Nanometer-sized inorganic particles play an important role in modern nanotechnology owing to their superior characteristics that can lead to fascinating function that are difficult to be realized using conventional used bulk materials. Recently the development of shape-controlled synthesis techniques make possible to obtain various well-defined shapes of nanoparticles with high yield. To determine their surface-to-volume ratio and crystal structure are expected to lead to improvement in performance in given application.

In this paper, we demonstrated fabrication of various metal nanodots MOS capacitors for floating nanodot gate memory using a evaporation-based colloidal self-assembly in order to attain a tight control over the size, shape, and density of metal nanodots, as well as the study of their effects on the charge injection characteristics of the nanodot arrays.

We synthesized Au nanoparticles with 2nm diameter by solution plasma processing in aqueous solution. The surface was modified with organic surfactants which tuned their zeta-potential to be approximately -40mV. We have recently proposed a versatile method for the fabrication of self-assembled metallic nanodot arrays onto a SiO2/Si substrate with dimension of 50 x 100mm2 by using a newly developed electrostatistically-driven self-assembly. The substrate surface was modified with amino-silane agents prior to use assembly. In order to make MOS capacitor containing Au nanodot array as a charge trapping layer, the Au nanodot array was embedded in a gate oxide.

By precise control of the velocity of the leading edge of a liquid slug, the volume ratio of the particles, and the deposition rate, we were able to reproducibly form an array consisting of a single layer of Au nanodot array with density of 1012particles/cm2. We further demonstrated the charge injection characteristics of the Au nanodot array, embedded in the ultra-thin SiO2 layer consisting of both thermally grown tunnel oxide and RF-driven sputtered control oxide layer. Counterclockwise hysteresis was observed reproducibly, whereas there was no hysteresis in the C-V curve of the MOS capacitor without Au nanodots. This hysteresis indicates the charging and discharging of the embedded Au nanodots. This electron confinement caused the flat-band voltage shift observed as the capacitance hysteresis.