Scaling Organic Electrochemical Transistors Down to Nanosized Channels

The perspective of downscaling organic electrochemical transistors (OECTs) in the nanorange is approached by depositing poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on electrodes with a nanogap designed and fabricated by electromigration induced break junction (EIBJ) technique. The electrical response of the fabricated devices is obtained by acquiring transfer characteristics in order to clarify the specific main characteristics of OECTs with sub‐micrometer‐sized active channels (nanogap‐OECTs). On the basis of their electrical response to different scan times, the nanogap‐OECT shows a maximum transconductance unaffected upon changing scan times in the time window from 1 s to 100 µs, meaning that fast varying signals can be easily acquired with unchanged amplifying performance. Hence, the scaling down of the channel size to the nanometer scale leads to a geometrical paradigm that minimizes effects on device response due to the cationic diffusion into the polymeric channel. A comprehensive study of these features is carried out by an electrochemical impedance spectroscopy (EIS) study, complemented by a quantitative analysis made by equivalent circuits. The propagation of a redox front into the polymer bulk due to ionic diffusion also known as the “intercalation pseudocapacitance” is identified as a limiting factor for the transduction dynamics.     

电迁移技术在获取核素迁移参数中的应用

电迁移技术可快速、高效获取核素迁移参数,在核素迁移研究领域具有广阔应用前景。传统电迁移方法利用电场驱动核素离子快速定向运移,通过土体精确切割、浓度定量测定及理论模型拟合可快速获取核素在土体中的扩散迁移参数,目前该技术在单一种态核素的迁移研究中已得到成功应用,但仍无法满足强吸附性核素的迁移实验研究需要。为此,本文对传统电迁移技术进行改进,设计了cm级流出法电迁移实验装置,并建立了相应的迁移模型与参数求解方法,开展了以⁸⁸Sr为示踪剂、柯尔碱膨润土为介质载体的电迁移实验,验证了流出法在电迁移研究中的可行性,为后续钚等多种态、强吸附性核素的电迁移实验研究奠定了理论基础。     

Regeneration of hexavalent chromium using a Bi-doped PbO2 anode

The rate of hexavalent chromium regeneration from trivalent chromium, present as an impurity in a chromium plating solution at the Bi-doped PbO₂ anode, is found to be approximately four times greater than the corresponding rate observed for a PbO₂ coated lead (anodized lead) anode. A mathematical model that takes into account species electromigration and associated mass transfer effects was developed and tested. Dynamic concentration data for various chromium species were used along with the mathematical model to evaluate the various rate parameters.     

Combined low-frequency noise and resistance measurements for void extraction in deep-submicrometer interconnects

Electromigration stress can give rise to voids that increase the resistance and localized thermal stress in interconnects. Estimation of the extent of voiding can provide information on the material quality and the amount of degradation that has resulted from the electrical stress. In this paper, a model is proposed that can be used to estimate the effective void volume in deep-submicrometer interconnects. The model uses a combination of low-frequency noise and resistance measurements, and also considers the thermal coefficient of resistance in calculating the change in resistance of the interconnect line. A deconvolution scheme was employed to extract the 1/f noise component from the noise-measurements to improve the accuracy of the extraction algorithm. To verify the accuracy of the model, the focused ion beam (FIB) technique was used to mill holes (to simulate voids) of known dimensions. The model was further applied to an electromigration stress study of aluminum (Al) interconnects as a method of testing its validity for stress-induced voids. The proposed technique is a useful reliability tool for void detection in deep-submicrometer interconnects.     

VLSI金属互连电迁移1/fγ噪声特性研究

通过对超大规模集成电路金属互连进行电迁移加速寿命实验和不同电迁移损伤程度的金属薄膜电阻及1/f^γ噪声的测量和分析,得到了1/f^γ噪声3Hz点功率谱密度和频率指数γ均随电迁移损伤程度加剧而变大的实验规律.分析表明,在同样的电迁移损伤程度条件下,1/f^γ噪声点功率谱密度的相对变化量是电阻相对变化量的大约2000倍.此外,得到了1/f^γ噪声频率指数随电迁移过程逐渐变大的实验规律.因此,1/f^γ噪声功率谱密度和频率指数有可能作为比现在应用的电阻相对变化量更为灵敏的金属互连电迁移表征参量.     

