ICMCTF2012 Session B2-1: B2-1-:CVD Coatings and Technologies

Thursday, April 26, 2012 8:00 AM in Room Royal Palm 4-6

Thursday Morning

Time Period ThM Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF2012 Schedule

Start Invited? Item
8:00 AM B2-1-1 AlTiN-CVD coatings - a new coating family for cast iron cutting with a high productivity
Philipp Immich, Uwe Kretzschmann, Uwe Schunk, Matthias Rommel (LMT Fette Werkzeugtechnik, Germany); Reinhard Pitonak, Roland Weißenbacher (Böhlerit, Austria)

The ever increasing demand for higher productivity in manufacturing requires advanced hard coatings. The coatings can be tailored using PVD and CVD processes to exhibit for example higher hardness and / or enhanced oxidation resistance and good adhesion. Nowadays most PVD coatings based on the Ti-Al-N system with addition of silicon, chromium, boron or yttrium and are commercial available. The system Ti-Al-N offers a very good combination of a hardness and ductility. PVD coatings offering compared to CVD coatings compressive stresses without any post treatment and high deposition rates. But the development horizon on the PVD Ti-Al-N system is limited, because starting at around 66at% Aluminium content a phase change from the cubic to the wurzite structure can be seen.

On the other side CVD processes offering a good adhesion and are very stable process behaviour especially at the deposition of oxide coatings. Also they offering compared to the PVD processes even using the new HIPIMS process a nearly homogenous coating distribution around the cutting edge. Depending on the insert geometry a high coating thickness on the cutting face offering high wear resistance. Since the last couple of years no new hard coatings systems were investigated and developed in the CVD sector. The development focus was often - working on the stress behaviour in the coating or the coating architecture.

Today in the field of cast iron cutting PVD-TiAlSiN or even PVD-AlTiN coatings with a high hot hardness compete against well establish CVD TiN/TiCN/alpha-Al2O3 or kappa-Al2O3 coatings gaining more and more market share in the milling and also in the turning operation.

The logic development way is now the combination of the good things from both worlds: the system Ti-Al-N from PVD and the good adhesion and coating distribution from CVD.

By using a new developed the CVD process it is possible to deposit cubic AlTiN-CVD coatings even above 70% Aluminium with superior coating properties.

In this regard this coating family was analysed using common thin film techniques revealing hardness, Young´s modulus and coating adhesion. This new develop coating is tested in milling experiments in cast iron comparing conventional state of the art hard-coatings. The developed coating shows a significant increase of tool life even at higher cutting speeds.

8:20 AM B2-1-2 C2H6 as precursor for low pressure chemical vapour deposition of TiCNB hard coatings
Christoph Czettl (Ceratizit Austria GmbH, Austria); Christian Mitterer (Montanuniversität Leoben, Austria); Marianne Penoy, Claude Michotte (Ceratizit Luxembourg S.àr.l., Luxembourg); Martin Kathrein (Ceratizit Austria GmbH, Austria)
Multilayered hard coatings grown by chemical vapor deposition (CVD) are used for wear protection of indexable cemented carbide inserts, applied in turning, milling, parting and grooving operations. A TiCN base layer deposited at low temperatures is a crucial feature for wear resistance and toughness of the tools. Beside the medium-temperature TiCN process using CH3CN as carbon feed, which is commonly used for hard coatings, C2H6 can be applied to deposit TiCN with high carbon content at temperatures around 920 °C. In order to influence the structure and properties of this base layer, three different amounts of BCl3 were added to the feed gas. The deposition runs were carried out using an industrial-scale low-pressure CVD system. The coatings were grown using a TiCl4-C2H6-H2-N2-BCl3 feed gas system with a total flux of 65.6 l/min. The deposition temperature was 920 °C, the deposition pressure 1.6×104 Pa. The thickness of the coatings was measured by light optical microscopy on polished cross-sections. Phase composition and preferred orientation of crystallites were characterized by X-ray diffraction and transmission electron microscopy. Surface topography and fracture cross-sections were investigated by scanning electron microscopy. Surface roughness was measured using a confocal profilometer. Indentation hardness and indentation modulus of the coatings were determined using nanoindentation with a Berkovich indentor. The chemical composition of the different coatings was analyzed by glow discharge optical emission spectroscopy. The increasing amount of BCl3 in the feed gas resulted in higher boron contents of the coating, which in turn yielded higher hardness and modified microstructures. The grain size decreased with increasing boron content, while the morphology changed from equiaxed grains to a fine lamellar structure. Transmission electron microscopy analyses showed that the incorporation of boron led to a homogenous distribution of voids within the TiCN grains and to an increasing density of defects with increasing boron content. In milling and turning tests, an increased lifetime for coatings with low amounts of boron compared to the TiCN coatings without boron was obtained.
8:40 AM B2-1-3 The Effects of Microstructure and Thermal Stresses on the Hardness of CVD Deposited α‐Al2O3 and TiCxN(1‐x) Coatings
Harry Chien (Carnegie Mellon University, US); Zhigang Ban, Paul Prichard, Yixiong Liu (Kennametal Incorporated, US); Gregory Rohrer (Carnegie Mellon University, US)

