Realizing High Thermoelectric Performance at Ambient Temperature by Ternary Alloying in Polycrystalline Si1-x-yGexSny Thin Films with Boron Ion Implantation.

The interest in thermoelectrics (TE) for an electrical output power by converting any kind of heat has flourished in recent years, but questions about the efficiency at the ambient temperature and safety remain unanswered. With the possibility of integration in the technology of semiconductors based on silicon, highly harvested power density, abundant on earth, nontoxicity, and cost-efficiency, Si1-x-yGexSny ternary alloy film has been investigated to highlight its efficiency through ion implantation and high-temperature rapid thermal annealing (RTA) process. Significant improvement of the ambient-temperature TE performance has been achieved in a boron-implanted Si0.864Ge0.108Sn0.028 thin film after a short time RTA process at 1100 °C for 15 seconds, the power factor achieves to 11.3 µWcm-1 K-2 at room temperature. The introduction of Sn into Si1-xGex dose not only significantly improve the conductivity of Si1-xGex thermoelectric materials but also achieves a relatively high Seebeck coefficient at room temperature. This work manifests emerging opportunities for modulation Si integration thermoelectrics as wearable devices charger by body temperature.

Germanene Epitaxial Growth by Segregation through Ag(111) Thin Films on Ge(111).

Large-scale two-dimensional sheets of graphene-like germanium, namely, germanene, have been epitaxially prepared on Ag(111) thin films grown on Ge(111), using a segregation method, differing from molecular beam epitaxy used in previous reports. From the scanning tunneling microscopy (STM) images, the surface is completely covered with an atom-thin layer showing a highly ordered long-range superstructure in wide scale. Two types of protrusions, named hexagon and line, form a (7√7 × 7√7) R19.1° supercell with respect to Ag(111), with a very large periodicity of 5.35 nm. Auger electron spectroscopy and high-resolution synchrotron radiation photoemission spectroscopy demonstrate that Ge atoms are segregated on the Ag(111) surface as an overlayer. Low-energy electron diffraction clearly shows incommensurate "(1.35 × 1.35)" R30° spots, corresponding to a lattice constant of 0.39 nm, in perfect accord with close-up STM images, which clearly reveal an internal honeycomb arrangement with corresponding parameter and low buckling within 0.01 nm. As this 0.39 nm value is in good agreement with the theoretical lattice constant of free-standing germanene, conclusively, the segregated Ge atoms with trivalent bonding in honeycomb configuration form a characteristic two-dimensional germanene-like structure.

Growth and applications of GeSn-related group-IV semiconductor materials.

We review the technology of Ge1-x Sn x -related group-IV semiconductor materials for developing Si-based nanoelectronics. Ge1-x Sn x -related materials provide novel engineering of the crystal growth, strain structure, and energy band alignment for realising various applications not only in electronics, but also in optoelectronics. We introduce our recent achievements in the crystal growth of Ge1-x Sn x -related material thin films and the studies of the electronic properties of thin films, metals/Ge1-x Sn x , and insulators/Ge1-x Sn x interfaces. We also review recent studies related to the crystal growth, energy band engineering, and device applications of Ge1-x Sn x -related materials, as well as the reported performances of electronic devices using Ge1-x Sn x related materials.