Batch fabricated scanning Hall probes by corner lithography

Abstract

In this chapter, I discuss nanometer sized Hall crosses on cantilever probes, fabricated by means of corner lithography. Scanning attempts on a permanent magnet show a strong topographic cross-talk. As this cross-talk was three orders of magnitude larger than the expected Hall signal, magnetic imaging over such a rough surface was impossible. We investigated the origin of the cross-talk by four different methods. These measurements clearly show that the asymmetry in the Hall cross, caused by fabrication imperfections, leads to an extra series resistance between the voltage sensing leads, resulting in an offset voltage on top of the output signal. Since this additional resistance is temperature dependent, the offset voltage varies with probe temperature. As the probe is heated by Joule heating, its temperature varies with probe-sample distance. This distance is slightly modulated due to topography of the sample while scanning, resulting in the observed strong topographic cross-talk. This work is a team effort by Edin Saraijlic, Martin Siekman and myself. My contribution is the theoretical model, the experiments and their analysis. The scanning Hall probes were fabricated by Edin Sarajlic. Martin Siekman assisted in construction of the measurement setup.

A low-noise measurement system for scanning thermal microscopy resistive nanoprobes based on a transformer ratio-arm bridge

“…A sensing resistor, made of conducting platinum nanowires, is placed in a pyramidal pit. It is isolated by a thin layer of silicon, oxidated silicon, and a silicon-rich nitride layer [17].…”

Advanced micromachining schemes for scanning probe tips

“…Using this method, tip structures consisting of molded pyramidal wire frames have been developed [46,47]. These wire frames have been used as SPM sensors for thermal and magnetic measurements [32,48,49]. Using the same method, but a different approach, pyramidal tips have been developed with small nanometer scale apertures at the apex of the tip and at the sides of the tip [50,51].…”