Using nonequilibrium Green's function combined with density functional theory, we investigate the transport properties of a single perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecular device before and after adsorbing single heavy metal atoms Ni, Pd, Cd, Cu, Zn, and Ag. We find that the adsorption of a single Ni or Pd atom has a slight modulation on the I–V characteristic of the junction. However, the adsorptions of a single Cd, Cu, Zn, and Ag atom can shift the transmission spectra of the junctions obviously leading to the large de...