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Agradecimentos: We thank Dr. Dario Campana, St Jude Children’s Research Hospital for kindly providing the hTERT + bone marrow mesenchymal cell line. We also acknowledge Prof. Dr. Antonio Riul Junior and Dr. Mawin Javier Martinez Jimenez from DFA-IFGW, UNICAMP, for their support in the electrochemical tests. This work was supported by the São Paulo Research Foundation (FAPESP), grants #2019/18460-4, #2019/04943-3 and #2018/24461-0 and FAPERGS, grant #19/2551-0002288-3. FC and LLA are FAPESP fellows. VP is CAPES fellow (grant #88887.475264/2020-00). JAY, CAF and FA are CNPq fellows Abstract: This study combines the brand new concept of high-entropy designed materials with the superior properties of metallic glasses to obtain a NbTaTiVZr high-entropy metallic glass (HEMG) coating for biomedical applications. The amorphous structure is achieved by a room temperature magnetron sputtering deposition, whereas a bcc crystalline phase, typical of high-entropy alloys (HEA), is obtained at 400 degrees C. X-ray photoelectron spectroscopy showed that the oxygen concentration on the coatings surface is > 50% and significantly higher than in the bulk (similar to 5%). The NbTaTiVZr(O) HEMG surface is completely passivated, in contrast to the metallic + oxide outermost layer found for the HEA. Potentiodynamic polarization tests attested an improved corrosion resistance of the HEMG surface, which showed also increased hydrophilicity compared to the crystalline sample. In vitro biocompatibility investigations using both the hTERT-immortalized bone marrow mesenchymal cells and MG-63 osteosarcoma cells showed excellent viability (similar to 98% and similar to 96%, respectively) and adhesion onto the HEMG coating after 96 h of incubation, indicating the integrity and biosafety of this surface. The cell viability and proliferation on the HEA and Ti (used as a benchmark) surfaces were much inferior. The enhanced surface protection and the superior biocompatibility makes the HEMG promising to be employed as a biocoating on orthopedic implants FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGS COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

Agradecimentos: This work was financially supported by the Brazilian agencies CNPq and FAPESP-FAPERGS (Grant 2019/18460–4). ARZ and FA are CNPq fellows (Grants 303233/2017–6 & 302370/2015–3). FGE and FC are FAPESP fellows (Grants 2019/00757–0 & 2018/24461–0) Abstract: To a large extent, future technological progress relies on the study-development of advanced materials with new and/or improved properties. The semiconductors titanium oxynitride (TixOyNz) and titanium dioxide (TiO2) perfectly meet these requirements in the sense that their main chemical and structural properties can be customized, leading to successful contributions in optics, electronics, catalysis, bactericides surfaces, and photovoltaics applications, for instance. Motivated by these aspects, this paper reports on the structure and optical bandgap of TixOyNz, as obtained by Raman scattering and optical transmittance spectroscopy, respectively. The study comprises a set of films produced by N-2-plasma Ti sputtering and subsequently thermal annealed in an atmosphere of oxygen flux. As the thermal treatments advance, the Raman spectra indicate a gradual transformation of the films from amorphous+(nano/micro-)crystalline TixOyNz to the crystalline Rutile phase of TiO2 (R-TiO2). Consistent with these structural changes, the optical bandgap of the films decreases from - 3.2 to 2.5 eV, i.e., across part of the ultraviolet-blue spectral region. The analysis of the experimental data confirms the importance of nitrogen (in the early stages of sample preparation) on the achievement of R-TiO2 in a continuous and controllable way. Therefore, this paper shows the suitability of the TixOyNz compound to produce films with well-defined crystalline TiO2-related structures and specific optical bandgap values CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGS Fechado

Agradecimentos: The authors are grateful to UCS, CAPES to PROSUC (#88887.153304/2017-00) and PDSE (#88881.362240/2019-01) for financial support to C.D.B. and CNPq (#422372/2016-1), FAPERGS (#19/2551-0002288-3), FAPESP (#2019/18460-4), and Plasmar Tecnologia Ltda. (#1408-25.51/14-6) for financial support. C.D.B., L.M.L., A.F.M., J.S.W., and C.A.F are CNPq or CAPES fellows. F.C. is an FAPESP fellow (project #2018/24461-0). The authors R.S., M.E., F.F., and A. C. would also like to thank funding from CEMMPRE UIDB/00285/2020 [co-financed via FEDER and FCT] and the IFGW-UNICAMP and Epipolé Research Group for their willingness to help with this research Abstract: The low adhesion of amorphous carbon (a-C) films on ferrous alloys has restricted massive industrial application since their development, restricting application