Effects of Interface and Grain Boundary on the Electrical Resistivity of Cu/Ta Multilayers

The electrical resistivity of Cu/Ta multilayers deposited by radio-frequency magnetron sputtering on a polyimide substrate was investigated as a function of monolayer thickness.It is found that the resistivity of the multilayer increases with decreasing monolayer thickness from 500 nm to 10 nm.Two significant effects of layer interface scattering and grain boundary scattering were identified to dominate electronic transportation behavior in the Cu/Ta multilayers at different length scales.The electrical res...     

Structural and magnetic characterization of electrodeposited Ni/Cu multilayers

Ni/Cu multilayers were electrodeposited from a single solution electrolyte by galvanostatic method. Interface roughness, magnetization and magneto-transport studies of Ni/Cu multilayers on Si(1 1 1)/Ti/Cu substrate were carried out for samples deposited from three different electrolytes, viz. pure sulphate, sulphate–citrate and sulphate-polyethylene glycol-8000 (PEG-8000). The top Ni-layer morphology of these samples was characterized by atomic force microscope (AFM). Detailed analysis of the morphological data showed a typical two-dimensional fractal growth pattern in all the three cases. The structural parameters like interface roughness, density and thicknesses of Ni and Cu layers were extracted from neutron reflectivity (NR) study. The order of interface roughness obtained from NR and AFM was found to be quite close. The sample deposited from sulphate–citrate electrolyte was found to have minimum interface roughness. The polarized neutron reflectometry (PNR) measurement showed reduced magnetic moment value (∼0.41 ± 0.01 μ_B) for nickel layers compared to bulk value in all the three samples. The magnetoresistance (MR) of these samples were measured at room temperature. An attempt has been made to explain the observed MR results in terms of granular structure and scattering mechanism involving super-paramagnetic and ferromagnetic particles in these samples.     

基底温度对直流磁控溅射制备氮化铜薄膜的影响研究

采用反应直流磁控溅射镀膜法,在氮气分压为0.9Pa、不同基底温度下、玻璃基底上制备了纳米多晶Cu3N薄膜,并研究了基底温度对薄膜结构和性能的影响。结果表明,当基底温度为100℃及以下时,薄膜以[111]方向择优生长为主;在150℃及200℃时,薄膜以[100]方向择优生长为主;250℃时开始出现Cu的[111]方向生长,300℃时已完全不能形成Cu3N晶体,只有明显的Cu晶体。随基底温度的升高,薄膜的沉积速率在13～28nm/min呈U型变化,低温和高温时较高,150℃时最低;薄膜的电阻率显著降低;薄膜的显微硬度先升后降,100℃时显微硬度最大。     

基底温度对直流溅射Nb掺杂TiO2薄膜性能的影响

采用陶瓷靶直流磁控溅射,以玻璃为基底制备2.5wt%Nb掺杂TiO2薄膜,控制薄膜厚度在300~350 nm,研究了不同基底温度下所制得薄膜的结构、形貌和光学特性.XRD分析表明,基底温度为150℃、250℃和350℃时,薄膜分别为非晶态、锐钛矿(101)和金红石相(110)结构.基底温度250℃时,锐钛矿相薄膜的晶粒尺寸最大,约为32 nm.薄膜表面形貌的SEM分析显示,薄膜粗糙度和致密度随基底温度升高得到改善.薄膜的平均可见光透过率在基底温度为250℃以内约为70%,随基底温度升高至350℃,平均透过率下降为59%,金红石相的存在不利于可见光透过.Nb掺杂TiO2薄膜的光学带宽在3.68~3.78 eV之间变化.基底温度为250℃时,锐钛矿相薄膜的禁带宽度最大,为3.78 eV.     

