We acknowledge Dr. Keng Hsu (University of Louisville) for insights regarding this work; University of Illinois&#39;s Frederick Seitz Laboratory and, in memoriam, staff member Scott Maclaren; Arizona State University&#39;s LeRoy Eyring Center for Solid State Science; and the Science Foundation Arizona under the Bis grove Scholars Award.

<ol>
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P., Lin, Y., Avagyan, A., Sivaguru, M., Hsu, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+Imprinting+of+Porous+Silicon+via+Metal-Assisted+Chemical+Etching.">Direct Imprinting of Porous Silicon via Metal-Assisted Chemical Etching.</a> Advanced Functional Materials. 26 (17), 2929-2939 (2016).</li><li>Azeredo, B., Hsu, K., Ferreira, P. 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We do not have anything to disclose.

Mac-Imprint stamps and prepatterned Si chips (p-type, [100] orientation, 1-10 Ohm&#8729;cm) were prepared according to sections 1 and 2 of the protocol, respectively. The Mac-Imprint of prepatterned Si chip with stamps containing 3D hierarchical patterns was performed according to section 3 of the protocol (Figure 9). As shown in Figure 9a, different configurations of Mac-Imprint were applied: solid Si with solid Au (left), porous Si with solid ...

Three-dimensional micro- and nanoscale patterning and texturization of semiconductors enables numerous applications in various areas, such as optoelectronics1,2, photonics3, antireflective surfaces4, super hydrophobic, and self-cleaning surfaces5,6 among others. Prototyping and mass-producing 3D and hierarchical patterns has been successfully accomplished for polymeric films by soft lithography and nanoimprinting lithography with sub-20 nm resolution. However, transferring such 3D polymeric patterns into Si requires the etching selectivity of a mask pattern during reactive ion etching and thus limits the aspect ratio, and induces shape distortions and surface roughness due to scalloping effects7,8.
A new method called Mac-Imprint has been achieved for parallel and direct patterning of porous9 and solid Si wafers10,11 as well as solid GaAs wafers12,13,14. Mac-Imprint is a contact-based wet etching technique that requires contact between substrate and a noble metal-coated stamp possessing 3D features in the presence of an etching solution (ES) composed of HF and an oxidant (e.g., H2O2 in the case of Si Mac-Imprint). During the etching, two reactions occur simultaneously15,16: a cathodic reaction (i.e., the H2O2 reduction at the noble metal, during which positive charge carriers [holes] are generated and subsequently injected into Si17) and an anodic reaction (i.e., Si dissolution, during which the holes are consumed). After sufficient time in contact, the stamp&#39;s 3D features are etched into the Si wafer. Mac-Imprint has numerous advantages over conventional lithographical methods, such as high throughput, compatibility with roll-to-plate and roll-to-roll platforms, amorphous, mono- and polycrystalline Si and III-V semiconductors. Mac-Imprint stamps can be reused multiple times. Additionally, the method can deliver a sub-20 nm etching resolution that is compatible with contemporary direct writing methods.
The key to attaining high-fidelity imprinting is the diffusion pathway to the etching front (i.e., contact interface between catalyst and substrate). The work of Azeredo et al.9 first demonstrated that ES diffusion is enabled through a porous Si network. Torralba et al.18, reported that in order to realize solid Si Mac-Imprint the ES diffusion is enabled through a porous catalyst. Bastide et al.19 and Sharstniou et al.20 further investigated the catalyst porosity influence on ES diffusion. Thus, the concept of Mac-Imprint has been tested in three configurations with distinct diffusion pathways.
In the first configuration, the catalyst and substrate are solid, providing no initial diffusion pathway. The lack of reactant diffusion leads to a secondary reaction during imprinting that forms a layer of porous Si on the substrate around the edge of the catalyst-Si interface. The reactants are subsequently depleted, and the reaction stops, resulting in no discernable pattern transfer fidelity between the stamp and substrate. In the second and third configurations, the diffusion pathways are enabled through porous networks introduced either in the substrate (i.e., porous Si) or in the catalyst (i.e., porous gold) and high pattern transfer accuracy is attained. Thus, the mass transport through porous materials plays a critical role in enabling the diffusion of reactants and reaction products to and away from the contact interface9,18,19,20. A schematic of all three configurations is shown in Figure 1.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61040/61040fig1.jpg" /> 
Figure 1: Schematics of Mac-Imprint configurations. This figure highlights the role of porous materials in enabling the diffusion of reacting species through the substrate (i.e., case II: porous Si) or in the stamp (i.e., case III: catalyst thin film made of porous gold). <a href="https://www.jove.com/files/ftp_upload/61040/61040fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In this paper, the Mac-Imprint process is thoroughly discussed, including stamp preparation and substrate pretreatment along with Mac-Imprint itself. The substrate pretreatment section within the protocol includes Si wafer cleaning and Si wafer patterning with dry etching and substrate anodization (optional). Further, a stamp preparation section is subdivided into several procedures: 1) PDMS replica molding of Si master mold; 2) UV nanoimprinting of a photoresist layer in order to transfer the PDMS pattern; and 3) catalytic layer deposition via magnetron sputtering followed by dealloying (optional). Finally, in the Mac-Imprint section the Mac-Imprint setup along with the Mac-Imprint results (i.e., Si surface 3D hierarchical patterning) is presented.

