title: Internal field switching in CdSe quantum dot films on Si.
abstract: If a thin film (tens of nm) of CdSe quantum dots (4 nm diameter) is deposited by chemical bath deposition onto various substrates, the films, although essentially intrinsic, behave as if they were n-type with respect to charge separation. However, films deposited under certain deposition conditions on Si (both n(+)- and p(+)-type) behave as if they were p-type. In this case, we show that it is possible to switch this p-type photoresponse by either light illumination intensity or injection of electrons from an external filament. Using both surface photovoltage spectroscopy and a novel adaptation of X-ray photoelectron spectroscopy, we show how this behavior results from a Cd(OH)(2) layer adsorbed at the Si surface at the beginning of the deposition. This response is explained by a competition between a high concentration of relatively shallow hole traps in the CdSe and a lower concentration of deeper electron traps in the Cd(OH)(2). The relative occupancies of these traps determine the fields in the film and their response to external parameters.
authors.affiliation: Department of Materials and Interfaces, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Shaibal K
authors.initials: SK
authors.lastname: Sarkar
authors.forename: Hagai
authors.initials: H
authors.lastname: Cohen
authors.forename: Gary
authors.initials: G
authors.lastname: Hodes
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D008567:Membranes, Artificial; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D019187:Cadmium Compounds; D008567:Membranes, Artificial; D018036:Selenium Compounds; C058667:cadmium selenide; D012825:Silicon