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Over the past seven years, pestalotiopsis has been the main strawberry disease found all over the crops located in the south of Minas Gerais State, Brazil. The leaves of the plants were severely at- tacked by an uncommon fungus in the regional crops, mainly in 2005 and 2006. The non-immediate identification of the microorganism resulted in catastrophic pathogen control processes performed by farmers who, eagerly trying to save their crops ended up using a series of toxic agrochemicals that had been previously purchased for the control of other types of diseases. Due to these events, the present paper aims at identifying the pathogen and put chemical as well as biological products into test that might help control the disease. Results showed that no fungicide under test in the present experiment was able to inhibit the isolate at a 100% rate, even under in vitro conditions. Pathogen identification revealed a fungi known as Pestalotiopsis longisetula.

X-ray diffraction using synchrotron radiation was used for real-time investigation of the phase evolution of Ni/Ti multilayer thin films during annealing. These multilayers were deposited onto Tie6Ale4V substrates by dc magnetron sputtering from pure Ni and Ti targets. The deposition parameters were adjusted in order to obtain a near equiatomic chemical composition and modulation periods (L) below 25 nm. Along the entire thickness of the films, well-defined structures with alternate Ni- and Ti-rich layers are observed, even for L ¼ 4 nm. In this case, a halo characteristic of an amorphous structure is obtained, while for L of 12 and 25 nm the as-deposited thin films are nanocrystalline being possible to identify the (111) Ni and (002) Ti diffraction peaks. The nanolayered structure vanishes during annealing due to interdiffusion followed by reaction. The reaction between Ni and Ti to produce NiTi in the cubic B2 structure occurs in a short delay of time and within a narrow temperature range. For L of 25, 12 and 4 nm, the reaction temperature is close to 320, 350 and 385 C, respectively. For higher temperatures, in addition to the austenitic phase, the NiTi2 phase is identified. The diffusion of Ti from the substrate and Ni towards the substrate could favour the precipitation of NiTi2.

Nickel-Titanium (Ni-Ti) thin film shape memory alloys (SMAs) have been widely projected as a novel material, which can be utilized in microdevices. Characterization of their physical properties and its correlation with phase transformations has been a challenging issue. In the present study, X-ray beam diffraction has been utilised to obtain the structural information at different temperatures while cooling. Simultaneously, electrical resistivity (ER) was measured in the phase transformation temperature range. The variation of ER and integral area of the individual diffraction peaks of the different phases as a function of temperature have been compared. A mismatch between the conventional interpretation of ER variation and the results of the XRD data has been clearly identified.

The shape memory effect and superelasticity of Ni-Ti (Nitinol) make it very attractive for biomedical applications. The Ni-Ti alloy (~ 50.4 at.% Ni) selected for this work is austenitic (superelastic) at body temperature. In the frame of the AIM-74 and SPIRIT-77 projects, plasma immersion ion implantation (PIII) has been employed to modify and improve the superficial region of the alloy. The formation of titanium oxynitride (TiNxOy) was achieved by ion implantation of nitrogen. A Ti-rich oxide layer was obtained during the experiments carried out with oxygen. Thus, the parameters to obtain a Ni-depleted surface, which serves as a barrier to out-diffusion of Ni ions from the bulk material, have been successfully established. Furthermore, nanostructured Ni-Ti surfaces have been produced. Synchrotron radiation-based X-ray diffraction data acquired in transmission mode show that the PIII technique only changes the structure of the Ni-Ti alloy top layer preserving superelastic behaviour at body temperature (PIII experiments carried out without intentional heating of the substrate holder). Techniques like thermal oxidation and nitriding also lead to an improved corrosion resistance and Ni-depleted Ni-Ti surface but require high processing temperatures leading to modification of the phase transformation characteristics and loss of specific mechanical properties.

In-situ X-ray scattering measurements were carried out during Ni-Ti shape memory alloy film processing at the Rossendorf Beamline (BM20-ESRF). The experiments performed with a two-magnetron sputter deposition chamber mounted into the six-circle diffractometer of the beamline enabled us to identify the different steps of the structural evolution during deposition with a set of parameters as well as to evaluate the effect of changing parameters (Ti target power) during film growth. The results show that the type of substrate plays an important role for the preferential orientation of sputtered Ni-Ti films. Amorphous SiO2 and TiN buffer layers were used to successfully control their crystallographic orientations. The deposition conditions leading to films mainly containing grains with (100) or (110) planes of the B2 phase parallel to the film surface are presented. The control of texture is an important achievement since it has a strong influence on the extent of the strain recovery of the Ni-Ti films. The deposition of graded Ni-Ti films by deliberately changing the Ti:Ni ratio, thereby altering microstructure and transformation temperatures across the film thickness, provided significant data for the optimisation of the deposition parameters in order to fabricate films with a “two-way” actuation (films with a combination of superelasticity and shape memory characteristics). This is a plus for the miniaturization of Ni–Ti films based devices in the field of micro-electro-mechanical systems since no consideration has to be paid to a resetting spring.

