In-situ investigations of magnetron sputtering processes with laboratory X-ray equipment

An Fe-Al duplex film was prepared on a Si(111)-wafer by sputter deposition in a vacuum chamber with two integrated small magnetron sources. The chamber allows the in-situ investigation of such sputtering processes using grazing incidence X-ray reflectivity, X-ray scattering measurements and X-ray diffraction. We will present details of the new cell and present the first results obtained using reflectivity measurements of the Fe-Al thin films. Here we will focus on the detailed evaluation of the specular reflectivity data of the iron films only, which clearly indicates the presence of an iron oxide, the density and roughness of which were determined and their changes with the film thickness were discussed in the framework of thin film growth models.     

同步辐射原位X射线散射技术在纳米与能源材料中的应用

同步辐射原位X射线散射技术可以实现对材料结构进行多尺度的、无损的、高时间空间分辨率的表征,动态地揭示材料微观结构在不同外界环境下的演变过程。X射线散射基础理论已经相对成熟。第三代同步辐射光源大幅提高了X射线散射技术的时空分辨率,进一步拓宽X射线散射技术的应用场景。当前同步辐射原位X射线散射技术的难点主要集中于实验装置设计和大数据处理。概述了X射线散射技术的主要分类和基本的实验方法,主要介绍了不同分类的同步辐射原位X射线散射技术在纳米材料(纳米颗粒生长和纳米颗粒自组装)与能源材料(以钙钛矿薄膜材料为代表)研究中的应用。最后结合当前国内外先进同步辐射光源的发展现状,展望了同步辐射原位X射线散射技术未来发展的方向和应用前景。     

同步辐射小角X射线散射及其在材料研究中的应用

小角X射线散射(small angle X-ray scattering,SAXS)是研究物质内部一纳米到数百纳米甚至到微米尺度级别微观结构的有力工具.近年来随着我国同步辐射技术的不断发展,同步辐射SAXS技术被越来越多地应用到各种材料的研究领域.然而,由于SAXS图谱是倒空间的信号,并不像显微镜那么直观,也不如X射线...     

On the dependence on bias voltage of the structural evolution of magnetron- sputtered nanocrystalline Cu films during thermal annealing

The nanostructural evolution during heat treatments of DC magnetron-sputtered Cu films deposited at different substrate bias voltages was experimentally studied. A growth chamber equipped with two magnetrons and Kapton windows for in-situ X-ray diffraction was mounted on a six-circle goniometer at a synchrotron beam line. Using Bragg-Brentano X-ray diffraction, the grain size, the texture, and the lattice constant were monitored during thermal annealing. Increasing the substrate bias voltage, the grain growth rate lowered, and the change in texture with time became smaller due to a decrease in the defect concentration. Furthermore, the grain size in the as-deposited films decreased with increasing bias voltage. The activation energy for grain growth was, within experimental errors, the same in all the films.     

同步辐射与分析测试

本文介绍一种大科学装置——同步辐射装置。这是一种数百人可同时在其上进行不同的科学技术实验的设备，其可达到的水平比实验室的极限水平高许多，从某些角度代表了国家的科学和技术水平。本文扼要介绍了同步辐射的特性，同步辐射装置的构造及一些主要的分析测试技术，如：X射线吸收精细结构光谱，X射线散射，高分辨X射线衍射，能量色散与时间分辨技术，聚集与微分析，成像与显微放大，综合测试原位测试及作铯对标定等。     

同步辐射技术在核材料研究中的应用

先进同步辐射光源具有高通量、高相干性、高脉冲重复率等优点,将基于其的X射线衍射、小角散射、成像、谱学等表征方法与原位环境(如温度场、应力场、气氛、溶液介质等)实验装置配合,可为系统表征与评价核能系统用材料与部件的服役行为和损伤机制提供重要技术手段.核材料在高温/应力/介质/中子辐照等复杂多场环境下的服役损伤行为长期以来...     

