Cathodic arc co-deposition of highly oriented hexagonal Ti and Ti2AlC MAX phase thin films

Ti₂AlC belongs to a family of ternary nanolaminate alloys known as the MAX phases, which exhibit a unique combination of metallic and ceramic properties. Here we report pulsed cathodic arc deposition of c axis normal oriented Ti₂AlC thin films on α-Al₂O₃ (001) single crystal substrates heated to 900 °C, without an intentionally pre-deposited seed layer. Oriented hexagonal Ti is observed in some films and an in-plane epitaxial relationship between the α-Al₂O₃ (001) substrate, the hexagonal Ti and Ti₂AlC MAX phase is observed. We observe formation of the Ti₂AlC phase in all films despite variations in elemental composition. The electrical resistivity of our films was in the range 0.48-0.67 μΩ m, higher than other values found for Ti₂AlC in the literature.     

Synthesis and characterization of Nb2AlC thin films

We report on the synthesis and characterization of epitaxial c-axis oriented Nb₂AlC thin films deposited on c-axis sapphire (Al₂O₃) substrates by magnetron sputtering. Selected area electron diffraction reveal that independent of substrate temperature or film stoichiometry, there is the growth of a secondary phase not found in bulk, Nb₅Al₃C_x with a- and c-axis lattice constants of 7.746 Å and 5.246 Å, respectively. Scanning electron micrographs reveal large surface features, many with hexagonal shape and faceted texture. Atomic force microscopy topographical measurements indicate a surface roughness of approximately 15% of the total film thickness. Electrical transport measurements show typical metal-like conduction with a room temperature resistivity of ≈ 0.9 μΩ-m and a residual resistivity ratio of 2.5. A superconducting transition was found at ≈ 440 mK.     

Sputter deposition from a Ti2AlC target: Process characterization and conditions for growth of Ti2AlC

Sputter deposition from a Ti₂AlC target was found to yield Ti-Al-C films with a composition that deviates from the target composition of 2:1:1. For increasing substrate temperature from ambient to 1000 °C, the Al content decreased from 22 at.% to 5 at.%, due to re-evaporation. The C content in as-deposited films was equal to or higher than the Ti content. Mass spectrometry of the plasma revealed that the Ti and Al species were essentially thermalized, while a large fraction of C with energies > 4 eV was detected. Co-sputtering with Ti yielded a film stoichiometry of 2:0.8:0.9 for Ti:Al:C, which enabled growth of Ti₂AlC. These results indicate that an additional Ti flux balances the excess C and therefore provides for more stoichiometric Ti₂AlC synthesis conditions.     

Crystallization kinetics and martensitic transformation of Ti49Ni46.5Ce4.5 alloy thin film

The Ti₄₉Ni_46.5Ce_4.5 alloy thin film was prepared by direct current (DC) magnetron sputtering system for the first time. Crystallization kinetics, phase composition and the behaviors of martensitic transformation were studied. The results by X-ray diffraction (XRD) and differential scanning calorimeter (DSC) demonstrated that the primary second phase of TiNiCe alloy thin films was Ce₂Ni₇ phase, apparent activation energy was determined to be 510 kJ/mol at the continuous heating process, Avrami exponents for different isothermal temperature were in the range of 1.1-1.88 between 713 and 730 K, one-step martensitic transformation was observed in the crystallized Ti₄₉Ni_46.5Ce_4.5 alloy thin films. The influence of thermal process on martensitic transformation temperature was investigated with non-isothermal and isothermal crystallization. The reason behind the transformation temperature change was also discussed.     

Crystallization behavior and resistance change in eutectic Si15Te85 amorphous films

Crystallization process and the corresponding electrical resistance change were investigated in eutectic Si₁₅Te₈₅ amorphous thin films. The Si₁₅Te₈₅ amorphous film showed two-stage crystallization process upon heating. In the first stage, the Si₁₅Te₈₅ amorphous crystallized into Te crystals at 175 °C. In the second stage, the residual amorphous phase crystallized into Si₂Te₃ crystals at above 300 °C accompanying the resistance drop. Before the second crystallization, the electrical resistance once increased in the temperature range of about 250-295 °C. This phenomenon can be explained by considering the formation of amorphous phase with a high electrical resistivity.     

