Millikelvin scanned probe for measurement of nanostructures

We demonstrate a scanning force microscope, based upon a quartz tuning fork, that operates below 100 mK and in magnetic fields up to 6 T. The microscope has a conducting tip for electrical probing of nanostructures of interest, and it incorporates a low noise cryogenic amplifier to measure both the vibrations of the tuning fork and the electrical signals from the nanostructures. At millikelvin temperatures, the imaging resolution is below 1 mum in a 22 mumx22 mum range, and a coarse motion provides translations of a few mm. This scanned probe is useful for high bandwidth measurement of many high impedance nanostructures on a single sample. We show data locating a single electron transistor within an array and measure its Coulomb blockade with a sensitivity of 2.6x10(-5) e/rootHz. (C) 2004 American Institute of Physics.