Name: a standard and reliable method to fabricate two-dimensional nanoelectronics
Uploaded: 2018-08-28T13:00:00
Description: Watch this Scientific Journal Video about A Standard and Reliable Method to Fabricate Two-Dimensional Nanoelectronics at JoVE.com

This work was supported by the National Science Council, Taiwan under contract No. MOST 105-2112-M-003-016-MY3. This work was also in part supported by the National Nano Device Laboratories and e-beam laboratory in electrical engineering of National Taiwan University.

1. 2D Quasi-heterojunction Transistors Fabrication Process
<ol>
	<li>Prepare commercial c-plane sapphire.
	<ol>
		<li>Wash the whole single-side polished sapphire (2-inch) with acetone.</li>
		<li>Rinse the sapphire substrate with isopropyl alcohol.</li>
	</ol>
	</li>
	<li>Grow MoS2 on sapphire substrate using CVD in a hot-wall furnace.
	<ol>
		<li>Place 0.6 g of molybdenum trioxide (MoO3) powder in a quartz boat located at the heating zone center of the furnace. Put the sapphire substrate downstr...

<ol>
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H., 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=Polymer-free+patterning+of+graphene+at+sub-10-nm+scale+by+low-energy+repetitive+electron+beam.">Polymer-free patterning of graphene at sub-10-nm scale by low-energy repetitive electron beam.</a> Small. 10 (22), 4778-4784 (2014).</li><li>Romero, M. F., Bosca, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+2D-Graphene+on+SiN+Passivated+AlGaN/GaN+MIS-HEMTs+Under+Mist+Exposure.">Impact of 2D-Graphene on SiN Passivated AlGaN/GaN MIS-HEMTs Under Mist Exposure.</a> IEEE Electron Device Letters. 38 (10), 1441-1444 (2017).</li><li>Blaschke, B. M., Tort-Colet, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+brain+activity+with+flexible+graphene+micro-transistors.">Mapping brain activity with flexible graphene micro-transistors.</a> 2D Materials. 4 (2), 25040 (2017).</li><li>Zhu, Z., Murtaza, I., Meng, H., Huang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thin+film+transistors+based+on+two+dimensional+graphene+and+graphene/semiconductor+heterojunctions.">Thin film transistors based on two dimensional graphene and graphene/semiconductor heterojunctions.</a> RSC Advances. 7 (28), 17387-17397 (2017).</li><li>Kim, S. J., Choi, K., Lee, B., Kim, Y., Hong, B. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Materials+for+Flexible,+Stretchable+Electronics:+Graphene+and+2D+Materials.">Materials for Flexible, Stretchable Electronics: Graphene and 2D Materials.</a> Annual Review of Materials Research. 45 (1), 63-84 (2015).</li><li>Manzeli, S., Ovchinnikov, D., Pasquier, D., Yazyev, O. V., Kis, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=2D+transition+metal+dichalcogenides.">2D transition metal dichalcogenides.</a> Nature Reviews Materials. 2, (2017).</li><li>Kolobov, A. V., Tominaga, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Emerging Applications of 2D TMDCs. 239, 473-512 (2016).</li><li>Nguyen, L. N., Lan, Y. 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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+development+of+two-dimensional+transition+metal+dichalcogenides+and+their+applications.">Recent development of two-dimensional transition metal dichalcogenides and their applications.</a> Materials Today. 20 (3), 116-130 (2017).</li><li>Xiao, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Introduction to Semiconductor Manufacturing Technology, Second Edition. , (2012).</li><li>Lin, C. Y., Zhu, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atomic-Monolayer+Two-Dimensional+Lateral+Quasi-Heterojunction+Bipolar+Transistors+with+Resonant+Tunneling+Phenomenon.">Atomic-Monolayer Two-Dimensional Lateral Quasi-Heterojunction Bipolar Transistors with Resonant Tunneling Phenomenon.</a> ACS Nano. 11 (11), 11015-11023 (2017).</li><li>Qi, J., Lan, Y. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Piezoelectric+effect+in+chemical+vapour+deposition-grown+atomic-monolayer+triangular+molybdenum+disulfide+piezotronics.">Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics.</a> Nature Communications. 6, (2015).</li></ol>

In this article, the detailed procedures of fabricating novel electronics based on 2D materials in nanometer scale are demonstrated. Since the sample preparation procedures of each application have differences with each other, the overlapped processes were treated as the protocol. Electron beam patterning combined with material location determination and metal electrode definition thus serves as the protocol here. Among the two types of devices mentioned, the whole process of 2D back-gated transistors starting at wet tra...

