IR and x-ray studies of ion-beam-synthesized aluminium nitride films

IR transmission spectroscopy in conjunction with X-ray diffraction was used to characterize the phase composition of aluminium films after nitrogen ion implantation. Aluminium films deposited onto single-crystal silicon and implanted with 30 keV nitrogen ions (¹⁴N₂⁺) to a dose of 10¹⁷-10¹⁸ ions cm^-2 were subsequently characterized for aluminium nitride (AIN) formation by IR spectroscopy. The formation of a stoichiometric AIN layer was evident from the IR absorption band observed at 648 cm^-1. Furthermore, X-ray diffraction of an aluminium foil after nitrogen implantation at 110 keV to a dose of 5.0 × 10¹⁷ ions cm^-2 on each side revealed the presence of a polycrystalline AIN phase. A thermal treatment at 700°C did not yield any new crystalline phases.     

Fabrication of nanostructured α-Fe2O3 electrodes using ferrocene for solar hydrogen generation

Nanostructured thin films of α-Fe₂O₃ were prepared through atmospheric chemical vapour deposition (APCVD) using ferrocene and iron pentacarbonyl as precursors. Higher optical absorption was observed for hematite films prepared using ferrocene, which was attributed to the higher packing density. Photoelectrochemical (PEC) studies of the films prepared using ferrocene showed superior performance to that of iron pentacarbonyl. Photocurrent density of 540 µA/cm² and 1.5 µA/cm² at 1.23 V_RHE was achieved for hematite films prepared using ferrocene and iron pentacarbonyl, respectively. Our findings suggest that ferrocene can be used as a promising alternative to iron pentacarbonyl to prepare hematite photoelectrodes using APCVD.     

Reaction of Al/Mo thin films

Intermixing and compound formation by means of annealing have been studied for Al/Mo thin films. With annealing at 300° C, only intermixing between aluminium and molybdenum films occurs due to mutual diffusion. With annealing at over 350° C, Al₁₂Mo and AlMo₃ compounds were formed. The electrical resistivity of the film increases with intermixing and compound formation. The electrical resistivity increase is proportional to the annealing time,t ^1/2. In low vacuum annealing, molybdenum oxide film forms on aluminium film. It is assumed that molybdenum atoms diffuse through the aluminium film due to their chemical affinity with oxygen in the atmosphere.     

Chemical/mechanical polishing of diamond films assisted by molten mixture of LiNO3 and KNO3

Chemical/mechanical polishing can be used to polish the rough surface of diamond films prepared by chemical vapor deposition (CVD). In this paper, a mixture of oxidizing agents (LiNO₃ + KNO₃) has been introduced to improve the material removal rate and the surface roughness in chemical/mechanical polishing because of its lower melting point. It had been shown that by using this mixture the surface roughness R_a (arithmetic average roughness) could be reduced from 8-17 to 0.4 μm in 3 h of polishing, and the material removal rate can reach 1.7-2.3 mg/cm²/h at the temperature of 623 K. Pure aluminium is compared with cast iron as the contact disk material in the polishing. Although the material removal rate of aluminiumdisk is lower than that of cast iron, it can eliminate the carbon contamination from the contact disk to the surface of diamond films, and facilitate the analysis of the status of diamond in the chemical/mechanical polishing. The surface character and material removal rate of diamond films under different polishing pressure and rotating speed have also been studied. Graphite and amorphous carbon were detected on the surface of polished diamond films by Raman spectroscopy. It has been found that the oxidization and graphitization combined with mechanical cracking account for the high material removal rate in chemical/mechanical polishing of diamond films.     

Preparation of SiO2 films from Si(OC2H5)4-C2H5OH-H2O solutions without catalysts

Thin and homogeneous SiO₂ films were prepared on aluminium plates from Si(OC₂H₅)₄-C₂H₅OH-H₂O solutions which had controlled compositions and did not contain any acid as a catalyst. Aluminium with the coatings showed good corrosion resistance. However, SiO₂ films prepared from alkoxide solutions with HCI contained Cl^– ions. Aluminium with coatings including Cl^– ions corroded in a corrosion test. Alkoxide solutions without acids were necessary for use in the coating of aluminium. The transformation of gels prepared from solutions without acids to amorphous SiO₂ was investigated.     

