Effect of microstructure on degradation of AlN films prepared by ion beam assisted deposition

Two kinds of aluminum nitride (AlN) films were prepared by ion beam assisted deposition (IBAD) by changing the nitrogen ion beam energy; one was deposited with a 0.2 keV ion beam, showing a columnar structure, and the other was deposited with a 1.5 keV ion beam, showing a granular structure. The effect of microstructure on degradation of AlN films was studied by immersing them in aqueous HNO₃, HCl, and NaOH solutions at room temperature. Degradation was examined mainly in terms of changes in optical transmittance and surface morphology. After immersion in HNO₃ and HCl solutions, the average transmittance of the columnar film decreased gradually from the beginning of immersion, while that of the granular film maintained the initial level of transmittance for about 60 h immersion in HNO₃ solution and about 80 h immersion in HCl solution. In NaOH solution, both films were detached readily from the substrate and no remarkable difference in the degradation behavior was observed between the two films. It is concluded that the IBAD AlN films with the granular structure show higher durability against aqueous acid solutions than the films with the columnar structure.     

The effect of the ion beam energy on the properties of indium tin oxide thin films prepared by ion beam assisted deposition

Indium tin oxide (ITO) thin films have been deposited onto polycarbonate substrates by ion beam assisted deposition technique at room temperature. The structural, optical and electrical properties of the films have been characterized by X-ray diffraction, atomic force microscopy, optical transmittance, ellipsometric and Hall effect measurements. The effect of the ion beam energy on the properties of the films has been studied. The optical parameters have been obtained by fitting the ellipsometric spectra. It has been found that high quality ITO film (low electrical resistivity and high optical transmittance) can be obtained at low ion beam energy. In addition, the ITO film prepared at low ion beam energy gives a high reflectance in IR region that is useful for some electromagnetic wave shielding applications.     

Texture evolution of transition-metal nitride thin films by ion beam assisted deposition

TiN, VN and CrN were systematically deposited on silicon substrates using ion beam assisted deposition (IBAD) technique at temperatures and ion (N₂⁺) energy ranging from 300 °C to 500 °C and 100 eV to 650 eV, respectively. The results showed that the texture could be controlled by the ion beam energy, flux, and its incident angle, in conjunction with the deposition temperature. For the 0° angle of ion incidence, fiber textures were formed and could be controlled between (111) and (200) surface plane orientation by adjusting ion flux or ion energy. Three types of in-plane textures were produced, when the ion beam was incident at 45° angle, for which cases ion channeling played an important role in the formation of in-plane texture. Using the strain-energy perturbation method, the stability of texture can be further understood. Among the three in-plane textures, the (200) in-plane texture is strain-energy stable, and the others are not.     

A study of silicon oxynitride film prepared by ion beam assisted deposition

A SOI-based optoelectronic device needs a high-quality antireflection coating on both faces of the device to minimize the optical reflectance from the face. In this work amorphous silicon oxynitride films were deposited on silicon substrates by ion beam assisted deposition (IBAD). The main purpose was to use silicon oxynitride film as single layer anti-reflection coating for SOI-based optoelectronic devices. This application is primarily based on the ability to tune the silicon oxynitride optical functions to the optimal values by changing deposition parameters. The chemical information was measured by X-ray photoelectron spectroscopy (XPS). Spectroscopic ellipsometry (SE) was applied to measure the refractive index and thickness. Single-side polished silicon substrate that was coated with silicon oxynitride film exhibited low reflectance. Double-side polished silicon substrate that was coated with silicon oxynitride film exhibited high transmittance. In addition, the Fresnel losses could be reduced to 0.08 dB by depositing silicon oxynitride films onto double-side polished silicon substrates. The results suggested silicon oxynitride film was a very attractive single layer anti-reflection coating for SOI-based optoelectronic device.     

