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Events
Event Date: June 7, 2016

June 7th and 8th
University of Illinois
Frederick Seitz Materials Research Laboratory
http://www.mrl.illinois.edu/events/conferences-workshops/advanced-materials-characterization-workshop-2016

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Image of the Month
Posted Date: June 1, 2016
RHK-June-IOM-2016-Fu-PRB_93_045430

Figure 1: Zoomed 5 nm image. Using Fourier filtering of the larger raw image, the superlattice is removed, and only the crystal lattice remains. Specifically, in filtering, we selected all of the crystallographic Bragg peaks connected by reciprocal lattice vectors appearing in the FFT. (PHYSICAL REVIEW B 93, 045430 (2016))

We use scanning tunneling microscopy to study the lithium molybdenum purple bronze (Li0.9Mo6O17) at room temperature. Our measurements allow us to identify the single-crystal cleave plane and show that it is possible to obtain clean cleaved surfaces reflecting the crystal structure without the complications of nanoscale surface disorder. In addition to the crystal lattice, we observe a coexisting discommensurate superlattice with wave vectors q = 0.5a ± 0.25b. We propose that the origin of the superstructure is a surface reconstruction that is driven by cleaving along a crystal plane that contains in-plane MoO4 tetrahedra connected to out-of-plane MoO6 octahedra through corner-sharing oxygens. When combined with spectroscopic measurements, our studies show a promising avenue through which to study the complex physics within Li0.9Mo6O17.

Credits:
Ling Fu,1  Aaron M. Kraft,1  Martha Greenblatt,2  and Michael C. Boyer1,*  (Phys. Rev. B 93, 045430 (2016))

1 Department of Physics, Clark University, Worcester, Massachusetts 01610, USA

2 Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, USA

Images and data graciously provided by Michael Boyer, Clark University, Worcester, Massachusetts.

Microscope:
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Control System:
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Image of the Month
Posted Date: May 1, 2016
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Figure 1: Atomic positions obtained by density functional calculations overlaid on an image created by a scanning tunneling microscope of D2O-covered step edges on Pt(553). STM image of D2O-covered step edges on Pt(553) [Tip type: cut and pull Pt/Ir; 4.5×4.5nm2; TSTM=25K; V=−1V , I= −9pA (Phys. Rev. Lett. 116, 136101)

The interaction of platinum with water plays a key role in (electro)catalysis. Herein, we describe a combined theoretical and experimental study that resolves the preferred adsorption structure of water wetting the Pt(111)-step type with adjacent (111) terraces. Double stranded lines wet the step edge forming water tetragons with dissimilar hydrogen bonds within and between the lines. Our results qualitatively explain experimental observations of water desorption and impact our thinking of solvation at the Pt electrochemical interface.

Credits:
Manuel J. Kolb1, Rachael G. Farber2, Jonathan Derouin2, Cansin Badan1, Federico Calle-Vallejo1, Ludo B. F. Juurlink1, Daniel R. Killelea2, and Marc T. M. Koper1 (Phys. Rev. Lett. 116, 136101)

1 Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA, Leiden, The Netherlands

2 Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, Illinois 60660, USA

Images and data graciously provided by Dan Killelea, Loyola University Chicago, Chicago, Illinois.

Microscope:
RHK PanScan Freedom Microscope

Control System:
RHK R9 Control System

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Image of the Month
Posted Date: April 1, 2016
institution

Figure 1: Adsorption of DDQT molecules on Au(111) in the intermediate coverage regime. STM image [set point 100 mV, 5 pA] of a large areafeaturing a finite-sized 2D crystal of DDQT with individual DDQT dimers in the vicinity (J. Phys. Chem. C 2015, 119, 26959−26967)

Charge transport in electronic applications involving molecular semiconductor materials strongly depends on the electronic properties of molecular-scale layers interfacing with external electrodes. In particular, local variations in molecular environments can have a significant impact on the interfacial electronic properties. In this study, we use scanning tunneling microscopy and spectroscopy to investigate the self-assembly regimes and resulting electronic structures of alkyl-substituted quaterthiophenes adsorbed on the Au(111) surface. We find that at dilute molecular concentrations, dimerized cis conformers were formed, while at higher concentrations corresponding to small fractions of a submonolayer, the molecular conformation converted to trans, with the molecules self-assembled into ordered islands. At approximately half-monolayer concentrations, the structure of the self-assembled islands transformed again showing a different type of the trans conformation and qualitatively different registry with the Au(111) lattice structure. Molecular distributions are observed to vary significantly due to variations in local molecular environments, as well as due to variations in the Au(111) surface reactivity. While the observed conformational diversity suggests the existence of local variations in the molecular electronic structure, significant electronic differences are found even with molecules of identical apparent adsorption configurations. Our results show that a significant degree of electronic disorder may be expected even in a relatively simple system composed of conformationally flexible molecules adsorbed on a metal surface, even in structurally well-defined self-assembled molecular layers.

Credits:
Dmitry A. Kislitsyn, Benjamen N. Taber, Christian F. Gervasi, Stefan C. B. Mannsfeld, Lei Zhang,
Alejandro L. Briseno, and George V. Nazin (J. Phys. Chem. C 2015, 119, 26959−26967)
Images and data graciously provided by George Nazin, University of Oregon, Eugene, Oregon.

Microscope:
RHK PanScan Freedom Microscope

Control System:
RHK Technology Control System

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