This effort was wholly supported by the US DOE, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.

1. Sample Growth Fabrication
<ol>
 <li>Clean a 5 mm x 5 mm x 0.5 mm single crystal substrate having a miscut angle &lt;0.1 degree such as SrTiO3 or LaAlO3 with acetone and then water in an ultrasonic cleaner for 10 min each. To get a TiO2 termination on SrTiO3, etch the substrate in 10% hydrogen fluoride for 30 sec and rinse in water for 1 min, followed by an anneal at 1,100 &deg;C for 10 hr. After cleaning, mount the substrate on a heater suitable for ultra-high vacuum conditions.</li>
 <li>Mount the heater into the PLD vacuum chamber and open the chamber oxygen source to fill the chamber with 2 x 10E-5 Torr oxygen. Raise the heater temperature to 800 &deg;C and allow it to anneal for 20 min. Temperature can be monitored using a computer controlled pyrometer or a thermocouple.</li>
 <li>To begin film deposition, start the excimer pulsed laser using a laser fluence of 1 to 2 J/cm2 and laser frequency of 1 or 2 Hz. The laser pulses will hit the target material and generate a plume flux. The flux will penetrate through the oxygen environment and deposit onto the substrate.</li>
 <li>Reflection High Energy Electron Diffraction (RHEED) can be used to monitor unit cell growth and confirm surface quality 7. This technique allows for very clear thickness monitoring.</li>
 <li>When the film is of the desired thickness, turn off the laser and decrease the heater temperature at 5 &deg;C/min. Once the heater is cooled to room temperature, turn off the oxygen source and remove the sample.</li>
 <li>Ex situ annealing can be used on oxide materials to remove oxygen deficiencies that may be present after growth or after long periods in vacuum. Place the sample in a tube furnace under 1 atm of flowing oxygen. Raise the temperature from 20 &deg;C to 700 &deg;C at 5 &deg;C/min, anneal for 2 hr, and then decrease temperature from 700 &deg;C to 20 &deg;C at 2 &deg;C/min. An important note is to never post-anneal at higher temperatures than those used during film growth when filling oxygen vacancies as this can adversely affect surface quality and may negatively influence crystal quality.</li>
</ol>
2. Photolithography Fabrication
<ol>
 <li>Ultrasonically clean the sample in acetone and then water for 10 min each. An optical microscope can be used to check that the sample surface is clean of large particulates. (Figure 2a)</li>
 <li>Spin coat a layer of 1 micron thick photoresist. Typical spin speed and duration are around 6,000 rpm and 80 sec though these numbers are dependent on specific photoresist used. Place the sample on a heat plate at 115 &deg;C for 2 min to cure the photoresist. Check the photoresist quality under an optical microscope. The coating should appear uniform with no bubbling.</li>
 <li>Use a mask aligner to expose the sample under a predefined lithography mask with UV light for 9 sec with an exposure dose around 90 mJ/cm2. Again these numbers will be specific to the photoresist used. When positive photoresist is used, the part of the photoresist which is covered by the mask will not change its chemical property while the part of the PR which is uncovered by the mask will change its property and can be dissolved in the chemical developer. Heat the photoresist and sample at 110 &deg;C for 80 sec to further cure the exposed photoresist.</li>
 <li>Rinse the sample in a developer solution for 25-35 sec. Take out the sample immediately and rinse in water for 30 sec. If positive photoresist is used, the part of photoresist which is uncovered by the mask will be washed away while the part which is covered will remain. Note that the duration of the developing step is crucial to accurately control photoresist dimensions and quality (Figure 2b).</li>
 <li>Prepare a solution of potassium iodide, hydrochloric acid and water of ratio 1:1:1. Use plastic tweezers to rinse the sample in the acid for approximately 10 sec. The unprotected part of the thin film will be etched away. Immediately rinse the sample in pure water for 60 sec. Check with an optical microscope to see if the thin film has been totally etched. If not, add 2 to 3 more seconds of acid etch and immediately rinse with pure water, then check again with an optical microscope. Repeat this procedure until all the unprotected film is etched away. This process is governed by the etchant strength and film thickness. Typical etch rates for many manganites are about 1-4 nm/second for the 1:1:1 solution ratio described above.</li>
 <li>Rinse the sample in acetone for 20 sec to remove the remaining photoresist. Check the quality of sample with microscope (Figure 2c and 2d).</li>
</ol>
3. Wire-bonding Connection
<ol>
 <li>Using a photo-mask, repeat the steps 2.1-2.3 above using a lithography mask that will leave open regions on the wires suitable for contact pads. Evaporate 5 nm Ti and 100 nm Au onto the sample and rinse in acetone. This will remove the photoresist and leave only the desired contact pad geometry (Figure 3a).</li>
 <li>Use GE varnish to mount the sample onto the sample puck. Allow 15 min to cure.</li>
 <li>Fix the sample position on wire bonder stage and use the wire bonder to connect Al wires from the sample puck to Ti/Au contacts (Figure 3b). Then perform electrical measurements.</li>
</ol>

