Photo emission spectroscopy for Ag-TCNQ (TCNQ = tetracyanoquinodimethane) nanowires

The electrical conductivity of many TCNQ charge-transfer complexes generated much interest in the subject of field emission displays (FEDs). Ag-TCNQ nanowires were prepared using a vacuum vapor-transport reaction method at a lower temperature, showing good field emission properties in our previous work. In this work, XPS test was carried out using the VG Scienctific suface analysis instrument (XR5 type) to study the charge transfer. Low energy resolution spectra were obtained by illuminating the sample with standard Al Kα radiation( hv =1486. 6 eV ). UPS test was done on the instrument of VG ADES-400 type, with illumination of He I line( hv = 21. 2 eV ). Results from XPS test for those nanowires showed that the charge transfer between the electron donor and acceptor was not complete in accord with the Raman analysis. The work function of the nanowires was measured by the ultraviolet photoemission spectroscopy (UPS) with the threshold energy method. UPS analysis showed that the highest of state occupied is 0.78 eV below the Femi level and the work function is about 5. 45 eV, which is different from the effective work function of 1.77 eV estimated by the Fowler-Nordheim plot in this theory. The nanostructure of organic nanowires and the special electrical conductivity by the charge transfer process are attributed to the good field emission properly.