Name: formation of thick dense yttrium iron garnet films using aerosol deposition
Uploaded: 2015-05-15T15:00:00
Description: Watch this Scientific Journal Video about Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition at JoVE.com

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 Depositi...

<ol>
	<li>Akedo, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room+Temperature+Impact+Consolidation+(RTIC)+of+Fine+Ceramic+Powder+by+Aerosol+Deposition+Method+and+Applications+to+Microdevices.">Room Temperature Impact Consolidation (RTIC) of Fine Ceramic Powder by Aerosol Deposition Method and Applications to Microdevices.</a> J. of Therm. Spray tech. 17, 181 (2008).</li><li>Hahn, B. D., Park, D. -. S., Choi, J. -. J., Ryu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoconductive+hydroxyapatite+coated+PEEK+for+spinal+fusion+surgery.">Osteoconductive hydroxyapatite coated PEEK for spinal fusion surgery.</a> Appl. Surf. Sci. 283, 6-11 (2013).</li><li>Johnson, S. 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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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porous+Photocatalytic+TiO2+Thin+Films+by+Aerosol+Deposition.">Porous Photocatalytic TiO2 Thin Films by Aerosol Deposition.</a> J. Am. Ceram. Soc. 93 (1), 55-58 (2010).</li><li>Harris, V. 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=Recent+advances+in+processing+and+applications+of+microwave+ferrites.">Recent advances in processing and applications of microwave ferrites.</a> J. of Magn. and Magn. Mat. 321, 2035 (2009).</li><li>Kang, Y. -. M., Ulyanov, A. N., Yoo, S. -. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FMR+linewidths+of+YIG+films+fabricated+by+ex+situ+post-annealing+of+amorphous+films+deposited+by+rf+magnetron+sputtering.">FMR linewidths of YIG films fabricated by ex situ post-annealing of amorphous films deposited by rf magnetron sputtering.</a> Phys. Stat. Sol. (a). 204 (3), 763-767 (2007).</li><li>Popova, E., 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=Perpendicular+magnetic+anisotropy+in+ultrathin+yttrium+iron+garnet+films+prepared+by+pulsed+laser+deposition+technique).">Perpendicular magnetic anisotropy in ultrathin yttrium iron garnet films prepared by pulsed laser deposition technique).</a> J. of Vac. Sci. Techn. 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. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+Ferrite-Integrated+On-Chip+Inductors+Using+Aerosol+Deposition.">Advances in Ferrite-Integrated On-Chip Inductors Using Aerosol Deposition.</a> Magnetics Business &amp; Technology Magazine. 10, (2014).</li><li>Johnson, S. D., Glaser, E. R., Cheng, S. -. F., Kub, F., Eddy Jr, ., R, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+As-Deposited+and+Sintered+Yttrium+Iron+Garnet+Thick+Films+Formed+by+Aerosol.">Characterization of As-Deposited and Sintered Yttrium Iron Garnet Thick Films Formed by Aerosol.</a> Appl. Phys. Express. 7, 035501 (2014).</li><li>Lee, D. -. W., Nam, S. -. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+Affecting+Surface+Roughness+of+Al2O3+Films+Deposited+on+Cu+Substrates+by+an+Aerosol+Deposition+Method.">Factors Affecting Surface Roughness of Al2O3 Films Deposited on Cu Substrates by an Aerosol Deposition Method.</a> J. of Ceramic Proc. Research. 11, 100 (2010).</li><li>Glass, H. L., Elliott, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Attainment+of+the+Intrinsic+FMR+Linewidth+in+Yttrium+Iron+Garnet+Films+Grown+by+Liquid+Phase+Epitaxy.J.">Attainment of the Intrinsic FMR Linewidth in Yttrium Iron Garnet Films Grown by Liquid Phase Epitaxy.J.</a> Cryst. Growth. 34, 285 (1976).</li></ol>

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://www.jove.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://www.jove.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://www.jove.com/files/ftp_upload/52843/52843fig3highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="0" cellpadding="0" cellspacing="0">
	<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...

Watch this Scientific Journal Video about Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition at JoVE.com

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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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, ...

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The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.

The technique of diffusive gradients in thin films (DGT) is proposed for speciation studies of plutonium. This protocol describes diffusion experiments probing the behavior of Pu(IV) and Pu(V) in presence of organic matter. DGTs deployed in a karstic spring allow assessment of the bioavailability of Pu.

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can ...

Electrospray Deposition of Uniform Thickness Ge23Sb7S70 and As40S60 Chalcogenide Glass Films

Solution-based electrospray film deposition, which is compatible with continuous, roll-to-roll processing, is applied to chalcogenide glasses. Two chalcogenide compositions are demonstrated: Ge23Sb7S70 and As40S60, which have both been studied extensively for planar mid-infrared (mid-IR) microphotonic devices. In this approach, uniform thickness films are fabricated through the use of computer numerical controlled (CNC) motion. Chalcogenide glass (ChG) is written over the substrate by a single nozzle along a serpentine path. Films were subjected to a series of heat treatments between 100 &#176;C and 200 &#176;C under vacuum to drive off residual solvent and densify the films. Based on transmission Fourier transform infrared (FTIR) spectroscopy and surface roughness measurements, both compositions were found to be suitable for the fabrication of planar devices operating in the mid-IR region. Residual solvent removal was found to be much quicker for the As40S60 film as compared to Ge23Sb7S70. Based on the advantages of electrospray, direct printing of a gradient refractive index (GRIN) mid-IR transparent coating is envisioned, given the difference in refractive index of the two compositions in this study.