Significant enhancement in quality factor of Zn2TiO4 with Cu-substitution

Zinc orthotitanate (Zn_1−xCu_x)₂TiO₄, 0 ≤ x ≤ 0.20, spinel samples were prepared by solid state reaction and sintering. 1060 °C was the optimal sintering temperature for all the Cu-substituted samples which showed sintered density ≥94%, and maximum unloaded quality factor (Q_uf). SEM microphotographs revealed fairly uniform grains between 2 and 20 μm depending upon the composition. Microwave measurements at ∼7.1-7.5 GHz on these samples (as dielectric resonators) showed with Cu-substitution a steep increase in Q_uf value from 2100 GHz (for Zn₂TiO₄, x = 0) to 15,200 GHz (for x = 0.10), a significant jump of over 7 times, while ε^′r was ∼20 (for x = 0) and ∼18 (x = 0.10). The jump in Q_uf in Cu-substituted samples was attributed partly to improved sintered density and partly to absence of paramagnetic Ti³⁺, as revealed by electron spin resonance spectra at 9.1 GHz.     

Crystallization behavior of Nd-doped SrBi2Ta2O9 thin films prepared by magnetron sputtering

Nd-doped SrBi₂Ta₂O₉ thin films are magnetron-sputtered on Pt/Ta/SiO₂/Si substrates. The effect of heating rate on crystallization behavior is investigated with conventional furnace annealing (CFA) and rapid thermal annealing (RTA). Grazing incidence X-ray diffraction and field emission scanning electron microscopy reveal that the crystallization goes through three stages (phases): amorphous, fluorite and finally Aurivillius. Under RTA, the fluorite-to-Aurivillius transformation starts around 100 °C lower than that under CFA. The reasons behind the transformation temperature drop are also discussed.     

Crystallization and Hardness of Melt Spun Fe73Si13B9Nb4Cu1 Alloy

An alloy having composition Fe₇₃Si₁₃B₉Nb₄Cu₁ was synthesized by melt spinning to investigate the kinetics of crystallization. Techniques of differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Mössbauer spectroscopy were employed to characterize the phases produced due to annealing at various temperatures. High temperature DSC revealed two stage crystallization reactions. First stage, crystallization occurs at temperature around 514°C with the production of α-Fe (bcc) and Fe₃Si phases. In the second stage, Fe₂B and α-Fe (Si,Nb) phases were produced. Mössbauer results revealed the formation of Fe₃Si, Fe₁₃Si₃ and Fe₇Si₁ in the first stage and Fe₃Si, Fe₁₃Si₃, Fe₂B and α-Fe (Si,Nb) phases in the second stage of crystallization. An abrupt change in average internal magnetic field was observed at 500°C. The maximum hardness value was found for the sample heat-treated at 500°C.     

Thermal stability and crystallization kinetics of sputtered amorphous Si3N4 films

The crystallization of thin silicon nitride (Si₃N₄) films deposited on polycrystalline SiC substrates was investigated by X-ray diffractometry as a function of annealing time. The amorphous Si₃N₄ films were produced by means of reactive r.f. magnetron sputtering. Annealing at temperatures between 1300 and 1700 °C led to the formation of crystalline films composed of -Si₃N₄ and β-Si₃N₄. The fraction of β-Si₃N₄ in the films reaches approximately 40% at temperatures above 1550 °C. Both polymorphic modifications were formed simultaneously during the crystallization process. A transformation of -Si₃N₄ to β-Si₃N₄ could not be observed in the time and temperature range investigated. The crystallization process of amorphous Si₃N₄ can be described according to the Johnson–Mehl–Avrami–Kolmogorov (JMAK) formalism, assuming a three-dimensional, interface controlled grain growth from pre-existing nuclei. The rate constants show an Arrhenius behaviour with an activation enthalpy of approximately 5.5 eV.     

TiO2/SiO2复合薄膜的晶化特征和结构转变研究

对TiO2／SiO2复合薄膜的晶化特征进行了分析，研究表明，随着TiO2含量的增加，其晶化温度降低，而由锐钛矿相完全转变为金红石相的速度减慢．SiO2的析晶温度也随着TiO2含量的增加而降低，即TiO2具有诱导SiO2析晶的作用．锐钛矿晶粒尺寸的增加幅度随着TiO2含量的降低和热处理温度的升高而增大．其晶粒尺寸的大小与热处理时间的平方根成正比．认为由于TiO2含量的不同，造成薄膜中由锐钛矿相完全转变成金红石相的速度差异主要来自于薄膜中应力的作用．     

Characterization of phase transition in silver photo-diffused Ge2Sb2Te5 thin films

