Room temperature preparation of c axis oriented ZnO films on Si(100), SiO2, and ZnO substrates by rf magnetron sputtering

Abstract

Growth of ZnO thin films with c axis (002) orientation has been demonstrated at room temperature on Si(100), SiO₂, and amorphous ZnO substrates by the rf magnetron sputtering method. The structural properties of the ZnO thin films were investigated with varying rf power. X-ray diffraction analysis revealed that increasing rf power helped to increase the c axis lattice constant and grain size, regardless of substrate material. Scanning electron microscopy indicated that the structural morphology of the ZnO films was not dependent on the substrate material.     

Transparent and conductive indium tin oxide/polyimide films prepared by high‐temperature radio‐frequency magnetron sputtering

A highly transparent and thermally stable polyimide (PI) substrate was prepared and used for the fabrication of indium tin oxide (ITO)/PI films via radio‐frequency magnetron sputtering at an elevated substrate temperature. The effect of the deposition conditions, that is, the oxygen flow rate, substrate temperature, sputtering power, and working pressure, on the optical and electrical properties of the ITO/PI films were investigated from the microstructural aspects. The results indicate that the optical and electrical properties of ITO were sensitive to the oxygen. Moreover, it was beneficial to the improvement of the ITO conductivity through the adoption of a high substrate temperature and sputtering power and a low working pressure in the deposition process. A two‐step deposition method was developed in which a thick bulk ITO layer was overlapped by deposition on a thin seed ITO layer with a dense surface to prepare the highly transparent and conductive ITO/PI films. The ITO/PI film after annealing at 240°C gave a transmittance of 83% and a sheet resistance of 19.7 Ω/square. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42753.     

The optical properties of Ti-doped TiO2 nanoceramic films deposited by simultaneous rf and dc magnetron sputtering

The Ti-doped TiO₂ (TiO₂:Ti) nanoceramic films were deposited by simultaneous rf magnetron sputtering of TiO₂ and dc magnetron sputtering of Ti. When dc power increased, TiO preferentially formed and the deposited films had lower O/Ti atomic ratio, especially at low substrate temperature. With the decrease of substrate temperature, the TiO₂:Ti film had relatively high optical energy gap, therefore the absorption edge showed the blue shift. The nonlinear refractive indices of TiO₂:Ti films prepared at different dc powers and substrate temperatures were measured by Moiré deflectometry, and were of the order of 10^?8 cm² W^?1. By decreasing dc power and increasing substrate temperature, TiO₂:Ti film exhibited lower surface roughness, higher linear refractive index and lower stress-optical coefficient.     

Influence of deposition parameters on the dielectric properties of rf magnetron sputtered Ba(ZrxTi1−x)O3 thin films

Ba(Zr_xTi_1−x)O₃ (BZ_xT_1−x in short) thin films have been deposited on Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering and their dielectric properties have been characterized as a function of sputtering parameters. The BZ_xT_1−x thin films are amorphous when sputtered at rf power (R_p)=100 W and substrate temperature (S_T)=300 °C. The crystalline phase of the BZ_xT_1−x thin films appears when the substrate temperature increases from 300 to 400 and 500 °C, respectively, and the films have a high degree of (100) preferred orientation. The dielectric constant decreases with increasing measurement temperature, irrespective of the rf power and Zr content of the BZ_xT_1−x thin films. The BZ_0.3T_0.7 thin films have a low dielectric loss tangent irrespective of the sputtering parameters. The dielectric constant of the BZ_0.3T_0.7 thin film increases with increasing Zr·(Zr+Ti)⁻¹ ratio and deposition temperature but decreases with increasing working pressure. Besides, the dielectric constant suddenly increases from 244.0 to 284.1 when the rf power increases from 100 to 130 W, then it decreases from 284.1 to 270.0 when the rf power increases from 130 to 160 W. The dielectric constant also suddenly increases from 164.1 to 281.5 when the sputtering gas contains O₂ from 0 to 10%, but its variation is insignificant when the sputtering gas contains O₂ from 10 to 20%.     

Effect of substrate temperature on the properties of TiO2 nanoceramic films

TiO₂ nanoceramic films were deposited on glasses by rf magnetron sputtering. This method provides more advantages in controlling the microstructure and composition of the films. TiO preferentially formed and the deposited films tended to become nonstoichiometric by increasing substrate temperature. The morphologies and hydrophilic properties of TiO₂ films were significantly affected by the substrate temperature. The nonlinear refractive index of the TiO₂ film on the glass substrate measured by Moiré deflectometry was of the order of 10^?8 cm² W^?1. Smaller grain size, higher optical energy gap, visible transmission and linear refractive index, and lower stress-optical coefficient were obtained at lower substrate temperature.     

