Scanning probe microscopic study to detect local electron field emission sites in ultrananocrystalline diamond films

Abstract

A detailed investigation of local electron field emission (EFE) from a set of pristine and metal (Pt, Ag) ion doped ultrananocrystaline diamond (UNCD) films was reported. In the present work, by using scanning probe microscopy (SPM) based techniques and metal ion doped UNCD films as model materials, the local EFE sites were mapped in nanometer scale. Various SPM based techniques such as energy dissipation mapping in dynamic scanning tunneling microscopy (D-STM) mode, atomic force microscopy (AFM) based peak force-controlled tunneling atomic force microscopy (PF-TUNA) and current imaging tunneling spectroscopy (CITS) in scanning tunneling spectroscopy mode were employed to directly detect the local EFE sites in pristine and doped UNCD materials. The D-STM based energy dissipation mapping and I-V measurements illustrated the presence of electron emitting grain boundaries (Gb, 1-2 nm) and non-emitting grains (G, similar to 5 nm) on doped UNCD surface. Further, on the context of the local grain boundary EFE mechanism, STM based spectroscopic results i.e. dissipation mapping and CITS measurements, agreed well with the AFM based PF-TUNA measurements. Moreover, these SPM based spectroscopic techniques can be promptly used to understand the conducting/non-conducting nature of thin film materials in nano or even atomic scale.