Electrical Characteristics of Metal Contacts to Carbon Nanowalls

The electrical characteristics of metal contacts to vertically-aligned nanographite structures, the so-called carbon nanowalls (CNWs), are examined using nickel as the electrode material. The total resistance between a pair of electrodes on CNWs is regarded as the sum of the serial resistance of CNWs and two metal-CNWs contacts to measure the contact resistance and specific contact resistivity by the transmission line method and transfer line method, respectively. The contact resistance and resistivity are around 2.8 omega and 0.1 omega cm(2), respectively, at room temperature and decrease gently to 2.4 omega and 0.06 omega cm(2), respectively, when the temperature is increased up to 300 degrees C. The apparent activation energy corresponding to the conduction barrier at the contact is in the range of 10(-3) eV to 10(-2) eV, which is comparable with that for the sheet resistance of CNWs. The contact resistance occupies a large portion of the total resistance between a pair of electrodes even at high temperatures, thus affecting electrical signal measurement in electronic and electrochemical device applications.