Name: Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides (Video) | JoVE Journal
Uploaded: 2018-05-29T15:00:00.000+00:00
Duration: 9 min 41 s
Description: Learn to synthesize bulk and thin film entropy-stabilized oxides using grinding, pellet pressing, and pulsed-laser deposition. This method enables tunable material chemistry for studying disorder effects on magnetism.

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5 minutes

This work was funded in part by National Science Foundation grant No. DMR-0420785 (XPS). We thank the University of Michigan&#39;s Michigan Center for Materials Characterization, (MC)2, for its assistance with XPS, and the University of Michigan Van Vlack laboratory for XRD. We would also like to thank Thomas Kratofil for his assistance with bulk materials preparation.

Caution: Wear necessary personal protective equipment (PPE) including close-toed shoes, full length pants, safety glasses, particulate filtration mask, lab coat, and gloves as oxide powders pose a risk for skin contact irritation and eye contact irritation. Consult all relevant material safety data sheets before beginning for additional PPE requirements. Synthesis should be done with the use of engineering controls such as a fume hood.
1. Bulk Synthesis of Entropy-stabilized Oxides
<ol>
	<li>Mass Calculation of Constituent Oxide Powders
	<ol>
		<li>Estimate the total desired mass of the target by multiplying the desired volume by the average density of the constituent binary oxides. 
		<img alt="Mass calculation equation: m_tar = V_tar * ρ_avg; mathematical formula." src="/files/ftp_upload/57746/57746eq3v2.jpg" data-altupdatedat="1788250015000" data-alt="Equation 3"> 
		<img alt="Density calculation formula, ρ_avg=Σ(X_i*ρ_i), equation for average density determination." src="/files/ftp_upload/57746/57746eq4.jpg" data-altupdatedat="1788250015000" data-alt="Equation 4"> 
		where <img alt="Static equilibrium, ΣFx=0 equation, formula diagram for physics education." src="/files/ftp_upload/57746/57746eq5.jpg" data-altupdatedat="1788250015000" data-alt="Equation 5"> and <img alt="Static equilibrium; ΣFx=0; diagram; free-body forces; educational physics; vector sum balance." src="/files/ftp_upload/57746/57746eq6.jpg" data-altupdatedat="1788250015000" data-alt="Equation 6"> are the mole fraction and the density of the <img alt='Optical interference, symbol "i," depicting light wave interaction, diagram for physics study.' src="/files/ftp_upload/57746/57746eq7.jpg" data-altupdatedat="1788250015000" data-alt="Equation 7">th component. For a 1" (2.54 cm) diameter, ⅛" (0.3175 cm) thick sample, the target volume is <img alt="Static equilibrium ΣFx=0; vector diagram; forces analysis; physics study; equilibrium condition." src="/files/ftp_upload/57746/57746eq8.jpg" data-altupdatedat="1788250015000" data-alt="Equation 8">1.7 cm3.</li>
		<li>Determine the required moles of each component by dividing this target mass by the average molar mass of the constituent binary oxides. 
		<img alt="Stoichiometry equation, \( n_i = \frac{m_{tar}}{M_{avg}} \times X_i \), chemical calculations." src="/files/ftp_upload/57746/57746eq9v2.jpg" data-altupdatedat="1788250015000" data-alt="Equation 9"> 
		<img alt="Average mass calculation formula, ΣX_i * M_i, equation for chemical or physical analysis." src="/files/ftp_upload/57746/57746eq10.jpg" data-altupdatedat="1788250015000" data-alt="Equation 10"> 
		where <img alt="Static equilibrium equations diagram; ΣFx=0, MA=0; mechanical system analysis." src="/files/ftp_upload/57746/57746eq11.jpg" data-altupdatedat="1788250015000" data-alt="Equation 11"> is the molar mass of the <img alt='Optical interference, symbol "i," depicting light wave interaction, diagram for physics study.' src="/files/ftp_upload/57746/57746eq7.jpg" data-altupdatedat="1788250015000" data-alt="Equation 7">th component. Convert the number of moles, <img alt="Chromatography diagram: protein purification method, separation process, analytical technique." src="/files/ftp_upload/57746/57746eq12.jpg" data-altupdatedat="1788250015000" data-alt="Equation 12">, back to grams by 