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			<td>Acetone, &#62;99.5%, ACS reagent</td>
			<td>Sigma-Aldrich</td>
			<td>67-64-1</td>
			<td>CAUTION, chemical</td>
		</tr>
		<tr>
			<td>Ammonium fluoride, &#62;98%, ACS grade</td>
			<td>Sigma-Aldrich</td>
			<td>12125-01-8</td>
			<td>CAUTION, hazardous</td>
		</tr>
		<tr>
			<td>Ammonium hydroxide solution, 28-30%, ACS reagent</td>
			<td>Sigma-Aldrich</td>
			<td>1336-21-6</td>
			<td>CAUTION, hazardous</td>
		</tr>
		<tr>
			<td>AZ 400K developer</td>
			<td>Microchemicals</td>
			<td>AZ 400K</td>
			<td>CAUTION, chemical</td>
		</tr>
		<tr>
			<td>BenchMark 800 Etch</td>
			<td>Axic</td>
			<td>BenchMark 800</td>
			<td>Reactive ion etching</td>
		</tr>
		<tr>
			<td>Chromium target, 2&#34; x 0.125&#34;, 99.95% purity</td>
			<td>ACI alloys</td>
			<td>ADM0913</td>
			<td>Magnetron sputter chromium target</td>
		</tr>
		<tr>
			<td>CTF 12</td>
			<td>Carbolite Gero</td>
			<td>C12075-700-208SN</td>
			<td>Tube furnace</td>
		</tr>
		<tr>
			<td>Desiccator</td>
			<td>Fisher scientific Chemglass life sciences</td>
			<td>CG122611</td>
			<td>Desiccator</td>
		</tr>
		<tr>
			<td>F6T5/BLB</td>
			<td>Eiko</td>
			<td>F6T5/BLB 6W</td>
			<td>UV bulb</td>
		</tr>
		<tr>
			<td>Gold target, 2&#34; x 0.125&#34;, 99.99% purity</td>
			<td>ACI alloys</td>
			<td>N/A</td>
			<td>Magnetron sputter gold target</td>
		</tr>
		<tr>
			<td>Hotplate KW-4AH</td>
			<td>Chemat tecnologie</td>
			<td>KW-4AH</td>
			<td>Leveled hotplate with uniform temperature profile</td>
		</tr>
		<tr>
			<td>Hydrofluoric acid, 48%, ACS reagent</td>
			<td>Sigma-Aldrich</td>
			<td>7664-39-3</td>
			<td>CAUTION, extremly hazardous</td>
		</tr>
		<tr>
			<td>Hydrogen peroxide, 30%, ACS reagent</td>
			<td>Fisher Chemical</td>
			<td>7722-84-1</td>
			<td>CAUTION, hazardous</td>
		</tr>
		<tr>
			<td>Isopropyl alcohol, &#62;99.5%, ACS reagent</td>
			<td>LabChem</td>
			<td>67-63-0</td>
			<td>CAUTION, chemical</td>
		</tr>
		<tr>
			<td>MLP-50</td>
			<td>Transducer Techniques</td>
