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.     

Electrical insulation and bending properties of SiOx barrier layers prepared on flexible stainless steel foils by different preparing methods

Stainless steel foils on which flexible display devices and integrated solar modules are prepared need to be coated by barrier layers for electrical insulation. In this study, SiO_x barrier layer was prepared on steel foils (SUS 304) by ion beam assisted deposition, Sol-gel deposition and plasma enhanced chemical vapor deposition, respectively. The electrical properties of the SiO_x films, such as resistance, reactance, leakage current density, breakdown field strength and performance index were investigated, and the bending properties were evaluated by bending tests. The best electrical insulation and bending properties of barrier could be achieved with 4 μm thick SiO_x layer prepared by plasma enhanced chemical vapor deposition.     

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).     

Properties of indium tin oxide films deposited on unheated polymer substrates by ion beam assisted deposition

The optical, electrical and mechanical properties of indium tin oxide (ITO) films prepared on polyethylene terephthalate (PET) substrates by ion beam assisted deposition at room temperature were investigated. The properties of ITO films can be improved by introducing a buffer layer of silicon dioxide (SiO₂) between the ITO film and the PET substrate. ITO films deposited on SiO₂-coated PET have better crystallinity, lower electrical resistivity, and improved resistance stability under bending than those deposited on bare PET. The average transmittance and the resistivity of ITO films deposited on SiO₂-coated PET are 85% and 0.90 × 10^− 3 Ω cm, respectively, and when the films are bent, the resistance remains almost constant until a bending radius of 1 cm and it increases slowly under a given bending radius with an increase of the bending cycles. The improved resistance stability of ITO films deposited on SiO₂-coated PET is mainly attributed to the perfect adhesion of ITO films induced by the SiO₂ buffer layer.     

Deposition of diamond like carbon (DLC) and C-N films using ion beam assisted deposition (IBAD) technique and evaluation of their properties

Diamond like carbon films and C-N films were prepared using ion beam assisted deposition technique (IBAD). Tribological properties were studied by subjecting DLC coated films to the accelerated wear tests. These tests indicated a significant improvement in the mechanical surface properties of glass by DLC coating. Better wear features were obtained for thinner DLC coating as compared to the thicker ones. We also studied the optical properties and obtained a band gap of 1·4 eV for these films. An attempt was made to prepare C₃N₄ films by using IBAD. We observed variation in the nitrogen incorporation in the film with the substrate temperature.     

Structural, optical and electrical properties of high-k ZrO2 dielectrics on Si prepared by plasma assisted pulsed laser deposition

ZrO₂ films were grown on p-type Si(100) using plasma assisted pulsed laser deposition and the electrical characteristics of the ZrO₂ dielectrics incorporated in metal oxide silicon (MOS) capacitors were studied in combination with their structural and optical properties. The ZrO₂ dielectric layers are of polycrystalline structure with a monoclinic phase and show good interfacial properties without obvious SiO_x interface. The electrical performance of the capacitors exhibits typical MOS-type capacitance-voltage (C-V) and leakage current density-voltage (J-V) characteristics. Thermal annealing of the ZrO₂ dielectrics results in an improvement in C-V and J-V characteristics and a reduction in C-V hysteresis without obvious introduction of leakage paths for the fabricated MOS capacitors. The dielectric constant was calculated to be 15.4 and the leakage current density was measured to be 6.7 × 10^− 6 A/cm² at a gate voltage of + 1.0 V for 900 °C annealed ZrO₂ dielectric layers with an equivalent oxide thickness of 5.2 nm.     

Effects of post-deposition heat treatment on the microstructure and properties of Al-doped ZnO thin films prepared by aqueous phase deposition

In this study, transparent conducting aluminum-doped ZnO thin films (AZO) were deposited on glass substrates by a water-based liquid phase deposition method. The results show that by employing a two-step post-deposition heat treatment, the preferential orientation of ZnO (002) appeared as soon as the polycrystalline films were formed. Under a reducing atmosphere, the crystallinity of the films was effectively improved. Furthermore, the reducing atmosphere was also beneficial for the removal of the residual stress of the prepared films and the c-axis lattice constant was less stretched as compared to those under an inert atmosphere at identical T_p. Both the atomic force micrograph and scanning electron micrograph clearly exhibited that the heat treatment induced considerable grain growth. The X-ray photoelectron spectrum revealed that the heat treatment atmosphere had little impact on the bonding state of zinc and that the reducing atmosphere was favorable for the non-stoichiometric alumina, which in turn, resulted in more oxygen vacancies and led to improvement in electrical conductivity. The ratio of chemisorbed oxygen declined substantially when applying the reducing atmosphere. Accordingly, hydrogen was helpful for the reduction of chemisorbed oxygen onto AZO films. Generally, the electrical resistivity declined linearly with T_p. A minimum resistivity of 9.90 × 10^− 3 Ω·cm was obtained with a doping concentration of Al/Zn = 2.25 at.% at T_p = 700 °C. The largest mean free path of the carriers was 1.2 Å, which was much smaller than the observed grain sizes of the AZO films. Accordingly, the grain boundary scattering was not the detrimental scattering mechanism. In contrast, the scattering within the grains was responsible for the low mobility. An increase in optical transparency with the heat treatment temperature was observed due to the compact and smooth topography with larger grains, among which, less porous structures were formed at elevated temperature.     

