Growth of ultrathin layers of Au on LiNbO3(0 0 0 1) measured with atomic force microscopy

Atomic force microscopy (AFM) has been used to characterize the growth of Au deposited via evaporation onto the positive face of single crystalline, lithium niobate, LiNbO₃(0 0 0 1) surface. In order to study the mechanisms for the ordering and aggregation of a noble metal on this ferroelectric surface, topographic and phase contrast imaging of the fractional surface coverage of Au were performed. Atomically flat, uniformly poled LiNbO₃ surfaces were prepared via an ambient high temperature anneal and served as a support for the thin gold films. These gold atomic layers were grown using electron bombardment evaporation sources under ultra-high vacuum (UHV) conditions and subsequently characterized under both vacuum and ambient environments. Using AFM it was found that gold preferentially nucleates at the top of LiNbO₃ substrate step edges. With increased coverage, island formation proceeds due to local aggregation of adsorbed gold on each substrate terrace. Based on local imaging of the growth morphology, the data is discussed in terms of thin film growth mechanisms as well as the influence of native surface features such as defects and charge distribution. Understanding growth mechanisms for gold layers on ferroelectric surfaces allows for a fuller appreciation of how atomic deposition of metal atoms on patterned poled LiNbO₃ surfaces would occur as well as yielding greater insight on the atomic characteristics of metals on ferroelectric interfaces.