Electrical properties of cr/crn nano-multilayers produced by the unbalanced magnetron sputtering technique

Chromium nitride (CrN) films have been applied to several steels as protective coatings against wear and corrosion due to their excellent mechanical properties and corrosion resistance, and in the electronic field these films are commonly used due to their low electrical resistivity. However, it has been found that multilayers combining metal/ceramic films could enhance mechanical and electrical properties compared with their monolayer counterparts, due to the higher amount and interaction between interfaces. In this work, Cr/CrN nano-multilayers have been produced through the unbalanced magnetron sputtering technique with three different degrees of unbalance, in order to study the influence of this parameter on electrical properties. Cr/CrN multilayers with approximately 1 μm of total thickness and a bilayer period (Λ) of 200 nm, 100 nm, and 20 nm were produced at room temperature on H13 steel and silicon (100); and their microstructure and electrical properties as a function of the magnetic field were evaluated. The phase formation was characterized through x-ray diffraction, and results presented (111) and (200) preferred orientations for all the multilayers. Cross section images were obtained through scanning electron microscopy and a multilayer structure can be clearly seen

Evaluating the corrosion resistance of ubm-deposited cr/crn multilayers

This work was aimed at evaluating the corrosion resistance of multilayer Cr/CrN coatings deposited by the unbalan-ced magnetron sputtering (UBM) technique. Coatings were produced at room temperature using 400 mA discharge current, 9 sccm argon flow and 3 sccm nitrogen flow. The total thickness of coatings deposited on AISI 304 stainless steel and silicon (100) varied between 0.2 a 3 μm as bilayer period varied between 20 and 200 nm. Coating microstructure and chemical composition was stu-died through scanning electron microscopy (SEM) and tex-ture and crystalline phases were analysed by X-ray diffraction (XRD) before and after corrosion tests which were carried out by potentiodynamic polarisation using 0.5 M H2SO4 + 0.05M KSCN solution. Lower bilayer period coatings presented better corrosion resistance and their corrosion mechanism is discussed in this article.En este artículo se evalúa la resistencia a la corrosión de los recubrimientos en multicapa de Cr/CrN depositados mediante la técnica de sputtering con magnetrón desba-lanceado, UBM. Los recubrimientos se produjeron a tem-peratura ambiente, con corriente de descarga de 400 mA y flujos de Ar de 9 sccm y de N2 de 3 sccm. El espesor total de los recubrimientos depositados sobre los sustratos de acero inoxidable AISI 304 y silicio (100) se varió entre 0,2 y 3 μm, al igual que el periodo de la bicapa, que estuvo entre 20 y 200 nm. La microestructura y compo-sición química de los recubrimientos se analizó por medio de microscopía electrónica de barrido (SEM), y la textura y fases cristalinas con difracción de rayos X (XRD), antes y después de las pruebas de corrosión, las cuales se rea-lizaron con ensayos de polarización potenciodinámica empleando una solución de 0,5M H2SO4 + 0,05M KSCN. Los recubrimientos con menor período de la bica-pa presentaron la mejor resistencia a la corrosión y su mecanismo de corrosión se discute en este estudio

Estudio comparativo de la evaluación a la corrosión de recubrimientos de crn y crn/cr con recubrimientos de cromo electrodepositado y pinturas tipo epoxy

En este trabajo se compara la resistencia a la corrosión de recubrimientos de CrN y CrN/Cr depositados con el sistema de sputtering con magnetrón desbalanceado (UBM) con recubrimientos industriales de Cr y pinturas tipo epoxy. Los recubrimientos UBM fueron optimizados y producidos a temperatura ambiente y con una corriente de descarga de 400 mA. Se utilizó un flujo de Ar de 9 sccm y para la producción de CrN se activó el nitrógeno con un flujo de 3 sccm. Los tiempos de depósito se ajustaron para producir monocapas de CrN y multicapas a escala nanométrica manteniendo un espesor total de 1 μm y un periodo de 100 nm. A los recubrimientos obtenidos se les determinó su microestructura con icroscopia electrónica de barrido (SEM), la textura y fases cristalinas con difracción de rayos X (XRD) y espectroscopia infrarroja (IR), y la resistencia a la corrosión se evaluó con ensayos de polarización potenciodinámica utilizando una solución de 0,5M H2SO4 y 0,05M KSCN. En general, las multicapas anométricas mejoraron la resistencia a la corrosión de los aceros inoxidables, además se observó que los aceros A36 recubiertos con CrN pueden ser una alternativa para reemplazar a los aceros inoxidables en ambientes ácidos.Los mecanismos de corrosión para los recubrimientos producidos son discutidos en esta investigación.This work was aimed at comparing the corrosion resistance of CrN and CrN/Cr coatings deposited through unbalanced magnetron sputtering (UBM), Cr industrial coatings and epoxy paints. UBM coatings were optimised and produced at room temperature, using 400 mA discharge current. Ar and N2 flow rates were set at 9 standard cubic centimetres per minute (SCCM) and 3 SCCM, respectively. Deposition times were set to produce CrN monolayers and nanometric multilayers having 1 μm total thickness and 100 nm period. Coating icrostructure was determined through scanning electron microscopy as texture and crystalline phases were determined using x-ray diffraction and infrared spectroscopy. Corrosion resistance was studied with anodic polarisation tests using 0.5M H2SO4 and 0.05M KSCN solution. Nanometric multilayers improved stainless steel corrosion resistance and it was observed that coated CrN steel A36 could be an alternative for replacing tainless steel in acid environments.Corrosion mechanisms for the coatings so deposited are discussed