The thermal reactions of muscovite studied by high-resolution solid-state 29-Si and 27-AI NMR

Studies of two muscovites of different iron contents, using solid-state NMR with magic-angle-spinning (MAS) combined with X-ray powder diffraction, thermal analysis and⁵⁷Fe Mössbauer spectroscopy, suggest that dehydroxylation occurs by a homogeneous rather than an inhomogeneous mechanism, forming a dehydroxylate in which the aluminium is predominantly 5-coordinate. On further decomposition at about 1100° C, the tetrahedral layer and interlayer K⁺ form a feldspar-like phase similar to leucite (KAISi₂O₆), the remainder forming a spinel, which, contrary to previous suggestions, appears to contain little silicon. Further heating induces the formation of mullite (AI₆Si₂OP₁₃), and, in the higher-iron sample, corundum (-Al₂O₃), in addition to the feldspar-like phase. The presence of the iron impurity enhances the recrystallization reactions and promotes the conversion of mullite to corundum, which eventually becomes the sole aluminous product in the high-iron sample. In samples fired to higher temperatures, only the tetrahedral aluminium resonance is detectable by²⁷AI NMR, probably because most of the iron is located in either the mullite or corundum phases, in which it broadens the octahedral aluminium resonance beyond detection.     

Reactive deposition of Al-N coatings in Ar/N2 atmospheres using pulsed-DC or high power impulse magnetron sputtering discharges

In this paper, the metal to ceramic transition of the Al-N₂ system was investigated using classical reactive pulsed-DC magnetron sputtering and HIgh Power Impulse Magnetron Sputtering (HIPIMS) at a constant average current of 3 A. Optical emission spectroscopy measurements revealed more ionised aluminium species in the HIPIMS discharge compared to pulsed-DC sputtering. It also showed excited N⁰ and ionised N⁺ species in reactive Ar/N₂ HIPIMS discharges. The corresponding evolution of the consumed nitrogen flow as a function of the N₂ partial pressure revealed that a higher amount of reactive gas is needed to achieve stoichiometric AlN with HIPIMS. Electron probe micro-analysis and X-ray diffraction measurements confirmed that a partially poisoned aluminium target is enough to allow the deposition of stoichiometric hcp-AlN thin films via HIPIMS. To go further in the comparison of both processes, two stoichiometric hexagonal aluminium nitride thin films have been deposited. High power impulse magnetron sputtered hcp-AlN exhibits a higher nano-hardness (18 GPa) than that of the coating realised with conventional pulsed-DC sputtering (8 GPa).     

Electrochemical properties of dielectric films of aluminium oxide deposited on silicon

Chemical, physical and some electrical properties of aluminium oxide dielectric films deposited on silicon substrates are reported. In the growth of these films we utilized the vapour phase reaction of the hydrolysis of aluminium trichloride (AlCl₃) in an r.f. heated horizontal reactor tube to give films of good thickness uniformity and run-to-run consistency. The activation energies associated with the constituent components of this complex chemical reaction were determined. It is shown that the films exhibit high dielectric constant (7.7±0.2) and field strength (in excess of 6 × 10⁶ V cm^?1) with low ionic content (typically anout 10¹⁰ cm^?2), making them an attractive contender for passivation and for use as the gate dielectric of metal-insulator-semiconductor (MIS) devices.     

Chemical synthesis of α-iron in aqueous FeCl3

Iron-aluminium composite and α-iron powder have been prepared by chemical reduction of aqueous FeCl₃ with aluminium at different conditions. Experiments showed that the concentration of FeCl₃ and aluminium particle size are the main factors to influence the reaction. XRD, SEM and potentiometric titration were employed to characterize the products. SEM showed that as iron particles grow they tend to form spherical seed on the surface of aluminium. XRD revealed that the α-iron was single phase after deposit treatment by NaOH solution. The purity of as-prepared α-iron was 99.5%, as determined from the X-ray fluorescence spectroscopy. The possible formation mechanism is a two-stage red-ox-process: Fe³⁺→Fe²⁺→α-Fe.     