Since past decades, mankind has been experiencing rapid downscale in the size of transistors and, consequently, an exponential increase in the number of transistors in integrated circuits (ICs). This maintains the continuous progress of silicon-based complementary metal-oxide semiconductor (CMOS) technology1. Moreover, this current trend in the size and performance of fabricated devices are still on-track with Moore&#39;s law, which states that the number of transistors on electronic chips, as well as their performance, doubles roughly every two years2. CMOS transistors are present in most, if not all, of the electronic devices available in the market and thus making it an integral part of human lives. Due to this, there are continuous demands for improvements in chip size and performance which have been pushing the manufacturers to keep following the Moore&#39;s law track.
Unfortunately, Moore&#39;s law appears to be nearing its end due to the amount of heat generated as more silicon circuitry is squeezed into a small area2. This calls for new types of materials that can provide the same, if not better, performance as silicon and, at the same time, can be implemented in a relatively smaller scale. Recently, new promising materials have been subjects of many material science researches. Such materials as one-dimensional (1D) carbon nanotubes3,4,5,6,7, 2D graphene8,9,10,11,12, and transition metal dichalcogenides (TMDs)13,14,15,16,17,18, are good candidates that can be used as substitute for the silicon-based CMOS and continue the Moore&#39;s law track.
Fabrication of small-scale devices requires careful determination of the material&#39;s location to successfully proceed to the other fabrication techniques such as lithography and metal electrode definition. So, the method presented in this paper was designed to address this need. Compared to the traditional semiconductor fabrication techniques19, the approach presented in this paper is tailor-fitted to the development of small-scale devices which needs more attention in terms of finding the location of the material. The aim of this method is to reliably fabricate 2D nanomaterial devices, such as 2D back-gated transistors and Q-HBTs, using standard fabrication processes. This can serve as a platform for future nanodevice developments as it paves the way towards the production of future advanced nano-scale devices.
In the proceeding section, the fabrication processes for 2D materials-based devices namely, the Q-HBT and 2D back-gated transistor are discussed in detail. Electron beam patterning combined with material location determination and metal electrode definition comprises the protocol since they are required in both mentioned processes. Part 1 discusses the step-by-step fabrication process of Q-HBTs20; and part 2 demonstrates a universal approach to obtain chemical vapor deposition (CVD) molybdenum disulfide (MoS2) back-gated transistors from transfer to lift-off21, which has been completely shown in the article. The detailed process flow is illustrated in (Figure 1).

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">E-gun Evaporator</td>
			<td style="width:175px;">AST</td>
			<td style="width:255px;">PEVA 600I</td>
			<td style="width:296px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Au slug, 99.99%</td>
			<td>Well-Being Enterprise Co</td>
			<td>&#160;N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Ti slug, 99.99%</td>
			<td>Well-Being Enterprise Co</td>
			<td>&#160;N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">E-beam Lithography System</td>
			<td style="width:175px;">Elionix</td>
			<td style="width:255px;">ELS7500-EX</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Cold Wall CVD System</td>
			<td style="width:175px;">Sulfur Science</td>
			<td style="width:255px;">SCW600S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">C-plane Sapphire substrate</td>
			<td style="width:175px;">Summit-Tech</td>
			<td style="width:255px;">X171999</td>
			<td>(0001) &#177; 0.2 &#176; one side polished</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">100 nm SiO2/Si</td>
			<td style="width:175px;"></td>
			<td style="width:255px;"></td>
			<td>Fabricated in NDL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Ammonia Solution</td>
			<td style="width:175px;">BASF</td>
			<td style="width:255px;">Ammonia Solution 28% Selectipur</td>
			<td style="width:296px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Molybdenum (Mo), 99.95%</td>
			<td style="width:175px;">Summit-Tech&#160;</td>
			<td style="width:255px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Tungsten (W), 99.95%</td>
			<td style="width:175px;">Summit-Tech&#160;</td>
			<td style="width:255px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Sulfur (S), 99.5%</td>
			<td style="width:175px;">Sigma-Aldrich&#160;</td>
			<td style="width:255px;">13803</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Polymethyl Methacrylate (PMMA)</td>
			<td style="width:175px;">Microchem&#160;</td>
			<td style="width:255px;">8110788</td>
			<td>Use for transfer process</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Spin Coater</td>
			<td>Laurell&#160;</td>
			<td>WS 400B 6NPP LITE</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Acetone</td>
			<td style="width:175px;">BASF</td>
			<td style="width:255px;">Acetone EL Selectipur</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Isopropanol (IPA)</td>
			<td style="width:175px;">BASF</td>
			<td style="width:255px;">2-Propanol UPS</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Photo Resist for EBL</td>
			<td style="width:175px;">TOK</td>
			<td style="width:255px;">TDUR-P-015</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:248px;">Plasma Cleaner</td>
			<td style="width:175px;">Harrick Plasma</td>
			<td style="width:255px;">PDC-32G</td>
			<td>Oxygen plasma</td>
		</tr>
	</tbody>
</table>

