Deposition and heat treatment of CuAlNi shape memory thin films

CuAlNi thin films were fabricated by magnetron sputtering process. After heat treatment, the thin films presented a shape memory effect. Calowear method was used to measure the thickness of the thin films. SEM, XRD and TEM were used to characterize the thin films. The phase transformation in the thin films was examined by DSC. The deposition rate increased with increasing sputtering power and decreased with increasing Ar pressure. Compared to the composition of the target, both the content of Al and the content of Ni increased a little. The sputtering conditions had little influence on the content of Ni. The content of Al varied slightly with sputtering power, while decreased with increasing Ar pressure. The deposited thin films were columnar. The grain size was very fine. The phases were α‐Cu and α₂. After heat treatment at 800 ^oC/ 60 min + 300 ^oC/ 60 min in vacuum, CuAlNi shape memory thin films were obtained. The phase in the heat‐treated thin films was β₁’ martensite. Martensite transformation was observed and a two‐way shape memory effect could be shown.     

Nitrogen doping of SiC thin films deposited by RF magnetron sputtering

Silicon carbide thin films (Si _x C _y ) were deposited in a RF (13.56 MHz) magnetron sputtering system using a sintered SiC target (99.5% purity). In situ doping was achieved by introducing nitrogen into the electric discharge during the growth process of the films. The N₂/Ar flow ratio was adjusted by varying the N₂ flow rate and maintaining constant the Ar flow rate. The structure, composition and bonds formed in the nitrogen-doped Si _x C _y thin films were investigated by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), Raman spectroscopy and Fourier transform infrared spectrometry (FTIR) techniques. RBS results indicate that the carbon content in the film decreases as the N₂/Ar flow ratio increases. Raman spectra clearly reveal that the deposited nitrogen-doped SiC films are amorphous and exhibited C–C bonds corresponding to D and G bands. After thermal annealing, the films present structural modifications that were identified by XRD, Raman and FTIR analyses.     

Synthesis of c-axis oriented AlN thin films on different substrates: A review

Highly c-axis oriented AlN thin films have been deposited by reactive sputtering on different substrates. The crystallographic properties of layered film structures consisting of a piezoelectric layer, aluminum nitride (AlN), synthesized on a variety of substrates, have been examined. Aluminum nitride thin films have been deposited by reactive pulsed-DC magnetron sputtering using an aluminum target in an Ar/N₂ gas mixture. The influence of the most critical deposition parameters on the AlN thin film crystallography has been investigated by means of X-ray diffraction (XRD) analysis of the rocking curve Full-Width at Half Maximum (FWHM) of the AlN-(0 0 0 2) peak. The relationship between the substrate, the synthesis parameters and the crystallographic orientation of the AlN thin films is discussed. A guide is provided showing how to optimize these conditions to obtain highly c-axis oriented AlN thin films on substrates of different nature.     

Effect of deposition ambient on structural and optical properties of Mg<Subscript>x</Subscript>Zn<Subscript>1−x</Subscript>O alloy thin films grown by RF sputtering

Mg_xZn_1−xO thin films were deposited on Corning eagle 2,000 glass substrates by a RF magnetron sputtering using a ceramic target. The effect of Ar/O₂ ratios on structural and optical properties was investigated. The XRD results showed that the film demonstrated the best structural properties when the Ar/O₂ ratio equal 7:3. Sputtering ambient seemed to have minor effect on the optical properties of Mg_xZn_1−xO thin films.     

Characteristics of Ti–Ni–Pd shape memory alloy thin films

Ti–Ni–Pd thin films were deposited by RF magnetron sputtering. Microstructure and phase transformation behaviors were studied by X-ray diffraction (XRD), by transmission electron microscopy and by differential scanning calorimeter (DSC). Also tensile tests and the internal friction characteristics were examined. Annealing at 750 °C followed by subsequent annealing at 450 °C resulted in relatively homogeneous microstructure and uniform martensite/austenite transformation. The results from DSC showed clearly the martensitic transformation upon heating and cooling, the transformation temperatures are 112 °C (M* peak) and 91 °C (M peak), respectively. The transformation characteristics are also found in strain–temperature curves and internal friction–temperature curves. The film had shape memory effect. The frequency had no effect on the modulus, but the internal friction decreased with increasing frequency.     

