface and surface morphology was studied by high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM), respectively. Particular attention has been directed to the evolution of the interfacial and surface roughness with the bias voltage. It was shown that with a bias voltage of -100 V these structures were prepared with relatively flat and smooth interfaces, albeit a certain level of intermixing being present.
4:10 PM		F4-1-9 Microstructural Characterization of Aluminum Nitride Thin Films on Si(111) and (100) Substrates Grown by Plasma Assisted Molecular Beam Epitaxy S.U. Hong, M.C. Paek, G.P. Han, Y.J. Sohn, T.Y. Kim, K.I. Cho (Electronics and Telecommunications Research Institute, South Korea); S.G. Yoon (Chung Nam National University, South Korea) Growth characteristics and microstructures of AlN thin films grown on Si(100) and (111) substrates by plasma assisted molecular beam epitaxy have been investigated. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation throughout the temperature range of 850-900°C, showing columnar growth. The columns were uniformly arranged on the whole substrate and surface morphology was rough, where the rms roughness was about 20nm more or less. However on Si(111), the AlN films were epitaxially grown to be single crystals containing lots of defects and the surface morphology was quite smoother than those on Si(100), where the rms roughness was only 4nm or more. The difference of growth mechanism between Si(100) and Si(111) have been comparatively studied using microstructural characterization techniques. TEM revealed the epitaxial growth of AlN films on Si(111) with directional coherency in AlN(0002)/Si(111), AlN(10-10)/Si(110), and AlN(11-20)/Si(112), and the x-ray diffraction showed that the coherency seemed to be slightly distorted with increasing temperature, while AlN films on Si(100) showed no directional coherency.
4:30 PM		F4-1-10 Characterization of Metal Oxide/Polymer Films. B.M. Henry, A.G. Erlat, C.R.M. Grovenor, G.A.D. Briggs (University Of Oxford, United Kingdom); Y. Tsukahara (Toppan Printing Company, Japan) The resistance to oxygen and moisture permeation of transparent metal oxide layers deposited on plastic substrates is of immense importance for applications requiring flexible films with good gas barrier properties. In this study the oxygen and water vapour permeation mechanism has been investigated for a variety of metal oxides deposited on poly(ethylene terephthalate). A range of characterisation techniques has been used including atomic force microscopy, transmission electron microscopy and secondary ion mass spectroscopy. Gas permeation equipment was used to examine the oxygen and water vapour transmission properties of the films. Results show that the oxygen permeation mechanism is primarily controlled by the presence of defects in the oxide layer. For water vapour permeation, the situation is different and there is evidence to suggest that the mechanism involve some kind of interaction with the oxide layer.
4:50 PM		F4-1-11 The Application of X-ray Slitless Collimator for a Structure Study of Thin Film Coating V.K. Egorov (Inst. of Problem of Microelectronics Technology, Russia) The slitless collimator (SC) for the x-ray radiation is one of perspective element for the x-ray optics. It was successfully applied for the x-ray fluorescence analysis of thin targets at the grazing incidence of the initial x-ray beam (TXRF-SC spectroscopy) ¹. But SC can be very useful for structure investigations of the surface coating too. Both schemes of structure surface diagnostic at the grazing x-ray beam incidence, the in-plane diffraction and the asymmetric Bragg diffraction ², can be realized on base of the slitless collimator using. In this work the SC was included to the set of the standard horizontal x-ray diffractometer HZG-4. The modified diffractometer was used for the asymmetric Bragg diffraction investigation of a polycrystal cooper film coating on a Si wafer. The design of the x-ray beam formation system and scheme of the scattering radiation collection are described. The layer thickness tested in during of experiments and the enhancement of an incident beam intensity on a target at the SC using are evaluated. Principle advantages and disadvantages of the SC application for the structure research of surface layer solids are discussed. ¹ V.K.Egorov, A.P.Zuev, O.S.Kondratiev, E.V.Egorov, Abstract Book of 8 Conference on Total Reflection X-ray Fluorescence Analysis and Related Methods, 2000, Vienna, p.49. ² W.C.Marra, P.Eisenberger, A.Y.Cho, J. Appl. Phys., v.50, #11, 1979, pp.6927-6933. .