Memory characteristics of Pt nanocrystals self-assembled from reduction of an embedded PtOx ultrathin film in metal-oxide-semiconductor structures

The nonvolatile memory characteristics of metal-oxide-semiconductor structures containing Pt nanocrystals in SiO2 gate oxide were studied. The Pt nanocrystals of 2-3 nm in diameter were self-assembled from reduction of an ultrathin PtOx layer embedded in the SiO2 by vacuum annealing at 425degreesC. A large hysteresis loop was found in the capacitance-voltage (C-V) relation indicating this significant memory effect. However, two different charge storage mechanisms were found for the Pt nanocrystals in devices with different tunnel oxide thickness. A counterclockwise C-V hysteresis was induced from substrate injection for the devices made with a thin tunnel oxide layer 2.5-5.0 nm thick. Contrast, a clockwise behavior attributed to the electron transfer from charged defects in the gate oxide was found for the devices having a tunnel oxide layer 7.5 nm thick. The relatively stable memory characteristics of Pt nanocrystals resulted from substrate injection were also demonstrated. (C) American Institute of Physics.