UC Santa Cruz

Semiconductors are an integral part of modern society, enabling numerous technologies such as transistors, microchips, detectors, solar cells, and LEDs. Semiconductor electronic properties are sensitive to microstructure which enables a high level of control over these properties and an ability to engineer them for applications. The development of these applications requires precise control of purity and impurity of semiconductor elements achieved through high temperature, high energy processes which produce large amounts of toxic waste.

Colloidal (suspended in solution) semiconductor quantum dots (QDs) have the potential to replace their bulk counterparts by eliminating these high temperature, high energy processes to produce large-area, flexible, and solution-processed thin film arrays.1–3 Just like bulk counterparts, QDs’ properties can be enhanced through doping with impurity atoms. Many of the challenges facing functional QD systems are tied to disorder; therefore, careful characterization of doped QDs is critical to fulfilling the potential of these materials as active materials for electronic applications.

This thesis reports studies of three elemental species incorporated into crystalline colloidal germanium (Ge) QDs: tin (Sn), antimony (Sb) and bismuth (Bi) along with the effects of ligand exchange. Extended X-Ray Absorption Fine Structure (EXAFS) and various other advanced characterization methods were used to decipher disorder, bonding modalities and lattice incorporation of dopants under processing and chemical environment conditions. All dopants studied were found to reside on the host lattice either on the surface of QDs or in the interior in disordered states.