Novel Anthracene Materials for Applications in Lithography and Reversible Photoswitching by Light and Air

Abstract

Herein we demonstrate how the photoreaction between anthracenes and singlet oxygen ((1)O(2)) is employed for applications either as photoswitch or as photoresist. Thin films of the diaryl-alkyl anthracene 1 and the analogous oligomeric species 2 were irradiated under photomasks to generate pattern structures composed of 1/1-O(2) and 2/2-O(2). Kelvin probe force microscopy (KPFM) provided a powerful and nondestructive method to image the pattern information. The following studies based on AFM, KPFM and contact angle measurements unfold that the two species 1 and 2 underwent different progressions after the imaging step. Degrading is observed for the monomeric compound 1 and the pattern eventually becomes recognizable in topography. In the oxidized state (1-O(2)) the monomeric species remains physically stable. In consequence, the unreacted portion is removable and the remaining oxygenated form 1-O(2) is sufficiently stable to protect an underlying substrate (e.g., silver) from etching. Thus, the system 1/1-O(2) operates as photoresist. On the other hand, both states of the oligomer 2 remain stable. The film is stable up to temperatures >120 degrees C required to erase the pattern within acceptable time by cycloreversion. Anthracene 2 therefore acts as erasable and rewritable photochromic switch. The different behavior between 1 and 2 is explained by phase transitions which cause crystallization and finally ablation. Such transitions affect only the monomeric system 1/1-O(2) and not the oligomeric system 2/2-O(2). In conclusion, we designed two very similar materials based on diarylanthracenes, which can act either as a photoresist or as a rewritable photochromic switch.