Influence of rapid thermal annealing on structure and interfacial characteristic of ZnO thin films

Highly C‐axis oriented ZnO thin film was manufactured by radio‐frequency magnetron sputtering technique on Si (111) substrate. The main objective was to study the influence of rapid thermal annealing (RTA) temperature on the structure and interfacial characteristic of ZnO thin films. X‐ray diffraction results showed that the ZnO thin films annealed at 600 °C by RTA technique had a perfect C‐axis preferred orientation compared to the other ZnO thin films, and the full width at half maximum of ZnO (002) rocking curve measurements indicted that the RTA‐annealed ZnO thin films possessed better crystal structure. Atom force microscopy displayed that the grain size of RTA‐annealed ZnO thin films was fine and uniform compared with the as‐deposited ZnO thin films, although the grains grew in RTA process and the root meant square roughness was smaller than that of as‐deposited films. High‐resolution transmission electron microscopy showed that there was an obvious amorphous layer between ZnO thin films and Si substrate, but the RTA‐annealed ZnO thin films exhibited larger and denser columnar structure and a preferred orientation with highly c axis perpendicular to the amorphous layer. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of gold‐induced crystallization process on the structural and electrical properties of germanium thin films

Gold‐induced (Au‐) crystallization of amorphous germanium (α‐Ge) thin films was investigated by depositing Ge on aluminum‐doped zinc oxide and glass substrates through electron beam evaporation at room temperature. The influence of the postannealing temperatures on the structural properties of the Ge thin films was investigated by employing Raman spectra, X‐ray diffraction, and scanning electron microscopy. The Raman and X‐ray diffraction results indicated that the Au‐induced crystallization of the Ge films yielded crystallization at temperature as low as 300°C for 1 hour. The amount of crystallization fraction and the film quality were improved with increasing the postannealing temperatures. The scanning electron microscopy images show that Au clusters are found on the front surface of the Ge films after the films were annealed at 500°C for 1 hour. This suggests that Au atoms move toward the surface of Ge film during annealing. The effects of annealing temperatures on the electrical conductivity of Ge films were investigated through current‐voltage measurements. The room temperature conductivity was estimated as 0.54 and 0.73 Scm⁻¹ for annealed samples grown on aluminum‐doped zinc oxide and glass substrates, respectively. These findings could be very useful to realize inexpensive Ge‐based electronic and photovoltaic applications.     

以LiCoO2为阴极的全固态薄膜锂电池的研究

Amorphous and oriented polycrystalline LiCoO2 thin films, used as cathode material for an all-solid-state thin film battery, were fabricated by using RF magnetron sputtering and annealed at different temperatures. The morphology and structure of LiCoO2 thin films were characterized by scanning electron microscopy and X-ray diffraction. All-solid-state thin film batteries, comprised of LiCoO2 cathode films with different structures, lithium phosphorous oxynitride electrolyte film and metallic lithium anode film, was successfully prepared and their properties were examined by chronopotentiometry. Results showed that the structure and crystallinity of the LiCoO2 films strongly influenced the electrochemical performance of all-solid-state thin film lithium batteries. Worth nothing was the battery with an oriented polycrystalline LiCoO2 film it exhibited the best electrochemical performance, and delivered a discharge capacity of ～55.4 μAh/cm2μm. Furthermore, when subjected to over 450 charge/discharge cycles, that battery suffered no obvious fode in capacity.     

Influence of thermal annealing on the microstructure,hardness and corrosion behavior of TiAlSiCuN nanocomposite films

Nanocomposite TiAlSiCuN films were deposited on high speed steels by filtered magnetic arc ion plating. Detailed properties of the films annealed at various temperatures are studied. After thermal annealing at different temperatures ranging from 400 to 800 °C, changes in the film micro‐structure, chemical and phase composition, surface morphology, hardness and polarization curve properties were systematically characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, nano‐indenter and electrochemical workstation, respectively. It was found that the TiAlSiCuN films could be fully oxidized at 800 °C, Al and Ti atoms all diffused outwards and formed dense protective Al₂O₃ and TiO₂ layer. Simultaneously, the TiAlN phase gradually disappeared. The films annealed at 400 °C obtained the highest hardness because of the certain grain growth and little generated oxides. Besides, the certain formation of dense protective Al₂O₃ layer made the TiAlSiCuN film annealed at 600 °C present the least corrosion current density and the corrosion voltage. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of thermal annealing on the microstructure and mechanical properties of magnetron sputtered hydrogenated amorphous carbon films

