Dynamic force microscopy study of the Ga-rich c(8 x 2) and As-rich c(4 x 4) reconstructions of the GaAs(001) surface

摘要

As-rich and Ga-rich GaAs(001) surfaces were studied with frequency-modulation dynamic force microscopy. By simply changing the parameters of argon sputtering and annealing during sample preparation, surfaces reconstructed with the As-rich c(4 x 4) phase or the Ga-rich c(8 x 2) phase could be obtained. True atomic resolution of the c(8 x 2) reconstruction is achieved by using constant frequency shift imaging. We show that tip functionalization allows selective species imaging. The presence at the tip apex of empty Ga dangling bonds or of fully filled As dangling bonds leads to selective atomic resolution of the As or Ga sublattices of the c(8 x 2) reconstructed surface, respectively. Our observations support the ζ model for the c(8 x 2) reconstruction (but no dimers were found) and the α model for the c(8 x 2) reconstruction (individual As-As dimers were resolved by dynamic force microscopy).