Surface activity of thermally evaporated amorphous chalcogenide films of Ge₂Sb₂Te₅ has been investigated. Silver (Ag) is readily deposited on such films from appropriate aqueous ionic solution and Ag diffuses into the films upon irradiation with energetic photons. The composition of Ge₂Sb₂Te₅ thin films and the amount of Ag photo-diffused has been gathered from electron probe micro-analyzer having a wavelength dispersive spectrometer. The composition of the films was found to be very close to the bulk used to deposit films and the amount of Ag photo-diffused was ∼ 0.38 at. %. X-ray diffraction and temperature dependent sheet resistance studies have been used for the structural analysis of the bulk alloy, as-deposited, Ag photo-diffused and annealed films at different temperatures. The films remain amorphous after Ag photo-diffusion into the amorphous Ge₂Sb₂Te₅ films. The reflectivity, reflectivity contrast and extinction coefficient of the crystalline and amorphous photo-diffused thin films are presented. The optical band gaps of the amorphous and crystalline photo-diffused (Ge₂Sb₂Te₅)_100−xAg_x=0.38 phase change thin films have also been calculated from absorption data using UV-VIS spectroscopy.     

Hump peak formation and the crystallization in amorphous Al87Co10Ce3 alloy

A distinct hump peak was observed at the scattering angle 2θ ≈ 44° in the X-ray diffraction (XRD) pattern of rapidly quenched amorphous Al₈₇Co₁₀Ce₃ alloy. From the XRD patterns of amorphous Al-Co-Ce alloys with different compositions, it is found that the intensity of the hump peak increases as the Co/Ce atomic ratio increases, while the prepeak which characterizes the medium-range order (MRO) becomes weak. The hump peak has a close relationship with the glass forming ability in the Al-Co-Ce system. Furthermore, the crystallization behavior of Al₈₇Co₁₀Ce₃ alloy was investigated by the DSC and XRD methods. Compared with Al₈₇Ni₁₀Ce₃ alloy, Al₈₇Co₁₀Ce₃ alloy did not show a single process of grain growth for fcc-Al particle. The formation of a hump peak is presumed to be associated with the presence of pre-existing nuclei of fcc-Al and Co₂Al₉ in as-quenched amorphous Al₈₇Co₁₀Ce₃ alloy.     

Crystallization process in Ge2Sb2Te5 amorphous films

The aim of this work is to investigate the isokinetic and isothermal amorphous-to-crystalline phase transformation process in Ge₂Sb₂Te₅ ternary alloys. The experiments were carried out using electrical impedance, X-ray diffraction and reflection measurements. The results have shown that, upon annealing, the crystallization process in amorphous Ge₂Sb₂Te₅ films starts with nuclei which were identified as the Ge₁Sb₄Te₇ crystalline phase. As temperature increases (or time of isothermal annealing) these nuclei are transformed into the fcc-Ge₂Sb₂Te₅ phase. In order to establish the mechanism of crystallization for this system, a stochastic lattice model was implemented to analyze nucleation and growth of the two phases involved (i.e., the metastable Ge₁Sb₄Te₇ nuclei followed by the stable fcc-Ge₂Sb₂Te₅). The results of the simulations demonstrate close agreement with experimental results. Furthermore, the crystallization process in amorphous films with the Ge₁Sb₄Te₇ composition shows the existence of only one phase during the whole process and can be described by the classical Johnson-Mehl-Avrami-Kolmogorov model.     

Crystallization of amorphous Si thin films by the reaction of MoO3/Al nanoengineered thermite

In this work, we investigated a new crystallization method for amorphous silicon (a-Si) using a mixture of nano-energetic materials: molybdenum oxide and aluminum (MoO₃/Al). The purpose of using nano-energetic materials is to improve the performance of a-Si films with a self-propagating exothermic reaction over a period of microseconds without any substrate damage. The mixture of MoO₃/Al nanopowders was used for a thermite reaction for crystallization of a-Si thin films.Characterization results showed that a-Si thin films were successfully crystallized to poly-Si as evidenced by a Raman peak near 519 cm^− 1. The crystalline volume fraction of poly-Si after the nanoengineered thermite reaction was about 94.7% and poly-Si grains was uniformly distributed with an average grain size of around 40-50 nm. These results indicate that high quality poly-Si thin films were successfully prepared on the substrate.     

Crystallization behavior and thermoelectric characteristics of the electrodeposited Sb2Te3 thin films

Crystallization behavior of the electrodeposited Sb₂Te₃ film was characterized and the effect of the amorphous-crystalline transition on the Seebeck coefficient was evaluated. The as-electrodeposited Sb₂Te₃ film was amorphous and exhibited the Seebeck coefficient of 268-322 μV/K, which was much larger than the value of the crystalline Sb₂Te₃ film. When annealed at temperatures above 100 °C, the Seebeck coefficient of the Sb₂Te₃ film dropped significantly to 78-107 μV/K due to the amorphous-crystalline transition at 94 °C. The thermal stability of the electrodeposited Sb₂Te₃ film was improved by the addition of Cu, and the crystallization temperature of the CuSbTe film increased up to 149.5 °C.     

