C-AFM and KPFM approach to investigate the electrical properties of single grain boundaries in ZnO varistor devices

AbstractThe effect of MnO on the electrical properties of Nb-doped SrTiO3 was investigated to understand the electronic states of grains and grain boundaries. Grain size and dielectric constant were decreased with increasing Mn-doped content from 0 to 0.07 mol%. However, it was observed that the non-linearity coefficient of Nb-doped SrTiO3 was changed from 5 to 43 with Mn-doped content increasing from 0 to 0.03 mol%. Current-voltage (I-V) characteristics, capacitance-voltage (C-V) measurement, complex plane analysis and impedance spectroscopy were performed to obtain the information about the electrical properties of grains and grain boundaries. The potential barrier height increased and the donor concentration decreased with increasing Mn-doped content. This phenomena, that the electrical properties of Nb-doped SrTiO3 were changed with the addition of Mn, would be determined by the effect which Mn-2-3 substituted for Ti sites. It was observed that the breakdown voltage of single grain boundary was changed from 3.8 V to 8.9 V when measured by micro-electrode method.

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Statistics on the AC ageing characteristics of single grain boundaries of ZnO varistor

Materials Chemistry and Physics ◽

10.1016/j.matchemphys.2010.09.023 ◽

2011 ◽

Vol 125 (1-2) ◽

pp. 9-11 ◽

Cited By ~ 11

Author(s):

Jun Liu ◽

Jinliang He ◽

Jun Hu ◽

Wangcheng Long ◽

Fengchao Luo

Keyword(s):

Grain Boundaries ◽

Zno Varistor ◽

Single Grain

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Origin of Leakage Currents in ZnO Based Varistor Ceramics with Al(NO3)3 Dopant

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.434-435.386 ◽

2010 ◽

Vol 434-435 ◽

pp. 386-388 ◽

Cited By ~ 1

Author(s):

Jun Hu ◽

Wang Chen Long ◽

Jin Liang He ◽

Jun Liu ◽

Feng Chao Luo

Keyword(s):

Experimental Data ◽

Numerical Simulation ◽

Electrical Properties ◽

Grain Boundaries ◽

The Other ◽

Leakage Currents ◽

Donor Density ◽

Zno Varistor ◽

Zno Varistors ◽

Simulation Results

The additive of Al(NO3)3 has been doped into ZnO varistors in order to reduce their residual voltages. However, the leakage currents of samples always increase at the same time. Generally, it is recognized that some of doped Al3+ ions enter the ZnO grains and reduce their resistivity, which results in lower residual voltages of varistor samples. On the other hand, the remnant Al3+ ions appear in the grain boundaries and also reduce their resistivity, which results in larger leakage currents. In this paper, the electrical properties of ZnO varistor samples with various amounts of Al(NO3)3 dopant were measured. The experimental data are compared with the numerical simulation results, which reveals that the increased leakage currents of ZnO varistors with Al(NO3)3 dopant are not only due to the decreased resistivity of grain boundaries, but also the increased donor density of ZnO grains.

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Microchemistry of ZnO Varistors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133102 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1694-1695

Author(s):

K. K. Soni ◽

J. Hwang ◽

V. P. Dravid ◽

T. O. Mason ◽

R. Levi-Setti

Keyword(s):

Grain Boundaries ◽

Multiple Roles ◽

Grain Boundary Engineering ◽

Ion Microprobe ◽

Dopant Distribution ◽

Important Ingredient ◽

Zno Varistor ◽

Zno Varistors ◽

Zno Powder ◽

The University

ZnO varistors are made by mixing semiconducting ZnO powder with powders of other metal oxides e.g. Bi2O3, Sb2O3, CoO, MnO2, NiO, Cr2O3, SiO2 etc., followed by conventional pressing and sintering. The non-linear I-V characteristics of ZnO varistors result from the unique properties that the grain boundaries acquire as a result of dopant distribution. Each dopant plays important and sometimes multiple roles in improving the properties. However, the chemical nature of interfaces in this material is formidable mainly because often trace amounts of dopants are involved. A knowledge of the interface microchemistry is an essential component in the ‘grain boundary engineering’ of materials. The most important ingredient in this varistor is Bi2O3 which envelopes the ZnO grains and imparts high resistance to the grain boundaries. The solubility of Bi in ZnO is very small but has not been experimentally determined as a function of temperature.In this study, the dopant distribution in a commercial ZnO varistor was characterized by a scanning ion microprobe (SIM) developed at The University of Chicago (UC) which offers adequate sensitivity and spatial resolution.

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Effects of Charge Compensation on Colossal Permittivity and Electrical Properties of Grain Boundary of CaCu3Ti4O12 Ceramics Substituted by Al3+ and Ta5+/Nb5+

Molecules ◽

10.3390/molecules26113294 ◽

2021 ◽

Vol 26 (11) ◽

pp. 3294

Author(s):

Jakkree Boonlakhorn ◽

Jedsada Manyam ◽

Pornjuk Srepusharawoot ◽

Sriprajak Krongsuk ◽

Prasit Thongbai

Keyword(s):