The plasma immersion ion implantation (PIII) technique was used to modify and improve the surface of a Ni-Ti alloy (» 50.2 at.% Ni) for biomedical applications. The main goal has been the formation of a Ni-depleted surface, which should serve as a barrier to out-diffusion of Ni ions from the bulk material. Ion implantation of oxygen was carried out. The depth profiles of the elemental distribution in the alloy surface region, obtained by Auger electron spectroscopy (AES), confirm the formation of a Ti-rich oxide layer. The working plan also comprised ion implantation of nitrogen. In this case, the formation of titanium oxynitride (TiNxOy) was observed. The AES depth profiles clearly show a Ni-depleted fraction for experiments performed with 40 keV.

The enormous elasticity of Ni-Ti is becoming integral to the design of a variety of new medical products. The wide spectrum of application in implantology imposes special requirements on the biocompatibility of Ni-Ti. The biological response to implant materials is a property directly related to their surface conditions and an optimum surface layer is thus desired. The plasma-immersion ion implantation (PIII) technique was used to modify and improve the surface of a Ni-Ti alloy (~ 50.2 at.% Ni, superelastic at body temperature) for biomedical applications. The main goal has been the formation of a Ni-depleted surface, which should serve as a barrier to out-diffusion of Ni ions from the bulk material. Ion implantation of oxygen was carried out. The depth profiles of the elemental distribution in the alloy surface region, obtained by Auger electron spectroscopy (AES), confirm the formation of a Ti-rich oxide layer. The working plan also comprised ion implantation of nitrogen. In this case, the formation of titanium oxynitride (TiNxOy) was observed. The AES depth profiles clearly show a Ni-depleted fraction for experiments performed with 40 keV. The deposition of a coating by a PVD technique would have disadvantages due to the interface between the coating and the bulk (lower adhesion). PIII creates a graded interface between the modified surface and the bulk. Techniques like thermal oxidation and nitriding could also lead to an improved corrosion resistance and Ni-depleted Ni-Ti surface. However, the high temperature necessary for the experimental procedure would lead to modification of the phase transformation characteristics and loss of specific mechanical properties of the alloy. Heat treatments tests performed at temperatures above 350ºC led to a shift of the transformation temperatures of the Ni-Ti alloy used in this work. Moreover, the R-phase is then present at body temperature, which is not the case for Ni-Ti samples modified by the PIII technique. This technique only changes the properties of the Ni-Ti alloy top layer.

Near equiatomic Ni–Ti films have been deposited by magnetron co-sputtering on TiN films with a topmost layer formed by b111N oriented grains (TiN/SiO2/Si(100) substrate) in a chamber installed at a synchrotron radiation beamline. In-situ X-ray diffraction during Ni–Ti film growth and their complementary ex-situ characterization by Auger electron spectroscopy, scanning electron microscopy and electrical resistivity measurements during temperature cycling have allowed us to establish a relationship between the structure and processing parameters. A preferential development of b110N oriented grains of the B2 phase since the beginning of the deposition has been observed (without and with the application of a substrate bias voltage of −45 and −90 V). The biaxial stress state is considerably influenced by the energy of the bombarding ions, which is dependent on the substrate bias voltage value applied during the growth of the Ni–Ti film. Furthermore, the present work reveals that the control of the energy of the bombarding ions is a promising tool to vary the transformation characteristics of Ni–Ti films, as shown by electrical resistivity measurements during temperature cycling. The in-situ study of the structural evolution of the growing Ni–Ti film as a consequence of changing the Ti:Ni ratio during deposition (on a TiNb111N layer) has also been performed. The preferential growth of b110N oriented grains of the Ni–Ti B2 phase has been as well observed despite the precipitation of Ti2Ni during the deposition of a Ti-rich Ni–Ti film fraction. Functionally graded Ni–Ti films should lead to an intrinsic “twoway” shape memory effect which is a plus for the miniaturization of Ni–Ti films based devices in the field of micro-electro-mechanical systems.

