Broadband Microwave Signal Dissipation in Nanostructured Copper Oxide at Air-Film Interface

Contactless broadband microwave spectroscopy (a.k.a., broadband dielectric spectroscopy (BDS)) enables the accurate operando analysis of the electrical and magnetic properties without compromising the kinetic conditions of the experiment. The BDS method is sensitive to the actual electronic structure of species, and it is most relevant to redox reactions involving charge-transfer. In this paper, using BDS, we have studied and characterized the oxidation of a copper layer in a purposely built prototypical 3-D integrated circuit (3D-IC) during cycled high-temperature storage. We show that the microwave signal loss in these devices is attributable to the energy dissipation through the signal's interactions with the copper oxidation product. The results demonstrate that contactless BDS could be leveraged into an excellent metrology for applications that use metal oxide as sensing elements.

Enhanced photocatalytic performances of n-TiO₂ nanotubes by uniform creation of p-n heterojunctions with p-Bi₂O₃ quantum dots

An ultrasonication-assisted successive ionic layer adsorption and reaction (SILAR) strategy was developed for uniform deposition of high density p-type Bi2O3 quantum dots on n-type TiO2 nanotube arrays (Bi2O3@TiO2 NTAs), which were constructed by electrochemical anodization in ethylene glycol containing the electrolyte. Compared with pristine TiO2 NTAs, the Bi2O3 quantum dots sensitized TiO2 NTAs exhibited highly efficient photocatalytic degradation of methyl orange (MO). The kinetic constant of Bi2O3@TiO2 NTAs prepared by an ultrasonication-assisted SILAR process of 4 cycles was 1.95 times higher than that of the pristine TiO2 NTA counterpart. The highly efficient photocatalytic activity is attributed to the synergistic effect between the formation of a uniform p-n heterojunction with high-density for enhancing light absorption and facilitating photogenerated electron-hole separation/transfer. The results suggest that Bi2O3@TiO2 p-n heterojunction nanotube arrays are very promising for enhancing the photocatalytic activity and open up a promising strategy for designing and constructing high efficiency heterogeneous semiconductor photocatalysts.