ICMCTF2013 Session TSP: Syposium TS Poster Session

Thursday, May 2, 2013 5:00 PM in Grand Hall

Thursday Afternoon

Time Period ThP Sessions | Topic TS Sessions | Time Periods | Topics | ICMCTF2013 Schedule

TSP1 Fine Micro- and Nano-Imprinting onto DLC Coating via Controlled Oxygen Plasma Etching
Tatsuhiko Zho (Shibaura Institute of Technology, Japan); Kento Mizushima (Shibaura Institute of Tchnology, Japan); Tatsuya Fukuda (Mitsue Mold Engineering, Co. Ltd.)
Thick diamond-like carbon (DLC) coating has a potential to be used as a mold die for micro- and nano-imprinting onto metallic sheets and optical oxide-glasses. In the previous paper, our developing high-density oxygen plasma etching processing had been introduced to make micro-patterning onto DLC-coating with aid of chromium masking. Aiming at further applications, this oxygen plasma etching process must be improved by instrumentation via quantitative plasma diagnosis. In addition, masking technique had to be advanced to deal even with nano-patterns.

In the present study, resin-base masking technique is proposed as an initial patterning procedure onto DLC coated mold-die substrates. Spectroscopic measurement and Langmuir probe method are combined not only to describe the population of activated oxygen species but also to measure the transients of electron density in plasmas. Through optimization of processing conditions, high etching rate was attained up to 8 to 10 micro-meter per hour, or, 2.2 to 3.0 nm/s. Both line and grid patterns were first employed to describe anisotropic etching behavior via SEM and leaser-microscopic measurement, and, to discuss this microscopic etching with reference to reactive ion etching process. In addition, macroscopic etching behavior was also in-situ monitored by spectroscopic plasma diagnosis for rational termination of etching when the monitored peak intensity became minimum. This termination of etching provided us the stepwise depth profile of micro- and nano-grooves and grids as the three dimensional pattern onto DLC coating.

In final, this etching method was applied to make three dimensional micro-grid patterning onto DLC-coated WC (Co) mold dies. Geometric accuracy of 5.2 x 5.2 μm squared grid as well as the depth of 5 μm was attained onto the 50 x 10 mm2 mold-surface of DLC coated WC (Co) through SEM observation and laser reflection profilometer. This surface-engineered mold die was applid to duplicate these patterns onto aluminum shee via mold-stamping and to fabricate heat-radiation devices.

TSP2 Comparison of Flow Curves of Thin Films Determined by Different Finite Element Models and Nanoindenter Geometries
Kirsten Bobzin, Nazlim Bagcivan, RicardoHenrique Brugnara, Jan Perne (Surface Engineering Institute - RWTH Aachen University, Germany)
Plastic properties of thin coatings are difficult to quantify. The substrates influence on the growing films as well as the specific production environment in physical vapor deposition (PVD) leads to mechanical properties of the coatings incomparable with macroscopic scaled samples. The determination of flow curves of thin coatings using nanoindentation is intensively investigated. In this paper an approach to determine flow curves using nanoindentation with spherical indenters coupled with finite element method is introduced. The finite element model is complemented by an analytic method providing information about the initial yield strength thereby reducing the number of possible solutions for the flow curve. The approach uses an FEM model to calculate the force-displacement-curve of the nanoindentation out of an arbitrary given flow curve for the sample material. The calculated force-displacement curve is compared with the measured one to adjust the modeled samples material model. This procedure is repeated iteratively until simulated and measured force-displacement curves match. This approach is realized with models for indenters with 10 and 1 µm radius. The models are verified on reference materials with known flow curves and used to analyze different CrxAlx-1N coating systems applied using direct current and high power pulse magnetron sputtering physical vapor deposition. The chemical composition of the coatings varies from 23 to 95 at.-% chromium.
TSP3 Micro-chemical and -morphological Features of Heat Treated Plasma Sprayed Zirconia-based Thermal Barrier Coatings
Barbara Cortese, Daniela Caschera, Tilde De Caro, Gabriel Ingo (CNR, Italy)

