Zuoming Zhao

Direct structural evidences of Mn11Ge8 and Mn5Ge2 clusters in Ge0.96Mn0.04 thin films

Mn-rich clusters in Mn-doped Ge thin films epitaxially grown on Ge (001) have been investigated by various transmission electron microscopy techniques. Both the mysterious Mn11Ge8 and the hexagonal Mn5Ge2 (a=0.72nm and c=1.3nm) clusters were confirmed to coexist in the thicker Ge0.96Mn0.04 film (80nm). Their possible formation mechanism is attributed to the existence of ordered stacking faults. The fact that no Mn-rich clusters found in thinner films (<=40nm) suggests that, for a given Mn concentration and growth/annealing condition, a critical thickness exists for the formation of Mn-rich clusters.

Selective growth of Ge islands on nanometer-scale patterned SiO2∕Si substrate by molecular beam epitaxy

The authors studied the selective growth of Ge islands by molecular beam epitaxy on Si(001) covered with nanometer-scale patterned SiO2 mask generated using self-assembled diblock copolymer. Selective growth is made possible by Ge adatoms desorbing from the SiO2 surface as well as diffusing into the exposed Si area. For the Ge coverage of 2nm, multiple islands are observed along the periphery of individual exposed Si areas. At 3.5nm coverage, the coalescence of small islands with significant strain relaxation becomes evident. The ramifications of the multiple islands morphology and their coalescence on potential device applications are discussed.

Three-stage nucleation and growth of Ge self-assembled quantum dots grown on partially relaxed SiGe buffer layers

We investigate the magnetic field inversion symmetry of the pumped currents in quantum pumps with various discrete symmetries using Floquet scattering matrix approach. We found the pumped currents can have symmetries

Mn behavior in Ge0.96Mn0.04 magnetic thin films grown on Si

I(B,\phi) = -I(-B,-\phi)

Initial stage of InAs growth on Si (001) studied by high-resolution transmission electron microscopy

and

A technique for the measurement of surface diffusion coefficient and activation energy of Ge adatom on Si(001)

I(B,\phi) = I(-B,-\phi)

Direct integration of III–V compound semiconductor nanostructures on silicon by selective epitaxy

, where

Optical properties of InAs quantum dots grown on patterned Si with a thin GaAs buffer layer

\phi

Microstructure analysis of epitaxially grown self-assembled Ge islands on nanometer-scale patterned SiO2∕Si substrates by high-resolution transmission electron microscopy

is the phase difference of two time dependent perturbations, depending on the discrete symmetry considered. The results in the adiabatic limit for each discrete symmetry are compared with those of Brouwers formula.

On the formation mechanism of epitaxial Ge islands on partially relaxed SiGe buffer layers

Mn behaviors in the Ge0.96Mn0.04 thin films grown on Si (001) substrates by molecular beam epitaxy were investigated by high resolution transmission electron microscopy, electron energy loss spectroscopy, and energy dispersive spectroscopy. Unlike the previously reported case of GeMn thin films grown on Ge, Mn has been found to be diffused toward to the surface during the thin film growth. When the Mn concentration is sufficiently high, Mn5Ge3 clusters may be formed. Further annealing of the high Mn concentrated thin film promotes the formation of α-Mn metallic clusters. We believe that all these extraordinary phenomena are attributed to Si as the substrate.