Electrical conduction in amorphous titanium nitride films

Abstract

Charge transport measurements in disordered semiconductors and insulators have been of considerable interest because they can provide information regarding the electronic structure of these materials [1-3]. The study of direct current conduction in thin dielectric films is of importance in thin film applications. Exhaustive work has been done on electrical conduction phenomena in a variety of amorphous and crystalline dielectrics [4-6]. Titanium oxide and titanium nitride are also potential dielectrics with a high permittivity. Though there are more studies on the conduction mechanism of titanium oxide films [7-9] the number of studies on titanium nitride films is relatively less. Osadnik and Das [10] have studied the resistivity of chemically deposited titanium nitride films. In the present investigation, we report our observations on the conduction mechanisms in the case of ion plated titanium nitride films. Aluminium has been evaporated from a tungsten filament onto well cleaned glass substrates to form the base electrode for the capacitor. The titanium nitride layer was deposited by the ion plating method [11] by evaporating titanium powder (99.9%) from a conical basket type tungsten filament, in an atmosphere of nitrogen. The substrates were maintained at a temperature of 150 ° C. Aluminium was again evaporated to complete the MIM sandwich structure. The thickness of the dielectric layer has been measured using a multiple beam interferometer. The samples were well annealed before conducting the studies. The structure of the deposited films was found to be amorphous. The current due to d.c. fields under the condition of constant rate of rising applied voltage was measured with a field-effect transistor nanoammeter. The variation of the current with voltage at different temperatures is shown in Fig. 1. At very low applied voltages, the conduction process due to thermally excited carriers is ohmic. As the voltage is increased, the current rises nonlinearly. Fig. 2 shows the dependence of log/ on the