Zirconia-based plasma-sprayed coatings are widely used in jet and land-based engines as thermal barriers coatings (TBCs) for protecting and insulating gas turbine metal components from the extreme temperature in the hot gas thus extending the engine life capabilities and service performances as well as to reduce fuel consumption. Zirconia-based thermal barrier coatings (TBCs) of nominal chemical composition 8 wt% Y2O3–ZrO2 and 25.5 wt% CeO2–2.5 Y2O3–ZrO2 were prepared by means of atmospheric plasma spray (APS) and low pressure plasma spray (LPPS) and thermal treated at different temperature (up to 1460°C, treatment time 200 hours). The heated materials have been then fractured and the resulting surfaces have been studied by means of X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM) combined with energy dispersive spectrometry (EDS) and secondary ion mass spectrometry (SIMS) in order to study the surface micro-chemical composition and morphology The results disclose the variation of the stabilising oxides amount, the occurrence of valence states modifications of cerium, impurities segregation phenomena and sintering. These information confirm that chemical and morphological aspects in plasma sprayed TBCs must be known in order to understand and predict relationships between the parameters of plasma spray process and TBC features, properties and performances for a better design of reliable TBCs.

TSP6 Deposition, Structural and Optoelectronic Properties of Bi2O3 Thin Films Deposited by Magnetron Sputtering
CeliaL. Gomez (Universidad Nacional Autonoma de Mexico, Mexico); Sandra Rodil, Phaedra Silva-Bermudez (Universidad Nacional Autónoma de México, Mexico); M. Lejeune, S. Charvet, A. Zeinert (Universite de Picardie Jules Verne, France); Enrique Camps (Instituto Nacional de Investigaciones Nucleares de Mexico)

Bismuth oxide thin films were deposited by magnetron sputtering using an α-Bi2O3 target, under an Ar/O2 (80:20) atmosphere. The power and substrate temperature were varied from 100-180 W and 125-250 oC. The films were simultaneously deposited on glass and silicon substrates; therefore spectroscopic optical characterization was done by both transmittance and ellipsometry. The film structure was studied by X-ray diffraction, obtaining strong differences in the predominant phase (mainly delta, beta and alpha) as the power or substrate temperatures were increased, which were also reflected in the deposition rate, the variations in the structure were also confirmed by Raman spectroscopy. The XPS analysis confirms that for all the conditions the composition was nearly 2:3 (Bi:O), except for minor traces of metallic bismuth found in some samples.

The electrical properties of the films were measured in planar mode for samples deposited on glass using two concentrical Pt electrodes. The measurements were done as a function of the temperature from RT to 600 oC. It was clearly shown that for all samples, the resistivity decreased as the T increased, showing an Arrhenius variation which allow us to estimate the values of the activation energy (optical gap) and the intrinsic surface conductivity. The results from the electrical properties are correlated to both the deposition conditions and the structure of the samples.

The optical properties, n and k as a function of the energy (E) from 1.5 to 5 eV, of the films were obtained by modeling the ellipsometric spectra by means of a Tauc-Lorentz dispersion model. From the k vs E curve, the absorption coefficient was calculated and compared to the data obtained from the transmission experiments. By doing this process iteratively, it was possible to have consistent parameters of the optical properties for each of the films and therefore of the Bi2O3 phases.

Acknowledgement: The research leading to these results has received funding from the European Community Seven Framework Programme (FP7-NMP-2010-EU-MEXICO) and CONACYT under grant agreements nº 263878 and 125141, respectively.