Effect of carrier gas on metal-organic chemical vapour deposition of aluminium from dimethylethylamine alane

The effect of carrier gas, such as H₂, He, and Ar, on the deposition rate, film morphology, resistivity, and chemical composition of Al thin film from dimethylethylamine alane (DMEAA) was investigated. The deposition rate was highest in H₂ carrier gas and lowest in Ar, when the substrate temperature is above 150 °C. The surface morphology of the film deposited in He carrier gas was rough and particles from gas phase reaction, were also observed on the film surface. The film deposited in He carrier gas had a higher resistivity than the films deposited in H₂ or Ar at the higher substrate temperature due to oxygen impurity incorporated in the film.     

O2/Ar气体流量比对射频磁控溅射HfO2薄膜的影响

采用射频磁控溅射法,以HfO2陶瓷作为靶材,在石英衬底上制备了HfO2薄膜.通过椭圆偏振光谱仪(SE)、X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)研究了不同O2/Ar气体流量比对薄膜沉积速率、结构、形貌等的影响.结果表明,随着O2/Ar气体流量比从0增加到0.50,薄膜的沉积速率逐渐下降.O2/Ar气体...     

Compositional uniformity in sputter-deposited NiTi shape memory alloy thin films

Compositional uniformity in NiTi thin films produced under “cold” and “hot” target conditions using d. c. magnetron sputtering is presented in this article. Film deposited under “hot” target condition shows significantly better compositional uniformity compared to those deposited under “cold” target condition. The Ti composition in the film produced under “cold” target condition showed a 2.5 at.% loss relative to the target composition, whereas film produced under “hot” target condition exhibits composition nearly identical to that of the target. XRD and DSC measurements confirm the presence of martensitic phase at room temperature and the shape memory effect in the film deposited under “hot” target condition.     

Sputter alloying of Ni,Ti and Hf for fabrication of high temperature shape memory thin films

Abstract

In the present paper, the fabrication and characterisation of typical high temperature Ni(Ti+Hf) alloyed thin films produced by simultaneous sputter deposition from separate elemental Ni, Ti and Hf targets are presented. Film composition, determined by energy dispersive X-ray spectroscopy, was controlled by adjusting the ratio of powers applied to each target. Films deposited at room temperature had an amorphous structure and subsequent annealing at 550°C was carried out in a high vacuum environment, based on crystallisation temperature evaluation by differential scanning calorimetry (DSC). High temperature martensitic transformation, confirmed by DSC and variable temperature X-ray diffraction (XRD), was achieved by deposition of (Ti+Hf) rich Ni–Ti–Hf films. Any slight change of composition towards Ni rich reduced the transformation temperature. Atomic force microscopy and XRD illustrated that the films had a fine grain structure (～100 nm). One way shape memory effect was observed at ～200°C in a film with composition of 15·6 at.-%Hf.     

High textured AlN thin films grown by RF magnetron sputtering; composition, structure, morphology and hardness

High quality thin aluminum nitride (AlN) films have been deposited onto a silicon (1 0 0) substrate by radio frequency magnetron sputtering of a pure Al target using different gas (Ar, N₂) mixtures. The depositions were carried out at substrate temperatures varying from room temperature (plasma heating) up to 400°C. The crystalline structures were investigated by X-ray diffractometry (XRD) revealing a pronounced texture of the deposited films. Some of the compounds investigated were deposited onto a thin buffer layer of pure Al. The film surface morphology was investigated by Atom Force Microscopy (AFM) (SPM-9500J3 from Shimadzu Co), and was found to depend distinctively upon the different deposition conditions. Generally, two kinds of structures were found—a columnar one, which was densely packed or organized in planar parallel sheets, and a flat structure, (typical for mono-crystals), with rms roughness below 0.2 nm. In this paper, the influence of argon added to the sputtering gas environment on the film properties is investigated and discussed. The depth elemental distributions were calculated using 2.4 MeV ⁴He⁺ Rutherford Backscattering Spectrometry (RBS). Finally, the mechanical characteristics were described using hardness tests.     

Hysteresis,structural and composition characteristics of deposited thin films by reactively sputtered titanium target in Ar/CH4/N2 gas mixture

Abstract

Hysteresis, crystal structure and chemical composition of thin films deposited through reactive sputtering of titanium metal target in Ar/CH₄/N₂ gas mixture have been investigated. The transition from metallic to compound sputtering mode was clearly seen as the reactive gases (CH₄ and N₂) flowrate concentration first increased and subsequently decreased. Abrupt cathode current drop from 273 mA to reach a minimum value of 195 mA was observed upon addition of nitrogen gas from 0 to 10% flowrate concentration to the Ar/CH₄ gas mixture. This was also accompanied by an abrupt change in reactive gas partial pressure. Exploration of the deposition rate and film thickness showed that it decreased from 4·5 to 1·5 nm min^?1 and from 140 to 40 nm as the N₂ flowrate concentration increased from 1·5 to 7·5% at 5·5%CH₄ flowrate concentration respectively. X-ray diffraction and X-ray photoelectron spectroscopy analyses of the deposited films confirmed the formation of titanium carbide and carbonitride phases as the methane and nitrogen gas concentrations in the sputtering gas were increased.     

