Excimer laser micromachining of indium tin oxide for fabrication of optically transparent metamaterial absorbers

Abstract

Excimer laser micromachining has been extensively studied to machine Indium Tin oxide which is uniformly deposited over PET to realize transparent broadband metamaterial absorbers. Various micromachining parameters such as fluence and spot overlap are considered and optimized to ablate the ITO film with controlled damage to the PET substrate for obtaining desired roughness to achieve uniform optical transmittance. A correlation has been developed between the generated roughness and optical transmittance of the machined area, so that any desired value of the optical transmittance can be achieved. Parameters for machining were selected in such a way that optical transmittance between machined and non-machined area are closely matched. Two different structures are demonstrated over a large area of about 243 mm2. To reduce the machining time of such a large area, an algorithm has been developed to determine the size of the masks for machining complex structures of any shape. Further, a thermal model is presented for better understanding of the ablation phenomenon. We conclude that the machining of ITO on PET substrates occurs via delamination of the ITO from the PET surface rather than a melt vaporization of the ITO.