元素掺杂对Bi电迁移影响的第一原理计算

应用第一原理方法研究通过元素掺杂来抑制SnBi无铅焊料中Bi的电迁移问题.在SnBi体系中掺杂zn和Sb元素,通过用近弹性带方法计算掺杂体系中Bi元素的扩散能垒.结果表明:加入Sb之后,Bi的扩散能垒由原来的0.32 eV升高到0.46 eV,扩散激活能由原来的1.14 eV升高到1.18 eV;加入Zn后,Bi的扩散能垒由原来的0.32 eV升高到0.48 eV,扩散激活能由原来的1.14 eV升高到1.22 eV.由此可得,Zn和Sb的加入都能够提高Bi的扩散激活能,起到抑制扩散的作用.通过分析态密度可知:加入Zn和Sb后,体系中Sb与Bi的p态曲线几乎完全重合,比Sn与Bi的p态曲线重合度高很多,说明sb和Bi的共价键作用很强,且比Sn-Bi的共价键作用强,从而增加Bi的扩散能垒.同样,Zn和Bi的p态曲线重合度也比Sn和Bi的曲线重合度高很多,表明Zn-Bi的共价键同样比sn-Bi的共价键强,所以Zn的加入同样增加Bi的扩散能垒.总结说来,Sb和zn的掺杂能够抑制SnBi焊料中Bi的电迁移.     

SnAgCu焊点电迁移诱发IMC阴极异常堆积

为了研究电迁移过程中焊点与焊盘界面金属问化合物(IMC)的变化,在28℃下,对无铅Sn3.0Ag0.5Cu焊点进行了6.5A直流电下的电迁移实验.结果发现,通电144h后,阳极侧IMC层变厚,平均达到10.12 μm;阴极侧IMC层大部分区域变薄至0.86μm,局部出现Cu焊盘的溶解消失,但在界面边缘处出现Cu3Sn5...     

Structured graphene devices for mass transport

The reversible atomic-mass transport along graphene devices has been achieved. The motion of Al and Au in the form of atoms or clusters is driven by applying an electric field between the metal electrodes that contact the graphene sheet. It is shown that Al moves in the direction of the applied electric field whereas Au tends to diffuse in all directions. The control of the motion of Al is further demonstrated by achieving a 90° turn, using a graphene device patterned in a crossroads configuration. The controlled motion of Al is attributed to the charge transfer from Al onto the graphene so that the Al is effectively charged and can be accelerated by the applied electric field. To get further insight into the actuation mechanism, theoretical simulations of individual Al and Au impurities on a perfect graphene sheet were performed. The direct (electrostatic) force was found to be ～1 pN and dominant over the wind force. These findings hold promise for practical use in future mass transport in complex circuits.     

电流密度对Sn3.0Ag0.5Cu焊点蠕变行为的影响

通过观察焊点的电阻变化和显微组织演变,研究了电流密度对Sn3.0Ag0.5Cu焊点蠕变行为的影响。结果表明:焊点在低电流密度条件下蠕变时,其电阻波动大、寿命长,失效机制由蠕变过程主导,损伤逐渐累积导致最终失效;焊点在高电流密度条件下蠕变时,其电阻波动小、寿命短,电迁移作用缓解了焊点的初期蠕变损伤,但是加速了焊点后期脆性断裂失效。     

基于电迁移法的铝微米带弯曲生长现象研究

基于电迁移法制备了弯曲形状的铝微米带,可作为连接件直接应用于微机电系统和光电器件中。试验所需试样是一层沉积在TiN层的铝膜,并在铝膜的阳极端制作原子排出孔。试验结果表明,铝微米带的生长驱动力来自于铝原子积聚产生的压应力,排出孔的位置靠近铝膜边缘,使铝原子在排出孔两侧的析出速率出现差异,导致铝微米带出现自发弯曲生长现象。