Composition tuning of rectifying polarity of colloidal CdS_1−xSe_x nanocrystal-based devices

CdS_1–xSe_x colloidal nanocrystals (NCs) were synthesized by colloidal chemistry route. Both lattice parameters and band structure were modulated by tuning the content of Se. As the Se content increases, the peak of UV–Visible absorbance spectrum of CdS_1−xSe_x shifts toward longer wavelength direction, indicating the reduction of band gap. Devices with Au/CdS_1−xSe_x NCs/Au structures have been fabricated by assembling the obtained CdS_1−xSe_x NCs into Au microelectrodes via dielectrophoresis method. It is found that the rectifying polarities of the devices are strongly dependent on the content of Se. With the increasing Se content, the rectification polarity changes from backward to forward. This polarity tuning could be caused by the change of the relative height of the Fermi levels between CdS_1−xSe_x and Au. The Se-content-dependent rectifying behavior may offer us an opportunity to design novel logical structure in NC-based nanoelectronics