Influence of modulation periods and modulation ratios on the structure and mechanical properties of nanoscale TiAlN/TiB2 multilayers prepared by IBAD

Alternate hard TiAlN/TiB₂ multilayers with different modulation periods (Λ) ranging from 0.6 to 27 nm and modulation ratios (t_TiAlN:t_TiB2) ranging from 8:1 to 25:1 were prepared using an ion beam assisted deposition (IBAD) system. The effect of Λ and t_TiAlN:t_TiB2 on the hardness, elastic modulus, residual stress, and fracture resistance were investigated using various characterization techniques. All multilayers with clear interfaces displayed higher hardness than individual TiAlN and TiB₂ layers. The maximum hardness of 35 GPa and critical load of 84 mN were obtained for the multilayer with a Λ of 2.2-8.8 nm and t_TiAlN:t_TiB2 of 8:1. Strong TiAlN (111) crystallographic texture as well as multilayer structure is thought to be be responsible for the increasing hardness of the TiAlN/TiB₂ multilayers.     

Ion beam energy effects on structure and properties of diamond like carbon films deposited by closed drift ion source

In the present study DLC films deposited from acetylene gas by a closed drift ion source were investigated. Ion beam energy effects on structure as well as optical and electrical properties of the synthesized films were studied. Non-monotonic dependence of structure of the DLC films on ion beam energy was observed. The highest sp³/sp² ratio as well as highest optical transparency was observed in the case of the films synthesized by 500 eV energy ion beam. However, the bandgap of the DLC films synthesized by 500 eV energy ion beam was the lowest between all investigated samples, while resistivity non-monotonically decreased with increase of the ion beam energy. These results were explained by changes of the sp³/sp² ratio, structure of sp² bonded clusters as well as hydrogen content in the film due to the competition between the increased (decreased) ion beam energy and decreased (increased) ion/neutral ratio.     

Effect of nickel incorporation on structural, nanomechanical and biocompatible properties of amorphous hydrogenated carbon thin films prepared by low energy biased target ion beam deposition

Nickel incorporated amorphous hydrogenated carbon (Ni/a:C-H) thin films were deposited onto the Si substrates via biased target ion beam sputtering of nickel combined with reactive ion beam deposition of a:C-H using CH₄/Ar gas mixture. The effects of Ni doping and target bias voltage on the microstructure and mechanical properties of the as-deposited films were investigated by means of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscopy and nanoindentation. It was found that the Ni content in the films gets increased with increasing target bias voltage, and most of the Ni atoms react with C atoms to form NiC_x phases in the Ni/a:C-H films. Moreover, the nickel carbide nanoparticles attain crystallinity even at low deposition temperature and get embedded in the cross-linked carbon matrix. It was found that the presence of Ni₃C nanoparticles tends to increase the content of sp² carbon, thus decreasing the hardness of Ni/a:C-H films as compared with that of a:C-H films. Additionally it was found that the nickel incorporated films do not show any adverse effect on the osteoblast cellular adhesion. Overall, these carbidic nanocrystals initiate direct graphitization and intend to change diamond-like to graphite-like carbon structure in Ni/a:C-H films with promising biocompatibility.     

二氧化钛过渡层对脉冲激光沉积钛酸锶钡薄膜微结构和介电性质的影响

选取极薄Ti02作为过渡层,采用脉冲激光沉积法分别在Si(100)和Pt(111)/Ti/SiO2/Si(100)基底上制备了Bao.6Sro.4TiO3(BST)薄膜,研究过渡层对BST薄膜微结构及电学性质的影响.发现厚度20纳米以内的锐钛矿相结晶TiO2过渡层可使BST薄膜由无规则取向转变为(111)择优取向,而非晶和较厚TiO2过渡层对BST薄膜的取向无影响.结晶的TiO2过渡层也使薄膜的表面颗粒变细.还研究了不同厚度TiO2对BST薄膜电学性质的影响,结果表明BST薄膜在Pt(111)底电极上加入极薄的结晶TiO2过渡层后电学性质有明显改善,薄膜的介电常数和可调谐度提高,而介电损耗降低.加入膜厚约5nm的TiO2过渡层后,测试频率为10 kHz时薄膜相应介电常数、介电损耗及可调谐度分别为513、0.053和36.7%.     

Influences of post-annealing on structural and electrical properties of Bi1.5Zn1.0Nb1.5O7 thin films prepared by pulsed laser deposition

Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) thin films were prepared on Pt/TiO₂/SiO₂/Si(100) substrates at 650 °C under an oxygen pressure of 10 Pa by using pulsed laser deposition process. The crystallinity, microstructure and electrical properties of BZN thin films were investigated to verify the influences of post-annealing thermal process on them. The X-ray diffractometer (XRD) results indicate that all Bi_1.5Zn_1.0Nb_1.5O₇ thin films without post-annealing process or with post-annealing in situ vacuum chamber and in oxygen ambient exhibit a cubic pyrochlore structure. The improved crystallinity of BZN thin films through post-annealing was confirmed by XRD and scanning electron microscope (SEM) analysis. Dielectric constant and loss tangent of the as-deposited BZN thin films are 160 and 0.002 at 10 kHz, respectively. After annealing, dielectric properties of thin films are significantly improved. Dielectric constant and loss tangent of the in situ annealed films are 181 and 0.0005 at 10 kHz, respectively. But the films post-annealed in O₂ oven show the largest dielectric constant of 202 and the lowest loss tangent of 0.0002, which may attribute to the increase in grain size and the elimination of oxygen vacancies. Compared with the as-deposited BZN thin films, the post-annealed films also show the larger dielectric tunability and the lower leakage current density.