USACM Nanotechnology TTA Seminar - Stephanie Law

October 6, 2026 Stephanie Law, Pennsylvania State University Quantum Dot Synthesis by Molecular Beam Epitaxy: A Tale of Two Materials Quantum dots (QDs) are semiconductors that are confined in three dimensions, leading to quantization of energy levels which can be leveraged to make QD light emitting diodes, lasers, and single photon emitters, among other devices. QDs have long been grown using molecular beam epitaxy (MBE) with significant success. However, control over the QD size, shape, spacing, and location has proven challenging. In this talk, I will describe our efforts to synthesize QDs using 2D materials and 3D materials for two different applications. One of the major challenges facing QDs used for single photon emission is the need to create identical QDs and precisely place them within an optical device. One way to address these problems is to use selective area epitaxy to control the nucleation and growth of QDs. We have been exploring selective area epitaxy of QDs of the van der Waals material Bi2Se3 which is predicted to emit in the telecom band. I will show our results in selective area van der Waals epitaxy (SAVE) of Bi2Se3 QDs where we can synthesize QDs with 100% selectivity with sizes down to 20 nm, meaning that the Bi2Se3 grows only on the substrate and not on the mask within a particular growth window. Although QDs have been extremely successful as light emitters in the visible and short wave infrared spectral ranges, there has been relatively little progress in the use of QDs as emitters in the mid-wave and long-wave infrared (MWIR and LWIR). III-V-based QDs made from In(Ga)Sb in an InAs matrix have previously shown promise as MWIR and LWIR emitters, but it has been difficult to reproducibly synthesize them. I will discuss our latest work using machine learning techniques to design experiments and understand the synthesis-structure-property relationships in In(Ga)Sb QDs.