Theoretical explanation of Ag/Cu and Cu/Ni nanoscale multilayers softening

Relationship between metallic multilayers hardness and monolayer thickness has been investigated and explained for electroplated Ag/Cu and Cu/Ni multilayers using a modified Thomas-Fermi-Dirac electron theory. Experiments reveal that the peak hardness of Ag/Cu multilayers occurs at the monolayer thickness of about 25 nm, while the peak hardness of Cu/Ni multilayers occurs at about 50 nm. Critical monolayer thickness corresponding to the peak hardness is approximated by the grain size limit of stable dislocations in Ag crystals for the Ag/Cu multilayers and in Cu crystals for Cu/Ni multilayers. Grains size limits are calculated based on a modified Thomas-Fermi-Dirac electron theory. Developed relationship between the critical monolayer thickness and the grains size limit helps understand nanoscale metallic multilayers softening.     

Growth of pseudocubic perovskite-type SrRuO3 thin films on quartz substrate using pulsed laser deposition method

Strontium ruthenium oxide (SrRuO₃) thin films have been grown using pulsed laser deposition technique on silicon, Pt coated silicon and quartz substrates. The effect of substrate temperatures on the structural, microstructure, and electrical properties of the SrRuO₃ films on quartz substrate has been investigated using XRD, SEM, AFM and four-probe method, respectively. The lowest resistivity at room temperature for the SrRuO₃ thin film on quartz substrate has been achieved at substrate temperature of 700 °C. Furthermore, the comparisons of SrRuO₃ thin films deposited on various substrates have been done with respect to structural, microstructural and electrical properties. XRD patterns exhibit that all thin films are a single phase, pseudo-cubic perovskite structure. Study of surface morphology shows that grain size and roughness varies with respect to substrate. It is observed that SrRuO₃ thin films yield larger grain size and root mean square roughness on Pt/Si substrate. Investigation of electrical properties shows that SrRuO₃ thin films can serve the purpose of the bottom electrode in dielectric and ferroelectric devices.     

磁控溅射沉积Cu-W薄膜的特征及热处理的影响

采用磁控共溅射法制备含钨1.51%~14.20%(原子分数,下同)的Cu-W合金薄膜,并用EDX、XRD、SEM、显微硬度仪和电阻仪研究了其成分、结构及性能。结果表明,添加W可显著细化Cu-W薄膜基体相晶粒,晶粒尺寸随W含量的增加而减小,Cu-W薄膜呈纳米晶结构。Cu-W薄膜中存在W在Cu中形成的fcc Cu(W)非平衡亚稳过饱和固溶体,固溶度随W含量的增加而提高,最大值为10.65%。与纯Cu膜对比发现,薄膜的显微硬度和电阻率总体上随W含量的增加而显著增大。经200℃、400℃及650℃热处理1h后,Cu-W薄膜基体相晶粒长大,EDX分析显示晶界处出现富W第二相;薄膜显微硬度降低,电阻率下降,降幅与退火温度呈正相关。添加W引起的晶粒细化效应以及退火中基体相晶粒度增大分别是Cu-W薄膜微观结构和性能形成及演变的主要原因。     

衬底温度对碲化镉薄膜性质及太阳电池性能的影响

蒸汽输运法是制备高质量且大面积均匀的CdTe薄膜的一种优良的方法。采用自主研发的一套蒸汽输运沉积系统制备了CdTe多晶薄膜, 并研究了衬底温度对CdTe薄膜性质及太阳电池性能的影响。利用XRD、SEM、UV-Vis和Hall等测试手段研究了衬底温度对薄膜的结构、光学性质和电学性质的影响。结果表明, 蒸汽输运法制备的CdTe薄膜具有立方相结构, 且沿(111)方向高度择优。随着衬底温度的升高(520℃~640℃), CdTe薄膜的平均晶粒尺寸从2 μm增大到约6 μm, CdTe薄膜的载流子浓度也从1.93×10¹⁰ cm^-3提高到2.36×10¹³ cm^-3, 说明提高衬底温度能够降低CdTe薄膜的缺陷复合, 使薄膜的p型更强。实验进一步研究了衬底温度对CdTe薄膜太阳电池性能的影响, 结果表明适当提高衬底温度, 能够大幅度提高电池的效率、开路电压和填充因子, 但是过高的衬底温度又会降低电池的长波光谱响应, 导致电池转换效率的下降。经过参数优化, 在衬底温度为610℃、无背接触层小面积CdTe薄膜太阳电池的转换效率达到11.2%。     

