The characterization of defect-induced deep levels and manipulation of physical properties in low-dimensional semiconductors
Speaker Dr. Penghong Ci
University of California, Berkeley
About the Speaker
Dr. Penghong Ci obtained his Ph.D. degree from the University of California, Berkeley, under the supervision of Prof. Junqiao Wu. His research interests are mainly focused on novel physical properties of semiconductors with reduced dimensions, such as optoelectronic, thermal, and mechanical properties, and defect-induced effects at the nanoscale.
Properties of semiconductors are largely defined by crystal imperfections including native defects. Van der Waals (vdW) semiconductors, a newly emerged class of materials, are no exception: defects exist even in the purest materials and strongly affect their electrical, optical, magnetic, catalytic, and sensing properties. This talk will demonstrate deep level transient spectroscopy, a high-frequency capacitance transient thermal scanning method, to characterize electronic structures of defect-induced deep traps inside the bandgap of vdW semiconductors. This method successfully identified deep traps attributed to native chalcogen vacancies and discovered a metastable DX center featuring persistent photoconductivity above 400K. In addition to defects, strain and isotopic effect can also effectively manipulate physical properties in semiconductors. Hence, the second part of the talk covers the band-structure engineering via diamond anvil cell to quantify the interlayer cohesive force in vdW semiconductors and the isotope engineering to enhance the thermal conductivity in silicon nanowires.
All are welcome！