a standard and reliable method to fabricate two-dimensional nanoelectronics

Two-dimensional (2D) materials have attracted huge attention due to their unique properties and potential applications. Since wafer scale synthesis of 2D materials is still in nascent stages, scientists cannot fully rely on traditional semiconductor techniques for related research. Delicate processes from locating the materials to electrode definition need to be well controlled. In this article, a universal fabrication protocol required in manufacturing nanoscale electronics, such as 2D quasi-heterojunction bipolar transistors (Q-HBT), and 2D back-gated transistors are demonstrated. This protocol includes the determination of material position, electron beam lithography (EBL), metal electrode definition, et al. A step by step narrative of the fabrication procedures for these devices are also presented. Furthermore, results show that each of the fabricated devices has achieved high performance with high repeatability. This work reveals a comprehensive description of process flow for preparing 2D nano-electronics, enables the research groups to access this information, and pave the way toward future electronics.

The device fabrication processes have been applied to several of the corresponding author&#39;s researches involving the development of 2D material devices. In this part, the results of some of these researches are presented to demonstrate the effectivity of the protocol discussed above. A monolayer of lateral WSe2-MoS2 Q-HBT20 is selected as the first example. Using the standard device fabrication processes detailed in the protocol, the monol...

Watch this Scientific Journal Video about A Standard and Reliable Method to Fabricate Two-Dimensional Nanoelectronics at JoVE.com

A Standard and Reliable Method to Fabricate Two-Dimensional Nanoelectronics

The article aims to introduce a standard and reliable fabrication procedure for the development of future low dimensional nanoelectronics.

Two-dimensional (2D) materials have attracted huge attention due to their unique properties and potential applications. Since wafer scale synthesis of 2D ...

