Nonmetal are called "metalloids" mainly in light of their physical resemblance to metals. While they each have a metallic appearance, they are brittle and only fair conductors of electricity. Boron, silicon, germanium, tellurium are semiconductors. Arsenic and antimony have the electronic band structures of semimetals although both have less stable semiconducting allotropes. Astatine has been predicted to have a metallic crystalline structure. Chemically the metalloids generally behave like (weak) nonmetals. They have moderate ionisation energies, low to high electron affinities, moderate electronegativity values, are poor to moderately strong oxidising agents, and demonstrate a tendency to form alloys with metals. The reactive
Silicon-germanium silicon-only technology. Silicon Germanium-on-insulator (SGOI) is a technology analogous to the Silicon-On-Insulator (SOI) technology currently employed in computer chips. SGOI increases the speed of the transistors inside microchips by straining the crystal lattice under the MOS transistor gate, resulting in improved electron mobility and higher drive currents. SiGe MOSFETs can also provide lower junction leakage due to the lower band gap value of SiGe. However, a major issue with SGOI MOSFETs is the inability to form stable oxides with silicon germanium using standard silicon oxidation processing. A silicon germanium thermoelectric device, MHW-RTG3, was used in the Voyager 1 and 2