Photoluminescence characterization of β-FeSi2 prepared by ion beam sputter deposition (IBSD) method

Photoluminescence (PL) measurement technique was found to be effective in revealing the unique characteristics of β-FeSi₂ film formation on Si substrates by means of ion beam sputter deposition (IBSD) method. A strong photoluminescence peak at around 0.8 eV was observed for β-FeSi₂ samples and also for Si substrates that were sputter etched by Ne⁺, and then thermally annealed in air at elevated temperature. Comparison with literature data indicated that the PL peak at 0.8 eV observed in this study was mainly from D1 emission bands in Si substrate, whose intensity was enhanced by the sputter etching and the subsequent annealing of the substrate. Furthermore, comparison between CZ-Si and FZ-Si results indicated that the energy of 0.8 eV peak observed in this study was affected by the presence of oxygen in the Si bulk as well.     

Effect of substrate temperature and deposited thickness on the formation of iron silicide prepared by ion beam sputter deposition

Ion beam sputter deposition (IBSD) method was employed to find optimum conditions for the formation of epitaxial β-FeSi₂ films on Si(100) substrate. It was found that crystal structure of the films as determined by X-ray diffraction (XRD) analysis is dependent on the substrate temperature as well as on the deposited thickness of sputtered Fe. The film with best crystal properties was obtained either at 873 K with the deposited Fe thickness of 15 nm, or at 973 K with the deposited Fe thickness of 30 nm. The obtained results indicate the importance of Fe and/or Si diffusion in determining the crystal properties of β-FeSi₂ film.     

Effect of target compositions on the crystallinity of β-FeSi2 prepared by ion beam sputter deposition method

Targets with the elemental composition of Fe, Fe₂Si and FeSi₂ were employed in the present study to grow β-FeSi₂ film on Si (100) substrate by means of ion beam sputter deposition (IBSD) method. The results revealed that when FeSi₂ target was employed, a Si-rich phase, α-FeSi₂ (Fe₂Si₅), was predominant at temperatures above 973 K, while β-FeSi₂ phase was observed only in the limited temperature range at around 873 K. In this case, Si was originated both from the sputtered target and the substrate, thus, the supply of Si was considered to be excessive to sustain β structure. On the other hand, the films prepared with Fe target became polycrystalline as they grow thicker than 100 nm. In order to optimize the supply of Fe and Si for epitaxial growth, Fe₂Si target was employed, where highly (100)-oriented β-FeSi₂ layer of 120 nm in thickness was obtained at 973 K.     

束流密度对Ge/Si量子点溅射生长的影响

采用离子束溅射技术在Si基底上自组织生长了一系列Ge量子点样品,研究了束流密度对Ge/Si量子点的尺寸分布和形貌演变的影响。原子力显微镜测试结果表明,随着束流密度的增加,量子点的面密度持续增大,其尺寸不断减小,量子点的形貌由圆顶形转变为过渡圆顶形。计算直径标准偏差的结果表明,当束流密度为0.86mA/cm2时,量子点的尺寸均匀性最佳。束流密度与沉积速率成正比,影响着表面吸附原子与其它原子相遇而形成晶核的能力。     

Surface characterization of titanium oxide films synthesized by ion beam enhanced deposition

In this article, titanium oxide films were prepared by ion beam enhanced deposition where titanium was evaporated by electron beam and simultaneously bombarded with xenon ion beams at an energy of 40 keV in an O₂ environment. X-ray photoelectron spectroscopy and Auger electron spectroscopy were used to research the chemical state and composition of the titanium oxide films. The results show that surface of the film was fully oxidized. After the surface was removed by argon ion sputtering, the results show that Ti²⁺, Ti³⁺ and Ti⁴⁺ states exist on the sputtered surface. The atomic concentration of all the three titanium states were calculated. The chemical shift of O 1s peak was also observed on the near surface.     

Characterization of nanocrystalline indium tin oxide thin films prepared by ion beam sputter deposition method

Indium tin oxide (ITO) thin films were deposited on glass substrates by ion beam sputter deposition method in three different deposition conditions [(i) oxygen (O₂) flow rate varied from 0.05 to 0.20 sccm at a fixed argon (1.65 sccm) flow rate, (ii) Ar flow rate changed from 1.00 to 1.65 sccm at a fixed O₂ (0.05 sccm) flow rate, and (iii) the variable parameter was the deposition time at fixed Ar (1.65 sccm) and O₂ (0.05 sccm) flow rates]. (i) The X-ray diffraction (XRD) patterns show that the ITO films have a preferred orientation along (400) plane; the orientation of ITO film changes from (400) to (222) direction as the O₂ flow rate is increased from 0.05 to 0.20 sccm. The optical transmittance in the visible region increases with increasing O₂ flow rate. The sheet resistance (R_s) of ITO films also increases with increasing O₂ flow rate; it is attributed to the decrease of oxygen vacancies in the ITO film. (ii) The XRD patterns show that the ITO film has a strong preferred orientation along (222) direction. The optical transmittance in the visible spectral region increases with an increase in Ar flow rate. The R_s of ITO films increases with increasing Ar flow rate; it is attributed to the decrease of grain size in the films. (iii) A change in the preferred orientations of ITO films from (400) to (222) was observed with increasing film thickness from 314 to 661 nm. The optical transmittance in the visible spectral region increases after annealing at 200 °C. The R_s of ITO film decreases with the increase of film thickness.     

