Cu掺杂对Be薄膜微结构的影响(英文)

利用离子束溅射法在硅基底上制备高纯Be薄膜并实现Cu元素的可控掺杂,利用X射线能谱、扫描电镜、X射线衍射以及透射电镜等对Cu掺杂Be薄膜进行表征分析。研究结果表明:Cu元素在Be膜内分布均一,且Cu掺杂量对Be薄膜的微观结构有显著影响。Cu掺杂能抑制Be晶粒生长,Be晶粒随着薄膜中Cu含量的增多而减小,并且尺寸分布更加均匀;Cu掺杂影响Be晶粒的生长取向,使其形成更为紧凑的薄膜结构。这些因素使得掺杂Cu的Be薄膜的表面粗糙度明显降低。     

氮气流量对磁控溅射法沉积NGZO薄膜性能的影响

目的通过磁控溅射镀膜工艺,在玻璃上制备高质量的氮镓共掺杂氧化锌(NGZO)薄膜。方法采用射频磁控溅射法,同时通入氩气和氮气,在流量比分别为25/10、25/20、25/25、25/30((m L/min)/(m L/min))条件下制备NGZO薄膜。通过XRD和SEM对薄膜的物相结构和表面形貌进行分析,通过紫外/可见分光光度计和霍尔效应测试仪对薄膜透过率和载流子浓度、迁移率及薄膜电阻率进行研究。结果与未掺入N的Ga掺杂氧化锌(GZO)薄膜相比,在可见光区,尤其是600~800 nm范围内,NGZO薄膜平均透过率在80%以上,符合透明导电薄膜透过率的要求。GZO薄膜载流子浓度较高,电阻率较低,而掺入N后薄膜的载流子浓度和迁移率有所下降,电阻率有所增加。结论在N-Ga共掺杂薄膜中,N的掺杂主要占据O空位,并吸引空位周围的电子,这减小了薄膜晶格畸变,并产生电子空穴,最终使得薄膜中电子载流子浓度降低,空穴载流子浓度增加,电阻率有所增加。随着氮气流量的变化,发现在25 m L/min时,薄膜具有最佳的综合性能。这种薄膜可用于紫外光探测器等需较大电阻率的应用中,并有望实现n-p型转化。     

Effect of grain size on nanomechanical property Ni80Fe20 thin film

The purpose of this paper is to describe the results of this study into the structure and nanomechanical properties of Ni₈₀Fe₂₀ thin film. The films were sputtered onto glass substrates with thicknesses of 500 Å, 1000 Å, and 1500 Å, respectively. These three thicknesses were tested both at room temperature (RT) and with a post-annealing heat treatment temperature of 250 °C for 1 h. The plane-view microstructure was observed under a high-resolution transmission electron microscope (HRTEM) to determine grain distribution. The selected area diffraction (SAD) pattern was obtained with the HRTEM to investigate NiFe microstructures. Electron diffraction patterns demonstrated that NiFe thin film has a face-centered cubic (FCC) structure and strong NiFe (111) crystallization. Annealing treatment increased the grain size distribution of the thin film. The grain size is increased at the thicker thickness of NiFe thin film. Nano-indentation was used to measure hardness and Young's modulus; based on these results and the grain size, the decline of hardness can be reasonably inferred from an enlarged grain size, which is consistent with the Hall–Petch effect. However, the rising Young's modulus measurement can be reasonably associated with the effect of the sputtered adhesion of NiFe thin film.     

Effect of bias on the As-deposited grain structure of Cr thin film

The film growth of Cr thin film by DC-magnetron sputter deposition was investigated by experimentally measuring the evolution of grain size distribution and by computing the film growth using Monte Carlo simulation. The as-deposited Cr thin film by sputter deposition typically grows in a columnar grain structure at the substrate temperature 260°C, which is far lower than 0.3 T_m. The stagnation of columnar grain structure does not occur in the case of no-bias condition up to the investigated film thickness of about 800 nm. However, the application of a negative bias of 200 V results in a stagnation of columnar grain structure at film thickness of about 50 nm and at the deposition temperature of 260°C. This is believed to arise from the fact that the mobility of ad-atoms is greatly enhanced and the Ar+ ions pin the grain boundary as a result of bias application. This article is based on a presentation made in the 2002 Korea-US symposium on the “Phase Transformation of Nano-Materials,” organized as a special program of the 2002 Annual Meeting of the Korean Institute of Metals and Materials, held at Yonsei University Seoul, Korea on October 25–26, 2002.     