ZnO:SiO2 films are intensively investigated for optical and electronic applications. Additionally, porous ZnO:SiO2 films are of great interest as catalyst and gas-sensing materials. The sol–gel method is an efficient and low-cost process for the deposition of meso- and microporous silica-based films. The present paper studies the effect of the withdrawal speed on the microstructure and optical properties of mesoporous ZnO:SiO2 films obtained by the sol–gel method. The morphology of the films was investigated by atomic force microscopy and the overall structure was studied by X-ray diffraction. The structure and size of the zinc oxide nanoparticles embedded in the silica matrix were investigated in more detail by transmission electron microscopy. These techniques showed ZnO:SiO2 films with crack-free mesoporous morphology and highly efficient embedding of ZnO nanoparticles with (100) preferred orientation. Furthermore, the optical transmittance (in the visible and near infrared regions) and the optical band gap value were observed to vary with withdrawal speed. It is shown that ZnO:SiO2 nanocomposites films which possess ZnO particles exhibiting a (100) orientation, with possible special applications in non-linear optics, could be prepared by the low-temperature crystallization sol–gel method.

The study of Ni-Ti shape memory alloy films is of great technological interest for applications in the field of microengineering. They can work as sensors and actuators at the same time. However, there are still important issues unresolved like formation of film texture and its control. Films exhibiting the two-way shape memory effect are also required. A better understanding of the underlying growth mechanisms and their microstructural development requires sophisticated in-situ techniques. A two-magnetron sputter deposition chamber mounted into the six-circle diffractometer of the Rossendorf Beamline at the European Synchrotron Radiation Facility has been used for the processing of the Ni-Ti films. The in-situ x-ray diffraction studies enabled us to identify the different steps of the structural evolution during deposition with a set of parameters as well as to evaluate the effect of changing parameters (Ti target power) during film growth. It has been found that the type of substrate plays an important role for the preferential orientation of sputtered Ni-Ti films. In some cases they exhibit a pronounced depth dependence of their preferential orientations. Amorphous SiO2 and TiN buffer layers have been used to successfully control their crystallographic orientations. This is an important achievement since the texture has a strong influence on the extent of the strain recovery of the Ni-Ti films. The deposition conditions leading to films mainly containing grains with (100) or (110) planes of the B2 phase parallel to the film surface are presented. The deposition of graded Ni-Ti films by changing deliberately the Ti:Ni ratio, thereby altering microstructure and transformation temperatures across the film thickness, has also been performed. The aim has been the optimization of the deposition parameters in order to fabricate films with a “two-way” actuation (films with a combination of superelasticity and shape memory characteristics). It will lead to the development of smaller devices due to an optimal design of microdevices regarding size and weight (i.e., no consideration has to be paid to a resetting spring).

Near equiatomic and Ti-rich Ni–Ti polycrystalline films have been deposited by magnetron co-sputtering using a chamber installed at a synchrotron radiation beamline. The in situ X-ray diffraction studies enabled the identification of different steps of the structural evolution during film processing. The depositions on a 140 nm amorphous SiO2 buffer layer heated at 520°C (without applying bias voltage, Vb, to the substrate) led to a preferential growth of oriented grains of the Ni–Ti B2 phase from the beginning of film growth until the end of the deposition. Films exhibiting a preferential growthof oriented grains of the Ni–Ti B2 phase from the beginning of the deposition were obtained (without and with a Vb of - 45 V) by using a TiN coating with a topmost layer formed by oriented grains. Those trends have been observed for the growth of near equiatomic (~50.0 at.% Ti–Ni) and Ti-rich (~50.8 at.% Ti–Ni) Ni–Ti films. Additionally, an ion gun had been commissioned, which allows ion bombardment during sputter deposition or post-deposition ion irradiation. In this first series of experiments, a Ni–Ti film was irradiated with He ions after deposition (without exposing the film to the atmosphere, i.e., avoiding surface oxide formation), thus modifying deliberately the microstructure of the film locally.

The deposition of Ni-Ti films with definite stoichiometry and high purity remains still a challenge. Furthermore, important issues like the formation of film texture and its control are not yet resolved. Near equiatomic (~ 50.0 at.% Ti¨CNi) and Ti-rich (~ 50.8 at.% Ti¨CNi) Ni-Ti polycrystalline films (thickness values ¡Ü 800 nm) have been deposited by magnetron co-sputtering using a chamber installed into the six-circle diffractometer of the Rossendorf beamline at the European Synchrotron Radiation Facility. The in-situ X-ray diffraction studies enabled the identification of different steps of the structural evolution during films processing. Films exhibiting a (100) preferential orientation for the B2 phase have been successfully produced. A continuous increase of the B2(200) diffraction peak intensity has been observed for depositions on a 140 nm amorphous SiO2 buffer layer heated at 520¡ãC (without substrate bias voltage, Vb). A (100) texture has been observed for films as thick as 800 nm. Films deposited without and with Vb on a TiN coating with a topmost layer formed by oriented grains have shown a preferential growth of oriented grains of the B2 phase from the beginning of the deposition. Those trends have been observed for the growth of near equiatomic and Ti-rich films.

