Large-area Silicon Nanowire Arrays Research Articles

Review of nanostructured devices for thermoelectric applications.

A big research effort is currently dedicated to the development of thermoelectric devices capable of a direct thermal-to-electrical energy conversion, aiming at efficiencies as high as possible. These devices are very attractive for many applications in the fields of energy recovery and green energy harvesting. In this paper, after a quick summary of the fundamental principles of thermoelectricity, the main characteristics of materials needed for high efficiency thermoelectric conversion will be discussed, and a quick review of the most promising materials currently under development will be given. This review paper will put a particular emphasis on nanostructured silicon, which represents a valid compromise between good thermoelectric properties on one side and material availability, sustainability, technological feasibility on the other side. The most important bottom-up and top-down nanofabrication techniques for large area silicon nanowire arrays, to be used for high efficiency thermoelectric devices, will be presented and discussed.

Si Nanowire Anode Prepared by Chemical Etching for High Energy Density Lithium-ion Battery

Silicon nanowire arrays were fabricated by metal-assisted chemical etching of single crystal silicon wafer. Then the silicon nanowire powder was obtained via ultrasonicating from silicon wafer and utilized as the anode elec- trode material of lithium ion battery. The effects of Ag catalyst deposition process and the subsequent anisotropic chemical etching on the formation of silicon nanowires were systematically investigated. The redistribution of Ag par- ticles was found during the chemical etching. The large-area silicon nanowire arrays with proper length-diameter ratio were obtained by optimizing the concentration of AgNO3, HF and H2O2 solution. The silicon nanowires exhibited the classical alloy-reaction plateaus of silicon and the specific capacity above 1800 mAh/g prior to the sixth cycle.

Fabrication of Large-Area Silicon Nanowire Arrays Based on Electroless Metal Deposition

Electroless metal deposition is a simple, low-cost and effective method for fabricating silicon nanowire arrays and has been used widely in micro electromechanical industry. In this paper, large-area silicon nanowire arrays are prepared successfully with mixed AgNO3 and HF solution by this method at normal temperature and pressure. It has been proved the best equality of silicon nanowires can be obtained at the concentration ratio of 0.02 mol/l: 5mol/l for AgNO3 and HF and 1h reaction time. The influence of nano metal particles on the growth, the wire diameter, the distribution and the array of silicon nanowires are analyzed. Experimental results show the distribution and wire diameter of silicon nanowires can be controlled effectively by nano metal particles deposited on silicon wafers. The length of silicon nanowires increases with the reaction time and the average growth velocity is predicted to be 0.5～0.7μm/min. The equality of silicon nanowires with nano Au particles is better than those with nano Pt particles. The reaction mechanism of preparing large-area silicon nanowire arrays is analyzed as the result of the deoxidization of silver ion and the removal of the oxidized silicon solution by reacting with HF.

Preparation and Characterization of Silicon Nanowire Arrays for Solar Cell

Large-area silicon nanowire arrays (SiNWs) were prepared by etching silicon substrate in HF/AgNO3 system solution at near room temperature. Morphology of SiNWs was characterized by scanning electron microscopy. The results showed that morphology of SiNWs could be influenced by solution ratio, temperature and reaction time in the hydrothermal system. The length of SiNWs was about 30-40 μm, and the diameter of SiNWs was in the range of 100-300 nm. SiNWs owned strong optical absorption capacity and could be used for application in solar cell.

Phonon thermal conductivity suppression of bulk silicon nanowire composites for efficient thermoelectric conversion

Vertically-aligned silicon nanowires (SiNWs) that demonstrate reductions of phonon thermal conductivities are ideal components for thermoelectric devices. In this paper, we present large-area silicon nanowire arrays in various lengths using a silver-induced, electroless-etching method that is applicable to both n- and p-type substrates. The measured thermal conductivities of nanowire composites are significantly reduced by up to 43%, compared to that of bulk silicon. Detailed calculations based on the series thermal resistance and phonon radiative transfer models confirm the reduction of thermal conductivity not only due to the increased air fraction, but also the nanowire size effect, suggesting the soundness of employing bulk silicon nanowire composites as efficient thermoelectric materials.

Fabrication and Properties of Large-Area Silicon Nanowire Arrays

Wet chemical etching with dry metal deposition method has been developed to fabricate large-area aligned silicon nanowire (SiNW) arrays. The combination of nanoclusters Ag film with proper interconnection and interspaces (of about 20 nm thick), and proper temperature during etching (from 20 to 80 °C) is vital to successfully fabricating large-area uniform SiNW arrays. Raman and photoluminescence spectra of the SiNW arrays indicated their potential applications in chemical detection and optical devices ,respectively.

Synthesis of Large-Area Silicon Nanowire Arrays via Self-Assembling Nanoelectrochemistry

Large-area silicon nanowire arrays have been prepared on a silicon wafer without the use of a template. The simple method, which can be carried out near room temperature, involves the nanoelectrochemistry of silver nanowires in an aqueous HF solution containing silver nitrate. This technique may be generally applicable to other semiconductors and metals. The Figure shows nanodendritic silicon wires.