High‐Temperature Shape Memory Effect in Ti‐Ta Thin Films Sputter Deposited at Room Temperature

Ti‐Ta based alloys are potential high‐temperature shape memory materials with operation temperatures above 100 °C. In this study, the room temperature fabrication of Ti‐Ta thin films showing a reversible martensitic transformation and a high temperature shape memory effect above 200 °C is reported. In contrast to other shape memory thin films, no further heat treatment is necessary to obtain the functional properties. A disordered α″ martensite (orthorhombic) phase is formed in the as‐deposited co‐sputtered Ti₇₀Ta₃₀, Ti₆₈Ta₃₂ and Ti₆₇Ta₃₃ films, independent of the substrate. A Ti₇₀Ta₃₀ free‐standing film shows a reversible martensitic transformation, as confirmed by temperature–dependent XRD measurements during thermal cycling between 125 °C to 275 °C. Furthermore, a one‐way shape memory effect is qualitatively confirmed in this film. The observed properties of the Ti‐Ta thin films make them promising for applications on polymer substrates and especially in microsystem technologies.     

Photo-catalytic film deposition by atmospheric TPCVD

TiO₂ film were deposited by atmospheric thermal plasma chemical vapor deposition (TPCVD) method to investigate the rapid process for functional film deposition. The experiment was conducted under the condition where working gas was Ar, working gas flow rate was 20 l/min, deposition distance was varied from 30 to 200 mm and spraying time was 10 min. Ethanol diluted titanium tetra buthoxide was used as starting material. Consequently, even in this process TiO₂ films including anatase could be deposited, and the results of wettability and methylene blue decoloration testings suggest that the TiO₂ films have good photo-catalytic property. Besides, by using extension nozzle, columnar structure film could be deposited due to a perfect starting material vaporization. From these results, the proposed process seemed to be highly promising for the rapid formation of functional thin films.     

Control of electrical resistivity of TaN thin films by reactive sputtering for embedded passive resistors

Tantalum nitride thin films were deposited by radio frequency (RF) reactive sputtering at various N₂/Ar gas flow ratios and working pressures to examine the change of their electrical resistivity. From the X-ray diffraction (XRD) and four-point probe sheet resistance measurements of the TaN_x films, it was found that the change of the crystalline structures of the TaN_x films as a function of the N₂ partial pressure caused an abrupt change of the electrical resistivity. When the hexagonal structure TaN thin films changed to an f.c.c. structure, the sheet resistance increased from 16 Ω/sq to 1396 Ω/sq. However, we were able to control the electrical resistivity of the TaN thin film in the range from 69 Ω/sq to 875 Ω/sq, with no change in crystalline structure, within a certain range of working pressures. The size of the grains in the scanning electron microscopy (SEM) images seemed to decrease with the increase of working pressure.     

Structural and electrical properties of sputtered indium-zinc oxide thin films

In this study, indium-zinc oxide (IZO) thin films have been prepared at a room temperature, 200 and 300 °C by radio frequency magnetron sputtering from a In₂O₃-12 wt.% ZnO sintered ceramic target, and their dependence of electrical and structural properties on the oxygen content in sputter gas, the substrate temperature and the post-heat treatment was investigated. X-ray diffraction measurements showed that amorphous IZO films were formed at room temperature (RT) regardless of oxygen content in sputter gas, and micro-crystalline and In₂O₃-oriented crystalline films were obtained at 200 and 300 °C, respectively. From the analysis on the electrical and the structural properties of annealed IZO films under Ar atmosphere at 200, 300, 400 and 500 °C, it was shown that oxygen content in sputter gas is a critical parameter that determines the local structure of amorphous IZO film, stability of amorphous phase as well as its eventual crystalline structure, which again decide the electrical properties of the IZO films. As-prepared amorphous IZO film deposited at RT gave specific resistivity as low as 4.48 × 10^− 4 Ω cm, and the highest mobility value amounting to 47 cm²/V s was obtained from amorphous IZO film which was deposited in 0.5% oxygen content in sputter gas and subsequently annealed at 400 °C in Ar atmosphere.     

