Dual Plasma Co-Deposition of Mixed-Phase Thin Films James Kakalios , University of Minnesota Twin-Cities, DMR 0705675

1. Dual Plasma Co-Deposition of Mixed-Phase Thin FilmsJames Kakalios, University of Minnesota Twin-Cities, DMR 0705675 Mixed-phase thin films consisting of nanocrystalline inclusions in an amorphous matrix combine the large area advantages of amorphous semiconductors with the superior opto-electronic characteristics of crystals. The mixed-phase films are grown in a novel dual chamber co-deposition system, where one type of nanocrystallite is synthesized, and then entrained by an inert carrier gas into a second PECVD chamber, where the surrounding amorphous matrix is deposited. One advantage of this system is that the two materials synthesis are independent. We have fabricated nc-Si in a-Si:H; nc-Si in a-SiNx:H; and nc-Ge in a-Si:H mixed-phase films. For n-type doped a/nc-Si:H films, we find a transition in transport mechanism as the nanocrystalline concentration is increased. For low crystal fractions conduction is described by Arrhenius behavior, while for higher nanocrystal content conduction is consistent with multi-phonon hopping, possibly through extended nanocrystalline clusters with weak electron-phonon coupling. Mixed-phase thin films of nanocrystallites (nc) embedded within an amorphous semiconductors matrix are synthesized in a dual-chamber co-deposition system. Si nc (diameter 5 nm) are grown in one chamber, and then entrained with Ar and injected into a second PECVD system in which the surrounding a-Si:H is deposited. Films with nc concentrations from < 1% to over 60% (as measured by Raman spectroscopy) in n-type a-Si:H have been fabricated. Log-log plot of the temperature dependence of the dark conductivity of n-type a/nc-Si:H films as a function of crystal fraction. When the crystal fraction exceeds 15%, the conductivity no longer follows an Arrhenius dependence, but exhibits a power-law dependence on temperature, consistent with conduction via multi-phonon hopping.

2. Quantum Mechanics and NanophysicsJames Kakalios, University of Minnesota Twin-Cities, DMR 0705675 As the science consultant for the Warner Bros. film Watchmen, the University of Minnesota asked me to make a short video on The Science of Watchmen for their youtube.com page. In this video I demonstrate the basics of wave/particle duality (as it relates to a superpowered character in the film). This video has been viewed over 1.7 million times to date, and won a regional EMMY award and was nominated for a national WEBBY. In 2010 Kakalios published The Amazing Story of Quantum Mechanics, which describes the physics of lasers, LEDs, transistors and hard drives, using examples from old science fiction pulps and comic books. Kortshagen organized and was involved in a multitude of events that engage the public in research of the Mechanical Engineering Department. Among others, he organized a research lab open house, public lectures around mechanical engineering topics, and a full day of activities for high school students around nanoparticle research.