to mechanical and electromechanical components. Although different mechanisms have been raised to describe the a-C film adhesion, the chemical affinity and the role of oxygen at the interfaces are the key issue. Nevertheless, a quantitative approach considering the oxygen adsorption and the adhesion strength/base pressure relationship is still not proposed, which would be of special interest in industry. In this study, we analyze the influence of the base pressure on the adhesion of amorphous carbon (a-C) films onto a ferrous alloy intermediated by a nanometric silicon interlayer. The different base pressure deposition resulted in different adhesion of the films. By means of structural and chemical techniques, the oxygen content at the interfaces was quantified and correlated with the base pressure before thin film deposition. We propose a quantitative physicochemical model that correlates the a-C film adhesion with oxygen located at the interfaces, which is indirect evidence of its previous presence in the deposition chamber, as a fraction of the residual gases from the base pressure. As adhesion depends on oxygen content, we used the Langmuir isothermal law to evaluate this dependence with good agreement. This model may be of potential interest in plasma surface engineering and process automatization not only for carbon-related materials deposited on metals, mainly in its potential use as a solid lubricant COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGS FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: This work was financially supported by the Brazilian agencies CNPq and FAPESP (Project 2019/18460-4). ARZ and FA are CNPq fellows (Grants 303233/2017-6 & 302370/2015-3). FC and FGE are FAPESP fellows (Grants 2018/24461-0 & 2019/00757-0) Abstract: Owing to its singular and (to some extend) adaptable characteristics, titanium oxynitride (TixOyNz) represents an exceptional choice in the realm of new materials aiming at the development of practical devices. However, the effective use of TixOyNz in photovoltaic and (photo)catalysis applications, for example, relies on a refined production-properties balance. Accordingly, this paper reports on the physico-chemical properties of TixOyNz films as investigated by means of the Raman scattering and X-ray photoelectron spectroscopy (XPS) techniques - the former shedding light on the structural characteristics of the films, and the latter providing the state of oxidation of the film's constituents. The films were prepared by sputtering TiO2 and Ti targets in a plasma comprising different mixtures of Ar and N-2. Because of the deposition method and conditions, the films exhibit Raman spectra that are consistent with a combination of TiO2 and TiN or, more properly, TixOyNz under the amorphous and (nano/micro-)crystalline structures. In fact, the experimental data indicate the presence of four TiO2- and two TiN-related phonon modes, whose relative scattering features scale with the oxygen and nitrogen contents of the films. A similar concentration dependence was verified with the percentage of Ti4+, Ti3+, and Ti2+ chemical states of oxidation. This mutual concentration dependence was explored thoroughly and the results clearly indicate the suitability of the Raman data to estimate the typical atom composition and distribution of the Ti-related chemical states of TixOyNz CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

Agradecimentos: This work was supported by the São Paulo Research Foundation (FAPESP), grants #2019/18460-4 and #2018/24461-0, and FAPERGS, grant #19/2551-0002288-3. FC is FAPESP fellow. SRSM is CAPES fellow. CAF and FA are CNPq fellow Abstract: Metallic sputtered high-entropy alloy (HEA) thin films often result in amorphous structures, due to the film growth kinetics and the large atomic size mismatch of the constituent elements. In this paper, single-phase crystalline NbTaTiVZr HEA thin films were achieved by the appropriate choice of both the alloying elements and the synthesis conditions. Regarding the latter, substrate biasing prompts Ar+ ion irradiation during film growth, whereas substrate heating increases the adatom mobility, inducing specific structural modifications. The control of both variables eliminates traditional crystallization strategies, such as adding nitrogen to the gas mixture during film growth or post-thermal annealing of the as-deposited films. Therefore, we have investigated the relationship between the synthesis conditions, the structure, and the mechanical properties of a Nb20Ta26-Ti22V16Zr16 HEA thin film, due to its potential application in the field of refractory coating materials. The asdeposited films prepared at 400 degrees C possessed a body-centered cubic (bcc) phase, and their preferential orientation changed according to the bias voltage value (V-b) chosen. Low energy ion irradiation (V-b approximate to -25 V) resulted in crystallite coarsening and surface roughening. On the other hand, higher negative bias voltages (V-b approximate to -75 V) led to lower growth rates, grain refining, and improved mechanical properties. In addition, the chemical states and composition were determined by X-ray photoelectron spectroscopy (XPS) and the HEA phase formation was predicted using empirical parameters and compared to the results obtained by the Calculation of Phase Diagrams (CALPHAD) approach FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGS COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