X-ray mirrors on flexible polymer substrates fabricated by atomic layer deposition

Atomic layer deposition (ALD) techniques were used to fabricate W/Al₂O₃ superlattices with high X-ray reflectivity on flexible Kapton® polyimide and polyethylene naphthalate (PEN) polymer substrates. Reflectivities of 78% and 74% at λ = 1.54 Å were measured for 6-bilayer W/Al₂O₃ superlattices on Kapton® polyimide and PEN, respectively. These excellent X-ray reflectivities are attributed to precise bilayer thicknesses and ultrasmooth interfaces obtained by ALD and smoothing of the initial polymer surface by an Al₂O₃ ALD layer. The conformal ALD film growth also produces correlated roughness that enhances the reflectivity. These W/Al₂O₃ superlattices on flexible polymers should be useful for ultralight and adjustable radius of curvature X-ray mirrors.     

In-situ synchrotron radiation photoemission spectroscopy study of the initial atomic layer deposition of Al2O3 film on Si(001) substrate

In-situ synchrotron radiation photoemission spectroscopy and X-ray photoemission spectroscopy have been used to investigate the initial stages of Al2O3 growth on a Si(001) substrate by atomic layer deposition (ALD). The core level spectra of Si 2p, O 1s, and Al 2p as well as the valence band spectra were measured at every half reaction in the trimethylaluminum (TMA)-H2O ALD process. The line shape changes and binding energy shifts of the core level spectra reveal that Al2O3 is predominantly formed with a small amount of Si oxide in the initial stages without the formation of Al silicate. All core level spectra were alternately shifted toward higher and lower binding energies sides at every half ALD reaction. This can be explained by the band bending effect induced by different chemical species on the surface during the TMA-H2O ALD reaction. The valence band spectra showed that four cycles of ALD reactions were necessary to complete the electronic structure of the Al2O3 film with a valence band offset of 3.73 eV.     

In-situ studies of the recrystallization process of CuInS2 thin films by energy dispersive X-ray diffraction

Recrystallization processes during the sulfurization of CuInS₂ (CIS) thin films have been studied in-situ using energy dispersive X-ray diffraction (EDXRD) with synchrotron radiation. In order to observe the recrystallization isolated from other reactions occurring during film growth, Cu-poor, small grained CIS layers covered with CuS on top were heated in a vacuum chamber equipped with windows for synchrotron radiation in order to analyze the grain growth mechanism within the CIS layer. In-situ monitoring of the grain size based on diffraction line profile analysis of the CIS-112 reflection was utilized to interrupt the recrystallization process at different points. Ex-situ studies by electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX) performed on samples of intermediate recrystallization states reveal that during the heat treatment Cu and In interdiffuse inside the layer indicating the importance of the mobility of these two elements during CuInS₂ grain growth.     

Anti-contamination device for cryogenic soft X-ray diffraction microscopy

Cryogenic microscopy allows one to view frozen hydrated biological and soft matter specimens with good structural preservation and a high degree of stability against radiation damage. We describe a liquid nitrogen-cooled anti-contamination device for cryogenic X-ray diffraction microscopy. The anti-contaminator greatly reduces the buildup of ice layers on the specimen due to condensation of residual water vapor in the experimental vacuum chamber. We show by coherent X-ray diffraction measurements that this leads to fivefold reduction of background scattering, which is important for far-field X-ray diffraction microscopy of biological specimens.     

Synchrotron X-ray reflectivity study of high dielectric constant alumina thin films prepared by atomic layer deposition

High dielectric constant (high-k) gate dielectric alumina films were prepared with nanoscale thicknesses on p-type silicon substrates by atomic layer deposition (ALD) with alternating pulses of trimethyl aluminum, nitrogen, ozone and nitrogen, and some of them were further thermally annealed. These high-k gate dielectric films were characterized by synchrotron X-ray reflectivity (XR), and the XR data were quantitatively analyzed, providing the following structural parameters of each gate dielectric film: the surface roughness and interfacial roughness, the electron density profile, the number of layers, and the thickness of individual layers. These structural characteristics were then analyzed in detail by considering the ALD processing conditions and post-thermal annealing history.     