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.     

直流等离子体CVD金刚石薄膜微观结构分析

采用直流等离子体CVD法制备了金刚石膜，利用X射线衍射、光学显微镜、扫描电镜、激光拉曼光谱等技术研究了金刚石膜的微观组织，晶粒择优取向生长过程。结果表明：开始形核时，晶粒随机无择优生长；对基体表面氢刻蚀预处理，有利于晶胚形核长大。甲烷浓度对金刚石膜晶粒择优取向生长有重要影响：甲烷浓度较低时，金刚石膜（100）面择优生长，形成以（111）为主的八面体晶体，并且可以制取中心和边缘均匀、高质量光学级自支撑金刚石膜，但生长速率慢，效率低。同时也发现金刚石膜存在空位、孔洞等缺陷。     

Study of the grain growth mechanism of CoPt/Cn thin film for magnetic recording media using the Monte Carlo simulation

The effect of carbon addition on the grain growth and ordering kinetics of CoPt film has been studied experimentally by sputter-depositing a monolithic CoPt-20 at.%C film of 24nm. The carbon addition of 20 at.% to CoPt thin film in the form of CoPt (20nm)/C_n (4 nm) (n=1, 4) significantly reduced both the grain growth and ordering kinetics. Reducing the thickness of the carbon layer, i.e. from n=1 to n=4, led to a much finer grain size distribution as well as to a finer grain size. The Monte Carlo simulation study indicated that the decrease of grain growth and ordering kinetics is primarily due to a continuous decrease of the mobility of the order—disorder inter-phase with the progress of the ordering reaction. Reduction of the inter-phase mobility can eventually lead to a stable two phase grain structure inter-locked by low mobility inter-phase and is responsible for the formation of a fine grain size distribution in the CoPt/C_n film with n=4.     

Carrier transportation in polycrystalline CuInSe_2 thin films with Cu-deficient grain boundaries

The interface energies and electronic structures of(112) grain boundaries of Cu In Se2 thin films were investigated by first-principle calculations.It is found that the grain boundary with a Cu vacancy has low interface energy and exists widely in the films.The Cu deficiency may cause the charge imbalance and result in an upward band bending at the grain boundary.It also weakens the repulsion between Cu-3d orbital and Se-4p orbital and leads to the downward shift of valence band maximum.The two mechanisms,namely the band bending from the charge imbalance and the depression of the valence band maximum, have effects on the(112) grain boundaries with different defects.The change of band structure forms a potential barrier to prevent electrons or holes from approaching the grain boundary and reduces their recombination.This might be used to explain the effects of the grain boundary on carrier transportation and why polycrystalline Cu(In,Ga)Se2thin film solar cells have better performance than single-crystal cells.     

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.     

Effects of bending fatigue on the electrical resistance in metallic films on flexible substrates

The increase of electrical resistance during the strain-controlled bending fatigue of 2 μm-thick inkjet-printed or vacuum deposited metallic films (Cu, Ag) on flexible substrates (BT: Bismaleimide Triazine, PI: Polyimide) was investigated. Electrical resistance increased with an increase in the number of fatigue cycles. The rate of increase in the electrical resistance of inkjet-printed Cu films was lower than that of thermally evaporated films. This phenomenon is attributable to the porous microstructure of inkjet-printed Cu films. The porous structure contains a lot of free volume and a large area of free surface, which can be a sinking site for vacancies formed during the cyclic deformation. It was confirmed that a smaller grain size leads to a lower rate of increase in the electrical resistance, which was ascribed to the easy vacancy annihilation due to a short diffusion length of the vacancy to the grain boundary which is a vacancy sinking site. The rate of increase in the electrical resistance was also influenced by the grain boundary geometry. The lower rate of the evaporated Ag film on a BT substrate was attributed to the crack-like grain boundaries, which were expected to behave like pores.     