Agradecimentos: This work was partially supported by The Royal Society – UK (award "Royal Society-Newton Advanced Fellowship" - NAF\R2\192108), the French National Center for Scientific Research (CNRS), the Brazilian National Council of Scientific and Technological Development (CNPq – projects: 233194/2014-2, 465423/2014-0, and 422372/2016-1), and Research Support Foundation of the State of Rio Grande do Sul (FAPERGS – projects: 17/2551-0001052-3 and 19/2551-0000656-0). F.C. and F.G.E. are FAPESP fellows (projects 2018/24461-0 and 2019/00757-0). B.L.P., S.R.S.M, and L.M.L. are CAPES fellows. C.A.F and F.A. are CNPq fellows. A.C. and T.P. acknowledge the support from the project ?Novel nanostructures for engineering applications? No. CZ.02.1.01/0.0/0.0/16_026/0008396 and The Ministry of Education, Youth and Sports from the Large Infrastructures for Research, Experimental Development and Innovations project ?e-Infrastructure CZ – LM2018140? and the use of VESTA software Abstract: In dry sliding, the coefficient of friction depends on the material pair and contact conditions. If the material and operating conditions remain unchanged, the coefficient of friction is constant. Obviously, we can tune friction by surface treatments, but it is a nonreversible process. Here, we report active control of friction forces on TiO2 thin films under UV light. It is reversible and stable and can be tuned/controlled with the light wavelength. The analysis of atomic force microscopy signals by wavelet spectrograms reveals different mechanisms acting in the darkness and under UV. Ab initio simulations on UV light-exposed TiO2 show a lower atomic orbital overlapping on the surface, which leads to a friction reduction of up to 60%. We suggest that photocontrol of friction is due to the modification of atomic orbital interactions from both surfaces at the sliding interface CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGS FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Fechado

Agradecimentos: This work was financially supported by the Brazilian agencies FAPESP (projects 2012/10127-5 and 2019/18460-4) and FAPERGS (project 19/2551-0002288-3). Partial support of CONICET (PIP 2017-2019 GI-11220170100289CO) and UBACyT (20020170200298BA). F.C. is a FAPESP fellow, project 2018/24461-0. D.S., A.R.Z., C.A.F., and F.A. are CNPq fellows. This work is part of the PhD Thesis of D.S. The authors are indebted to C. Piacenti for his technical support. The authors acknowledge "Universidade Estadual de Campinas" (UNICAMP) for APC funding Abstract: The role played by oxygen vacancies and rare earth (RE) elements in the anatase-to-rutile (A-R) phase transformation of titanium dioxide (TiO2) is still a matter of controversy. Here, we report the A-R transformation of TiO2 thin solid films as obtained by ion beam sputtering a RE-decorated titanium target in an oxygen-rich atmosphere. The samples correspond to undoped, single-doped (Sm, Tm, and Tb), and codoped (Sm:Tb, Sm:Tm, and Sm:Tb:Tm) TiO2 films. In the as-prepared form, the films are amorphous and contain similar to 0.5 at. % of each RE. The structural modifications of the TiO2 films due to the RE elements and the annealing treatments in an oxygen atmosphere are described according to the experimental results provided by Raman scattering, X-ray photoelectron spectroscopy, and optical measurements. The A-R transformation depends on both the annealing temperature and the characteristics of the undoped, single-doped, and codoped TiO2 films. As reported in the literature, the A-R transformation can be inhibited or enhanced by the presence of impurities and is mostly related to energetic contributions. The experimental results were analyzed, considering the essential and stabilizing role of the entropy of mixing in the A-R transformation due to the introduction of more and multiple quantum states originated in vacancies and impurities in the anatase phase FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGS Aberto