调制比对电弧离子镀Cr/TiN纳米多层膜力学性能的影响

采用电弧离子镀技术,通过改变调制比沉积Cr/TiN纳米多层膜.利用扫描电子显微镜、原子力显微镜、X射线衍射仪、纳米压痕仪研究了调制比对Cr/TiN纳米多层膜表面形貌、微观结构以及力学性能的影响.结果表明,纳米多层膜表面致密、平滑均匀,膜层与基底结合良好,膜层综合力学性能优异,出现明显的纳米效应和界面效应.当调制比为2:...     

Characterization of thermally stable W/Ni multilayers by X-rays and cross-sectional transmission electron microscopy

W/Ni multilayer structures (MLS) composed of 5 and 10 bilayers, with composition W(15 Å)/Ni(55 Å), have been deposited on float glass substrate using ion-beam sputtering. X-ray reflectivity and wide-angle X-ray diffraction techniques have been used to study their interface characteristics, such as layer thickness, interface roughness and change in structural parameters. The fabricated MLS were found to be oriented along (111) of Ni having superlattice modulation perpendicular to the film plane. Thermal annealing studies on these multilayers showed that these were stable up to 500 °C. Cross-sectional transmission electron microscopy and selected area electron diffraction studies on as-deposited W/Ni MLS of 10 bilayers revealed well formed interfaces without any correlated roughness. The thicknesses of different layers were found to vary along the film thickness.     

The effect of direct current bias on the characteristics of Cu/C:H composite thin films on poly ethylene terephthalate film prepared by electron cyclotron resonance-metal organic chemical vapor deposition

Cu/C:H composite films were prepared on poly ethylene terephthalate (PET) substrate at room temperature by the electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) coupled with a negative direct current (DC) bias system. The negative DC bias voltage applied around the substrate strongly affected the crystallographic structure and composition as well as the surface roughness of the copper films. The surface resistivity of films decrease sharply as the bias voltage increase up to about 5 μΩ-cm below which the resistivity remains almost constant in the range of − 900 to − 1700 V. Thus, the bias voltage appeared to be a critical deposition parameter for preparing copper films with low resistivity. With interfacial studies of Cu-PET, copper atoms are embedded into the polymer substrate during the growth process. Therefore, Cu/C:H composite films on PET with good interfacial properties could be prepared by ECR-MOCVD coupled with a (−)DC bias system.     

Microstructural evolution of Fe/Ti multilayers submitted to in situ thermal annealing

The Fe/Ti multilayers of nominal bilayer thickness of 4.0, 8.0 and 18.0 nm with alternating Fe and Ti sublayers thickness ratio of 1:1 were deposited by direct current magnetron sputtering on Si(100) substrates. The bilayer thickness of as-deposited Fe/Ti multilayers was measured as a modulation wavelength of 4.8, 8.5 and 19.0 nm, respectively, by small angle X-ray diffraction and cross-sectional transmission electron microscopy (XTEM). The three Fe/Ti multilayers were composed of pure metallic -Fe and -Ti according to wide angle X-ray diffraction and selected area diffraction. The Fe/Ti multilayers were in situ submitted to thermal vacuum annealing at the temperatures ranging from 523 K to 723 K for the annealing time of 3 h. With annealing at the lower temperature of 523 K, the intermetallic FeTi appeared in the Fe/Ti multilayers with small modulation wavelength of 4.8 nm. At 623 K, the intermetallic FeTi was formed with modulation wavelength of 8.5 nm. At the higher temperature of 723 K, the intermetallic FeTi was detected with modulation wavelength of 19.0 nm. The modulation wavelength of the Fe/Ti multilayers remained during the thermal annealing. The mixture of intermetallic FeTi and -Fe phase was observed in the extended Fe sublayer of the Fe/Ti multilayers annealed at 723 K by XTEM, correspondingly the remaining Ti sublayer was obtained as a thinned sublayer. Coexistence of the intermetallic FeTi, -Fe and -Ti phases indicated that the dynamic factors have control of the intermixing between the Fe and Ti sublayers in the Fe/Ti multilayers during the thermal annealing.     

