Previous studies have shown that the underpotential deposition (UPD) of a saturated silver chloride solution on Au(111) forms a thermally stable, atomically-thin film, which persists to temperatures ≥ 1,000 K. This layer was applied to the surface at one specific UPD potential and characterized using electrochemical scanning tunneling microscopy (EC-STM) and cyclic voltammetry (CV). However, it has also been found that silver halides (AgX) have two distinct UPD potentials at which a monolayer can be deposited. The two specific UPD values correspond to two different chemical mechanisms of deposition, one in which the silver halide exists as a bare, ionic species and one in which the silver halide exists as a solvated formula unit. Studies on the UPD of a silver chloride formula unit have shown the resulting thin film to be thermally stable, but no study has been done to determine the thermal stability of a thin film deposited from the bare, ionic species. Current studies involve the investigation of the thermal stability of silver chloride UPD on a Au(111) crystal through the use of EC-STM and cyclic voltammetry as a function of deposition potential. EC-STM evidence shows that the amount of Ag on the surface is different depending on the Ag source used, showing a (1x1) configuration for the solvated AgCl monolayer and a (4x4) configuration for the monolayer formed from the bare, ionic species. Additionally, the thermal stability of other silver halides, such as AgBr and AgI, will be explored and characterized using the same techniques. With EC-STM, we plan to study these two underpotential systems and determine how the different AgX sources affect the thermal stability of the monolayer and the resulting physical properties of the bulk system. These thin films have the potential to be used in many applications ranging from imparting thermal stability to microelectronics to exploiting their anti-corrosion properties as the films also form a protective barrier against oxidation.

EC-STM investigation of the thermal stability of silver halide thin films on Au(111)

255th National Meeting (2018)

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