Hydrogenated amorphous carbon films were deposited by magnetron sputtering of a carbon target in a methane/argon atmosphere. A postdeposition annealing at 300 °C was performed and the microstructure, bonding structure and mechanical properties of the as‐deposited and annealed films were analyzed and compared directly by high‐resolution transmission electron microscopy, micro‐Raman spectroscopy, XPS, and nanoindentation. The results showed that the carbon films are quite stable upon annealing, since there are only minor changes in microstructure and chemical bonding in the amorphous matrix. The hardness of the films remained unaffected, but the elastic properties were somewhat deteriorated. In comparison to the outcomes of our previous work on the growth of fullerene‐like hydrogenated carbon films, we can state that the formation of fullerene‐like carbon structures requires different sputtering process conditions, such as a higher ion energy and/or different sputtering target. Copyright © 2011 John Wiley & Sons, Ltd.     

Deposition of Silicon Carbide Thin Films from 1,1-Dimethyl-1-Silacyclobutane

1,1-Dimethyl-1-silacyclobutane was used as a single-source precursor to deposit SiC thin films on Si(100) and Si(111) by low-pressure chemical vapor deposition (LPCVD). Polycrystalline β-SiC thin films were grown at temperatures 1100 and 1200°C. At temperatures between 950 and 1100°C, amorphous thin films of silicon carbide were obtained. The films were studied by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and electron diffraction (ED).     

Useful and accessible organometallic precursors for preparation of zinc sulfide and indium sulfide thin films via solution pyrolysis (printing) method

Polycrystalline β-zinc sulfide thin films were prepared by solution pyrolysis of an ethylzinc isopropylthiolate–zinc bis(dibutyldithiocarbamate) combined precursor (EtZnSiPr–Zn(S₂CNnBu₂)₂) in chloroform solution on glass or silicon(111) substrates at 300°C. Homogeneous but amorphous indium sulfide thin films were obtained from butylindium bis(isopropylthiolate) (nBuInSiPr₂) in P-xylene on these substrates at 300°C similarly. The sulfide thin films obtained were characterized by means of X-ray photoelectron spectroscopy (XPS), X-ray fluorescence Microanalysis, scanning electron microscopy (SEM) and optical band gap measurements.     

Effect of substrate temperature on morphology and electrochemical performance of radio frequency magnetron sputtered lithium nickel vanadate films used as negative electrodes for lithium microbatteries

Lithium nickel vanadate thin films were prepared by radio frequency magnetron sputtering at various substrate temperatures (Ts). These thin films have been investigated as anode electrode material in the use of microbatteries. Films were characterized by Rutherford backscattering spectroscopy, nuclear reaction analysis, Auger electron spectroscopy, glancing-incidence X-ray diffraction analysis, Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and high-resolution transmission electron microscopy techniques. The anodic electrochemical performances of the films have been evaluated by cyclic voltammetry at a scan rate of 1 mV/s and by galvanostatic cycling, with lithium metal as the counter and the reference electrode, and cycled in the range of 0.02-3.0 V at a current density of 75 microA/cm2. Thin films prepared at a Ts of 650 degrees C show a discharge capacity at the 20th cycle of 1100 (+/-10) mAh/g, which exhibited excellent capacity retention with a small capacity fade.     

Sputter‐deposited Ni/Ti double‐bilayer thin film and the effect of intermetallics during annealing

