Molybdenum oxide on carbon nanotube: Doping stability and correlation with work function

Abstract

Carbon nanotubes (CNTs) have great potential for future high-performance and energy-efficient transistor technology. To realize this potential, methods to dope the CNTs need to be developed to achieve low parasitic resistance of the transistor. Two key issues present themselves: (a) understanding the doping mechanism of the various methods and (b) stability of the doping method. For instance, although studies on molybdenum oxide (MoOx) demonstrate its ability to heavily dope nanomaterials, the interaction between MoOx and the CNT is unclear. Here, we observe an unstable effect of MoOx on the CNT and demonstrate dielectric passivation as a means to preserve the doping strength. The semiconducting CNTs exhibit greater than 103× reduction in resistance after stably doped with MoOx. By exploiting the instability of MoOx, we delve deeper into clarifying the doping mechanism. The relationship between the time-dependent material property of MoOx and the change in the electrical measurements of CNT devices is investigated to study the role of work function in doping the CNTs. We conclude that the doping mechanism of MoOx on the CNT is due to bandgap modulation by charge transfer, which occurs due to the difference in work function between MoOx and the CNT.