Browsing by Subject "FILMS"

Sort by: Order: Results:

Now showing items 1-20 of 21
  • Fraser, James P.; Postnikov, Pavel; Miliutina, Elena; Kolska, Zdenka; Valiev, Rashid; Svorcik, Vaclav; Lyutakov, Oleksiy; Ganin, Alexey Y.; Guselnikova, Olga (2020)
    Two-dimensional (2D) transition-metal dichalcogenides have become promising candidates for surface-enhanced Raman spectroscopy (SERS), but currently very few examples of detection of relevant molecules are available. Herein, we show the detection of the lipophilic disease marker beta-sitosterol on few-layered MoTe2 films. The chemical vapor deposition (CVD)-grown films are capable of nanomolar detection, exceeding the performance of alternative noble-metal surfaces. We confirm that the enhancement occurs through the chemical enhancement (CE) mechanism via formation of a surface-analyte complex, which leads to an enhancement factor of approximate to 10(4), as confirmed by Fourier transform infrared (FTIR), UV-vis, and cyclic voltammetry (CV) analyses and density functional theory (DFT) calculations. Low values of signal deviation over a seven-layered MoTe2 film confirms the homogeneity and reproducibility of the results in comparison to noble-metal substrate analogues. Furthermore, beta-sitosterol detection within cell culture media, a minimal loss of signal over 50 days, and the opportunity for sensor regeneration suggest that MoTe2 can become a promising new SERS platform for biosensing.
  • Hautala, Jaana; Kääriäinen, Tommi; Hoppu, Pekka; Kemell, Marianna; Heinämäki, Jyrki; Cameron, David; George, Steven; Juppo, Anne Mari (2017)
    We introduce atomic layer deposition (ALD) as a novel method for the ultrathin coating (nanolayering) of minitablets. The effects of ALD coating on the tablet characteristics and taste masking were investigated and compared with the established coating method. Minitablets containing bitter tasting denatonium benzoate were coated by ALD using three different TiO2 nanolayer thicknesses (number of deposition cycles). The established coating of minitablets was performed in a laboratory-scale fluidized-bed apparatus using four concentration levels of aqueous Eudragit (R) E coating polymer. The coated minitablets were studied with respect to the surface morphology, taste masking capacity, in vitro disintegration and dissolution, mechanical properties, and uniformity of content. The ALD thin coating resulted in minimal increase in the dimensions and weight of minitablets in comparison to original tablet cores. Surprisingly, ALD coating with TiO2 nanolayers decreased the mechanical strength, and accelerated the in vitro disintegration of minitablets. Unlike previous studies, the studied levels of TiO2 nanolayers on tablets were also inadequate for effective taste masking. In summary, ALD permits a simple and rapid method for the ultrathin coating (nanolayering) of minitablets, and provides nanoscale-range TiO2 coatings on porous minitablets. More research, however, is needed to clarify its potential in tablet taste masking applications. (C) 2017 Elsevier B.V. All rights reserved.
  • Perez-Tanoira, Ramon; Horwat, David; Kinnari, Teemu J.; Perez-Jorge, Concepcion; Gomez-Barrena, Enrique; Migot, Sylvie; Esteban, Jaime (2016)
    The aim of this study was to compare the bacterial adhesion of Staphylococcus spp. on Ti-6Al-4V with respect to Ti-6Al-V modified alloys with a set of Cubic yttria stabilized zirconia (YSZ) and Ag-YSZ nanocomposite films. Silver is well known to have a natural biocidal character and its presence in the surface predicted to enhance the antimicrobial properties of biomedical surfaces. Microbial adhesion tests were performed using collection strains and twelve clinical strains of Staphylococcus aureus and Staphylococcus epidermidis. The adherence study was performed using a previously published protocol by Kinnari et al. Both collection strains and clinical isolates have shown lower bacterial adhesion to materials modified with respect to the alloy Ti-6Al-4V and the modification with silver reduced the bacterial adhesion for most of all the strains studied. Moreover the percentage of dead bacteria have been evaluated, demonstrating increased proportion of dead bacteria for the modified surfaces. Nanocrystalline silver dissolves releasing both Ag+ and Ag-0 whereas other silver sources release only Ag+. We can conclude that YSZ with nanocrystalline silver coating may lead to diminished postoperative infections and to increased corrosion and scratch resistance of YSZ incorporating alloys Ti-6Al-4V.