The plasma-immersion ion implantation (PIII) technique was used to modify and improve the surface of a Ni-Ti alloy (» 50.2 at.% Ni) for biomedical applications. The main goal has been the formation of a Ni-depleted surface, which should serve as a barrier to out-diffusion of Ni ions from the bulk material. Ion implantation of oxygen was carried out. The depth profiles of the elemental distribution in the alloy surface region, obtained by Auger electron spectroscopy (AES), confirm the formation of a Ti-rich oxide layer. The working plan also comprised ion implantation of nitrogen. In this case, the formation of titanium oxynitride (TiNxOy) was observed. The AES depth profiles clearly show a Ni-depleted fraction for experiments performed with 40 keV.

Due to the high sensitivity of Ni–Ti films to environmental changes, e.g. thermal, and/or to stress, they are ideal materials for applications on micro-sensors. It was aimed to obtain Ni–Ti films exhibiting the beginning of the B25R-phase transformation between room temperature (RT) and 0°C. Thus, films with a slightly Ni-rich composition were prepared by sputtering, without intentional heating of the substrate. The Ni–Ti films were deposited on an Si3N4 intermediate layer previously deposited on naturally oxidized Si(100). The crystallization behaviour of the samples (at a constant temperature of 430°C) was studied by X-ray diffraction in grazing incidence geometry off-plane (GIXD) at a synchrotron-radiation beamline. The GIXD patterns obtained during the annealing process of the Ni–Ti polycrystalline films revealed mainly an austenitic structure (B2 phase) and the precipitation of Ni4Ti3. The results have also shown that the presence of an intermediate layer of Si3N4 enhances the crystallization process of the Ni–Ti sputtered films when compared to the films deposited directly on single-crystal Si (with native oxide). The phase transformation behaviour of the Ni–Ti film on Si3N4 was evaluated by XRD in off-plane Bragg–Brentano geometry during cooling (RT-> -40°C) and heating (-40°C ->RT). It has been observed that a high fraction of the Ni–Ti film is already transformed to R-phase at 9°C (austenitic at RT), as well as a very small temperature hysteresis for the B25R-phase transformation. After the characterization described above, the film was removed from the substrate. The free-standing film showed a pronounced ‘‘two-way’’ shape memory effect (SME). In the austenitic state the film presents a flat shape. During cooling, by reducing its distance from ice cubes (i.e., decreasing the surrounding temperature), the film starts bending exhibiting a final curled shape (yet without touching the ice). On heating it recovers its flat shape. The authors attribute the nature of this ‘‘two-way’’ SME to the Ni4Ti3 precipitates that formed during the heat treatment.

Ni-Ti SMA films are attractive materials for microfabrication and integration in micro-miniature systems composed of mechanical elements, actuators, sensors and electronics made on one chip. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. It is essential to identify and control their preferential orientation since it is a crucial factor in determining the shape memory behaviour. Widening the scope of previous experiments concerning the influence of the deposition parameters on the Ni-Ti films structure, the incorporation of a TiN intermediate layer was tested. Here, it is established a clear relationship between the TiN substrates and Ni-Ti texture development (B2 phase) and it is shown that the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation behaviour. The influence of a substrate bias voltage on the preferential orientation of the B2 phase and transformation temperatures is as well revealed.

The metal (Ni) contamination on crystallized silicon obtained by metal induced crystallizaion (MIC) was estimated by Spectroscopic Ellipsometry (SE) using a new simulation approach. The method employs the addition of Ni as reference for a Bruggeman Effektive Medium Approximation (BEMA) to simulate the optical response of the crystallized silicon. Samples with different initial metal/silicon ratios were annealed and crystallized. Besides determining thickness, surface roughness and crystalline fraction, this new approach using SE has shown to be sensible to changes on the initial metal thickness used on the crystallization process being able of determining in a quick and non destructive way the Ni concentration inside MIC poly-Si films. The effectiveness of the obtained results was confirmed by RBS. An accurate determination of the initial Ni thickness that is deposited onto the amorphous silicon prior to crystallization is not possible using a quartz oscillator due to the very low quantity of evaporated materials. A better relation between defferent metal amounts present inside the crystallized films can be obtained by integratingthe Ni distribution in the RBS spectra. The obtained values are proportional to the Ni volume fraction determined by SE ellipsometry proves to be sensible to a metal volume fraction as low as 0.24%, corresponding to an initial Ni average thickness of 0.05 nm.

