SDJ gratefully acknowledges the support of the American Association for Engineering Education/NRL Postdoctoral Fellowship Program, discussions with Konrad Bussmann (NRL) and Mingzhong Wu (Colorado State University) on the magnetic properties of materials, and Ron Holm (NRL) for his part in the design and implementation of the NRL AD system.

1. Powder Preparation
<ol>
	<li>Sieve as-received yttrium iron garnet (YIG) powder to obtain 100&#8211;150 g of agglomerates sized less than 53 &#181;m.</li>
	<li>Place the sieved powder into a furnace to dry for at least 24 hr at a temperature greater than 300 &#176;C.</li>
</ol>
2. Substrate Preparation
<ol>
	<li>Clean a substrate of desired size, e.g., 3 mm x 3 mm using acetone then isopropanol. Dry using nitrogen gas.</li>
</ol>
3. Performing Aerosol Deposition
<ol>
	<li>Mount the sample to the translation mounting stage.
	<ol>
		<li>Place double-sided copper tape to the mounting stage. Place the cleaned substrate onto the copper tape.</li>
		<li>Measure the distance from the edge of the mounting stage to each edge of the sample. Record the dimensions and sample position on the sample history sheet.</li>
		<li>Check that the mounting stage is aligned parallel with the body of the translation motor by measuring the distance from the edge of the mounting stage to the edge of the motor body with calipers. Load the sample into the deposition chamber.</li>
		<li>Clamp the flange to seal the deposition chamber. Attach the 3 15-pin D-sub controller cables for the translation motors.</li>
	</ol>
	</li>
	<li>Load the powder and close up the aerosol chamber.
	<ol>
		<li>Remove the dried powder from the furnace and place it in the aerosol chamber bottom section. Slide the filter de-clogging rod attachment onto the filter de-clogging rod.</li>
		<li>Place the main body of the aerosol chamber onto the aerosol chamber bottom section. Allow the filter de-clogging rod attachment to rest on the agitation plate as the main body is being attached to the bottom section.</li>
		<li>Clamp the main body to the bottom section. Attach the aerosol chamber pressure gauge to the side port on the main body of the aerosol chamber.</li>
		<li>Clamp the nozzle inlet section to the top port on the main body of the aerosol chamber using a QF clamp. Raise the nozzle inlet tube to the inlet port on the deposition chamber and secure the top and bottom fitting.</li>
		<li>Record the powder and aerosol chamber identification numbers on the sample history sheet.</li>
	</ol>
	</li>
	<li>Turn on the roughing pump with it isolated from the rest of the system. Turn on the deposition chamber illumination lamp. Open the constriction valve on the bypass line to begin the pump-down of the entire system.</li>
	<li>Setup the pressure monitoring software with the deposition run identification.</li>
	<li>Run the stage controller macro creator by typing &#8216;pitrans&#8217; in the command line terminal window and enter the requested information. Create a new sheet in the run log spreadsheet and record the deposition parameters and setup notes.</li>
	<li>After the system pressure has reached about 150&#8211;200 Torr, slightly open the unconstricted valve. Maintain a pump-down rate of about 1 Torr/sec. Once the pressure has dropped below 100 Torr start the pressure monitoring software and the translation stage motor controller software.</li>
	<li>Once the system pressure has reached about 1 Torr close all three valves to the bypass line and open the main pumping valve. Tighten the clamp to the top cap on the deposition chamber.</li>
	<li>Turn on the blower pump. Open the ultra-high purity (UHP) nitrogen gas cylinder. Monitor the pressure and record the base pressure of the system (it typically reaches 15&#8211;25 mTorr).</li>
	<li>Set the distance between the nozzle and the substrate. Use the stage controller software graphical user interface window to move the mounted substrate over the nozzle. Lower the substrate until it contacts the nozzle. Move the substrate 7.5 mm in the vertical direction from this position.</li>
	<li>Close the main pumping line and monitor the leak rate of the system on the pressure monitoring software. Note the initial leak rate upon shutting the valve. If this leak rate is less than 3.33 mTorr/sec continue, otherwise begin checking for leaks. A typical leak rate is less than 1.2 mTorr/sec.</li>
	<li>Set the deposition chamber butterfly valve to the 500 Torr preset value. Set the mass flow controller value to 13.63 L/min (do not turn it on).</li>
	<li>Move the mounting stage to the starting position for the deposition. Load the macro created in step 3.7 into the controller software.</li>
	<li>Program the function generator to sweep linearly between 135 and 145 Hz every 10 sec. Turn the function generator on. Turn the nitrogen gas flow on. After a 3 sec countdown start the stage controller macro.</li>
	<li>Monitor the deposition and adjust gas flow rate as necessary to keep the pressure difference at 500 &#177; 0.5 Torr (or as desired for the run) for the duration of the deposition. 
	Note: The pressure in the deposition chamber is typically 0.65 Torr and the pressure in the deposition chamber is typically 501 Torr. Uncontrollable variations in pressure usually indicate that the UHP nitrogen is running out. A slight drop in pressure (1&#8211;2 Torr) over the duration of the run is typical. This can be remedied by increasing the gas flow rate. During the initial passes a visible film should form on the substrate, lack of film formation suggests insufficient aerosolization of the powder and/or significant filter clogging.</li>
	<li>At the end of the deposition note the exact deposition run time. Shut off the nitrogen gas, the function generator, and the pumps. Open the deposition chamber butterfly valve completely.</li>
	<li>Open the bypass valve located at the side of the deposition chamber. Turn the house nitrogen gas regulator to zero and redirect it into the deposition chamber. Close the main pumping valve while slowly increasing the house gas regulator pressure.</li>
	<li>Home the nozzle to X = 25 mm, Y = 25 mm, and Z = 25 mm, then close the stage controller software.</li>
	<li>Once the pressure in the system has risen above 100 Torr stop the pressure monitoring software. Record the total nitrogen gas used and time to complete the deposition.&#160;Adjust the house gas pressure as necessary until the system reaches atmosphere.</li>
	<li>Unplug the 3 15-pin D-sub stage controller cables and unclamp the top cap. Remove the top cap from the deposition chamber and unmount the sample.</li>
</ol>
4. Post-deposition Inspection
<ol>
	<li>Remove the sample from the mounting stage and inspect it under a microscope. If necessary, wash the sample in isopropanol to remove loose powder. Perform the planned characterizations of the film.</li>
</ol>