TSP8 Relationship Between the Microstructure and Thermoelectric Properties of n-type Bi-Se-Te by Using RF Sputtering
TaiSheng Chen, ChihChao Shih, HsinDing Fu, MingSheng Leu (Industrial Technology Research Institute, Taiwan)
The thermoelectric thin films have attracted great interest due to solid state operation, high reliability and zero emission. Bismuth-telluride based alloys have excellent thermoelectric properties at room temperature. In this study, we have investigated the relationship between the microstructure and thermoelectric properties of the n-type Bi-Se-Te films, which were deposited at room temperature by magnetron RF sputtering using Bi2Se0.3Te2.7 alloy targets and electric stressing annealed by rapid thermal annealing (RTA) at 300 °C for 5 min. Then, X-ray diffraction, energy dispersive spectroscopy, scanning electron microscopy, Hall, Seebeck and 3ω measurement were utilized to characterize the evolution of microstructure, composition and thermoelectric properties of Bi-Se-Te films as function of RF power, working pressure and annealing temperature. XRD results show that each film exhibits polycrystalline microstructure. The intensity of (0 1 5) peak at 27.8∘increases with increasing power and decreasing working pressure. In addition, the intensity of diffraction peaks appears to increase after electric stressing annealing. Consequently, the composition of as-deposited film is closely about target stoichiometry and after annealing films at 300°C was conserved. The surface of Bi-Se-Te film exhibits sheet-like morphology and the feature size was larger as the (0 1 5) preferred orientation. The microstructure and composition and morphology concur with the change in thermoelectric properties. The Seebeck coefficient and resistivity increase with increasing working pressure and decreasing RF power and the impact of the resistivity rather than the Seebeck lead to low power factor. However, the power factor was substantially enhanced after rapid thermal annealing due to the reduction of defect or carrier concentration and more crystallization orientation. The relationship between the microstructure and thermoelectric properties of n-type Bi-Se-Te films is discussed and established.Key words: Thermoelectric, Thin film, Seebeck, Bi-Se-Te (Bismuth selenium telluride), RF sputtering.
TSP9 Surfactant-assisted Dispersion of Polyimide/multi-walled Carbon Nanotube Nanocomposites Films with Ultrahigh Electrical Conductivity
Hsin-Pei Yu (National Chin-Yi University of Technology, Taiwan, Republic of China); Yi-Chia Huang (National Chiao Tung University, Taiwan, Republic of China); I-Hsiang Tseng, Mei-Hui (M.H.) Tsai (National Chin-Yi University of Technology, Taiwan, Republic of China)

A facile approach to disperse and stabilize high loading of multi-walled carbon nanotubes (CNTs) in polyimide (PI) matrix is presented. PI/CNT nanocomposite films were synthesized by in situ polymerization of pyromellitic acid dianhydride (PMDA) and 4,4'-oxydianiline (ODA) in N,N'-dimethyl acetamide (DMAc) with the presence of various amounts of CNTs and the surfactant polyvinylpyrrolidone (PVP) and sodium dodecyl benzene sulfonate (SDBS). The FTIR spectroscopy proved that the surfactant did not hinder the polymerization of PI. The experimental results showed that the dispersion of CNT was significantly improved by increasing the ultrasonication temperature to 60 oC. Accordingly, The electrical conductivity of PI/CNT was increased to 41.5 S/m for the hybrid film containing 40 wt% of CNT.

TSP10 Poly(amide-imide) / Graphene Oxide Nanocomposite Films for Anticorrosion Application
Chin-Wen Chang, I-Hsiang Tseng, Mei-Hui Tsai (National Chin-Yi University of Technology, Taiwan, Republic of China); Jui-Ming Yeh (Chung-Yuan Christian University, Taiwan, Republic of China)

A series of advanced anticorrosive hybrid films comprising of polyimide (PI) or poly(amide-imide) (PAI) matrix dispersed with various content of graphene oxide (GO) nanosheets have been successfully synthesized through the solution dispersion process of GO in PI or PAI. PAI was synthesized by mixing 4,4'-oxydianiline (ODA), 3,3'-4,4'-benzophenonetetracarboxylic dianhydride (BTDA), trimellitic anhydride chloride (TMAC) in N-Methyl-2-pyrrolidone ( NMP ) solvent. The content of hydroxyl groups in PAI affects the dispersion of GO in PAI matrix. The water-vapor-transmission-rate (WVTR), oxygen-transmission-rate (OTR) and corrosion resistance in saline condition of PAI/GO films were comprehensively studied and correlated with the content of GO. The PAI/GO nanocomposite films exhibit improved corrosion inhibition compared to pure PI and PAI .