非晶态SrTiO3薄膜的快速晶化处理

在Si(111)基片上采用脉冲激光沉积(PLD)方法,烘烤温度300℃,制备得到非晶态SrTiO3薄膜.采用快速晶化处理,将非晶态SrTiO3薄膜在不同温度、不同晶化处理时间下进行了晶化处理,采用GIXRD和AFM分析检验晶化的效果和表面形貌.结果表明,SrTiO3晶化程度强烈依赖处理温度,处理温度越高,晶化程度越高;在同一温度下,增加处理时间有助于提高晶化效果,并获得致密、表面平整、均匀的SrTiO3晶态薄膜;晶粒大小不随晶化处理时间明显变化.在快速晶化处理过程中,非晶态SrTiO3薄膜在极短时间内达到晶化温度,并形成大量晶核,从而使晶粒生长受到限制,有利于获得更好的晶化效果.     

溶胶-凝胶法制备掺铁钛酸铋铁电薄膜光学性能的研究

通过溶胶-凝胶法制备了不同掺杂浓度的Fe-BTO铁电薄膜以减小其光学带隙,研究不同Fe掺杂浓度对BTO铁电薄膜铁电光伏效应的影响。结果表明,使用溶胶-凝胶法对BTO铁电薄膜掺杂不同浓度的Fe,所制备的薄膜结晶度较好、网状结构明显、空间分布均匀,晶粒大小均一;通过溶胶-凝胶法制备Fe-BTO铁电薄膜在Fe掺杂浓度x=0.9附近可以明显减小其禁带宽度。     

PECVD法制备掺硼纳米金刚石薄膜的工艺研究进展

首先详细介绍了金刚石作为半导体材料的优异性能,然后从应用角度阐述了NCD薄膜掺B后形成半导体材料的优势,接着探讨了影响NCD薄膜性能(电性能、光学性能、生物性能等)的主要工艺条件(包括硼源种类、掺硼浓度、衬底温度、后处理)。研究发现,大多数研究者都采用液态和气态硼源,而固态硼源由于很难液化且浓度不易控制而不常被采用,掺B后NCD薄膜的电阻率急剧下降,紫外波段下透过率可达51%,磁阻效应变好。另外衬底温度对BD-NCD薄膜的质量以及性能都有影响,衬底温度太高,非晶碳含量增加,金刚石质量下降;衬底温度太低,能够进入NCD晶界或晶粒的有效硼原子减少,影响其电学性能、光学性能,在最佳衬底温度工艺下的电导率可达22.3 S/cm,而在电化学性能方面,其电化学窗口可达3.3 V。而选择合适的硼源浓度对BD-NCD的电性能、光学性能、生物性能也非常关键,硼源浓度过大,BD-NCD表面粗糙度和晶粒尺寸增大;硼源浓度过小,产生空穴进行导电的B原子就少,在合适硼源浓度工艺条件下其载流子浓度可达1021 cm-3,折射率可达2.45。还有研究者对BD-NCD薄膜进行后处理工艺(退火、等离子体处理等),发现后处理对其电性能也有一定的影响。因此,选择合适的工艺对生长质量高、性能优异的NCD薄膜尤为重要。最后对BD-NCD薄膜的发展以及后续研究方向进行了展望和期待。     

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。     

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。     

离子束辅助沉积法制备重掺N氧化铈提高其可见光吸收性能

氧化铈是一种潜在的可见光催化材料,但是如何实现在氧化铈晶格内的N掺杂是阻碍其发展的主要原因。本研究中,我们采用离子束辅助沉积法制备了N掺杂的氧化铈薄膜材料,采用该方法实现了对氧化铈薄膜的高含量N掺杂,N含量可高达25%,远远高于采用传统方法制备的氮掺杂氧化铈。N 1s的高分辨谱显示,掺杂的N替代了氧化铈中的O而实现了N在氧化铈晶格中的掺杂。XRD结果显示,氧化铈薄膜在生长过程中,N离子的轰击并没有改变氧化铈的晶体结果,但是改变了氧化铈薄膜表面形貌,从SEM结果上可以看出氧化铈表面颗粒变得细小,薄膜表面变得光滑。紫外可见吸收光谱结果显示,随着掺N量的增加,氧化铈的光吸收发生红移。     

Substitutional diffusion and Kirkendall effect in binary crystalline solids containing discrete vacancy sources and sinks

