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This paper reports thermal nanotopography sensing using a heated atomic force microscope cantilever with a sensitivity as high as 4.68 mV/nm, which is two orders of magnitude higher than previously published results for heated cantilevers. The sensitivity improvement arises from closed-loop control of cantilever temperature during the topography sensing. The cantilever temperature is controlled by maintaining constant electrical resistance, current, power, or voltage across either the entire electrical circuit or individual components of the circuit. We develop a model that links the cantilever heat flow and temperature-dependent cantilever properties to the circuit behavior in order to predict and then optimize the cantilever topography sensitivity. Topography measurements on a 100 nm tall silicon gratings how cantilever sensitivity ranging 0.047 to 4.68 mV/nm, depending on the control scheme. The application of closed loop control yields a topography sensitivity that is 100 times increased over previously published work on heated cantilevers.
Date of Publication: Nov. 2011