Effects of deposition and post-annealing conditions on electrical properties and thermal stability of TiAlN films by ion beam sputter deposition

TiAlN films were deposited by ion beam sputter deposition (IBSD) using a Ti-Al (90/10) alloy target in a nitrogen atmosphere on thermal oxidized Si wafers. Effects of ion beam voltage, substrate temperature (T_s) and post-annealing conditions on electrical properties and oxidation resistance of TiAlN films were studied. According to the experimental results, the proper kinetic energy provided good crystallinity and a dense structure of the films. Because of their better crystallinity and predomination of (200) planes, TiAlN films deposited with 900 V at low T_s (50 °C) have shown lower resistivity than those at high T_s (250 °C). They also showed better oxidation resistance. If the beam voltage was too high, it caused some damage to the film surfaces, which caused poor oxidation resistance of films. When sufficient kinetic energy was provided by the beam voltage, the mobility of adatoms was too high due to their extra thermal energy, thus reducing the crystallinity and structure density of the films. A beam voltage of 900 V and a substrate temperature of 50 °C were the optimum deposition conditions used in this research. They provided good oxidation resistance and low electrical resistivity for IBSD TiAlN films.     

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.     

离子束溅射沉积Ta2O5光学薄膜的实验研究

根据择优溅射的理论,在不同的通氧方式下,详细分析了离子辅助对离子束溅射沉积Ta2O5薄膜光学特性的影响。结果表明,在薄膜生长的过程中,由于氩离子的轰击作用,薄膜中的氧原子被优先溅射出来,造成了薄膜化学剂量比失调、吸收增加。但是,通过优化辅助离子源中氧气的比例,可获得合理化学剂量比、低损耗的Ta2O5薄膜。     

Characterization of Mo/Si soft X-ray multilayer mirrors by grazing-incidence small-angle X-ray scattering

The morphology of buried interfaces plays a key role in high performing Mo/Si soft X-ray mirrors. We show that grazing-incidence small-angle X-ray scattering is a highly effective and non-destructive diagnostic technique for analysis of buried interfaces. The parameters of average interface autocorrelation function can be determined unambiguously. Additionally period thickness, roughness of interfaces and an effective number of vertically correlated periods can be extracted. The multilayer mirrors were prepared by e-beam evaporation on heated and unheated substrates, ion beam assisted e-beam evaporation, ion beam sputtering and RF magnetron sputtering. The latter three techniques produce multilayer mirrors with comparable interface roughness. The differences in lateral correlation length and Hurst parameter are found.     

氧分压对动态离子束辅助沉积合成的氧化钛膜的影响

采用离子束增强沉积的方法,改变氧分压,在硅基体表面制备出了不同组分及不同取向的 氧化钛薄膜。采用 XRD,掠角衍射以及 XPS分析方法对薄膜的成分、结构和取向进行了分析,并 通过 RBS分析计算出了薄膜的 O/Ti比。实验结果发现,所制备的氧化钛薄膜为具有一定择优取 向的多晶膜,薄膜内 TiO、 Ti2O3和 TiO2共同存在。当氧分压低于 8.4× 10-4 Pa时,氧化钛薄膜的 成分以 TiO为主,且 TiO的取向随氧分压的增加从（ 220）向（ 031）转变,氧分压对薄膜取向的影响 较大。当氧分压高于 8.6× 10-4 Pa时,氧化钛薄膜的成分以具有（ 100）择优取向的金红石型 TiO2 为主,含有少量其他结构的 TiO2和低价 Ti,其成分及取向相对较为稳定,对氧分压的变化不敏感。     

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.     

Influence of substrate bias voltage on properties of Pt thin films deposited by non-mass separated ion beam deposition method

Pt thin films were deposited on Si substrates by applying a negative substrate bias voltage using a non-mass separated ion beam deposition method. The effect of the substrate bias voltage on the properties of the deposited films was investigated. In the case of Pt thin films deposited without the substrate bias voltage, a columnar structure and small grains were observed. The electrical resistivity of the deposited Pt films was very high (49.3 ± 0.65 µΩ cm). By increasing the substrate bias voltage, no clear columnar structure was observed. At the substrate bias voltage of − 75 V, the resistivity of the Pt film showed a minimum value of 16.9 ± 0.2 µΩ cm closed to the value of bulk (10.6 µΩ cm).     