			<td>MLP-50</td>
			<td>Load cell</td>
		</tr>
		<tr>
			<td>Nitric acid, 70%, ACS grade</td>
			<td>SAFC</td>
			<td>7697-37-2</td>
			<td>CAUTION, hazardous</td>
		</tr>
		<tr>
			<td>NSC-3000</td>
			<td>Nano-master</td>
			<td>NSC-3000</td>
			<td>Magnetron sputter</td>
		</tr>
		<tr>
			<td>Potassium hydroxide, 45%, Certified</td>
			<td>Fisher Chemical</td>
			<td>1310-58-3</td>
			<td>CAUTION, chemical</td>
		</tr>
		<tr>
			<td>Rocker 800 vacuum pump, 110V/60Hz</td>
			<td>Rocker</td>
			<td>1240043</td>
			<td>Oil-free vacuum pump</td>
		</tr>
		<tr>
			<td>Silicon master mold</td>
			<td>NILT</td>
			<td>SMLA_V1</td>
			<td>Silicon chip with pattern</td>
		</tr>
		<tr>
			<td>Silicon wafers, prime grade</td>
			<td>University wafer</td>
			<td>783</td>
			<td>Si wafer</td>
		</tr>
		<tr>
			<td>Silver target, 2&#34; x 0.125&#34;, 99.99% purity</td>
			<td>ACI alloys</td>
			<td>HER2318</td>
			<td>Magnetron sputter silver target</td>
		</tr>
		<tr>
			<td>SP-300</td>
			<td>BioLogic</td>
			<td>SP-300</td>
			<td>Potentiostat</td>
		</tr>
		<tr>
			<td>SPIN 150i</td>
			<td>Spincoating</td>
			<td>SPIN 150i</td>
			<td>Spin coater</td>
		</tr>
		<tr>
			<td>SPR 200-7.0 positive photoresist</td>
			<td>Microchem</td>
			<td>SPR 220-7.0</td>
			<td>CAUTION, chemical</td>
		</tr>
		<tr>
			<td>Stirring hotplate</td>
			<td>Thermo scientific Cimarec+</td>
			<td>SP88857100</td>
			<td>General purpose hotplate</td>
		</tr>
		<tr>
			<td>SU-8 2015 negative photoresist</td>
			<td>Microchem</td>
			<td>SU-8 2015</td>
			<td>CAUTION, chemical</td>
		</tr>
		<tr>
			<td>SYLGARD 184 Silicone elastomere kit</td>
			<td>DOW</td>
			<td>4019862</td>
			<td>CAUTION, chemical</td>
		</tr>
		<tr>
			<td>T-LSR150B</td>
			<td>Zaber Technologies</td>
			<td>T-LSR150B-KT04U</td>
			<td>Motorized linear stage</td>
		</tr>
		<tr>
			<td>Trichloro(1H,1H,2H,2H-perfluorooctyl)silane (PFOCS), 97%</td>
			<td>Sigma-Aldrich</td>
			<td>78560-45-9</td>
			<td>CAUTION, hazardous</td>
		</tr>
	</tbody>
</table>

