Narrow Results

Large-scale silicon oxide nanowires (SiO${}_x$ NWs) with a diameter about 250 nm on silicon wafers were synthesized by thermal evaporation of silicon monoxide (SiO) powder. In order to investigate the role of distance on the physical properties of SiO${}_x$ NWs, Si substrates were positioned at 5 cm and 10 cm apart from the boat position set at 1150${}^{\circ }$C. The local temperatues of the samples were 1100${}^{\circ }$C and 1050${}^{\circ }$C, respectively. The SEM images and EDS spectra showed interweaved networks of SiO${}_x$ NWs with x = 0.62 and 0.65 in these layers. The XRD patterns showed S1 has a polycrystalline structure (cristobalite), while S2 has amorphous nature. The PL spectra showed an intense blue peak at 468 nm in S1, and a violet peak at 427 nm in S2 that could be related to the differences in the crystallite structures and oxygen vacancies in these samples.

The plasma treatment on SiO₂ substrate surfaces increased the oxygen-containing functional groups or the polar component of the surface free energy and, the wetting characteristics of the underfills/SiO₂. The plasma treatment condition which gave the smallest contact angle between the underfills and SiO₂ was an operating time of 60 sec under O₂ gas atmosphere and a power of 200 W.

In this work, silicon-rich oxide (SRO) films with designed thickness of ~100 nm were deposited by a bipolar pulse and radio frequency magnetron co-sputtering. For comparison, the samples were then treated in a nitrogen atmosphere by conventional rapid thermal annealing (CRTA) or light-filtering rapid thermal annealing (LRTA) at 900–1100°C for 2 min. Raman spectra, grazing incident X-ray diffraction (XRD), transmission electron microscopy (TEM), Hall measurements, and current density–voltage measurements were carried out to analyze the microstructural and electrical properties of samples. Compared with the control sample using CRTA method, the crystalline volume fraction and number density of Si nanocrystals (SiNCs) in silicon oxide prepared by LRTA were greatly increased. The quantum effects of the short wave-length light (less than 800 nm) of these tungsten halogen lamps during the rapid thermal annealing process have negative effects on the formation of SiNCs in SiO₂ films. SiNCs with crystal volume fraction of 73%, average size of 2.53 nm, and number density of ~1.1 × 10¹² cm^-2 embedded in the amorphous SiO₂ matrix can be formed by LRTA at 1100°C. Enhancement of more than one order of magnitude in conductivity and higher current density were obtained from the LRTA annealed sample compared to the CRTA annealed sample. The improvements in conductivity and current density were attributed to the high density SiNCs. Our results show that the LRTA method is a suitable annealing tool for the formation of SiNC in thin SiO_x films.

Various amorphous SiO_x nanotube structures nucleated by GeO_x nanoparticles were synthesized by thermal evaporation method. The presence of Ge does not only nucleate the growth of the SiO_x nanomaterials, but also dopes them. The nanostructure morphology is affected by the substrate temperature, source temperature and GeO_x vapor density through their effect on the size and lifetime of the nucleation center. In general, low substrate temperature promotes the formation of the nanotube bundle structure with 2–3% atomic ratio of Ge doping, and high temperature produces Ge-free much less bundled nanotubes.

In the last years, concepts have been developed to use etched ion tracks in insulators, such as polymer foils or silicon oxide layers as hosts for nano- and microelectronic structures. Depending on their etching procedure and the thickness of the insulating layer in which they are embedded, such tracks have typical diameters between some 10 nm and a few μm and lengths between some 100 nm and some 10 μm. Due to their extremely high aspect ratios, and due to the possibility to cover very large sample areas, they exceed the potential of nanolithography.

In this paper, the strategies of etched ion track manipulation are briefly outlined, that lead to the formation of nanotubules, nanowires, or tubular arrangements of nanoclusters. Examples where nanoelectronic structures are based on single ion tracks, are nanocondensors or sensors for temperature, light, pressure, humidity and/or alcohol vapor. By combination of ion track metallization and conducting track-to-track connections on the foil surface, micromagnets, microtransformers and microcondensors could be formed within polymer foils.

