Effect of rapid recurrent thermal annealing on the soft magnetic behaviour of Co85.5Nb8.9Zr5.6 nanocrystalline thin films

The rapid recurrent thermal annealing (RRTA) method has been used to crystallize-amorphous Co_85.5Nb_8.9Zr_5.6 soft magnetic thin films, which were fabricated by DC magnetron sputtering onto glass-ceramic substrates directly at room temperature. As a result, crystalline grains with diameter of about 10 nm were formed and a partiall nanocrystallization of the films was obtained. The soft magnetic properties of the Co-based nanocrystalline thin films were largely improved after RRTA. The resistivity is decreased by a quarter and the coercivity is also decreased. The magnetic and electrical properties were investigated using the RRTA method with varied parameters such as annealing temperature, annealing time and repeat cycle. The experimental results revealed that the RRTA is an effective method to control the magnetic and electrical properties of Co_85.5Nb_8.9Zr_5.6 thin films.     

CoNbZr非晶软磁薄膜晶化动力学研究

采用 DSC热分析技术,结合 XRD、TEM和AFM实验,对磁控溅射制备的 Co85.5Nb8.9Zr5.6非晶合金软磁薄膜进行了变温和等温晶化动力学的研究。研究结果表明:升温晶化时,薄膜的晶化的表观激活能为99.82kJ/mol;局域激活能随晶化度增加;在等温晶化过程中,平均激活能为 88. 51kJ/mol, Avrami 指数1.17~1.39, 晶化行为主要是一维表面晶化,晶核长大受扩散控制的过程。     

Magnetic and photoconductive properties of the CoxPt1−x-Pt-TiO2 nanocomposite films prepared by reactive sputter-deposition

Co-Pt-Ti-O films were prepared on SiO₂ glass substrate by sputtering of a Co-Pt-Ti composite target in Ar+O₂ atmosphere with the total pressure of 4 Pa and then in situ annealed at an elevated temperature T_a to form the Co_xPt_1−x-TiO₂ films. It is found that the ferromagnetic films grow in the form of fiber-like columnar grain about 10 nm in diameter when sputtered in the pressure ratio of O₂/Ar=1/133 followed by in situ annealing at The films contain Pt and amorphous anatase-type TiO₂ phases besides the ferromagnetic fcc-Co_xPt_1−x phase. Thus, such nanocomposite films show photoconductive properties due to the anatase-type TiO₂ phase as well as ferromagnetic properties due to the Co_xPt_1−x phase.     

Mechanism of biaxial alignment in thin films, deposited by magnetron sputtering

Biaxially aligned TiN layers have been deposited by reactive unbalanced magnetron sputtering. In this work, a mechanism for the resulting microstructure and biaxial alignment of the deposited TiN layers will be discussed. According to the described model, the resulting biaxial alignment is caused by an overgrowth mechanism (zone T) due to an anisotropy in growth rate of the different oriented grains towards the incoming material flux. Hence, the in-plane alignment will mainly depend on two parameters: the mobility during the growth (zone T condition) and the spread on the incoming material flux. This spread on the incoming material flux has been calculated by an earlier published Monte Carlo simulation program of the transport of sputtered particles towards the substrate. The model for the mechanism of biaxial alignment is validated by comparing the experimental and theoretical influence of target-substrate distance and working pressure on the resulting in-plane alignment.     

Deposition of nanocryctalline silicon thin films: Effect of total pressure and substrate temperature

The structural changes in intrinsic silicon thin films are investigated as a function of the total pressure (2 to 4 Pa) and substrate temperature (room temperature to 200 °C). Infrared absorption, Raman spectroscopy and high resolution transmission electron microscopy are applied to characterize the films. The results indicate that the films grown at 2 Pa are completely amorphous, while at 3 and 4 Pa, crystallization occurs at temperature as low as room temperature. These structural changes are well correlated to the variation of the room temperature conductivity, which increases up to about eight orders of magnitude for the nanocrystallized films. A crystalline volume fraction varying from 71 to about 90% is also observed. The growth mechanism of the nanocrystalline films is also discussed in the framework of the reported models.     

