MRI: Development of a Combination High Resolution and Low Current Density Inverse Photoemission Spectrograph for Research and Eduction

University Of Delaware, Newark DE

Investigators

Abstract

Recently, tremendous advances have been achieved in the development of new materials such as highly correlated electron systems, nanoscale materials, organic semiconductors and promising species for molecular electronics. While photoelectron spectroscopy has played a central role in establishing key properties of these materials, there has been markedly less progress towards understanding the spectral function above EF. Inverse photoemission (IPE) spectroscopy is the natural choice for probing this energy range, but high current densities and low energy resolution limit its application to these interesting systems. The proposed instrument will greatly relieve these shortcomings and open to experimental scrutiny the spectral function above the Fermi level of these interesting materials. The information gained from this new instrument will enable intelligent design of candidate species for molecular electronics or organic semiconductor applications. Similarly it will test our current theoretical understanding of highly correlated electron systems by experimentally probing the energy and momentum dependence of the spectral function in a new regime. We will develop and construct the prototype for a new generation of inverse photoemission spectrographs that will serve the dual demands of modern materials science -- low current density and high energy resolution -- while maintaining high count rates. This objective will be achieved by a design principle that exploits the compatibility between a fast (f/5) normal incidence grating spectrograph and the spatially extended linear electron spot produced by either of two sources: a modified, high perveance electron gun, and a high resolution electron energy monochromator. This dual source approach will enable us to perform rapid exploratory measurements and then investigate interesting features either with low current densities (~0.1 mA/mm2) or with high resolution (~ 50 meV) at good count rates (~ 100 Hz). The instruments will serve the research community at the University of Delaware, Rutgers University, and other neighboring institutions. With the proposed instrument, the PI's will add to their strong track record of outreach both within and out of the academic communities, as well as ensure members of underrepresented groups have direct participation in our research activities. The proposed instrument will give previously unattainable experimental access a wide range of problems in modern condensed matter and materials physics, semiconducting organic materials, organic molecular electronics, modern electronics, and superconductivity. This new instrument will probe, with very high energy resolution, the unfilled electronic levels in conducting systems with minimal perturbation of the other charge carriers and minimal damage to the materials system. We propose a program to develop and construct the prototype for a new generation of inverse photoemission spectrographs that will serve the dual demands of modern materials science -- low current density and high energy resolution -- while maintaining high count rates. While traditional photoelectron spectroscopy has played a central role in establishing key properties of the bonding and charge carriers in the filled electronic levels of these materials, there has been markedly less progress towards understanding the unfilled levels. Inverse photoemission (IPE) spectroscopy is the natural choice for probing this energy range, but high current densities and low energy resolution limit its application to these interesting systems. The proposed instrument will greatly relieve these shortcomings. The information gained from this new instrument will enable intelligent design of candidate species for molecular electronics or organic semiconductor applications. Similarly it will test our current theoretical understanding of highly correlated electron systems, for example, superconductors, by experimentally probing the energy and momentum dependence of the spectral function in a new regime. The instruments will serve the research community at the University of Delaware, Rutgers University, and other neighboring institutions. With the proposed instrument, the PI's will add to their strong track record of outreach both within and out of the academic communities, as well as ensure members of underrepresented groups have direct participation in our research activities.