Fabrication of Tungsten Tips Suitable for Scanning Probe Microscopy by Electrochemical Etching Methods

The fabrication of metal tips is becoming an interesting field for scientists who are working in spectroscopy measurements. A significant amount of work has already been done in the tips fabrication process. Metal tips used to analyze the surface of materials play a key role in the scanning tunneling microscope (STM) technique. It\u27s remarkable quality that it is used to study the surface of material at the atomic level. There are various methods used in the tips fabrication process. Of diverse methods, three different electrochemical etching methods: submerged method, single lamella drop-off method, and double lamella drop-off method are commonly used to make various tips\u27 shapes such as smaller cone shape, larger cone shape, sharp cone shape, and extremely sharp cone shape at room temperature are reported in this thesis. With submerged method, we made various tips in different etching parameters. The bulk surfaces of the etched tips were characterized using a simple optical microscope. Various tips shapes affected by etching parameters are discussed in this thesis. To better control tips\u27 shapes, a single lamella method was used. However, the tips still etched when the lower part of the etching wire dropped because there was no auto cutoff etching circuit at the end of the etching process. Sometimes, this method produced non-cone shapes tips. To overcome this problem, a double lamella drop-off method was finally used. In this method, the various tips\u27 shapes were made by the variation of the etchant height from the upper mark of the etch stop on the etching tungsten wire. The etch stop was enough to control the tips\u27 shapes. The fabricated tips through various etching methods are recommended to study the surface of material in the STM chamber

Controlled electrochemical growth of ultra-long gold nanoribbons

Citation: Basnet, G., Panta, K. R., Thapa, P. S., & Flanders, B. N. (2017). Controlled electrochemical growth of ultra-long gold nanoribbons. Applied Physics Letters, 110(7), 5. doi:10.1063/1.4976027This paper describes the electrochemical growth of branchless gold nanoribbons with similar to 40 nm x similar to 300 nm cross sections and >100 mu m lengths (giving length-to-thickness aspect ratios of > 10(3)). These structures are useful for opto-electronic studies and as nanoscale electrodes. The 0.75-1.0V voltage amplitude range is optimal for branchless ribbon growth. Reduced amplitudes induce no growth, possibly due to reversible redox chemistry of gold at reduced amplitudes, whereas elevated amplitudes, or excess electrical noise, induce significant side-branching. The inter-relatedness of voltage-amplitude, noise, and side-branching in electrochemical nanoribbon growth is demonstrated. Published by AIP Publishing

Laser-Induced Electron Emission from Au Nanowires: A Probe for Orthogonal Polarizations

Photoelectron field emission, induced by femtosecond laser pulses focused on metallic nanotips, provides spatially coherent and temporally short electron pulses. The properties of the photoelectron yield give insight into both the material properties of the nanostructure and the exciting laser focus. Ultralong nanoribbons, grown as a single crystal attached to a metallic taper, are sources of electron field emission that have not yet been characterized. In this report, photoemission from gold nanoribbon samples is studied and compared to emission from tungsten and gold tips. We observe that the emission from sharp tips generally depends on one transverse component of the exciting laser field, while the emission of a blunted nanoribbon is found to be sensitive to both components. We propose that this property makes photoemission from nanoribbons a candidate for position-sensitive detection of the longitudinal field component in a tightly focused beam

Laser-Induced Electron Emission from Au Nanowires: A Probe for Orthogonal Polarizations

Photoelectron field emission, induced by femtosecond laser pulses focused on metallic nanotips, provides spatially coherent and temporally short electron pulses. The properties of the photoelectron yield give insight into both the material properties of the nanostructure and the exciting laser focus. Ultralong nanoribbons, grown as a single crystal attached to a metallic taper, are sources of electron field emission that have not yet been characterized. In this report, photoemission from gold nanoribbon samples is studied and compared to emission from tungsten and gold tips. We observe that the emission from sharp tips generally depends on one transverse component of the exciting laser field, while the emission of a blunted nanoribbon is found to be sensitive to both components. We propose that this property makes photoemission from nanoribbons a candidate for position-sensitive detection of the longitudinal field component in a tightly focused beam