PNNL

Abstract

In the past decade, photoelectron emission microscopy (PEEM) has undergone major instrument development and become commercially available. PEEM probes photoelectrons in a high-contrast imaging technique that is sensitive to the surface electronic structure. In this paper we illustrate the principles of PEEM and analyze important PEEM contrast mechanisms. We briefly summarize the applications of PEEM to areas such as surface structure analysis, surface chemistry, magnetism, and semiconductor device characterization. Two important new directions in PEEM development are multiphoton and time-resolved PEEM. Multiphoton PEEM is capable of imaging materials with work functions greater than the incident photon energy, while time-resloved PEEM enables study of fast relaxation dynamics of surface intermediate states. We discuss our recent progress on implementing femtosecond time-solved PEEM and multiphoton PEEM to investigate the silver nanostructured film coated on silicon. The multiphoton images consist of some “hot spots” with far greater photonelectron intensity than is observed in single-photon derived images. We surmise that this is due to the highly-selective excitation of surface localized plasmon of silver. To illustrate the utility of PEEM, we also describe an in-situ thermal-induced structural phase transformation of CuZnA1 shape memory alloy.