Abnormal growth of “giant” grains in silver thin films

Abnormal growth of “giant” grains in the millimeter range was observed in silver thin films with thicknesses of 2.0 and 2.4 μm. The effect depends on deposition temperature and deposition geometry. The microstructure and texture of as-deposited and annealed films have been characterized using X-ray, electron backscatter diffraction (EBSD) and focused ion beam (FIB) techniques. Abnormal grain growth is found whenever a special texture is formed during film deposition. Otherwise normal grain growth occurs. The texture type—and thus the grain growth mode—can be controlled by adjusting the process parameters. During abnormal grain growth, the initial 〈111〉 texture transforms completely into 〈001〉. Growth of 〈111〉-oriented grains stagnates at a size smaller than the film thickness with a non-columnar grain structure. This stagnation promotes orientation-selective growth of 〈001〉 grains.     

多晶沉积薄膜生长过程中织构演变的模拟研究

将织构组态熵的概念应用于沉积多晶薄膜织构演变的模拟研究,考虑膜沉积过程中晶体表面能各向异性及应变能各向异性的变化,建立了沉积薄膜晶体择优生长的定量模型;模拟了Ａｌ多晶薄膜沉积过程中晶体的生长规律,分析了织构演变的主要微观物理因素。     

内应力对金属薄膜生长织构的影响

基于FS型原子镶嵌势（EAM热）用分子动力学模拟了金属多晶薄膜的原子沉积生长过程，通过预设恒定应变在薄膜生长过程中引入了单轴压应力，模拟研究了应力对呈丝织构的多晶薄膜中沿丝轴旋转取向择优的影响，模拟结果表明，在固定压应变条件下，最密排方向偏离压应力轴的晶粒较为优先生长发展；在生长过程中，取向择优的晶粒从沉积表面开始逐渐扩张吞并相邻晶粒，模拟结果还显示，这种生长织构的发展随沉积膜厚增加有显著的临界特征，在织构发展过程中被吞并的晶粒局部出现孪晶，继而转换为择优生长晶粒的结构，在被吞并的晶粒最终消失处将会留下失配位错。     

Characterization of CuInS2 thin films prepared by sulfurization of Cu-In precursor

CuInS2 thin films were prepared by sulfurization of Cu-In precursors. The influences of the deposition sequence of Cu and In layers, such as Cu/In, Cu/In/In, and In/Cu/In, on structure, topography, and optical properties of CuInS2 thin films were investigated. X-ray diffraction results show that the deposition sequence of Cu and In layers affects the crystalline quality of CuInS2 films. Atomic force microstructure images reveal that the grain size and surface roughness are related to the deposition sequence used. When the deposition sequence of precursor is In/Cu/In, the CuInS2 thin films show a single-phase chalcopyrite structure with （112） preferred orientation. The surface morphology of CIS films is uniform and compacted. The absorption coefficient is larger than 10^4 cm^-1 with optical band gap Egclose to 1.4 eV.     

Stress and microstructure evolution in thick sputtered films

Materials synthesized by deposition techniques are often plagued by high levels of residual stress. While the origin and control of this stress in thin (sub-micron) films has been an active area of research, it is not clear how the results extrapolate with thickness. In the present work, in situ residual stress measurements are performed during the sputter deposition of beryllium, spanning the transition from thin to thick. Variables including sputtering gas pressure and substrate biasing are shown to strongly affect both the average and instantaneous stress levels measured during film growth. Detailed microstructural characterization is performed to assess the grain structure, surface morphology, and crystallographic growth texture of representative specimens. The microstructure is correlated with theoretical models of stress generation to interpret experimental measurements. A stress map is also constructed, generalizing the effects of processing and material parameters on stress state.     

Highly c-axis Oriented YBCO Thin Films Deposited on Cold Rolling Ag Substrates and Textures of Cold-Rolling and Recrystallization in Ag

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Origins of microstructure and stress gradients in nanocrystalline thin films: The role of growth parameters and self-organization

The development of depth gradients of texture, morphology and stresses in thin nanocrystalline films was experimentally demonstrated for a nanocrystalline CrN film by means of position-resolved synchrotron X-ray nanodiffraction and explained by atomistic processes at the growing film surface and the effect of interfaces, both controlled by the deposition conditions. Controllable changes in the energy of incident particles adjusted by bias voltages ranging from ?40 to ?120 V affect the competitive growth of grains with different orientations, induce disruption of grain growth and thus give rise to structural variations across the film thickness. Subsequent changes in the volume fraction of grain boundaries and film texture were found to be responsible for changes in the residual stress state as defect generation proceeds to different extents in the interior of differently oriented grains and in the interfacial area. While the defect density predominantly affects the development of intrinsic stress, the variation in the number of weakly bonded atoms of grain boundaries determines the thermal stress component. The structural dependence of both stress components thus contributes to the characteristic development of stress gradients in thin nanocrystalline films.     