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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=Aerosol+Deposition+of+Yttrium+Iron+Garnet+for+Fabrication+of+Ferrite-Integrated+On-Chip+Inductors.">Aerosol Deposition of Yttrium Iron Garnet for Fabrication of Ferrite-Integrated On-Chip Inductors.</a> IEEE Trans. on Magnetics. 51 (05), (2015).</li><li>Johnson, S. D., Kub, F. J., Eddy, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ZnS/Diamond+Composite+Coatings+for+Infrared+Transmission+Applications+Formed+by+the+Aerosol+Deposition+Method.">ZnS/Diamond Composite Coatings for Infrared Transmission Applications Formed by the Aerosol Deposition Method.</a> Proceedings of SPIE. 8708, 87080T-87081T (2013).</li><li>Han, G., Ryu, J., Yoon, W. -. H., Choi, J. -. 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A. 19 (5), 2567-2570 (2001).</li><li>Sun, Y., 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+and+ferromagnetic+resonance+properties+of+nanometer-thick+yttrium.">Growth and ferromagnetic resonance properties of nanometer-thick yttrium.</a> Appl. Phys. Lett. 101 (15), 082405 (2012).</li><li>Kalarickal, S. S., Krivosik, P., Das, J., Kim, K. S., Patton, C. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microwave+damping+in+polycrystalline+Fe-Ti-N+films:+Physical+mechanisms+and+correlations+with+composition+and+structure.">Microwave damping in polycrystalline Fe-Ti-N films: Physical mechanisms and correlations with composition and structure.</a> Phys. Rev. B. 77, 054427 (2008).</li><li>Johnson, S. 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The authors have nothing to disclose.

The SEM image in Figure 4 indicates that significant fracture and densification is occurring during the deposition process. The image is taken of the top surface of the film, which shows a small number of voids and grains. The observable region is the last of the material to be deposited and therefore does not benefit from the further impact and densification process of subsequent particles as illustrated by impact from particle 2 and 3 in Figure 1. The film density within the volume of ...