The microstructures of four different CVD Deposited α‐Al2O3 and TiCxN(1‐x) coatings were determined by cross sectional electron backscatter diffraction mapping. The harnesses of the layers were also measured by nanoindentation. Using the microstructural data as input, two‐dimensional finite element analysis was used to calculate the residual thermal stresses in these materials. The thermal stresses and stored elastic energy in the α‐Al2O3 layer are larger than those in the TiCxN(1‐x) layer. Furthermore, the mean value and distribution of stored elastic energy are influenced by the texture in the alumina layer. Coatings with weaker texture have a broader distribution of thermal stresses. Coatings with alumina oriented so that the [0001] direction is parallel to the film growth direction have less stored elastic energy. This is because the thermal expansion perpendicular to [0001] is less than the thermal expansion parallel to [0001] and, therefore, the thermal expansion mismatch between the alumina coating and the substrate is minimized when grains are oriented with [0001] perpendicular to the substrate. The thermal stresses in hypothetical coatings with synthetic microstructures were also computed. These calculations tested the effects of coating thickness, channel crack spacing, composition of the TiCxN(1‐x) layer, grain aspect ratio, and cobalt enrichment of the substrate on the thermal stresses. Based on the thermal stresses, it is concluded that the three most significant factors influencing coating hardness, ordered from most significant to least significant, are the composition of the TiCxN(1‐x) layer, the channel crack spacing, and the cobalt enrichment of the substrate.

9:20 AM B2-1-5 3D EBSD analysis of CVD ceramics coatings
Makoto Igarashi, Akira Osada (Mitsubishi Materials Corporation, Japan); Christopher Schuh (Massachusetts Institute of Technology, US)

Al2O3 and TiCN coatings have been widely used in cutting tools. TiCN has high hardness. Al2O3 maintains high hardness and excellent oxidation resistance under such a severe cutting condition. Moreover, it is well known that the orientations of these coatings effect their performance. For instance, specific oriented Al2O3 represents higher performance than the other orientations. These coatings are deformed during cutting, and wear out at last. Therefore it is necessary to investigate the deformation mechanism of such ceramics coatings.

In this study, (422) and (220) oriented TiCN coatings and (006) oriented Al2O3 coatings with low and high CSL boundaries are prepared. These samples are indented with Micro Vickers . Deformed areas are observed in 3 dimension s with FIB and EBSD system. The effects of orientations and grain boundaries on deformation are discussed in details.

