The role of oxidized germanium in the growth of germanium nanoparticles on hafnia

The role oxidized germanium (GeOx) plays in germanium (Ge) nanoparticle growth on hafnia is reported. Oxide islands, in the form of hafnium germinate, form on hafnia during the initial stages of growth. The Ge adatoms are oxidized by background oxidants, such as water, only when they are in contact with the hafnia surface. Once a sufficient amount of hafnium germinate has formed, Ge nanoparticles nucleate such that nanoparticle growth proceeds by Ge growth on GeOx. Nanoparticles are not deposited on the hafnia but only on the interfacial oxide islands formed early in the growth process. Annealing hafnia in a silane ambient after Ge nanoparticle growth reduces the amount of GeOx and appears to transform it into a hafnium silicate. Furthermore, the electronic and/or chemical interaction between the Ge nanoparticles and the hafnia substrate is changed by the silane annealing step as reflected in the binding energy shift in the Ge 2p signal and the increased retention time of metal-oxide-semiconductor capacitors made from Ge nanoparticles and hafnia. Pretreating hafnia in silane leads to hafnium silicate islands and subsequent Ge nanoparticle growth proceeds on the silicate islands.