Controlling of electrical characteristics of Al/p-Si Schottky diode by tris(8-hydroxyquinolinato) aluminum organic film

We study how tris(8-hydroxyquinolinato) aluminum organic semiconductor layer at p-silicon/Al interface can affect electrical transport across this interface. Al/Alq3/p-Si device shows a good rectifying behavior with an ideality factor value of 1.95. The barrier height values obtained from I–V and Norde method were found to be 0.84 and 0.82 eV, respectively. This indicates that the barrier height obtained from Norde method is lower than that of barrier height value obtained from I–V due to the series resistance effect. The modification of the interfacial potential barrier for Al/p-Si diode was achieved using an interlayer of the Alq3 organic semiconductor and this is ascribed to the fact that the Alq3 interlayer increases the effective barrier height, because of the interface dipole induced by passivation of the organic layer. The frequency dispersion in capacitance and conductance can be interpreted in terms of the series resistance and interface state density values. The series resistance of the diode was changed from 9 kΩ to 1 kΩ with increasing frequency. The distribution profile of R_s–V gives a peak at low frequencies in the depletion region and disappears with increasing frequency.     

Hydrolysis of interfacial bonds in a metal/polymer electrical double layer

Effect of water on the electrical double layer structure at a metal/polymer interface is studied with the use of scanning vibrating capacitor and electrochemical impedance spectroscopy. In the initial stage, the Volta potential of the contact changes well reversibly and rapidly, being proportional to the water vapor pressure, following its diffusion in the polymer (V = A + B log (time)^1/2). Water dipoles at the metal/polymer interface orientate counter the field and compensate it. Drying of the contact restores the initial potential drop. In the first stage of exposure, water somewhat enhances the interfacial interaction, which manifests itself in increasing the potential drop, as well as the charge transfer resistance, and in decreasing the capacitance of the electrical double layer. As time passes, the interface hydrolyzes, its capacitance grows and the time of subsequently restoring the electrical double layer by drying increases. Kinetic dependences of the potential and capacitance, exhibit two segments, we ascribe to easily removable and strongly bonded water molecules solvating the interface, respectively. It is shown that metal-polymer interfacial bonds passivate the metal; however, the passivation can be broken down because of the hydrolysis and the interfacial moisture film formation.Translated from Zashchita Metallov, Vol. 41, No. 2, 2005, pp. 115–126.Original Russian Text Copyright © 2005 by Nazarov, Thierry.     

复合层对Al接触反应钎焊过程及接头性能的影响

研究了Cu ,Zn复合层对Al接触反应钎焊过程和接头质量的影响规律。Cu和Al形成共晶液相破坏了Al表面氧化膜 ,促使Cu Zn包晶液相和Al Zn Cu共晶液相在Al表面润湿。结果表明 ,采用复合层进行Al接触共晶反应钎焊时 ,Cu和Zn厚度比例合适 ,可提高钎焊接头的抗电化学腐蚀性能和接头强度     

Approach to disrupting thick intermetallic compound interfacial layer in friction stir brazing (FSB) of Al/Cu plates

Friction stir brazing (FSB) was developed for dissimilar joining to overcome the problems associated with friction stir lap welding (e.g. pin wear, narrow bonded area, hook defect) by metallurgical reaction instead of plastic flow. To enhance the thermomechanical effect of the rotating shoulder, a pin free tool with a large shoulder of 30 mm diameter was used in FSB of 5 mm thick Al/Cu plates in stepped lap configuration with Zn braze. Compared to the case using common tool of 20 mm diameter, it was found that although the intermetallic compound (IMC) layer grew thickly, it was disrupted into particles, and end crack within thick IMC layer was eliminated. As a result, the joint fractured not along interface and the fracture load increased by as much as 2271 N. This work proposed an approach to disrupting continuous IMC into particles by enhancing the mechanical effect of rotating shoulder.     

