  The effect of finite deformed length is demonstrated by squashing an armchair
(10,10) single-walled carbon nanotube with two finite tips. Only when the
deformed length is long enough, an effectual metal-semiconductor-metal
heterojunction can be formed in the metallic tube. The effect of finite
deformed length is explained by the quantum tunnelling effect. Furthermore,
some conceptual designs of nanoscale devices are proposed from the
metal-semiconductor-metal heterojunction.