Influence of substrate temperature on the structural and electrical properties of α-Fe2O3 films prepared by ultrasonic spray pyrolysis

Iron oxide films were prepared by ultrasonic spray pyrolysis (USP) on SiO₂ coated Si wafers using iron acetylacetonate as an iron precursor. The crystallographic properties and surface morphologies of the films were characterized by X-ray diffraction and scanning electron microscopy, respectively. X-ray photoelectron spectroscopy (XPS) was carried out to determine the Fe oxidation states. The satellite peak associated with Fe³⁺ photoemission at a binding energy of 719 eV was detected in the XPS results for iron oxide films, which is one of the indications of the Fe₂O₃ composition. The as-deposited films exhibit a polycrystalline -Fe₂O₃ structure. In order to observe thermal stability of the films, the resistance variation with ambient temperature was measured. All the iron oxide films deposited in this experiment were found to be -Fe₂O₃ with the thermal stability lower than 2%/ °C.     

Effect of iron particle addition on the pseudocapacitive performance of sol–gel derived manganese oxides film

Manganese oxide electrodes with promising behavior were prepared successfully by sol–gel process. Manganese oxide films were also modified with the addition of submicron-crystalline iron powders. Effects of post heat treatment and iron submicron-powder addition on the material characteristics and electrochemical capacitance of the manganese oxide electrodes were investigated. The experimental results showed that manganese oxide films composed from metal-organic precursors at 250 °C heat treatment, while formation of MnO₂, Mn₂O₃, Mn₃O₄, Fe₂O₃, and Fe₃O₄ phases were observed after heat treatment at a temperature higher than 300 °C. The specific capacitances were 48.9, 140.1, 212.7, and 81.1 F g⁻¹ for manganese oxide films heat treated at 250, 300, 350, and 400 °C, respectively. The specific capacitances were 75.7, 227.3, 247.9, and 152.9 F g⁻¹ for manganese/iron oxide films (Mn:Fe = 100:1) heat treated at 250, 300, 350, and 400 °C, respectively. The manganese/iron oxide films (Mn:Fe = 100:1) treated at 350 °C exhibited the highest specific capacitance 247.9 F g⁻¹ of the electrodes investigated in the present study. After 1000 cyclic voltammetry tests, the specific capacitance decreased by only 10 percent. The surface morphology of this film exhibited powders with linked nano-sized particles. The number of special particles reached a maximum after heat treatment at 350 °C. The experimental results showed that post heat treatment and iron submicron-particle addition may change the surface morphology and structure, increase the specific capacitance, and improve the electrochemical performances of the manganese oxide electrodes.     

Preparation and photoluminescence of Er-doped Al2O3 films by sol-gel method

The 0-1.5 mol% Er³⁺-doped Al₂O₃ films have been prepared on the thermally oxidized SiO₂/Si(100) substrate in the dip-coating process by the sol-gel method, using the aluminium isopropoxide [Al(OC₃H₇)₃]-derived γ-AlOOH sols with the addition of erbium nitrate [Er(NO₃)₃·5H₂O]. The continuous Er³⁺-doped Al₂O₃ films with the thickness of about 1.2 μm were obtained for nine coating cycles at a sintering temperature of 900 °C. The aggregate size for the Er³⁺-doped Al₂O₃ films increased with increasing the Er³⁺ doping concentration from 0 to 1.5 mol%. The root-mean-square roughness of the films was independent on the Er³⁺ doping, which was about 1.8 nm for the 0-1.5 mol% Er³⁺-doped Al₂O₃ films. The γ-Al₂O₃ phase with a (110) preferred orientation was produced for the Al₂O₃ film. The photoluminescence (PL) spectra of 0.1-1.5 mol% Er³⁺-doped Al₂O₃ films were observed at the measurement temperature of 10 K. There was no significant change for the PL peak intensity with the increase of Er³⁺ doping concentration from 0.1 to 1.5 mol%, and similar full width at half maximum of about 40 nm was detected for the 0.1-1.5 mol% Er³⁺-doped Al₂O₃ thin films. The Er³⁺-doped Al₂O₃ films possess the available PL properties for use in planar optical waveguides.     

