Image of the Month

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Image of the Month
Posted Date: December 1, 2012
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Figure 6. (a) Scanning electron microscope image of a 200 nm wide Pt line; (b) 3D topographic of a 2.5 μm x 2.5 μm region where the 200 nm wide Pt line lies on top of a 1 μm wide Pt line; (c) thermal image of the same region shown in panel b. The temperature rise of the 200 nm line is seen to be lower in the region where it intersects the 1 μm wide line because the 1 μm wide Pt line acts as a fin.

Microscope: RHK Technology, Customized UHV7500 STM/AFM

Control System: RHK Technology SPM1000

Credits – Kyeongtae Kim, Wonho Jeong, Woochul Lee, and Pramod Reddy – University of Michigan, Ann Arbor

Reference – ACS Nano, 2012, 6 (5), pp 4248–4257

Abstract – Understanding energy dissipation at the nanoscale requires the ability to probe temperature fields with nanometer resolution. Here, we describe an ultra-high vacuum (UHV)-based scanning thermal microscope (SThM) technique that is capable of quantitatively mapping temperature fields with ∼15 mK temperature resolution and ∼10 nm spatial resolution. In this technique, a custom fabricated atomic force microscope (AFM) cantilever, with a nanoscale AuCr thermocouple integrated into the tip of the probe, is used to measure temperature fields of surfaces. Operation in an UHV environment eliminates parasitic heat transport between the tip and the sample enabling quantitative measurement of temperature fields on metal and dielectric surfaces with nanoscale resolution. We demonstrate the capabilities of this technique by directly imaging thermal fields in the vicinity of a 200 nm wide, self-heated, Pt line. Our measurements are in excellent agreement with computational results; unambiguously demonstrating the quantitative capabilities of the technique. UHV-SThM techniques will play an important role in the study of energy dissipation in nanometer-sized electronic and photonic devices and the study of phonon and electron transport at the nanoscale.
Keywords: scanning thermal microscopy . ultrahigh vacuum . quantitative temperature profiling . nanoscale thermal contact . thermocouple probe

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Image of the Month
Posted Date: October 1, 2012
iotm-october-2012

Description:
Microscope: RHK Technology UHV 300 STM
Control System: RHK Technology SPM1000 Control System

Credits:
Jose A. Hinojosa Jr., Jason F. Weaver – Department of Chemical Engineering, University of Florida, Gainesville

Reference:
Surface Science 605 (2011) 1797–1806

Abstract:
We used scanning tunneling microscopy (STM) to characterize PdO(101) thin films grown on Pd(111), and the structural changes that occur during isothermal decomposition.We find that the PdO(101) thin films have high-quality surface structures that are characterized by large, crystalline terraces with low concentrations of point defects. Small domains of single-layer oxide are also present on the top layer of relatively thick PdO(101) films grown at 500 K. The thinner PdO(101) films exhibit negligible quantities of such domains, apparently because new domains agglomerate rapidly as the film thickness decreases. We find that the isothermal decomposition rate of a PdO(101) film at 720 K exhibits an autocatalytic regime in which the rate of oxygen desorption increases as the oxide decomposes. Our STM results demonstrate that reduced sites created during oxide decomposition catalyze further PdO decomposition, and reveal strong kinetic anisotropies in the decomposition. The kinetic anisotropies produce one-dimensional reaction fronts that propagate preferentially along the atomic rows of the PdO(101) surface, resulting in the formation of long chains of reduced sites.We also find that reduced sites promote oxygen recombination in neighboring rows of the Pd(101) structure, causing loops and larger aggregates of reduced sites to form. The promotion of decomposition across the atomic rows can qualitatively explain the autocatalytic desorption kinetics. Finally, the STM images provide evidence that underlying PdO(101) layers transfer oxygen to reduced surface domains, thus producing large domains of PdO(101) islands that coexist with reduced domains as well as the larger PdO(101) terraces of the initial surface. Re-oxidation of the surface acts to sustain the autocatalytic decomposition kinetics, and provides a mechanism for oxygen atoms to ultimately evolve from the subsurface of the PdO(101) film.

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Image of the Month
Posted Date: September 1, 2012
iotm-september-2012

Microscope: RHK Technology UHV300
Control System: RHK Technology SPM 1000

Credits:

Hidong Kima, Otgonbayar Dugerjava,Ganbat Duvjir a, Huiting Lia, Seunghun Jangb, Moonsup Hanb, B.D. Yub, Jae M. Seoa

a Department of Physics and Institute of Photonics and Information Technology, Chonbuk National University, Jeonju 561-756, Republic of Korea

b Department of Physics, University of Seoul, Seoul 130-743, Republic of Korea

Reference: H. Kim et al. / Surface Science 606 (2012) 312–319

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Image of the Month
Posted Date: August 1, 2012
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Microscope: RHK UHV300

Controller: RHK SPM1000

Credits:
P. A. Bennett, Zhian He, David J. Smith and F. M. Ross
Physics Department, Arizona State University, Tempe, AZ 85287 USA
School of Materials, Arizona State University, Tempe, AZ 85287 USA
IBM T. J. Watson Research Center, Yorktown Heights NY 10598 USA

