Molecular Electronics by Chemical Modification of Semiconductor Surfaces

摘要

Inserting molecular monolayers within metal / semiconductor interfacesprovides one of the most powerful expressions of how minute chemicalmodifications can affect electronic devices. This topic also has directimportance for technology as it can help improve the efficiency of a variety ofelectronic devices such as solar cells, LEDs, sensors and possible futurebioelectronic devices, which are based mostly on non-classical semiconductingmaterials (section 1). The review covers the main aspects of using chemistry to- control alignment of energy levels at interfaces (section 2): - passivateinterface states (section 3), - insert molecular dipoles at interfaces (section4), - induce charge rearrangement at and around interfaces (section 5). Aftersetting the stage, we consider the unique current-voltage characteristics thatresult from transport across metal / molecular monolayer / semiconductorinterfaces. Here we focus on the interplay between the monolayer as tunnelingbarrier on the one hand, and the electrostatic barrier within thesemiconductor, due to its space-charge region (section 6), on the other hand,as well as how different monolayer chemistries control each of the thesebarriers. Section 7 provides practical tools to experimentally identify thesetwo barriers, and distinguish between them, after which section 8 concludes thestory with a summary and a view to the future. While this review is concernedwith hybrid semiconductor / molecular effects (see Refs. 1,2 for earlierreviews on this topic), issues related to formation of monolayers and contacts,as well as charge transport that is solely dominated by molecules, have beenreviewed elsewhere[3-6], including by us recently[7].