Susan L. Brandow

Bio: Susan L. Brandow is an academic researcher from United States Naval Research Laboratory. The author has contributed to research in topics: Resist & Scanning tunneling microscope. The author has an hindex of 24, co-authored 47 publications receiving 2400 citations.

On the electrochemical etching of tips for scanning tunneling microscopy

Abstract: The sharpness of tips used in scanning tunneling microscopy (STM) is one factor which affects the resolution of the STM image. In this paper, we report on a direct‐current (dc) drop‐off electrochemical etching procedure used to sharpen tips for STM. The shape of the tip is dependent on the meniscus which surrounds the wire at the air–electrolyte interface. The sharpness of the tip is related to the tensile strength of the wire and how quickly the electrochemical reaction can be stopped once the wire breaks. We have found that the cutoff time of the etch circuit has a significant effect on the radius of curvature and cone angle of the etched tip; i.e., the faster the cutoff time, the sharper the tip. We have constructed an etching circuit with a minimum cut‐off time of 500 ns which uses two fast metal–oxide semiconductor field effect transistors (MOSFET) and a high‐speed comparator. The radius of curvature of the tips can be varied from approximately 20 to greater than 300 nm by increasing the cutoff time ...

Low voltage electron beam lithography in self‐assembled ultrathin films with the scanning tunneling microscope

Abstract: With a scanning tunneling microscope (STM) operating in vacuum, we have studied the lithographic patterning of self‐assembling organosilane monolayer resist films. Where the organic group is benzyl chloride, the resist layer can be patterned with electrons down to 4 eV in energy. The patterned films have been used as templates for the electroless plating of thin Ni films. Linewidths down to ∼20 nm have been observed in scanning electron micrographs of the plated films. Still smaller features are observed in STM images of the exposed organosilane films.

Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites

Abstract: Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures, but the absence of crystallinity in these films is expected to be beneficial for many potential applications.

"Dip-Pen" Nanolithography

Abstract: A direct-write “dip-pen” nanolithography (DPN) has been developed to deliver collections of molecules in a positive printing mode. An atomic force microscope (AFM) tip is used to write alkanethiols with 30-nanometer linewidth resolution on a gold thin film in a manner analogous to that of a dip pen. Molecules are delivered from the AFM tip to a solid substrate of interest via capillary transport, making DPN a potentially useful tool for creating and functionalizing nanoscale devices.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Chaotic Dirac billiard in graphene quantum dots.

Abstract: The exceptional electronic properties of graphene, with its charge carriers mimicking relativistic quantum particles and its formidable potential in various applications, have ensured a rapid growth of interest in this new material. We report on electron transport in quantum dot devices carved entirely from graphene. At large sizes (>100 nanometers), they behave as conventional single-electron transistors, exhibiting periodic Coulomb blockade peaks. For quantum dots smaller than 100 nanometers, the peaks become strongly nonperiodic, indicating a major contribution of quantum confinement. Random peak spacing and its statistics are well described by the theory of chaotic neutrino billiards. Short constrictions of only a few nanometers in width remain conductive and reveal a confinement gap of up to 0.5 electron volt, demonstrating the possibility of molecular-scale electronics based on graphene.