Finally, we present our new "TEMPOS" (Tunable Electronic Material with Pores in Oxide on Silicon) concept where nanometric pores, produced by etching of tracks in silicon oxide on silicon wafers, are used as charge extraction (or injection) channels. In comparison with the metal oxide semiconductor field effect transistors (MOS-FETs), the TEMPOS structures have a number of additional parameters (such as the track diameter, density, and shape, and the material embedded therein and its spatial distribution) which makes these novel structures much more complex. This eventually leads to higher compactation of the TEMPOS circuits and to unexpected electronic properties. TEMPOS structures can overtake the function of tunable resistors, condensors, photocells, hygrocells, diodes, sensors, and other elements. As an example, some corresponding current/voltage relations and TEMPOS circuits are presented. In this work we concentrate on TEMPOS structures with fullerene and phthalocyanine. Though not yet verified, TEMPOS structures could, in principle, be scaled down to nanometer sizes.

Nanometer-scale silicon oxide mask was patterned by atomic force microscope (AFM) lithography for fabrication of nanoelectronic devices. The oxide growth mechanism is similar to a well-known local anodic oxidation, which a negative voltage applied to conductive AFM tip in order to grow oxide patterns on silicon layer surface. The surrounding environment is one of the very important parameter on the formation of nanoscale silicon oxide patterns via AFM lithography. Therefore, in this work, the effect of relative humidity (RH) has been studied systematically in the range of 55–72%. Meanwhile, the applied tip voltage, exposure time, and scanning speed were kept constant during lithography process. From AFM topographic analysis on the fabricated nanopatterns found that the oxide width and thickness are significantly depending on the room humidity. These results proved that the room humidity is playing an important role on the fabrication of nanometer-scale oxide patterns by using AFM nanolithography.

This work presents the results of pulsed plasma-chemical modification of silicon dioxide nanopowder with zinc oxide nanoparticles (ZnO@SiO₂). The obtained ZnO@SiO₂ powders were characterized by transmission electron microscopy (TEM) and X-ray phase analysis. The size of the synthesized particles was in the range of 20–100nm. The photocatalytic characteristics of ZnO@SiO₂ were studied. When exposed to ultraviolet radiation, the methylene blue (MB) decomposes efficiently. Two samples characterized by the content of silicon tetrachloride in the initial mixture were synthesized. The band gap estimated from the absorption spectra calculated from the diffuse reflectance spectra for these samples was 2.4eV and 2.95eV for indirect transitions and 3.03eV and 3.24eV for direct allowed transitions.

In this paper, a simple method for synthesizing SiO_x nanowires and nanocoils is presented. Si substrates with an oxide layer were placed in a tube furnace exposed to temperatures ranging from 900°C to 1200°C for a few hours under a mixture of flowing Ar and H₂ gas maintained at ambient pressure. Nanowires were grown from the surface when the furnace temperature was above 1000°C and a high yield could be achieved at 1100°C. SiO_x nanocoils have also been observed and the sample treated at 1000°C had the highest concentration of them. TEM images show that the nanowires and the nanocoils have an amorphous structure and analysis of EDX spectra (obtained in the TEM) shows that x varies from 1.2 to 2.0. The mechanism of growth is discussed.

Silicon oxide (SiO_x) nanowires have many applications due to their electrical, mechanical and optical properties. Many methods have been reported for the synthesis of SiO_x nanowires. In this paper, previously, we made Ni/SiO₂/Si substrates by dry oxidation and nickel sputtering. Then we successfully fabricated SiO_x nanowires on Ni/SiO₂/Si substrates with hydrogen gas by using simple heating process. We figured out the best temperature and best time duration for SiO_x nanowires' fabrication on Ni/SiO₂/Si substrate. Field emission scanning electron microscope (FE-SEM), field emission transmission electron microscope (FE-TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were taken to analyze these nanowires.