Name: visualizing uniaxial-strain manipulation of antiferromagnetic domains in fe1+yte using a spin-polarized scanning tunneling microscope
Uploaded: 2019-03-24T14:00:00
Description: Watch this Scientific Journal Video about Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope at JoVE.com

P.A. acknowledges support from the U.S. National Science Foundation (NSF) CAREER under award No. DMR-1654482. Material synthesis was carried out with the support of the Polish National Science Centre grant No 2011/01/B/ST3/00425.

NOTE: The U-shaped body is made of 416-grade stainless steel, which is stiff and has a low coefficient of thermal expansion (CTE), ~9.9 &#956;m/(m&#8729;&#176;C), as compared to ~17.3 &#956;m/(m&#8729;&#176;C) for 304-grade stainless steel.
1. Mechanical uniaxial-strain device
<ol>
	<li>Clean the U-shaped device, the micrometer screws (1&#8211;72 corresponding to 72 rotations per inch), the Belleville spring disks, and the base plate by sonicating them separately in acetone first and then in...

<ol>
	<li>Paglione, J., Greene, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-temperature+superconductivity+in+iron-based+materials.">High-temperature superconductivity in iron-based materials.</a> Nature Physics. 6 (9), 645 (2010).</li><li>Keimer, B., Kivelson, S. A., Norman, M. R., Uchida, S., Zaanen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+quantum+matter+to+high-temperature+superconductivity+in+copper+oxides.">From quantum matter to high-temperature superconductivity in copper oxides.</a> Nature. 518, 179-186 (2015).</li><li>Anderson, P. 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D., Haghighirad, A. A., Rhodes, L. C., Hoesch, M., Kim, T. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gigantic+anisotropic+uniaxial+pressure+effect+on+superconductivity+within+the+CuO2+plane+of+La1.64Eu0.2Sr0.16CuO4:+Strain+control+of+stripe+criticality.">Gigantic anisotropic uniaxial pressure effect on superconductivity within the CuO2 plane of La1.64Eu0.2Sr0.16CuO4: Strain control of stripe criticality.</a> Journal of the Physical Society of Japan. 73 (5), 1123-1126 (2004).</li><li>Kuo, H. -. H., Shapiro, M. C., Riggs, S. C., Fisher, I. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+the+elastoresistivity+coefficients+of+the+underdoped+iron+arsenide+Ba(Fe0.975Co0.025)2As2.">Measurement of the elastoresistivity coefficients of the underdoped iron arsenide Ba(Fe0.975Co0.025)2As2.</a> Physical Review B. 88 (8), 085113 (2013).</li><li>He, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dichotomy+between+in-plane+magnetic+susceptibility+and+resistivity+anisotropies+in+extremely+strained+BaFe2As2.">Dichotomy between in-plane magnetic susceptibility and resistivity anisotropies in extremely strained BaFe2As2.</a> Nature Communications. 8 (1), 504 (2017).</li><li>Engelmann, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strain+induced+superconductivity+in+the+parent+compound+BaFe2As2.">Strain induced superconductivity in the parent compound BaFe2As2.</a> Nature Communications. 4 (2877), 2877 (2013).</li><li>Berger, A. 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N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Temperature Driven Topological Switch in 1T’-MoTe2 and Strain Induced Nematicity in NaFeAs. , (2018).</li><li>B&#246;hmer, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+biaxial+strain+on+the+phase+transitions+of+Ca(Fe1&#8722;xCox)2As2.">Effect of biaxial strain on the phase transitions of Ca(Fe1&#8722;xCox)2As2.</a> Physical Review Letters. 118 (10), 107002 (2017).</li><li>Bao, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tunable+(&#948;+&#960;,+&#948;+&#960;)-type+antiferromagnetic+order+in+&#945;-Fe(Te,Se)+superconductors.">Tunable (&#948; &#960;, &#948; &#960;)-type antiferromagnetic order in &#945;-Fe(Te,Se) superconductors.</a> Physical Review Letters. 102 (24), 247001 (2009).</li><li>Koz, C., R&#246;&#223;ler, S., Tsirlin, A. 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All operations required to move the samples into and inside the STM are carried out using sets of arm manipulators. The STM is maintained at low temperatures by liquid nitrogen and liquid helium, and the sample cools down for at least 12 h before being approached. This allows the sample and microscope temperature to reach thermal equilibrium. To isolate electric and acoustic noise, the STM is placed in an acoustic and radio frequency shielded room. The microscope head is further suspended from springs for optimized instr...