The d.c. magnetron sputtering behavior of TiO2−x targets with added Fe2O3 or Nd2O3

Targets of 6 mm thickness were prepared from TiO₂ powder with different amounts of Fe₂O₃ and Nd₂O₃ added. The targets were sintered in a vacuum furnace to obtain sub-stoichiometric rutile TiO_2−x. For both added metal oxides, it was found that they were present as titanates forming a second phase. The sputtering behavior of these mixed-oxide targets was investigated. First, the dependence of the discharge voltage and the deposition speed on the argon pressure was measured. Second, the effect of the oxygen addition on the same two parameters was investigated. Both were compared with the dependencies measured for a pure TiO_2−x target. All experiments were performed in constant power mode. The results show that Fe₂O₃ and Nd₂O₃ exhibit different effects on the sputtering behavior of TiO_2−x targets.     

Synthesis and characterization of ferromagnetic cobalt-doped tin dioxide thin films

Co-doped SnO₂ thin films are grown on sapphire (0001) substrates at 600 °C by the technique of dual-beam pulsed laser deposition. The prepared films show preferred orientation in the [100] direction of the rutile structure of SnO₂. Nonequilibrium film growth process results in doping Co into SnO₂ much above the thermal equilibrium limit. A Film with 3% of Co is ferromagnetic at room temperature with a remanent magnetization of ∼ 26% and a coercivity of ∼ 9.0 mT. As Co doping content x increases, the optical band gap absorption edge (E₀) of the Co-doped SnO₂ thin films initially shows a redshift at low x up to x = 0.12 and then increases at the higher x, which are attributed to the sp-d exchange interactions and alloying effects, respectively.     

Effect of deposition temperature on the properties of amorphous silicon carbide thin films

Silicon carbide films were deposited on n-type Si substrates (111) of resistivity 2-7 Ω cm in a high-frequency parallel-plate plasma reactor. The deposition temperatures were 250, 350 and 450 °C, respectively. The RBS results showed that the concentrations of Si and C in the films depend a little on the deposition temperature. The films contain a small amount of oxygen and nitrogen. IR results showed the presence of Si-C, Si-H, C-H, Si-O, Si-N specific bonds. The AFM micrographs revealed that the film surface is rather smooth and compact.     

Electrodeposition for antibacterial nickel-oxide-based coatings

Nickel-oxide-based films exhibiting antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive bacteria (Bacillus atrophaeus) have been fabricated by electrodeposition from aqueous solutions. However, after annealing of the films, no antibacterial activity has been observed. As-deposited films were found to consist of a mixture of nickel-oxide hydroxide and nickel hydroxide, while annealing resulted in the conversion of the films into pure NiO. Also, annealed films exhibited no production of H₂O₂, unlike as-deposited films. Thus, antibacterial activity of as-deposited films is related to the presence of nickel-oxide hydroxide/nickel hydroxide which results in the production of reactive oxygen species and antibacterial activity.     

Friction and adhesion properties of fluorocarbon polymer thin films prepared by magnetron sputtering

Fluorocarbon polymer thin films were deposited onto a SUS302 substrate with a poly(tetrafluoroethylene) (PTFE) target by three different types of r.f. magnetron sputtering systems with strong, weak and unbalanced magnetic fields. Friction and adhesion properties of these polymer thin films were evaluated.Friction coefficient of polymer thin films prepared with strong magnetic field, unbalanced magnetron and without magnetron (r.f. sputtering) was almost the same level, however, that prepared with the weak magnetic field was slightly lower than those of other thin films. Wear durability of polymer thin film increased with increase of the magnetic field.Adhesion strength between these thin films and SUS302 substrate and shear stress were measured by SAICAS. Both of the adhesion strength and shear stress of polymer thin films prepared with r.f. sputtering (without magnetron) were slightly higher than those prepared by magnetron sputtering systems.     

