  A methodology to test the interlayer bonding strength of two-dimensional (2D)
surfaces and associated one (1D)- and two (2D)- dimensional surface defects
using scanning tunneling microscope tip-induced deformation, is demonstrated.
Surface elastic deformation characteristics of soft 2D monatomic sheets of
graphene and graphite in contrast to NbSe2 indicates related association with
the underlying local bonding configurations. Surface deformation of 2D
graphitic moire patterns reveal the inter-layer van der Waals strength varying
across its domains. These results help in the understanding of the comparable
interlayer bonding strength of 1D grain boundary as well as the grains.
Anomalous phenomena related to probing 2D materials at small gap distances as a
function of strain is discussed.