  • Reyes, Guillermo; Lundahl, Meri; Alejandro-Martin, Serguei; Arteaga-Perez, Luis; Oviedo, Claudia; King, Alistair; Rojas, Orlando J. (2020)
    Hydrogels of TEMPO-oxidized nanocellulose were stabilized for dry-jet wet spinning using a shell of cellulose dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium propionate ([DBNH][CO2Et]), a protic ionic liquid (PIL). Coagulation in an acidic water bath resulted in continuous core-shell filaments (CSFs) that were tough and flexible with an average dry (and wet) toughness of similar to 11 (2) MJ.m(-3) and elongation of similar to 9 (14) %. The CSF morphology, chemical composition, thermal stability, crystallinity, and bacterial activity were assessed using scanning electron microscopy with energy-dispersive X-ray spectroscopy, liquid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, pyrolysis gas chromatography-mass spectrometry, wide-angle X-ray scattering, and bacterial cell culturing, respectively. The coaxial wet spinning yields PIL-free systems carrying on the surface the cellulose II polymorph, which not only enhances the toughness of the filaments but facilities their functionalization.
  • Zhang, Xue; Viitala, Tapani; Harjumäki, Riina; Kartal-Hodzic, Alma; Valle-Delgado, Juan Jose; Österberg, Monika (2021)
    The development of in vitro cell models that mimic cell behavior in organs and tissues is an approach that may have remarkable impact on drug testing and tissue engineering applications in the future. Plant based, chemically unmodified cellulose nanofibrils (CNF) hydrogel is a natural, abundant, and biocompatible material that has attracted great attention for biomedical applications, in particular for threedimensional cell cultures. However, the mechanisms of cell-CNF interactions and factors that affect these interactions are not yet fully understood. In this work, multi-parametric surface plasmon resonance (SPR) was used to study how the adsorption of human hepatocellular carcinoma (HepG2) cells on CNF films is affected by the different proteins and components of the cell medium. Both human recombinant laminin 521 (LN-521, a natural protein of the extracellular matrix) and poly -L-lysine (PLL) adsorbed on CNF films and enhanced the attachment of HepG2 cells. Cell medium components (glucose and amino acids) and serum proteins (fetal bovine serum, FBS) also adsorbed on both bare CNF and on protein-coated CNF substrates. However, the adsorption of FBS hindered the attachment of HepG2 cells to LN-521and PLLcoated CNF substrates, suggesting that serum proteins blocked the formation of laminin-integrin bonds and decreased favorable PLL-cell electrostatic interactions. This work sheds light on the effect of different factors on cell attachment to CNF, paving the way for the utilization and optimization of CNF-based materials for different tissue engineering applications. (C) 2020 The Authors. Published by Elsevier Inc.
  • Kupka, K.; Leino, A. A.; Ren, W.; Vazquez, H.; Åhlgren, E. H.; Nordlund, K.; Tomut, M.; Trautmann, C.; Kluth, P.; Toulemonde, M.; Djurabekova, F. (2018)
    Stable C-C bonds existing in several sp hybridizations place carbon thin films of different structural compositions among the materials most tolerant to radiation damage, for applications in extreme environments. One of such applications, solid state electron stripper foils for heavy-ion accelerators, requires the understanding of the structural changes induced by high-energy ion irradiation. Tolerance of carbon structure to radiation damage, thermal effects and stress waves due to swift heavy ion impacts defines the lifetime and operational efficiency of the foils. In this work, we analyze the consequences of a single swift heavy ion impact on two different amorphous carbon structures by means of molecular dynamic simulations. The structures are constructed by using two different recipes to exclude the correlation of the evolution of sp2-to-sp3 hybridization with the initial condition. Both initial structures contain approximately 60% of sp2-bonded carbon atoms, however, with different degree of clustering of atoms with sp3 hybridization. We simulate the swift heavy ion impact employing an instantaneous inelastic thermal spike model. The analysis of changes in density, bonding content and the number and size of carbon primitive rings reveals graphitization of the material within the ion track, with higher degree of disorder in the core and more order in the outer shell. Simulated track dimensions are comparable to those observed in small angle x-ray scattering measurements of evaporation-deposited amorphous carbon stripper foils irradiated by 1.14 GeV U ions.