Electrospray Deposition of Uniform Thickness Ge23Sb7S70 and As40S60 Chalcogenide Glass Films

A method of uniform thickness solution-derived chalcogenide glass film deposition is demonstrated using computer numerical controlled motion of a single-nozzle electrospray.

Solution-based electrospray film deposition, which is compatible with continuous, roll-to-roll processing, is applied to chalcogenide glasses. Two ...

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 ...

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a standard fluid dynamic diagnostic, particle image velocimetry (PIV), to measure: i) velocities of individual particles (grains), extant on short, grain-collision time-scales, ii) velocities of systems of particles, on both short collision-time- and long, continuum-flow-time-scales, iii) collective hydrodynamic modes known to exist in dense molecular fluids, and iv) short- and long-time-scale velocity autocorrelation functions, central to understanding particle-scale dynamics in strongly interacting, dense fluid systems. The basic system is composed of an imaging system, light source, vibrational sensors, vibrational system with a known media, and PIV and analysis software. Required experimental measurements and an outline of the theoretical tools needed when using the analog technique to study molecular-scale hydrodynamic processes are highlighted. The proposed technique provides a relatively straightforward alternative to photonic and neutron beam scattering methods traditionally used in molecular hydrodynamic studies.

An experimentally accessible analog method for studying molecular hydrodynamic processes in dense fluids is presented. The technique uses particle image velocimetry of vibrated, high-restitution grain piles and allows direct, macroscopic observation of dynamical processes known and predicted to exist in strongly interacting, high density gases and liquids.

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a ...

Production of Single Tracks of Ti-6Al-4V by Directed Energy Deposition to Determine the Layer Thickness for Multilayer Deposition

Directed Energy Deposition (DED), which is an additive manufacturing technique, involves the creation of a molten pool with a laser beam where metal powder is injected as particles. In general, this technique is employed to either fabricate or repair different components. In this technique, the final characteristics are affected by many factors. Indeed, one of the main tasks in building components by DED is the optimization of process parameters (such as laser power, laser speed, focus, etc.) which is usually carried out through an extensive experimental investigation. However, this sort of experiment is extremely lengthy and costly. Thus, in order to accelerate the optimization process, an investigation was conducted to develop a method based on the melt pool characterizations. In fact, in these experiments, single tracks of Ti-6Al-4V were deposited by a DED process with multiple combinations of laser power and laser speed. Surface morphology and dimensions of single tracks were analyzed, and geometrical characteristics of melt pools were evaluated after polishing and etching the cross-sections. Helpful information regarding the selection of optimal process parameters can be achieved by examining the melt pool features. These experiments are being extended to characterize the larger blocks with multiple layers. Indeed, this manuscript describes how it would be possible to quickly determine the layer thickness for the massive deposition, and avoid over or under-deposition according to the calculated energy density of the optimum parameters. Apart from the over or under-deposition, time and materials saving are the other great advantages of this approach in which the deposition of multilayer components can be started without any parameter optimization in terms of layer thickness.

In this research, a rapid method based on melt pool characterization is developed to estimate the layer thickness of Ti-6Al-4V components produced by directed energy deposition.

Directed Energy Deposition (DED), which is an additive manufacturing technique, involves the creation of a molten pool with a laser beam where metal ...

Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with wafer-scale uniformity and angstrom level control of thickness, the method of atomic-layer deposition was chosen. This ALD process enables high-quality, low-temperature (&#8804;150 &#176;C) growth of ultrathin films (100-1000 &#197;) of VO2. For this demonstration, the VO2 films were grown on sapphire substrates. This low temperature growth technique produces mostly amorphous VO2 films. A subsequent anneal in an ultra-high vacuum chamber with a pressure of 7x10-4 Pa of ultra-high purity (99.999%) oxygen produced oriented, polycrystalline VO2 films. The crystallinity, phase, and strain of the VO2 were determined by Raman spectroscopy and X-ray diffraction, while the stoichiometry and impurity levels were determined by X-ray photoelectron spectroscopy, and finally the morphology was determined by atomic force microscopy. These data demonstrate the high-quality of the films grown by this technique. A model was created to fit to the data for VO2 in its metallic and insulating phases in the near infrared spectral region. The permittivity and refractive index of the ALD VO2 agreed well with the other fabrication methods in its insulating phase, but showed a difference in its metallic state. Finally, the analysis of the films&#39; optical properties enabled the creation of a wavelength- and temperature-dependent model of the complex optical refractive index for developing VO2 as a tunable refractive index material.