Reference: Thin Solid Films – Vol. 519, Issue 24, 3 October 2011, p. 8434-8440

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Image of the Month
Posted Date: July 1, 2012
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Microscope:
RHK Technology, ATM 300

Controls:
RHK SPM 1000

Contributors:
C. Meier, M. Roos, D. Künzel, A. Breitruck, H. Hoster , A. Gross, R. J. Behm, U. Ziener – University of Ulm, Germany

K. Landfester –  Max-Planck Institute for Polymer Research, Mainz, Germany

Reference:
J. Phys. Chem. C 2010, 114, 1268-1277

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Image of the Month
Posted Date: June 1, 2012
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Abstract:
See Abstract

Microscope:
RHK Technology, UHV 300

Controls:
UHV SPM 100

Contributors:
Miki Nakayama, Natalie A. Kautz, Tuo Wang, and S. J. Sibener

Reference:
dx.doi.org/10.1021/la204986n | Langmuir

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Image of the Month
Posted Date: March 1, 2011
iotm-march-2011

(a)–(c) Intensity plots of G(V)/GN as a function of temperature and applied bias for three different films (upper panels), and the resistance vs temperature (R-T) in the same temperature range (lower panels); vertical dotted lines in the upper panels correspond to Tc. Insets of panels (a),(b) and left inset of panel (c) show representative tunneling spectra in the superconducting state (blue), in the pseudogap state (green) and above the pseudogap temperature (red). The right inset of panel (c) shows the AA background subtracted spectra at 2.65 K. [right inset of Fig. 2(c)] clearly reveals the presence of broadened coherence peaks around 2 mV confirming the superconducting origin of the pseudogap feature. In addition, the individual line scans [23], reveal that the superconducting state becomes progressively inhomogeneous as the disorder is increased [11].

Microscope:
Homebuilt STM

Controls:
RHK SPM 100

Contributors:
M. Mondal, A. Kamlapure, M. Chand, G. Saraswat, S. Kumar, J. Jesudasan, L. Benfatto, V. Tripathi, and P. Raychaudhuri – Tata Institute of Fundamental Research and Sapienza University

Reference:
Phys. Rev. Lett. 106, 047001 (2011)

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Image of the Month
Posted Date: February 1, 2011
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Porphyrin derivatives are promising candidates for the generation of functional molecular architectures on surfaces. The unambiguous identification of individual porphyrin species is a prerequisite in this regard. We investigated a layer of intermixed tetraphenylporphyrins (TPP), namely 2HTPP, FeTPP and CoTPP at room temperature. Voltage-dependent STM imaging was successfully applied to discriminate the very similar porphyrins. The characteristic appearance of CoTPP at low negative voltages (>-0.4 V) can be traced back to a specific interaction of the Co dz2 orbital with the underlying Ag substrate. The dumbbell appearance observed for FeTPP over a wide bias range and for CoTPP at lower negative voltages (<-0.4 V) is in line with the well known saddle shape of the porphyrin macrocycle in the adsorbed state.

Microscope:
UHV300 VT

Controls:
RHK SPM 100

Contributors:
F. Buchner, K.-G. Warnick, T. Wölfle, A. Görling, H.-P. Steinrück, W. Hieringer and H. Marbach – Universitat Erlangen-Nurnberg

Reference:
J. Phys. Chem. C 2009, 113, 16450–16457

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Image of the Month
Posted Date: January 1, 2011
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Raw images showing the friction signal in the left-to-right sliding direction. Upper row: 4-layer graphene; lower row: bulk graphite; right column: Low-pass filtered images of the friction measurements showing the periodicity of the lattice. Black dots represent the periodic sites of the friction force signal. The scale bars correspond to 0.5 nm.

Microscope:
UHV350

Controls:
RHK SPM 100

Contributors:
Q. Li and R.W. Carpick, University of Pennsylvania

Reference:
Science 328, 76 (2010) DOI: 10.1126/science.1184167

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Image of the Month
Posted Date: August 1, 2010
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RHEED intensity oscillation monitored on the specular spot during the growth of the LSMO on STO substrate at 900 °C. Inset a1 and a2: RHEED pattern obtained before and after deposition, respectively. (b) Resistivity/magnetization vs temperature curves for LSMO thin films of 5 nm thickness. STM topographic images (1×1 um2) with set point (sample bias 0.7 V, current 0.5 nA) taken at (c) 300 K and (d) 105 K.

Reprinted with permission from Abhimanyu Rana, Kashinath Bogle, Onkar Game, Shankar Patil, Nagarajan Valanoor, and Satishchandra Ogale, APPLIED PHYSICS LETTERS 96, 263108 2010. Copyright 2010, American Institute of Physics.

Microscope:
UHV3500 VT with Variable Magnetic Field

Controls:
RHK SPM 100

Contributors:
Abhimanyu Rana, Kashinath Bogle, Onkar Game, Shankar Patil, Nagarajan Valanoor, and Satishchandra Ogale – NCL, Pune and Univ. of New South Wales

Reference:
APPLIED PHYSICS LETTERS 96, 263108 (2010)

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