TSP11 Aberration-corrected HRSTEM Characterization of Nanolaminate Copper Diffusion Barriers Grown by PEALD
C.N. Hsiao, B.H. Liou (National Applied Research Laboratories); G.S. Chen (Feng Chia University, Taiwan, Republic of China); Y.J. Cheng (National Chi Nan University); Y.S. Y. S. Lai (National Applied Research Laboratories)
Ru/TaN nanolaminate barriers and Cu interconnect were sequential directly grown on dual damascene nano-porous dielectrics (PMSQ, k < 2.3) by plasma enhanced atomic layer deposition (PEALD) for the application of 28 nm node and below. The PEALD processes for TaN, Ru and Cu employed argon/ammonia (Ar/NH3) and hydrogen (H2) plasmas. Ta(NC2H6)5 and RuEt(Cp)2 was used as the precursor source for tantalum and ruthenium while Cu(hfac)2 was used as the copper precursor source. Liner dependency of the growth rate on the precursor pulse time with different self-limited PEALD cycle number were analyzed from thickness measurements using high resolution scan transmittance electron microscopy. The growth rate of TaN was 0.05 nm/cycle as 1.5 s pulse time, 0.02 nm/cycle for Ru as 0.2 s pulse time, and 0.03 nm/cycle for Cu at the 2 s pulse time, respectively. Moreover, resistivity of nanolaminate barriers was dependent on the microstructural features by grain size and crystalline which characterized by atomic-resolution aberration-corrected HRSTEM (C1, A1, A2, B2, and C3 corrected), EDS mapping, X-ray and the sheet resistance measured by four-point probe. Additionally, various materials properties including conformability, diffusion gradient and electro-thermal stress of Ru/TaN nanolaminate barriers on dual damascene structure have been evaluated. Furthermore, the integration PEALD processes at lower substrate temperature with porous low-k dielectric and pore-sealing effect by plasma and ion beam on voiding treatment of PMSQ are also discussed.
TSP12 Kinetics of Spinodal Decomposition in Au-Ni Nanolaminates near Room Temperature
Alan Jankowski (Texas Tech University, US)

The kinetics of spinodal decomposition are affected by several factors including the alloy composition and the depression of the coherent spinodal below chemical spinodal within the miscibility gap. Within the spinodal, phase separation leads to the formation of characteristic composition wavelengths from a solid solution. In the gold-nickel (Au-Ni) alloy system, nanolaminates were used to initially create an artificial composition fluctuation with unique nanoscale wavelengths. Although the decomposition reaction has been well documented for Au-Ni in the literature, the direct measurement of the diffusivities at low temperatures, i.e. at room temperature, would require time durations on the order of several decades. This has been accomplished by now examining sputter deposited films that were synthesized in a thermalized condition 25 years ago. In addition to the aging at room temperature, the effects of strain energy are accounted for in accommodating lattice misfit in this superlattice system. For this purpose, the results of x-ray diffraction to assess the state of short-range order at grazing incidence angles are compared with scans at high angle reflections that evidence the effects of lattice distortions.

TSP13 Synthesis of CdS Thin Films with Hexagonal Orientation Through an Ammonia-free System
Kuan-Yu Chen, Su-Ching Hsiao, Bou-Jing Yang, Lih-Hsin Chou (National Tsing Hua University, Taiwan, Republic of China)
Cadmium sulfide (CdS) is a n-type semiconductor material which is known to be a window layer of high efficiency thin film solar cells such as copper indium gallium diselenide (CIGS) and cadmium telluride (CdTe). Chemical bath deposition (CBD), a low-cost and scalable technique, was often used to synthesize CdS films. Traditional CBD synthesis, which is predominantly based on one-step process, usually use ammonia as the complexing agent, though it is environmentally harmful. The films as-produced are deposited in a growth solution containing cadmium chloride, ammonia, KOH and CS(NH2)2 (thiourea) and accompanied with several disadvantages such as porous films, Cd(OH)2 byproduct and hard-controlling thickness.

In this work, a process with ammonia replaced by sodium citrate was employed for producing a more continuous, compact, homogeneous CdS thin film with controlled thickness. Cadmium acetate, instead of cadmium chloride, was used for its low-cost and not under regulation. First, Cd(OH)2 particles were deposited on the substrate, thiourea was then added to the solution and the CdS uniform thin film was formed finally. Phase determination was carried out by X-ray diffraction (XRD). It was reported that the CdS synthesized using cadmium chloride had a preferred (002) hexagonal orientation and the crystal quality produced by cadmium acetate was not as good. However, an (002) hexagonal crystal orientation was obtained in this work applying cadmium acetate by controlling the pH value in the beginning of reaction. Surface morphology of the films was observed by scanning electron microscopy (SEM). Hall measurement and optical transmission spectroscopy will be applied to determine the carrier mobility and band gap. The reaction mechanism will be discussed in this paper and the as-formed CdS films are expected to be beneficial for solar cell applications for its probable high carrier mobility and reduced carrier recombination.

