Photoemission spectroscopy has shown that each Ag atom in its two-dimensional adatom gas ͑2DAG͒ phase deposited on the Si͑111͒-ͱ3ϫͱ3-Ag surface at room temperature donates one electron into an antibonding surface-state band of this substrate, resulting in a steep increase in electrical conductance through the band. The surface space-charge layer makes no contribution to the conductance increase by the 2DAG adsorption, estimated from the band-bending measurements. When the 2DAG nucleates into three-dimensional Ag microcrystals by further deposition beyond a critical supersaturation coverage, the carrier-doping effect vanishes, returning to a lower conductance. These results reveal that the surface state acts as a surface conduction band. The electron mobility in this band is estimated to be on the order of 10 cm 2 /V s.

2The effects of the addition of Cr, Mo, and/or Ni on the Charpy impact toughness of a 0.2 pct C-1.5 pct Si-1.5 pct Mn-0.05 pct Nb transformation-induced plasticity (TRIP)-aided steel with a lath-martensite structure matrix (i.e., a TRIP-aided martensitic steel or TM steel) were investigated with the aim of using the steel in automotive applications. In addition, the relationship between the toughness of the various alloyed steels and their metallurgical characteristics were determined.When Cr, Cr-Mo, or Cr-Mo-Ni was added to the base steel, the TM steel exhibited a high upper-shelf Charpy impact absorbed value that ranged from 100 J/cm 2 to 120 J/cm 2 and a low fracture appearance transition temperature that ranged from 123 K to 143 K (−150 C to −130 °C), while also exhibiting a tensile strength of about 1.5 GPa. This impact toughness of the alloyed steels was far superior to that of conventional martensitic steel and was caused by the presence of (i) a softened wide lath-martensite matrix, which contained only a small amount of carbide and hence had a lower carbon concentration, (ii) a large amount of finely dispersed martensite-retained austenite complex phase, and (iii) a metastable retained austenite phase of 2-4 vol pct in the complex phase, which led to plastic relaxation via a strain-induced transformation and played an important role in the suppression of the initiation and propagation of voids and/or cleavage cracks.

When Ag adatoms were deposited on top of the Si͑111͒-ͱ3ϫͱ3-Ag surface at room temperature with less than a critical coverage ⌰ C (ϳ0.03 atomic layer͒, they were found to exist as a supersaturated metastable two-dimensional gas phase, which made the surface electrical conductance extremely high. With the coverage beyond ⌰ C , the gas phase began to nucleate into three-dimensional microcrystals, leading to a steep reduction in the electrical conductance. A kinetic overshoot beyond the critical supersaturation for nucleation was also detected in in situ conductance measurements during the Ag deposition.