非晶态固体在压力下的晶化

综述了压力对非晶态合金的晶化行为的影响。首先介绍压力作用对不同类型晶化过程的作用，主要是晶化温度的变化，然后通过体积变化、原子扩散、界面和塑性变形几个方面分析压力如何影响非晶态固体晶化过程的。多数非晶合金体系表现出晶化温度随压力升高，热稳定性增加，说明原子扩散仍然是主要的影响因素。此外，少数非晶合金体系则需要考虑新生晶体／非晶界面的作用，在一定条件下，晶化温度反而随压力升高而下降。塑性变形也可以降低非晶的热稳定性。     

ArF-line high transmittance attenuated phase shift mask blanks using amorphous Al2O3-ZrO2-SiO2 composite thin films for the 65-, 45- and 32-nm technology nodes

Amorphous (ZrO₂)_x-(SiO₂)_1−x and (Al₂O₃)_x-(ZrO₂)_y-(SiO₂)_1−x−y composite films were prepared using r.f. unbalanced magnetron sputtering in an atmosphere of argon and oxygen at room temperature. The (ZrO₂)_x-(SiO₂)_1−x and (Al₂O₃)_x-(ZrO₂)_y-(SiO₂)_1−x−y composite films were completely oxidized when an O₂/Ar flow rate ratio of 2.0 was used. The optical constants of these thin films depend linearly on the mole fraction of corresponding films. By tuning the (x, y) mole fractions of (Al₂O₃, ZrO₂) in the (Al₂O₃)_x-(ZrO₂)_y-(SiO₂)_1−x−y composite films, the optical constants can meet the optical requirements for a high transmittance attenuated phase shift mask (HT-AttPSM) blank. The n-k values in the quadrangular area in the (x, y) plane, where x and y represent the mole fractions of Al₂O₃ and ZrO₂, respectively, meet the optical requirements for an HT-AttPSM blank with an optimized transmittance of 20 ± 5% in ArF lithography. It is noted that the quadrangular area is bounded by (0, 0.31), (0, 0.62), (0.26, 0) and (0.57, 0). All the films also met the chemical and adhesion requirements for an HT-AttPSM application. One (Al₂O₃)_0.1-(ZrO₂)_0.52-(SiO₂)_0.38 composite film was fabricated with optical properties that meet the optimized optical requirements of ArF-line HT-AttPSM blanks. Combined with these HT-AttPSMs, ArF-line (immersion) lithography may have the potential of reaching 65-, 45-nm and possibly the 32-nm technology nodes for the next three generations.     

Low temperature chemical vapor deposition of nanocrystalline V2O5 thin films

Spatially uniform, carbon-free thin films of V₂O₅ were deposited on silicon by chemical vapor deposition using vanadium oxide triisopropoxide and water as gaseous precursors, in the temperature range of 100-300 °C. Films with substantial crystallinity were obtained for deposition temperatures as low as 180 °C. The “neat” chemistry that nominally leaves no fragments of ligand or water in the solid promotes film purity and reduces the deposition temperature needed for crystallization. Such deposition temperatures also open up additional possibilities for using crystalline vanadia on fragile substrates such as polymers for electronics and optical applications.     

Formation and transformation of ZnTiO3 prepared by sputtering process

Zinc titanate (ZnTiO₃) films were prepared using RF magnetron sputtering at substrate temperatures ranging from 30 to 400 °C. Subsequent annealing of the as-deposited films was performed at temperatures ranging from 600 to 900 °C. It was found that all as-deposited films were amorphous, as confirmed by XRD. This was further confirmed by the onset of crystallization that took place at annealing temperatures 600 °C. The phase transformation for the as-deposited films and annealed films were investigated in this study. The results revealed that pure ZnTiO₃ (hexagonal phase) can exist, and was obtained at temperatures between 700 and 800 °C. However, it was found that decomposition from hexagonal ZnTiO₃ to cubic Zn₂TiO₄ and rutile TiO₂ took place with a further increase in temperature to 900 °C.     

K_2O-MgO-MgF_2-SiO_2系统固相反应与玻璃析晶相变反应的比较

K_2O-MgO-MgF_2-SiO_2系统与云母型微晶玻璃的化学组成密切相关。作者采用显微结构的研究方法,研究了该系统在不同反应条件下固相反应和玻璃析晶相变反应的历程;根据 X-射线衍射分析结果和玻璃晶化过程中物相的形貌变化,比较了两个反应过程的差异。值得指出,虽然该系统固相反应与玻璃析晶相变反应的过渡相的种类和含量不同,但它们的最终反应产物都是含氟四硅酸云母。