		<img alt="Stoichiometry equation \( m_i = n_i \times M_i \), chemical calculation concept." src="/files/ftp_upload/57746/57746eq13.jpg" data-altupdatedat="1788250015000" data-alt="Equation 13"> 
		NOTE: The masses of constituents and targeted compositions of the materials synthesized here are given in Tables 1 and 2.</li>
	</ol>
	</li>
	<li>Preprocessing of Oxide Powders
	<ol>
		<li>Clean an agate pestle and mortar by etching with 20 mL of aqua regia (HNO3 + 3 HCl). Pour the acid into the mortar and grind with the pestle until the bottom is clear. Dispose of the acid properly and rinse with water.</li>
		<li>Combine 0.559 g of MgO, 1.103 g of CoO, 1.035 g of NiO, 1.103 g of CuO, and 1.129 g of ZnO (for equimolar composition) powders in the clean mortar.</li>
		<li>Using the clean pestle, grind the powder using clockwise motions for 20 turns, then 20 counterclockwise turns. Repeat this process for at least 45 min. Use a clean metal spatula to remove powder from the sides of the mortar and brush the powder down to the center of the mortar. 
		NOTE: Powder mixing and grinding are complete when the powder is homogenous and grey-black in color, appears finely ground, and feels smooth.</li>
		<li>Transfer the powder into a clean, sealable container for transport.</li>
	</ol>
	</li>
	<li>Ceramic Pellet Pressing 
	CAUTION: Wear gloves and safety glasses when assembling the die and while the press is in use. Perform entire die cleaning and assembly steps on a clean paper surface. The components used are shown in Figure 2.
	<ol>
		<li>Lubricate the sides and interior face of the small bottom plunger (labelled C in Figure 2a and 2b) of the die with mineral oil and insert into the die cylinder until it is flush with the bottom.</li>
		<li>Roll a weigh paper into the cavity of the die so that the sides of the die are covered. Pour the powder into the bottom of the die. Without allowing the small plunger to fall out of the die, gently tap the part on the counter to remove any air pockets and level the powder. Carefully remove the weigh paper.</li>
		<li>Add a small amount of acetone to the powder in the cavity of the die to form a slurry. This enables grain flow while the target is under pressure and inhibits the formation of voids.</li>
		<li>Lubricate the sides and interior face of the plunger (part B in Figure 2a and 2b) with paraffin oil, being careful to not disturb the powder. Insert this part into the die. Place the assembled die into the pressing machine as pictured in Figure 2c, including the top and bottom plates (parts D in Figure 2a and 2b) to provide an even surface.</li>
		<li>Place die in the cold uniaxial press. Pump the press arm until 200 MPa is reached. Allow the press to sit in the compressed state for 20 min. The pressure will relax with time as the powder densifies. Add pressure as needed to maintain 200 MPa for the duration of pressing. Wipe away any excess solvent that leaks out of the die.</li>
		<li>Release the press pressure. Carefully remove the top and bottom plates. Position the removal sheath and removal piston as shown in Figure 2c. Press slowly, removing the small die piece from the assembly before exposing the pressed target. Press the assembly carefully until the target is exposed from the die. Carefully remove the green body and transfer to a crucible for sintering.</li>
	</ol>
	</li>
	<li>Ceramic sintering 