NiO-based nanostructured thin films with Pt surface modification for gas detection

Nanocrystalline NiO thin films were prepared by dc reactive magnetron sputtering in a mixture of oxygen and argon and subsequently coated by Pt on an NiO film surface. Very thin Pt overlayers with a thickness of about 3 and 5 nm have been deposited by magnetron sputtering. Then, the modified NiO films have been analyzed by TEM, EELS and AES. NiO thin films showed a polycrystalline structure (fcc NiO phase) with the size of nanocrystals ranging from a few nanometres to 10 nm. TEM observations both of unmodified and Pt-modified NiO films revealed that they were formed by nanocrystals and an amorphous phase. Uniformly distributed Pt particles were produced on top of the NiO surface. According to AES measurements, the presence of Ni in the spectra recorded from Pt pad indicated that the Pt layer has discontinuous nature. Electrical responses of NiO-based sensor structures towards hydrogen have been measured.     

Layer-by-layer growth of thin epitaxial Fe3Si films on GaAs (001)

Molecular beam epitaxy of Fe₃Si films on GaAs (001) is studied in situ by grazing incidence X-ray diffraction. Fe₃Si grows layer-by-layer. During deposition the growth front roughens as indicated by the damping of the X-ray oscillations and corresponding atomic force micrographs. The X-ray oscillations are modified during growth at substrate temperatures of 180 °C and below.     

Construction of a high-temperature sessile drop device

The study of the wettability in a liquid metal—solid surface system is of great technological interest for industrial processes like soldering and brazing, as well as for fundamental research in the field of diffusion, chemical reaction and formation of intermetallic phases.For the characterization of these processes the so-called contact angle between the liquid droplet and the solid substrate is measured. Therefore, a high-temperature sessile drop device was planned and constructed, and first measurements in different liquid/solid systems were performed.     

Compositional analysis of polycrystalline hafnium oxide thin films by heavy-ion elastic recoil detection analysis

The composition of polycrystalline hafnium oxide thin films has been measured by heavy-ion elastic recoil detection analysis (HI-ERDA). The films were deposited by high-pressure reactive sputtering (HPRS) on silicon wafers using an oxygen plasma at pressures between 0.8 and 1.6 mbar and during deposition times between 0.5 and 3.0 h. Hydrogen was found to be the main impurity and its concentration increased with deposition pressure. The composition was always slightly oxygen-rich, which is attributed to the oxygen plasma. Additionally, an interfacial silicon oxide thin layer was detected and taken into account. The thickness of the hafnium oxide film was found to increase linearly with deposition time and to decrease exponentially with deposition pressure, whereas the thickness of the silicon oxide interfacial layer has a minimum as a function of pressure at around 1.2 mbar and increases slightly as a function of time. The measurements confirmed that this interfacial layer is formed mainly during the early stages of the deposition process.     

非化学计量比SbOx薄膜的结晶动力学研究

利用直流磁控反应溅射法在不同氧分压下制备了SbOx薄膜,对退火前后薄膜的X射线衍射(XRD)分析表明,退火后薄膜结构发生了从非晶态向晶态的转变.利用示差扫描量热法(DSC)测出不同升温速度条件下非晶态薄膜粉末的晶化峰温度,用Kissinger公式计算了材料的结晶活化能计算结果表明,随着溅射时氧分压的增加,薄膜的结晶活化能增加,而相应的非晶态与晶态之间的焓差则呈现出相反的变化趋势.     

The DC conductivity and structural ordering of thin silicon films at the amorphous to nano-crystalline phase transition

Thin silicon films were deposited by the plasma-enhanced chemical vapor deposition using standard 13.6 MHz radiofrequency gas discharge in silane diluted by hydrogen. The deposition conditions were kept constant for all samples, with the exception of only one parameter: the degree of dilution was varied from low values that produce amorphous layers up to the high dilution that resulted in a high degree of crystalline fraction. The structural properties of the samples were analyzed by Raman and grazing incidence small angle X-ray scattering (GISAXS) while direct current (DC) dark conductivity was measured by standard methods.The ratio of the areas under corresponding transversal optical (TO) phonon peaks in Raman was taken as the ratio between crystal and amorphous volume fraction while the shift of the TO peak position was used for the estimation of the crystal size. By increasing the working gas dilution, the crystalline fraction grew from 0% to 40% and the average individual crystal size increased from 2 to 10 nm.The size of the “particles”, estimated by GISAXS using the Guinier approximation, varied from 2 to 4 nm. For a lower working gas dilution, the “particles” detected by GISAXS were spherically symmetric and showed no difference between near surface and “bulk” of the film. For a higher dilution, the particles became asymmetric and larger closer to the surface, which indicates columnar growth.The DC dark conductivity increased exponentially with the crystalline fraction, except for a very low crystal to amorphous volume ratio where the conductivity was larger, probably due to a better ordering of the amorphous phase in the vicinity of the amorphous to crystalline transition.     

