Direct wiring of carbon nanotubes for integration in nanoelectromechanical systems

The authors present the use of electron beam induced deposition (EBID) for direct wiring of carbon nanotubes (CNTs). Since this technique is a maskless, direct patterning method, EBID is applicable to suspended nanotubes potentially integrated in predefined nanoelectromechanical systems (NEMS). The authors developed a process including CNT adsorption from solution on prepatterned planar samples, evaluation and localization of CNTs by scanning force microscopy, preparation of GDSII layouts, and contacting CNTs by EBID of tungsten. EBID was performed in an integrated e-beam lithography and nanoengineering workstation using tungsten hexacarbonyl as precursor. With well controlled exposure conditions, a resistivity on the order of 10−2Ωcm has been achieved. Moreover, electrical measurements on CNTs contacted by EBID tungsten leads clearly show transistorlike behavior. First tests on EBID metal lead integration on alumina NEMS structures were carried out. Thus EBID can enable a top metallization of CNTs on suspended NEMS structures, which should enhance also the mechanical stability between the lead and the CNT.