<ol>
	<li>Ahn, C. H., Triscone, J. -. M., Mannhart, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electric+field+effect+in+correlated+oxide+systems.">Electric field effect in correlated oxide systems.</a> Nature. 424, 1015-1018 (2003).</li><li>Basov, D. N., Averitt, R. D., Van der Marel, D., Dressel, M., Haule, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrodynamics+of+correlated+electron+materials.">Electrodynamics of correlated electron materials.</a> Reviews of Modern Physics. 83, 471-541 (2011).</li><li>Waser, R., Aono, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoionics-based+resistive+switching+memories.">Nanoionics-based resistive switching memories.</a> Nat. Mater. 6, 833-840 (2007).</li><li>Willmott, P. R., Huber, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulsed+laser+vaporization+and+deposition.">Pulsed laser vaporization and deposition.</a> Rev. Mod. Phys. 72, 315-328 (2000).</li><li>Eres, H. M. C., G, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+pulsed-laser+deposition+of+complex+oxides.">Recent advances in pulsed-laser deposition of complex oxides.</a> Journal of Physics: Condensed Matter. 20, 264005 (2008).</li><li>Ding, J. F., Jin, K. X., Zhang, Z., Wu, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dependence+of+negative+differential+resistance+on+electronic+phase+separation+in+unpatterned+manganite+films.">Dependence of negative differential resistance on electronic phase separation in unpatterned manganite films.</a> Applied Physics Letters. 100, 62402-62404 (2012).</li><li>Ichimiya, A., I, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Reflection High Energy Electron Diffraction. , (2004).</li><li>Guo, H., Sun, D., 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=Growth+diagram+of+La0.7Sr0.3MnO3+thin+films+using+pulsed+laser+deposition.">Growth diagram of La0.7Sr0.3MnO3 thin films using pulsed laser deposition.</a> arXiv. , 1210.5989 (2012).</li><li>Ward, T. Z., Gai, Z., Guo, H. W., Yin, L. F., Shen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+a+first-order+electronic+phase+transition+in+manganites.">Dynamics of a first-order electronic phase transition in manganites.</a> Physical Review B. 83, 125125 (2011).</li><li>Ward, T. Z., Liang, S., 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=Reemergent+Metal-Insulator+Transitions+in+Manganites+Exposed+with+Spatial+Confinement.">Reemergent Metal-Insulator Transitions in Manganites Exposed with Spatial Confinement.</a> Physical Review Letters. 100, 247204 (2008).</li><li>Ward, T. Z., Zhang, X. G., 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=Time-Resolved+Electronic+Phase+Transitions+in+Manganites.">Time-Resolved Electronic Phase Transitions in Manganites.</a> Physical Review Letters. 102, 87201 (2009).</li><li>Zhai, H. -. Y., Ma, J. X., 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=Giant+Discrete+Steps+in+Metal-Insulator+Transition+in+Perovskite+Manganite+Wires.">Giant Discrete Steps in Metal-Insulator Transition in Perovskite Manganite Wires.</a> Physical Review Letters. 97, 167201 (2006).</li><li>Wu, T., Mitchell, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Creation+and+annihilation+of+conducting+filaments+in+mesoscopic+manganite+structures.">Creation and annihilation of conducting filaments in mesoscopic manganite structures.</a> Physical Review B. 74, 214423 (2006).</li><li>Altissimo, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=E-beam+lithography+for+micro-/nanofabrication.">E-beam lithography for micro-/nanofabrication.</a> Biomicrofluidics. 4, 26503-26506 (2010).</li><li>Watt, F., Bettiol, A. A., Van Kan, J. A., Teo, E. J., Breese, M. B. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ion+Beam+Lithography+and+Nanofabrication:+A+Review.">Ion Beam Lithography and Nanofabrication: A Review.</a> International Journal of Nanoscience. 4, 269-286 (2005).</li><li>Urban, J. J., Yun, W. S., Gu, Q., Park, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+single-crystalline+perovskite+nanorods+composed+of+barium+titanate+and+strontium+titanate.">Synthesis of single-crystalline perovskite nanorods composed of barium titanate and strontium titanate.</a> J. Am. Chem. Soc. 124, 1186-1187 (2002).</li><li>Wang, Y., Fan, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+origin+of+different+magnetic+properties+in+nanosized+Ca0.82La0.18MnO3:+Wires+versus+particles.">The origin of different magnetic properties in nanosized Ca0.82La0.18MnO3: Wires versus particles.</a> Applied Physics Letters. 98, 142502 (2011).</li></ol>