High-temperature superconductivity in cuprates and iron-based superconductors is an intriguing state of quantum matter1,2. A major challenge in understanding superconductivity is the locally intertwined nature of various broken symmetry states, such as electronic nematic and smectic phases (that break rotational and translational symmetries of the electronic states), with superconductivity3,4,5,6,7. Manipulation and deliberate tuning of these broken symmetry states is a key objective toward understanding and controlling superconductivity.
Controlled strain, both uniaxial and biaxial, is a well-established technique to tune the collective electronic states in condensed matter systems8,9,10,11,12,13,14,15,16,17,18,19,20,21,22. This clean tuning, without the introduction of disorder through chemical doping, is commonly used in various kinds of experiments to tune bulk electronic properties23,24,25,26. For example, uniaxial pressure has proved to have an immense effect on superconductivity in Sr2RuO413 and cuprates27 and on the structural, magnetic, and nematic phase transitions of iron-based superconductors10,14,28,29 and was recently demonstrated in tuning the topological states of SmB624. However, the use of strain in surface-sensitive techniques, such as STM and angle-resolved photoemission spectroscopy (ARPES), has been limited to in situ-grown thin films on mismatched substrates26,30. The major challenge with applying strain to single crystals in surface-sensitive experiments is the need to cleave the strained samples in ultrahigh vacuum (UHV). In the last few years, an alternative direction has been to epoxy a thin sample on piezo stacks9,10,18,31 or on plates with different coefficients of thermal expansion19,32. Yet in both cases, the magnitude of the applied strain is quite limited.
Here we demonstrate the use of a novel mechanical uniaxial-strain device that allows researchers to strain a sample (compressive strain) without constraints and simultaneously visualize its surface structure using STM (see Figure 1). As an example, we use single crystals of Fe1+yTe, where y = 0.10, the parent compound of the iron chalcogenide superconductors (y is the excess iron concentration). Below TN = ~60 K, Fe1+yTe transitions from a high-temperature paramagnetic state into a low-temperature antiferromagnetic state with a bicollinear stripe magnetic order26,33,34&#160;(see Figure 3A,B). The magnetic transition is further accompanied by a structural transition from tetragonal to monoclinic26,35. The in-plane AFM order forms detwinned domains with the spin structure pointing along the long b-direction of the orthorhombic structure34. By visualizing the AFM order with spin-polarized STM, we probe the bidirectional domain structure in unstrained Fe1+yTe samples and observe their transition into a single large domain under applied strain (see the schematic in Figure 3C-E). These experiments show the successful surface tuning of the single crystals using the uniaxial-strain device presented here, the cleaving of the sample, and the simultaneous imaging of its surface structure with the scanning tunneling microscope. Figure 1 shows the schematic drawings and pictures of the mechanical strain device.

<table border="0" cellpadding="0" cellspacing="0" style="width:668px;" width="668">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Belleville spring disks</td>
			<td style="width:167px;">McMaster Carr</td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Fe(1.1)Te</td>
			<td style="width:167px;"></td>
			<td style="width:119px;"></td>
			<td>Single Crystal</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">H20E</td>
			<td style="width:167px;">Epoxy Technology</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">H74F</td>
			<td style="width:167px;">Epoxy Technology</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micrometer screws</td>
			<td style="width:167px;">McMaster Carr</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Stainless Steel sheets (416)</td>
			<td style="width:167px;">McMaster Carr</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

visualizing uniaxial-strain manipulation of antiferromagnetic domains in fe1+yte using a spin-polarized scanning tunneling microscope

The quest to understand correlated electronic systems has pushed the frontiers of experimental measurements toward the development of new experimental techniques and methodologies. Here we use a novel home-built uniaxial-strain device integrated into our variable temperature scanning tunneling microscope that enables us to controllably manipulate in-plane uniaxial strain in samples and probe their electronic response at the atomic scale. Using scanning tunneling microscopy (STM) with spin-polarization techniques, we visualize antiferromagnetic (AFM) domains and their atomic structure in Fe1+yTe samples, the parent compound of iron-based superconductors, and demonstrate how these domains respond to applied uniaxial strain. We observe the bidirectional AFM domains in the unstrained sample, with an average domain size of ~50-150 nm, to transition into a single unidirectional domain under applied uniaxial strain. The findings presented here open a new direction to utilize a valuable tuning parameter in STM, as well as other spectroscopic techniques, both for tuning the electronic properties as for inducing symmetry breaking in quantum material systems.

