This Grant Opportunity for Academic Liaison with Industry (GOALI) project with the University of Pennsylvania and the IBM T. J. Watson Research Center will study fundamental aspects of electrochemical nucleation, growth, and dendrite formation as functions of substrate and process conditions with a novel imaging tool, the nanoaquarium, which facilitates imaging of electrodeposition in a liquid medium, in real time, with the nanoscale resolution of the transmission electron microscope (TEM). A hermetically-sealed, liquid cell (the nanoaquarium), with a height ranging from tens to hundreds of nanometers, sandwiched between electron-transparent, silicon-nitride windows will be constructed using microfabrication technology for real-time imaging of electrochemical processes with the TEM. The device will be equipped with electrodes for electrochemical plating/dissolution and sensing, and heaters for temperature control. The electrochemical process will be monitored in situ in real time with the electron microscope as a function of solution composition, additives, applied voltage/current, current ramping, electrode geometry, and temperature. The device will enable one to vary process conditions dynamically and monitor and modify parameters in real-time, yielding insights that are inaccessible by other means. The results of the study will assist both in developing basic electrochemical nucleation and growth models and in developing materials systems for various manufacturing processes. UPenn will design and construct the electrochemical nanoaquarium based on a previously successful liquid cell. Collaborative electrochemical experiments and data analysis will then be carried out at both IBM and UPenn. The materials studied will be chosen for their relevance to rechargeable battery technology, thin film photovoltaic cells, and advanced interconnects.
Electrochemical processes play a critical role in a plethora of technologies, ranging from energy conversion in batteries, to the production of photovoltaic (PV) cells, to the fabrication of interconnects in high density microelectronics; yet a complete understanding of nucleation, growth, and development of morphology during electroplating is still lacking for many industrially important processes. Since its invention, the electron microscope, with its sub-nanometer resolution has enabled important discoveries in disciplines ranging from materials science to biology. The conventional electron microscope operates, however, in a high vacuum environment and is not capable of imaging processes in liquid media. To enable imaging of processes in liquid media such as electrodeposition and electrodisorption, it is necessary to construct a very thin, hermetically-sealed liquid cell (nanoaquarium) sandwiched between two electron-transparent membranes. Such a device will enable nanoscale observations and a better understanding of the initial, nanoscale stages of the electroplating process that ultimately control the process outcome. In addition to advancing fundamental science, this study will aid the optimization of manufacturing processes, help improve the performance and reliability of rechargeable batteries, and assist in the development of high throughput, low cost production of solar cells and higher density microelectronics. In addition, the nanoaquarium has broad applicability for in situ electron microscope imaging of diverse processes in liquid media such as nano particle self and controlled assembly, formation of metamaterials with unique properties, and biological phenomena. The nanoaquarium is likely to be transformative, provide new insights in diverse disciplines, and enable discoveries. The grant will also facilitate the translation of academic research to an industrial laboratory and enable academic researchers to get acquainted with critical problems encountered by manufacturers. The results of the study, in particular the videos obtained with the nanoaquarium, will be incorporated into instructional material in courses in materials science, electrochemistry, and nanotechnology. In situ electron microscopy videos obtained with the nanoaquarium convey information about dynamical, nanoscale phenomena that is vivid, accessible, and exciting to scientists and non-scientists alike. Narrated videos will be posted on the web for high school students and teachers, undergraduate students, and the public to convey the excitement of discovery and promote interest in science and engineering.
Electrochemical processes play a critical role in a various technologies, ranging from energy conversion in batteries, to the production of photovoltaic (PV) cells, to the fabrication of interconnects in high density microelectronics; yet a complete understanding of nucleation, growth, and development of morphology during electroplating is still lacking for many industrially important processes. Intellectual Merit: We studied the initial stages of electroplating that ultimately control process outcomes, the solid phase growth dynamics, and the evolution of morphological instabilities as functions of process conditions. Since in many cases morphological instabilities are undesired, we also devised and tested active and passive control strategies to control the deposited phase morphology. The active control consisted of electric current modulation. The passive control consisted of the inclusion of additives in the bath. To enable the imaging of the electrodeposition in-situ, in real time, with sufficient spatial resolution, we constructed a very thin, hermetically-sealed liquid cell (nanoaquarium) sandwiched between two electron-transparent membranes. The device was equipped with electrodes and enabled us to image the processes of interest with the transmission electron microscope (TEM), obtaining spatial resolution of a few nanometers. Our experiments generated a wealth of data, which necessitated the development of automated image processing algorithms for quantitative analysis of the characteristics of the growing interfaces such as interface roughness, wavelength, and local current density distribution. The data extracted from our experiments revealed detailed information about the physics of morphology dynamics, especially during the critical transition to a diffusion-limited regime and the consequential interfacial instabilities. The results of our study will assist engineers in developing electrochemical nucleation and growth models and in designing manufacturing processes to achieve desired results. We have also studied the interactions of the electron beam with the imaged medium. The irradiated electrons interact with the irradiated medium, i.e., water, and cause a cascade of reactions that lead to the formation of, among other things, radicals and gaseous species. To this end, we developed a computer code to predict the concentrations of radiolysis products as functions of space, time, and operating conditions. We compared our predictions with our experimental data and that of others and explained conflicting experimental observations previously reported in the literature. A good understanding of the electron beam – irradiated medium interactions is important for the design of experiments that minimize unwanted artifacts and for the correct interpretation of experimental results. We have also shown that the electron beam can be used to precipitate metal ions from solution and to pattern nanowires without a need for a mask. Our results were reported in scientific papers, conference proceedings, and lectures, a few of which were posted on the web. We also posted on the web the computer codes that we have developed to determine radiolysis products and to analyze experimental data. Broader impacts: In addition to advancing fundamental science, our study aid optimizing important manufacturing processes such as high density microelectronics. The nanoaquarium has broad applications for in situ electron microscope imaging of diverse phenomena in liquid media, ranging from material science to heat transfer to biology. Our devices can be readily adapted for use by scientists without a need for expensive TEM sample holders. Our studies of electron beam interactions with the irradiated medium are of significance to the entire electron microscopy community. The NSF grant facilitated the translation of academic research to industrial laboratories and enabled academic researchers to get acquainted with critical problems encountered by manufacturers. The results of this study, in particular the videos obtained with the nanoaquarium were incorporated into instructional material in courses in nanotechnology. Narrated videos and lectures were posted on the web. Videos were shown to high school students and teachers as part of the NanoDay@Penn to convey the excitement of discovery and promote interest in science and engineering.
