Papers by Keyword: Nanowire

Abstract: We report a facil and robust strategy for fabricating flexible piezoelectric nanogenerator based on free-standing polydimethylsiloxane (PDMS) / ZnO nanowire (NW) hybrid film. Free-standing hybrid film was fabricated by mechanical exfoliation of ZnO NWs grown on a FR₄ substrate. The free-standing ZnO/PDMS hybrid film is robust enough to be transferred into a flexible substrate of polyimide (Kapton) with Au sputtered. The nanogenerator based on the free-standing hybrid film exhibits stable output voltage about 0.7 V and current of 7 nA under pressing conditions. This facil and robust method should hold significant promise applications in efficient energy harvesting.

Abstract: Core–shell Si/SiC nanostructures appear as promising building blocks for sensing applications, thanks to the high chemical stability of SiC coupled with the semiconducting properties of Si. In order to optimize the fabrication process of such structures, Si nanowires were coated with a thin SiC layer, and integrated as back-gated field-effet transistors. Two approaches for the fabrication of the SiC shell were then investigated. The first approach involves chemical vapor deposition of amorphous SiC on Si nanowires, without the need for masking; the second approach involves carbonization of Si surfaces to produce a thin crystalline SiC layer, but requires a larger thermal budget. The resulting structures were analyzed using high-resolution transmission electron microscopy (HR-TEM), and the devices were characterized electrically. Electrical characterization shows that the carbonization approach induces a dramatic decrease in drain-to-source current associated with gate leakage, whereas the electrical performances were preserved in the case of chemical deposition.

Abstract: 3D Simulation was carried out and compared with fabricated ZnO NWFET. The device had the following electrical output characteristics: mobility value of 10.0 cm²/Vs at a drain voltage of 1.0 V, threshold voltage of 24 V, and subthreshold slope (SS) of 1500 mV/decade. The simulation showed that the device output results are influenced by two main issues: (i) contact resistance (R_con ≈ 11.3 MΩ) and (ii) interface state trapped charge number density (Q_IT = 3.79 x 10¹⁵ cm^-2). The Q_IT was derived from the Gaussian distribution that depends on two parameters added together. These parameters are: an acceptor-like exponential band tail function g_GA(E) and an acceptor-like Gaussian deep state function g_TA(E). By de-embedding the contact resistance, the simulation is able to improve the device by producing excellent field effect mobility of 126.9 cm²/Vs.

Abstract: HAuCl₄ was reduced by glucose as reducing agent and dispersant under UV radiation and acetone as photo sensitizer. The experimental samples were characterized by the transmission electron microscopy and UV-visible spectrophotometer, and the results show that these gold nanoparticles’ size is uniform, monodisperse distribution of spherical particles of average diameter of 5.8 nm, and gold nanowires with two-dimensional network structure were successfully prepared. The influence of glucose concentration on reaction under this condition and the mechanism of nucleation and growth of the photochemical reduction were discussed.

Abstract: ZnO NWFETs were fabricated with and without Al₂O₃ passivation. This was done by developing a new recipe for depositing the thin film of ZnO. By using a high donor concentration of 1.7 x 10¹⁸ cm^-3 for the thin film, contact resistance values were lowered (passivated device had R_con = 2.5 x 10⁴ Ω; unpassivated device had R_con = 3.0 x 10⁵ Ω). By depositing Zn first instead of O₂, steep subthreshold slopes were obtained. The passivated device had a subthreshold slope of 225 mV/decade and the unpassivated device had a slope of 125 mV/decade. Well-behaved electrical characteristics have been obtained and the passivated device shows field effect mobility of 10.9 cm²/Vs and the un-passivated device shows a value of 31.4 cm²/Vs. To verify the results, 3D simulation was also carried out which shows that the obtained values of sub-threshold slope translate into interface state number densities of-1.86 x 10¹³ cm^-2 for the unpassivated device and 3.35 x 10¹⁴ cm^-2 for the passivated device. The passivated device is suitable for biosensing applications.

Abstract: Products formed in the discharge region of the DC arc between graphite electrodes in water were studied. Whereas one of them was grown on a cathode and kept whole, the other is arose by erosion of electrodes in powder form and sank or floated in the surrounding water. The structure of the products was studied by SEM and SEM EDX analysis. The whole parts grown on the cathode were made up three different components: (i) almost spherical tiny particulates; (ii) long and narrow linear parts; and (iii) macro particulates of gigantic size. We have identified the size distributions and the number densities for these component parts in the sample as well their mechanical features. The powder samples included bulk particulates of carbon sheets and linear structures, like a thread. The study shows that the long linear structures in the powder sample are formed by the scrolling of carbon layers whereas the ones deposited are formed by a growth mechanism

Abstract: A highly sensitive low-doped ZnO nanowire field effect transistor (NWFET) biosensor has been fabricated and measured. The low doped biosensor with NWFET transducer was used to sense charge of the following substances: lysozyme (LYSO), phosphate buffered saline (PBS), bovine serum albumin (BSA). It achieved maximum sensitivity of -543.2 % for the PBS-LYSO protein and 13,069 % for the PBS-BSA protein. These results were achieved because the electrical measurement and characterisation was focused on the charge effect of the LYSO and BSA acting on the ZnO nanowire subthreshold region. The nano-fabrication process is stable and reproducible. The high sensitivity of the ZnO NWFET biosensor can be exploited for selective analyte detection by functionalizing the nanowire surface with antibodies and/or other biomolecular probe molecules.

Abstract: Gate All-Around (GAA) is considered a key design feature for future CMOS technology. SiGe vs. Si selective etch is required for Si nanowire formation in GAA. It is confirmed the selective SiGe removal with commodity chemical (mixtures of hydrofluoric acid (HF), hydrogen peroxide (H2O2) and acetic acid (CH3COOH, HAc)), however the thick oxidized layer on Si NW was observed after commodity chemical process, which is indicated the significant Si NW loss. On the other hand, the formulated mixture ACT® SG-101, which is focusing on SiGe oxidizer, chemical pH, solvent polarity & corrosion inhibitor for chemical concept, was performed higher selectivity and lower Si loss than commodity chemical. The formulated mixture has also been used to form an inner spacer for cavity etch scheme and confirmed uniform cavity etch and inner spacer filling on topological test structure.

Abstract: For horizontally stacked nanowires or-sheets to compete with finFET, the development of a robust inner spacer module is essential. These inner spacers are required to reduce the parasitic capacitance due to the overlap between the source/drain and gate regions. Here we propose an inner spacer integration scheme for Si gate-all-around (GAA) taking advantage of the selective oxidation and oxide removal of SiGe versus Si. Compared to thermal oxide, we found a very high SiGe-oxide etch rate in aqueous HF solutions. When using an NH₃/NF₃ remote plasma, a reduction in etch rate was found for SiGe-oxide versus thermal oxide. We show Si_0.75Ge_0.25-oxide meets inner spacer requirements for leakage current and electrical breakdown field and finally demonstrate the proposed inner spacer integration scheme using a fin-shaped SiGe/Si multilayer topological-test-structure.

Abstract: A selective wet etching process for fabricating SiGe and Ge nanowires for gate all around transistors is introduced in this paper. Two formulated proprietary chemical mixtures with highly selective etching properties (Si vs. SiGe and SiGe vs. Ge) can effectively dissolve the sacrificial layers with minimal damage to the interstitial nanowire materials. The Auger Electron Spectroscopy (AES) surface characterization indicates that no chemical contamination is left after the wet etching process.