Synthesis Methods of Quantum Dots and Applications

This chapter discusses the synthesis processes of quantum dots (QDs) using both top-down and bottom-up approaches. Top-down synthesis involves thinning down a bulk semiconductor material using techniques such as electron beam lithography, reactive-ion etching (RIE), and wet chemical etching. These methods allow for precise control over the size, shape, and arrangement of QDs but may introduce impurities and structural imperfections. Etching processes, including RIE, are well-established techniques used in the top-down synthesis of QDs. Focused ion beam (FIB) techniques provide high lateral precision for QD fabrication but are slow and can cause surface damage. Electron beam lithography followed by etching is another method used to achieve QD patterns with flexibility and precise separation. Bottom-up synthesis processes involve self-assembly techniques, including wet chemical and vapor-phase methods. Wet chemical methods, such as sol–gel and microemulsion, offer control over QD size, shape, and composition by adjusting various parameters. However, they may have limitations such as broad size distribution, defects, and lower yields. Vapor-phase methods, including molecular beam epitaxy (MBE), physical vapor deposition (PVD), and chemical vapor deposition (CVD), involve the growth of nanostructures through vapor-phase deposition. These methods allow for the self-assembly of QDs on a substrate without specific patterning, and the growth modes observed depend on factors such as interfacial/surface energies and lattice mismatch. Overall, this chapter provides an overview of various techniques used in synthesizing QDs, highlighting their advantages, limitations, and the control they offer over the size, shape, and composition of the QDs. QDs have found applications in white light-emitting diodes (LEDs), solar cells, quantum computers, and quantum dot cellular automata (QCA).