Electrical furnace for producing carbide coatings using the thermoreactive deposition/diffusion technique

In this work, the design of an electrical furnace for producing transition metal-based hard coatings using the thermo-reactive deposition and diffusion (TRD) technique is described. Performance of the system was tested through production of vanadium carbide (VC) and niobium carbide (NbC) coatings on steel AISI D2. X-ray diffraction (XRD) and optical microscopy techniques were used to study phase formation and microstructure, respectively. Hardness was determined by using Knoop microhardness measurements. XRD results showed the presence of VC and NbC, and as MEB results clearly show, the formation of regular thickness coatings. The results obtained allow for assessing that the designed and built furnace fulfills the requirements of the TRD technique for obtaining different types of hard coatings

Multicapas nanoestructuradas de Cr/CrNx como barrera de difusión entre Cu y Si

Esta tesis se enfoca en el crecimiento y la caracterización funcional de multicapas basadas en Cr y CrNx depositadas por técnicas de deposición en fase vapor, con énfasis en el comportamiento como barrera de difusión entre cobre y silicio. Para este propósito se prestó especial atención en sus características de espesor, resistividad, y formación de compuestos a altas temperaturas. Las técnicas de deposición utilizadas para obtener las multicapas fueron la técnica de sputtering con magnetrón desbalanceado D.C. de campos variables y la técnica de sputtering con magnetrón R.F. La primera se utilizó para producir multicapas nanométricas basadas en Cr y CrN mientras que la segunda se utilizó para obtener multicapas basadas en Cr y Cr2N. De esta forma los resultados obtenidos en la tesis se dividen en dos partes: la primera se enfoca en la producción, caracterización y evaluación de las propiedades como barrera de difusión de multicapas basadas en Cr y CrN al variar el grado de desbalanceo del magnetrón utilizado en su producción, y la periodicidad de la multicapa que estuvo en el rango nanométrico. En la segunda parte se evalúan las características de las multicapas basadas en Cr y Cr2N, variando su período de la misma forma en el rango nanométrico. Los resultados obtenidos para las multicapas basadas en Cr y CrN mostraron que tuvieron buen desempeño hasta 600 °C, y la menor resistividad obtenida fue 195 μΩ-cm para la bicapa crecida con el menor desbalanceo del magnetrón. Para el caso de las multicapas basadas en Cr y Cr2N se encontró una temperatura de falla de 900 °C para la bicapa, la cual fue superior a la encontrada en los sistemas basados en CrN. Por otro lado la resistividad de esta bicapa fue 26.2 μΩ-cm, la cual no es sólo menor a la obtenida en las multicapas basadas en CrN sino también menor a las resistividades de las monocapas y multicapas reportadas en la literatura para ser usadas como barrera de difusión en dispositivos electrónicos que utilizan contactos Cu y Si. Estos resultados permiten proponer las bicapas basadas en Cr y Cr2N para ser aplicadas como barrera de difusión en este tipo de dispositivos, ya que cumplen con las características requeridas para este fin: bajo espesor, del orden de los nanómetros, baja difusividad a altas temperaturas y baja resistividad. /Abstract:This thesis is focused on the growth and performance characterization of Cr and CrNx based multilayers using physical vapor deposition techniques, placing special attention on their properties as diffusion barriers between copper and silicon, in order to study their applicability in the integrated circuits manufacturing technology, which uses copper as metallization layer. For this purpose the efforts where focused on their thickness, resistivity and compound formation at high temperatures characteristics. Deposition techniques used to obtain the multilayers were variable field unbalanced magnetron sputtering and magnetron sputtering R.F. The first was used to produce nanometric multilayers based on Cr and CrN and the latter was used to obtain Cr and Cr2N based multilayers. In this way, results obtained in this thesis are divided in two parts: the first one is focused on the production, characterization and evaluation of Cr and CrN based diffusion barrier properties when varying unbalance degree and multilayer period, which was in the nanometric range. The second one evaluates Cr and Cr2N based multilayer characteristics when varying its period in the same way in the nanometric range. Results obtained for Cr and CrN based multilayers showed that they had good performance at 600 °C, and the minor resistivity was found to be 195 μΩ-cm for the bilayer grown with the minor unbalance degree of the magnetron. For the case of Cr and Cr2N based multilayers, the best result was found for the bilayer with failure temperature at 900 °C, which is higher than that found for CrN based multilayers. On the other hand, resistivity in this case was found to be 26.2 μΩ-cm, which is not only minor than that obtained for CrN based multilayers, but also minor to that reported in literature for monolayers and multilayers to be used as diffusion barriers in electronic devices using Cu and Si contacts. These results allow to propose Cr and Cr2N based bilayers to be used as diffusion barriers in this kind of devices, because they fulfill the requirements for this purpose: low thickness, in the range of nanometers, low diffusivity at high temperatures and low resistivity.Doctorad

