Papers by Keyword: Nanodots

Abstract: As an emerging subgroup of 2D materials, monoelemental layered materials and their hydrogenated analogues (Xanes) such as silicane and germanane, have attracted considerable interest due to their remarkable combination of physical, chemical, and (opto)electronic properties. On the other hand, changing the size and structure of two-dimensional materials result to nanostructures with new and unique properties. In this direction, here we present the transformation of germanane and siloxane sheets into nanoscrolls and nanodots respectively, towards the generation of novel 0D and 1D nanostructures.

Abstract: Dip-pen nanolithography (DPN), based on atomic force microscope (AFM) system, is an effective method for nanoscale science and engineering, and the potential applications of DPN will be shown in the field of nanomechanics, nanomaterials, nanobiotechnology, nanomedicine. And the novel combined-dynamic mode DPN (CDDPN), rather than mostly used contact mode DPN or tapping mode DPN, becomes the important tool for the fabrication of nanodots with the direct-writing method of depositing the ink onto the hard silicon surface at the predetermined position, which is presented in the corresponding experiments. In addition, the size of nanodots gradually decreases in the diameter with the increase of the number of nanodots in the case of AFM tip dipping in ink once. However, the size in height does not monotonically reduce as the reduction of the ink, which is affected by the interaction among the relative humidity, AFM tip, substrate material, surface roughness, etc. For the better nanolithography quality of the nanodot, the nanolithography process, under the optimized process parameters, is accomplished once without the intermediate scan imaging process as much as possible.

Abstract: We studied optical properties of copper nanowires fabricated by a shadow deposition method. We found that the optical absorption spectra of thinner nanowires exhibited stronger anisotropic absorption than thickner nanowires. Absorption maxima are located at lower photon energy when incident field is parallel to the wire axes than they are perpendicular to each other. They also shift to lower energy when the widths of nanowires are increased.

Abstract: ZnO nanostructures with controlable properties were synthesized by a reverse micellar system. The morphology and photoluminescence of ZnO nanostructures can be controlled by changing the the ratio of reaction Zn(NO3)2 and MEA. As the ratio of MEA/ Zn(NO3)2 is low, ZnO nanodots were generated with strong blue emission; as the ratio of MEA/ Zn(NO3)2 is increased, the formation of ZnO nanorods with green emission were synthesized. Since the photoluminescence (PL) properties could be adjusted by varying the nanostructures, these ZnO materials have high potential on different applications, for instance, as fluorescence probes.

Abstract: ZnO nanostructures with controllable morphology were synthesized by confining the reaction of Zn(NO3)2 and MEA in Reverse Micellar system composed with CCl4-AOT-Water. It was found that the ratio of MEA/ Zn(NO3)2 is decisive on the morphology of ZnO nanostructures. As the lower ratio of MEA/ Zn(NO3)2 is lower than 2:1, ZnO nanodots with a size about 5 nm were generated; the increase in the ratio of MEA/ Zn(NO3)2 leads to the formation of ZnO nanorods.

Abstract: Nickel- and Platinum-silicide nanodots with an areal density of the order of ~1011cm-2 were successfully formed on thermally-grown SiO2 through a process of ultrathin metal film formation on self-assembled Si quantum dots (QDs) on SiO2 and subsequent remote H2 plasma exposure. Chemical shifts in photoemission spectra of core lines and changes in valence band spectrum and work function value with the remote H2-plasma treatment show that silicidation of pre-grown Si-QDs is promoted by the remote H2-plasma treatment. Electrical separation among so-prepared nanodots was verified from the surface potential change after applying a dc bias between the AFM tip and the sample surface. From temporal decay in the surface potential after electron injection to the nanodots, we confirmed that silicide nanodots have superior charge retention to that of Si nanodots with almost the same size as expected in a deeper potential well for electrons in silicide dots than pure Si-QDs. In the application of silicide nanodots to a floating gate in MOS capacitors, distinct hysteresis characteristics caused by charging and discharging of several electrons per dot were verified by capacitance-voltage measurements.

Abstract: We demonstrated a new fabrication method of Pt- and Ni-silicide nanodots with an areal density of the order of ~1011 cm-2 on SiO2 through the process steps of ultrathin metal film deposition on pre-grown Si-QDs and subsequent remote H2 plasma treatments at room temperature. Verification of electrical separation among silicide nanodots was made by measuring surface potential changes due to electron injection and extraction using an AFM/Kelvin probe technique. Photoemission measurements confirm a deeper potential well of silicide nanodots than Si-QDs and a resultant superior charge retention was also verified by surface potential measurements after charging to and discharging. Also, the advantage in many electron storage per silicide nanodot was demonstrated in C-V characteristics of MIS capacitors with silicide nanodots FGs.

Abstract: We report a fabrication of high-density nanodots by photodoping in overdoped Bi2Sr2CaCu2O8+d thin film (Tc = 80 K). A scanning near-field optical microscope probe is used to locally excite carrier, and photodoped region is associated with lower Tc phase (Tc = 75 K) via overdoping. Nanoscale characterizations with optical reflectivity reveal that nanodots (30-nm diameter) are regularly distributed in 50-nm step. The resultant films with photoinduced nanodots enhance Jc, a situation being similar to strong pinning effects observed in films modified by either ion irradiation or sputtered nanoparticles. These results suggest that photoinduced nanodots with lower Tc act as effective pinning centers.