No conflicts of interest declared.

Unlike single element semiconducting materials such as Si, the fabrication of complex materials can be more difficult due to the fact that the complex structure and multiple elements must all be taken into consideration. The use of photolithography to fabricate complex oxide devices is relatively low cost and fast to prototype as opposed to other confinement techniques. There are however some important limitations to understand. Photolithography has a spatial limitation to creating structures of about 1 micron so is not ...

The first and one of the most important steps towards high quality devices is the growth of epitaxial oxide thin films. A single crystal substrate is used as a "template" to deposit the target materials. Among different deposition methods, pulsed laser deposition (PLD) is one of the best ways to acquire good quality thin films 4,5. The growth processes involve heating the substrate to around 800 &deg;C in an oxygen environment and using laser pulses to hit the target material and generate a flux to be deposited onto the substrate. The typical system is shown in Figure 1.
While unpatterned films have been shown to reveal exotic new physics 6, reducing film dimension provides more opportunities to explore new phenomena and device fabrication. Photolithography can be used to shrink the in-plane sample dimension down to the order of 1 &mu;m. The detailed protocol of the photolithography process will be discussed below. This technique is compatible with most widely used substrates which allows for investigations of confinement effects on epitaxial films held at different strain states.
Since many complex oxides have interesting characteristics at low temperatures and/or high magnetic fields, the electronic connection between the device and measurement equipment is very important. High quality contacts can be formed by evaporating Au contact pads in a 4-probe geometry and with the use of a wire bonder to make connections between the pads and measurement device. When done correctly, these connections can easily withstand extreme measurement environments within wide temperature ranges of 4 K to 400 K and magnetic field ranges of up to &plusmn; 9 T.

<table border="1">
 <tbody>
 <tr>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>Reagent/Material</td>
 </tr>
 <tr>
 <td>SrTiO3(001) &amp; LaAlO3(100) substrates</td>
 <td>CrysTec GmbH</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Microposit S1813 Photoresist</td>
 <td>Shipley</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>CD-26 Developer</td>
 <td>Shipley</td>
 <td>38490</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>GE varnish</td>
 <td>Lakeshore</td>
 <td>VGE-7031</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>Equipment</td>
 </tr>
 <tr>
 <td>Reflected High Energy Electron Diffraction (RHEED)</td>
 <td>Staib Instruments</td>
 <td>&nbsp;</td>
 <td>35 kV TorrRHEED</td>
 </tr>
 <tr>
 <td>Mask Aligner</td>
 <td>ABM</td>
 <td>Model 85-3 (350 W) Lightsource</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Resistivity Puck</td>
 <td>Quantum Design</td>
 <td>P102</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Wire Bonder</td>
 <td>Kulicke &amp; Soffa</td>
 <td>04524-0XDA-000-00</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
</table>