Agradecimentos: This work was supported by the Sao Paulo Research Foundation (FAPESP), grants #2019/18460–4 and #2018/24461–0, FAPERGS, grants #17/2551-0001052-3 and #19/2551-0002288-3, and CNPq, grant #422372/2016–1. FC is FAPESP fellow. MJMJ and LML are CAPES fellows. CAF and FA are CNPq fellows. The authors would like to thank the technician R.B. Merlo for the annealing experiments execution and R. Marcon for his help in XRD treatment data. Abstract: The vast, unexplored chemical realm of multi-principal element alloys (MPEAs) has encouraged researchers to design and synthetize advanced materials based on refractory metals, metalloids, and deoxidizer elements, that are expected to follow single-phase, solid solution high-entropy alloys (HEAs)’ footsteps. In this paper, we have theoretically and experimentally studied the AlSiTaTiZr alloy in the thin film form, due to potential applications as a high-temperature oxidation-resistant coating. The MPEA film, synthetized by radio-frequency magnetron sputtering (RFMS), shows a considerable glass-forming ability. However, the metallic glass structure transits to several intermetallic compound phases by post-thermal annealing at ~873 K, confirming that both thermodynamics and kinetics determine the formation of phases in sputtered MPEAs. Moreover, a strong tendency of Si and Al to form compounds with transition metals was revealed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermodynamic investigations. Special focus is given to the role played by both entropy and enthalpy on the phase evolution, demonstrated by thermodynamic calculations using the regular solution model and the CALculation of PHAse Diagrams (CALPHAD) method. This methodology is presented as a useful approach for starting deeper thermodynamic investigations in the thin film literature of MPEAs and HEAs, currently focused on the ultimate properties of such alloys FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DO RIO GRANDE DO SUL - FAPERGS CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES Fechado

Agradecimentos: The authors wish to acknowledge Dr. Philippe Guerin for his technical assistance on the sputter-deposition system. This work was supported by the French National Center for Scientific Research (CNRS) and the Brazilian National Council of Scientific and Technological Development (CNPq, "Ciencia sem Fronteiras") through Project No. 233194/2014-2. FC is CNPq fellow. GA acknowledges financial support from the MC2 Project funded by French ANR program (Project No. ANR-13-MERA-0002-02). The authors are grateful to CTU IEF-Minerve, which is partly supported by the RENATECH network and the General Council of Essonne Abstract: Ion bombardment during film growth usually induces high compressive stress in compound thin film materials, resulting in rupture and failure of coated tools used in tribological applications. Hence, intrinsic stress generated during film growth can drastically limit the industrial appeal of deposition technologies such as high power impulse magnetron sputtering (HiPIMS). This work investigates how to reduce high stress levels by tuning the HiPIMS discharge conditions and selecting the appropriate substrate bias configuration. The strategy is based on optimizing the process discharge parameters, leading to HiPIMS discharges containing fewer multiply charged energetic metal ions, which is combined with pulsed substrate bias synchronized to the HiPIMS pulse to control the chemical nature of the incident ions, i.e., inert gas vs. metal ions. The study was performed during growth of TiN thin films, due to their relevance as a protective coating, and the intrinsic stress was measured in situ during film growth using the wafer curvature method and a multi-beam optical stress sensor. The results show that for standard HiPIMS discharges and biased substrates, the energetic metal ion bombardment results in very dense, compact microstructures, but highly stressed TiN films. On the other hand, when using the here proposed strategy mentioned above, the compressive stress was considerably reduced (by a factor 11) while retaining rather compact microstructures compared to direct current magnetron sputtered as well as non-biased HiPIMS samples CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Aberto

High power impulse magnetron sputtering (HiPIMS) is a thin film deposition technique where the deposition flux is predominantly composed of ionized sputtered material. This enables control of energy and direction of the film-forming species and is thereby beneficial for tailoring the film structure and final properties. Although researchers world-wide have spent significant time and efforts characterizing and understanding the plasma process conditions in HiPIMS, research in new and improved HiPIMS-based thin film materials that find applications in areas of importance for society is still required. The goal of this work has been to identify and optimize the deposition parameters that allow tailoring the film microstructure, intrinsic stress and energy-related properties, such as electrical resistivity and optical band gap, to ultimately achieve superior HiPIMS