document: The length effect is always important in nanodevices. So we investigate the length dependence of electronic transport properties in M3 by increasing the number of carbon unit cells in the scattering region. Here we present the transport results when the numbers of carbon unit cells in the scattering region are 10 and 12, which are called M4 and M5, respectively. The current–voltage characteristics shown in Fig. 8. We can see that the large rectifying ratio still can be observed irrespective of the length of heterojunctions. This is due to the fact that the electronic transport properties for M3 are mainly determined by the parity of the π and π⁎ subbands of left and right electrodes. Thees results indicate that the lengths of the two parts in the scattering regions have no affects on the qualitative charge transport in M3.
extractive_keyphrases: carbon unit cells current–voltage characteristics electronic transport properties large rectifying ratio length effect nanodevices qualitative charge transport π and π⁎ subbands
abstractive_keyphrases: increasing the number of carbon unit cells length dependence of electronic transport properties