  • Hynninen, Ville; Hietala, Sami; McKee, Jason R.; Murtomäki, Lasse; Rojas, Orlando J.; Ikkala, Olli; Nonappa, [No Value] (2018)
    We show that composite hydrogels comprising methyl cellulose (MC) and cellulose nanocrystal (CNC) colloidal rods display a reversible and enhanced rheological storage modulus and optical birefringence upon heating, i.e., inverse thermoreversibility. Dynamic rheology, quantitative polarized optical microscopy, isothermal titration calorimetry (ITC), circular dichroism (CD), and scanning and transmission electron microscopy (SEM and TEM) were used for characterization. The concentration of CNCs in aqueous media was varied up to 3.5 wt % (i.e, keeping the concentration below the critical aq concentration) while maintaining the MC aq concentration at 1.0 wt %. At 20 degrees C, MC/CNC underwent gelation upon passing the CNC concentration of 1.5 wt %. At this point, the storage modulus (G') reached a plateau, and the birefringence underwent a stepwise increase, thus suggesting a percolative phenomenon. The storage modulus (G') of the composite gels was an order of magnitude higher at 60 degrees C compared to that at 20 degrees C. ITC results suggested that, at 60 degrees C, the CNC rods were entropically driven to interact with MC chains, which according to recent studies collapse at this temperature into ring-like, colloidal-scale persistent fibrils with hollow cross-sections. Consequently, the tendency of the MC to form more persistent aggregates promotes the interactions between the CNC chiral aggregates towards enhanced storage modulus and birefringence. At room temperature, ITC shows enthalpic binding between CNCs and MC with the latter comprising aqueous, molecularly dispersed polymer chains that lead to looser and less birefringent material. TEM, SEM, and CD indicate CNC chiral fragments within a MC/CNC composite gel. Thus, MC/CNC hybrid networks offer materials with tunable rheological properties and access to liquid crystalline properties at low CNC concentrations.
  • Liu, Jian; Muinos, Henrique Vazquez; Nordlund, Kai; Djurabekova, Flyura (2020)
    As a promising material used in accelerators and in space in the future, it is important to study the property and structural changes of graphene and diamond-like carbon on the surface as a protective layer before and after swift heavy ion irradiation, although this layer could have a loose structure due to the intrinsic sp(2) surrounding environment of graphene during its deposition period. In this study, by utilizing inelastic thermal spike model and molecular dynamics, we simulated swift heavy ion irradiation and examined the track radius in the vertical direction, as well as temperature, density, and sp(3) fraction distribution along the radius from the irradiation center at different time after irradiation. The temperature in the irradiation center can reach over 11000 K at the beginning of irradiation while there would be a low density and sp(3) fraction area left in the central region after 100 ps. Ring analysis also demonstrated a more chaotic cylindrical region in the center after irradiation. After comprehensive consideration, diamond-like carbon deposited by 70 eV carbon bombardment provided the best protection.
  • Forsman, Nina; Johansson, Leena-Sisko; Koivula, Hanna; Tuure, Matilda; Kääriäinen, Pirjo; Österberg, Monika (2020)
    Environmental benign cellulosic textiles are hampered by their tendency to absorb water, which restricts their use in functional clothing. Herein we describe a method to functionalize textile surfaces using thin, open coatings based on natural wax particles and natural polymers rendering cellulosic fabrics water-repellent while retaining their feel and breathability. The impact of curing temperature, cationic polymer and fabric properties on wetting and long-term water-repellency were studied using contact angle measurements and scanning electron microscopy. The wetting properties were correlated to roughness of the textiles using white light interferometer. X-ray photoelectron spectroscopy revealed the surface chemical composition, leading to fundamental understanding of the effect of annealing on the wax layer. Breathability was evaluated by water vapor permeability. The optimal curing temperature was 70 °C. The developed coating performed well on different natural textiles, and better than commercial alternatives. A set of garment prototypes were produced using the coating.
