Driven by the demands of technology, silicon surface chemists seek the creation of truly perfect surfaces � surfaces that are atomically flat, free of contaminants, and perfectly terminated with precisely defined monolayers. To meet this goal, most have sought to understand silicon reactivity in terms of the majority species � the ideal terrace sites on an atomically flat surface. Here, I will show that the chemistry of perfection actually lies in the defects.Because of its importance to the microelectronics industry, silicon oxidation has been studied intensely for decades; however, the disordered nature of the oxide makes this reaction notoriously difficult to understand. In this work, the oxidation reaction is coupled with a subsequent etching reaction, allowing oxidation to literally write an atomic-scale record of its reactivity into the etched surface � a record that can be read with a scanning tunneling microscope (STM) and decoded into site-specific reaction rates, and thus chemical understanding, with the aid of simulations and spectroscopy. This record overturns the long-standing and much-applied mechanism for the aqueous oxidation of the technologically important face of silicon, Si(100), and shows that the unusually high reactivity of a previously unrecognized surface species leads to a self-propagating etching reaction that produces near-atomically flat Si(100) in a beaker at room-temperature � a long-standing technological goal. These findings show that, contrary to expectation, the low-temperature oxidation of Si(100) is a highly site-specific reaction and suggests strategies for functionalization by low-temperature, solution-based reactions.

Award Address  (Arthur W. Adamson Award for Distinguished Service in the Advancement of Surface Chemistry sponsored by the ACS Division of Colloid and Surface Chemistry and the ACS Publications Journal Langmuir). In search of perfection: The quest for atomically flat silicon and the mechanism of silicon oxidation

247th National Meeting (2014)

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