metal-assisted electrochemical nanoimprinting of porous and solid silicon wafers

Metal-assisted electrochemical imprinting (Mac-Imprint) is a combination of metal-assisted chemical etching (MACE) and nanoimprint lithography that is capable of direct patterning 3D micro- and nanoscale features in monocrystalline group IV (e.g., Si) and III-V (e.g., GaAs) semiconductors without the need of sacrificial templates and lithographical steps. During this process, a reusable stamp coated with a noble metal catalyst is brought in contact with a Si wafer in the presence of a hydrofluoric acid (HF) and hydrogen peroxide (H2O2) mixture, which leads to the selective etching of Si at the metal-semiconductor contact interface. In this protocol, we discuss the stamp and substrate preparation methods applied in two Mac-Imprint configurations: (1) Porous Si Mac-Imprint with a solid catalyst; and (2) Solid Si Mac-Imprint with a porous catalyst. This process is high throughput and is capable of centimeter-scale parallel patterning with sub-20 nm resolution. It also provides low defect density and large area patterning in a single operation and bypasses the need for dry etching such as deep reactive ion etching (DRIE).

Scanning electron microscope (SEM) images, optical microscope scans (Figure 9), and atomic force microscopy (AFM) scans (Figure 10) were obtained in order to study the morphological properties of the Mac-Imprint stamps and imprinted Si surfaces. The cross-sectional profile of the imprinted solid Si was compared to that of the used porous Au stamp (Figure 10). Pattern transfer fidelity and porous Si g...

Watch this Scientific Journal Video about Metal-Assisted Electrochemical Nanoimprinting of Porous and Solid Silicon Wafers at JoVE.com

Metal-Assisted Electrochemical Nanoimprinting of Porous and Solid Silicon Wafers

A protocol for metal-assisted chemical imprinting of 3D microscale features with sub-20 nm shape accuracy into solid and porous silicon wafers is presented.

Metal-assisted electrochemical imprinting (Mac-Imprint) is a combination of metal-assisted chemical etching (MACE) and nanoimprint lithography that is ...

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3.9K Views.  Arizona State University. A protocol for metal-assisted chemical imprinting of 3D microscale features with sub-20 nm shape accuracy into solid and porous silicon wafers is presented.

Video: Metal-Assisted Electrochemical Nanoimprinting of Porous and Solid Silicon Wafers

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 ...

Fabrication of VB2/Air Cells for Electrochemical Testing

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.

Fabrication of VB2/Air Cells for Electrochemical Testing

A protocol is presented to study multi-electron metal/air battery systems by using previous technology developed for the zinc/air cell. Electrochemical testing is then performed on fabricated batteries to evaluate performance.

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for ...

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms.
In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station.

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra ...

Fabrication of Uniform Nanoscale Cavities via Silicon Direct Wafer Bonding

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned and bonded silicon wafers. Unlike confinements in porous materials often used for these types of experiments3, bonded wafers provide predesigned uniform spaces for confinement. The geometry of each cell is well known, which removes a large source of ambiguity in the interpretation of data.
Exceptionally flat, 5 cm diameter, 375 &#181;m thick Si wafers with about 1 &#181;m variation over the entire wafer can be obtained commercially (from Semiconductor Processing Company, for example). Thermal oxide is grown on the wafers to define the confinement dimension in the z-direction. A pattern is then etched in the oxide using lithographic techniques so as to create a desired enclosure upon bonding. A hole is drilled in one of the wafers (the top) to allow for the introduction of the liquid to be measured. The wafers are cleaned2 in RCA solutions and then put in a microclean chamber where they are rinsed with deionized water4. The wafers are bonded at RT and then annealed at ~1,100 &#176;C. This forms a strong and permanent bond. This process can be used to make uniform enclosures for measuring thermal and hydrodynamic properties of confined liquids from the nanometer to the micrometer scale.

A method for permanently bonding two silicon wafers so as to realize a uniform enclosure is described. This includes wafer preparation, cleaning, RT bonding, and annealing processes. The resulting bonded wafers (cells) have uniformity of enclosure ~1%1,2. The resulting geometry allows for measurements of confined liquids and gasses.

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned ...

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic electrolyte, and an O2-breathing cathode. The aprotic electrolyte is a solution of lithium salt with aprotic solvent; and porous carbon is commonly used as the cathode substrate. To improve the performance, an electrocatalyst is deposited onto the porous carbon substrate by certain deposition methods, such as atomic layer deposition (ALD) and wet-chemistry reaction. The as-prepared cathode materials are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray absorption near edge structure (XANES). A Swagelok-type cell, sealed in a glass chamber filled with pure O2, is used for the electrochemical test on a battery test system. The cells are tested under either capacity-controlled mode or voltage controlled mode. The reaction products are investigated by electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and Raman spectroscopy to study the possible pathway of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This protocol demonstrates a systematic and efficient arrangement of routine tests of the aprotic Li-O2 battery, including the electrochemical test and characterization of battery materials.

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

A protocol for the electrochemical testing of an aprotic Li-O2 battery with the preparation of electrodes and electrolytes and an introduction of the frequently used methods of characterization is presented here.