  • Liekkinen, Juho; Enkavi, Giray; Javanainen, Matti; Olmeda, Barbara; Pérez-Gil, Jesús; Vattulainen, Ilpo (2020)
    Surfactant protein B (SP-B) is essential in transferring surface-active phospholipids from membrane-based surfactant complexes into the alveolar air-liquid interface. This allows maintaining the mechanical stability of the surfactant film under high pressure at the end of expiration; therefore, SP-B is crucial in lung function. Despite its necessity, the structure and the mechanism of lipid transfer by SP-B have remained poorly characterized. Earlier, we proposed higher-order oligomerization of SP-B into ring-like supramolecular assemblies. In the present work, we used coarse-grained molecular dynamics simulations to elucidate how the ring-like oligomeric structure of SP-B determines its membrane binding and lipid transfer. In particular, we explored how SP-B interacts with specific surfactant lipids, and how consequently SP-B reorganizes its lipid environment to modulate the pulmonary surfactant structure and function. Based on these studies, there are specific lipid-protein interactions leading to perturbation and reorganization of pulmonary surfactant layers. Especially, we found compelling evidence that anionic phospholipids and cholesterol are needed or even crucial in the membrane binding and lipid transfer function of SP-B. Also, on the basis of the simulations, larger oligomers of SP-B catalyze lipid transfer between adjacent surfactant layers. Better understanding of the molecular mechanism of SP-B will help in the design of therapeutic SP-B-based preparations and novel treatments for fatal respiratory complications, such as the acute respiratory distress syndrome. (C) 2020 The Author(s). Published by Elsevier Ltd.
  • Harjumaki, Riina; Nugroho, Robertus Wahyu N.; Zhang, Xue; Lou, Yan-Ru; Yliperttula, Marjo; Valle-Delgado, Juan Jose; Österberg, Monika (2019)
    In vitro cell culture or tissue models that mimic in vivo cellular response have potential in tissue engineering and regenerative medicine, and are a more economical and accurate option for drug toxicity tests than animal experimentation. The design of in vivo-like cell culture models should take into account how the cells interact with the surrounding materials and how these interactions affect the cell behavior. Cell-material interactions are furthermore important in cancer metastasis and tumor progression, so deeper understanding of them can support the development of new cancer treatments. Herein, the colloidal probe microscopy technique was used to quantify the interactions of two cell lines (human pluripotent stem cell line WA07 and human hepatocellular carcinoma cell line HepG2) with natural, xeno-free biomaterials of different chemistry, morphology, and origin. Key components of extracellular matrices -human collagens I and IV, and human recombinant laminin-521-, as well as wood-derived, cellulose nanofibrils -with evidenced potential for 3D cell culture and tissue engineering- were analysed. Both strength of adhesion and force curve profiles depended on biomaterial nature and cell characteristics. The successful growth of the cells on a particular biomaterial required cell-biomaterial adhesion energies above 0.23 nJ/m. The information obtained in this work supports the development of new materials or hybrid scaffolds with tuned cell adhesion properties for tissue engineering, and provides a better understanding of the interactions of normal and cancerous cells with biomaterials in the human body.
  • Nugroho, Robertus Wahyu N.; Harjumäki, Riina; Zhang, Xue; Lou, Yan-Ru; Yliperttula, Marjo; Valle-Delgado, Juan Jose; Österberg, Monika (2019)
    Biomaterials of different nature have been and are widely studied for various biomedical applications. In many cases, biomaterial assemblies are designed to mimic biological systems. Although biomaterials have been thoroughly characterized in many aspects, not much quantitative information on the molecular level interactions between different biomaterials is available. That information is very important, on the one hand, to understand the properties of biological systems and, on the other hand, to develop new composite biomaterials for special applications. This work presents a systematic, quantitative analysis of self- and cross-interactions between films of collagen I (Col I), collagen IV (Col IV), laminin (LN-521), and cellulose nanofibrils (CNF), that is, biomaterials of different nature and structure that either exist in biological systems (e.g., extracellular matrices) or have shown potential for 3D cell culture and tissue engineering. Direct surface forces and adhesion between biomaterials-coated spherical micro-particles and flat substrates were measured in phosphate-buffered saline using an atomic force microscope and the colloidal probe technique. Different methods (Langmuir-Schaefer deposition, spin-coating, or adsorption) were applied to completely coat the flat substrates and the spherical micro particles with homogeneous biomaterial films. The adhesion between biomaterials films increased with the time that the films were kept in contact. The strongest adhesion was observed between Col IV films, and between Col IV and LN-521 films after 30 s contact time. In contrast, low adhesion was measured between CNF films, as well as between CNF and LN-521 films. Nevertheless, a good adhesion between CNF and collagen films (especially Col I) was observed. These results increase our understanding of the structure of biological systems and can support the design of new matrices or scaffolds where different biomaterials are combined for diverse biological or medical applications.