In the present study, a double bilayer of a Ni/Ti thin film was investigated. A nanoscale NiTi thin film is deposited in a Ni–Ti–Ni–Ti manner to form a double‐bilayer structure on a Si(100) substrate. Ni and Ti depositions were carried out by using d.c. and r.f. power, respectively, in a magnetron sputtering chamber. Four types of bilayers are formed by varying the deposition time of each layer (i.e. 15, 20, 25, and 30 min). The as‐deposited amorphous thin films were annealed at 300, 400, 500, and 600 °C for 1 h to achieve the diffusion in between the layers. Microstructures were analyzed using field‐emission scanning electron microscope and high‐resolution transmission electron microscope. It was found that, with the increase in annealing temperature from 300 to 600 °C, the diffusion at the interface and atomic migration on the surface increase. Cross‐sectional micrographs exhibited the interdiffusion between the two‐layer constituents, especially at higher temperatures, which resulted in diffusion patches along the interface. Phase analyses, performed by grazing incidence X‐ray diffraction, showed the formation of intermetallic compounds with some silicide phases that enhance the mechanical properties. Nanoindentation and atomic force microscopy were carried out to know the mechanical properties and surface profiles of the films. The surface finish is better at higher annealing temperatures. It was found that for annealing temperatures varying from 300 to 600 °C, the increase in annealing temperature resulted in a gradual increase in atomic‐cluster coarsening with improved adatom mobility. Copyright © 2016 John Wiley & Sons, Ltd.     

Nanocrystals grown in amorphous Cr and CrNi thin films

The structure of vacuum annealed amorphous sputtered Cr and CrNi (55:45) thin films has been studied by transmission electron microscopy (TEM) and electron diffraction (TED). The thin films with thicknesses ranging from 150 to 600 Å were annealed while still on their alkali halide substrates under high vacuum at temperatures ranging from 200 to 370°C. The TEM and TED data permitted to establish the annealing conditions (temperature, duration), which lead to the nucleation and growth of nanosized crystals in the Cr and CrNi icosahedral glasses.     

Characterisation and properties of magnetron sputtered nanoscale bi‐layered Ni/Ti thin films and effect of annealing

Single‐bi‐layer of Ni–Ti thin film was deposited using DC and RF magnetron sputtering technique by layer‐wise deposition of Ni and Ti on Si(100) substrate in the order of Ni as the bottom layer and Ti as the top layer. The deposition of these amorphous as‐deposited thin films was followed by annealing at 300 °C, 400 °C, 500 °C, and 600 °C temperature with 1‐h annealing time for each to achieve crystalline thin films. This paper describes the fabrication processes and the novel characterization techniques of the as‐deposited as well as the annealed thin films. Microstructures were analysed using FESEM and HRTEM. Nano‐indentation and AFM were carried out to characterize the mechanical properties and surface profiles of the films. It was found that, for the annealing temperatures of 300 °C to 600 °C, the increase in annealing temperature resulted in gradual increase in atomic‐cluster coarsening with improved ad‐atom mobility. Phase analyses, performed by GIXRD, showed the development of silicide phases and intermetallic compounds. Cross‐sectional micrographs exhibited the inter‐diffusion between the two‐layer constituents, especially at higher temperatures, which resulted either in amorphization or in crystallization after annealing at temperatures above 400 °C. Copyright © 2015 John Wiley & Sons, Ltd.     

Lithium intercalation in thin amorphous-silicon films

Electrochemical intercalation of lithium in thin films of amorphous hydrogenated silicon (a-Si:H), deposited at temperatures of 100 and 250°C on stainless-steel substrates, is studied. It is shown that the discharge capacity of films of identical thicknesses manufactured at a temperature of 250°C is greater than that for films produced at of 100°C. Dependence of the discharge capacity of the films manufactured at 250°C on their thickness is examined. It is established that an increase in the film thickness leads to acceleration of the decrease in the discharge capacity in the course of cycling. At a current density of 0.175 mA cm^?2, the discharge capacity of films 0.25 and 1.35 μm thick equals nearly 2 Ah g^?1 in a third cycle, whereas in a hundredth cycle it amounts to 1.10 and 0.37 Ah g^?1, respectively. The diffusion coefficient for lithium in the films is equal to ～10^-13 cm²s^?1.     

Effect of Lithia and Substrate on the Electrochemical Performance of a Lithia/Cobalt Oxide Composite Thin‐Film Anode

