[Spm] re: Sharp STM tips

[Chris Pawlowicz]

Don,

The two main types of STM tips seem to be W and Pt-Ir. W oxidizes in air, Pt-Ir does not (are you doing STM in air or UHV?). I've seen where people used W tips etched in HF just prior to scanning and they lasted a little while before oxidizing.

Usually W tips are electrochemically etched, usually Pt-Ir tips are cut/torn (although they can also be etched).

I would think that using electrochemical etching (where you control the voltage/current and can move the sample in/out of the solution) you could control the tip characteristics as required.

There are a number of home-brew tools out there or even commercial ones-
http://www.omicron.de/products/accessories//w_tek_tip_etching_tool/media/w_tek_tip_etching_tool_1.pdf

I've been making my own Pt-Ir tips using the 'cut&tear' method and scanning in air.
I do have some pix of HOPG lattice this way but it took a few tries and I'm using a big AFM (not the most suited for small scans).

Chris Pawlowicz
Lab Development Manager
Semiconductor Insights Inc.
Phone: (613) 599-5145 x 4454
Fax: (613) 599-6501
Email: chrisp at semiconductor.com
Web: www.semiconductor.com



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Date: Wed, 21 Oct 2009 13:05:21 -0400
From: "Don Chernoff at ASM" <donc at asmicro.com>
Subject: [Spm] Sharp STM tips

Dear Colleagues:

How would one get or make STM tips with the following characteristics:
-apex has 1 nm radius of curvature (or less) -opening angle (or cone angle) in the 5 nm above the apex is less than 60 degrees (full angle) -tip material is stable in air -can achieve atomic resolution

regards,
Don
=============================================
Don Chernoff, Ph.D., President

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