Overview

Adam Z. Stieg @ the CNSI - UCLA

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Overview | Electrochemical Scanning Tunneling Microscopy ( EC-STM ) / in-situ STM | Instrument Design | Images & Performance | Sponsors, Suppliers, & Collaborators

The field of study I am presently engaged in entails nanoscale studies at the solid liquid interface, specifically in the field of electrochemistry. In order to achieve atomic and molecular scale resolution for imaging and spectroscopic studies, scanning tunneling microscopy is the tool of choice. Currently, optimization and application of an electrochemical scanning tunneling microscope (EC-STM) designed and constructed in-house is underway in an effort to carry out in-situ studies of both redox active molecular systems and templated electrochemical deposition. The attractive nature of in-situ STM and STS results from its ability to preserve and control the electrode-electrolyte interface while imaging electronic density of states with sub-nanometer resolution. Coarse and controlled fine approach of the tip to the tunneling position as well as controlled feedback scanning have been realized. Tunneling and imaging of atomic periodicities have been achieved in air. Initial trials of imaging in the electrochemical environment have produced intermittent atomic scale resolution. Currently, an upgrade of the control electronics is being addressed.

The study of single molecules that exhibit nanomechanical motion due to their redox behavior are currently areas of great interest in both industrial and academic circles. Within this category fall both molecular machines and molecular switches, such as the rotaxane/catenane family as well as metalloboranes. The attractive nature of in-situ STM and STS results from its intrinsic capability to independently control the electrode-electrolyte interface while imaging electronic density of states with sub-nanometer resolution. In addition, the nature of the electrochemical environment also provides an attractive means to study biological materials such as proteins and DNA in more native surroundings compared to UHV studies with similar levels of resolution.

The second area of study involves the development of innovative methods for the electrochemical nanopatterning of metals as well as exotic molecular layers and heterostructures. Recently, electrochemical deposition of metals into the interstices of self-assembled colloidal polystyrene monolayer templates has demonstrated a correlation between the morphology of the deposited materials and process conditions, namely deposition bias potential and rate. This behavior is attributed to bias-dependent mechanisms and diffusion path effects that are inherently contingent on the potential gradient and the nature of the depletion layer. Atomic Force Microscopy has been employed in initial analyses of the deposited structures, however the limited resolution does not lend itself to definitive conclusions on growth mechanisms. Application of ECSTM will enable controlled deposition and dynamic analysis of these processes at the solid-liquid with atomic resolution .


	Adam Z. Stieg @ the CNSI - UCLA \| home \| back to Research \| Overview \| Electrochemical Scanning Tunneling Microscopy ( EC-STM ) / in-situ STM \| Instrument Design \| Images & Performance \| Sponsors, Suppliers, & Collaborators The field of study I am presently engaged in entails nanoscale studies at the solid liquid interface, specifically in the field of electrochemistry. In order to achieve atomic and molecular scale resolution for imaging and spectroscopic studies, scanning tunneling microscopy is the tool of choice. Currently, optimization and application of an electrochemical scanning tunneling microscope (EC-STM) designed and constructed in-house is underway in an effort to carry out in-situ studies of both redox active molecular systems and templated electrochemical deposition. The attractive nature of in-situ STM and STS results from its ability to preserve and control the electrode-electrolyte interface while imaging electronic density of states with sub-nanometer resolution. Coarse and controlled fine approach of the tip to the tunneling position as well as controlled feedback scanning have been realized. Tunneling and imaging of atomic periodicities have been achieved in air. Initial trials of imaging in the electrochemical environment have produced intermittent atomic scale resolution. Currently, an upgrade of the control electronics is being addressed. The study of single molecules that exhibit nanomechanical motion due to their redox behavior are currently areas of great interest in both industrial and academic circles. Within this category fall both molecular machines and molecular switches, such as the rotaxane/catenane family as well as metalloboranes. The attractive nature of in-situ STM and STS results from its intrinsic capability to independently control the electrode-electrolyte interface while imaging electronic density of states with sub-nanometer resolution. In addition, the nature of the electrochemical environment also provides an attractive means to study biological materials such as proteins and DNA in more native surroundings compared to UHV studies with similar levels of resolution. The second area of study involves the development of innovative methods for the electrochemical nanopatterning of metals as well as exotic molecular layers and heterostructures. Recently, electrochemical deposition of metals into the interstices of self-assembled colloidal polystyrene monolayer templates has demonstrated a correlation between the morphology of the deposited materials and process conditions, namely deposition bias potential and rate. This behavior is attributed to bias-dependent mechanisms and diffusion path effects that are inherently contingent on the potential gradient and the nature of the depletion layer. Atomic Force Microscopy has been employed in initial analyses of the deposited structures, however the limited resolution does not lend itself to definitive conclusions on growth mechanisms. Application of ECSTM will enable controlled deposition and dynamic analysis of these processes at the solid-liquid with atomic resolution .