Fabrication and Evaluation of Electrical Properties of Poly (1,8-diaminonaphthalene) Based Schottky Diode

Poly (1,8-diaminonaphthalene) films as p-type semiconductors were easily synthesized potenitiostatically on the Au or indium-tin oxide vacuum deposited glass substrates. Optical transmissions of doped and dedoped films were measured within 250-1100 nm wavelength range and the corresponding optical band gaps were estimated to be 2.84 and 3.62 eV. The polymer was used for the construction of schottky barriers with In, Cu, and Ag metals. The current-voltage and capacitance-voltage characteristics of the diodes were studied to derive information on junction parameters. The electrical characteristics of the junctions at low range potential were analyzed based on the standard thermionic emission theory. The value of ideality factor (E) for In/polymer junction was found to be 9.93 which decreased to 5.23 and 6.30 for Cu and Ag electrodes, respectively. This can be attributed to the formation of complex between Cu and Ag during vacuum deposition of these two metals onto the polymer layer which reduces the thickness of oxide insulator interfacial layer. The capacitance-voltage characteristics of the diode were also studied and the built-in voltage (V(c)), the charge carrier concentration (N(s)), depletion width, and the work function of poly (1,8-DAN) were estimated. The value of 4.45 eV was obtained for polymer work function.