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. The results of studies in which the etching current and the molarity of the NaOH solution used in the etching process were varied are presented. The investigation of the geometry of the tips, by imaging them with a scanning electron microscope, and by operating them in field emission mode is also described. The field emission tips produced are intended to be used as an electron beam source for ion production via electron impact ionization of background gas or vapor in Penning trap mass spectrometry applications.

A method for electrochemically etching field emission tips is presented. Etching parameters are characterized and the operation of the tips in field emission mode is investigated.

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. ...

Fabrication of White Light-emitting Electrochemical Cells with Stable Emission from Exciplexes

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active layer which consists of blue-fluorescent poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) and &#960;-conjugated triphenylamine molecules. This white light emission originates from exciplexes formed between PFD and amines in electronically excited states. A device containing PFD, 4,4&#39;,4&#39;&#39;-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), Poly(ethylene oxide) and K2CF3SO3 showed white light emission with Commission internationale de l&#39;&#233;clairage (CIE) coordinates of (0.33, 0.43) and a Color Rendering Index (CRI) of Ra = 73 at an applied voltage of 3.5 V. Constant voltage measurements showed that the CIE coordinates of (0.27, 0.37), Ra of 67, and the emission color observed immediately after application of a voltage of 5 V were nearly unchanged and stable after 300 sec.

The authors present a method for fabricating stable white-light-emitting electrochemical cells utilizing emission from exciplexes formed between a blue-emitting fluorene polymer and aromatic amines.

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active ...

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser (laser-SARPES), and demonstrate a power of this technique for studying solid state physics. Laser-SARPES achieves two great capabilities. Firstly, by examining orbital selection rule of linearly polarized lasers, orbital selective excitation can be carried out in SAPRES experiment. Secondly, the technique can show full information of a variation of the spin quantum axis as a function of the light polarization. To demonstrate the power of the collaboration of these capabilities in laser-SARPES, we apply this technique for the investigations of spin-orbit coupled surface states of Bi2Se3. This technique affords to decompose spin and orbital components from the spin-orbit coupled wavefunctions. Moreover, as a representative advantage of using the direct spin detection collaborated with the polarization-variable laser, the technique unambiguously visualizes the light polarization dependence of the spin quantum axis in three-dimension. Laser-SARPES dramatically increases a capability of photoemission technique.

Here, we combine polarization-variable 7-eV laser with spin- and angle-resolved photoemission technique to visualize the spin-orbital coupling effect in solid states.

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser ...

A Silicon-tipped Fiber-optic Sensing Platform with High Resolution and Fast Response

In this article, we introduce an innovative and practically promising fiber-optic sensing platform (FOSP) that we proposed and demonstrated recently. This FOSP relies on a silicon Fabry-Perot interferometer (FPI) attached to the fiber end, referred to as Si-FOSP in this work. The Si-FOSP generates an interferogram determined by the optical path length (OPL) of the silicon cavity. Measurand alters the OPL and thus shifts the interferogram. Due to the unique optical and thermal properties of the silicon material, this Si-FOSP exhibits an advantageous performance in terms of sensitivity and speed. Furthermore, the mature silicon fabrication industry endows the Si-FOSP with excellent reproducibility and low cost toward practical applications. Depending on the specific applications, either a low-finesse or high-finesse version will be utilized, and two different data demodulation methods will be adopted accordingly. Detailed protocols for fabricating both versions of the Si-FOSP will be provided. Three representative applications and their according results will be shown. The first one is a prototype underwater thermometer for profiling the ocean thermoclines, the second one is a flow meter to measure flow speed in the ocean, and the last one is a bolometer used for monitoring exhaust radiation from magnetically confined high-temperature plasma.

This work reports an innovative silicon-tipped fiber-optic sensing platform (Si-FOSP) for high-resolution and fast-response measurement of a variety of physical parameters, such as temperature, flow, and radiation. Applications of this Si-FOSP span from oceanographic research, mechanical industry, to fusion energy research.

In this article, we introduce an innovative and practically promising fiber-optic sensing platform (FOSP) that we proposed and demonstrated recently. This ...