靶基距对Cu/Si(100)薄膜结构和残余应力的影响

采用高功率调制脉冲磁控溅射(MPPMS)技术在 Si(100)基体上沉积 Cu 薄膜,SEM 观察薄膜厚度及生长特征、XRD 分析薄膜晶体结构、nanoindentor 测量薄膜纳米硬度和弹性模量、Stoney 公式计算薄膜残余应力,研究沉积过程靶基距对 Cu / Si(100)薄膜沉积速率、微结构及残余应力的影响。 随着靶基距的增大,薄膜沉积速率降低,薄膜的生长结构由致密 T 区向 I 区转变,Cu(111)择优生长的晶粒逐渐减小,薄膜纳米硬度和弹性模量也相应降低,残余拉应力约为 400 MPa。 较小靶基距时增加的沉积离子通量和能量,决定了薄膜晶粒合并长大体积收缩过程的主要生长形式,导致了 Cu / Si(100)薄膜具有的残余拉应力状态。 MPPMS 工艺的高沉积通量和粒子能量可实现对 Cu / Si(100)薄膜残余应力的调控。     

Effect of magnetic fields on pulse plating of cobalt films

Magnetic fields parallel to the electrodes were introduced during a pulse plating process to obtain cobalt thin films from alkaline baths. Ef-fects of different magnetic intensities on the composition, microstructure, and magnetic properties of cobalt thin films were investigated. It was found that the deposition speed increased gradually with the increase of magnetic intensity. Almost all of the deposited films were crys-talline and showed Co(002), Co(100) peaks. With the rise on the magnetic intensity, the intensity of Co (002) peak raised gradually. Mag-netic fields would induce cobalt growing along (002) orientation. The films were densely covered with typical nodular structure. Films of smaller grain size and smooth surface could be formed under high magnetic intensity (1 T) as a result of magnetic force and MHD effects. Moreover, higher magnetic intensity induced larger saturation magnetization and lower coercivity. With the rise on magnetic intensity, cobalt contents in the films increased gradually, which led to the rise of saturation magnetization.     

衬底与缓冲层的晶格失配对CeO_2缓冲层外延生长的影响

采用金属有机沉积(MOD)技术在La Al O3(LAO)、Y稳定的氧化锆(YSZ)和Ni-W衬底上沉积了Ce O2缓冲层薄膜,并研究了衬底与缓冲层的晶格失配对其外延生长的影响。结果表明,随着衬底和缓冲层薄膜之间晶格失配的增大,缓冲层薄膜内部的压应变增加,晶界浓度增加,晶粒生长速率减小。衬底和缓冲层薄膜之间的晶格失配越小,越有利于薄膜织构度的增大。Ce O2薄膜的表面形貌及粗糙度的演化对衬底和缓冲层薄膜之间的晶格失配并没有明确的依赖关系。     

Morphological, structural, and mechanical characterizations of InGaN thin films deposited by MOCVD

Presented in this study are surface roughness, crystalline structure, and nanomechanical properties of InGaN thin films deposited under various growth temperatures, obtained by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and nanoindentation techniques. The InGaN thin films with different In contents were deposited on sapphire substrates through a metal-organic chemical-vapor deposition (MOCVD) system. Changes in mechanical properties for InGaN thin films are discussed in conjunction with deposition temperature, surface morphology and crystalline structure. The XRD measurements showed that there was no phase separation of In as the In composition went from 25 at.% to 34 at.%. Moreover, both XRD and AFM showed larger grain and surface roughness in In_0.25Ga_0.75N thin films. Nanoindentation results indicate that hardness and Young's modulus both decreased as the indentation depth increased. The contact stress–strain relationships were also analyzed.     

Nd-Fe-B薄膜的磁控溅射法制备与组织结构

对直流磁控溅射法制备Nd-Fe-B薄膜工艺进行了研究.在不同的溅射功率、溅射气压、溅射时间等条件下制备薄膜,并对薄膜进行了AFM、XRD分析.结果表明,Nd-Fe-B薄膜的沉积速率、表面形貌及相结构与溅射功率、溅射气压、溅射时间密切相关.薄膜的沉积速率随磁控溅射功率的增加而增加,薄膜表面晶粒尺寸和表面粗糙度随溅射功率增加而增大.沉积速率随溅射气压的升高先增大后减小.低功率溅射时,薄膜中出现α-Fe、Nd2Fe14B相相对较少,随溅射功率增加,α-Fe相消失,Nd2Fe14B相增多.综合考虑各种因素,最佳溅射功率为100～130 W.     

