Thermodynamically driven Al migration across ultrathin Ag layered electrodes without thermal loading
Guoqing Zhao, Eunwook Jeong, Sang‐Geul Lee, Jeong-Seong Bae, Seung Min Yu, Seung Zeon Han, Gun-Hwan Lee, Eun‐Ae Choi, Jungheum Yun
Abstract
The use of metallic dopants and seeds as wetting inducers for synthesizing ultrathin Ag layers on chemically heterogeneous oxides has been criticized for inducing nonnegligible degradation in the optoelectrical properties of Ag. This report presents a series of experimental and numerical investigations that reveal a substantial migration of atomic Al across ultrathin (<10 nm) Ag layered electrodes at room temperature, which provides a reliable means of minimizing optoelectrical degradation. Experimental evidence revealed the substantial segregation of atomic Al along the topmost surfaces of Ag geometries, followed by the migration of the majority of the Al atoms beyond the Ag domains into the upper SiOx and Au layers in the SiOx/Ag/SiOx and SiOx/Ag/Au configurations, respectively. The Al atoms incorporated into the SiOx layer were completely oxidized. Numerical calculations indicated that the Al migration across the Ag geometries was driven toward simultaneous decreases in the formation energy and surface free energy of Ag. The findings elucidate the Al migration across Ag domains at room temperature and refute the existing convictions that only support the oxidation-driven and thermal loading-driven migration mechanisms.