9:40 AM B2-1-6 TiSiN and TiSiCN hard coatings by CVD
Ingolf Endler, Mandy Höhn, Jenny Schmidt, Sebastian Scholz, Mathias Herrmann (Fraunhofer IKTS, Germany); Martin Knaut (TU Dresden, Germany)

TiN and TiCxNy are commercial CVD coatings widely used for cutting tool applications. A promising route for improving hardness and oxidation resistance is the addition of silicon. Thermal CVD method was employed using gas mixtures containing TiCl4 and the silicon chlorides SiCl4 or Si2Cl6. This work is focussed on the investigation of structure, composition and properties of the TiSiN and TiSiCN coatings deposited on hardmetal inserts.

TiSiN layers with a nanocomposite structure were obtained with SiCl4 as well as Si2Cl6 in a temperature range between 800°C and 900°C. In both cases ammonia was used as nitrogen precursor. The crystalline phases TiN, and at 900°C Ti5Si3 as well, were analysed by XRD. From the TEM investigation of a layer deposited at 850°C it is evident that the nanocrystalline TiN is embedded in an amorphous phase. The amorphous phase is silicon nitride. The hardness correlates well with the silicon content and the grain size. A maximum hardness about 37 GPa was observed at a silicon content between 6 and 8 at.% if SiCl4 was applied as silicon precursor. In this silicon concentration range a TiN grain size of 14.5 nm was determined. If Si2Cl6 was used the hardness maximum of 38 GPa was already achieved at a lower silicon content of 3.5 at.%. The corresponding TiN grain size is 16.4 nm. The investigation of the oxidation behavior showed an increase of the oxidation resistance with the silicon content. In the case of layers with silicon contents between 5 and 8 at.% an oxidation resistance up to 700°C was observed. At this temperature a weak TiO2 formation occurred at the surface.

Furthermore TiSiCN coatings were deposited using the same titanium and silicon precursors. The ratios of the silicon precursors to TiCl4 were varied. Hardness values up to 40 GPa were measured for optimum ratios. The structure was analysed by SEM, XRD and XPS.

The examination of the adherence of TiSiN and TiSiCN layers showed that a diffusion barrier is necessary for suppressing the cobalt diffusion from cemented carbide substrate into the layers. If interlayers of TiN or TiCN were applied critical loads of 80 N for TiSiN and 50 N for TiSiCN layers were obtained from scratch test measurements.

10:00 AM B2-1-7 High temperature chemical vapor deposition of highly crystallized and textured silicon on metals for solar conversion
Ouassila Gourmala, Rym Benaboud, Guy Chichignoud, Elisabeth Blanquet, Carmen Jimenez, Beatrice Doisneau, Kader Zaidat, Michel Pons (Grenoble INP, France)

Highly crystallized silicon layers were grown on metal sheets at high temperature (950°C) by thermal CVD from silane. An intermediate buffer layer (TiN layer) was mandatory to prevent interdiffusion and silicide formation but also to compensate lattice parameters and thermal expansion coefficients mismatches between metal and silicon and ideally transfer some crystalline properties (grain size, texture) from the substrate to the silicon layer. After a thermodynamic study, intermediate titanium nitride diffusion barrier was selected and processed by CVD. Special attention is given to the substrate surface preparation for texture transfer. The structure and the interfaces stabilities of these silicon/nitride/metal stacks were studied by FEG and TEM, X-ray diffraction, Raman and energy dispersive X-ray spectroscopy.

By both optimizing substrate preparation and silicon processing conditions, this multilayered structure could be able to provide an efficient and reliable converter, comparable with classical crystalline silicon wafers in terms of solar conversion yield, while overcoming their majors drawbacks: due to ingot sawing and squaring as well as wafer slicing.