Fabrication of epitaxial ZnO films by atomic-layer deposition with interrupted flow

We formed epitaxial ZnO thin films on a (0001) c-plane sapphire substrate through deposition of atomic layers (ALD) at 25-160 °C using diethylzinc (DEZn) and deionized water as precursors in combination with interrupted flow. High-resolution X-ray diffraction measurements were employed to characterize the microstructure of these films. With interrupted flow, we obtained ZnO thin films with an optimal growth window in a range of 40-160 °C, effectively decreasing the growth temperature by about 120 °C relative to a conventional method involving continuous flow. X-ray reflectivity measurements showed that the rate of growth increased also between 20 °C and 120 °C. The XRD results indicate that the stock time might extend the reaction of DEZn and water through an increased duration. All results show that a low temperature for growth improves the crystalline quality and is consistent with thermodynamically blocked self-compensation.     

Carbon contamination analysis and its effect on extreme ultra violet mask imaging performance using coherent scattering microscopy/in-situ accelerated contamination system

The coherent scattering microscopy/in-situ accelerated contamination system (CSM/ICS) is a developmental metrology tool designed to analyze the impact of carbon contamination on the imaging performance. It was installed at 11B EUVL beam-line of the Pohang Accelerator Laboratory (PAL). Monochromatized 13.5 nm wavelength beam with Mo/Si multilayer mirrors and zirconium filters was used. The CSM/ICS is composed of the CSM for measuring imaging properties and the ICS for implementing acceleration of carbon contamination. The CSM has been proposed as an actinic inspection technique that records the coherent diffraction pattern from the EUV mask and reconstructs its aerial image using a phase retrieval algorithm. To improve the CSM measurement accuracy, optical and electrical noises of main chamber were minimized. The background noise level measured by CCD camera was approximately 8.5 counts (3 sigma) when the EUV beam was off. Actinic CD measurement repeatability was <1 A (3 sigma) at 17.5 nm line and space pattern. The influence of carbon contamination on the imaging properties can be analyzed by transferring EUV mask to CSM imaging center position after executing carbon contamination without a fine alignment system. We also installed photodiode and ellipsometry for in-situ reflectivity and thickness measurement. This paper describes optical design and system performance observed during the first phase of integration, including CSM imaging performance and carbon contamination analysis results.     

In situ thermal residual stress evolution in ultrathin ZnO and Ag films studied by synchrotron x-ray diffraction

Residual-stress evolution in sputtered encapsulated ZnO/Ag/ZnO stack has been studied in-situ by synchrotron x-ray diffraction when heat treated. The ZnO/Ag/ZnO stack encapsulated into Si₃N₄ layers and deposited on (001) Si substrates was thermally heated from 25 °C to 600 °C and cooled down to 25 °C. X-ray diffraction 2D patterns captured continuously during the heat treatment allowed monitoring the diffraction peak shifts of both Ag (15 nm thick) and ZnO (10 nm and 50 nm thick) sublayers. Due to the mismatch between the coefficients of thermal expansion, the silicon substrate induced compressive thermal stresses in the films during heating. We first observed a linear increase of the compressive stress state in both Ag and ZnO films and then a more complex elastic-stress evolution starts to operate from about 100 °C for Ag and about 250 °C for ZnO. Thermal contraction upon cooling seems to dominate so that the initial compressive film stresses relax by about 300 and 700 MPa after thermal treatment for ZnO and Ag, respectively. The overall behavior is discussed in terms of structural changes induced by the heat treatment.     

三维X射线衍射技术与工程材料研究

第三代同步辐射光源可以产生高能X射线,实现对使役条件下工程材料内部晶体结构的原位无损表征.三维X射线衍射(3DXRD)是一种基于同步辐射技术的新兴表征技术,其采用单色高能硬X射线对多晶材料沿不同方向采集衍射信号,得到材料内部晶粒的晶体取向、空间位置、晶内局部应力张量等信息.当结合原位实验对材料进行3DXRD分析时,可以...     