Effect of bias voltage on growth property of Cr-DLC film prepared by linear ion beam deposition technique

Cr-containing diamond-like carbon films were deposited on silicon wafers by a combined linear ion beam and DC magnetron sputtering. The influence of the bias voltage on the growth rate, atomic bond structure, surface topography and mechanical properties of the films were investigated by SEM, XPS, Raman spectroscopy, AFM, and nano-indentation. It was shown that the chromium concentration of the films increased with negative bias voltage and that a carbide phase was detected in the as-deposited films. The surface topography of the films evolved from a rough surface with larger hillocks reducing to form a smoother flat surface as the bias voltage increased from 0 to −200 V. The highest hardness and elastic modulus were obtained at a bias voltage of about −50 V, while the maximum sp³ bonding fraction was acquired at −100 V. It was suggested that the mechanical properties of the films not only depended on the sp³ bonding fraction in the films but also correlated with the influence of Cr doping and ion bombardment.     

Deposition of titanium nitride films onto silicon by an ion beam assisted deposition method

Titanium nitride (TiN) films were deposited onto silicon wafers using an ion beam assisted deposition (IBAD) method with an electron cyclotron resonance (ECR) ion source for ionizing the nitrogen (N₂) gas under a condition of high nitrogen ion to titanium neutral ratio. The deposition rate of the TiN films was strongly dependent on the evaporation rate, d_Ti, of Ti metal and decreased with increasing nitrogen ion current. The deposition rate can be approximated as d=βd_Ti?_N2/{1/k+?_N2}−αI, where β, k and α are proportional constants, ?_N2 is the sum rate of neutral and ionized nitrogen impinging onto the substrate, and I is the nitrogen ion current.     

Photocatalytic properties of Cr-doped TiO2 films prepared by oxygen cluster ion beam assisted deposition

We prepared Cr-doped titanium dioxide (TiO₂) films by oxygen (O₂) cluster ion beam assisted deposition method, and investigated photocatalytic properties of the films as well as crystallographic property, optical property and surface morphology. The films prepared at a substrate temperature below 200 °C were found to be amorphous from the X-ray diffraction measurement. For the substrate temperatures such as 300 °C and 400 °C, the films exhibited rutile and/or anatase structures. The film surface measured by the atomic force microscope (AFM) was smooth at an atomic level. Furthermore, the optical band gap decreased with increase of Cr-composition, and it was approximately 3.3 eV for the non-doped films, 3.2 eV for the 1% Cr-doped films and 3.1 eV for the 10% Cr-doped films, respectively. With regard to the photocatalytic properties of the Cr-doped TiO₂ films, we measured the change of contact angle as well as the photocatalytic degradation of methylene blue by the UV light irradiation. Compared with the non-doped films, the 1% Cr-doped films prepared at a substrate temperature of 400 °C showed high degradation efficiency. In addition, the contact angle of the 1% Cr-doped films with an initial value of 60° decreased to 10° by the UV light irradiation for 20 min, and the films exhibited the predominant properties of photocatalytic hydrophilicity even for the UV light irradiation with longer wavelengths.     

Improved stability of organic light-emitting diode with aluminum cathodes prepared by ion beam assisted deposition

We have fabricated highly stable organic electroluminescent devices based on spin-coated poly-p-phenylene-vynylene (PPV) thin films. The electrical properties of aluminum cathode, prepared by ion beam assisted deposition, on PPV have been investigated and compared to those by thermal evaporation. Although energetic particles of Al assisted by Ar⁺ ion may damage the organic material, I–V–L characteristics are improved by applying thin Al buffer layer. In addition, a dense Al cathode inhibits the permeation of H₂O and O₂ into PPV film through pinhole defects, and thus retards dark spot growth. It may be deduced from highly packed structure of Al cathode with an increase in the contact area between Al and PPV that reduce the contact resistance. In conclusion, the lifetime of organic light-emitting device (OLED) has been extended effectively by dense Al film through ion beam assisted deposition process.     

Effect of the oxygen flow on the properties of ITO thin films deposited by ion beam assisted deposition (IBAD)

ITO films were deposited onto glass substrates by ion beam assisted deposition method. The oxygen ions were produced using a Kaufman ion source. The oxygen flow was varied from 20 until 60 sccm and the effect of the oxygen flow on properties of ITO films has been studied. The structural properties of the film were characterized by X-ray diffraction and atomic force microscopy. The optical properties were characterized by optical transmission measurements and the optical constants (refractive index n and extinction coefficient k) and film thickness have been obtained by fitting the transmittance using a semi-quantum model. The electrical properties were characterized by Hall effect measurements. It has been found that the ITO film with low electrical resistivity and high transmittance can be obtained with 40 sccm oxygen flow (the working pressure is about 2.3 × 10^− 2 Pa at this oxygen flow).     

