The filament in aAu/Ta2 O5 /Au system is analyzed and determined to be a nanoscaled TaO2-x filament. A shrunken anode localizes the filament formation and the defect boundary leads to faster accumulation of oxygen vacancies. The defect changes the switching domination between electron transport and oxygen-vacancy migration. The migration of oxygen vacancies limits the filament dynamics, indicating the crucial role played by oxygen defects.
One dimensional metal oxide nanostructures have attracted much attention owing to their fascinating functional properties. Among them, piezoelectricity and photocatalysts along with their related materials have stirred significant interests and widespread studies in recent years. In this work, we successfully transformed piezoelectric ZnO into photocatalytic TiO2 and formed TiO2/ZnO axial heterostructure nanowires with flat interfaces by solid to solid cationic exchange reactions in high vacuum (approximately 10(-8) Torr) transmission electron microscope (TEM). Kinetic behavior of the single crystalline TiO2 was systematically analyzed. The nanoscale growth rate of TiO2 has been measured using in situ TEM videos. On the basis of the rate, we can control the dimensions of the axial-nanoheterostructure. In addition, the unique Pt/ ZnO / TiO2/ ZnO /Pt heterostructures with complementary resistive switching (CRS) characteristics were designed to solve the important issue of sneak-peak current. The resistive switching behavior was attributed to the migration of oxygen and TiO2 layer served as reservoir, which was confirmed by energy dispersive spectrometry (EDS) analysis. This study not only supplied a distinct method to explore the transformation mechanisms but also exhibited the potential application of ZnO/TiO2 heterostructure in nanoscale crossbar array resistive random-access memory (RRAM).
Gold nanostructures (NSs) have been widely investigated due to their unique properties. Understanding their growth behaviors during synthesis will be beneficial in designing and applying to many functional nanodevices. It is important to enrich the fundamental science and technology of the synthesis and characterization through real time evolution. In this work, we observed the dynamic growth of Au NSs by using liquid in situ transmission electron microscopy (TEM). The solution was sealed in a liquid cell, and the results indicated that the thicker solution layer tended to form multitwinned decahedral NSs; in contrast, nanoplates easily formed in the thinner solution layer. The silver halide model, relying on side-face structures, and the Wulff construction can be used to explain the formation of NSs. Additionally, we analyzed the growth rate of different morphologies to elucidate their growth behaviors. The growth mechanism and formation kinetics of different shapes of Au NSs were systematically studied, which provided direct evidence toward and extended the study of reaction kinetics for modifying the morphology of NSs.
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