  • Ahvenniemi, Esko; Akbashev, Andrew R.; Ali, Saima; Bechelany, Mikhael; Berdova, Maria; Boyadjiev, Stefan; Cameron, David C.; Chen, Rong; Chubarov, Mikhail; Cremers, Veronique; Devi, Anjana; Drozd, Viktor; Elnikova, Liliya; Gottardi, Gloria; Grigoras, Kestutis; Hausmann, Dennis M.; Hwang, Cheol Seong; Jen, Shih-Hui; Kallio, Tanja; Kanervo, Jaana; Khmelnitskiy, Ivan; Kim, Do Han; Klibanov, Lev; Koshtyal, Yury; Krause, A. Outi I.; Kuhs, Jakob; Kaerkkaenen, Irina; Kaariainen, Marja-Leena; Kääriäinen, Tommi; Lamagna, Luca; Lapicki, Adam A.; Leskelä, Markku; Lipsanen, Harri; Lyytinen, Jussi; Malkov, Anatoly; Malygin, Anatoly; Mennad, Abdelkader; Militzer, Christian; Molarius, Jyrki; Norek, Malgorzata; Ozgit-Akgun, Cagla; Panov, Mikhail; Pedersen, Henrik; Piallat, Fabien; Popov, Georgi; Puurunen, Riikka L.; Rampelberg, Geert; Ras, Robin H. A.; Rauwel, Erwan; Roozeboom, Fred; Sajavaara, Timo; Salami, Hossein; Savin, Hele; Schneider, Nathanaelle; Seidel, Thomas E.; Sundqvist, Jonas; Suyatin, Dmitry B.; Torndahl, Tobias; van Ommen, J. Ruud; Wiemer, Claudia; Ylivaara, Oili M. E.; Yurkevich, Oksana (2017)
    Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency. (C) 2016 Author(s).
  • Pitkänen, Leena M.; Heinonen, Marina; Mikkonen, Kirsi S. (2018)
    A growing population and concern over the sufficiency of natural resources for feeding this population has motivated researchers and industries to search for alternative and complementary sources of food ingredients and additives. Numerous plant species and parts of plants are explored as raw materials for food production. An interesting example is wood; to date, few wood-based additives or ingredients are authorized for food use. Wood hemicelluloses, such as softwood galactoglucomannans (GGM), constitute an abundant bioresource that shows a highly potential functionality in edible materials. Spruce GGM—“spruce gum”—acts as a multi-functional emulsion stabilizer, and it could be used in various processed food products, replacing less effective, conventional emulsifiers. Before new materials can be released onto the food market, their safety must be evaluated, according to the Novel Food regulation. This review focuses on the safety aspects that must be considered before polysaccharide- and phenolic-rich plant extracts can be awarded the status of authorized food ingredients. In this review, GGM is presented as a case study and examples are given of plant-based polysaccharides that are already authorized for food purposes. The legislation regarding Novel Food ingredients in Europe is also briefly reviewed.
  • Dinh, Van Tuan; Kotakoski, Jani; Louvet, Thibaud; Ortmann, Frank; Meyer, Jannik C.; Roche, Stephan (2013)
  • Mynttinen, Elsi; Wester, Niklas; Lilius, Tuomas; Kalso, Eija; Koskinen, Jari; Laurila, Tomi (2019)
    Tramadol (TR) is a member of the opioid family and is widely used for pain treatment in clinical patient care. The analgesic effect of tramadol is induced primarily by its main metabolite Odesmethyltramadol (ODMT). Due to interindividual differences in the TR metabolism to ODMT, the responses to TR vary highly between patients. Thus, a fast and selective method for simultaneous detection of TR and ODMT would increase the patient safety and pain treatment efficacy. In this study, a tetrahedral amorphous carbon (ta-C) electrode coated with a thin dip-coated recast Nafion membrane was fabricated for selective electrochemical determination of TR and ODMT. With this Nafion/ta-C electrode, simultaneous detection of TR and ODMT was achieved with linear ranges of 1-12.5 mu M and 1-15 mu M, respectively. The limits of detection were 131 nM for TR and 209 nM for ODMT. Both analytes were also measured in the presence of several common interferents, demonstrating the high selectivity of the fabricated electrode. In addition, the effect of pH on the peak potential was studied to observe the electrochemical behavior of the analytes at the electrode. Finally, clinically relevant concentrations of TR and ODMT were simultaneously detected from diluted human plasma to assess the applicability of the electrode in real samples. The fabricated Nafion/ta-C electrode was found successful in the simultaneous electrochemical detection of TR and ODMT in both buffer solution and in human plasma. (C) 2018 Elsevier Ltd. All rights reserved.
