Noise in STM due to atoms moving in the tunneling space

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Abstract
A theory of electron tunneling through an adiabatically time-dependent potential barrier is applied to describe fluctuations of the scanning-tunneling-microscope current, induced by the motion of atoms in the tunneling gap. We show that atoms of a gas intervening between the tip and the sample introduce a noise small compared to the shot and thermal-electron noises. On the contrary, the noise induced by the movement of adsorbed atoms can be large enough to be observed. Simple formulas for the average current and temporal correlation functions of the current are offered to treat data on surface diffusion.