ITO薄膜射频磁控溅射法制备及性能研究

以10%SnO2和90%In2O3(以质量计)烧结成的ITO氧化物陶瓷为靶材,采用射频磁控溅射法在玻璃基片成功地制备出光电性能优异的ITO透明导电薄膜。研究了基片温度和氧分压溅射工艺参数对ITO薄膜的结构和光电性能的影响。实验结果表明,采用氧化铟锡陶瓷靶射频磁控溅射制备的ITO薄膜沿(222)晶面生长,薄膜紫外透射光谱的吸收截止边带随着衬底温度和氧分压的升高向短波长方向漂移。     

Structural and optical properties of ITO/TiO2 anti-reflective films for solar cell applications

Indium tin oxide (ITO) and titanium dioxide (TiO₂) anti-reflective coatings (ARCs) were deposited on a (100) P-type monocrystalline Si substrate by a radio-frequency (RF) magnetron sputtering. Polycrystalline ITO and anatase TiO₂ films were obtained at room temperature (RT). The thickness of ITO (60 to 64 nm) and TiO₂ (55 to 60 nm) films was optimized, considering the optical response in the 400- to 1,000-nm wavelength range. The deposited films were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM). The XRD analysis showed preferential orientation along (211) and (222) for ITO and (200) and (211) for TiO₂ films. The XRD analysis showed that crystalline ITO/TiO₂ films could be formed at RT. The crystallite strain measurements showed compressive strain for ITO and TiO₂ films. The measured average optical reflectance was about 12% and 10% for the ITO and TiO₂ ARCs, respectively.     

Room temperature preparation of high performance AZO films by MF sputtering

Aluminum-doped zinc oxide (AZO) thin films have been deposited by MF magnetron sputtering from a ceramic oxide target without heating the substrates. This study has investigated effects of sputtering power on the structural, electrical and optical properties of the AZO films. The films delivered a hexagonal wurtzite structure with (002) preferential orientation and uniform surface morphology with 27–33 nm grain size. The results indicate that residual stress and grain size of the AZO films are dependent on sputtering power. The minimum resistivity of 7.56×10^?4 Ω cm combined with high transmittance of 83% were obtained at deposited power of 1600 W. The films delivered the advantages of a high deposition rate at low substrate temperature and should be suitable for the fabrication of low-cost transparent conductive oxide layer.     

Preparation of Fluorine-Containing Indium Tin Oxide Sputtering Targets using Spark Plasma Sintering Process

Fluorine-containing indium tin oxide (F-ITO) sputtering targets were prepared using spark-plasma-sintering (SPS) process. The initial powder, which was prepared by reacting ITO with HF, was sintered to the 10 cm-disks with nearly 90% of the theoretical density by the SPS process. The resulting disks were consisted of ITO and InOF, and the fluorine content was about 4 at.%. Using the F-ITO disks as sputtering target, thin films were deposited on the glass substrates. The electrical conductivity and optical transmission of the deposited films were comparable to those of the conventional ITO films, while the surface roughness of the films was much improved.     

Effects of element chemical states and grain orientation growth of ITO targets on photoelectric properties of the film

A study was carried out to compare element chemical states and grain orientation growth between two ITO targets, which were respectively sintered at 1560 °C (target A#) and 1600 °C (target B#). The lower sintering temperature can be beneficial to increase mass content ratio of In₂O₃ to SnO₂, reduce the production of Sn²⁺ ions and the component of O-In as well as increase oxygen holes, and can also promote grain orientation growth of In₂O₃ and In₄Sn₃O₁₂ phase. Three groups of ITO films were deposited at 230 °C using these targets to investigate the effects of sputtering parameters on the photoelectric properties of ITO films. Under different sputtering pressures, the sheet resistance for target A# has higher sensitivity to low O₂ flow, while target B# displays higher sensitivity to high O₂ flow. In the case of sputtering pressure of 0.5 Pa, ITO films for target A# displays the highest visible transmittance. In addition, annealing process could decrease the sheet resistance and improve the transmittance of ITO films because of its effect on the crystallinity and surface morphology of ITO films.     