	CAUTION: Target materials will be quenched from high temperatures. Wear heat resistant gloves and a face shield when removing the crucible from the hot furnace.
	<ol>
		<li>Obtain an alumina crucible that will fit the pressed powder and a 2 mm layer of Yttria-Stabilized Zirconia (YSZ) 0.1–0.2 mm beads. Coat the bottom of the crucible with YSZ beads. 
		NOTE: The coating should be approximately 2 mm in thickness to ensure that the target does not contact the bottom of the crucible.</li>
		<li>Slowly and carefully transfer the pressed target to the center of the crucible.</li>
		<li>Using metal tongs, carefully transport the crucible to the sintering furnace. Increase the temperature to 1100 °C at 50 °C min-1. Sinter the target for 24 h at 1,100 °C in an air atmosphere.</li>
		<li>While at 1100 °C, remove the crucible from the furnace. Using tongs, quickly quench the target in room temperature water. The target will sputter for ~30 s, then remove it from the water and set to dry.</li>
		<li>Once target is cool and dry, measure the target density and compare to the theoretical value, <img alt="ρ_avg symbol for average density calculation." src="/files/ftp_upload/57746/57746eq14v2.jpg" data-altupdatedat="1788250015000" data-alt="Equation 14">, calculated in Part 1. Measure the mass of the target on the balance used previously, and measure the dimensions using calipers. The ratio of the measured density to the estimated value, <img alt="Formula for density calculation: (m_measured/V_measured)/ρ_avg, equation representation." src="/files/ftp_upload/57746/57746eq15.jpg" data-altupdatedat="1788250015000" data-alt="Equation 15">, gives the percent theoretical density. 
		NOTE: After the synthesis, the density is usually ~80% of the theoretical density.</li>
		<li>For higher density, regrind the sintered target using the pestle and mortar and repeat the Bulk Synthesis procedure from step 1.2.3. After the second sintering, determine the density of the target. 
		NOTE: Usually the measured density is <img alt='Mathematical symbol "greater than or equal to" 90% shown in an equation format for calculations.' src="/files/ftp_upload/57746/57746eq16.jpg" data-altupdatedat="1788250015000" data-alt="Equation 16"> theoretical density, which is suitable for pulsed laser deposition (PLD).</li>
	</ol>
	</li>
</ol>
2. PLD of ESO Single Crystal Films
<ol>
	<li>Target preparation
	<ol>
		<li>The bulk ceramic pellets synthesized in step 1 will now serve as deposition sources (targets). Polish the target(s) in a circular motion using progressive (320/600/800/1,200) grits of SiC paper until the surface is reflective and uniform.</li>
		<li>Place the targets on the rotating carousel inside the chamber and place a ~2 cm x 2 cm piece of burn paper on the final target in the beam path.</li>
		<li>Measure the laser spot size by firing a single shot at the target and measuring the resulting burn mark across both axes. If the spot size is not correct, adjust the focusing lens (Figure 3a). Adjust the measured spot size until an ellipse, 0.27 cm x 0.24 cm across both axes is achieved.</li>
		<li>Remove the burn paper and close the door for evacuation. Evacuate the chamber using a dry scroll roughing pump to a pressure of 6.7 Pa, at which point the turbo pump can be spun up to a rate of 1,000 Hz.</li>
		<li>Pump out the chamber to a base pressure of at least 1.3 x 10-5 Pa as measured by an ion gauge. Once reached, reduce the turbo to a speed of 200 Hz to allow the use of process gas during the growth.</li>
	</ol>
	</li>
	<li>Substrate Preparation
	<ol>
		<li>Clean a single crystalline, one side polished, 0.5 mm thick MgO substrate by sonication for 2 min each in semiconductor grade trichloroethylene (TCE), semiconductor grade acetone, and high purity isopropanol (IPA).</li>