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk1. The deposition process is believed to occur through a continual process of impact, fracture or deformation, adhesion, and densification of particles. Figure 1 depicts this process as a series of steps showing particle impact and densification over several steps. As shown, the particles move toward the substrate with a typical velocity of 100&#8211;500 m/sec. As the initial particles impact with the substrate they fracture and adhere to the substrate. This anchoring layer provides the mechanical adhesion between the substrate and the bulk film. As subsequent impacts occur the underlying particles are increasingly fractured, adhered, and further densified. This process of continual impact, fracture, and densification works to compact the underlying film and bond the crystallites and produce a film with a density reaching greater than 95% of the bulk material.
<img alt="Figure 1" src="/files/ftp_upload/52843/52843fig1.jpg" /> 
Figure 1. Illustration of the deposition process. Panel A shows three particles moving toward the substrate with a typical velocity of 100&#8211;500&#160;m/sec. Panel B shows the result of impact, fracture, and adhesion of the first particle. Panels C and D show the subsequent impact of the second and third particles, which further compact the underlying film and bond the crystallites. The result is a film with density greater than 95% of the bulk material (reproduced with permission from Reference 19). <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/52843/52843fig1highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The primary advantage of AD is that the deposition takes place entirely at ambient RT; thereby enabling film growth, for instance, of a high-melting-temperature material (starting powder) onto a low-melting-temperature substrate. The deposition rate can be up to several micrometers per minute and is performed at moderate vacuum conditions of 1&#8211;20 Torr in the deposition chamber. The process shows the ability to scale up to very large deposition areas and finally, it can deposit conformally.2
There are many material systems studied by AD for a wide variety of uses, such as inductors3, abrasion-resistant coatings4, piezoelectrics5, multiferroics6, magnetoelectrics7 thermistors8, thermoelectric films9, flexible dielectrics10, hard tissue implants and bioceramics11, solid electrolytes12, and photocatalysts13. For applications to microwave devices, magnetic films of several hundreds of micrometers in thickness are required that would ideally be integrated directly into the circuit board elements. One challenge to realizing this integration is the high-temperature regime needed for fabricating ferrite films (see review by Harris et al.14), such as yttrium iron garnet (YIG). For this reason AD appears to be a natural choice for realizing potential new advancements in magnetic integrated circuit technology. The low-cost operation, high deposition rate, and simplicity of AD has spurred interest by researchers in Germany, France, Japan, Korea, and now in the United States.
Figure 2 is a drawing outlining the basic setup to perform aerosol deposition. Pressure is monitored at the locations marked PAC, PDC, and PH for the aerosol chamber, deposition chamber, and pump head, respectively. The gas flow, controlled by the mass flow controller (MFC), enters the aerosol chamber and aerosolizes the powder. The deposition chamber is pumped to create the pressure difference between the two chambers, causing the flow of particles through the rectangular (0.4 mm x 4.8 mm) nozzle opening.
<img alt="Figure 2" src="/files/ftp_upload/52843/52843fig2.jpg" /> 