  • Holland-Moritz, Henry; Ilinov, Andrey; Djurabekova, Flyura; Nordlund, Kai; Ronning, Carsten (2017)
    Ion beam processing of surfaces is well known to lead to sputtering, which conventionally is associated only with erosion of atoms from the material. We show here, by combination of experiments and a newly developed Monte Carlo algorithm, that in the case of nanoparticles in a regular two-dimensional array on surfaces, the redeposition of sputtered atoms may play a significant role on the system development. The simulations are directly compared to in situ experiments obtained using a dual focused Ga+ ion beam system and high resolution scanning electron microscopy, and explain the size evolution by a combination of sputtering and redeposition of sputtered material on neighboring particles. The effect is found to be dependent on the size of the nanoparticles: if the nanoparticle size is comparable to the ion range, the reposition is negligible. For larger nanoparticles the redeposition becomes significant and is able to compensate up to 20% of the sputtered material, effectively reducing the process of sputtering. The redeposition may even lead to significant growth: this was seen for the nanoparticles with the sizes much smaller than the ion range. Furthermore, the algorithm shows that significant redeposition is possible when the large size neighboring nanoparticles are present.
  • Mirhashemihaghighi, Shadi; Swiatowska, Jolanta; Maurice, Vincent; Seyeux, Antoine; Klein, Lorena H.; Salmi, Emma; Ritala, Mikko; Marcus, Philippe (2016)
    Surface smoothening by substrate annealing was studied as a pre-treatment for improving the corrosion protection provided to copper by 10, 20 and 50 nm thick alumina coatings deposited by atomic layer deposition. The interplay between substrate surface state and deposited film thickness for controlling the corrosion protection provided by ultrathin barrier films is demonstrated. Pre-annealing at 750 degrees C heals out the dispersed surface heterogeneities left by electropolishing and reduces the surface roughness to less than 2 nm independently of the deposited film thickness. For 10 nm coatings, substrate surface smoothening promotes the corrosion resistance. However, for 20 and 50 nm coatings, it is detrimental to the corrosion protection due to local detachment of the deposited films. The weaker adherence of the thicker coatings is assigned to the stresses accumulated in the films with increasing deposited thickness. Healing out the local heterogeneities on the substrate surface diminishes the interfacial strength that is bearing the stresses of the deposited films, thereby increasing adhesion failure for the thicker films. Pitting corrosion occurs at the local sites of adhesion failure. Intergranular corrosion occurs at the initially well coated substrate grain boundaries because of the growth of a more defective and permeable coating at grain boundaries. (C) 2016 Elsevier B.V. All rights reserved.
  • Sharma, Varun; Blomberg, Tom; Haukka, Suvi; Cembella, Shaun; Givens, Michael E.; Tuominen, Marko; Odedra, Rajesh; Graff, Wes; Ritala, Mikko (2021)
    In this work, thermal based gas-phase etching of titanium nitride (TiN) is demonstrated using thionyl chloride (SOCl2) as a novel etchant. A single etchant is utilised in a pulsed fashion to etch TiN. This type of etching technique may also be considered as a chemical gas-phase or dry etching. The removed TiN amount was measured by various techniques like spectroscopic ellipsometry (SE), weighing balance and in some cases X-ray reflectometry (XRR). Additionally, the post-etch surfaces were analysed with X-ray photoelectron spectroscopy (XPS) and bright field transmission electron microscopy (BF-TEM). The surface roughness and morphology of before and after etching TiN films were measured using atomic force microscopy (AFM). The etch per cycle (EPC) was calculated and is plotted as a function of SOCl2 pulse time, purge time after SOCl2 exposure, number of etch cycles and etch temperature (T-etch). An increase in EPC with an increase in SOCl2 pulse time as well as etch temperature was observed. SOCl2 is able to etch TiN starting from 270 degrees C with an EPC of about 0.03 angstrom to almost 1.2 angstrom at 370 degrees C. Arrhenius plot determined the activation energy (E-a) of about 25 kcal/mol for TiN etching by SOCl2. In addition, the etch selectivity between different substrates such as silicon dioxide (SiO2), silicon nitride (Si3N4) and aluminum oxide (Al2O3) was investigated on blanket as well as 3D structures. Moreover, thermodynamic calculations were performed for various possible etch reactions. Titanium from TiN is proposed to be etched in the form of either titanium trichloride (TiCl3) or titanium tetrachloride (TiCl4). Nitrogen from TiN films may form volatile by-products such as diatomic nitrogen (N-2), nitrous oxide (N2O) and nitrogen dioxide (NO2).