Real-time Degradation Study of HgBa₂CaCu₂O_6+δ?Thin Film Using Near-field Scanning Microwave and Optical Dual Probe

Abstract

All high- T_c superconductors are susceptible to humid environment. The mechanism behind this degradation process is not yet well known or even described. In an attempt to understand the mechanism, we studied the real-time degradation process of HgBa₂CaCu₂O_6+δ (Hg-1212) thin film using scanning probe microscopy (SPM) techniques. A newly developed near-field scanning microwave and optical dual probe was employed to map simultaneously the spatial variation of microwave sheet resistance and optical transmittance of a sample. Mapping was performed at a regular time interval while the sample was exposed to a very high level of humidity (85%-90%). In a separate experiment, atomic force microscope (AFM) was used to monitor the surface roughness of a sample subjected to the same level of humidity. Results indicate that the degradation process of Hg-1212 involves the gradual transformation of the material into a colorless insulator accompanied by continuous surface deformations.