Structure and morphology of TiB2 duplex coatings deposited over X40 CrMoV 5-1-1 steel by DC magnetron sputtering

The deposition of titanium diboride (TiB₂) films over tool steel substrates (AISI H13 premium/EN X40 CrMoV 5-1-1) is being investigated due to its excellent corrosion resistance and chemical stability against liquid aluminium. The use of nitrided steels as substrates for TiB₂ deposition may contribute to increase its adhesion and the overall steel resistance in applications such as forging, extrusion and die casting of aluminium. Duplex coatings were obtained by the PVD deposition of TiB₂ films over heat treated and nitrided steel using non-reactive DC magnetron sputtering from a TiB₂ target, varying the substrate bias voltage. Well structured and crystalline TiB₂ films were obtained for the selected deposition conditions, the best crystalline coatings being obtained for the positively biased substrates. Selected films produced over die-casting pins at a bias voltage of +50 V were tested for resistance to liquid aluminium soldering by immersion tests, and compared with the nitrided steel. The duplex TiB₂ coating has a much larger chemical resistance to attack by molten aluminium alloy than the just nitrided steel. Where there is soldering, steel is rapidly attacked and a complex Al-Fe-Si intermetallic forms.     

Nonlinear optical properties of thin iron films grown on MgO (100) by pulsed laser deposition

Thin films of iron were fabricated on MgO (100) substrates using pulsed laser deposition technique. The crystalline property and surface roughness of the films were investigated by X-ray diffraction and atomic force microscopy, respectively. It was found that the morphology of the Fe film deposited at room temperature was characteristic of continuous metal film. Increasing the deposition temperature caused the smooth Fe film to break up, and nanoscale Fe islands were formed. We performed the z-scan measurements to study the third-order optical nonlinearity of the continuous approximately 9-nm-thick iron film. The results show that the ultrathin iron film exhibits large nonlinear refractive coefficient, n₂=7.09×10⁻⁵ cm²/kW, and nonlinear absorption coefficient, β=−5.52×10⁻³ (cm/W), at the wavelength of 532 nm.     

Angular distribution and sputtering yield of Al and Al2O3 during 40 key argon ion bombardment

The angular distribution and sputtering yield of Al and Al₂O₃ during 40 keV argon ion bombardment have been measured by collecting the sputtered particles on a semi-cylindrical collector and analysing them by Rutherford backscattering spectrometry (RBS). It was found that due to the relatively high residual pressures (1–4 · 1O^?4Pa) in the sputtering chamber not only aluminium but also oxygen atoms are deposited on the collector through the mechanism of reactive sputtering both when sputtering the oxide and the metal target. The angular distribution of the collected aluminium and oxygen atoms in the case of pure aluminium sputtering follows a cosine law while in the case of Al₂O₃ sputtering a considerable deviation from the cosine law is observed. This deviation is explained by a preferred orientation (texture) of the crystallites in the polycrystalline oxide targets. It was found that the very thin films deposited on the collector when sputtering both types of targets have a composition close to AlO₂. The sputtering yield of Al and Al₂O₃ by 40 keV argon ions has been determined. On the basis of the obtained values an estimation of the productivity of the reactive sputter deposition of Al₂O₃ films from oxidized and non-oxidized targets is made.     

Electron microscopy observations of N2+ -implanted TiN films as diffusion barriers for very-large-scale integration applications

Titanium nitride films were prepared by implanting 40keV N₂⁺ ions into Si〈100〉n⁺/p shallow junctions coated with titanium layers of different thicknesses (from 80 up to 100nm). Using a suitable thermal annealing a film of TiSi₂ is formed at the TiN-Si interface, as demonstrated by transmission electron microscopy (TEM) observations on planar and cross-sectioned specimens, as well as by Rutherford backscattering spectrometry experiments. The effectiveness of these TiN films as diffusion barriers when placed in contact with a thick aluminium overlayer is evaluated, and their electrical performances are tested on suitable test patterns after thermal treatments up to 600°C. The variation in the structure of the interfaces in the TiSi₂/TiN/Al contacts is followed as a function of the heat treatment by cross-sectional TEM investigations and the results are presented.     

