When SOI wafer is kept at a high temperature, Si overlayer becomes unstable against dewetting and spontanesously agglomerates into islands. On further elevating the temperature, a Si atom reacts with an underlying SiO₂ molecule to produce two SiO molecules. Since SiO molecule is volatile, Si islands evaporate by leaving nano-pores in the dioxide layer.
 In this paper, we study dynamical behavior of an evaporating island in terms of a simple solid-on-solid model with a two-dimensional adsorbate island on a one-dimensional substrate surface. The model is simulated with a kinetic Monte Carlo (KMC) method. Dynamics consists of five elementary processes: 1) Surface diffusion of adatoms A, 2) decomposition of a substrate atom S into A by emitting two oxygen atoms O, 3) reverse of 2), 4) interface diffusion of O, and 5) evaporation of A combined with O at the edge of an island.
 Without decomposition, an adisland as a whole migrates on the substrate surface, and a means square displacement (MSD) of the island's center of mass increases linearly in time. The island diffusion constant Dc decreases as an island size R increases in a power law as Dc~R^-3. With decomposition and evaporation, the temporal behavior of an island MSD in general is classified in three stages: 1) Initially, MSD increases linearly in time, 2) then in an intermediate stage, MSD increases faster than a linear behavior due to the depinning of triple points, and 3) finally until the island disappears, MSD saturates since the island is trapped in a nano-pore it drilled.
 In an early stage of evaporation, the interface between the island and the substrate has two dips near the edges of the island, because those O's produced close to edges can escape from the interface and the decomposition from S to A proceeds, whereas in the center of the island decomposition is balanced with the reverse reaction. Eventually, when the island becomes too small, it is trapped into one of the nano-pore that it drilled. The final shape of a drilled pore is deep when the evaporation rate is large.

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