Self-Assembled Monolayers of Triazolylidenes on Gold and Mixed Gold/Dielectric Substrates

<i>N</i>-Heterocyclic carbenes (NHCs) have emerged as valuable ligands for surface chemistry. They can be used to prepare robust self-assembled monolayers (SAMs) for a variety of applications, including as small-molecule inhibitors (SMIs) for metal surfaces in the fabrication of next-generation integrated circuits with angstrom precision. However, little work has been performed to assess the effect of structural and electronic modifications to the basic NHC structure. Herein, we report the design and deposition of a series of 1,2,3-triazolylidene (Tz)-type carbenes on gold (Au) and Au/SiO₂ patterned substrates. Triazolylidenes are an important class of stable carbenes that can be prepared with ease by using click chemistry. In this work, we studied the selective deposition of 1,2,3-triazolium hydrogen carbonate salts. The thermal properties of these precursors were measured and shown to be appropriate for either solution or vapor phase deposition. Tz-SAM stability was studied by time-of-flight secondary-ion mass spectrometry (ToF-SIMS) of Tz SAMs before and after exposure to various conditions, leading to the conclusion that Tz SAMs have thermal stabilities greater than that of NHC SAMs reported to date. Tz SAMs were analyzed by using X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS) and contact angle measurements. High selectivity for deposition on metal regions over dielectric regions on patterned Au/SiO₂ substrates enabled the use of Tzs as an entirely new class of SMIs on preventing ZnO deposition, providing considerable potential utility in microelectronics fabrication methods. Structure-property relationships were studied and provided key insight into the effectiveness of the SAM as a blocking agent.