TSP14 Electrical Characteristics and Stability of Metal Electrodes for Pyrite Ultra-thin Film Solar Cells
Bing-Kai Chen, Su-Ching Hsiao, Lih-Hsin Chou (National Tsing Hua University, Taiwan, Republic of China)
FeS2 (pyrite) is catching the attention gradually because of its promising potential for optoelectronic applications. It possesses a suitable band gap and very high absorption coefficient (5x105 cm-1) that makes pyrite to be one of the candidates for thin film solar cell, especially ultrathin and flexible cell, absorption material. Pyrite’s environmental compatibility and elemental abundance further assures its sustainable applications.

It is known that ohmic metal contact is essential for solar cell devices application. However, few studies has been reported for pyrite thin film devices. Schieck et al. [1] reported that platinum showed good ohmic contact characteristic on thick pyrite crystal film and R. J. Soukup et al. found the low-cost Ni metal also showed ohmic characteristic on pyrite thin film with higher resistivity. In order to get good and cheaper ohmic metal contacts for our ultrathin pyrite films, various metals were tested and stability study will be performed for the best electrode obtained in this report.

Various metals including Au, Mo, Cu, Ag, and Ni were tried in this study to find out their ohmic contact characteristic on our pyrite ultrathin films. The metal layers with thickness of 1 μm were deposited onto glass substrates by direct current magnetron sputtering under argon atmosphere. Pyrite thin film with ~50 nm thickness produced by spin coating pyrite nanoparticles ink was covered on these metal layers. Layers stacked by this sequence may avoid the destruction of the pyrite absorption layer resulted from the post deposited metal layers. For optimal choice of contact metal, a current-voltage (I-V) measurement was employed on sandwich-structured electrodes. The top metal electrodes were sputtered on the pyrite film applying a mini-pores mask so as to eliminate the plasma damage to the absorption layer. The devices were then annealed at 400 °C in sulfur ambient to improve the crystallinity of the spin-coated pyrite thin films.

Grazing incidence x-ray diffraction (GIXRD) diffractometer will be utilized to detect if phases other than pyrite and metals are present. The metal with best I-V characteristic will be adopted for further interface diffusion study. Depth profiles from nano Auger will reveal the interface diffusion between the metal layer and pyrite thin film after prolonged annealing.

Reference:

[1] R. Schieck, A. Hartmann, S. Fiechter, R. Konenkamp, and H. Wetzel, J. Mater. Res., 5 (1990) 1567.

TSP15 Nanostructure Formation of Al2O3 Layer Carried Out in a Three-Component Electrolyte
Marek Kubica (University of Silesia, Poland); Marek Bara, Władysław Skoneczny (Univesrsity of Silesia, Poland)

It has been reported that the size and shape of the pores depend on the structure of the base metal, the type of electrolyte and the conditions of the anodizing process. The paper presents thin Al2O3 oxide layer formed under hard anodizing conditions on a plate made of EN AW-5251aluminium alloy. The oxidation of the ceramic layer was carried out for sixty minutes in a three-component SFS electrolyte at a temperature of 303K, electric charge 180A*min and the current density of 3A/dm2. Presented images taken with a scanning microscope for: base material (aluminium alloy), breakdown voltage, beginning of the oxidation, five, ten and sixty minutes layer growth. A computer analysis of the binary images showed the average surface of a pore and different shapes as: triangle, rhombus, pentagon and hexagon. The structure of ceramic Al2O3 layers is one of the main factors determining chemical, physical, surface and mechanical properties. The resistance to wear of polymer-oxide coating layer depends on porosity, morphology and roughness of the ceramic layer surface. A 3D oxide coating model, based on the computer analysis of images from a scanning electron microscope (SEM), was proposed. Special computer program that shows morphology of the layer was programmed in C++ language.