Electrical properties of cr/crn nano-multilayers produced by the unbalanced magnetron sputtering technique

Chromium nitride (CrN) films have been applied to several steels as protective coatings against wear and corrosion due to their excellent mechanical properties and corrosion resistance, and in the electronic field these films are commonly used due to their low electrical resistivity. However, it has been found that multilayers combining metal/ceramic films could enhance mechanical and electrical properties compared with their monolayer counterparts, due to the higher amount and interaction between interfaces. In this work, Cr/CrN nano-multilayers have been produced through the unbalanced magnetron sputtering technique with three different degrees of unbalance, in order to study the influence of this parameter on electrical properties. Cr/CrN multilayers with approximately 1 μm of total thickness and a bilayer period (Λ) of 200 nm, 100 nm, and 20 nm were produced at room temperature on H13 steel and silicon (100); and their microstructure and electrical properties as a function of the magnetic field were evaluated. The phase formation was characterized through x-ray diffraction, and results presented (111) and (200) preferred orientations for all the multilayers. Cross section images were obtained through scanning electron microscopy and a multilayer structure can be clearly seenPelículas de nitruro de cromo (CrN) se han aplicado como recubrimientos protectores contra el desgaste y la corrosión debido a sus excelentes propiedades mecánicas y alta resistencia a la corrosión, y en el campo electrónico debido a su baja resistividad. Sin embargo, se ha encontrado que las multicapas que combinan películas metal/cerámico podrían mejorar las propiedades en comparación a sus contrapartes en monocapa debido al aumento e interacción entre interfaces. En este trabajo se produjeron nano-multicapas de Cr/CrN a través de la técnica de sputtering con magnetrón desbalanceado con tres grados de desbalanceo diferentes para estudiar la influencia de este parámetro en las propiedades eléctricas. Se crecieron multicapas con un espesor total de aproximadamente 1 μm y un período de bicapa (Λ) de 200 nm, 100 nm y 20 nm. Las multicapas se produjeron a temperatura ambiente sobre acero H13 y silicio (100) y se estudió su microestructura y las propiedades eléctricas en función del campo magnético. La formación de fases se caracterizó a través de Difracción de Rayos X y los resultados muestran las orientaciones (111) y (200) para todas las multicapas. Se obtuvieron imágenes de la sección transversal a través de Microscopía Electrónica de Barrido y los resultados muestran la formación de una estructura en multicap

Unbalanced magnetron sputtering system for producing corrosion resistance multilayer coatings

In this work, an unbalanced magnetron sputtering system which allows for the production of corrosion resistance multilayer coatings is described. The major advantage of this system is that it combines features such as a multi-cathode setup, temperature control, control over the rotation of the sample holder, and the ability to change samples without breaking the vacuum. The system was tested with the production of Cr/CrN nanometric multilayers on AISI stainless steel 304 and silicon (100) substrates and the evaluation of its corrosion resistance. X-ray diffraction (XRD) was used in order to assess the crystalline microstructure and scanning electron microscopy (SEM) was used to characterize multilayer formation. The XRD results show (111) and (200) orientations for CrN multilayer films and the SEM results clearly show the formation of a multilayer structure. Corrosion resistance was evaluated through electrochemical studies and the results show that the Cr/CrN multilayer structure presents lower corrosion current and higher corrosion potential as compared to the stainless steel 304 substrate