STM topographs were measured in constant current mode with a setpoint bias of -12 meV applied to the sample and a setpoint current of -1.5 nA collected on the tip. Pt-Ir tips were used in all experiments. To achieve spin-polarized STM, the scanning tunneling microscope tip has to be coated with magnetic atoms, which can be quite challenging. In this case of studying Fe1+yTe, the sample itself provides a simple means of achieving this. The excess irons (y...

Watch this Scientific Journal Video about Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope at JoVE.com

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

Using uniaxial strain combined with spin-polarized scanning tunneling microscopy, we visualize and manipulate the antiferromagnetic domain structure of Fe1+yTe, the parent compound of iron-based superconductors.

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

The quest to understand correlated electronic systems has pushed the frontiers of experimental measurements toward the development of new experimental ...

This protocol is significant because it is a visualization of the integration of the uniaxial-strain device with scanning tunneling microscopy. It involves both applying strain and visualizing the manipulation of structural domains in SDM. The main advantage of this technique is it allows for increased amounts of strain since it's a mechanical device.It's surface effects are able to be visualized using scanning tunneling microscopy. In high temperature superconductors by deliberately tuning and manipulating broken symmetry states, one can control and understand superconductivity. This process can be applied to any material provided it's a single crystal and it is SDM-compatible.There's a lot of device testing to determine the set-up's response to varying conditions including how much strain can be achieved. It's a very challenging experiment where patience and absolute understanding of what you are doing is key. Visual demonstration of this process is critical, as it gives an insight into making and using the described device with SDM which is a complex process.To begin, disassemble the u-shaped device and place it into acetone. Clean the device, the micrometer screws, the Belleville spring discs, and the base plate by sonicating them for 20 minutes. Then, transfer them into isopropanol and sonicate them for an additional 20 minutes.Once clean, bake the device components in an oven for 15 to 20 minutes to get rid of any water residue and to degas. Then, using a sharp razor blade, cut the iron tellurium sample to one millimeter by two millimeters by 0.1 millimeters in size. Finally, assemble the parts together.The opening inside the u is one millimeter and can be tuned smaller or large by a pair of micrometer screws located on the sides of the device. In two separate dishes, mix silver epoxy and non-conductive epoxy according to the instructions on the epoxy data sheets. Then, apply a thin layer of silver epoxy to create an electrical contact and mount the sample across the one millimeter gap so that its long axis is oriented along the b axis of the iron tellurium sample.Place the sample holder and sample into a convection oven and bake them for 15 minutes to again cure the epoxy. Once the sample has cooled, cover its two sides with non-conductive epoxy so that the sample is firmly supported on the device. Then, place it back into the oven to cure the epoxy.Using an optical microscope, examine the position of the sample from all angles to check for parallel alignment of the sides of the sample with the gap. With everything now prepared, begin to apply compressive strain by rotating the micrometer screw 50 degrees while observing the surface of the sample. There should be no cracks or bending of the sample after the pressure is applied.Next, screw the device into the base plate. Once secured, apply a thin layer of silver epoxy from the base plate onto the u-shaped device to create electrical contact between the sample and the plate. Place the sample into the oven to cure the epoxy.Once cooled, check the electrical contact using a multimeter. Then, use a thin layer of non-conducting epoxy to glue an aluminum post onto the sample so that it is perpendicular to the ab cleaving plane. The posts should be the same size as the sample.When the post is correctly positioned, bake the assembled device until the epoxy is cured. First, transfer the device to the scanning tunneling microscope by placing it into the loading dock of the variable temperature, ultra-high vacuum scanning tunneling microscope. Using an arm manipulator, knock off the aluminum post in ultra-high vacuum at room temperature to expose a freshly cleaved surface.Immediately transfer the device in situ with another set of manipulators to the scanning tunneling microscope chamber, enter the microscope head, which has been cooled down to nine degrees Calvin. Allow the sample to cool down to nine degrees overnight before carrying out the next steps and maintain this temperature during the experiments. Once the temperature equilibrium has been reached, prepare the platinum iridium tips prior to each experiment by field emission on a one one one copper surface that has been treated with several rounds of sputtering and annealing.Using the voltage applied to the piezo electric materials in the microscope, move the sample stage to align with the tip. Then approach the sample. Once the tip is a few angstroms away from the sample and the tunneling current registers on the oscilloscope, it is ready for taking topographs.Here is a 10 nanometer atomic resolution topographical image of an unstrained iron tellurium single crystal. The atomic structure seen corresponds to the tellurium atoms which are exposed after cleaving the sample. The 4DA transform of the topography shows four sharp peaks at the corners of the image along the a and b directions that correspond to the atomic Bragg peaks.In contrast to the first image, this topographical image shows a topograph obtained with a magnetic tip. Unidirectional stripes with a periodicity of twice that of the lattice along the a axis are observed. The 4DA transform of this topograph shows in addition to the Bragg peaks, a new pair of satellite peaks, corresponding to half the Bragg peak momenta and therefore twice the real space wavelength.The new structure corresponds to the AFM stripe order of the iron atoms just below the surface. On some parts of the unstrained sample twin domain boundaries exist where the crystal structure with the long b axis and the accompanying AFM stripe order rotate 90 degrees. Here you can observe a 25 nanometers topograph of an AFM twin domain boundary.The 4DA transform of this region shows two pairs of AFM order highlighted by green and yellow circles. Each magnetic domain contributes to only one pair of the peaks in the 4DA transform. For the strained sample, only one single domain can be seen as a result of the uniaxial pressure applied to the sample.Here, a large-scale topography is shown spanning a total region of approximately 1.75 microns by 0.75 microns which is more than twice the total area spanned in the unstrained samples. The 4DA transform for each topograph shows only one pair of AFM peaks indicating only a single domain on this strained sample. The most important thing to consider while attempting this procedure is your ultimate goal.Knowing why you're applying uniaxial strain should guide you as to the sample orientation and how much strain to apply. Following this procedure, a strain device could also be integrated with other techniques such as x-ray diffraction, resonant elastic x-ray scattering, and angular resolved photoemission spectroscopy. SDM's a powerful technique that enables one to visualize electrons in quantum materials.And these are materials that are very sensitive to external perturbations such as strain, so the uniaxial strain integrated SDM technique will allow one to electronically tune these materials and visualize the response to strain with the ultimate goal of understanding superconductivity.

