Tip-sample distance feedback control in a scanning evanescent microwave probe for nonlinear dielectric imaging

We implemented tip-sample distance control in a scanning evanescent microwa ve probe for nonlinear dielectric microscopy. With the analytic expression of the tip-sample capacitance as a function of tip-sample distance, we can quantitatively regulate the tip-sample separation and independently measure the dielectric nonlinearity by application of an ac bias voltage. Simultan eous imaging of topography and ferroelectric domains has been demonstrated on periodically poled LiNbO3 single crystals. (C) 2000 American Institute o f Physics. [S0034-6748(00)05406-X].