Etching process

The solvents used for the selective etching process were Dimethylsulfoxide (DMSO) and Dimethylformamide (DMF), the amines used were Triethylamine (TEA) and Propylamine (PA) in specified concentrations. Etching baths were prepared daily. Samples were etched in the dark or under red light at room temperature (20$\pm1^\circ$C). After removal from the etching bath, the samples were immediately placed in a 1:1 methanol/acetone bath to stop the process. After a few seconds, the samples were moved again, and immersed in pure acetone. Finally, the samples were dried by a stream of compressed dry and clean air, labelled carefully and stored in protective boxes.