基于Al元素界面调控的镁/钛激光熔钎焊接特性

文中选用含Al量元素含量为9%(质量分数)的AZ91焊丝作为填充钎料,采用激光填丝熔钎焊的方法,利用焊丝中Al元素配合激光局部加热的特性改善非互溶不反应镁/钛之间的界面反应. 探索工艺参数对焊接质量的影响规律,分析焊接接头力学性能及组织特征. 结果表明,添加AZ91焊丝能够实现AZ31B镁合金/TC4钛合金的可靠连接,接头最大载荷达到1 520 N,发现焊丝中Al元素能够在激光快速加热冷却过程中偏聚到界面,并与钛侧发生冶金反应生成AlTi₃化合物,界面由较薄的反应层(2 μm以下)组成,达到既实现界面冶金结合,又将反应层厚度控制在不影响接头力学性能的范围之内.     

The influence of bulk traps on the subthreshold characteristics of an organic field effect transistor

The subthreshold characteristics of fabricated organic field effect transistors based on regioregular poly(3-dodecylthiophene) (P3DDT) as the active layer and poly-4-vinylphenol (P4VP) as the gate insulator have been investigated. The transistor turn-on occurs at a threshold voltage of around V_th=0 V. The (hole) mobility of 0.002–0.005 cm²/(V s) has been estimated from the linear region of the transfer characteristics. As usually observed for organic transistors, the inverse subthreshold slope is very high, in our case S≈7 V/dec. Furthermore, the subthreshold current depends on the drain voltage although the transistor is a long channel device. One possibility to explain these peculiarities are interface traps, as demonstrated recently by Scheinert et al. [J. Appl. Phys. 92 (2002) 330]. In this paper, the influence of bulk traps is shown. It turns out that both the high inverse subthreshold slope and the drain voltage dependence can be explained also by recharging of bulk traps. Therefore, other frequency and temperature dependent dynamic measurements have to be applied to distinguish between the different possible influences.     

The characteristics of organic light emitting diodes with Al doped zinc oxide grown by atomic layer deposition as a transparent conductive anode

Al doped zinc oxide (AZO) films, deposited by atomic layer deposition (ALD) were investigated for applying a transparent conductive oxide (TCO) layer as an anode for organic light emitting diode (OLED) devices. AZO films with a thickness of 100 nm were deposited at various Al atomic ratios ranging from 0 to 5% at a deposition temperature (250 °C). The optimum electrical properties: the carrier mobility, the resistivity, and the sheet resistance for the 2% AZO film were found to be 16.2 cm² V^?1 s^?1, 1.5 × 10^?3 cm^?3, and 217 Ω/sq, respectively. The red OLED devices were fabricated using AZO anodes utilizing the various Al atomic ratios; the electrical and optical characteristics were then investigated. The best luminance, quantum efficiency, and current efficiency were found in the OLED device using the 2% AZO TCO; the results were 16599 cd/m², 8.2%, and 7.5 cd/A, respectively.     

Effects of intermetallic compound on the electrical and mechanical properties of friction welded Cu/Al bimetallic joints during annealing

Al/Cu metal joints applied for the electrical connector was joined by the friction welding method to limit the formation of intermetallic compound under optimum friction welding condition. To guarantee the reliability of the Al/Cu joints in service requirement, the effects of the intermetallic compound layer on the electrical and mechanical properties have been investigated under various annealing conditions. Two kinds of intermetallic compounds layer were formed in the joints interface and identified by AlCu and Al₂Cu. The growth kinetic of these intermetallics during the annealing can be followed by volume diffusion process. The activation energy of Al₂Cu, AlCu and total intermetallic compound (AlCu + Al₂Cu) represented 107.5, 98.42 and 110.22 kJ/mol, respectively. A thicker intermetallic compound layers could seriously degrade the electrical resistivity and tensile strength. The electrical resistivity with 21 μm thickness of intermetallic compound was 45 μΩ cm and increased to be 85 μΩ cm with 107 μm of intermetallic compound. Tensile strength remarkably decreased from 85 MPa to near zero at the annealing condition of 773 K and 129.6 ks and fracture occurred through the intermetallic compound layers.     

