In tetrahedral amorphous carbon (ta-C) swift heavy ions create conducting tracks of about 8 nm in diameter. To apply these nanowires and implement them into nanodevices, they have to be contacted and gated. In the present work, we demonstrate the fabrication of conducting vertical nanostructures in ta-C together with self-aligned gate electrodes. A multilayer assembly is irradiated with GeV heavy ions and subsequently exposed to several selective etching processes. The samples consist of a Si wafer as substrate covered by a thin ta-C layer. On top is deposited a SiNx film for insulation, a Cr layer as electrode, and finally a polycarbonate film as ion track template. Chemical track etching opens nanochannels in the polymer which are self-aligned with the conducting tracks in ta-C because they are produced by the same ions. Through the pores in the polymer template, the Cr and SiNx layers are opened by ion beam sputtering and plasma etching, respectively. The resulting structure consists of nanowires embedded in the insulating carbon matrix with a built in gate electrode and has potential application as gated field emission cathode.
Ion track lithography is well established and is based on heavy ions of several hundred MeV energy passing through a polymer film and thereby changing the material properties along the trajectory of each ion. By selective chemical track etching, small channels (down to 20–30nm diameter) are formed which can be filled with another material or can serve as mask for further etching steps. Another application uses unetched ion tracks directly for nanostructuring. The authors’ investigations showed that graphitic nanowires are formed along ion tracks in insulating diamondlike carbon films. The diameter of these conducing filaments is in the order of 8nm. In the present article the authors describe a combination of these two possibilities to create several nanodevices such as cold field emission devices, quantum-based electronics, or interconnections in very-large-scale integrated circuits. Since the lithographic structure and the conducting filament are produced by the same ion track, the two parts of the device are self-aligned and need no further adjustment. Furthermore, it should be mentioned that the structure is created by a single ion and therefore is automatically very small in diameter and does not require special beam focusing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.