visualizing-uniaxial-strain-manipulation-antiferromagnetic-domains

Research

JoVE Journal

Engineering

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface.
As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz&frac12; at 0.3 K 5.

Scanning-probe single-electron capacitance spectroscopy facilitates the study of single-electron motion in localized subsurface regions. A sensitive charge-detection circuit is incorporated into a cryogenic scanning probe microscope to investigate small systems of dopant atoms beneath the surface of semiconductor samples.

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Fabrication of Gate-tunable Graphene Devices for Scanning Tunneling Microscopy Studies with Coulomb Impurities

Owing to its relativistic low-energy charge carriers, the interaction between graphene and various impurities leads to a wealth of new physics and degrees of freedom to control electronic devices. In particular, the behavior of graphene&#8217;s charge carriers in response to potentials from charged Coulomb impurities is predicted to differ significantly from that of most materials. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) can provide detailed information on both the spatial and energy dependence of graphene&#39;s electronic structure in the presence of a charged impurity.&#160;The design of a hybrid impurity-graphene device, fabricated using controlled deposition of impurities onto a back-gated graphene surface, has enabled several novel methods for controllably tuning graphene&#8217;s electronic properties.1-8 Electrostatic gating enables control of the charge carrier density in graphene and the ability to reversibly tune the charge2 and/or molecular5 states of an impurity. This paper outlines the process of fabricating a gate-tunable graphene device decorated with individual Coulomb impurities for combined STM/STS studies.2-5 These studies provide valuable insights into the underlying physics, as well as signposts for designing hybrid graphene devices.

This paper details the fabrication process of a gate-tunable graphene device, decorated with Coulomb impurities for scanning tunneling microscopy studies. Mapping the spatially dependent electronic structure of graphene in the presence of charged impurities unveils the unique behavior of its relativistic charge carriers in response to a local Coulomb potential.

Owing to its relativistic low-energy charge carriers, the interaction between graphene and various impurities leads to a wealth of new physics and degrees ...

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

The optical, electrical, and structural properties of dislocations and of grain boundaries in semiconductor materials can be determined by experiments performed in a scanning electron microscope. Electron microscopy has been used to investigate cathodoluminescence, electron beam induced current, and diffraction of backscattered electrons.

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications ...