The technological importance of thin films has led to an unabated interest in the detailed characterization of their structure, morphology, and their interfaces. A real understanding of the underlying growth mechanisms and their microstructural development requires sophisticated in situ techniques. X-ray diffraction with high-brilliance beams is such a powerful technique, as it is demonstrated here for the study of Ni-Ti films. Numerous examples of investigations on Ni-Ti films can be found in the literature but it has been reported that the deposition of Ni-Ti films with definite stoichiometry and high purity remains a challenge, and important issues like formation of film texture and its control are still unresolved. It is essential to identify and control their preferential orientation since it is a crucial factor in determining the shape memory behaviour. Widening the scope of our previous experiments concerning the influence of the deposition parameters on the structure of the Ni-Ti films, the incorporation of a TiN buffer layer has been tested. Here, it is established a clear relationship between the TiN substrates and Ni-Ti texture development (B2 phase) and it is shown that the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation behaviour. The influence of a substrate bias voltage on the preferential orientation of the B2 phase and transformation temperatures is as well revealed. A lower biaxial stress state and lower phase transformation temperatures have been observed for the films deposited with bias (-45 and -90V). Therefore, the control of the energy of the bombarding ions could be used as a tool for the manipulation of the transformation temperatures.

The preferential orientation of Ni-Ti thin films is a crucial factor in determining the shape memory behavior. The texture has a strong influence on the extent of the strain recovery. The relationship between structure and deposition parameters is of extreme importance for future device applications. Our approach is in-situ x-ray diffraction during deposition carried out in a process chamber installed at a synchrotron radiation beamline. Near-equiatomic films were co-sputtered from Ni-Ti and Ti targets. Substrate type and bias voltage play an important role for the preferred orientation. On naturally oxidized Si(100) substrates the NiTi B2 phase starts by stacking onto (h00) planes and then changes to (110) fiber texture with increasing film thickness. For thermally oxidized Si(100) substrates, this cross-over is only observed when a bias voltage is applied. The experiments were supplemented by ex-situ transmission electron microscopy and Auger Electron Spectroscopy allowing an additional deeper insight into the film/substrate interface.

Ni-Ti thin films have been recognized as promising and high performance materials in the field of microelectromechanical system applications. However, important issues like formation of film texture and its control are still unresolved. Widening the scope of previous experiments concerning the influence of the deposition parameters on the Ni-Ti films structure, here we show how different crystallographic orientations can be obtained by changing the substrate type. The growth of near-equiatomic Ni-Ti films, deposited by magnetron co-sputtering from Ni-Ti and Ti targets on heated substrates ( 470C), has been studied in situ by x-ray diffraction at a synchrotron radiation beamline. As mentioned in other studies for depositions on Si(100), a (110) fiber texture is observed for the B2 phase. However, a preferential stacking of (100) planes of the B2 phase parallel to the film surface was observed when using a MgO(100) substrate. The preferential orientation of B2(100) // MgO(100) was very strong and was kept as such until the end of the deposition, which lasted for 2 hours (~ 900 nm). Ni-Ti films were also deposited on a TiN layer (~ 15 nm) previously deposited on top of a SiO2/Si(100) substrate. In this case, a crossover from (110) oriented grains dominating at small thicknesses, to (211) oriented grains taking over at larger thicknesses was observed. These are promising results concerning the manipulation of the crystallographic orientations of Ni-Ti thin films, since the texture has a strong influence on the extent of the strain recovery.

In-situ x-ray diffraction (XRD) during the growth of Ni-Ti thin films was chosen in order to investigate their texture development using a deposition chamber installed at a synchrotron radiation beamline. Near-equiatomic films were co-sputtered from Ni-Ti and Ti targets. The texture evolution during deposition is clearly affected by the substrate type and the ion bombardment of the growing film. On naturally oxidized Si(100) substrates the NiTi B2 phase starts by stacking onto (h00) planes, and as the thickness increases evolves into a (110) fiber texture. For the deposition on thermally oxidized Si(100) substrates, this pronounced cross-over is only observed when a substrate bias voltage (-45 V) is applied. The oxide layer plays an important role on the development of the (100) orientation of the B2 phase during deposition on heated substrates (≈ 470ºC). If this layer is not thick enough (naturally oxidized Si substrate) or if a bias voltage is applied, a cross-over and further development of the (110) fiber texture is observed,which is considered as an orientation that minimizes surface energies. Electrical resistivity measurements showed different behaviour during phase transformation for the NiTi film deposited on thermally oxidized Si without bias and those on thermally oxidized Si(100) with bias and on naturally oxidized Si(100) without bias. This is related to stresses resultant from the fact that the NiTi films are attached to the substrates as well as with the existence of distinct textures.

