Quantum Contact

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The present work clarified the quantum mechanical phenomena at the quantum nano-contact, such as quantized conductance, by using STM (scanning tunneling microscope) installed in the specimen position of the UHV (ultra-high-vacuum) transmission electron microscope (TEM). A new AFM (atomic force microscope) combined UHV-TEM was also developed to study atomic forces acting on the nano-contact or on the nanowire that span between the AFM cantilever and the substrate.Some noticeable results are obtained as follows :(1)The conductance of the helical multi-shell (HMS) gold nanowire with magic number 7 was measured by using STM-TEM, to conclude that the integer quantization of the conductance is broken because of the symmetry breaking at the contact area of the electrode and the HMS. (2)Single wall nanotube of gold (and platinum) was synthesized at 150K during the thinning of the gold film by electron beam. (3)Copper nanowires display half integer quantum conductance, but they allow no change under application of magnetic filed up to 100mT. (4)Non-linear conductance was recognized for gold, copper, silver, and platinum nano-contacts. The conductance increased positively for increasing the bias voltage. (5)The breaking of the conductance quantization was investigated by making a long silver nanowire (rope), which grew from the AgI crystalline surface while the tip electrode approached above the AgI surface. (5)We developed Cs (spherical aberration) corrected lens for the analysis of elements at nano-contacts to study electron scattering at atoms in the nano-contact.