Hand Controlled Manipulation of Single Molecules via a Scanning Probe Microscope with a 3D Virtual Reality Interface

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building blocks in a bottom-up approach is still open. The scanning probe microscope (SPM) could be a tool of choice; however, SPM-based manipulation was until recently limited to two dimensions (2D). Binding the SPM tip to a molecule at a well-defined position opens an opportunity of controlled manipulation in 3D space. Unfortunately, 3D manipulation is largely incompatible with the typical 2D-paradigm of viewing and generating SPM data on a computer. For intuitive and efficient manipulation we therefore couple a low-temperature non-contact atomic force/scanning tunneling microscope (LT NC-AFM/STM) to a motion capture system and fully immersive virtual reality goggles. This setup permits &#34;hand controlled manipulation&#34; (HCM), in which the SPM tip is moved according to the motion of the experimenter&#39;s hand, while the tip trajectories as well as the response of the SPM junction are visualized in 3D. HCM paves the way to the development of complex manipulation protocols, potentially leading to a better fundamental understanding of nanoscale interactions acting between molecules on surfaces. Here we describe the setup and the steps needed to achieve successful hand-controlled molecular manipulation within the virtual reality environment.

We demonstrate the precise manipulation of individual organic molecules on a metal surface with the tip of a scanning probe microscope driven in 3D by the experimenter's hand using a motion capture system and fully immersive virtual reality goggles.

Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building ...

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

This protocol describes the operation of a liquid flow specimen holder for scanning transmission electron microscopy of AuNPs in water, as used for the observation of nanoscale dynamic processes.

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a ...

Scanning SQUID Study of Vortex Manipulation by Local Contact

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual vortices is necessary in order to study how vortices interact with each other, with the lattice, and with other magnetic objects. Here, we present a protocol for vortex manipulation in thin superconducting films by local contact, without applying current or magnetic field. Vortices are imaged using a scanning superconducting quantum interference device (SQUID), and vertical stress is applied to the sample by pushing the tip of a silicon chip into the sample, using a piezoelectric element. Vortices are moved by tapping the sample or sweeping it with the silicon tip. Our method allows for effective manipulation of individual vortices, without damaging the film or affecting its topography. We demonstrate how vortices were relocated to distances of up to 0.8 mm. The vortices remained stable at their new location up to five days. With this method, we can control vortices and move them to form complex configurations. This technique for vortex manipulation could also be implemented in applications such as vortex based logic devices.

We present a protocol for manipulation of individual vortices in thin superconducting films, using local mechanical contact. The method does not include applying current, magnetic field or additional fabrication steps.

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual ...

Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning electron microscope (ESEM) operating with a low pressure water vapor ambient. In this technique, a portion of the electron beam interacts with the water vapor in the vicinity of the CNT sample, dissociating the water molecules into hydroxyl radicals and other species by radiolysis. The remainder of the electron beam interacts with the CNT forest sample, making it susceptible to oxidation from the chemical products of radiolysis. This technique may be used to trim a selected region of an individual CNT, or it may be used to remove hundreds of cubic microns of material by adjusting ESEM parameters. The machining resolution is similar to the imaging resolution of the ESEM itself. The technique produces only small quantities of carbon residue along the boundaries of the cutting zone, with minimal effect on the native structural morphology of the CNT forest.

Low pressure scanning electron microscopy in a water vapor ambient is used to machine nanoscale to microscale features in carbon nanotube forests.

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning ...

Demonstration of a Hyperlens-integrated Microscope and Super-resolution Imaging

The use of super-resolution imaging to overcome the diffraction limit of conventional microscopy has attracted the interest of researchers in biology and nanotechnology. Although near-field scanning microscopy and superlenses have improved the resolution in the near-field region, far-field imaging in real-time remains a significant challenge. Recently, the hyperlens, which magnifies and converts evanescent waves into propagating waves, has emerged as a novel approach to far-field imaging. Here, we report the fabrication of a spherical hyperlens composed of alternating silver (Ag) and titanium oxide (TiO2) thin layers. Unlike a conventional cylindrical hyperlens, the spherical hyperlens allows for two-dimensional magnification. Thus, incorporation into conventional microscopy is straightforward. A new optical system integrated with the hyperlens is proposed, allowing for a sub-wavelength image to be obtained in the far-field region in real time. In this study, the fabrication and imaging setup methods are explained in detail. This work also describes the accessibility and possibility of the hyperlens, as well as practical applications of real-time imaging in living cells, which can lead to a revolution in biology and nanotechnology.

The use of a hyperlens has been regarded as a novel super-resolution imaging technique due to its advantages in real-time imaging and its simple implementation with conventional optics. Here, we present a protocol describing the fabrication and imaging applications of a spherical hyperlens.

The use of super-resolution imaging to overcome the diffraction limit of conventional microscopy has attracted the interest of researchers in biology and ...

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...