Low Vacuum Deposition of Aluminum Nitride Thin Films by Sputtering

Conventionally, sputtering deposition of thin films requires a low base pressure (high vacuum) to minimize influences of residual gases. Here, a high base pressure (low vacuum) was used, which can reduce significantly the overall processing time. Aluminum nitride ( AlN ) was selected as a model system of dielectric nitrides. All the analyses revealed that the obtained films under a low vacuum environment within specific processing windows exhibited characteristics similar to those of high‐vacuum made AlN films. Such a low vacuum deposition technique takes advantages of kinetically favorable formation of the nitride films and hence, has great potentials in many more technological applications.     

Interfacial Reaction between Titanium Thin Films and Aluminum Nitride Substrates

Interdiffusion and reaction at the interface between titanium thin films and AlN have been studied by using Rutherford backscattering spectrometry and transmission electron microscopy. Ti₂AlN is formed as a result of reaction with titanium and AlN at temperatures of 800°-950°C. The activation energy for Ti₂AlN formation in the temperature range of 800°-850°C is 224 kJ/mol, which is similar to that of nitrogen diffusion in titanium. Therefore, the formation of Ti₂AlN is believed to be controlled by the diffusion of nitrogen in titanium.     

Preparation of Highly Oriented Aluminum Nitride Thin Films on Polycrystalline Substrates by Helicon Plasma Sputtering and Annealing

Highly c -axis-oriented aluminum nitride (AlN) thin films were prepared on polycrystalline Si₃N₄ and SiC substrates by helicon plasma sputtering. The difference in the substrate materials scarcely influenced the crystal structures of the films. The full width at half-maximum (FWHM) of the X-ray rocking curves of the films was 3.2°, which is the smallest value for AlN thin films deposited on polycrystalline substrates to our knowledge. Annealing at 800°C in vacuum decreased the FWHM from 3.2° to 2.8°. The structure of the films was densely packed and consisted of many fibrous grains. The films developed c -axis orientation on the polycrystalline substrates, because the interaction between the films and substrate surfaces was small, and (100) and (110) AlN planes grew preferentially. The films were piezoelectric and generated electrical signals in response to mechanical stress.     

Adhesion Between Plasma-Treated Polypropylene Films and Thin Aluminum Films

Polypropylene (PP) film was treated with radio-frequency-induced oxygen plasma, followed by the vacuum deposition of aluminum (Al) thin film, and the peel strength of the Al deposited PP film (Al/PP) was examined. The peel strength of plasma-treated PP film varied widely in the range of 6.7 to 157 N/m depending upon the plasma treatment conditions, whereas that of the untreated PP was 5.2 N/m. The peel strength was minimized at oxygen pressure near 13.3 Pa (0.1 Torr), and decreased with increasing discharge power. The peel strength rapidly increased at the initial stage of plasma treatment (∼ several seconds), decreased at the second stage, and slightly increased again at the third stage. A good agreement was found between the peel strength of Al/PP and the amounts of oxygen introduced onto the PP surface at the initial stage. A short-time treatment was very effective to improve the adhesion of Al/PP. At the end of the second stage, a large amount of carbon was detected by XPS on the Al layer of the peeled interface of Al/PP, which gave a minimum peel strength. Cohesive failure of PP film might have occurred. SEM photograph showed that PP surface was etched by oxygen plasma at the thrid stage. These peel behaviors of Al/PP were explained by the chemical and physical changes of the PP surface caused by oxygen plasma treatment: (1) introduction of O-functional groups onto the PP surface at the initial stage, (2) formation of weak booundary layers resulting from the partial scission of PP molecules at the second stage, and (3) plasma etching of the PP surface at the third stage.     

Suppressing the Formation of Cone Structures in Chemical-Vapor-Deposited Aluminum Nitride/Titanium Nitride Films

Cone structures are sometimes observed in aluminum nitride/titanium nitride (AIN/TiN) composite films formed by chemical vapor deposition (CVD). In this study, we determined the formation mechanism of cone structures by looking at such films deposited on Si substrates. We found that the mechanism can be explained by changes in the deposition rate due to composition differences in the growing surfaces, rather than by inhomogeneities in the original substrate surface. We then used this discovery to develop a technique to suppress cone structure formation, i. e., deposition of an interlayer before the deposition of the composite. To validate our technique, we then successfully suppressed the formation of cone structures in AIN/TiN films by depositing a TiN interlayer on the substrate before the deposition of AIN/TiN.     

