Christine Caragianis-Broadbridge

A cross-sectional atomic force microscopy study of nanocrystalline Ge precipitates in SiO2 formed from metastable Si1−xGexO2

In recent years, many investigators have reported visible photoluminescence from structures that consist of Ge or Si nanocrystals embedded in a SiO2 matrix deposited or grown on various substrates. We have developed a rapid technique for studying the through-thickness microstructure of this class of materials via atomic force microscopy (AFM) and, using this technique, we report on the precipitation and growth of Ge crystallites formed via a two-step process of hydrothermal oxidation of Si1−xGexO2 (x=0.15) at 450–500 °C and subsequent chemical reduction in forming gas (85/15: N2/H2; 800 °C). The Ge-particle distributions obtained with this AFM cross-sectional technique are consistent with those previously reported using other techniques. The utility of cross-sectional AFM for the evaluation of nanoscale features in the thickness of a thin film is evaluated.

A Study of the Effect of Oxide Structure on the Synthesis of Nanocrystalline Ge from Si 1 - x Ge x O 2

In this study, Si 1-x Ge x O 2 was produced by hydrothermal oxidation of Si 1-x Ge x alloys at temperatures of 450–500°C and pressures of 30–40 MPa. The resulting Si 1-x Ge x O 2 samples were annealed in forming gas (85/15:N 2 /H 2 ) and the precipitation and growth of Ge crystallites as a function of oxidation and annealing conditions were investigated using FTIR, Raman spectroscopy, XPS, AFM and high resolution SEM. The particle size distribution through the oxide thickness is accounted for by consideration of the incorporation of hydroxyl groups in the amorphous oxide network and their effect on the rate of diffusion of Ge in the amorphous structure during H 2 annealing.

Computer assisted analysis of microscopy images

The use of Transmission Electron Microscopy (TEM) to characterize the microstructure of a material continues to grow in importance as technological advancements become increasingly more dependent on nanotechnology1 . Since nanoparticle properties such as size (diameter) and size distribution are often important in determining potential applications, a particle analysis is often performed on TEM images. Traditionally done manually, this has the potential to be labor intensive, time consuming, and subjective2. To resolve these issues, automated particle analysis routines are becoming more widely accepted within the community3. When using such programs, it is important to compare their performance, in terms of functionality and cost. The primary goal of this study was to apply one such software package, ImageJ to grayscale TEM images of nanoparticles with known size. A secondary goal was to compare this popular open-source general purpose image processing program to two commercial software packages. After a brief investigation of performance and price, ImageJ was identified as the software best suited for the particle analysis conducted in the study. While many ImageJ functions were used, the ability to break agglomerations that occur in specimen preparation into separate particles using a watershed algorithm was particularly helpful4.

Authentic Science Research and the Utilization of Nanoscience in the Non-Traditional Classroom Setting

Applications of nanoscience in the non-traditional classroom have successfully exposed students to various methods of research with applications to micro- and nano-electronics. Activities obtained from the NanoSense website associated with current global energy and water concerns are solid examples. In this regard, all 36 students in the 2008-2009 Science Research Program (SRP) prepared and delivered individual and group lesson plans in addition to their authentic, year-long research projects. Two out of 36 students selected nanoscience based projects in preparation for science fair competition in 2009. Additionally, preliminary research was conducted while participating in the Center for Research on Interface Structures and Phenomena (CRISP) Research Experience for Teachers (RET) Program in summer 2008 which supported the idea of developing a photolithography kit. This kit is intended to introduce high school students to the fundamentals of photolithography. In this paper, the design, implementation and feasibility of this kit in the high school classroom is described as well as details involving individual and group nanoscience based projects. Supporting educational models include self-regulated learning (SRL) concepts; situated cognition; social constructivism; Renzullis (1977) enrichment triad and Types I – III inquiry enrichment activities.

Preparation, Microstructure and Physical Characteristics of Ferroelectric Pb 5 Ge 3 O 11 Thin Films for Memory Application

We report sol-gel process of Pb 5 Ge 3 O 11 (PGO) as well as the microstructure and physical properties of ferroelectric PGO films for memory applications. The PGO sol was prepared from lead acetate hydrate, germanium isopropoxide, and di(ethylene glycol) ethyl ether. The reactions taking place during the sol-gel process were examined in detail. Diethanolamine (DEA) was added to help maintain the desired species ratio and prevent germanium oxide precipitation. The preferred orientation of the PGO thin films was well controlled by the heating and reflux procedures in the sol-gel preparation process. Additionally, to examine the impact of postdeposition processing, selected samples were oxygen annealed at temperatures ranging from 450–650°C. The samples were characterized with X-ray diffraction (XRD), non-contact (planview) atomic force microscopy (NC-AFM). The resulting data indicate that the microstructure and physical properties of PGO films depend strongly on the precursor preparation as well as the post deposition annealing temperature.

Microstructure and Electronic Properties of Thin Film Nanoporous Silica as a Function of Processing and Annealing Methods

Alcogels, aerogel precursors, were prepared by hydrolysis and condensation of the metal alkoxide tetraethylorthosilicate and were catalyzed by both acids and bases, according to a standard reaction. Alcogel solution was spin coated onto p-type silicon wafers and fluid extraction was achieved in an uncontrolled (room temperature, atmospheric pressure) environment. Film porosity was retained through surface modification and/or low vapor pressure solvent techniques. The microstructure and electronic properties of the resulting films were evaluated using non-contact atomic force microscopy (nc-AFM), cross sectional scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Metal insulator semiconductor (MIS) devices were prepared and current-voltage and capacitance-voltage measurements were obtained from these devices. Annealing studies reveal a dramatic temperature dependent effect on both the microstructure and electronic properties of the porous silica films.