No abstract

We report a simple one‐pot method for the rapid preparation of sub‐10 nm pure hexagonal (β‐phase) NaYF4‐based upconverting nanoparticles (UCNPs). Using Therminol® 66 as a co‐solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase‐purity of the as‐synthesized core and core–shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X‐ray diffraction, and small‐angle X‐ray scattering studies. In‐depth photophysical evaluation of the UCNPs was pursued by using steady‐state and time‐resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface‐related luminescence quenching effects.

In this paper, we report a hierarchical simulation study of the electromigration problem in Cu-CNT composite interconnects. Our work is based on the investigation of the activation energy and self-heating temperature using a multiscale electro-thermal simulation framework. We first investigate the electrical and thermal properties of Cu-CNT composites, including contact resistances, using the Density Functional Theory and Reactive Force Field approaches, respectively. The corresponding results are employed in macroscopic electro-thermal simulations taking into account the self-heating phenomenon. Our simulations show that although Cu atoms have similar activation energies in both bulk Cu and Cu-CNT composites, Cu-CNT composite interconnects are more resistant to electromigration thanks to the large Lorenz number of the CNTs. Moreover, we found that a large and homogenous conductivity along the transport direction in interconnects is one of the most important design rules to minimize the electromigration.

The proceeding scaling in microelectronic devices requires smaller and smaller copper wires for energy transfer in integrated devices. Voids in the copper wires lead to a resistance increase and damage of the wiring. Copper wires are fabricated by electrochemical deposition as it enables a bottom-up, void free copper growth, so-called superfilling. The present work focuses on the mechanism of the electrochemical deposition with the goal of understanding and describing the superfilling. Electrochemical measurements and partial fill experiments under production-like conditions are carried out to study the effects of bath additives. The co-adsorption theory is adopted to explain additive interaction which is presumed to be the key for superfilling. It is shown that superfilling is a result of the synergetic adsorption behavior of at least two organic additives and a kinetic balancing between additive accumulation and copper deposition rate.

No abstract