coatings compared to what is achieved today using conventional deposition techniques. Three material systems constitute the core of the work: copper, titanium dioxide, and titanium nitride. From the work carried out it is concluded that the most important parameters affecting the film structure and properties are the amount as well as the kinetic energy of the ionized sputtered species irradiating the film during growth. These parameters differ substantially for optimum growth conditions of metallic and compound films., La pulvérisation cathodique magnétron pulsée à haute puissance (HiPIMS) est un procédé de dépôt de couches minces dans lequel le flux de dépôt est principalement composé d’ions du matériau pulvérisé. Ce type de décharge permet de contrôler l’énergie et la direction des espèces qui seront déposées, ce qui est favorable à la modification de la structure et des propriétés finales des couches. Malgré tous les travaux de recherches menés pour caractériser et comprendre les conditions de décharge HiPIMS, la nécessité de développer des couches minces utiles à la société reste toujours d’actualité. La finalité de ce travail est l’obtention de couches minces HiPIMS plus performantes que celles obtenues aujourd'hui en utilisant des techniques de dépôt classiques. Pour cela il est indispensable d'identifier et d'optimiser les paramètres de dépôt permettant de modifier à la fois la microstructure des couches, la contrainte résiduelle et les propriétés liées à l'énergie telles que la résistivité électrique et la bande interdite. Trois matériaux sont au cœur de ce travail : le cuivre, le dioxyde de titane et le nitrure de titane. Les études expérimentales ont montré que les paramètres les plus importants pour obtenir les propriétés souhaitées étaient la quantité et l’énergie cinétique des espèces ionisées irradiant la couche au cours de sa croissance. Par ailleurs, les paramètres de croissance optimale entre couches métalliques et couches composées diffèrent considérablement.

High power impulse magnetron sputtering (HiPIMS) is a thin film deposition technique where the deposition flux is predominantly composed of ionized sputtered material. This enables control of energy and direction of the film-forming species and is thereby beneficial for tailoring the film structure and final properties. Although researchers world-wide have spent significant time and efforts characterizing and understanding the plasma process conditions in HiPIMS, research in new and improved HiPIMS-based thin film materials that find applications in areas of importance for society is still required. The goal of this work has been to identify and optimize the deposition parameters that allow tailoring the film microstructure, intrinsic stress and energy-related properties, such as electrical resistivity and optical band gap, to ultimately achieve superior HiPIMS coatings compared to what is achieved today using conventional deposition techniques. Three material systems constitute the core of the work: copper, titanium dioxide, and titanium nitride. From the work carried out it is concluded that the most important parameters affecting the film structure and properties are the amount as well as the kinetic energy of the ionized sputtered species irradiating the film during growth. These parameters differ substantially for optimum growth conditions of metallic and compound films.; La pulvérisation cathodique magnétron pulsée à haute puissance (HiPIMS) est un procédé de dépôt de couches minces dans lequel le flux de dépôt est principalement composé d’ions du matériau pulvérisé. Ce type de décharge permet de contrôler l’énergie et la direction des espèces qui seront déposées, ce qui est favorable à la modification de la structure et des propriétés finales des couches. Malgré tous les travaux de recherches menés pour caractériser et comprendre les conditions de décharge HiPIMS, la nécessité de développer des couches minces utiles à la société reste toujours d’actualité. La finalité de ce travail est l’obtention de couches minces HiPIMS plus performantes que celles obtenues aujourd'hui en utilisant des techniques de dépôt classiques. Pour cela il est indispensable d'identifier et d'optimiser les paramètres de dépôt permettant de modifier à la fois la microstructure des couches, la contrainte résiduelle et les propriétés liées à l'énergie telles que la résistivité électrique et la bande interdite. Trois matériaux sont au cœur de ce travail : le cuivre, le dioxyde de titane et le nitrure de titane. Les études expérimentales ont montré que les paramètres les plus importants pour obtenir les propriétés souhaitées étaient la quantité et l’énergie cinétique des espèces ionisées irradiant la couche au cours de sa croissance. Par ailleurs, les paramètres de croissance optimale entre couches métalliques et couches composées diffèrent considérablement.