Figure 2. Main components in the NRL ADM system. Pressure is monitored at the locations marked PAC, PDC, and PH for the aerosol chamber, deposition chamber, and pump head, respectively. See text for details. (copyright (2014) The Japan Society of Applied Physics, reproduced from Reference 20). <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/52843/52843fig2highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The average size of an individual YIG particle in this work is 0.5 &#181;m. The effect of agglomeration causes these small particles to form much larger agglomerates that range in size from about 10 &#181;m to about 400 &#181;m. Control of the agglomerate size and delivery rate is essential to achieving a dense well-formed film. This necessitates configuration of an aerosol chamber that allows size selection and uniform particle flux into the deposition chamber. The powder is pre-sieved to remove any agglomerates larger than 53 &#181;m prior to being loaded into the aerosol chamber. The aerosol chamber configuration used in this work is illustrated in Figure 3. Nitrogen gas enters through four inlet nozzles (two are shown in Figure 3) located at the bottom sides of the chamber. The gas interacts with the YIG powder (shown in green) to produce an aerosol comprised of a distribution of agglomerated particle sizes less than 53 &#181;m. An agitator at the base of the aerosol chamber made of a stainless steel plate is vibrated continuously to keep the powder moving into the gas flow. The agglomerates impact a 45 &#181;m filter, allowing only agglomerates sized less than 45 &#181;m to enter the nozzle inlet. Upon entering the nozzle inlet the agglomerates are accelerated to a large velocity and ejected into the deposition chamber (not shown) to perform the deposition. A stainless steel rod connects the bottom of the filter to the base of the agitator (not shown) to aid in de-clogging the filter.
<img alt="Figure 3" src="/files/ftp_upload/52843/52843fig3.jpg" /> 
Figure 3. Illustration of the internal aerosol chamber configuration, with filter, inlet nozzles, and YIG powder shown. See text for details.
This report details the experimental procedure to perform AD using the custom-built system described above to produce dense films of YIG. Representative results for an 11 &#181;m thick film produced in this system are presented using scanning electron microscopy (SEM), thickness profiles, and ferromagnetic resonance (FMR). The results presented are not intended to be an in-depth study of the magnetic properties or material structure of the film, but as a demonstration of the films produced by this technique. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/52843/52843fig3highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table><tbody><tr><td>Ferromagnetic Resonance Spectrometer</td><td>www.bruker.com/</td><td>9.5 GHz Spectrometer</td><td></td></tr><tr><td>Scanning Electron Microscope</td><td>www.zeiss.com</td><td>LEO Supra 55</td><td></td></tr><tr><td>Profilometer</td><td>www.kla-tencor.com/</td><td>D-120</td><td></td></tr><tr><td>Stereo Microscope</td><td>www.microscopes.com</td><td>Omano Stereo Microscope</td><td>Used for inspection directly after removal from deposition chamber</td></tr><tr><td>Double-sided Copper Tape</td><td>www.2spi.com</td><td>05085A-AB</td><td>hold-down clips or other adhesives may be used</td></tr><tr><td>Nitrile Exam Gloves</td><td>www.fishersci.com</td><td>19-130-1597D</td><td></td></tr><tr><td>2-propanol</td><td>www.fishersci.com</td><td>A451SK-4</td><td></td></tr><tr><td>Acetone</td><td>www.fishersci.com</td><td>A11-1</td><td></td></tr><tr><td>Yttrium Iron Garnet Powder</td><td>www.trans-techinc.com/</td><td>Call for Product Information</td><td>Powder is custom made to order and ground to specifications</td></tr><tr><td>Stainless Steel Spoon</td><td>www.fishersci.com</td><td>14-429E</td><td>Used for scooping and transferring powder</td></tr><tr><td>Alumina Boats</td><td>www.coorstek.com/</td><td>65580</td><td></td></tr><tr><td>Drying Furnace</td><td>www.paragonweb.com</td><td>KM14 ceramic furnace</td><td>Furnace is connected to air during drying</td></tr><tr><td>Powder Sieves</td><td>www.advantechmfg.com/</td><td>270SS8F</td><td>A selection of mesh openings are needed to sieve from large down to target size</td></tr><tr><td>Ultra High Purity Nitrogen Gas</td><td>www.praxairdirect.com</td><td>NI 5.0UH-3K</td><td>Used as medium for aerosol.</td></tr><tr><td>Air Breathing Quality</td><td>www.praxairdirect.com</td><td>AI BR-4KN</td><td>Used inside furnace during drying</td></tr><tr><td>Lab Balance</td><td>www.balances.com/</td><td>Sartorius ED224S Lab Balance</td><td>Used for weighing powder</td></tr><tr><td>Sapphire Wafers</td><td>www.pmoptics.com/</td><td>PWSP-313211</td><td></td></tr></tbody></table>

