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Article

Development and Comparative Analysis of Electrochemically Etched Tungsten Tips for Quartz Tuning Fork Sensor

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Department of Mechanical Engineering, University of Engineering & Technology, Peshawar 25000, Pakistan
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Department of Mechanical Engineering, CECOS University of IT and Emerging Sciences, Peshawar 25000, Pakistan
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Department of Mechanical Engineering, Bahauddin Zakariya University, Multan 60011, Pakistan
*
Authors to whom correspondence should be addressed.
Micromachines 2021, 12(3), 286; https://doi.org/10.3390/mi12030286
Received: 11 January 2021 / Revised: 25 February 2021 / Accepted: 25 February 2021 / Published: 8 March 2021
Quartz Tuning Fork (QTF) based sensors are used for Scanning Probe Microscopes (SPM), in particular for near-field scanning optical microscopy. Highly sharp Tungsten (W) tips with larger cone angles and less tip diameter are critical for SPM instead of platinum and iridium (Pt/Ir) tips due to their high-quality factor, conductivity, mechanical stability, durability and production at low cost. Tungsten is chosen for its ease of electrochemical etching, yielding high-aspect ratio, sharp tips with tens of nanometer end diameters, while using simple etching circuits and basic electrolyte chemistry. Moreover, the resolution of the SPM images is observed to be associated with the cone angle of the SPM tip, therefore Atomic-Resolution Imaging is obtained with greater cone angles. Here, the goal is to chemically etch W to the smallest possible tip apex diameters. Tips with greater cone angles are produced by the custom etching procedures, which have proved superior in producing high quality tips. Though various methods are developed for the electrochemical etching of W wire, with a range of applications from scanning tunneling microscopy (SPM) to electron sources of scanning electron microscopes, but the basic chemical etching methods need to be optimized for reproducibility, controlling cone angle and tip sharpness that causes problems for the end users. In this research work, comprehensive experiments are carried out for the production of tips from 0.4 mm tungsten wire by three different electrochemical etching techniques, that is, Alternating Current (AC) etching, Meniscus etching and Direct Current (DC) etching. Consequently, sharp and high cone angle tips are obtained with required properties where the results of the W etching are analyzed, with optical microscope, and then with field emission scanning electron microscopy (FE-SEM). Similarly, effects of varying applied voltages and concentration of NaOH solution with comparison among the produced tips are investigated by measuring their cone angle and tip diameter. Moreover, oxidation and impurities, that is, removal of contamination and etching parameters are also studied in this research work. A method has been tested to minimize the oxidation on the surface and the tips were characterized with scanning electron microscope (SEM). View Full-Text
Keywords: scanning probe microscopy; tungsten tips; electrochemical etching; scanning electron microscope; quartz tuning fork sensor scanning probe microscopy; tungsten tips; electrochemical etching; scanning electron microscope; quartz tuning fork sensor
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MDPI and ACS Style

Ali, A.; Ullah, N.; Riaz, A.A.; Zahir, M.Z.; Khan, Z.A.; Shah, S.S.A.; Rehman Siddiqi, M.U.; Hassan, M.T. Development and Comparative Analysis of Electrochemically Etched Tungsten Tips for Quartz Tuning Fork Sensor. Micromachines 2021, 12, 286. https://doi.org/10.3390/mi12030286

AMA Style

Ali A, Ullah N, Riaz AA, Zahir MZ, Khan ZA, Shah SSA, Rehman Siddiqi MU, Hassan MT. Development and Comparative Analysis of Electrochemically Etched Tungsten Tips for Quartz Tuning Fork Sensor. Micromachines. 2021; 12(3):286. https://doi.org/10.3390/mi12030286

Chicago/Turabian Style

Ali, Ashfaq, Naveed Ullah, Asim A. Riaz, Muhammad Z. Zahir, Zuhaib A. Khan, S. S.A. Shah, Muftooh U. Rehman Siddiqi, and Muhammad T. Hassan. 2021. "Development and Comparative Analysis of Electrochemically Etched Tungsten Tips for Quartz Tuning Fork Sensor" Micromachines 12, no. 3: 286. https://doi.org/10.3390/mi12030286

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