Effects of current density and deposition time on electrical resistivity of electroplated Cu layers

This study was performed to investigate the effects of current density and deposition time on sheet resistance and resistivity of electroplated Cu layer. Cu layer covered on sputtered Si/Ta/22Cu-78Ta/Cu films was electroplated with current densities of 1, 1.5 and 2 A/dm², and the deposition times varied from 20 to 100 min. The effects of current density and deposition time on the thickness of Cu layers and the current efficiency were investigated. The variation in sheet resistance and resistivity were discussed with respect to thickness, surface roughness, microstructure, grain size, and texture. In general, it was found that surface roughness might not be the dominate parameter, but the density of nodule boundary in the porous films would affect the electrical property of the electroplating Cu. An increasing extent of the (1 1 1) preferred orientation tends to loosen the nodules and lower the sheet resistance and resistivity of Cu layers. A decrease in the current density and an increase in deposition time tend to produce a Cu layer with (1 1 1) preferred orientation and results in relatively low sheet resistance and resistivity.     

Effects of current density and deposition time on electrical resistivity of electroplated Cu layers

This study was performed to investigate the effects of current density and deposition time on sheet resistance and resistivity of electroplated Cu layer. Cu layer covered on sputtered Si/Ta/22Cu-78Ta/Cu films was electroplated with current densities of 1, 1.5 and 2 A/dm², and the deposition times varied from 20 to 100 min. The effects of current density and deposition time on the thickness of Cu layers and the current efficiency were investigated. The variation in sheet resistance and resistivity were discussed with respect to thickness, surface roughness, microstructure, grain size, and texture. In general, it was found that surface roughness might not be the dominate parameter, but the density of nodule boundary in the porous films would affect the electrical property of the electroplating Cu. An increasing extent of the (1 1 1) preferred orientation tends to loosen the nodules and lower the sheet resistance and resistivity of Cu layers. A decrease in the current density and an increase in deposition time tend to produce a Cu layer with (1 1 1) preferred orientation and results in relatively low sheet resistance and resistivity.     

Reactive DC Magnetron Sputtering Deposition of Copper Nitride Thin Film

Copper nitride thin film was deposited on glass substrates by reactive DC （direct current） magnetron sputtering at a 0.5 Pa N2 partial pressure and different substrate temperatures. The as-prepared film, characterized with X-Ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy measurements, showed a composed structure of Cu3N crystallites with anti-ReO3 structure and a slight oxidation of the resulted film.The crystal structure and growth rate of Cu3N films were affected strongly by substrate temperature. The preferred crystalline orientation of Cu3N films were （111） and （200） at RT, 100℃. These peaks decayed at 200℃ and 300℃ only Cu （111） peak was noticed. Growth of Cu3N films at 100℃ is the optimum substrate temperature for producing high-quality （111） Cu3N films. The deposition rate of Cu3N films estimated to be in range of 18-30 nm/min increased while the resistivity and the microhardness of Cu3N films decreased when the temperature of glass substrate increased.     

Structural and morphological investigations on DC-magnetron-sputtered nickel films deposited on Si (100)

Pure nickel thin films were deposited on Si (100) substrates under different conditions of sputtering using direct current magnetron sputtering from a nickel metal target. The different deposition parameters employed for this study are target power, argon gas pressure, substrate temperature and substrate-bias voltage. The films exhibited high density of void boundaries with reduction in <111> texture deposited under high argon gas pressures. At argon gas pressure of 5 mTorr and target power of 300 W, Ni deposition rate was ~40 nm/min. In addition, coalescence of grains accompanied with increase in the film texture was observed at high DC power. Ni films undergo morphological transition from continuous, dense void boundaries to microstructure free from voids as the substrate-bias voltage was increased from −10 to −90 V. Furthermore, as the substrate temperature was increased, the films revealed strong <111> fiber texture accompanied with near-equiaxed grain structure. Ni films deposited at 770 K showed the layer-by-layer film formation which lead to dense, continuous microstructure with increase in the grain size.     

