Tuning the electrical conductance of oligo(phenylene-ethynylene) derivatives-PbS quantum-dot bilayers†
Abstract
Transcribing quantum effects from lower to higher dimensions is a complex yet intriguing area of research. Coulomb blockade (CB), a fundamental quantum phenomenon, is commonly observed in low-dimensional materials like quantum dots (QDs) at extremely low temperatures. This behavior shows promise for the development of high-performance memory and thermoelectric devices. However, when transitioning to larger dimensions, such as arrays at room temperature, the CB effect is hindered by thermal fluctuations and structural inconsistencies. This study presents a thorough examination of electron transport through PbS QDs using a blend of experimental and theoretical methods. By creating a sizable parallel array of QDs immobilized on self-assembled monolayers (SAMs) and employing single-layer graphene (SLG) as the top electrode, we were able to maintain the CB effect at room temperature on a device scale. Additionally, a device with a top gate structure was designed to precisely regulate the energetic position of quantum states in relation to the Fermi level of the electrode. By utilizing ultra-small QDs (typically 2 nm in size), we successfully sustained the CB effect at room temperature. To investigate the impact of structural uncertainties, we combined density-functional theory and quantum transport theory to comprehensively analyze the quantum transport properties of QDs bound with SAMs across various facets. This enabled us to establish a correlation between these structural variations and the experimental data distribution.
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