An atomic force microscope which operated under ultra-high vacuum was constructed, and was used to image the cleaved (100) surface. As a result, atomically resolved images of atomic defects which penetrated the surface were obtained for the first time. This suggested that the cleaved (100) surface was imaged under conditions of monatomic or small-cluster tip-sample interaction.

M.Ohta, T.Konishi, Y.Sugawara, S.Morita, M.Suzuki, Y.Enomoto: Japanese Journal of Applied Physics 1, 1993, 32[6B], 2980-2