Internal photoemission of electrons from 2 dimensional semiconductor heterostructures

The work will be focused on development of characterization methodology capable of quantifying energy band offsets and electrostatic potential profiles in heterogeneous semiconductor and metal electrodes with focus on 2-dimensional materials. This experimental technique is based on the phenomenon of internal electron photoemission (IPE) into an insulating layer which enables determination of both the electron band edge energies in the photoemitting hetero-junction and the orientation of electric field at its interface with insulator. Interfaces in heterostructures relevant to nano-electronic devices including 2D semiconductors, graphene, and metals with wide range of work-function values will be addressed. In particular, the possibility of detecting electrostatic potential perturbation by individual interface charges, e.g., dopants in 2-D material layer or at its interface, will be explored. Since the atomically-thin 2D films are commonly analyzed upon transfer (or synthesis) on top of the insulating substrate to enable optical observation and to avoid electrical shunting, this measurement configuration is directly relevant to the analysis of electron transport across the stack of 2D materials or in the metal/2D contacts which makes possible to explore the limits of interface barrier engineering aiming at realization of functional electron devices. Furthermore, this kind of characterization would be of much interest if considering the contamination related “patches” and the inter-domain/inter-grain boundaries in the few-layer 2D semiconductor or graphene sheets transferred on top of an insulator.