The aim of the present work is to investigate the textural evolution in high-temperature phase (austenite – B2) of Ti-rich NiTi (Ni–51at%Ti) shape memory alloys (SMA). The alloy was subjected to different thermomechanical treatments involving various heat treatments and cold rollings (10% and 40%). The qualitative texture analysis was performed at BM20 (ROBL-CRG) of the European Synchrotron Research Facility (ESRF) using in-situ high-temperature X-ray diffraction (XRD) with a wavelength of 0.154 nm. In-situ high-temperature texture determination has been carried out for the first time for Ni–Ti alloys, by annealing at different temperatures up to 800 °C under a vacuum better than 1e-4 Pa. The discussion highlights the evolution of texture during annealing at high temperatures and the change in the coherency domain size and microstrain.

Thin films of the MAX phase Ti2AlN were epitaxially grown onto single crystal MgO(111) and MgO(100) substrates by DC reactive magnetron co sputtering from Ti and Al targets in an Ar/N2 gas mixture at a temperature of 690 °C. To promote the nucleation of the MAX phase, an fcc (Ti0.63Al0.37)N seed layer was deposited before changing to Ti2AlN growth parameters. The nucleation processes have been studied by real time in situ specular x ray reflectivity. Independent of substrate orientation, the seed layer shows no roughening until its final thickness of approximately 100 Å indicating pseudomorphic layer by layer growth within the descriptive step-flow growth model of Kodambaka et al. [1]. The MAX phase shows heteroepitaxial layer by layer growth on MgO(111), with increased surface roughening up to approximately 200 Å, whereas on MgO(100) the growth mode changes to Volmer Weber type already after three monolayers. X ray scattering in Bragg Brentano geometry of the final, approximately 1000 Å thick, Ti2AlN film reveals lattice parameters of c = 13.463 Å and a = 2.976 Å on the MgO(111) substrate and c = 13.740 Å and a = 2.224 Å on the MgO(100) substrate. From ex situ pole figure measurements the epitaxial relationship between film and substrate lattice was determined to be MgO{111} // Ti2AlN{101‾2}, regardless of the substrate orientation. This tilted, non basal plane growth leads to a threefold grain orientation of Ti2AlN along the MgO directions and a polycrystalline morphology, which is also confirmed by cross sectional transmission electron microscopy. The growth can be assumed to take place in a step-flow mode, i.e. emerging steps on the high surface free energy (0001) plane where adatoms come to rest after diffusion along A-facets, irrespective of epitaxial relationship.

Shape Memory Alloy (SMA) Ni-Ti thin films have attracted much interest as functional and smart materials due to their unique properties. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. In this study, near-equiatomic films were obtained by co-sputtering from Ni-Ti and Ti targets in a process chamber installed at a synchrotron radiation beamline. In-situ x-ray diffraction during the growth of these films allowed establishing a relationship between structure and deposition parameters. The effect of a TiN layer deposited on top of the SiO2/Si(100) substrate prior to the deposition of the Ni-Ti films was analysed. These experiments show that TiN acts not only as a diffusion barrier, but also induces different crystallographic orientations. A TiN layer with ~ 215 nm thickness induces the preferential growth of (110) planes of the Ni-Ti B2 phase parallel to the substrate from the beginning of the deposition with a constant growth rate during the whole deposition. For a TiN thickness of ~ 15 nm, the diffraction peak B2(110) also appears from the beginning of the deposition but much less intense. In this latter case, the B2(211) peak was also detected having observed a crossover from oriented grains dominating at small thicknesses, to oriented grains taking over at larger thicknesses. The same orientations and similar intensities were observed for a Ni-Ti film deposited on a TiN layer with ~ 80 nm.

Anisotropy of the shape recovery associated with shape memory effect strongly depends on the type of preferential orientation, that is present, as well as the ‘strength’ of the texture. In the present paper, we report the results obtained by the in-situ study of texture evolution during the annealing process in Ti-rich Ni-Ti Shape Memory Alloys (SMAs) with different thermal and mechanical histories. For this purpose, a Be-dome furnace installed into a 6-circle goniometer at the BM20 beamline (ROBL-CRG) at the ESRF (Grenoble) has been used. It is shown that there is a significant change in the preferential orientation of B2 phase, with the change in microstrain/coherence domain size, as a function of annealing temperature. This effect is also observed in the B19’ phase after cooling. The alpha-fiber II (austenite texture - ||RD ({111}-{110}) was present in the as-received alloy, but only up to 400ºC. The evolution of {111} austenite texture component is quite clear for annealing temperatures above 400ºC.

