Catalysis
Three STM images of a Ni3 cluster adsorbed on a MoS2 basal plane at 4 K. All three images show a 60 Å 60 Å area and are plotted as perspective views with the same aspect ratio and angle of view. The images were acquired with sample biases of +2 (A), +1.4 (B), and -2 V (C) and tunneling currents of 100, 100, and 200 pA, respectively. The Ni3 clusters effect on the local density of electronic states - both filled and empty can be seen.
For more information see:
Kushmerick et al. JPCB 102, 10094 (1998).
Image by: J. G. Kushmerick
Surface defect sites such as step edges, kinks, and missing atom defects have long been thought to play an important role in chemisorption. Recent STM measurements of benzene adsorption have yielded real-space observations of the preference for bonding at these sites. An ordered 2D benzene solid forms along straight Cu{111} steps, as shown in the 4nm x 4nm image above. One row of benzene molecules is strongly bound below the step riser (labeled row 1) and another above the step riser (row 2). The adsorption sites at the interface between the 2D solid and 2D gas phases are transiently occupied by benzene (row 3). Molecules can diffuse laterally along the interface or can desorb into the 2D molecular gas on the terrace and readsorb, thereby setting up the dynamic equilibrium between the two phases.
A SAM on Au{111}
Phase separated domains of amide-containing alkanethiolates (yellow) and n-alkanethiolates (red). Phase separation occurs spontaneously when these components are codeposited from solution based on differing interaction strengths of the two molecules.
For more information see:
Smith et al. JPCB 105, 1119 (2001).
Lewis et al. JPCB 105, 10630 (2001)
Image by: P. A. Lewis
A scanning tunneling microscope image (15 nm x 15 nm) of a self-assembled monolayer of n-decanethiolate on Au{111}. The individual molecules closely pack into a hexagonal array. Features of the assembly and surface, respectively, including domain boundaries (light blue stripe) and gold vacancy islands (circular blue depressions) are easily seen.
For more information see:
Smith et al. Molecular Nanoelectronics, T. Lee and M. Reed,
eds, pp. 153-177 (2003).
Image by: R. K. Smith & B. A. Mantooth
A scanning tunneling microscope image (200nm x 140 nm) of a self-assembled monolayer of n-decanethiolate on Au{111} that has been vapor-annealed in n-dodecanethiolate. The protrusions on each of the atomic steps are the 1.1 Å higher n-dodecanethiolate molecules.
For more information see:
Donhauser et al. JACS 125, 11462 (2003).
Image by: Z. J. Donhauser
Perspective views of several molecules inserted into a dodecanethiolate monolayer. The lower image reveals that several of the molecules have switched OFF. [Imaging conditions: 470 Å x 470 Å; 1.0 pA; Vtip=-1.5 V; Frame interval: 13 hr 20 min]
For more information see:
Donhauser et al. Science 292, 2303 (2001).
Donhauser et al. JJAP 41, 4871 (2002).
Mantooth et al. Proc IEEE, 91, 1785 (2003).
and others.
Image by: Z. J. Donhauser & B. A. Mantooth
A field emission scanning electron microscopy image showing a ~30 nm gold dot formed in the center of a hollow gold parent structure supported on an oxidized Si substrate. This nanostructure was fabricated by a 'molecular ruler' resist process developed to extend the range of conventional nanolithography techniques.
For more
information see:
Hatzor et al. Science 291, 1019 (2001).
Image by: A. Hatzor & B. A. Mantooth
Field emission scanning electron microscopy images depicting stages of a nanostructure reduction process. From top to bottom, gaps between "parent" gold traces on oxidized Si are reduced from ~110 nm to ~65 nm (third row left) and ~25 nm (third row right) by 10-layer and 20-layer molecular ruler resists, respectively. Thin metal wires ~65 nm (bottom left) and ~25 nm (bottom right) wide, respectively, are formed, separated by precisely determined gaps from each of the parent gold traces.
For more information see:
Hatzor et al. Science 291, 1019 (2001).
Image by: A. Hatzor & B. A. Mantooth
"Surfing a wave", CS2
riding an electronic surface state on Au{111}
236 Å x 236 Å, image of 0.2 ML CS2 on
Au(111) at 4 K (Vtip =
+ 0.5 V, I = 200 pA)
For more information see:
Sykes et al. JPCB 107, 5016 (2003).
Image by: E. H. Sykes & P. Han
A STM image showing 0.9 ML coverage of CS2 adsorbed on Au{111}. This 220 Å x 220 Å image shows a 60° rotation between two domains on the top terrace (-1000 mV sample bias, 50 pA tunneling current). The direction of the one of the domains on the top terrace is shown to be in phase with the domain on the lower terrace.
For more information see:
Han et al. JPCA 107, 8124 (2003).
Image by: P. Han
Ripples in the electron density of a stepped gold surface taken using scanning tunneling microscopy at 4 Kelvin. The central triangle is a single atom high terrace containing ~ 650 gold atoms. The "billiard balls" are maxima in the electron density at the Fermi level and are caused by constructive interference of the electron waves as they bounce off the edges of the triangular gold box. Quantum mechanics lets us solve the structure using particle in a box equations. We are now investigating how molecules interact with the electron density in these systems.
Image by: E. H. Sykes, P. Han, & B. A. Mantooth
Scanning tunneling microscope image of benzene molecules adsorbed on the unreconstructed gold surface at 4 Kelvin. The "holes" indicate vacancies in the benzene layer where molecules prefer not to adsorb. The red lines are the soliton walls off the Au{111} reconstruction. Our data has given us insight into the thermodynamic and kinetic behavior the benzene molecule exhibits when adsorbed on gold.
For more information see:
Sykes et al. submitted.
Han et al. submitted.
Mantooth et al. in prep.
Image by: B. A. Mantooth, E. H. Sykes & P. Han
A scanning tunneling microscope image of subsurface hydrogen in palladium at 4 Kelvin. The letters are 0.3 Å high and 40 Å wide, and arise from an outward relaxation of the Pd{111} surface atoms to accommodate hydrogen atoms in the subsurface region. The letters are created by inducing segregation of bulk hydrogen to interstitial sites directly below the surface using voltage pulses applied to the microscope tip.
For more
information see:
Sykes et al. submitted.
Image by: E. H. Sykes, L. Fernandez, & B. A. Mantooth