Comprehensive characterization of nanoscale material interfaces remains one challenging research direction in nanoscience and nanotechnology. Advancements in the science of nanocrystal (NC) synthesis has lead to the design and synthesis of single- and multi-component nanostructures that consist of combinations of semiconducting, metallic, oxide, magnetic, or other material components. However, material interfaces often govern the physical properties of the overall structure. The ability to directly characterize individual components of a nanoheterostructure will greatly aid our understanding of design parameters for complex functional nanomaterials and device applications. In this presentation, I will discuss scanning Kelvin probe microscopy (SKPM) in the study of electrostatic potential distribution across single, colloidal heterostructured nanorods (NRs).1 In the heterostructured CdS/PbS nanorod, the PbS component (< 10 nm) is expected to show strong quantum confinement and thereby display size-dependent electrical properties potentially resulting in a the formation of a tunable built-in potential within the nanoheterostructure. We measured a sharp, electrostatic potential difference across this material interface. We used a high frequency bimodal SKPM method with a potential resolution of *10 mV and a spatial resolution of ~10 nm and measured potential differences of ~150 mV in CdS/PbS NRs. We attribute this potential contrast to the built-in potential across the CdS/PbS and discuss details of the spatial distribution of charges within each component. This SKPM technique was also applied to cross-sections of active quantum dot based (PbS) solar cells and the electrostatic potential distribution across all the layers of the device was directly measured. The measurements gave insight into the operation mechanism of these solar cells and will be a useful tool in further development of advanced device architectures for solar power conversion.2
(1) Nanayakkara, Cohen, Jiang, Romero, Maturova, Al-Jassim, van de Lagemaat, Rosenwaks and Luther, Nano Lett., 13(3), 1278, 2013.
(2) Ihly, Nanayakkara, Gao, Zhang, Li, Nemmeth, Gibbs, Law and Luther, In preparation.
For further information please contact Nikolai Zhitenev, 301-975-6039, nikolai.zhitenev [at] nist.gov (nikolai[dot]zhitenev[at]nist[dot]gov)