formation of thick dense yttrium iron garnet films using aerosol deposition

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk. The primary advantage of AD is that the deposition takes place entirely at ambient temperature; thereby enabling film growth in material systems with disparate melting temperatures. This report describes in detail the processing steps for preparing the powder and for performing AD using the custom-built system. Representative characterization results are presented from scanning electron microscopy, profilometry, and ferromagnetic resonance for films grown in this system. As a representative overview of the capabilities of the system, focus is given to a sample produced following the described protocol and system setup. Results indicate that this system can successfully deposit 11 &#181;m thick yttrium iron garnet films that are &#160;&#62; 90% of the bulk density during a single 5 min deposition run. A discussion of methods to afford better control of the aerosol and particle selection for improved thickness and roughness variations in the film is provided.

After the deposition is complete, the coated substrates are removed from the deposition chamber and inspected using an optical stereo microscope. Samples are typically brushed and washed with isopropanol to remove excess powder that remained during re-pressurization to atmosphere. Film characterization was performed on the representative results presented here using scanning electron microscopy to assess the morphology of the film, profilometry to assess the film thickness, uniformity, and roughness, and ferromagnetic re...

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Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

This report describes the use of a custom-built system to perform aerosol deposition of thick films of yttrium iron garnet onto sapphire substrates at RT. The deposited films are characterized using scanning electron microscopy, profilometry, and ferromagnetic resonance to give a representative overview of the capabilities of the technique.

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% ...

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Engineering

9.2K Views.  Naval Research Laboratory. This report describes the use of a custom-built system to perform aerosol deposition of thick films of yttrium iron garnet onto sapphire substrates at RT. The deposited films are characterized using scanning electron microscopy, profilometry, and ferromagnetic resonance to give a representative overview of the capabilities of the technique.

Video: Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

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, ...

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.

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 ...

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

Chemically ordered alloys are useful in a variety of magnetic nanotechnologies. They are most conveniently prepared at an industrial scale using sputtering techniques. Here we describe a method for preparing epitaxial thin films of B2-ordered FeRh by sputter deposition onto single crystal MgO substrates. Deposition at a slow rate onto a heated substrate allows time for the adatoms to both settle into a lattice with a well-defined epitaxial relationship with the substrate and also to find their proper places in the Fe and Rh sublattices of the B2 structure. The structure is conveniently characterized with X-ray reflectometry and diffraction and can be visualised directly using transmission electron micrograph cross-sections. B2-ordered FeRh exhibits an unusual metamagnetic phase transition: the ground state is antiferromagnetic but the alloy transforms into a ferromagnet on heating with a typical transition temperature of about 380 K. This is accompanied by a 1% volume expansion of the unit cell: isotropic in bulk, but laterally clamped in an epilayer. The presence of the antiferromagnetic ground state and the associated first order phase transition is very sensitive to the correct equiatomic stoichiometry and proper B2 ordering, and so is a convenient means to demonstrate the quality of the layers that can be deposited with this approach. We also give some examples of the various techniques by which the change in phase can be detected.

A method to prepare epitaxial layers of ordered alloys by sputtering is described. The B2-ordered FeRh compound is used as an example, as it displays a metamagnetic transition that depends sensitively on the degree of chemical order and the exact composition of the alloy.

Chemically ordered alloys are useful in a variety of magnetic nanotechnologies. They are most conveniently prepared at an industrial scale using ...

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

Chemistry

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 ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Fabrication of Ultra-thin Color Films with Highly Absorbing Media Using Oblique Angle Deposition

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present an advanced method for fabricating ultra-thin color films with improved characteristics. The proposed process addresses several fabrication issues, including large area processing. Specifically, the protocol describes a process for fabricating ultra-thin color films using an electron beam evaporator for oblique angle deposition of germanium (Ge) and gold (Au) on silicon (Si) substrates.&#160; Film porosity produced by the oblique angle deposition induces color changes in the ultra-thin film. The degree of color change depends on factors such as deposition angle and film thickness. Fabricated samples of the ultra-thin color films showed improved color tunability and color purity. In addition, the measured reflectance of the fabricated samples was converted into chromatic values and analyzed in terms of color. Our ultra-thin film fabricating method is expected to be used for various ultra-thin film applications such as flexible color electrodes, thin film solar cells, and optical filters. Also, the process developed here for analyzing the color of the fabricated samples is broadly useful for studying various color structures.

We present a detailed method for fabricating ultra-thin color films with improved characteristics for optical coatings. The oblique angle deposition technique using an electron beam evaporator allows improved color tunability and purity. Fabricated films of Ge and Au on Si substrates were analyzed by reflectance measurements and color information conversion.

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present ...

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 ...