Fabrication and characterization of Fe3O4 thin films deposited by reactive magnetron sputtering

Fe-O thin films with different atomic ratio of iron to oxygen were deposited on glass and thermally oxidized silicon substrates at temperatures of 300, 473 and 593 K, by reactive magnetron sputtering in Ar+O₂ atmosphere. The composition and structure of the thin films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrical resistivity. It was found from XRD that with increasing the oxygen partial pressure in the working gas, the crystalline structure of the Fe-O films deposited at the substrate temperature of 473 K gradually changed from α-Fe, amorphous Fe-O, Fe₃O₄, γ-Fe₂O₃ to Fe_21.34O₃₂. The structure and chemical valence of the Fe₃O₄ films were analyzed by electron microscopy and XPS, respectively.     

Effects of oxygen pressure on the structure and photoluminescence of ZnO thin films

A series of ZnO thin films were deposited on silicon (100) substrate at 473 K by using facing target RF magnetron sputtering system at different oxygen pressure in this paper. The structure, surface morphology and photoluminescence of the ZnO thin films were characterized by X-ray diffraction, atomic force microscopy (AFM), and photoluminescence spectra (PL), respectively. The results showed that only a (002) peak of hexagonal wurtzite appeared in all ZnO thin films, indicating that ZnO films exhibited strong texture. With increasing the oxygen pressure, the results indicated that the ZnO film deposited at 1.2 Pa Ar pressure and 0.6 Pa oxygen pressure had the best preferential C-axis orientation and the weakest compressive stress. Meanwhile, AFM observation showed that ZnO film deposited at pure Ar had the highest surface roughness. With the increment of oxygen pressure, the surface roughness decreased gradually. In addition, PL measurement showed that the ZnO film deposited at 1.2 Pa Ar pressure and 0.6 Pa oxygen pressure had the strongest ultraviolet emission and the weakest blue emission.     

Pulsed laser deposition of NiTi shape memory alloy thin films with optimum parameters

A series of experiments was carried out to optimize the pulsed laser deposition parameters for the fabrication of high quality NiTi shape memory alloy thin films. Smooth NiTi shape memory alloy thin films were deposited at high growth rate with optimum deposition parameters based on the analysis of the relationships among the morphology of the target surface and the deposited thin film, the laser energy, the target–substrate distance, the thin film composition and its growth rate. Crystal structures and phase transformation temperatures of the annealed Ni_49.7Ti_50.3 thin film were characterized by using X-ray diffraction and differential scanning calorimetry, respectively. The martensitic transformation temperature of the crystallized Ni_49.7Ti_50.3 thin film is found to be lower than room temperature and 27°C lower than that of the NiTi target material. These results are attributed to the refined grain size of the thin film and its composition, which deviates slightly from Ni₅₀Ti₅₀.     

Orthogonal analysis for perovskite structure microwave dielectric ceramic thin films fabricated by the RF magnetron-sputtering method

The perovskite structure microwave dielectric ceramic thin films have been deposited by radio frequency (RF) magnetron sputtering on SiO₂(110) substrates. Subsequently, orthogonal analysis has been adopted to optimize the process parameters. The experimental results indicate that sputtering pressure has the greatest impact on comprehensive evaluation indicators such as the film quality, whereas sputtering power has a lower effect; the ratio of O₂/Ar and substrate temperature have the least impact on the process. Thus, the optimal process parameters to prepare perovskite structure dielectric thin films by RF magnetron sputtering are as follows: 200 W of sputtering power, 0.25 Pa of sputtering pressure, Ar as working gas, and substrate temperature of 610 °C.     

Preparation of amorphous TiS x thin film electrodes by the PLD method and their application to all-solid-state lithium secondary batteries

Titanium sulfide thin film electrodes were prepared by the pulsed laser deposition method using a KrF excimer laser. Thin films of various compositions were prepared under several deposition conditions such as Ar gas pressure, laser fluence, and target-substrate distance. The thickness of the titanium sulfide thin film prepared under Ar gas pressure of 0.01 Pa, the pulse energy of 200 mJ/pulse, and the distance of 5 cm between the target and the substrate was ca. 400 nm. The films prepared at room temperature showed no peaks in the XRD pattern and no periodic lattice fringe in high-resolution transmission electron microscopic images, suggesting that they were amorphous. An all-solid-state cell using a TiS_4.0 thin film electrode formed on a pelletized Li₂S–P₂S₅ glass–ceramic electrolyte showed the reversible capacity of 543 mAh g⁻¹, which was higher than that of a cell using a TiS_1.7 film. The former solid-state cell retained higher capacity for 20 cycles at room temperature.