This work focuses on the role of the native oxide layer (SiO2) on the nickel (Ni)-assisted crystallization of amorphous silicon (a-Si). In some samples, the native oxide was removed using a HF-diluted solution before Ni layers with 0.5 nm be deposited on a-Si. The results show that the presence of a thin SiO2 layer of about 3 nm between the a-Si and the Ni delays the crystallization process. Ellipsometry data show that, after annealing for 5 h at 500 °C, the HF-cleaned sample presents a crystalline fraction of 88%, while the one with the native oxide has only 35%. This difference disappears after 20 h where both samples present similar crystalline fraction. These facts are also reflected on the film's electrical properties, where the activation energy for samples annealed for 5 h rises from 0.42 eV to 0.55 eV, when the oxide layer is removed. After 20 h and 30 h, the activation energy is around 0.55 eV for both kinds of samples, meaning that films with similar electrical properties are now obtained. However, the XRD data suggest the presence of some structural differences attributed to slight differences on the crystallization process.

Ni-Ti thin films are promising high performance materials in the field of micro-electro-mechanical system (MEMS) applications. Their preferential orientation is a crucial factor in determining the shape memory behavior since it has a strong influence on the extent of the strain recovery. The relationship between structure and deposition parameters is of extreme importance for future device applications. Our approach is in-situ x-ray diffraction during deposition carried out in a process chamber installed at a synchrotron radiation beamline. Near-equiatomic films (800nm) were co-sputtered from Ni-Ti and Ti targets on heated substrates (~470C) without applying a substrate bias voltage. The texture evolution during deposition is clearly affected by the substrate type. On naturally oxidized Si(100) substrates the Ni-Ti B2 phase starts by stacking onto (h00) planes, and, as the thickness increases, evolves to a (110) fiber texture. An initial significant change of the lattice parameter, as calculated from d(200) , is observed and its tendency for stabilization is coincident with the deposition time where the preferential stacking of B2 phase on (110) planes is starting. For the deposition on thermally oxidized Si(100) there is a strong preferential stacking on (h00) planes of B2 leading to a (100) fiber texture. The measured lattice constants do not exhibit such a strong initial variation as for the sample deposited on naturally oxidized Si(100) substrate, but a continuous slight decrease of this value is perceptible. Ni-Ti films were also deposited on top of a TiN buffer layer. There is a preferential growth of oriented grains of the Ni-Ti B2 phase [ grains are defined as grains with a plane from the {hkl} family parallel to the film surface] from the beginning of the deposition, with a constant growth rate during the whole deposition for a Ni-Ti film deposited on TiN with a topmost layer formed mainly by oriented grains. The Ni-Ti films deposited on top of a TiN layer where a dominating orientation could not be identified (primarily and oriented grains nucleate and grow) exhibit a different behavior. In this case oriented grains of the Ni-Ti B2 phase dominate at small thicknesses while oriented grains take over at larger thicknesses. The decrease of the lattice parameter suggests that the films experience compressive stress which is significantly relaxed with increasing film thickness.

A sputter deposition hamber inserted into the six-circle Huber diffractometer of the materials research station of the ROssendorf BeamLine (ROBL-CRG) at ESRF allowed to perform in-situ experiments during film growth of Ni-Ti. It is equipped with Kapton windows for X-Ray Diffraction (XRD) and specular Reflectivity (XRR) measurements. By following in situ the evolution of the structure of the growing film, we reveal intermediate “states” which cannot be seen/revealed ex situ , because those states ocurred only during the growth but were no longer visible after deposition. Vertical Bragg-Brentano large-angle scattering geometry was employed to study the different trends of structural transformations taking place during deposition. Ni-Ti films exhibiting a non-uniform phase content across the film thickness could be produced by varying the power of co-sputtering Ni-Ti plus Ti. A significant decrease of IB2{110}/IB2{200} was observed when a bias of -45 V was applied.