Synthesis and characterization of Cu2ZnSnS4 thin films grown by PLD: Solar cells

As-deposited and annealed Cu₂ZnSnS₄ (CZTS) thin films have been synthesized onto Mo coated glass substrates at different deposition times using pulsed laser deposition (PLD) technique. The effect of deposition time (film thickness) and annealing onto the structural, morphological, compositional and optical properties of CZTS thin films have been investigated. The polycrystalline CZTS thin films with tetragonal crystal structure have been observed from structural analysis. FESEM and AFM images show the smooth, uniform, homogeneous and densely packed grains and increase in the grain size after annealing. The internal quantitative analysis has been carried out by XPS study which confirms the stoichiometry of the films. The optical band gap of CZTS films grown by PLD is about 1.54 eV, which suggests that CZTS films can be useful as an absorber layer in thin film solar cells. Device performance for deposited CZTS films has been studied.     

Effect of substrate bias voltage on the texture and microstructure of Cu thin films deposited by ion beam deposition

Cu thin films deposited by non-mass separated ion beam deposition under various substrate bias voltages were investigated. The film textures and microstructure were analyzed by X-ray diffraction and field emission scanning electron microscopy, and the resistivity of the film was measured with the Van der Pauw method. It was found that the optimum negative substrate bias voltage for Cu films was −50 V. The Cu films deposited without substrate bias voltage showed a columnar grain structure with small grains and random orientation. However, when a substrate bias voltage of −50 V was applied, the Cu films had a non-columnar structure with a strong (111) texture and large grains. The electrical resistivity of the Cu films decreased remarkably with increasing negative substrate bias voltage, and reaching a minimum value of 1.8±0.13 μΩ cm at the substrate bias voltage of −50V.     

Converting polycrystals into single crystals – Selective grain growth by high-energy ion bombardment

Common failure mechanisms in microelectronics such as electromigration, creep and fatigue can be positively influenced by microstructure optimization. In this paper a new mechanism of microstructure optimization in thin metal films is proposed. Post-deposition ion bombardment can produce an in-plane texture in originally highly fiber textured thin metal films by a selective grain growth process. In extreme cases the in-plane texture becomes as sharp as the out-of-plane fiber texture. A subset of grains oriented for ion channeling was found to grow significantly at the expense of the remaining grain fraction. We studied the selective grain growth as a function of ion species (N⁺, Ne⁺, Ar⁺), ion energy (1–3.5 MeV) and target temperature (liquid nitrogen to 400 °C). In a textured thin film the degree of preferred in-plane orientation can be strongly influenced by ion bombardment, and therefore this technique has the potential to become a powerful tool for the enhancement of reliability in micro- and nanosystems.     

Room-temperature growth of high-purity titanium nitride by laser ablation of titanium in a nitrogen atmosphere

Thin films of titanium nitride (TiN) were deposited on glass substrates by KrF excimer laser ablation of titanium over a very broad nitrogen pressure range with different target–substrate distances at room temperature. The as-deposited TiN thin films were analyzed by X-ray diffraction and transmission electron microscopy. It was found that the as-deposited thin films are normally a mixture of TiN and metallic titanium, and the TiN-to-Ti ratio of the as-deposited thin film depends on both the nitrogen pressure and the target–substrate distance. High-purity TiN thin films can be obtained only in a very narrow deposition parameter range. A compound parameter (the product of the nitrogen pressure and the target–substrate distance) is proposed to optimize the deposition of high-purity TiN thin films, and the possible mechanism is also discussed. It was also revealed that the as-deposited TiN thin films are polycrystalline with an average grain size of about 20 nm.     

Texture in films: Selected examples

The paper contains a brief discussion of research on texture and properties of films. Three examples are selected to illustrate problems of understanding of texture development and correlation between texture and properties of films. Various correlations between texture related structural characteristics of film and probability of failure of Al-Cu interconnects line are presented to illustrate the need for a better understanding of the correlation between texture and failure mechanism. Another example on development of texture in nickel films illustrates processes that influence texture development and type of interfaces between oxide grains. It is demonstrated that texture and grain boundary character distribution decides the rate of oxidation of Nickel. An example of Co-Cr films for magnetic recording media illustrates an important role of texture in controlling the magnetic properties of films for application in perpendicular magnetic recording. Principles of methods that are used to calculate texture influence on magnetic properties are discussed.     