Propiedades eléctricas de nano-multicapas de Cr/CrN producidas por la técnica de sputtering con magnétrón desbalanceado / Electrical properties of Cr/CrN nano-multilayers produced by the unbalanced magnetron sputtering technique

Películas de nitruro de cromo (CrN) se han aplicado como recubrimientos protectores contra el desgaste y la corrosión debido a sus excelentes propiedades mecánicas y alta resistencia a la corrosión, y en el campo electrónico debido a su baja resistividad. Sin embargo, se ha encontrado que las multicapas que combinan películas metal/cerámico podrían mejorar las propiedades en comparación a sus contrapartes en monocapa debido al aumento e interacción entre interfaces. En este trabajo se produjeron nano-multicapas de Cr/CrN a través de la técnica de sputtering con magnetrón desbalanceado con tres grados de desbalanceo diferentes para estudiar la influencia de este parámetro en las propiedades eléctricas. Se crecieron multicapas con un espesor total de aproximadamente 1 μm y un período de bicapa (Λ) de 200 nm, 100 nm y 20 nm. Las multicapas se produjeron a temperatura ambiente sobre acero H13 y silicio (100) y se estudió su microestructura y las propiedades eléctricas en función del campo magnético. La formación de fases se caracterizó a través de Difracción de Rayos X y los resultados muestran las orientaciones (111) y (200) para todas las multicapas. Se obtuvieron imágenes de la sección transversal a través de Microscopía Electrónica de Barrido y los resultados muestran la formación de una estructura en multicapas./ Abstract. Chromium nitride (CrN) films have been applied to several steels as protective coatings against wear and corrosion due to their excellent mechanical properties and corrosion resistance, and in the electronic field these films are commonly used due to their low electrical resistivity. However, it has been found that multilayers combining metal/ceramic films could enhance mechanical and electrical properties compared with their monolayer counterparts, due to the higher amount and interaction between interfaces. In this work, Cr/CrN nano-multilayers have been produced through the unbalanced magnetron sputtering technique with three different degrees of unbalance, in order to study the influence of this parameter on electrical properties. Cr/CrN multilayers with approximately 1 μm of total thickness and a bilayer period (Λ) of 200 nm, 100 nm, and 20 nm were produced at room temperature on H13 steel and silicon (100); and their microstructure and electrical properties as a function of the magnetic field were evaluated. The phase formation was characterized through x-ray diffraction, and results presented (111) and (200) preferred orientations for all the multilayers. Cross section images were obtained through scanning electron microscopy and a multilayer structure can be clearly seen

Microstructural evolution and microhardness in a low carbon steel processed by high-pressure torsion

A low-carbon triple-alloyed steel was processed by high-pressure torsion at room temperature for up to 5 turns under a pressure of 6.0 GPa. Microhardness, scanning electron microscopy and X-ray diffraction were used to investigate the hardness and microstructural evolution of the steel. Values of the Vickers microhardness were recorded across the sample diameters. The results show that there is a gradual evolution in both the hardness and the microstructure with increasing numbers of turns. However, the microhardness does not become fully homogeneous across the sample diameter after five turns and there remain significantly lower values in the center of the disk. These results indicate that complete homogeneity across the disks for this steel requires applied pressures higher than 6.0 GPa and/or torsional straining through more than 5 turns

Microstructural evolution and microhardness in a low carbon steel processed by high-pressure torsion

A low-carbon triple-alloyed steel was processed by high-pressure torsion at room temperature for up to 5 turns under a pressure of 6.0 GPa. Microhardness, scanning electron microscopy and X-ray diffraction were used to investigate the hardness and microstructural evolution of the steel. Values of the Vickers microhardness were recorded across the sample diameters. The results show that there is a gradual evolution in both the hardness and the microstructure with increasing numbers of turns. However, the microhardness does not become fully homogeneous across the sample diameter after five turns and there remain significantly lower values in the center of the disk. These results indicate that complete homogeneity across the disks for this steel requires applied pressures higher than 6.0 GPa and/or torsional straining through more than 5 turns