		<li>Blow the substrate off with ultra-dry, compressed N2 gas, and attach the substrate to the substrate platen (Figure 3b) with a small amount of thermally conductive silver paint. Heat the substrate and platen to °C for 10 min on a hot plate to cure the silver paint.</li>
		<li>Using the external transfer tool, place the substrate holder on the transfer arm in the chamber load lock, then seal and pump out the chamber to a pressure of at least 1.3 x 10-4 Pa.</li>
		<li>Transfer the substrate into the growth chamber by opening the gate valve between the two and using the transfer arm to place the substrate platen on the heater assembly.</li>
		<li>Retract the transfer arm back into the load lock and seal the gate. Lower the heater using the screw assembly on top of the chamber.</li>
	</ol>
	</li>
	<li>Laser Energy and Fluence 
	NOTE: Deposition is enabled by the irradiation from a 248 nm KrF pulsed excimer laser. The laser pulse width is ~20 ns.
	<ol>
		<li>Measure the laser energy using an energy meter placed in the beam path, just before entering the chamber (Figure 3a). Determine the mean energy after irradiating the photodiode with 50 pulses at a rate of 2 Hz.</li>
		<li>Vary the excitation voltage of the laser until an average pulse energy of 310 mJ is reached with ± 10 mJ stability. Remove the energy meter from the beam path to allow the laser to pass into the chamber. 
		NOTE: Using a laser attenuation of the chamber window of 10%, the configuration above gives a fluence of 2.55 J cm-2. The substrate-target distance in this work is 7 cm. A different substrate-target difference may change ideal deposition conditions and growth rate.</li>
	</ol>
	</li>
	<li>Deposition
	<ol>
		<li>Before growth, heat the substrate to 1,000 °C for 30 min at a rate 30 °C min-1 in vacuum to dehydroxylize the surface of MgO crystal. Reduce the temperature to 300 °C at 30° min-1 and allow to equilibrate for 10 min. 
		NOTE: Our reported temperatures are determined by a thermocouple within the heater block.</li>
		<li>Flow ultra-high purity (99.999%) O2 gas into the chamber to reach a pressure of 6.7 Pa. 
		NOTE: When oxygen flown into the chamber, the pressure is measured using a barotron gauge. The gas is introduced using a mass flow controller, as part of a closed loop system which stabilizes chamber pressure during growth.</li>
		<li>Clean the targets of any remaining contaminants and prepare them for growth by pre-ablation. Set the selected target to raster and rotate, so that the laser is not hitting the same spot each time, ensure that the substrate shutter is closed, and ablate the target for 2,000 pulses at a rate of 5 Hz. 
		NOTE: The target is now prepared, and the system is at the correct conditions (temperature, pressure, fluence) for deposition.</li>
		<li>Open the shutter before deposition. At these conditions, 10,000 pulses at 6 Hz produces an ~80 nm thick film. 
		NOTE: This growth rate was determined by X-ray reflectivity in previous work16.</li>
		<li>After deposition, increase the oxygen partial pressure to 133 Pa (1.0 torr) to inhibit the formation of oxygen vacancies. Reduce the sample temperature to 40 °C at 10 °min-1. Once 40 °C is reached, close the flow of oxygen and, after the stabilization of pressure, open the gate valve between the growth chamber and the load lock. Raise the heater and use the transfer arm to remove the substrate platen from the assembly back into the load lock.</li>
		<li>Vent the load lock to atmosphere and remove the sample using the external transfer tool. Remove the sample from the platen using a razor blade and polish the platen to take off the remaining silver paint and deposited material. Repeat the procedure starting from step 2.2 for additional film growth.</li>
	</ol>
	</li>
</ol>

