Controlling probe-sample separation with aerodynamic floating

We have recently developed a noncontact technique capable of detecting micr oscopic variations in the surface potential of charged dielectric films. Th e technique is based on measuring the charge induced on a small capacitive probe held at a constant distance from a charged sample surface. Distance c ontrol is achieved by aerodynamic floating, which is an inexpensive and sim ple passive feedback system capable of maintaining a constant probe-sample separation despite minor variations in sample morphology. We have used the technique to detect the presence of microscopic electrostatic defects in or ganic photoreceptors, such as charge deficient spots, which are responsible for image degradation in xerographic copiers and printers. However, aerody namic floating could be implemented in other applications requiring accurat e control over probe-sample separation. (C) 2001 American Institute of Phys ics.