Characterization of Hafnium-Zirconium-Oxide-Nitride films grown by ion beam assisted deposition

Hafnium-Zirconium-Oxide-Nitride (Hf_1−xZr_xO_1−yN_y) films are prepared by ion beam assisted deposition on p-Si and quartz substrates with a composite target of sintered high-purity HfO₂ and ZrO₂. The thermal stability and microstructure characteristics for Hf_1−xZr_xO_1−yN_y films have been investigated. EDS results confirmed that nitrogen was successfully incorporated into the Hf_1−xZr_xO₂ films. XRD and Raman analyses showed that the Hf_1−xZr_xO_1−yN_y films remain amorphous after 1100 °C under vacuum ambient, and monoclinic HfO₂ and ZrO₂ crystals separate from Hf_1−xZr_xO_1−yN_y films with a increase of the annealing temperature up to 1300 °C. Meanwhile, the Hf_1−xZr_xO_1−yN_y films can also effectively suppress oxygen diffusion during high temperature annealing. AFM measurements demonstrated that surface roughness of the Hf_1−xZr_xO_1−yN_y films increase slightly. Then the optical properties of the samples were observed in the ultraviolet-visible range at room temperature. The variation in E_g from 5.64 to 6.09 eV as a function of annealing temperature has also been discussed briefly.     

Silicon nitride and oxynitride films prepared by ion beam reactive sputtering

The composition of particles sputtered from a silicon target during bombardment by nitrogen and oxygen ions was measured. Elementary processes on both the substrate and the target were examined. A model of silicon nitride film formation was proposed, in which the main idea is the interaction of silicon on the substrate with the atomic nitrogen sputtered from the target. The dependence of the film properties on the oxygen concentration in N₂O₂ mixtures was investigated. The relationship between the nitrogen and silicon concentrations in silicon nitride films, the nitrogen ion beam incidence angle and the ejection angle of the sputtered particles was revealed experimentally. In the proposed model this relationship is interpreted as a result of the difference between the angular distribution of silicon and nitrogen atoms sputtered from the target.     

Biaxially textured Ag films by grazing ion beam assisted deposition

The effect of grazing incidence 4 keV Ar⁺ ion irradiation on the early stage of Ag thin film growth on amorphous Si was investigated. The double effect of axial and surface channeling resulted in grains oriented along the 〈110〉 axis in-plane, while the (111) out-of-plane texture was maintained. A slight average tilt of the (111) out-of-plane texture axis towards the ion beam direction is proposed to result from the difference between terrace and step edge sputtering yield. The observed tilt is consistent with a minimum erosion orientation of the surface profile.     

Bactericidal and biocompatible properties of TiN/Ag multilayered films by ion beam assisted deposition

Nanoscale TiN/Ag multilayered films of thickness 500 nm were synthesized on AISI317 stainless steel by ion beam assisted deposition (IBAD) with the modulation period of 4, 5, 6, 7.5, and 12 nm. The bactericidal and biocompatible properties of TiN/Ag multilayered films were investigated through Gram negative E. coli bacteria and L929 cells (mice fibroblast) as well as human umbilical vein endothelial cells (HUVEC). The results show that the TiN/Ag multilayered films with the modulation period of 7.5 nm possess the strongest bactericidal property. The cytotoxicity grade of TiN/Ag multilayered coating with the modulation periods of 7.5 nm, 12 nm is in 0–1 scope, which indicates this film has no cytotoxicity to L929. HUVEC on TiN/Ag multilayered film grows well and shows good cellularity. Auger electronic spectroscopy reveals the relationship between the structure of TiN/Ag multilayered film and the biomedical properties.     