We investigate vacancy-mediated diffusion in a binary substitutional alloy by explicitly accounting for discrete vacancy sources and sinks. The regions between sources and sinks are treated as binary crystals with a perfect lattice structure containing a dilute concentration of vacancies. The sources and sinks are assumed ideal, maintaining an equilibrium vacancy concentration in their immediate vicinity. Diffusion within the perfect lattice is described with a diffusion-coefficient matrix determined by kinetic Monte Carlo simulations for a binary, thermodynamically ideal alloy in which the components have different vacancy-exchange frequencies. Continuum simulations are performed for diffusion couples with discrete grain boundaries acting as vacancy sources and sinks. Effective grain coarsening due to the Kirkendall effect is observed even in the absence of Gibbs-Thomson driving forces. As in standard ternary systems, uphill diffusion is observed. We also find that the drift of the lattice frame of reference as a result of the Kirkendall effect increases with the source/sink density. Upon increasing the density of vacancy sources and sinks, we recover the conventional treatment of substitutional diffusion, which assumes a dense and uniform distribution of vacancy sources and sinks that maintain an equilibrium vacancy concentration throughout the solid. The inverse Kirkendall effect, where the slower component segregates at grain boundaries acting as vacancy sinks, is also observed in the simulations.     

Thermodynamic effects on the kinetics of vacancy-generating processes

The inhibiting effect of vacancies on the very process in which they are generated is considered from a thermodynamic viewpoint. Examples of such processes treated here in some detail are grain growth and pore dissolution. It is shown that these processes are inhibited due to vacancy generation. A particular scenario discussed implies intermittent “locking”. After a period of uninhibited kinetics the process comes to a halt due to a thermodynamic back force “locking” it. It can only re-start once the vacancies produced are removed by diffusion. This repetitive cycle leads to an overall reduction in the rate of the kinetic process in question. Specific predictions with regard to grain growth in fine-grained (particularly nanocrystalline) materials and void dissolution kinetics in sintering are made. A third example considered is vacancy drag on a moving individual grain boundary. The magnitude of the drag is re-assessed by taking into account the Gibbs free energy of the vacancies generated.     

通过氢还原热处理提升TiO2薄膜的抗菌性能

提升在可见光区间的抗菌效率一直是二氧化钛(TiO₂)抗菌性能研究的重要方向。采用脉冲激光沉积(PLD)制备TiO₂薄膜,并通过氢还原热处理的方法提升TiO₂表面的氧空位浓度从而增强其抗菌性能。结果发现,在以单晶氧化钇稳定的氧化锆(YSZ)为衬底时,生长的TiO₂薄膜为高度择优取向的锐钛矿相。生长温度越高,锐钛矿相的XRD衍射峰越强,薄膜越致密。将在600℃下生长的350 nm厚的TiO₂薄膜进行抗菌性能测试,发现其抗菌率约为86%。对样品进一步在4%H2氛围下进行还原处理,发现其抗菌率提升到约为97%。通过XPS、UV-Visible和PL测试,发现TiO₂经过还原热处理后在其表面形成更多的氧空位,在TiO₂带隙中形成氧空位缺陷能级,导致在可见光区域吸光性能增强,使其具有更高的抗菌性能。通过氢还原过程调控材料的缺陷组成,并研究TiO₂薄膜的光催化抗菌性能及抗菌机理。这种简易的调控TiO₂光吸...     

Determination of the Diffusivity of Point Defects in Passive Films on NiTi and NiTiAl Alloys

A point defect model based on the movement of cation and anion defects in an electrostatic field was carried out to explain the growth and dissolution behavior of a passivation layer on NiTi and NiTiAl thin films. The calculated value of diffusivity was in range of 10⁻¹⁶ to 10⁻¹⁷ cm²/s. The defect of oxygen vacancy revealed that the passive film was an n-type semiconductor. Mott-Schottky analysis showed that the doping level within a passive film was rather large and in the order of 10²⁰ to 10²¹ cm⁻³ film, which was considered to be a highly doped structure. The high-resolution transmission electron microscopy (HRTEM) images showed that the highly doped structure consisted of amorphous and crystalline structures of TiO₂ and Al₂O₃, respectively. A thermodynamic evaluation for the difference between crystalline and the fully amorphous oxides was calculated to be 57.57 and 96.87 kJ/mol, respectively. In the amorphous region, the electronic level arises from the presence of an energy band gap in the ideal crystalline structure. Therefore, the smaller donor density and the lower diffusion coefficient retarded the defect movement in the passivation layer, and improved the stability of the passive film during corrosion.