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<li>Damodaran, A. R., Breckenfeld, E., Chen, Z., Lee, S., Martin, L. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Enhancement+of+Ferroelectric+Curie+Temperature+in+BaTiO3+Films+via+Strain-Induced+Defect+Dipole+Alignment%5BTitle%5D)+AND+%22Adv+Mater%22%5BJournal%5D)">Enhancement of Ferroelectric Curie Temperature in BaTiO3 Films via Strain-Induced Defect Dipole Alignment.</a> Adv Mater. 26 (36), 6341-6347 (2014).</li>
</ol>

We have nothing to disclose.

We have described and shown a protocol for the synthesis of bulk and high-quality, single crystalline films of (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) entropy-stabilized oxides. We expect these synthesis techniques to be applicable to a wide range of entropy-stabilized oxide compositions as more are discovere...

Since the discovery of high-entropy metal alloys in 2004, high-entropy materials have attracted significant interest due to the properties such as increased hardness1,2,3, toughness4,5, and corrosion resistance3,6. Recently, high-entropy oxides7,8 and borides9 have been discovered, opening up a large playground for material enthusiasts. Oxides, in particular, can demonstrate useful and dynamic functional properties such as ferroelectricity10, magnetoelectricity11,12, thermoelectricity13, and superconductivity14. Entropy-stabilized oxides (ESOs) have recently been shown to possess interesting, compositionally-dependent functional properties15,16, despite the significant disorder, making this new class of materials particularly exciting.
Entropy-stabilized materials are chemically homogeneous, multicomponent (typically having five or more constituents), single-phase materials where the configurational entropic contribution (<img alt="Static equilibrium, ΔS_conf, equation, thermodynamic entropy change, molecular configuration." src="/files/ftp_upload/57746/57746eq1.jpg" data-altupdatedat="1788250015000" data-alt="Equation 1">) to the Gibbs free energy (<img alt="Thermodynamics equation ΔGf = ΔH - TΔSconf, symbol formula in biochemical process analysis." src="/files/ftp_upload/57746/57746eq2.jpg" data-altupdatedat="1788250015000" data-alt="Equation 2">) is significant enough to drive the formation of a single phase solid solution17. The synthesis of multicomponent ESOs, where cationic configurational disorder is observed across the cation sites, requires precise control over the composition, temperature, deposition rate, quench rate, and quench temperature7,16. This method seeks to enable the practitioner the ability to synthesize phase pure and chemically homogeneous entropy-stabilized oxide ceramic pellets and phase pure, single crystalline, flat thin films of the desired stoichiometry. Bulk materials can be synthesized with greater than 90% theoretical density enabling the study of the electronic, magnetic, and structural properties or use as sources for thin film physical vapor deposition (PVD) techniques. As the entropy-stabilized oxides considered here have five cations, thin film PVD techniques that employ five sources, such as molecular beam epitaxy (MBE) or co-sputtering, will be presented with the challenge of depositing chemically homogenous thin films due to flux drift. This protocol results in chemically homogenous, single crystalline, flat (root-mean-square (RMS) roughness of ~0.15 nm) entropy-stabilized oxide thin films from a single material source, which are shown to possess the nominal chemical composition. This thin film synthesis protocol may be enhanced by the inclusion of in situ electron or optical characterization techniques for real-time monitoring of the synthesis and refined quality control. Expected limitations of this method stem from laser energy drift which may limit the thickness of high quality films to be below 1 μm.
Despite the significant advances in the growth and characterization of thin film oxide materials10,18,19,20,21, the correlation between stereochemistry and electronic structure in oxides can lead to significant differences in the final material stemming from seemingly insignificant methodological differences. Furthermore, the field of multicomponent entropy-stabilized oxides is rather nascent, with only two current reports of thin film synthesis in the literature7,16. ESOs lend themselves particularly well to this process, circumventing challenges that would be presented by chemical vapor deposition and molecular beam epitaxy. Here, we provide a detailed synthesis protocol of bulk and thin films ESOs (Figure 1), in order to minimize materials processing difficulties, unintended property variations, and improve the acceleration of discovery in the field.