脉冲激光沉积及硒化法制备Cu(In,Ga)Se2薄膜研究

采用脉冲激光沉积和硒化后热处理的方法在石英衬底上制备Cu(In,Ga)Se2（简写为CIGS）薄膜,研究脉冲激光沉积（PLD）技术在制备CIGS薄膜太阳能电池材料上的应用,分析了不同预制层沉积顺序及厚度对CIGS薄膜组织结构、表面形貌、成分以及光学性能的影响。实验结果表明：(1)利用PLD技术及后硒化处理的工艺,制得的CIGS太阳能电池吸收层具有纯相和高结晶度等特性;(2)CuGa/In金属预制层的叠层顺序和叠层数、硒化退火温度对薄膜的结晶质量、晶粒尺寸、成分都具有重要的影响,其中叠层顺序影响最为明显;(3)样品均表现出对可见光区具有透射率低和吸收系数高的光学特性。本工作为制备性能优良的CIGS太阳能电池吸收层,提供了一个新颖的工艺手段。     

Stress Study on CrN Thin Films with Different Thicknesses on Stainless Steel

The reliability of a substrate curvature-based stress measurement method for CrN thin films on substrate with fluctuant surface was discussed. The stress error led by the ignorance of substrate thermal deformation was studied. Results showed that this error could be as large as several hundred MPa under general deposition conditions. Stress in the CrN thin films with different thicknesses ranging from 110 to 330 nm on stainless steel was studied by this method, in comparison with conventional results on silicon wafer. The thin films' morphology and structure were investigated and related to the film stress. A significant result of the comparison is that stress evolution in the thin films on steel obviously differs from that on silicon wafer, not only because the two substrates have different coefficients of thermal expansion, which provokes thermal stress, but also the considerable discrepancy in the thin films' grain coarsening rate and structure that induce different intrinsic stresses.     

Influence of Oblique Sputtering on Stripe Magnetic Domain Structure and Magnetic Anisotropy of CoFeB Thin FilmsEI北大核心CSCD

Magnetic anisotropy is one of the most important fundamental properties of magnetic thin film. The strength of magnetic anisotropy determines the ferromagnetic resonance frequency of magnetic films in the high-frequency applications. Because of the directionality of conventional static magnetic anisotropy in magnetic film, the high-frequency device usually shows an obvious directionality. When the microwave magnetic fi eld deviates from the perpendicular direction of magnetic anisotropy, the devices cannot reveal their best performance. The magnetic film with a stripe magnetic domain structure displays an in-plane rotatable magnetic anisotropy, which can be an important strategy to solve the problem of magnetic fi eld orientation dependent performance in high-frequency device. Therefore, the magnetic domain, the magnetic anisotropy, and the high-frequency behaviors for magnetic fi lms with a stripe magnetic domain structure have received extensive attention. Previously, most of the studies focused on the stripe magnetic domain structure of polycrystalline thin films. However, less attention was paid on amorphous magnetic thin films. Since the amorphous magnetic films have no long-range ordered crystal structure, no magnetocrystalline anisotropy, no grain boundary defects resistance hindering the domain wall displacement, they usually show excellent soft magnetic properties and have been widely applied in high-frequency devices. CoFeB alloy is one of the most important amorphous magnetic materials and has been extensively applied in various spintronic devices. In this work, amorphous CoFeB magnetic thin films were prepared by using a method of oblique sputtering technique at room temperature. The influences of oblique sputtering on the stripe magnetic domain structure, the in-plane static magnetic anisotropy, the in-plane rotational magnetic anisotropy, and the perpendicular magnetic anisotropy of the amorphous CoFeB films were studied by scanning probe microscope, vibrating sample magnetometer, ferromagnetic resonance. It is found that the method of oblique sputtering could effectively reduce the critical thickness for the appearance of stripe magnetic domain in amorphous CoFeB films. For a non-oblique sputtered CoFeB film, the critical thickness for the appearance of the stripe magnetic domain is above 240 nm. In contrast, after been subjected to the oblique sputtering, the critical thickness becomes below 240 nm. The different magnetic characterizations indicate that for the growth of CoFeB films with stripe magnetic domain structure, the oblique sputtering could not only enhance the strength of in-plane static magnetic anisotropy, but also improve the in-plane rotational magnetic anisotropy and the perpendicular magnetic anisotropy. All of the magnetic anisotropies are increased with the angle of oblique sputtering. The observation results of XRD and TEM prove that the prepared CoFeB thin films tend to amorphous structure. The characterization of SEM observation indicates that although the amorphous CoFeB films do not possess long-range ordered crystalline structure, they still could form a kind of columnar structure. The slanted columnar structure of CoFeB films could significantly increase the perpendicular magnetic anisotropy, thus lead to the appearance of stripe magnetic domain structure.