Atomic layer deposition of MnO using Bis(ethylcyclopentadienyl)manganese and H2O

Manganese oxide (MnO) atomic layer deposition (ALD) was accomplished using sequential exposures of bis(ethylcyclopentadienyl)manganese (Mn(CpEt)₂) and H₂O. Rutherford backscattering analysis revealed a nearly 1:1 atomic ratio for Mn:O in the MnO ALD films. X-ray diffraction determined that the films were crystalline and consistent with the cubic phase of MnO. Quartz crystal microbalance (QCM) measurements monitored the mass deposition rate during MnO ALD and verified self-limiting reactions for each reactant. Extremely efficient reactions were observed that required reactant exposures of only 3 × 10⁴ L (1 L = 1.33 × 10^− 4 Pa s). X-ray reflectivity (XRR) studies were used to confirm the QCM measurements and determine the film density and film thicknesses. The MnO ALD film density was 5.23 g/cm³. The growth per cycle was investigated from 100-300 °C. The largest MnO ALD growth per cycle was 1.2 Å/cycle at 100 °C and the growth per cycle decreased at higher temperatures. Transmission electron microscopy images observed the conformality of MnO films on ZrO₂ nanoparticles and confirmed the growth per cycle observed by the XRR studies. Fourier transform infrared spectroscopy was used to study the -CpEt? and -OH? surface species during MnO ALD and also monitored the bulk vibrational modes of the growing MnO films. The results allowed a growth mechanism to be established for MnO ALD using Mn(CpEt)₂ and H₂O. Only 54% of the Mn sites are observed to retain the -CpEt? surface species after the Mn(CpEt)₂ exposure. Efficient MnO ALD using Mn(CpEt)₂ and H₂O should be useful for a variety of applications where metal oxides are required that can easily change their oxidation states.     

Growth and characterization of epitaxial anatase TiO2(001) on SrTiO3-buffered Si(001) using atomic layer deposition

Epitaxial anatase titanium dioxide (TiO₂) films have been grown by atomic layer deposition (ALD) on Si(001) substrates using a strontium titanate (STO) buffer layer grown by molecular beam epitaxy (MBE) to serve as a surface template. The growth of TiO₂ was achieved using titanium isopropoxide and water as the co-reactants at a substrate temperature of 225-250 °C. To preserve the quality of the MBE-grown STO, the samples were transferred in-situ from the MBE chamber to the ALD chamber. After ALD growth, the samples were annealed in-situ at 600 °C in vacuum (10^− 7 Pa) for 1-2 h. Reflection high-energy electron diffraction was performed during the MBE growth of STO on Si(001), as well as after deposition of TiO₂ by ALD. The ALD films were shown to be highly ordered with the substrate. At least four unit cells of STO must be present to create a stable template on the Si(001) substrate for epitaxial anatase TiO₂ growth. X-ray diffraction revealed that the TiO₂ films were anatase with only the (004) reflection present at 2θ = 38.2°, indicating that the c-axis is slightly reduced from that of anatase powder (2θ = 37.9°). Anatase TiO₂ films up to 100 nm thick have been grown that remain highly ordered in the (001) direction on STO-buffered Si(001) substrates.     

Initial stages of high-temperature CaF2/Si(001) epitaxial growth studied by surface X-ray diffraction

Surface X-ray diffraction was applied to study structure of the fluorite-silicon interface forming upon epitaxial growth of CaF2 on Si(001) surface kept at 750 degrees C. Samples with CaF2 coverage of 1.5-4 (110)-monolayers were grown and in-situ characterized using synchrotron radiation. The 3 x 1-like surface reconstruction was observed in agreement with the previous studies by electron diffraction. Interestingly, a well pronounced splitting of the fractional x 1/3 reflections was revealed. This splitting was ascribed to the effect of antiphase domain boundaries in the row-like structure of the interface layer. The in-plane integrated intensities were used to reconstruct two-dimensional atomic structure of the high-temperature CaF2/Si(001) interface.