Bias voltage dependent shift of the atomic-scale structure of the Ge(111)-(2$\times$1) reconstructed surface measured by low temperature scanning tunneling microscopy

We present the results of our low temperature scanning tunneling microscopy (STM) investigations of the clean Ge(111) surface. We observe bias dependent shifts of the atomic-scale structure caused by the $(2\times1)$ reconstruction of the Ge(111) surface. A detailed comparison of experimental data with theoretical predictions based on the $\pi$-bonded chain model allows us to conclude that inelastic tip-sample interaction plays a significant role in STM imaging of the Ge(111)-($2\times1$) reconstructed surface.