fabrication of spatially confined complex oxides

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from the inherent strong electron correlations that reside within them. These materials can also possess electronic phase separation in which regions of vastly different resistive and magnetic behavior can coexist within a single crystal alloy material. By reducing the scale of these materials to length scales at and below the inherent size of the electronic domains, novel behaviors can be exposed. Because of this and the fact that spin-charge-lattice-orbital order parameters each involve correlation lengths, spatially reducing these materials for transport measurements is a critical step in understanding the fundamental physics that drives complex behaviors. These materials also offer great potential to become the next generation of electronic devices 1-3. Thus, the fabrication of low dimensional nano- or micro-structures is extremely important to achieve new functionality. This involves multiple controllable processes from high quality thin film growth to accurate electronic property characterization. Here, we present fabrication protocols of high quality microstructures for complex oxide manganite devices. Detailed descriptions and required equipment of thin film growth, photo-lithography, and wire-bonding are presented.

This paper focuses mostly on the photolithography and wire-bonding aspects of sample preparation. More details on film growth procedures can be found in our other recent publications 8.
Photolithography is an important method to control dimensionality in complex oxides for the purpose of investigating electron correlation lengths and electronic phase separation 9-13. Figure 2 shows optical images of partial steps during the process. It is necessary to poi...

Watch this Scientific Journal Video about Fabrication of Spatially Confined Complex Oxides at JoVE.com

Fabrication of Spatially Confined Complex Oxides

We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from ...

fabrication-of-spatially-confined-complex-oxides

Research

JoVE Journal

Engineering

9.4K Views.  Oak Ridge National Laboratory. We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

Video: Fabrication of Spatially Confined Complex Oxides

Measuring Spatially- and Directionally-varying Light Scattering from Biological Material

Light interacts with an organism's integument on a variety of spatial scales. For example in an iridescent bird: nano-scale structures produce color; the milli-scale structure of barbs and barbules largely determines the directional pattern of reflected light; and through the macro-scale spatial structure of overlapping, curved feathers, these directional effects create the visual texture. Milli-scale and macro-scale effects determine where on the organism's body, and from what viewpoints and under what illumination, the iridescent colors are seen. Thus, the highly directional flash of brilliant color from the iridescent throat of a hummingbird is inadequately explained by its nano-scale structure alone and questions remain. From a given observation point, which milli-scale elements of the feather are oriented to reflect strongly? Do some species produce broader "windows" for observation of iridescence than others? These and similar questions may be asked about any organisms that have evolved a particular surface appearance for signaling, camouflage, or other reasons.
In order to study the directional patterns of light scattering from feathers, and their relationship to the bird's milli-scale morphology, we developed a protocol for measuring light scattered from biological materials using many high-resolution photographs taken with varying illumination and viewing directions. Since we measure scattered light as a function of direction, we can observe the characteristic features in the directional distribution of light scattered from that particular feather, and because barbs and barbules are resolved in our images, we can clearly attribute the directional features to these different milli-scale structures. Keeping the specimen intact preserves the gross-scale scattering behavior seen in nature. The method described here presents a generalized protocol for analyzing spatially- and directionally-varying light scattering from complex biological materials at multiple structural scales.

We present a non-destructive method for sampling spatial variation in the direction of light scattered from structurally complex materials. By keeping the material intact, we preserve gross-scale scattering behavior, while concurrently capturing fine-scale directional contributions with high-resolution imaging. Results are visualized in software at biologically-relevant positions and scales.

Light interacts with an organism's integument on a variety of spatial scales. For example in an iridescent bird: nano-scale structures produce color; the ...