This method can help answer key questions in the field of 2D material device fabrication, related to techniques to precisely locate 2D material samples in the preparation for later fabrication steps. The main advantage of this technique is that this is tailored to the development of small-scale devices, for which finding the location of materials is more challenging. Demonstrating the procedure will be Po-Chun Chen and Kristan, research assistants and graduate students from my laboratory.The fabrication process requires two prepared substrates. The first is back-gated silicon dioxide on silicon with titanium and gold metal pad arrays. The second substrate is sapphire with a deposited layer of molybdenum disulfide.Take the sapphire substrate with the molybdenum disulfide to a spin coater. Spin coat PMMA to cover the top of the molybdenum disulfide at 3, 500 rpm for 30 seconds. Then, move the sample to a hot plate and bake it at 120 degrees Celsius for three minutes to strengthen the PMMA coating.Next, prepare 50 milliliters of ammonia solution. Immerse the sample to separate the molybdenum disulfide from the substrate. Once the film has separated, remove it from the ammonia solution.Transfer the molybdenum disulfide film to the silicon dioxide on the silicon substrate. To enhance adhesion, bake the sample at 120 degrees Celsius for at least 30 minutes. Recover the sample and place it in 30 milliliters of acetone.After about 30 minutes, the PMMA will be removed as indicated by a change in color. Before proceeding, rinse the sample in isopropyl alcohol and use nitrogen to blow it dry. Now, prepare to perform electron-beam lithography.Use an optical microscope to measure the displacement between the target locations and the alignment marks on the sample. Based on these measurements, design the metal electrode pattern layout using software. Spin coat Photo Resist on top of the sample and ensure it covers the entire sample.Move on to soft-bake the sample at 100 degrees Celsius for 90 seconds to enhance the adhesion. At the electron-beam lithography machine, upload the design and position the sample. The alignment marks in the silicon-silicon dioxide substrate should match the corresponding marks in the design.Expose the sample to the electron beam. When done, take the sample to a hot plate. Heat the sample to 120 degrees Celsius for 90 seconds in a post-exposure bake.Next, have a container of TMAH ready as a developer and immerse the sample for 80 seconds. Then, wash the sample in 200 milliliters of deionized water for 10 seconds. Examine the sample with an optical microscope to determine if the pattern is well developed.If it is well developed, hard-bake the sample at 110 degrees Celsius for 90 seconds. The next step is to use an electron gun evaporator to deposit 100 nanometers of gold on the sample. After deposition, work to remove the Photo Resist.To dissolve the Photo Resist, prepare 100 milliliters of acetone. Immerse the sample in the acetone to perform lift-off. Monitor the process with an optical microscope and stop when only metal lines and pads remain.During characterization, choose a source and a drain electrode from those in the device, then use an anatomic force microscope to apply a load to the sample. Here Xs indicate where loads have been applied. The atomic force microscope loads results in a compressive strain on the device.Here are the current voltage characteristics of the molybdenum disulfide device at different applied forces producing compressive strain. At a given voltage, the device's current decreases with an increase in applied force and vice versa, indicating a change in the resistance of the device, a behavior that is expected for a piezo sensor. These data are for the current response of the molybdenum disulfide device for repeated compressive strains at a fixed-bias voltage of one volt.The output current barely changes with the repeated application of 10 nanonewtons of applied force, suggesting that the sensor is stable. Once mastered and performed properly, this technique can be done in 20 straight hours, including the fabrication of all transistors. After its development, this technique can serve as the platform for future nanodevice developments as it paves the way towards the production of future advanced nanoscale devices.After watching this video, you should have a good understanding of how to reliably fabricate 2D back-gated transistors using standard fabrication processes, including electron beam lithography and metal electrodeposition. Though this method caters to the development of 2D nanomaterial devices, it can also be applied to 1D materials. Don't forget that working with TMAH, ammonia solution, PMMA, and other photo resistors can be extremely dangerous and personal protection equipment should always be worn while performing this procedure.

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Engineering

A Method to Fabricate Disconnected Silver Nanostructures in 3D

The standard nanofabrication toolkit includes techniques primarily aimed at creating 2D patterns in dielectric media. Creating metal patterns on a submicron scale requires a combination of nanofabrication tools and several material processing steps. For example, steps to create planar metal structures using ultraviolet photolithography and electron-beam lithography can include sample exposure, sample development, metal deposition, and metal liftoff. To create 3D metal structures, the sequence is repeated multiple times. The complexity and difficulty of stacking and aligning multiple layers limits practical implementations of 3D metal structuring using standard nanofabrication tools. Femtosecond-laser direct-writing has emerged as a pre-eminent technique for 3D nanofabrication.1,2 Femtosecond lasers are frequently used to create 3D patterns in polymers and glasses.3-7 However, 3D metal direct-writing remains a challenge. Here, we describe a method to fabricate silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm. The method enables the fabrication of patterns not feasible using other techniques, such as 3D arrays of disconnected silver voxels.8 Disconnected 3D metal patterns are useful for metamaterials where unit cells are not in contact with each other,9 such as coupled metal dot10,11or coupled metal rod12,13 resonators. Potential applications include negative index metamaterials, invisibility cloaks, and perfect lenses.
In femtosecond-laser direct-writing, the laser wavelength is chosen such that photons are not linearly absorbed in the target medium. When the laser pulse duration is compressed to the femtosecond time scale and the radiation is tightly focused inside the target, the extremely high intensity induces nonlinear absorption. Multiple photons are absorbed simultaneously to cause electronic transitions that lead to material modification within the focused region. Using this approach, one can form structures in the bulk of a material rather than on its surface.
Most work on 3D direct metal writing has focused on creating self-supported metal structures.14-16 The method described here yields sub-micrometer silver structures that do not need to be self-supported because they are embedded inside a matrix. A doped polymer matrix is prepared using a mixture of silver nitrate (AgNO3), polyvinylpyrrolidone (PVP) and water (H2O). Samples are then patterned by irradiation with an 11-MHz femtosecond laser producing 50-fs pulses. During irradiation, photoreduction of silver ions is induced through nonlinear absorption, creating an aggregate of silver nanoparticles in the focal region. Using this approach we create silver patterns embedded in a doped PVP matrix. Adding 3D translation of the sample extends the patterning to three dimensions.