Antibacterial Thin Films on Glass Substrate by Sol–Gel Process

Antibacterial transparent thin films, containing different amounts of silver ion, have been prepared on a glass substrate by the sol–gel process. Thin films were obtained from inorganic-organic hybrid sols derived from 3-(glicydiloxypropyl)trimethoxy silane, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane and aluminium-sec-butoxide/ethylaceto-acetate complex and doped with silver ions. The films were characterized by Scanning Electron Microscopy and Raman Spectroscopy. The physical properties of the films were studied by solar-box, taber abraser, hardness test pencil, scratch-adhesion test and spectroscopy. The antibacterial activity of the coatings were investigated against gram negative Escherichia coli and gram positive Staphylococcus aureus. The results showed that 1% doping of the transparent hybrid thin film with silver ions resulted in high antibacterial properties of the film.     

Investigation on Molybdenum Thin Films Deposited by DC-Sputtering on Polyethylene Terephthalate Substrate

Molybdenum (Mo) films were prepared by DC sputtering on a polyethylene terephthalate (PET) substrate with different thicknesses. The molybdenum finds use in a very broad spectrum of applications in widely different forms. The obtained results of thin films of molybdenum deposited on PET are characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD) and (EDX). It was found that the thickness increases with the time of deposition and reduces the resistivity and sheet resistance. The lowest resistivity value we found for the Mo films was 1.3 × 10^?5 Ω · cm at thickness (210 nm).     

Thin Copper, Gold, and Aluminum Films on Silicate Glass

The composition and structure of thin copper, gold, and aluminum films deposited on a substrate made of vitreous quartz are investigated. The composition of the film – substrate interfaces is analyzed.     

Growth of Oxide Layers on Thin Aluminum Nitride Samples Measured by Electron Energy-Loss Spectroscopy

AlN ceramics with different amounts of oxygen impurities were investigated by electron energy-loss Spectroscopy (EELS). Because of the high dynamics of EEL spectra, a method was developed to record partial spectra and then to join them together to form a complete spectrum. The data obtained from EEL spectra were the nitrogen/oxygen concentration ratio, sample thickness, and energy-loss nearedge structures (ELNES). Because of spontaneous formation of an oxide layer on AlN samples immediately after ion milling, a method had to be developed which yielded the oxide layer thickness and the bulk oxygen content. The growth kinetics of the oxide layer were investigated by exposing the AIN samples at room temperature to air and to water for various times. From these measurements a logarithmic rate law for the oxidation of AlN at room temperature was obtained.     

Ceramics Based on Aluminum Nitride

The results of studying the effect of Y₂O₃and CaO additives introduced into ceramic mixtures in the form of oxides and salts on sintering and properties of AlN-based ceramics are discussed. The effect of high-temperature annealing of ceramics in a mixture of nitrogen and hydrogen on its properties is specified.     

Composite Coatings Based on Aluminum Nitride and an Organic Binder

Results for a special mixture, composed of AlN and a thermoreactive binder (a liquid phenol-formaldehyde resin) and tested for thermal destruction are presented. The inert AlN increases corrosion stability of the mixture and imparts the needed physicochemical properties to the material.     

PECVD制备富硅氮化硅薄膜的工艺条件及其性质的研究

采用等离子体增强化学气相沉积法(PECVD)以SiH4和N2为反应气体,分别在射频功率、硅烷稀释度[SiH4/N2]、衬底温度为变量的情况下制备了富硅氮化硅薄膜材料,利用X射线衍射谱(XRD)、傅里叶变换红外谱(FTIR)、紫外-可见光吸收谱(UV-Vis)对薄膜材料进行了表征,并研究了薄膜材料的微结构和晶化状况、光学特性等.实验结果表明,所沉积薄膜都为富硅的非晶氮化硅材料,改变射频功率、硅烷稀释度和衬底温度可以控制氮化硅薄膜中N元素的含量、光学带隙的大小和薄膜的折射率,并制备出最适宜富硅氮化硅薄膜,为进一步退火析出硅量子点奠定了基础.     