Dielectric Properties ◽

Electrical Properties ◽

Grain Boundary ◽

Grain Boundaries ◽

Barrier Height ◽

Potential Barrier ◽

Charge Compensation ◽

Solid State Reaction Method ◽

Wide Frequency Range ◽

Potential Barrier Height

The effects of charge compensation on dielectric and electrical properties of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics (x = 0−0.05) prepared by a solid-state reaction method were studied based on the configuration of defect dipoles. A single phase of CaCu3Ti4O12 was observed in all ceramics with a slight change in lattice parameters. The mean grain size of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics was slightly smaller than that of the undoped ceramic. The dielectric loss tangent can be reduced by a factor of 13 (tanδ ~0.017), while the dielectric permittivity was higher than 104 over a wide frequency range. Impedance spectroscopy showed that the significant decrease in tanδ was attributed to the highly increased resistance of the grain boundary by two orders of magnitude. The DFT calculation showed that the preferential sites of Al and Nb/Ta were closed together in the Ti sites, forming self-charge compensation, and resulting in the enhanced potential barrier height at the grain boundary. Therefore, the improved dielectric properties of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics associated with the enhanced electrical properties of grain boundaries. In addition, the non-Ohmic properties were also improved. Characterization of the grain boundaries under a DC bias showed the reduction of potential barrier height at the grain boundary. The overall results indicated that the origin of the colossal dielectric properties was caused by the internal barrier layer capacitor structure, in which the Schottky barriers at the grain boundaries were formed.

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Grain Boundary Atomic Structures in SrTiO3 and BaTiO3

Materials Science Forum ◽

10.4028/www.scientific.net/msf.558-559.851 ◽

2007 ◽

Vol 558-559 ◽

pp. 851-856 ◽

Cited By ~ 1

Author(s):

Takahisa Yamamoto ◽

Teruyasu Mizoguchi ◽

S.Y. Choi ◽

Yukio Sato ◽

Naoya Shibata ◽

...

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Annealing Temperature ◽

Unit Length ◽

Rate Dependency ◽

Atomic Structures ◽

Current Voltage ◽

Single Grain ◽

Current Voltage Characteristics ◽

Theoretical Results

SrTiO3 bicrystals with various types of grain boundaries were prepared by joining two single crystals at high temperature. By using the bicrystals, we examined their current-voltage characteristics across single grain boundaries from a viewpoint of point defect segregation in the vicinity of the grain boundaries. Current-voltage property in SrTiO3 bicrystals was confirmed to show a cooling rate dependency from annealing temperature, indicating that cation vacancies accumulate due to grain boundary oxidation. The theoretical results obtained by ab-initio calculation clearly showed that the formation energy of Sr vacancies is the lowest comparing with Ti and O vacancies in oxidized atomosphere. The formation of a double Schottky barrier (DSB) in n-type SrTiO3 is considered to be closely related to the accumulation of the charged Sr vacancies. Meanwhile, by using three types of low angle boundaries, the excess charges related to one grain boundary dislocation par unit length was estimated. In this study, we summarized our results obtained in our group.

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Effect of Crystallographic Quality of Grain Boundaries on Both Mechanical and Electrical Properties of Electroplated Copper Thin Film Interconnections

Journal of Electronic Packaging ◽

10.1115/1.4029931 ◽

2015 ◽

Vol 137 (3) ◽

Cited By ~ 7

Author(s):

Naokazu Murata ◽

Naoki Saito ◽

Kinji Tamakawa ◽

Ken Suzuki ◽

Hideo Miura

Keyword(s):

Electrical Properties ◽

Grain Boundaries ◽

Fatigue Fracture ◽

High Crystallinity ◽

Mechanical And Electrical Properties ◽

Copper Interconnection ◽

Electroplated Copper ◽

Two Parameters ◽

Low Crystallinity

Effects of crystallographic quality of grain boundaries on mechanical and electrical properties were investigated experimentally. A novel method using two parameters of image quality (IQ) and confidence index (CI) values based on electron back-scattering diffraction (EBSD) analysis was proposed in order to evaluate crystallographic quality of grain boundaries. IQ value was defined as an index to evaluate crystallinity in region irradiated with electron beam. CI value determined existence of grain boundaries in the region. It was found that brittle intergranular fatigue fracture occurred in the film without annealing and the film annealed at 200 °C because network of grain boundaries with low crystallinity remained in these films. On the other hand, the film annealed at 400 °C caused only ductile transgranular fatigue fracture because grain boundaries with low crystallinity almost disappeared. From results of measurement of electrical properties, electrical resistivity of copper interconnection annealed at 400 °C with high crystallinity (2.09 × 10−8 Ωm) was low and electron migration (EM) resistance was high compared with an copper interconnection without annealing with low crystallinity (3.33 × 10−8 Ωm). It was clarified that the interconnection with high crystallinity had superior electrical properties. Thus, it was clarified that the crystallographic quality of grain boundaries has a strong correlation of mechanical and electrical reliability.

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Structural and Electrical Studies on ZnO-Based Thin Films by Laser Irradiation

Journal of Nanotechnology ◽

10.1155/2016/9385725 ◽

2016 ◽

Vol 2016 ◽

pp. 1-6 ◽

Cited By ~ 2

Author(s):

Shanyue Zhao ◽

Yinqun Hua ◽

Ruifang Chen ◽

Jian Zhang ◽

Ping Ji

Keyword(s):

Thin Films ◽

Grain Size ◽

Electrical Properties ◽

Grain Boundaries ◽

Laser Irradiation ◽

Nonlinear Coefficient ◽

Acceptor State ◽

Xrd Pattern ◽

Electrical Studies ◽

Structural And Electrical Properties

The effects of laser irradiation on the structural and electrical properties of ZnO-based thin films were investigated. The XRD pattern shows that the thin films were highly textured along thec-axis and perpendicular to the surface of the substrate. Raman spectra reveal that Bi2O3segregates mainly at ZnO-ZnO grain boundaries. After laser irradiation processing, the grain size of the film was reduced significantly, and the intrinsic atomic defects of grain boundaries and Bi element segregated at the grain boundary were interacted frequently and formed the composite defects of acceptor state. The nonlinear coefficient increased to 24.31 and the breakdown voltage reduced to 5.34 V.

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