Thin films (100-1000 &#197;) of vanadium dioxide (VO2) were created by atomic-layer deposition (ALD) on sapphire substrates. Following this, the optical properties were characterized through the metal-insulator transition of VO2. From the measured optical properties, a model was created to describe the tunable refractive index of VO2.

Vanadium dioxide is a material that has a reversible metal-insulator phase change near 68 &#176;C. To grow VO2 on a wide variety of substrates, with ...

Film Control to Study Contributions of Waves to Droplet Impact Dynamics on Thin Flowing Liquid Films

Droplet impact is a very common phenomenon in nature and attracts attention due to its aesthetic fascination and wide-ranging applications. Previous studies on flowing liquid films have neglected the contributions of spatial structures of waves to the impact outcome, while this has recently been shown to have a significant influence on the drop impact dynamics. In this report, we outline a step-by-step procedure to investigate the effect of periodic inlet forcing of a flowing liquid film leading to the production of spatiotemporally regular wave structures on drop impact dynamics. A function generator in connection with a solenoid valve is used to excite these spatiotemporally regular wave structures on the film surface while the impact dynamics of uniform-sized droplets are captured using a high-speed camera. Three distinct regions are then studied; viz. the capillary wave region preceding the large wave peak, the flat film region, and the wave hump region. The effects of important dimensionless quantities such as film Reynolds, drop Weber and Ohnesorge numbers parameterized by the film flow rate, drop speed, and drop size are also examined. Our results show interesting, hitherto undiscovered dynamics brought about by this application of film inlet forcing of the flowing film for both low and high inertia drops.

A protocol to study the contributions of waves to droplet impact dynamics on flowing liquid films is presented.

Droplet impact is a very common phenomenon in nature and attracts attention due to its aesthetic fascination and wide-ranging applications. Previous ...

Plasma-Assisted Molecular Beam Epitaxy Growth of Mg3N2 and Zn3N2 Thin Films

This article describes a procedure for growing Mg3N2 and Zn3N2 films by plasma-assisted molecular beam epitaxy (MBE). The films are grown on 100 oriented MgO substrates with N2 gas as the nitrogen source. The method for preparing the substrates and the MBE growth process are described. The orientation and crystalline order of the substrate and film surface are monitored by the reflection high energy electron diffraction (RHEED) before and during growth. The specular reflectivity of the sample surface is measured during growth with an Ar-ion laser with a wavelength of 488 nm. By fitting the time dependence of the reflectivity to a mathematical model, the refractive index, optical extinction coefficient, and growth rate of the film are determined. The metal fluxes are measured independently as a function of the effusion cell temperatures using a quartz crystal monitor. Typical growth rates are 0.028 nm/s at growth temperatures of 150 &#176;C and 330 &#176;C for Mg3N2 and Zn3N2 films, respectively.

Plasma-Assisted Molecular Beam Epitaxy Growth of Mg3N2 and Zn3N2 Thin Films

This article describes the growth of epitaxial films of Mg3N2 and Zn3N2 on MgO substrates by plasma-assisted molecular beam epitaxy with N2 gas as the nitrogen source and optical growth monitoring.

This article describes a procedure for growing Mg3N2 and Zn3N2 films by plasma-assisted molecular beam epitaxy (MBE). The films are grown on 100 oriented ...

Procedure for the Transfer of Polymer Films Onto Porous Substrates with Minimized Defects

The fabrication of devices containing thin film composite membranes necessitates the transfer of these films onto the surfaces of arbitrary support substrates. Accomplishing this transfer in a highly controlled, mechanized, and reproducible manner can eliminate the creation of macroscale defect structures (e.g., tears, cracks, and wrinkles) within the thin film that compromise device performance and the usable area per sample. Here, we describe a general protocol for the highly controlled and mechanized transfer of a polymeric thin film onto an arbitrary porous support substrate for eventual use as a water filtration membrane device. Specifically, we fabricate a block copolymer (BCP) thin film on top of a sacrificial, water-soluble poly(acrylic acid) (PAA) layer and silicon wafer substrate. We then utilize a custom-designed, 3D-printed transfer tool and drain chamber system to deposit, lift-off, and transfer the BCP thin film onto the center of a porous anodized aluminum oxide (AAO) support disc. The transferred BCP thin film is shown to be consistently placed onto the center of the support surface due to the guidance of the meniscus formed between the water and the 3D-printed plastic drain chamber. We also compare our mechanized transfer-processed thin films to those that have been transferred by hand with the use of tweezers. Optical inspection and image analysis of the transferred thin films from the mechanized process confirm that little-to-no macroscale inhomogeneities or plastic deformations are produced, as compared to the multitude of tears and wrinkles produced from manual transfer by hand. Our results suggest that the proposed strategy for thin film transfer can reduce defects when compared to other methods across many systems and applications.

We present a procedure for highly controlled and wrinkle-free transfer of block copolymer thin films onto porous support substrates using a 3D-printed drain chamber. The drain chamber design is of general relevance to all procedures involving transfer of macromolecular films onto porous substrates, which is normally done by hand in an irreproducible fashion.

The fabrication of devices containing thin film composite membranes necessitates the transfer of these films onto the surfaces of arbitrary support ...