<table><tbody><tr><td>MAGNESIUM OXIDE 99.95%</td><td>Fisher</td><td>AA1468422</td><td></td></tr><tr><td>COBALT(II) OXIDE, 99.995%</td><td>Fisher</td><td>AA4435414</td><td></td></tr><tr><td>NICKEL(II) OXIDE 99.998%</td><td>Fisher</td><td>AA1081914</td><td></td></tr><tr><td>COPPER(II) OXIDE 99.995%</td><td>Fisher</td><td>AA1070014</td><td></td></tr><tr><td>ZINC OXIDE 99.99%</td><td>Fisher</td><td>AA8781230</td><td></td></tr><tr><td>TRICHLROETHLENE SEMICNDTR 9</td><td>Fisher</td><td>AA39744K7</td><td></td></tr><tr><td>ACETONE SEMICNDTR GRD 99.5%</td><td>Fisher</td><td>AA19392K7</td><td></td></tr><tr><td>2-PROPANOL ACS 99.5%</td><td>Fisher</td><td>A416S4</td><td></td></tr><tr><td>Mineral oil, pure</td><td>Acros Organics</td><td>AC415080010</td><td></td></tr><tr><td>alumina crucible</td><td>MTI Corporation</td><td>eq-ca-l50w40h20</td><td></td></tr><tr><td>ZIRCONIA (YSZ) GRINDING MEDIA</td><td>Inframat Advanced Materials</td><td>4039GM-S010</td><td></td></tr><tr><td>SiC paper 320/600/800/1200</td><td>South Bay Technology</td><td>SDA08032-25</td><td></td></tr><tr><td>MgO (100) substrate, 5x5x0.5 mm, 1SP</td><td>MTI Corporation</td><td>MGa050505S1</td><td></td></tr><tr><td>OXYGEN COMPRESSED ULTRA HIGH PURITY GRADE, 99.999%</td><td>Cryogenic Gases</td><td>OXYUHP</td><td></td></tr><tr><td>NITROGEN COMPRESSED EXTRA DRY GRADE</td><td>Cryogenic Gases</td><td>NITEX</td><td></td></tr></tbody></table>

bulk and thin film synthesis of compositionally variant entropy-stabilized oxides

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.

X-ray diffraction (XRD) spectra were taken of both the prepared (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) bulk ceramics (Figure 4a) and deposited thin films (Figure 4b). These data show that the samples are single phase...

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 ...

bulk-thin-film-synthesis-compositionally-variant-entropy-stabilized

Research

JoVE Journal

Engineering

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.

Fabrication of Spatially Confined Complex Oxides

Oxide nanostructures provide new opportunities for science and technology.  The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique.  The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

Writing and Low-Temperature Characterization of Oxide Nanostructures

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 Templates for Epitaxial Growth of Complex Oxide Thin Films

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.

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

We fabricate metal/LaAlO3/SrTiO3 heterostructures using a combination of pulsed laser deposition and in situ magnetron sputtering. Through magnetotransport and in situ X-ray photoelectron spectroscopy experiments, we investigate the interplay between electrostatic and chemical phenomena of the quasi two-dimensional electron gas formed in this system.

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

Here, we present a protocol for the synthesis of porous barium titanate (BaTiO3) thin film by a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles are used as an organic template.

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Metal-organic frameworks are effective in gas storage and heterogeneous catalysis, but typical synthesis methods result in loose powders that are difficult to incorporate into smart materials. We demonstrate a method of first coating fabrics with ALD metal oxides, resulting in conformal films of MOF on the fabrics during solvothermal synthesis.

Solvothermal Synthesis of MIL-96 and UiO-66-NH2 on Atomic Layer Deposited Metal Oxide Coatings on Fiber Mats

Here, we demonstrate a unique, relatively low-temperature, molten-salt synthesis method for preparing uniform complex metal oxide lanthanum hafnate nanoparticles.

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

Oxide materials show many exotic properties that can be controlled by tuning the oxygen content. Here, we demonstrate the tuning of oxygen content in oxides by varying the pulsed laser deposition parameters and by performing postannealing. As an example, electronic properties of SrTiO3-based heterostructures are tuned by growth modifications and annealing.

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

We report a one-pot hydrothermal synthesis of manganese ferrite clusters (MFCs) that offers independent control over material dimension and composition. Magnetic separation allows rapid purification while surface functionalization using sulfonated polymers ensures the materials are non-aggregating in biologically relevant medium. The resulting products are well positioned for biomedical applications.

Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

Learn to synthesize bulk and thin film entropy-stabilized oxides using grinding, pellet pressing, and pulsed-laser deposition. This method enables tunable material chemistry for studying disorder effects on magnetism.

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

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