Effects of ion energy on ion beam assisted deposition textured yttria stabilized zirconia buffer layer of coated conductor

High quality biaxially textured yttria stabilized zirconia (YSZ) thin films, as buffer layers of coated conductors, were deposited on hastelloy substrates by ion beam assisted deposition (IBAD) method with different assisting ion energy E_i. The roles of assisting ion beam and the influences of ion energy E_i on the structure of the films were studied. It was found that both the out-of-plane alignment and in-plane texture of the IBAD-YSZ films are sensitive to the variation of E_i. The results are explained in the paper by different damage tolerance of the differently oriented grains to ion bombardment.     

SiO2/TiO2 thin films with variable refractive index prepared by ion beam induced and plasma enhanced chemical vapor deposition

SiO₂/TiO₂ optical thin films with variable compositions have been prepared by ion beam induced and plasma enhanced chemical vapour deposition (IBICVD and PECVD). While the films obtained by IBICVD were very compact, the PECVD ones with a high content of Ti presented a columnar microstructure. The formation of Si–O–Ti bonds and a change in the environment around titanium from four- to six-coordinated has been proved by vibrational and X-ray absorption spectroscopies. The refractive index increased with the titanium content from 1.45 to 2.46 or 2.09 for, respectively, the IBICVD and PECVD films. Meanwhile, the band gap decreased, first sharply and then more smoothly up to the value of pure TiO₂. It is concluded that the optical properties of SiO₂/TiO₂ thin films can be properly tailored by using these two procedures.     

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).     

Enhanced exchange field of NiO/NiFe biyer by dual ion beam sputtering process control

Dual IBS (Ion Beam Sputtering) technique was used to fabricate NiO/NiFe bilayers. Various process conditions were examined to enhance the exchange field of the bilayer. Ion beam sputtering with an ion beam voltage above the threshold voltage and with the optimum ion beam current produced a fine-grained and smooth NiO film. This fine-grained surface followed by optimum etching exhibited an enhanced exchange field of 100 Oe. Growing NiO films were ion bombarded with a secondary ion-beam source having various beam voltages. The texture, surface roughness and grain size of the NiO films changed due to the ion bombardment; however, the grain size and/or surface roughness rather than texture was found to be responsible for controlling the exchange coupling. Furthermore, it was demonstrated that an optimum etching time of the NiO film prior to the depositing of NiFe for a large exchange field exists. With this optimum etching of the NiO film, surface segregated impurities could be eliminated without deteriorating the surface unnecessarily. Exchange fields and coercivities of the NiO/NiFe bilayers were measured with a MOKE (Magneto–Optic Kerr Effect) hysteresis looper and the surface properties of NiO films were examined with an AFM (Atomic Force Microscope) and an AES (Auger Electron Spectroscope).     

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.     

Electron beam evaporation deposition and properties of Abrupt GST/Si heterojunction structure

The ternary alloy, Ge₂Te₂Sb₅ is one of the most important compounds of the GeTe-Sb₂Te₃ pseudobinary systems. Ge₂Te₂Sb₅ thin films of thickness of 100 nm-300 nm were deposited by electron beam evaporation. After annealing at different temperatures, we did X-ray diffraction measurement to characterize the structure transformation of the material. In-situ resistance measurement depending on the temperature shows that there is about three orders of magnitude change between the high resistance state (amorphous state) and the low resistance state (face-centered cubic state). To construct a heterojunction diode, we deposited Ge₂Te₂Sb₅ thin films on n-type silicon wafers. Rectification effects were observed in voltage-current measurements of the abrupt heterojunctions. Traditional voltage-current relationship of p-n junctions and metal-semiconductor junctions are used to explain the characteristics of Ge₂Te₂Sb₅/n-Si heterojunctions.     

Electrical characteristics of mixed Zr-Si oxide thin films prepared by ion beam induced chemical vapor deposition at room temperature

Mixed Zr-Si oxide thin films have been prepared at room temperature by ion beam decomposition of organometallic volatile precursors. The films were flat and amorphous. They did not present phase segregation of the pure single oxides. A significant amount of impurities (-C-, -CH_x, -OH, and other radicals coming from partially decomposed precursors) remained incorporated in the films after the deposition process. This effect is minimized if the Ar content in the O₂/Ar bombarding gas is maximized. Static permittivity and breakdown electrical field of the films were determined by capacitance-voltage and current-voltage electrical measurements. It is found that the static permittivity increases non-linearly from ~ 4 for pure SiO₂ to ~ 15 for pure ZrO₂. Most of the dielectric failures in the films were due to extrinsic breakdown failures. The maximum breakdown electrical field decreases from ~ 10.5 MV/cm for pure SiO₂ to ~ 45 MV/cm for pure ZrO₂. These characteristics are justified by high impurity content of the thin films. In addition, the analysis of the conduction mechanisms in the formed dielectrics is consistent to Schottky and Poole-Frenkel emission for low and high electric fields applied, respectively.