Highly porous reticular Li₂O/CoO composite thin films fabricated by electrostatic spray deposition were investigated by using X-ray diffraction, scanning electron microscopy, galvanostatic cell-cycling measurements, and AC impedance spectroscopy measurements. The results of the electrochemical tests indicate that the initial coulombic efficiency and capacity retention are dependent on Li₂O content and the specific surface area of the deposited layer. Irrespective of the type of substrate, the electrode gave the best electrochemical performance when the molar ratio of Li to Co was controlled at 1:1. At the optimal composition, at 0.2 C the initial coulombic efficiency was as high as 81.9 % and 83.6 % for the film on Cu foil and on porous Ni, respectively. The Li₂O/CoO (Li/Co=1:1) films on Ni foam and Cu foil had sustained capacities of up to 790 and 715 mAh g⁻¹, respectively, at a rate of 1 C over 100 cycles at 25 °C. Similar cycling experiments carried out at 70 °C showed that the capacity is temperature-sensitive, and it exhibited reversible capacities as high as 1018 (Cu foil) and 1269 mAh g⁻¹ (Ni foam) for up to 100 cycles. The thin-film electrodes on Ni foam always performed better than those on Cu foil. Cycling at elevated temperature (70 °C) also resulted in a significant increase in capacity.     

High Performance Full Sodium‐Ion Cell Based on a Nanostructured Transition Metal Oxide as Negative Electrode

A novel design of a sodium‐ion cell is proposed based on the use of nanocrystalline thin films composed of transition metal oxides. X‐ray diffraction, Raman spectroscopy and electron microscopy were helpful techniques to unveil the microstructural properties of the pristine nanostructured electrodes. Thus, Raman spectroscopy revealed the presence of amorphous NiO, α‐Fe₂O₃ (hematite) and γ‐Fe₂O₃ (maghemite). Also, this technique allowed the calculation of an average particle size of 23.4 Å in the amorphous carbon phase in situ generated on the positive electrode. The full sodium‐ion cell performed with a reversible capacity of 100 mA h g^?1 at C/2 with an output voltage of about 1.8 V, corresponding to a specific energy density of about 180 W h kg^?1. These promising electrochemical performances allow these transition metal thin films obtained by electrochemical deposition to be envisaged as serious competitors for future negative electrodes in sodium‐ion batteries.     

Thickness and temperature‐dependent study of Co/Si interface

Thin films of cobalt (10, 40, and 100 nm) are deposited on Si substrate by electron beam physical vapor deposition technique. After deposition, 4 pieces from each of the wafers of silicon substrate were cut and annealed at a temperature of 200°C, 300°C, and 400°C for 2 hours each, separately. X‐ray diffraction, atomic force microscopy, and transmission electron microscopy (TEM) are used to study the structural and morphological characteristics of the deposited films. To obtain TEM images, Co films are deposited on Cu grids; so far, no such types of TEM images of Co films are reported. Structural studies confirm nanocrystalline nature with hexagonal close packed structure of the deposited Co film at lower thickness, while at higher thickness, film structure transforms to amorphous with lower surface roughness value. The particle sizes in all the cases are in the range of 3 to 5 nm. Micro‐Raman spectroscopy is also used to study the phase formation and chemical composition as a function of thickness and temperature. The results confirm that the grown films are of good quality and free from any impurity. Studies show the silicide formation at the interface during deposition. The appearance of new band at 1550 cm⁻¹ as a result of annealing indicates the structural transformation from CoSi to CoSi₂, which further enhances at higher annealing temperatures.     

50 keV H+ ion beam irradiation of Al doped ZnO thin films: Studies of radiation stability for device applications

Thin films of Al doped ZnO (Al:ZnO) were deposited on two substrates (Si and glass) at room temperature and 300°C using DC magnetron sputtering. These films were bombarded with 50 keV H⁺ beam at several fluences. The pristine and ion beam irradiated films were analysed by X‐ray diffraction, Raman spectroscopy, scanning electron microscopy, and UV‐Vis spectroscopy. The X‐ray diffraction analysis, Hall measurements, Raman and UV‐Vis spectroscopy confirm that the structural and transport properties of Al:ZnO films do not change substantially with beam irradiation at chosen fluences. However, in comparison to film deposited at room temperature, the Al:ZnO thin film deposited at 300°C shows increased transmittance (from 70% to approximately 90%) with ion beam irradiation at highest fluence. The studies of surface morphology by scanning electron microscopy reveal that the ion irradiation yields smoothening of the films, which also increases with ion fluences. The films deposited at elevated temperature are smoother than those deposited at room temperature. In the paper, we discuss the interaction of 50 keV H⁺ ions with Al:ZnO films in terms of radiation stability in devices.     