Microanalyses of chemically etched thin film alumina-ferrite interfaces

Thin films of aluminium oxide were deposited on ferrite (Ni _x Zn_1−x Fe₂O₄) substrates by r.f. sputtering. The sputtered alumina films were not easily etched by hot phosphoric acid unlike readily etchable films prepared by physical deposition techniques. Microanalytical characterization of unetched films, partially etched films and interfacial regions was conducted to identify the microscopic features responsible for reluctant film etchability. The post-etched films were categorized as easily, partially and un-etchable (EE, PE and U respectively) and were examined using optical microscopy, SEM, XRD, EDS, XPS, AES, and TEM/STEM. TEM examination of cross-sections of partially etchable films revealed a non-uniform crystalline phase at the film-substrate interface. Electron diffraction data identified the phase asη-alumina although AES and EDS results suggest that the interfacial phase also contained some iron. The occurrence and orientation of theη-alumina phase was shown to depend on the orientation of the grains of the ferrite substrate.     

γ-Irradiation effect on the trap-hopping conductivity of thin film SiO2-Si3N4 structures

The a.c. properties of r.f. sputtered aluminium fluoride metal-insulator-metal capacitors were measured at different temperatures in the range 103–423 K and at various frequencies between 10² Hz and 10⁶ Hz. The capacitance of the specimens varied slightly with frequency and temperature. Both the capacitance and loss tangent of freshly prepared samples tended to be larger before the first heating cycle was initiated but attained a constant value after three or four heating cycles. The relative permittivity (?_r = 2.8) was found to be smaller than that for thermally evaporated AlF₃ films, indicating that the sputtered films were more highly amorphous.Tha activation energy of the conduction mechanism in the temperature range 103–273 K was found to be 0.0018 eV while that at higher temperatures was 0.068 eV. The plot of tan δ versus frequency showed a minimum with tan δ_min shifting towards higher frequencies as the temperature was increased. The conductance varied as fⁿ where n had the value 0.85 in the low frequency low temperature range and the value 2 in the high frequency high temperature region.The sputtered AlF₃ films showed a lower value of loss tangent and less temperature dependence of permittivity than thermally prepared samples.     

Preparation of Fe2O3/Al composite powders by homogeneous precipitation method

The Fe₂O₃/Al composite powders were prepared by homogeneous precipitation method. The influence of the concentration of Fe²⁺ and the molar ratio of raw materials on the preparation of Fe₂O₃/Al composite powders were investigated. X-ray diffractometer, scanning electron microscope, Fourier transform infrared spectroscopy and differential thermal analysis were used to analyze the morphology and structure of the Fe₂O₃/Al composite powders. The results show that the content of iron oxide in the composite powders could be effectively controlled by adjusting the concentration of Fe²⁺ and the molar ratio of raw materials in the plating solution. The surface of Al particle was coated with a layer of thick and dense iron oxide. The core-shell Fe₂O₃/Al composite powders with Fe₂O₃ content of 14.1% were produced, the coating efficiency of Fe₂O₃ reaches more than 77%. The iron oxide, which coated on the surface of the aluminium particle is flower-like cluster structure, each flower-like cluster is constituted by nano-flaky iron oxide.     

Hydrothermal growth of ferromagnetic Fe-doped TiO2 films

Polycrystalline Fe-doped TiO₂ anatase films were deposited on (001) oriented SrTiO₃ single crystal substrates at temperatures less than 200 °C from acidic aqueous solutions of titanyl sulfate and iron (III) nitrate. Epitaxial anatase TiO₂ films were obtained when the films were annealed in air at 900 °C. Room-temperature ferromagnetic Fe-doped TiO₂ thin films were obtained after repeated deposition and annealing steps. The observed saturation magnetization (>0.28μ_B/Fe) could not be attributed to the presence of secondary phase magnetic iron oxides or iron clusters.