O carbono tipo diamante (DLC) é um material de revestimento que tem atraído grande interesse devido às propriedades de alta resistência ao desgaste e baixo coeficiente de atrito. Intercamadas contendo silício são amplamente utilizadas para melhorar a adesão do DLC em ligas ferrosas, embora o fenômeno que gera a adesão ainda não seja bem entendido. Neste contexto, o objetivo desse estudo é compreender claramente os fenômenos físico-químicos e as ligações químicas que são responsáveis pela adesão de filmes de DLC sobre aços, utilizando intercamadas contendo silício produzidas em diferentes condições de processamento. Os filmes foram depositados sobre o aço AISI 4140 por deposição química a vapor assistida por plasma pulsado de corrente contínua utilizando confinamento eletrostático. As intercamadas foram produzidas a partir de tetrametilsilano em diferentes tempos e temperaturas de deposição, e o filme de DLC foi subsequentemente depositado sobre as intercamadas a partir de acetileno, utilizando-se as mesmas condições experimentais para todas as amostras. A estrutura físico-química dos filmes produzidos foi avaliada por microscopia eletrônica de varredura, espectroscopia de Raios X por dispersão em energia, espectroscopia de emissão óptica por descarga luminescente e espectroscopia Raman. As ligações químicas nas interfaces do sistema aço/intercamada/DLC foram avaliadas por espectroscopia de fotoelétrons excitados por Raios X. Por fim, a carga crítica para delaminação dos filmes foi medida por testes de nanoesclerometria linear. Os resultados mostraram que a espessura e a estrutura química das intercamadas são dependentes do tempo e da temperatura de deposição, mas a temperatura foi estabelecida como o parâmetro chave de controle da cinética de reação e de crescimento da intercamada. A intercamada é estruturada como um carbeto de silício amorfo hidrogenado com formação preferencial de ligações Si–C em temperaturas de deposição a partir de 300°C. Para as amostras com intercamada depositada a partir dessa temperatura de transição, a adesão dos filmes de DLC é alcançada, sem delaminação espontânea. A melhora na adesão está associada com as ligações químicas formadas nas interfaces. Enquanto as ligações C–C e Si–C são formadas na interface intercamada/DLC, ligações Si–Fe são formadas na interface aço/intercamada. A presença de hidrogênio e oxigênio residual na estrutura da intercamada prejudica a adesão dos filmes de DLC. Conselho Nacional de Desenvolvimento Científico e Tecnológico. Diamond-like carbon (DLC) is a thin film material that has attracted much attention due to its properties as high wear resistance and super-low friction coefficient. Although silicon-based intermediate layers are employed to enhance the adherence of DLC films on ferrous alloys, the role of such buffer layers is not yet understood in chemical terms. In this context, the aim of this study is to clearly understand the physical-chemical phenomena and chemical bonding guaranteeing the DLC adhesion on ferrous alloys using Si-based interlayers deposited by different process conditions. The films were deposited on AISI 4140 steel by pulsed direct current plasma enhanced chemical vapor deposition assisted by electrostatic confinement. The interlayers were grown from tetramethylsilane at different deposition temperatures and times and the DLC thin film was grown from acetylene with the same experimental conditions for all samples. The physical-chemical structure of the bi-layers produced was evaluated by scanning electron microscopy, energy-dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy and Raman spectroscopy. The local chemical bonds at the interfaces of the steel/interlayer/DLC structure were evaluated by X-ray photoelectron spectroscopy. Finally, the critical loads for thin films delamination were measured by nanoscratch testing. The results show that the interlayer thickness and structure are dependent on both deposition time and temperature, but the temperature was established as being the key parameter controlling the reaction kinetic and the interlayer growth. The interlayer is structured as a hydrogenated amorphous silicon carbide alloy with enhanced formation of Si–C bonds at deposition temperatures ≥ 300°C. At such transition temperature of interlayer deposition, adhesion of DLC is reached, with no spontaneous delamination. The improved adhesion is associated with the nature of chemical bonds formed in the interfaces. Whereas C–C and C–Si bonds are formed on the interlayer/DLC interface, the steel/interlayer interface is constituted by Si–Fe bonds. The presence of hydrogen and residual oxygen in the interlayer structure degrades the adhesion of DLC thin films.