Anna M. Zaniewski

Graphene as a Long-Term Metal Oxidation Barrier: Worse Than Nothing

Anticorrosion and antioxidation surface treatments such as paint or anodization are a foundational component in nearly all industries. Graphene, a single-atom-thick sheet of carbon with impressive impermeability to gases, seems to hold promise as an effective anticorrosion barrier, and recent work supports this hope. We perform a complete study of the short- and long-term performance of graphene coatings for Cu and Si substrates. Our work reveals that although graphene indeed offers effective short-term oxidation protection, over long time scales it promotes more extensive wet corrosion than that seen for an initially bare, unprotected Cu surface. This surprising result has important implications for future scientific studies and industrial applications. In addition to informing any future work on graphene as a protective coating, the results presented here have implications for graphenes performance in a wide range of applications.

Electronic and optical properties of metal-nanoparticle filled graphene sandwiches

We sandwich gold nanoparticles between graphene sheets and contrast the electronic and optical properties of these hybrid structures to those of single layer graphene with and without gold nanoparticle overlayers, and laminated unfilled double layers. Undecorated graphene has the highest sheet resistance while filled sandwiches have the lowest. The optical extinction spectrum for sandwiches is redshifted and broadened compared to decorated single layer graphene. We also find that the presence of gold nanoparticles in sandwiches shifts the work function relative to unfilled double-layer graphene. The low sheet resistance and favorable optical properties of metal-filled sandwiches make them attractive candidates for optoelectronic applications.

Building classroom and organizational structure around positive cultural values

The Compass Project is a self-formed group of graduate and undergraduate students in the physical sciences at UC Berkeley. Our goals are to improve undergraduate physics education, provide opportunities for professional development, and increase retention of students-especially those from populations typically underrepresented in the physical sciences. Compass fosters a diverse, collaborative student community by providing a wide range of services, including a summer program and fall/spring seminar courses. We describe Compasss cultural values, discuss how community members are introduced to and help shape those values, and demonstrate how a single set of values informs the structure of both our classroom and organization. We emphasize that all members of the Compass community participate in, and benefit from, our cultural values, regardless of status as student, teacher, or otherwise.

Learning About Non-Newtonian Fluids in a Student-Driven Classroom

We describe a simple, low-cost experiment and corresponding pedagogical strategies for studying fluids whose viscosities depend on shear rate, referred to as “non-Newtonian fluids.” We developed these materials teaching for the Compass Project,1 an organization that fosters a creative, diverse, and collaborative community of science students at UC Berkeley. Incoming freshmen worked together in a week-long residential program to explore physical phenomena through a combination of conceptual model-building and hands-on experimentation. During the program, students were exposed to three major aspects of scientific discovery: developing a model, testing the model, and investigating deviations from the model.

Modifying the chemistry of graphene with substrate selection: A study of gold nanoparticle formation

Graphene and metal nanoparticle composites are a promising class of materials with unique electronic, optical, and chemical properties. In this work, graphene is used as a reducing surface to grow gold nanoparticles out of solution-based metal precursors. The nanoparticle formation is found to strongly depend upon the graphene substrate selection. The studied substrates include diamond, p-type silicon, aluminum oxide, lithium niobate, and copper. Our results indicate that the chemical properties of graphene depend upon this selection. For example, for the same reaction times and concentration, the reduction of gold chloride to gold nanoparticles on graphene/lithium niobate results in 3% nanoparticle coverage compared to 20% coverage on graphene/silicon and 60% on graphene/copper. On insulators, nanoparticles preferentially form on folds and edges. Energy dispersive X-ray analysis is used to confirm the nanoparticle elemental makeup.

Toward plasma enhanced atomic layer deposition of oxides on graphene: Understanding plasma effects

Integration of dielectrics with graphene is essential for the fulfillment of graphene based electronic applications. While many dielectric deposition techniques exist, plasma enhanced atomic layer deposition (PEALD) is emerging as a technique to deposit ultrathin dielectric films with superior densities and interfaces. However, the degree to which PEALD on graphene can be achieved without plasma-induced graphene deterioration is not well understood. In this work, the authors investigate a range of plasma conditions across a single sample, characterizing both oxide growth and graphene deterioration using spectroscopic analysis and atomic force microscopy. Investigation of graphene and film quality produced under these conditions provides insight into plasma effects. Using their method, the authors achieve ultrathin (<1 nm) aluminum oxide films atop graphene.