TSP16 Performance Characterisation of Metallic Substrates Coated by HVOF WC-Co
Andrew Venter (Necsa Limited; DST/NRF Centre of Excellence in Strong Materials, South Africa); Philip Oladijo (DST/NRF Centre of Excellence in Strong Materials, South Africa; University of the Witwatersrand, South Africa); Vladimir Luzin (ANSTO (Australian Nuclear Science & Technology Organisation), Australia); Lesley Cornish, Natasha Sacks (DST/NRF Centre of Excellence in Strong Materials, South Africa; University of the Witwatersrand, South Africa)
The high-velocity oxygen-fuel (HVOF) thermal spray technique is extensively used by in-dustry to produce thin coatings on substrates to enhance their functional properties such as wear resistance linked to adhesion and residual stress enhancement, or to act as thermal or chemical barriers. Our research interest is the systematic characterisation of the performance of metal substrates subjected to the different processing steps associated with their HVOF coating with WC-Co.

A number of substrates that have coefficients of thermal expansion covering a range of values different to that of the coating material have been considered to assess the potential role of thermal misfit as mechanism in improving the coating performance. Both the as-coated and stress annealed conditions (40% of the respective melting temperatures) have been investigated.

The different annealing temperatures influence the final coating microstructural properties [1,2]. Depth resolved studies of the in-plane residual stresses in the coatings and substrates have been investigated using, X-ray, synchrotron and neutron diffraction techniques in con-junction with sub millimetre sized gauge volumes [1-3]. The abrasive wear performance of the coatings were characterised using an ASTM-G65 three body abrasive wear machine. Steep stress gradients have been observed in the near surface regions of all the as-coated substrates, extending to approximately 0.5 mm from the interface. It has been identified to originate primarily from the shot blast surface preparation step. Annealing had the effect of completely removing the cold work contribution and triggering the differences in the CTE’s between coating and substrates that introduced beneficial residual stresses. Differences ob-served in the wear behaviour are related to the residual stresses resulting in the coatings ow-ing to the thermal mismatch between the coatings and substrates.

[1] O.P Oladijo. A.M. Venter, L.A. Cornish, N. Sacks, X-ray diffraction Measurement of Residual Stress in WC-Co Thermally Sprayed Coatings onto Metal Substrates, Surface & Coatings Technology (2012) 206 4725

[2] A.M. Venter, T. Pirling, T. Buslaps, O.P. Oladijo, A. Steuwer, T.P. Ntsoane, L.A. Cornish, N. Sacks, Systematic investigation of the residual strains associated with WC-Co coatings thermal sprayed onto metal substrates, Surface & Coatings Technology (2012) 206 4011

[3] V. Luzin, A.M Venter, O.P. Oladijo, L.A. Cornish, N. Sacks, Residual stress in WC-Co coated systems studied by high resolution neutron diffraction, 5th Asian Thermal Spray Conference, 26 –28 November 2012, Japan. To be submitted to Journal of Thermal Spray Technology

TSP17 Micromechanical Characterisation of a-C:H Coating Systems with Si-based Adhesion Layers
Christoph Schmid, Christopher Schunk, Markus Krottenthaler, Verena Maier, Mathias Göken, Karsten Durst (University of Erlangen-Nürnberg, Germany)

A common technique to enhance the adhesion of hydrogenated amorphous carbon (a-C:H) coatings especially on steel substrates is the use of adhesion layers based on different elements like W, Cr or Si. These layers normally show a complex microstructure with chemical gradients and their thickness is less than one micron. Relating the local chemical composition to the microstructure and the mechanical properties is therefore not an easy task.

In this work two a-C:H coating systems with an Si-based adhesion layer deposited with different process parameters on steel substrates were investigated in terms of chemical composition, local mechanical properties and residual stresses. Nanoindentations across small angle cross-sections of the coating systems result in a complex hardness and Young`s modulus depth profile over the adhesion layer. Additionally, auger electron spectroscopy revealed the corresponding chemical composition. A direct correlation between the local mechanical properties and the chemical composition of the two different adhesion layers was observed.

In addition, residual stresses of the two a-C:H coating on steel substrates were determined by means of focused ion beam (FIB) milling and digital image correlation (DIC). For this a H-bar geometry which is commonly used for TEM lamella preparation was FIB milled in the a-C:H coating which causes the residual stresses to relax locally. The residual stresses can be quantified by tracking the relaxation strain with DIC. At this the H-bar geometry enables a simple evaluation of the residual stresses using Hooke’s law. For the two a-C:H coatings similar residual compressive stresses of about - 2 to -3 GPa were found.

Time Period ThP Sessions | Topic TS Sessions | Time Periods | Topics | ICMCTF2013 Schedule