Characterization of PTCDA nanocrystals on Ge(001):H-(2×1) surfaces

Extended iron phthalocyanine islands self-assembled on a Ge(001):H surface

“…Finally, hydrogen-passivated semiconductors may also provide sufficient isolation for organic molecules to allow for the growth of molecular crystals. It has been already shown that PTCDA molecules form ordered islands on hydrogen-passivated Si or Ge surfaces [ 36 – 39 ]. For instance, it has been shown that on Ge(001):H those molecules form hexagonal islands composed from flat-lying molecules that are sufficiently decoupled from the underlying semiconductor [ 36 ].…”

“…It has been already shown that PTCDA molecules form ordered islands on hydrogen-passivated Si or Ge surfaces [ 36 – 39 ]. For instance, it has been shown that on Ge(001):H those molecules form hexagonal islands composed from flat-lying molecules that are sufficiently decoupled from the underlying semiconductor [ 36 ]. Vicinal Si(001):H has been applied in order to achieve control over the growth of molecular columns of CuPc molecules [ 40 ].…”

Adsorption of PTCDA on Ge(001)

“…Its planar shape is very well suitable for STM studies. On less reactive substrates such as metal surfaces, metal-terminated Si surfaces, or hydrogen-passivated surfaces of Ge(001) and Si(001), the PTCDA molecules tend to diffuse and self-order. − It is also reported that the molecules are in the physisorbed state and interact mostly by van der Waals (vdW) forces on rutile TiO 2 (110) . On more reactive surfaces, such as those of clean Si, the molecules form stronger covalent bonds with substrates and do not diffuse in general. − So far, adsorption of PTCDA on Ge(001) has been reported only briefly without any discussions about its atomic adsorption configurations …”

Transformations of PTCDA structures on rutile TiO2 induced by thermal annealing and intermolecular forces

“…However, on highly reactive substrates exhibiting a large density of dangling bonds exposed at the vacuum interface, such as InAs, Si or Ge, strong molecule–substrate coupling hinders the growth of any regular structure. Interestingly, the introduction of a single atomic layer of hydrogen dramatically changes the situation in favour of molecule–molecule interactions and allows for the formation of nanocrystalline islands [ 30 – 34 ].…”