Charge Transport and Chemical Processes at Interfaces Studied by Advanced Photoelectron Spectroscopy

Processes taking place at interfaces are of general interest and, not surprisingly, drive researchers in a variety of scientific and applicative fields to use surface sensitive techniques, following a key requirement as of the depth sensitivity of the technique. Naturally, depending on the interface(s) of interest, the technique’s depth sensitivity dictates its applicability. In this respect, X-ray photoelectron spectroscopy (XPS) is a popular example, proposing considerable reliability in the quantitative analysis of chemical compositions, with exclusive restriction to the top few nanometers, 0.1-15 nm, of a solid surface. Remarkably, subject to slight modifications only, the XPS instrumentation can be upgraded to also provide unique electrical information, together with the chemical data. This combination opens a whole new dimension in the sensing capabilities of processes occurring at solid surfaces and interfaces. A technique named chemically resolved electrical measurements (CREM) focuses on the development of these capabilities.[1-4] Already demonstrated on a variety of systems, CREM proposes unique sensitivities by a top-contact-free sensor and, combined with real-time chemical information, it offers an important advantages over standard electrical tools. In this talk I will focus on the study of electric and optoelectronic processes in heterostructures and self-assembled-monolayers (SAMs) in particular. Charge transport processes across heterojunctions consisting of organic spacers between inorganic particles will be described, emphasizing the inseparable role of chemical and electrical characteristics at the active domain.