Composition and Microstructure of Chemically Vapor-Deposited Boron Nitride, Aluminum Nitride, and Boron Nitride + Aluminum Nitride Composites

The composition and microstructure of dispersed-phase ceramic composites containing BN and AIN as well as BN and AIN single-phase ceramics prepared by chemical vapor deposition have been characterized using X-ray diffraction, scanning electron microscopy, electron microprobe, and transmission electron microscopy techniques. Under certain processing conditions, the codeposited coating microstructure consists of small single-crystal AIN fibers (whiskers) surrounded by a turbostratic BN matrix. Other processing conditions resulted in single-phase films of AIN with a fibrous structure. The compositions of the codeposits range from 2 to 50 mol% BN, 50 to 80 mol% AIN with 7% to 25% oxygen impurity as determined by electron microprobe analysis.     

Degradation of Aluminum Nitride Powder in an Aqueous Environmet

The degradation of A1N powder in excess H₂O at room temperature for up to 24 h was investigated. Samples were characterized by various techniques (IR; XRD; SEM; XPS; C, H, N analysis; surface area, particle size, and weight change measurements). The reaction rate was found to be significant, with 80% of the A1N being consumed in 24 h. The initial reaction product was found to be a porous, amorphous, hydrated alumina with stoichiometry near AlOOH. After ∽16 h a crystalline phase, bayerite Al(OH)₃, was detected which became the predominant phase after 24-h contact. The kinetics of the A1N consumption were found to be first order and the reaction rate linear. The kinetic data fitted an unreacted core model with a porous product layer where the surface chemical reaction controlled the overall kinetics.     

Photoluminescence from Boron-Doped Titanium Nitride Nanocomposite Thin Films Prepared by the Magnetron Sputtering Method

Boron-doped titanium nitride (TiBN) thin films with nanosized grains were prepared by a magnetron sputtering method. X-ray diffraction and transmission electron microscopy observation indicated that TiBN thin films have a cubic structure with grains ∼5 nm in size. The photoluminescence (PL) of the films was investigated as a function of temperature over a wavelength range of 350–900 nm. Two PL peaks near 3.20 and 2.38 eV were conisdered to have resulted from the recombination of the donor-bound excitons and deep-trap defects with the holes in the valence band, respectively. An energy transfer from bound electrons to deep-trap defects was observed in the nanocomposite thin film.     

The Crystallization of Amorphous Aluminum Oxide Thin Films Grown on NiAl(100)

The crystallization of amorphous aluminum oxide thin films formed on NiAl(100) has been investigated using in‐situ low energy electron microscopy, low energy electron diffraction, and scanning tunneling microscopy. It is found that both the annealing temperature and annealing time play crucial roles in the crystallization process. A critical temperature range of 450°C–500°C exists for the crystallization to occur within a reasonably short annealing time. The initially uniform oxide film first becomes roughened, followed by coalescing into amorphous‐like oxide islands; further annealing results in the conversion of the amorphous oxide islands into crystalline oxide stripes. The density of the crystalline oxide stripes increases concomitantly with the decrease in the density of the amorphous oxide islands for annealing at a higher temperature or longer time.     

Epitaxial Aluminum-Doped Zinc Oxide Thin Films on Sapphire: I, Effect of Substrate Orientation

Epitaxial thin films of Al-doped zinc oxide have been grown on sapphire substrates by pulsed laser ablation. The effect of substrate temperature, background pressure of oxygen, and substrate orientation (A, M, R, C) on the orientation relationships between ZnO and sapphire have been evaluated using on- and off-axis X-ray diffractometry. Under all growth conditions zinc oxide, on A- and C-plane sapphire, grew with the c -axis perpendicular to the substrate. In contrast, on M and R orientations of sapphire, ZnO grew with its c -axis parallel or perpendicular to the substrate depending on the substrate temperature and background pressure employed during growth. In all cases only one unique in-plane relationship between the sapphire substrate and the zinc oxide film was found with the exception of the M-plane at high substrate temperatures.     

Intrinsic Disorder in Aluminum Nitride

An interatomic potential model is developed for aluminum nitride and is used in conjunction with atomistic computer simulation methods to obtain the energies of intrinsic point defects. These energies are found to be very high, indicating no significant intrinsic disorder, even close to the melting point. Interstitial formation is particularly unfavorable, suggesting that these species will play no part in defect-controlled processes in AlN.