Shape Memory Alloy (SMA) NiTi thin films have attracted much interest as functional and smart materials due to their unique properties. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. For microelectromechanical systems (MEMS) integration, there is a need for an electrically and thermally insulating or sacrificial layer like poly-Si. In the present study, NiTi thin films have been prepared by d.c. magnetron sputtering on Si(100) and poly-Si/Si(100) substrates to elucidate the substrate influence on the crystallization of these films. Following the structural development of the films during crystallization (at a constant temperature of 430 ºC) by GIXD, is was observed that the crystallization process is significantly enhanced for low target/substrate distances of 4 cm instead of 7 cm for Si(100) substrates. The presence of an intermediate layer of poly-Si furthermore drastically enhances the crystallization process. In-situ XRD during the growth of Ni-Ti thin films was chosen in order to investigate their texture development using a deposition chamber installed at ROBL. Near-equiatomic films were obtained by co-sputtering from Ni-Ti and Ti targets. The texture evolution during deposition is clearly affected by the substrate type and the ion bombardment of the growing film. On naturally oxidized Si(100) substrates the NiTi B2 phase starts by stacking onto (h00) planes, and as the thickness increases evolves into a (110) fiber texture. This pronounced cross-over is only observed when a substrate bias voltage (-45 V) is applied for the deposition on thermally oxidized Si(100) substrates. The oxide layer plays an important role on the development of the (100) orientation of the B2 phase during deposition on heated substrates (~ 470ºC). The effect of a TiN layer deposited on top of the SiO2/Si(100) substrate prior to the deposition of the NiTi films was also analysed. These experiments have shown that TiN acts not only as a diffusion barrier, but also induces different crystallographic orientations. These are promising results concerning the manipulation of the crystallographic orientations of NiTi thin films, since the texture has a strong influence on the extent of the strain recovery.

Ni-Ti thin films as-sputtered are amorphous if the substrate is not intentionally heated during deposition. Therefore, these films have to be heat-treated to induce crystallization in order to exhibit the shape memory effect. Several films have been prepared by dc magnetron sputtering and then studied concerning the influence of the type of substrate (single crystal Si, polycrystalline Si) on the crystallization kinetics and the final structure. The structural development of the films during crystallization (at a constant temperature of 430°C) has been studied by X-ray diffraction in grazing incidence geometry (GID) off-plane at a synchrotron radiation beamline. These experiments allow to establish a correlation between the deposition conditions and the kinetics of crystallization. For films deposited at an electrode distance of 70 mm on a Si(100) substrate, a longer crystallization time is needed compared with films obtained at 40 mm, for otherwise fixed deposition parameters. The analysis of the nucleation kinetics by using the Kolmogorov-Johson-Mehl-Avrami equation lead to exponents between 2.6 and 3. The presence of an intermediate layer of poly-Si drastically enhances the crystallization process. Additionally, ex-situ annealing of identical samples at 500°C during 1 hour and complementary characterization of the structure and morphology of the films by Cross-sectional Transmission Electron Microscopy (XTEM) and Selected Area Electron Diffraction (SAED) were performed. The temperature dependence of the electrical resistivity was measured, identifying the phase transformation temperature ranges. An increase of the overall resistivity with the precipitation of Ni4Ti3 has been detected. Results obtained by X-ray reflectometry (XRR) and GID suggest that during crystallization excess nickel is driven into an amorphous region ahead of the crystal/amorphous interface, thus leading to a higher concentration of Ni at the surface and further precipitation of Ni4Ti3. t the shape memory effect. Several films have been prepared by dc magnetron sputtering and then studied concerning the influence of the type of substrate (single crystal Si, polycrystalline Si) on the crystallization kinetics and the final structure. The structural development of the films during crystallization (at a constant temperature of 430°C) has been studied by X-ray diffraction in grazing incidence geometry (GID) off-plane at a synchrotron radiation beamline. These experiments allow to establish a correlation between the deposition conditions and the kinetics of crystallization. For films deposited at an electrode distance of 70 mm on a Si(100) substrate, a longer crystallization time is needed compared with films obtained at 40 mm, for otherwise fixed deposition parameters. The analysis of the nucleation kinetics by using the Kolmogorov-Johson-Mehl-Avrami equation lead to exponents between 2.6 and 3. The presence of an intermediate layer of poly-Si drastically enhances the crystallization process. Additionally, ex-situ annealing of identical samples at 500°C during 1 hour and complementary characterization of the structure and morphology of the films by Cross-sectional Transmission Electron Microscopy (XTEM) and Selected Area Electron Diffraction (SAED) were performed. The temperature dependence of the electrical resistivity was measured, identifying the phase transformation temperature ranges. An increase of the overall resistivity with the precipitation of Ni4Ti3 has been detected. Results obtained by X-ray reflectometry (XRR) and GID suggest that during crystallization excess nickel is driven into an amorphous region ahead of the crystal/amorphous interface, thus leading to a higher concentration of Ni at the surface and further precipitation of Ni4Ti3.

The aim of the present experiment was to analyse the structural evolution during annealing of Nickel-Titanium (Ni-Ti) SMA subjected to different thermomechanical treatments. As structural evolutions are accompanied by the changes in preferential orientations, pole figures were employed to study the in-situ conditions.

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