10:20 AM B2-1-8 In-line Deposition of Silicon-based Films by Hot-Wire Chemical vapor Deposition
Lothar Schäfer, Tino Harig, Markus Höfer, Artur Laukart (Fraunhofer IST, Germany); Dietmar Borchert, Sinje (S.) Keipert-Colberg (Fraunhofer ISE, Germany); Jutta Trube (Leybold Optics GmbH, Germany)
Silicon-based films such as hydrogenated amorphous (a-Si:H), and nanocrystalline silicon (µc-Si:H), and hydrogenated amorphous silicon nitride (a-SiNx:H) were deposited by hot-wire gas phase activation (HW-CVD). To evaluate the opportunities of the HW-CVD technology for thin film deposition in solar industry an in-line hot-wire CVD system was used to deposit a-Si:H films for passivation of crystalline solar cells as well as for the fabrication of thin film silicon solar cells. The HW-CVD system consists of seven vacuum chambers including three hot-wire systems with maximum deposition areas of 500 mm by 600 mm for each hot-wire activation source. The deposition processes were investigated by applying design of experiment methods to identify the effects and interactions of the process parameters on the deposition characteristics and film properties. The process parameters investigated were silane flow, pressure, substrate temperature, film thickness, as well as temperature, diameter and number of wires, respectively. Growth rates up to 2.5 nm/s were achieved for a-Si:H films. Intrinsic a-Si:H films for passivation of different crystalline solar cell types yielded carrier lifetimes of more than 1.000 µs for film thickness values below 20 nm. Films with thickness values of about 350 nm show microstructure factors of less than 0.1 measured by FTIR and photosensitivity ratios of up to 106. For n-doped a-Si:H films prepared with PH3 as dopant gas specific electrical resistances are in the range of 102 Ohm x cm. P-doped a-Si:H films prepared with B2H6 as dopant gas show electrical resistances of about 105 Ohm x cm. The results of these investigations are not only aiming at the passivation of crystalline solar cells but also at the application of hot-wire CVD processes for the fabrication of heterojunction solar cells as well as thin film silicon solar cells.
11:00 AM B2-1-10 Highly chemically reactive AP-CVD coatings: Influence of the deposition parameters and application for thermally reversible interfacial bonding.
Maryline Moreno-Couranjou, Anton Manakhov, Nicolas Boscher (Centre de Recherche Public - Gabriel Lippmann, Luxembourg); Jean-Jacques Pireaux (University of Namur (FUNDP), Belgium); Patrick Choquet (Centre de Recherche Public - Gabriel Lippmann, Luxembourg)

In this work, we present the plasma copolymerization of Maleic Anhydride (MA) and Vinyltrimethoxysilane (VTMOS) performed in an Atmospheric Pressure-Dielectric Barrier Discharge process for the formation of highly reactive anhydride functionalized coatings.

In the first part of the presentation, we will show how the tuning of the electrical parameter led to coatings with different combination of anhydride/carboxylic group surface density, morphology and deposition rate. For that goal, the power (P) delivered by the source was varied from 50 to 150W. Moreover, the discharge electrical mode was operating in a continuous wave or a pulsed wave with a pulse ON-time (ton) fixed at 10ms and a pulse OFF-time (toff) ranging from 10 to 60ms. The different coating chemistries have been studied by XPS for the estimation of the anhydride/carboxylic surface density and by ATR FT-IR to investigate the conservation or the destruction of the cyclic anhydride group related to the incorporation of the MA monomer in the coatings. The average power (Pav), defined as Pav=P.[ton/(ton+toff)], appeared as a key parameter to control the anhydride surface functionalization within a range of 2 to 13 at.%, independently of the coatings morphology or deposition rate.

In the second part, we will present how the coatings reactivity has been exploited for the elaboration of a thermally reversible interfacial bonding property based on a Diels-Alder reaction. For that, MA-VTMOS deposits have been performed on a rigid polished aluminium and on a kapton foil and subsequently, treated through a chemical gas phase reaction for the grafting of the required diene and dienophile groups. The complete chemical path reaction will be exposed with some adhesion results dealing with the Diels-Alder and the retro-Diels-Alder reactions.

