Low Dimensional Materials for Infrared Imaging

The current state-of-the-art technology for infrared (IR) imaging primarily relies on HgCdTe detectors. Low-dimensional materials offer an alternative with lower operational and production costs. Additionally, the band gap can be varied with the size in colloidal quantum dots (CQDs) and with strain, number of layers, and electric field in 2D materials. In this thesis, I explore CQD and 2D materials for IR sensing. Carrier extraction is a serious issue with CQD-based devices. The electronic energy levels of the ligands used for photoexcited carrier transport are not aligned with those of the CQDs creating an energy level mismatch that hinders an efficient charge transport. I explored two methods—the shape of the CQD and quadrupole moment in the ligand— for tuning the band edges of the CQDs without altering the energy gap. Computationally, I studied the band gap variation and the band edge positions with the CQD shape for a given size. Similarly, I show that the quadrupole in ligands attached to either end of a Sn-CQD will change the potential inside the CQD and thus alter the position of the conduction and valence band edges. We present a systematic method and propose specific ligands to achieve good alignment with either the conduction or the valence band edge. The band gap of bilayer 2D materials has been demonstrated to vary considerably under an applied electric field. However, materials such as MoS2 suffer from low photon absorption. To address this limitation, I focused on selecting materials with small interlayer distances and then used various stacking orientations to increase absorption considerably. Furthermore, I specifically applied this approach to hexagonal BAs and hexagonal BP to evaluate their use for possible hyperspectral sensing. My work addresses and presents theoretical solutions to significant bottlenecks in achieving low-dimensional infrared detectors.