CONDUCTIVITY AND MAGNETOCONDUCTIVITY OF POLYANILINE FILMS IMPLANTED WITH AR-INSULATOR-TRANSITION( AND GA+ IONS NEAR THE CRITICAL REGIME OF THE METAL)

The dc conductivity (down to 1.5 K) and magnetoconductivity (up to 8 T ) of polyaniline films synthesized in the emeraldine oxidation state a nd implanted with Ar+ ions at 30 keV and Ga+ ions at 62 keV with doses between 3 x 10(15) and 2.3 x 10(17) ions cm(-2) are reported. The dou ble ion irradiation of polyaniline films decreases the room temperatur e sheet resistivity from 10(15) Ohm cm(-2) down to 10(3 )Ohm cm(-2) an d results in a maximum conductivity of 150 S cm(-1 )at the highest irr adiation level. As the irradiation dose increases, the temperature dep endence of the conductivity sigma (T) changes from activated transport to close to critical regime behaviour with a minimum characteristic r esistivity ratio rho(r) = rho (1.6 K)/rho(300 K) of about 4.4. For the most highly irradiated samples sigma (T) similar to T-0.3, which is c haracteristic of the critical regime near the metal-insulator transiti on. Magnetoconductivity of these Ar+ and Ga+ ion irradiated polyanilin e films in the critical regime below 4.2 K is negative (i.e. positive magnetoresistance). The magnetoconductivity increases as the temperatu re decreases and is well described by H-2 and H-1/2 dependences at low and high magnetic fields, respectively, which is characteristic of th e dominant influence of electron-electron interactions on the low temp erature conductivity.