Comparative studies of polypropylene nonwoven sputtered with ITO and AZO

In this study, the polypropylene (PP) spunbonded nonwoven materials were used as substrates for depositing transparent nanostructures on the fiber surfaces. Magnetron sputter coating technique was used to deposit tin‐doped indium oxide (ITO) and aluminum‐doped zinc oxide (AZO) films onto the nonwoven substrates. The structures and properties of the deposited ITO and AZO films were investigated and compared using atomic force microscopy, energy‐dispersive X‐ray (EDX), and electrical and optical tests. The observations by atomic force microscopy revealed the formation of functional nanostructures on the fiber surfaces. EDX analyses confirmed the deposition of ITO and AZO functional films on the PP fibers. It was found that ITO had more compact structures on the fiber surface than AZO under the same sputtering conditions. The transmittance analysis revealed that the nonwoven substrates deposited with nanostructural AZO showed better ultraviolet shielding effect than those coated with ITO in the same thickness. The nonwoven materials coated with ITO had lower electrical resistance than those coated with AZO in the same thickness. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Influence of deposition parameters and annealing treatment on the properties of GZO films grown using rf magnetron sputtering

In this study, transparent conductive films of gallium-doped zinc oxide (GZO) are deposited on soda-lime glass substrates, under varied coating conditions (rf power, sputtering pressure, substrate-to-target distance and deposition time), using radio frequency (rf) magnetron sputtering, at room temperature. The effect of the coating parameters on the structural, morphological, electrical and optical properties of GZO films was studied. This study uses a grey-based Taguchi method, to determine the parameters of the coating process for GZO films, by considering multiple performance characteristics. In the confirmation runs, with grey relational analysis, improvements of 14.1% in the deposition rate, 39.81% in electrical resistivity and 1.38% in visible range transmittance were noted. The influence of annealing treatment, in a vacuum, oxygen, and nitrogen gas atmospheres, at temperatures ranging from 130 to 190 °C, for a period of 1 h, was also investigated. GZO films annealed at 190 °C, in a vacuum, showed the lowest electrical resistivity, at 1.07 × 10⁻³ Ω-cm, with about 85% optical transmittance, in the visible region. It is likely that films grown at lower temperatures (190 °C) could be coated onto polymeric substrates, to produce flexible optoelectronic devices.     

Microstructure of Molybdenum Disilicide-Silicon Carbide Nanocomposite Thin Films

Composite thin films of molybdenum disilicide-silicon carbide (MoSi₂-SiC) have been deposited via rf magnetron sputtering onto molybdenum substrates. An intermediate layer was deposited in the presence of nitrogen gas and evaluated as a potential diffusion barrier layer. The composite films have been characterized using X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and Auger electron spectroscopy. The as-deposited films were amorphous but crystallized into nanometer-sized grains after annealing under vacuum at 1000°C for 30 min. There was a significant amount of interdiffusion between the film and substrate, which resulted in the formation of subsilicides such as Mo₅Si₃ and MoSi₃, as well as Mo₂C. The films that were deposited via reactive sputtering in a nitrogen ambient were amorphous in both the as-deposited and annealed conditions. Significantly fewer second phases were detected with the presence of the intermediate layer, which suggests the potential use of the nitrided (MoSi _x N _y C _z ) layer as a high-temperature diffusion barrier layer for the silicon and carbon.     

As-deposited LiCoO2 thin film cathodes prepared by rf magnetron sputtering

LiCoO₂ thin films were deposited using radio frequency (rf) magnetron sputtering system on stainless steel substrates. Different rf powers, up to 150 W, were applied during deposition. The as-deposited films exhibited (1 0 1) and (1 0 4) preferred orientation and the nanocrystalline film structure was enhanced with increasing rf power. The film crystallinity was examined using X-ray diffraction, Raman scattering spectroscopy and transmission electron microscopy. The compositions of the films were determined by inductively coupled plasma-mass spectroscopy. The average discharge capacity of as-deposited films is about 59 μAh/(cm² μm) for cut-off voltage range of 4.2 and 3.0 V. From the electrochemical cycling data, it is suggested that as-deposited LiCoO₂ films with a nanocrystalline structure and a favorable preferred orientation, e.g. (1 0 1) or (1 0 4) texture, can be used without post-annealing at high temperatures for solid-state thin film batteries.     

Structural Modification of TiO2 Nanorod Films with an Influence on the Photovoltaic Efficiency of a Dye-Sensitized Solar Cell (DSSC)

TiO₂ nanorod films have been deposited on ITO substrates by dc reactive magnetron sputtering technique. The structures of these nanorod films were modified by the variation of the oxygen pressure during the sputtering process. Although all these TiO₂ nanorod films deposited at different oxygen pressures show an anatase structure, the orientation of the nanorod films varies with the oxygen pressure. Only a very weak (101) diffraction peak can be observed for the TiO₂ nanorod film prepared at low oxygen pressure. However, as the oxygen pressure is increased, the (220) diffraction peak appears and the intensity of this diffraction peak is increased with the oxygen pressure. The results of the SEM show that these TiO₂ nanorods are perpendicular to the ITO substrate. At low oxygen pressure, these sputtered TiO₂ nanorods stick together and have a dense structure. As the oxygen pressure is increased, these sputtered TiO₂ nanorods get separated gradually and have a porous structure. The optical transmittance of these TiO₂ nanorod films has been measured and then fitted by OJL model. The porosities of the TiO₂ nanorod films have been calculated. The TiO₂ nanorod film prepared at high oxygen pressure shows a high porosity. The dye-sensitized solar cells (DSSCs) have been assembled using these TiO₂ nanorod films prepared at different oxygen pressures as photoelectrode. The optimum performance was achieved for the DSSC using the TiO₂ nanorod film with the highest (220) diffraction peak and the highest porosity.     

