Professor and Chair Department of Physics
Rockefeller Building 220
B.A., Middlebury College (1975)
Ph.D., Massachusetts Institute of Technology (1982)
Experimental Condensed Matter Physics
Changing the dimensionality of a physical system has a profound influence on all of the interactions that occur in any system, through changing the phase space of the system and through modifying the interactions between particles. Condensed matter physics abounds with intriguing and important examples of phenomena that occur when the motion of particles is restricted. Phase diagrams change drastically, and new phenomena-chaos, the Quantum Hall Effects, to name two examples-arise.
My earlier research involved work in quantum wells and superlattices, where electrons and holes are restricted to move in planes created by near- perfect layer- by-layer control of the composition of alternating low-band- gap and higher-band-gap semiconductors, and the creation of “quantum wires” and “quantum dots” by using nanoscopic-size strain patterns. One of the primary foci of our current research, in collaboration with colleagues in Chemical Engineering and Macromolecular Science, aims to produce nanometer- size semiconductor wires and dots by using molecular templates as masks for electrodeposition. Here, the idea is to deposit a regular array of molecules-ours are ring structures, with inner diameters as small as 5 nanometers-onto a substrate, and then electrodeposit semiconductor nanocrystals within the rings to form a hexagonal ring. While the properties of such small crystals are of intrinsic interest, potential device applications-for example, as two-dimensional photonic crystals for x- rays-are also of great interest to our group.
An ancillary interest is our work on understanding how to make good electrodeposited semiconductor material. From a device physics point of view, very little work has been done to date in this area. Yet, if we could grow device-quality material, we could take advantage of electrodeposition to design geometries of structures that cannot be made easily-or at all-by starting with a single crystal. For example, we could make integrated circuits from devices arranged in three-dimensional arrays, instead of in the two-dimensional arrays that is a current design limitation.
A third focus of our group, also in collaboration with colleagues in Chemical Engineering, is low-pressure growth of GaN and InN. These materials are used to make blue and ultraviolet lasers and light emitting devices, and electronic devices that can be used in harsh and high temperature environments.
“High Efficiency Green Light-Emitting Diodes based on InGaN-ZnGeN2 Type-II Quantum Wells”, Lu Han, Kathleen Kash and Hongping Zhao, Proc. SPIE. 9003 90030W-1 (2014). DOI: 10.1117/12.2038756
“Synthesis, lattice structure and band gap of ZnSnN2”, Paul Quayle, Keliang He, Jie Shan, Kathleen Kash, MRS Communications (2013).http://dx.doi.org/10.1557/mrc.2013.19.
“ZnGeN2: The Effects of Growth Conditions on Morphology, Ordering and Optical Properties”, E. Blanton, P. Zhao, K. He, J. Shan, H. Zhao and K. Kash, Online Proceedings of the 2012 Fall Meeting of the MRS Society, Photovoltaic Technologies—Materials, Devices and Systems E19.93 (2013).
“Size-dependent Electron Chemical Potential: Effect on Particle Charging”, John C. Angus, Isaac Greber, Kathleen Kash, Journal of Electrostatics 71, 1055-1060 (2013). http://dx.doi.org/10.1016/j.elstat.2013.10.006.
“Thermodynamic Properties of Gallium Nitride”, Timothy J. Peshek, John C. Angus, Kathleen Kash, J. Crystal Growth 322, 114 (2011).http://dx.doi.org/10.1016/j.crysgro.2011.09.040
“Electrochemical Charge Transfer to Diamond and Other Materials”, Vidhya Chakrapani, John C. Angus, Kathleen Kash, Alfred B. Anderson, Sharvil Desai and Gamini U. Sumanasekeran, Proceedings of Symposium J of the 2009 Fall Meeting of the Materials Research Society (Boston, MA, November 30-December 4, 2009); Vol 1203, 1203-J07-01. http://dx.doi.org/10.1557/PROC-1203-J07-01
“Vibrational modes in ZnGeN2: Raman study and theory”, Timothy J. Peshek, Tula Ram Paudel, Kathleen Kash and Walter R.L. Lambrecht, Phys. Rev. B 77, 235213 (2008). http://link.aps.org/abstract/PRB/v77/e235213
“Experimental Investigation of the Enthalpy, Entropy and Free Energy of Formation of GaN”, Timothy J. Peshek, John C. Angus, and Kathleen Kash, Journal of Crystal Growth 311, 185 (2008). http://dx.doi.org/10.1016/j.jcrysgro.2008.09.203
“Synthesis and Characterization of ZnGeN2 grown from Elemental Zn and Ge Sources”, K. Du, C. Bekele, C.C. Hayman, J.C. Angus, P. Pirouz, K. Kash, J. Crystal Growth 310, 1065 (2008). http://dx.doi.org/10.1016/j.jcrysgro.2007.12.042
“Optical non-linearity in GaAs quantum dots”, A.S. Plaut, K. Kash, B.P. Van der Gaag, A.S. Gozdz, J.P. Harbison and L.T. Florez, J. Appl. Phys. 101, 106107 (2007). http://dx.doi.org/+10.1063/1.2655626