Simultaneous Carbon Coating and Lithiation of Oxides by Contact Reaction

Chemical lithiation and carbon coating of cathode materials can lead to strongly improved electrochemical properties, especially if the active materials have low electronic conductivity. This behavior is quite often the case for new high‐capacity materials. A novel synthesis method is presented in which the two processes are performed simultaneously by employing Li₂C₂ as both the carbon and the lithium source. In this contact reaction, the acetylide anion C₂^2? is oxidized to carbon and deposited directly on the surface of the active material, while lithium is reductively inserted into the oxidant. Two different synthesis routes are demonstrated: a tribochemical approach at room temperature and heat treatments between 150 and 600 °C. The applicability of these new carbon‐coating methods are demonstrated on various crystalline and amorphous Li_xV₂O₅ phases. The composites obtained were characterized by powder X‐ray diffraction, transmission electron microscopy, and Raman spectroscopy. In addition, electrochemical data confirm the chemical lithiation and show that lithiated Li_xV₂O₅ with specific phases can be prepared selectively.     

基片温度对LiCoO2薄膜结构与电化学性能的影响

采用射频(RF)磁控溅射技术制备了用于全固态薄膜锂电池的非晶态和多晶LiCoO2阴极薄膜,利用XRD和SEM研究了沉积温度对LiCoO2薄膜结构和形貌的影响,并研究了高温退火后薄膜的电化学性能.研究结果表明,随著基片温度的不同,薄膜成分、表面形貌以及电化学行为有明显差异.室温沉积的薄膜很难消除薄膜中Li2CO3的影响,经过高温退火处理后也无法形成有效的多晶LiCoO2薄膜,而150℃沉积的薄膜经过高温退火后形成了有利于锂离子嵌入的多晶LiCoO2结构,薄膜显示出了较好的电化学性能.     

Thin films of vanadium oxide grown on vanadium metal: oxidation conditions to produce V2O5 films for Li‐intercalation applications and characterisation by XPS,AFM, RBS/NRA

Thin films of vanadium oxide were grown on vanadium metal surfaces (i) in air at ambient conditions, (ii) in 5 mM H₂SO₄ (aq), pH 3, (iii) by thermal oxidation at low oxygen pressure (10^?5 mbar) at temperatures between 350 and 550 °C and (iv) at near‐atmospheric oxygen pressure (750 mbar) at 500 °C. The oxide films were investigated by atomic force microscopy (AFM), X‐ray photoelectron spectroscopy (XPS), X‐Ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). The lithium intercalation properties were studied by cyclic voltammetry (CV). The results show that the oxide films formed in air at room temperature (RT), in acidic aqueous solution, and at low oxygen pressure at elevated temperatures are composed of V₂O₃. In air and in aqueous solution at RT, the oxide films are ultra‐thin and hydroxylated. At 500 °C, nearly atmospheric oxygen pressure is required to form crystalline V₂O₅ films. The oxide films grown at pO₂ = 750 mbar for 5 min are about 260‐nm thick, and consist of a 115‐nm outer layer of crystalline V₂O₅. The inner oxide is mainly composed of VO₂. For all high temperature oxidations, the oxygen diffusion from the oxide film into the metal matrix was considerable. The oxygen saturation of the metal at 450 °C was found, by XPS, to be 27 at.% at the oxide/metal interface. The well‐crystallized V₂O₅ film, formed by oxidation for 5 min at 500 °C and 750 mbar O₂, was shown to have good lithium intercalation properties and is a promising candidate as electrode material in lithium batteries. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of two-dimensional gallium nitride via spin coating method: influences of nitridation temperatures

This paper reports the synthesis and characterization of gallium nitride (GaN) thin films deposited on p-type silicon (100) substrates by using low cost spin coating method under various nitridation temperatures. This work demonstrated that spin coating with the new prepared precursor solution can be used as a versatile method for the successfully growth of GaN thin films. Furthermore, the influence of varying nitridation temperatures on the structural, morphological, and optical properties of synthesized GaN thin films were studied in this work. The GaN thin films were characterized by X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, photoluminescence and Raman spectroscopy. All the characteristics of the GaN thin films were effectively improved with the increasing of the nitridation temperatures from 750 to 950 °C and degraded at temperature of 1,050 °C. The measured results show that nitridation temperature plays an important role in improving the crystalline quality of the GaN thin films and the most efficient nitridation temperature was at 950 °C.