Manganese 3x3 and sqrt 3 x sqrt 3-R30° structures and structural phase transition on w-GaN(0001) studied by scanning tunneling microscopy and first-principles theory

ABHIJIT V. CHINCHORE; KANGKANG WANG; MENG SHI; ANDRADA MANDRU; YINGHAO LIU; MUHAMMAD HAIDER; ARTHUR R. SMITH; VALERIA FERRARI; MARIA ANDREA BARRAL; PABLO ORDEJÓN

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 2013 vol. 87 p. 165426 - 165426

1098-0121

Manganese deposited on the N-polar face of wurtzite gallium nitride [GaN (000-1)] results in two unique surface reconstructions, depending on the deposition temperature. At lower temperature (less than 105 ◦C),it is found that a metastable 3 × 3 structure forms. Mild annealing of this Mn 3 × 3 structure leads to an irreversible phase transition to a different, much more stable √3 ×√3-R30◦ structure which can withstand high temperature annealing. Scanning tunneling microscopy (STM) and reflection high-energy electron diffraction data are compared with results from first-principles theoretical calculations. Theory finds a lowest-energy model for the 3 × 3 structure consisting of Mn trimers bonded to the Ga adlayer atoms but not with N atoms. Thelowest-energy model for the more stable √3 × √3-R30◦ structure involves Mn atoms substituting for Ga within the Ga adlayer and thus bonding with N atoms. Tersoff-Hamman simulations of the resulting lowest-energystructural models are found to be in very good agreement with the experimental STM images.