电场对AZ31B与Al连接界面扩散反应和扩散溶解层结构的影响

应用电场激活扩散连接技术(FADB)实现AZ31B与Al的连接。研究了电场对AZ31B/Al结合界面扩散反应和扩散溶解层结构的影响。采用光学显微镜、扫描电子显微镜、X射线能谱与X射线衍射仪等方法分析了扩散溶解层的显微组织、相组成和元素分布。结果表明,在FADB条件下以铝粉为中间层时扩散溶解层由均匀共晶层、过渡层和胞状晶组成;以铝箔为中间层时由镁合金侧共晶层和铝侧过渡层构成。电场强度对扩散溶解层宽度和形态均有显著影响。溶解层随电流密度升高而变宽。以铝粉为中间层在温度450℃,时间50min,电流密度80A·cm-2时过渡层宽度为120μm,为未施加电场时的12倍。电流对共晶层内晶粒尺寸有显著影响。当电流密度由28A·cm-2升至48A·cm-2时,点状晶粒晶粒尺寸由2μm降至0.5μm。     

Al2O3钝化层对a-IGZO薄膜晶体管电性能的增强机制研究

采用空心阴极增强脉冲激光沉积技术(HC-PLD)在室温制备高质量的Al₂O₃薄膜，作为非晶铟镓锌氧(a-IGZO)TFT器件的钝化层，显著增强了Al₂O₃/a-IGZO TFT器件的亚阈值特性，其原因在于空心阴极引入的氧等离子体抑制了Al₂O₃/a-IGZO界面处氧空位的形成。进一步研究发现，针对a-IGZO薄膜的180℃退火处理有利于消除弱结合氧并抑制深能级缺陷，提高载流子迁移率并降低阈值电压漂移；而针对Al₂O₃/a-IGZO TFT器件进行100℃退火处理有助于消除其界面附近的氧空位，降低载流子浓度，改善亚阈值特性。结合2步退火工艺所制备的Al₂O₃/a-IGZO TFT器件迁移率高达22.8 cm²·V^-1·s^-1，亚阈值摆幅为0.6 V·decade^-1，综合电性能优异。     

Self-assembled monolayer effect on the characteristics of organic diodes

In this paper, we study the effect of self-assembled monolayers (SAMs) on the electric behavior of organic diodes based on sexithiophene (6T) sandwiched between indium tin oxide (ITO) and aluminum. We have used molecules of SAMs based on a thiol with functional groups of oligothiophene (3T(CH₂)₆SH). Wettability measurements have been performed to characterize ITO surface energy and its modification upon deposition of SAMs. The results of contact angle measurements and surface energies demonstrate the homogeneity and rigidity of grafting surface. The current vs. applied voltage characteristics of devices show that conduction in weak biasing follow Richardson–Schottky behavior. Beyond 1.5 V, J–V characteristics can be successfully modeled by space-charge limited current (SCLC) theory followed by a trap charge limited current (TCLC). The electrical as well as optical characteristics of 6T layer are clearly affected by the presence of the SAM. The differences between ITO/SAM and bare ITO samples are interpreted in terms of structural effect induced by the self-assembled monolayer of 3T(CH₂)₆SH.     

热压工艺对SiCf/Ti复合材料界面反应层生长影响的数值模拟

提出一个热-力-扩散-反应强耦合相场模型来研究热压烧结制备工艺对连续碳化硅纤维增强钛基复合材料中金属间化合物生长规律的影响。模拟结果表明,在两种不同温度下各个界面反应层(Ti₃SiC₂/Ti₅Si₃C_x/Ti₅Si₃C_x+TiC/TiC)的厚度生长与试验值吻合较好。增大外加压力能促进界面层厚度的生长,但对其中抗拉强度最低的Ti₅Si₃层的生长起显著的抑制作用,同时使各界面反应层由周向拉应力状态逐渐转变为压应力。温度的升高使断裂韧度最大的Ti₃SiC₂层厚度增大,但也使总界面层和Ti₅Si₃层的厚度增加。因此,在制备工艺上适当增加压力并选择合适的温度,得到厚度适宜的界面反应层的同时,尽可能使Ti₅Si₃层变薄和Ti₃Si...     

