David D. Allred received Alumni Professorship Award

Abstract: A series of 20 and 100 nm Fe(53)Pt(47) thin films sputter-deposited onto Si substrates have been thermally annealed using a pulsed thermal plasma arc lamp. A series of one, three or five pulses were applied to the thin films with widths of either 50 or 100 ms. The microstructure and magnetic properties of these annealed Fe(53)Pt(47) films are discussed according to the various annealing conditions and A1 to L1(0) phase transformation. Upon pulse annealing, the average in-plane grain size of 15 nm (nearly equivalent for both film thicknesses) was observed to increase to values near 20 nm. In general, increasing the pulse width or number of pulses increased the L1(0) order parameter, tetragonality of the c/a ratio and coercivity of the specimen. The exception to this trend was for five pulses at 100 ms for both film thicknesses, which indicated a reduction of the order parameter and coercivity. This reduction is believed to be a result of the interdiffusion of Fe and Pt into the Si substrate and the formation of iron oxide clusters in the grain boundaries characterized by atom probe tomography. (C) 2009 Published by Elsevier B.V.

Abstract: We recently developed a fabrication process for carbon nanotube templated MEMS. The fabrication process involves growing a three dimensional pattern from carbon nanotube forests and filling that forest by chemical vapor infiltration to make a solid structure. This templating process allows us to fabricate extremely high aspect ratio microscale structures from a wide variety of materials. The nanotube structures can be hundreds of microns tall with lateral pattern dimensions down to a few microns. The chemical vapor infiltration has been shown with silicon and silicon nitride but could be extended to many other materials. In this paper, we investigate the microstructure of the filling material and extend the process to the fabrication of comb actuators.

Abstract: Vanadium dioxide (VO2) single crystals undergo a structural first-order metal to insulator phase transition at approximately 68°C. This phase transition exhibits a resistivity change of up to 5 orders of magnitude in bulk specimens. We observe a 2-3 order of magnitude change in thin films of VO2. Individual particles with sizes ranging from 50 to 250 nm were studied by means of Transmission Electron Microscopy (TEM). The structural transition for individual particles was observed as a function of temperature. Furthermore, the interface between grains was also studied. We present our current progress in understanding this phase transition for polycrystalline thin films of VO2 from the view of individual particles.

Abstract: Re-distribution of Mn atoms implanted into Czochralski silicon (CzSi: Mn) and floating zone silicon (FzSi: MN) after thermal annealing between 300 and 1,000 degrees C have been investigated by secondary ion mass spectroscopic technique. The motivation behind our study comes from recent report of strong magnetic ordering up to 400 K of Mn(+) implanted silicon samples reported by Bolduc et al. (Phys Rev B 71: 033302, 2005). Our silicon substrates were implanted with 160 keV Mn(+) ion to a dose of 1 x 10(16) cm(-2) at either room temperature or at 340 degrees C. The Mn profiles after annealing above 900 degrees C showed multiple concentration peaks for the 340 degrees C implanted samples, but not for the samples implanted at room temperature. We also carried out cross sectional TEM and ferromagnetic resonance measurements to correlate the micro-structural and magnetization data with the Mn depth profile obtained by SIMS.

Abstract: Antiphase domains are seen in single crystal gamma lithium aluminate (gamma-LiAlO(2)) with 16.7 nm periodicity in the < 110 > direction. Alternate domains have a 1/2 [001] shift. Beta phase lithium aluminate (beta-LiAlO(2)) is seen to form on the surface of the as-received wafers with an epitaxial strain limited relationship with the bulk gamma phase. The orthorhombic beta phase aligns with the a and b axes (0.528 and 0.630 nm) matching with the tetragonal gamma phase's a and c axes (0.5168 and 0.6268 nm). The gamma and beta phases are seen to have different etch rates. The beta phase converts back to the gamma phase above 450 degrees C. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3014193]

Abstract: When considering the optical performance of thin films in the Extreme Ultraviolet (EUV), developing an accurate physical description of a thin film coating is necessary to be able to successfully model optical performance. With the short wavelengths of the EUV, film interfaces and sample roughness warrant special attention and care. The surfaces of thin film samples are routinely measured by Atomic Force Microscopy, from which roughness can be determined. However, characterizing the quality of interfaces below the surface is much more challenging. In a recent study of scandium oxide thin films, High Resolution Transmission Electron Microscopy and Annular Dark Field Scanning Transmission Electron Microscopy (ADF STEM) were used to study the cross section of the samples. ADF STEM data analyzed along a path into the volume of the sample (normal to the interfaces) reveals information of sample density versus depth. This density-depth profile reflects the presence of subsurface film interfaces in the volume of the sample. Additionally, information from the ADF STEM profile can be used to gauge the roughness of the subsurface interfaces, which is used to refine the sample description during modeling. We believe this is the first use of ADF STEM in this capacity. This characterization technique may provide key insight to subsurface interface quality, which is particularly important when optimizing the performance of multilayer coatings in the EUV.