11:20 AM B2-1-11 Optical properties of the ZnO thin films grown on glass substrates using catalytically generated high-energy H2O
Eiichi Nagatomi, Souichi Satomoto, Masami Tahara, Takahiro Kato, Kanji Yasui (Nagaoka University of Technology, Japan)

Zinc oxide (ZnO) is useful for many applications such as transparent conductive films in solar cells and flat panel displays, optoelectronic devices operating at short wavelengths. Despite the advantages of MOCVD for industrial applications, ZnO film growth by conventional MOCVD consumes a lot of electric power to react the source gases and raise the substrate temperature. To overcome this, a more efficient means of reacting oxygen and metalorganic source gases is needed. In addition to the low reaction efficiency, conventional CVD methods yield low-quality ZnO films, due to incomplete reaction of metalorganic source gases with oxygen source gases in the gas phase. If thermally excited water is used to hydrolyze the metalorganic source gases, however, reactive ZnO precursors are produced in the gas phase, allowing growth of ZnO films under energy-saving conditions.

In this study, we present a ZnO film growth on glass substrates aiming at the application for transparent conductive thin films, using the reaction between dimethylzinc (DMZn) and high-energy H2O produced by a Pt-catalyzed H2-O2 reaction. CVD apparatus is comprised of a catalytic cell with a fine nozzle, gas lines for H2, O2 and DMZn supplies, and a substrate holder. H2 and O2 gases were admitted into a catalyst cell containing a Pt-dispersed ZrO2 catalyst, whose temperature increased rapidly to over 1300 K due to the exothermic reaction of H2 and O2 on the catalyst. The resulting high-energy H2O molecules were ejected from the fine nozzle into the reaction zone and allowed to collide with DMZn ejected from another fine nozzle. ZnO films were grown on glass substrates at 573-873K and the film properties were evaluated.

X-ray diffraction patterns of the ZnO films grown at 673-873K exhibited intense (0002) peak at 2q=34.42-34.47˚, which means that small tensile stress exists in the ZnO/glass films grown in our method. Average transmittance in the wavelength between 500 nm and 2000 nm was higher than 85%.

In the photoluminescence (PL) spectra measurement at room temperature, band edge emission of ZnO films appeared at 3.27-3.30eV. The PL spectra at 17.8K showed the strongest emission peaks at 3.357-3.360eV, which are attributed to the neutral-bound excitons Dox. The FWHM value of the strongest peak of the film grown at 673K was as low as 6.34 meV, which is smaller than that previously reported for ZnO (10meV) obtained by MOCVD grown on sapphire substrates (using Zn(C2H5)2 and N2O as source gases).

11:40 AM B2-1-12 Efficiency of indium oxide with doped tin by thermal evaporation and their optoelectronic properties
Ko-Ying Pan (National Tsing Hua University, Taiwan); Lang-Da Lin (Chinese Culture University, Taiwan); Li-Wei Chang, Han-Chang Shih (National Tsing Hua University, Taiwan)

Three nano-architectures of indium oxide (In2O3) have been successuflly synthesized by thermal evaporation, which include nanorods, nanotowers, and tin-doped indium oxide (ITO) nanorods. Judging from the images of transmission electron microscope (TEM) analysis and the x-ray diffraction (XRD) analysis, the slight dopping of tin did not affect and change the growth direction and in-situ micro-structure of nano indium oxide. The qualitative analysis of ITO nanorods were analysized by energy dispersive spectrometer (EDS) and x-ray photoelectron spectroscopy (XPS), which confrimed that slight tin were totally dpoed into nanorods of indium oxide via thermal evaporation. The optoelectronic properties of In2O3 and ITO nanorods were tested by cathodoluminescence (CL) analysis. There are blue shifts in the CL spectrums, which also means tin was definitely added in In2O3 nanorods. The results of I-V curve show that the resistance of nanorods, nanotowers and ITO are 1.32 k Ω, 0.65 k Ω and 0.063 k Ω . According to this result, dopping slight tin is a good approaching to enhance the conductivity of In2O3 nanorods.

Time Period ThM Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF2012 Schedule