Effect of various processing methods on the interfacial reactions in SiCp/2024 Al composites

SiC_p/2024 Al composites were prepared using various processing techniques, such as spray forming, powder metallurgical hot pressing, thixoforming, and compocasting. The interfacial characterizations of these composites were performed using scanning electron microscopy, Auger electron spectrometry, transmission electron microscopy, and X-ray diffraction on reaction products extracted using the electrochemical dissolution. The value of these combined techniques in elucidating the morphologies of the interfacial reaction products was also demonstrated. The influence that each fabrication process has on the extent of the interfacial reaction was studied. Adequate process parameters to fabricate SiC_p/Al alloy composites were proposed based on thermodynamic considerations.     

The effect of pulsed electrical currents on the formation of macrosegregation in solidifying Al–Si hypoeutectic phases

Within this study, we conducted experimental investigations focusing on the formation of macrosegregation in Al-7wt-%Si alloys exposed to electric current pulses (ECP) during solidification. The distribution of eutectic phase was measured on various sections of the solidified samples. The results do not show the formation of reproducible segregation pattern. This finding can be attributed to the specific pattern and the turbulent character of the flow generated by the ECP treatment, the equiaxed growth of free-moving crystals and a non-symmetric distribution of the electromagnetic force due to an uneven wetting of the electrodes. An increasing input of energy by ECP intensifies the melt flow and increases the variations of phase distribution over a longitudinal section.     

液压马达滑靴副接触方式对静压支承性能的影响

本文将滑靴副按半径误差分为三种接触方式,讨论了各接触方式对静压支承性能的影响。指出现有的计算模型由于忽略了尺寸误差是不完整的,在误差较大时尤其如此。     

The effect of an artificially synthesized simonkolleite layer on the corrosion of electrogalvanized steel

Electrochemical behavior of low alloy steel covered by a synthetic layer of simonkolleite was studied alone and in galvanic couple with zinc. Simonkolleite on steel inhibits cathodic oxygen reduction in 5 wt.% NaCl at pH = 7 and 9 but it is unstable at pH = 11. In NaCl solution the galvanic current density between Zn and steel is reduced by more than twice if the synthetic simonkolleite layer is deposited on steel. The polarity between Zn and steel is inverted after several hours in NaHCO₃ solutions. X-ray diffraction confirmed the instability of simonkolleite in this conditions and its transformation into carbonate containing salts.     

Cu含量对Ag/LSCO电接触材料物理性能的影响

采用溶胶凝胶法辅以高能球磨工艺合成Cu粉体改性La_0.5Sr_0.5CoO_3-δ(LSCO)粉体,用粉末冶金工艺结合热挤压技术制备了系列Cu改性Ag/LSCO电接触材料与成品丝,研究了Cu粉体对改性Ag/LSCO材料界面润湿性、物理力学性能等影响规律。结果表明,随着Cu含量的增加,改性Ag/LSCO-x Cu (x=0、1、2、4、6、8)电接触材料的电阻率呈先增加后减小的趋势,与Ag和LSCO基底的润湿角变化趋势相一致,但其密度和硬度性能变化趋势相反;当Cu含量为4%时,Ag和LSCO-4Cu基底的润湿角达最小值55.0°,相应的成品丝(φ2.35 mm)性能最佳：电阻率2.29μ?·cm,硬度(HV_0.3)946.7 MPa,密度9.73 g/cm³,断后延伸率3.9%,为纯Ag/LSCO的3.9倍。     

A study on the structure and electrochemical characteristics of a Ni/Al double hydroxide

Aluminium-substituted nickel based layered double hydroxides (LDHs), Ni_0.78Zn_0.04Co_0.04Co_0.02Al_0.16(OH)₂(CO₃)_0.08· 1.0H₂O, were synthesized by a chemical co-precipitating process. It was shown that the structure of the LDHs is similar with that of α-Ni(OH)₂ investigated by X-ray diffraction and transmission electron microscopy. The electrode comprising the LDHs was charged/discharged according to a galvanostatic model, and displayed better discharge capacity than the common β-Ni(OH)₂ electrode. In addition, the effects of losing structure water on structure and electrochemical performance were investigated. This article is based on a presentation in “The 7th Korea-China Workshop on Advanced Materials” organized by the Korea-China Advanced Materials Cooperation Center and the China-Korea Advanced Materials Cooperation Center, held at Ramada Plaza Jeju Hotel, Jeju Island, Korea on August 24≈27, 2003.