Crystallization kinetics of sol-gel derived hydroxyapatite thin films

The crystallization kinetics of sol-gel derived hydroxyapatite (HA) and tricalcium phosphate (TCP) thin films were studied to determine whether viscous sintering could be used for densification. The films were approximately 900 nm thick, and were synthesized and processed on silicon substrates. The films were fired in air in a rapid thermal annealer (RTA) for various times and the degree of crystallinity was determined by measuring the intensity of characteristic X-ray diffraction lines. The growth kinetics of HA and TCP were measured between 420 and 550 °C, and between 840 and 920 °C, respectively. Films that were subjected to an accelerated aging step before firing, exhibited a significantly lower crystallization growth rate when compared to unaged films. The aged films also became harder, as measured by nanoindentation. At temperatures above 840 °C, HA transformed into both -and -TCP, with the form being dominant at lower temperatures. The activation energies for both transformations (amorphous film to HA, and HA to TCP) were determined, as were the constants for the Avrami equation. Based on the rapid crystallization kinetics observed for the amorphous film to HA transformation, densification through viscous sintering is essentially precluded in this system. © 2001 Kluwer Academic Publishers     

The effect of argon pressure on the structural and photocatalytic characteristics of TiO2 thin films deposited by d.c. magnetron sputtering

TiO₂ thin films of 200-300 nm thickness were deposited by d.c. magnetron sputtering onto glass substrates from a semiconducting TiO_2−x target in pure Ar using pressures between 0.1 and 1.0 Pa. The obtained TiO₂ coatings are transparent and have refractive indices between 2.5 and 1.9. Post deposition heat treatment at different temperatures was performed to achieve crystallization of anatase TiO₂. The as-deposited and heat treated films were examined with UV-VIS (transmission), SEM and XRD to investigate the influence of the argon pressure during deposition on the structural development during heat treatment. Additionally, the photocatalytic activity of the films was tested by measuring the decomposition rate of ethanol in a controlled gas atmosphere simulating air, and was related to their respective microstructures.     

Growth paths for the sulfurization of Cu-rich Cu/In thin films

In-situ energy-dispersive X-ray diffraction performed at the BESSY and HASY-LAB synchrotron facilities was used to observe sulfur pressure dependent growth paths for the formation of CuInS₂ thin films from Cu-rich metallic precursors. CuInS₂ can form directly from the intermetallic phases, through binary sulfides or via CuIn₅S₈. Particular attention is given to the latter reaction sequence, typical of rapid thermal processing (RTP), with complementary EDS and SEM analysis.     

Crystallization kinetics of amorphous Ga-Sb films extended for phase-change memory

Performance of phase-change materials based on Ga-Te-Sb was found getting better with decreasing Te content in our earlier studies. We concerned much properties of Te-free, Sb-rich binary Ga-Sb, which has been known to possess extremely fast crystallization behavior. Non-isothermal and isothermal crystallization kinetics of amorphous Sb-rich Ga-Sb films were explored by temperature dependent electrical resistance measurements. The crystallization temperature (183 to 261 degrees C) increases with decreasing Sb content (91 to 77 at%). The activation energy and rate-factor vary with Sb contents and reach the maximum at Ga19Sb81. The kinetic exponent is smaller than 1.5 at Sb < 85 at% denoting that the mechanism is one-dimensional crystal-growth from nuclei. The temperature corresponding to 10-year data-retention, evaluated from films, is 180 degrees C (Ga19Sb81) and 137 degrees C (Ga13Sb87), respectively. We verified memory performance using test-devices made of Ga16Sb84 working at voltages with 100 ns pulse-width.