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic (VES) fluids. The measurements are made for particles settling in unbounded fluids&#160;and fluids between parallel walls. VES fluids over a wide range of rheological properties are prepared and rheologically characterized. The rheological characterization involves steady shear-viscosity and dynamic oscillatory-shear measurements to quantify the viscous and elastic properties respectively. The settling velocities under unbounded conditions are measured in beakers having diameters at least 25x the diameter of particles. For measuring settling velocities between parallel walls, two experimental cells with different wall spacing are constructed. Spherical particles of varying sizes are gently dropped in the fluids and allowed to settle. The process is recorded with a high resolution video camera and the trajectory of the particle is recorded using image analysis software. Terminal settling velocities are calculated from the data.
The impact of elasticity on settling velocity in unbounded fluids is quantified by comparing the experimental settling velocity to the settling velocity calculated by the inelastic drag predictions of Renaud et al.1&#160;Results show that elasticity of fluids can increase or decrease the settling velocity. The magnitude of reduction/increase is a function of the rheological properties of the fluids and properties of particles. Confining walls are observed to cause a retardation effect on settling and the retardation is measured in terms of wall factors.

This paper demonstrates the experimental procedure to measure terminal settling velocities of spherical particles in surfactant-based shear thinning viscoelastic fluids. Fluids over a wide range of rheological properties are prepared and settling velocities are measured for a range of particle sizes in unbounded fluids and fluids between parallel walls.

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Atomically Traceable Nanostructure Fabrication

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure.

We report a protocol for combining the atomic metrology of the Scanning Tunneling Microscope for surface patterning with selective Atomic Layer Deposition and Reactive Ion Etching. Using a robust process involving numerous atmospheric exposures and transport, 3D nanostructures with atomic metrology are fabricated.

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process ...

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.

We demonstrate the fabrication of periodic gold nanocup arrays using colloidal lithographic techniques and discuss the importance of nanoplasmonic films.

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing ...

Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental sciences and industrial applications owing to their periodic arrangement of nanopores with relatively high aspect ratio. However, the techniques reported so far, which could be only valid for mono-surface anodization, show critical disadvantages, i.e., time-consuming as well as complicated procedures, requiring toxic chemicals, and wasting valuable natural resources. In this paper, we demonstrate a facile, efficient, and environmentally clean method to fabricate nanoporous AAOs in sulfuric and oxalic acid electrolytes, which can overcome the limitations that result from conventional AAO fabricating methods. First, plural AAOs are produced at one time through simultaneous multi-surfaces anodization (SMSA), indicating mass-producibility of the AAOs with comparable qualities. Second, those AAOs can be separated from the aluminum (Al) substrate by applying stair-like reverse biases (SRBs) in the same electrolyte used for the SMSAs, implying simplicity and green technological characteristics. Finally, a unit sequence consisting of the SMSAs sequentially combined with SRBs-based detachment can be applied repeatedly to the same Al substrate, which reinforces the advantages of this strategy and also guarantees the efficient usage of natural resources.

A protocol for fabricating nanoporous anodic aluminum oxides via simultaneous multi-surfaces anodization followed by stair-like reverse biases detachments is presented. It can be applied repeatedly to the same aluminum substrate, exhibiting a facile, high-yield, and environmentally clean strategy.

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental ...

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in industry. The wettability of the produced surface was analyzed by bouncing drop experiments and the topography was analyzed by confocal microscopy. In addition, we show various methodologies to measure its durability and anti-icing properties. Superhydrophobic surfaces hold a special texture that must be preserved to keep their water-repellency. To fabricate durable surfaces, we followed two strategies to incorporate a resistant texture. The first strategy is a direct incorporation of roughness to the metal substrate by acid etching. After this surface texturization, the surface energy was decreased by silanization or fluoropolymer deposition. The second strategy is the growth of a ceria layer (after surface texturization) that should enhance the surface hardness and corrosion resistance. The surface energy was decreased with a stearic acid film.
The durability of the superhydrophobic surfaces was examined by a particle impact test, mechanical wear by lateral abrasion, and UV-ozone resistance. The anti-icing properties were explored by studying the ability to repeal subcooled water, freezing delay, and ice adhesion.

We illustrate several methodologies to produce superhydrophobic metal surfaces and to explore their durability and anti-icing properties.

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in ...

Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.

The synthesis of high quality bulk and thin film (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O entropy-stabilized oxides is presented.

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and ...