Thermal vibrations of a two-dimensional vacancy island crystal in a strained metal film

Vacancy islands formed during room-temperature exposure to sulfur of a subm onolayer Ag him on Ru(0001) order spontaneously to form a triangular lattic e at an island area fraction just above 20%. A normal mode decomposition of the thermal vibrations of this vacancy island crystal, measured with time- resolved scanning tunneling microscopy, obtains Lame coefficients in the ra nge of 10(8) N m(-2). We show that these estimates are consistent with stab ilizing forces derived from long-range elastic interactions between the isl ands. (C) 1999 Elsevier Science B.V. All rights reserved.