Femtosecond-laser direct-writing is frequently used to create three-dimensional (3D) patterns in polymers and glasses. However, patterning metals in 3D remains a challenge. We describe a method for fabricating silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm.

The standard nanofabrication toolkit includes  techniques primarily aimed at creating 2D patterns in dielectric media. Creating  metal patterns on a ...

Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding combined with layer transfer enables the replication of arbitrary surface patterns from a master structure onto the functional material. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes. In particular we demonstrate the fabrication of patterned transparent zinc oxide electrodes for light trapping applications in solar cells.

We describe a nanomoulding technique which allows low-cost nanoscale patterning of functional materials, materials stacks and full devices. Nanomoulding can be performed on any nanoimprinting setup and can be applied to a wide range of materials and deposition processes.

We describe a nanomoulding technique which  allows low-cost nanoscale patterning of functional materials, materials stacks  and full devices. Nanomoulding ...

A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation

The dynamic fracture of a body is a late-stage phenomenon typically studied under simplified conditions, in which a sample is deformed under uniform stress and strain rate. This can be produced by evenly loading the inner surface of a cylinder. Due to the axial symmetry, as the cylinder expands the wall is placed into a tensile hoop stress that is uniform around the circumference. While there are various techniques to generate this expansion such as explosives, electromagnetic drive, and existing gas gun techniques they are all limited in the fact that the sample cylinder must be at room temperature. We present a new method using a gas gun that facilitates experiments on cylinders from 150 K to 800 K with a consistent, repeatable loading. These highly diagnosed experiments are used to examine the effect of temperature on the fracture mechanisms responsible for failure, and their resulting influence on fragmentation statistics. The experimental geometry employs a steel ogive located inside the target cylinder, with the tip located about halfway in. A single stage light gas gun is then used to launch a polycarbonate projectile into the cylinder at 1,000 m/sec-1. The projectile impacts and flows around the rigid ogive, driving the sample cylinder from the inside. The use of a non-deforming ogive insert allows us to install temperature control hardware inside the rear of the cylinder. Liquid nitrogen (LN2) is used for cooling and a resistive high current load for heating. Multiple channels of upshifted photon Doppler velocimetry (PDV) track the expansion velocity along the cylinder enabling direct comparison to computer simulations, while High speed imaging is used to measure the strain to failure. The recovered cylinder fragments are also subject to optical and electron microscopy to ascertain the failure mechanism.

Fracture and fragmentation are late stage phenomena in dynamic loading scenarios and are typically studied using explosives. We present a technique for driving expansion using a gas gun which uniquely enables control of both loading rate and sample temperature.

The dynamic fracture of a body is a late-stage phenomenon typically studied under simplified conditions, in which a sample is deformed under uniform ...

A Cost-effective and Reliable Method to Predict Mechanical Stress in Single-use and Standard Pumps

Pumps are mainly used when transferring sterile culture broths in biopharmaceutical and biotechnological production processes. However, during the pumping process shear forces occur which can lead to qualitative and/or quantitative product loss. To calculate the mechanical stress with limited experimental expense, an oil-water emulsion system was used, whose suitability was demonstrated for drop size detections in bioreactors1. As drop breakup of the oil-water emulsion system is a function of mechanical stress, drop sizes need to be counted over the experimental time of shear stress investigations. In previous studies, the inline endoscopy has been shown to be an accurate and reliable measurement technique for drop size detections in liquid/liquid dispersions. The aim of this protocol is to show the suitability of the inline endoscopy technique for drop size measurements in pumping processes. In order to express the drop size, the Sauter mean diameter d32 was used as the representative diameter of drops in the oil-water emulsion. The results showed low variation in the Sauter mean diameters, which were quantified by standard deviations of below 15%, indicating the reliability of the measurement technique.