Preparation of diamond like carbon thin films above room temperature and their properties

Diamond like carbon (DLC) thin films were deposited on p-type silicon (p-Si), quartz and ITO substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) at different substrate temperatures (RT ∼ 300 °C). Argon (Ar: 200 sccm) was used as carrier gas while acetylene (C₂H₂: 20 sccm) and nitrogen (N: 5 sccm) were used as plasma source. Analytical methods such as X-ray photoelectron spectroscopy (XPS), FT-IR and UV–visible spectroscopy were employed to investigate the structural and optical properties of the DLC thin films respectively. FT-IR spectra show the structural modification of the DLC thin films with substrate temperatures showing the distinct peak around 3350 cm^− 1 wave number; which may corresponds to the sp² C–H bond. Tauc optical gap and film thickness both decreased with increasing substrate temperature. The peaks of XPS core level C 1 s spectra of the DLC thin films shifted towards lower binding energy with substrate temperature. We also got the small photoconductivity action of the film deposited at 300 °C on ITO substrate.     

Deposition and characterization of AZO thin films on flexible glass substrates using DC magnetron sputtering technique

Al-doped zinc oxide (AZO) thin films were deposited onto flexible ultra-thin glass substrates by using a direct current (DC) magnetron sputtering process. The effects of sputtering power, working pressure and substrate temperature on the morphology and optoelectronic performances of AZO films were investigated. The optimal sputtering power, working pressure and substrate temperature for AZO film were determined to be 100 W, 0.9 Pa and 150 ℃, respectively. Further increasing or decreasing the sputtering power, working pressure and substrate temperature degrades the quality of AZO films. XRD patterns show all as-sputtered AZO thin films are preferred to grow along <0002> direction. Moreover, the largest grain size, which depicts the best microstructure of AZO films, matches with the smallest stress value. It can be seen from SEM images that the surface is smooth and dense. The smallest value of the resistivity is 1.784×10⁻³ Ω cm and the average transmittance of all AZO films in the visible range is about 80%. The X-ray photoelectron spectroscopy spectra show that the amount of Al element in the AZO film is very small.     

磁控溅射法制备纳米Cu薄膜及其微结构的研究

采用磁控溅射法制备出以ITO为基底的纯Cu薄膜,考察溅射时间和基底温度等工艺条件对生长Cu薄膜的影响.用电子扫描显微镜(SEM)、X射线衍射仪(XRD)对薄膜的形貌、厚度和结构进行表征.实验结果表明:在一定范围内调控衬底温度和溅射时间,可获得不同形貌、尺寸和厚度的Cu薄膜,所得薄膜的晶体结构为面心立方结构,均沿(111...     

Heteroepitaxial growth of TiN film on MgO (100) by reactive magnetron sputtering

TiN thin films were deposited on MgO (100) substrates at different substrate temperatures using rf sputtering with Ar/N₂ ratio of about 10. At 700°C, the growth rate of TiN was approximately 0.05 μm/h. The structural and electrical properties of TiN thin films were characterized with x-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Hall measurements. For all deposition conditions, XRD results show that the TiN films can be in an epitaxy with MgO with cube-on-cube orientation relationship of (001)_TiN // (001)_MgO and [100]_TiN // [100]_MgO. TEM with selected-area electron diffraction pattern verifies the epitaxial growth of the TiN films on MgO. SEM and AFM show that the surface of the TiN film is very smooth with roughness approximately 0.26 nm. The minimum resistivity of the films can be as low as 45 μΩ cm.     

The properties of Al-doped TiO2 nanoceramic films deposited by simultaneous rf and dc magnetron sputtering

The Al-doped TiO₂ (TiO₂:Al) nanoceramic films were deposited by simultaneous rf magnetron sputtering of TiO₂ and dc magnetron sputtering of Al. The advantage of this method is that the Al content could be independently controlled. Al₂O₃ was favorable to form with decreasing Al content. The nanocrystallinity was enhanced by increasing the Al contents, because the increase of Al contents resulted in that the deposited films to be nearly stoichiometric. The morphologies of TiO₂:Al films were significantly affected by Al contents. The nonlinear refractive index of TiO₂:Al film on the glass substrate was measured by Moiré deflectometry, and was of the order of 10^?8 cm² W^?1. As Al content increased, the TiO₂:Al film had high VIS-IR transmission, high optical energy gap, high linear refractive index and low porosity.