Nanodots

Synthesis of nanodot arrays using self-assembled niobium oxide nanopillar mask by reactive ion etching... 

The formation of nanostructures such as nanodot arrays has drawn a great attention due to the feasible applications in a variety of functional structures and nanodevices containing optoelectronic device, information storage, and sensing media [1-3]. The various methods such as self-assembled nanodots from solution onto substrate, strain-induced growth, and template-based methods have been proposed for the fabrication of nanodot arrays on a large area, [4-6]. However, most of these works can be applied to the small scale systems due to the limited material systems. 

In this report, the fabrication of Si nanodot arrays using niobium oxide nanopillars as an etching mask was performed by an inductively coupled plasma reactive ion etching (ICPRIE). 

The formation of Si nanodot arrays on a substrate was performed by ICPRIE of Si films using self-assembled niobium oxide pillars as an etching mask. The etch rates of niobium oxide pillars and Si films, and the etch selectivity of Si films to niobium oxide were investigated by varying etch parameters in a Ch/Ar gas. The main etch parameters used in this study were the concentration of CI2 gas, coil rf power, and dc-bias to substrate. 

In order to confirm the formation of nanodots, the fabricated nanodot arrays on a substrate were examined using energy dispersive spectroscopy (EDS). The EDS analysis of niobium oxide arrays on Si film before etching (Fig. 2(a)) was shown in Fig. 3(a). The Si peak as well as Nb and O peaks was observed because niobium oxide on Si film was so thin. 

Figures 3(b) and 3(c) were the EDS results of the etched nanodot arrays shown in Figs. 2(b) and 2(c). The EDS of Fig. 3(b) was almost identical to that of Fig. 3(a). It means that niobium oxide masks were still on Si film although the Si dots were formed. Fig. 3(c) was the EDS result of the nanodot arrays etched for longer etch time than Fig. 3(b). The Nb peak disappeared due to the increased etching and it was confirmed that the nanodots consisted of only Si. The diameters of Si nanodots were approximately 20 30 nm. It was demonstrated that the optimal etching condition could form close-packed and highly ordered Si nanodot arrays without niobium oxide mask. It is expected that this novel technique of forming...

Fig. 2. FESEM images of (a) niobium oxide arrays before etching, and of Si nanodot arrays etched for (b) 20 s and (c) 30 s at 20% CI2, 500 W coil rf power, 300 V dc-bias voltage and 5 mTorr gas pressure...

This species has been used as precursor of nanogold particles by electrodeposition. When the electrodeposition is induced from the isotropic state at 117 °C, the nanoparticles obtained are nanodots aggregated in a spherical-like shape. In contrast, the morphology of the nano particles prepared from the SmA mesophase at 111 °C consist of leaf-like forms interlocked in rosettes. 

Link, S. and El-Sayed, M. A. (1999) Spectral properties and relaxation dynamics of surface plasmon electronic oscillations in gold and silver nanodots and nanorods. 

Secondly, we describe the site-selective introduction of a functional molecule, tetrakis-5,10,15,20-(4-carboxyphenyl)porphyrin (TCPP), into the microphase separation structure of a diblock copolymer film of PS-fo-P4VP. Since porphyrin derivatives show various functionalities such as sensitization, redox activity, and nonlinear optical effect, a polymer nanodot array containing a porphyrin at a high concentration would be applicable to a light-harvesing and charge transporting nanochannel. 

Further modification of the above nanostructures is useful for obtaining new functional materials. Thirdly, we apply the dopant-induced laser ablation technique to site-selectively doped thin diblock copolymer films with spheres (sea-island), cylinders (hole-network), and wormlike structures on the nanoscale [19, 20]. When the dye-doped component parts are ablated away by laser light, the films are modified selectively. Concerning the laser ablation of diblock copolymer films, Lengl et al. carried out the excimer laser ablation of diblock copolymer monolayer films, forming spherical micelles loaded with an Au salt to obtain metallic Au nanodots [21]. They used the laser ablation to remove the polymer matrix. In our experiment, however, the laser ablation is used to remove one component of block copolymers. Thereby, we can expect to obtain new functional materials with novel nanostmctures. 

AlSalman,A.,Tortschanoff, A.,Mohamed, M. B., Tonti, D., van Mourik, F. and Chergui, M. (2007) Temperature effects on the spectral properties of colloidal CdSe nanodots, nanorods, and tetrapods. Appl. Phys. Lett., 90, 093104. 

Similarly, monometallic Rh, Pd, and Au and bimetallic Pt-Rh and Pt-Pd nanowires were prepared in FSM-16 or HMM-1 by the photoreduction method [30,33,34]. The bimetallic wires gave lattice fringes in the HRTEM images, and the EDX analysis indicated the homogeneous composition of the two metals. These results show that the wires are alloys of Pt-Rh and Pt-Pd. Mesoporous silica films were also used as a template for the synthesis of uniform metal particles and wires in the channels [35,36]. Recently, highly ordered Pt nanodot arrays were synthesized in a mesoporous silica thin film with cubic symmetry by the photoreduction method [37]. The... 

Figure 5.16 Tapping-mode AFM image of a 25 Cu nanodot array on H-terminated p-Si(l 0 0), formed by nanoindentation. (Reproduced with permission from Ref. [72].)...

Zheng, J., and Dickson, R.M. (2002) Individual water-soluble dendrimer-encapsulated silver nanodot fluorescence./. Am. Chem. Soc. 124, 13982-13983. 

Fig. 12 SEM image of a a Ru04 stained PS-PLA film and b a NisoFe2o nanodot array formed from the resultant nanoporous PS template. Reproduced from [50]...

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