Bactericidal and biocompatible properties of TiN/Ag multilayered films by ion beam assisted deposition

Nanoscale TiN/Ag multilayered films of thickness 500 nm were synthesized on AISI317 stainless steel by ion beam assisted deposition (IBAD) with the modulation period of 4, 5, 6, 7.5, and 12 nm. The bactericidal and biocompatible properties of TiN/Ag multilayered films were investigated through Gram negative E. coli bacteria and L929 cells (mice fibroblast) as well as human umbilical vein endothelial cells (HUVEC). The results show that the TiN/Ag multilayered films with the modulation period of 7.5 nm possess the strongest bactericidal property. The cytotoxicity grade of TiN/Ag multilayered coating with the modulation periods of 7.5 nm, 12 nm is in 0-1 scope, which indicates this film has no cytotoxicity to L929. HUVEC on TiN/Ag multilayered film grows well and shows good cellularity. Auger electronic spectroscopy reveals the relationship between the structure of TiN/Ag multilayered film and the biomedical properties.     

Stability of indium-oxide thin-film transistors by reactive ion beam assisted deposition

This work reports on the performance and stability of bottom-gate In₂O₃-TFTs with PECVD silicon dioxide gate dielectric. A highly-resistive amorphous In₂O₃ channel layer was deposited at room temperature by reactive ion beam assisted evaporation (IBAE). The field-effect mobility of the n-channel TFT is 33 cm²/V-s, along with an ON/OFF current ratio of 10⁹, and threshold voltage of 2 V. Device stability was demonstrated through measurement of the threshold voltage shift during long-term gate bias-stress and current stress experiments. Device performance, including stability, together with low-temperature processing, makes the indium-oxide TFT an attractive candidate for flexible transparent electronics, and display applications.     

低能Ar+离子束辅助沉积择优取向Pt(111)膜

采用低能Ar+离子束辅助沉积方法,在Mo/Si(100)基底上沉积Pt膜,离子/原子到达比分别为0.1、0.2、0.3.若Ar+离子的入射角为0°,XRD谱分析表明,沉积的Pt膜均呈(111)和(200)混合晶向;当Ar+离子的入射角为45°,沉积的Pt膜均呈很强的(111)择优取向.因此若合理控制Ar+离子束的入射角,可在Mo/Si(100)衬底上制备出具有显著择优取向的Pt(111)薄膜.本文采用Monte Carlo方法模拟低能Ar+离子注入 Pt单晶所引起的原子级联碰撞过程,得出Ar+离子入射单晶铂(200)晶面时,Ar+离子的溅射率与入射角的关系,对Pt膜择优取向的机理作了初步的探讨和分析.     

Effect of nitrogen flow ratio on structure and properties of zirconium nitride films on Si(100) prepared by ion beam sputtering

In this study, zirconium nitride thin films were deposited on Si substrates by ion beam sputtering (IBS). Influence of N₂/(N₂+Ar) on the structural and physical properties of the films has been investigated with respect to the atomic ratio between nitrogen and zirconium. It was found that the thickness of layers decreased by increasing the F(N₂). Moreover, crystalline plane peaks such as (111), (200) and (220) with (111) preferred orientation were observed due to strain energy which associate with (111) orientation in ZrN. Also, the fluctuation in nitrogen flow ratio results in colour and electrical resistivity of films.     

Oriented carbon nanostructures containing nitrogen obtained by ion beam assisted deposition

In this paper, we report the deposition of graphite multilayer containing nitrogen covering nanometric nickel particles. In-situ photoelectron emission spectroscopy (XPS) reveals the presence of nitrogen in the carbon layer covering the nickel particles. The field emission properties of the structures are reported. Atomic force microscopy displays regular domelike structures. Raman spectroscopy shows the characteristic frequencies associated with graphite and disordered structures. High-resolution transmission electron microscopy confirms the presence of multiwall well-organized graphite layers covering the nickel particles. Disorder increases on increasing nitrogen content. The samples were prepared in-situ by depositing first a few atomic layers of nickel and subsequent islands formation by thermal annealing. Then, an argon ion beam bombards an ultrapure carbon target and simultaneously the growing film is assisted with a second low-energy nitrogen ion beam (ion beam assisted deposition).