Date of Graduation

8-2013

Document Type

Thesis

Degree Name

Master of Science in Physics (MS)

Degree Level

Graduate

Department

Physics

Advisor/Mentor

Thibado, Paul M.

Committee Member

Li, Jiali

Second Committee Member

Li, Jiali

Third Committee Member

Kennefick, Julia D.

Fourth Committee Member

Chen, Jingyi

Keywords

Pure sciences; Etching methods; Fabrication of tungsten tips

Abstract

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's 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' 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' 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' 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' shapes. The fabricated tips through various etching methods are recommended to study the surface of material in the STM chamber.

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