Influence of substrate temperature on the materials properties of reactive DC magnetron sputtered Ti/TiN multilayered thin films

Ti/TiN multilayers were deposited by DC reactive magnetron sputtering method using a titanium target and an Ar-N₂ mixture discharge gas. XRD technique was employed to study the structure of the coatings and to observe the variations of structural parameters with substrate temperatures. An increase in grain size with increase of substrate temperature was observed. The components of Ti 2p doublet, related to TiN, TiON and TiO₂, were observed in the core-level spectra of the deposited multilayer films from XPS analysis. A microhardness value of 25.5 GPa was observed for Ti/TiN multilayers prepared at 400 °C. Electrical properties were found to depend on substrate temperature.     

Effect of Interfacial Roughness Configuration on the Exchange-Bias Field in NiO Based Spin Valves

Two series of NiO-Co-Cu-Co based spin valves with the same nominal structure were grown by the magneton sputtering technique with different deposition parameters. Texture, surface and interfacial microstructures and the magnetic properties have been investigated in detail. X-ray diffraction, grazing incident X-ray reflectivity and transverse X-ray diffuse scattering were combined to analyze the microstructure of the multilayers. The results show that the texture of the multilayers is not a prerequisite factor for an exchange-bias (EB) field in NiO/Co/Cu/Co spin valves. And the EB effect is also independent of the average roughness at the interfaces. Large correlation lengths and two dimensions of the roughness at the interface are more advantageous for the EB effect.     

Comparative study of copper films prepared by ionized metal plasma sputtering and chemical vapor deposition in the Cu/TaN/SiO2/Si multilayer structure

This work investigated the properties of ionized metal plasma (IMP) deposited copper (Cu) and chemical vapor deposited (CVD) Cu on IMP-TaN (tantalum nitride) diffusion barrier in the Cu(200 nm)/TaN(30 nm)/SiO₂(250 nm)/Si multi-layer structure. The IMP-Cu film deposited on IMP-TaN had a preferred orientation (220) with a grain size of around 30 nm and roughness (RMS) of 1.391 nm, while the CVD-Cu had a (111) preferred orientation with a grain size around 170 nm and roughness (RMS) of 15.416 nm as determined by atomic force microscopy (AFM) and x-ray diffraction (XRD) analyses. Thermal stability study of the structures was also performed by sheet resistance measurements, scanning electron microscopy (SEM), XRD and Rutherford backscattering spectroscopy (RBS). These results revealed that IMP-Cu on IMP-TaN has higher thermal stability, less intermixing and/or agglomeration than CVD-Cu on IMP-TaN at the same annealing temperatures. The higher thermal stability of IMP-Cu than CVD-Cu can be accounted by their difference in microstructure. The failure mechanisms of IMP-Cu and CVD-Cu in multiplayer structure were also discussed.     

Research into the relationship between the surface topography, texture and mechanical properties of PVD-Cu/Ni multilayers

The paper presents the results of structural examinations and mechanical tests of Cu/Ni multilayers fabricated by the magnetron sputtering method. The investigated multilayers were differentiated by Ni sublayer thickness (1, 3 and 6 nm), while the retaining Cu sublayer thickness was unchanged (2 nm). Measurements demonstrated that the multilayers were strongly textured in the direction of their growth [111], with the thinnest multilayer (Cu/Ni = 2/1) showing a stronger texture. Stronger texturing was associated with greater surface roughness. Multilayers with the largest thickness had higher hardness and Young’s modulus. The properties of Cu/Ni multilayers depended both on the thickness of their sublayers, as well as on their total thickness.