Shear stress investigations on an oil-water emulsion system result in drop breakup over the experimental time. To count drop sizes in pumping processes, the suitability of inline endoscopy was successfully demonstrated in this protocol.

Pumps are mainly used when transferring sterile culture broths in biopharmaceutical and biotechnological production processes. However, during the pumping ...

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

Experimental Implementation of a New Composite Fabrication Method: Exposing Bare Fibers on the Composite Surface by the Soft Layer Method

The bipolar plate is a key component in proton exchange membrane fuel cells (PEMFCs) and vanadium redox flow batteries (VRFBs). It is a multi-functional component that should have high electrical conductivity, high mechanical properties, and high productivity.
In this regard, a carbon fiber/epoxy resin composite can be an ideal material to replace the conventional graphite bipolar plate, which often leads to the catastrophic failure of the entire system because of its inherent brittleness. Though the carbon/epoxy composite has high mechanical properties and is easy to manufacture, the electrical conductivity in the through-thickness direction is poor because of the resin-rich layer that forms on its surface. Therefore, an expanded graphite coating was adopted to solve the electrical conductivity issue. However, the expanded graphite coating not only increases the manufacturing costs but also has poor mechanical properties.
In this study, a method to expose fibers on the composite surface is demonstrated. There are currently many methods that can expose fibers by surface treatment after the fabrication of the composite. This new method, however, does not require surface treatment because the fibers are exposed during the manufacture of the composite. By exposing bare carbon fibers on the surface, the electrical conductivity and mechanical strength of the composite are increased drastically.

A protocol to expose bare fibers on the composite surface by eliminating resin rich area is presented. The fibers are exposed during fabrication of the composites, not by the post surface treatment. The exposed carbon composites exhibit high electrical conductivity in the through-thickness direction and high mechanical property.

The bipolar plate is a key component in proton exchange membrane fuel cells (PEMFCs) and vanadium redox flow batteries (VRFBs). It is a multi-functional ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...

A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

In this paper, we present a protocol to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica.

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on ...

Scalable Quantum Integrated Circuits on Superconducting Two-Dimensional Electron Gas Platform

To form a coherent quantum transport in hybrid superconductor-semiconductor (S-Sm) junctions, the formation of a homogeneous and barrier-free interface between two different materials is necessary. The S-Sm junction with high interface transparency will then facilitate the observation of the induced hard superconducting gap, which is the key requirement to access the topological phases (TPs) and observation of exotic quasiparticles such as Majorana zero modes (MZM) in hybrid systems. A material platform that can support observation of TPs and allows the realization of complex and branched geometries is therefore highly demanding in quantum processing and computing science and technology. Here, we introduce a two-dimensional material system and study the proximity induced superconductivity in semiconducting two-dimensional electron gas (2DEG) that is the basis of a hybrid quantum integrated circuit (QIC). The 2DEG is a 30 nm thick In0.75Ga0.25As quantum well that is buried between two In0.75Al0.25As barriers in a heterostructure. Niobium (Nb) films are used as the superconducting electrodes to form Nb- In0.75Ga0.25As -Nb Josephson junctions (JJs) that are symmetric, planar and ballistic. Two different approaches were used to form the JJs and QICs. The long junctions were fabricated photolithographically, but e-beam lithography was used for short junctions&#8217; fabrication. The coherent quantum transport measurements as a function of temperature in the presence/absence of magnetic field B are discussed. In both device fabrication approaches, the proximity induced superconducting properties were observed in the In0.75Ga0.25As 2DEG. It was found that e-beam lithographically patterned JJs of shorter lengths result in observation of induced superconducting gap at much higher temperature ranges. The results that are reproducible and clean suggesting that the hybrid 2D JJs and QICs based on In0.75Ga0.25As quantum wells could be a promising material platform to realize the real complex and scalable electronic and photonic quantum circuitry and devices.

Quantum integrated circuits (QICs) consisting of array of planar and ballistic Josephson junctions (JJs) based on In0.75Ga0.25As two-dimensional electron gas (2DEG) is demonstrated. Two different methods for fabrication of the two-dimensional (2D) JJs and QICs are discussed followed by the demonstration of quantum transport measurements in sub-Kelvin temperatures.

To form a coherent quantum transport in hybrid superconductor-semiconductor (S-Sm) junctions, the formation of a homogeneous and barrier-free interface ...