Work function seen with sub-meV precision through laser photoemission

Ishida, Y.; Jung, Ji-Ung; Kim, Min‐Soo; Kwon, Junyoung; Kim, Younsik; Chung, Dae Kyun; Song, Inkyung; Kim, Changyoung; Otsu, Toshio; Kobayashi, Yohei

doi:10.1038/s42005-020-00426-x

Cited by 13 publications

(10 citation statements)

References 69 publications

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“…[ 31 ] On the contrary, Au work function ( Φ Pt = 5.2 eV) is lower than hematite, resulting in a downward bending of hematite energy bands and in the formation of an Ohmic contact. [ 43 ] On these bases, a higher charge separation and speed would be expected for hematite/Au Janus microrobots. However, our findings indicate that mixed potential difference and catalytic activity of the metal (Pt is more catalytic than Au for hydrogen evolution reaction) play the major role in determining the speed of semiconductor/metal Janus microrobots.…”

Section: Resultsmentioning

confidence: 99%

Breaking Polymer Chains with Self‐Propelled Light‐Controlled Navigable Hematite Microrobots

Urso

Ussia

Pumera

2021

Adv Funct Materials

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The increasing use of polymers has led to an uncontrollable accumulation of polymer waste in the environment, evidencing the urgent need for effective and definitive strategies to degrade them. Here, self‐propelled light‐powered magnetic field‐navigable hematite/metal Janus microrobots that can actively move, capture, and degrade polymers are presented. Janus microrobots are fabricated by asymmetrically depositing different metals on hematite microspheres prepared by low‐cost and large‐scale chemical synthesis. All microrobots exhibit fuel‐free motion capability, with light‐controlled on/off switching of motion and magnetic field‐controlled directionality. Higher speeds are observed for bimetallic coatings with respect to single metals. This is due to their larger mixed potential difference with hematite as indicated by Tafel measurements. As a model for polymers, the total degradation of high molecular weight polyethylene glycol is demonstrated by matrix‐assisted laser desorption/ionization mass spectrometry. This result is attributed to the active motion of microrobots, enhanced electrostatic capture of polymer chains, improved charge separation at the hematite/metal interface, and catalyzed photo‐Fenton reaction. This work opens the route toward the degradation of polymers and plastics in water using light.

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Section: Resultsmentioning

confidence: 99%

Breaking Polymer Chains with Self‐Propelled Light‐Controlled Navigable Hematite Microrobots

Urso

Ussia

Pumera

2021

Adv Funct Materials

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“…2(b) shows low energy side of ARPES spectra with bias voltage for same materials. Note that all the spectra have parabolic lowenergy cutoff for which the parabolic shape comes from the non-zero in-plane momentum of photoelectrons at the cutoff [22]. As the E L in equation ( 1) should be measured at the vertex of the parabola, the energy distribution curve (EDC) at the vertex position was used to determine the E L (see Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Work function measurements were performed with a 5.988 eV fiber-laser source [21] with a lab-based system at Seoul National University [22]. The energy resolution (convolution of the analyzer's resolution and the bandwith of the light source) acquired from polycrystalline gold with no bias voltage is about 12 meV.…”

Section: Experimental Methodsmentioning

confidence: 99%

Effect of the sample work function on alkali metal dosing induced electronic structure change

Jung,

Ishida,

Kim

et al. 2021

Preprint

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Alkali metal dosing (AMD) has been widely used as a way to control doping without chemical substitution. This technique, in combination with angle resolved photoemission spectroscopy (ARPES), often provides an opportunity to observe unexpected phenomena. However, the amount of transferred charge and the corresponding change in the electronic structure vary significantly depending on the material. Here, we report study on the correlation between the sample work function and alkali metal induced electronic structure change for three iron-based superconductors: FeSe, Ba(Fe0.94Co0.06)2As2 and NaFeAs which share a similar Fermi surface topology. Electronic structure change upon monolayer of alkali metal dosing and the sample work function were measured by ARPES. Our results show that the degree of electronic structure change is proportional to the difference between the work function of the sample and Mulliken's absolute electronegativity of the dosed alkali metal. This finding provides a possible way to estimate the AMD induced electronic structure change.

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“…S9). [35,36] In AR-LEIPS measurement, an electron beam with the kinetic energy in the range between 0 and 5 eV from an electron source was incident to the sample surface. The S2).…”

Section: Methodsmentioning

confidence: 99%

Accessing the Conduction Band Dispersion in CH₃NH₃PbI₃ Single Crystals

Yang

Sato

Orio

et al. 2021

J. Phys. Chem. Lett.

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The conduction band structure in methylammonium lead iodide (CH3NH3PbI3) was studied both by angle-resolved two-photon photoemission spectroscopy (AR-2PPE) with low-photon intensity and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy dispersion of the conduction band along the ΓM direction was observed by these independent methods under different temperatures, and the dispersion was found to be consistent with band calculations under the cubic phase. The effective mass of the electrons at the Γ point was estimated to be (0.20±0.05)m0 at 90 K. The observed energy position was largely different between the AR-LEIPS and AR-2PPE, demonstrating the electron correlation effects on the band structures. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.

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Work function seen with sub-meV precision through laser photoemission

Cited by 13 publications

References 69 publications

Breaking Polymer Chains with Self‐Propelled Light‐Controlled Navigable Hematite Microrobots

Breaking Polymer Chains with Self‐Propelled Light‐Controlled Navigable Hematite Microrobots

Effect of the sample work function on alkali metal dosing induced electronic structure change

Accessing the Conduction Band Dispersion in CH₃NH₃PbI₃ Single Crystals

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Work function seen with sub-meV precision through laser photoemission

Cited by 13 publications

References 69 publications

Breaking Polymer Chains with Self‐Propelled Light‐Controlled Navigable Hematite Microrobots

Breaking Polymer Chains with Self‐Propelled Light‐Controlled Navigable Hematite Microrobots

Effect of the sample work function on alkali metal dosing induced electronic structure change

Accessing the Conduction Band Dispersion in CH3NH3PbI3 Single Crystals

Contact Info

Product

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Accessing the Conduction Band Dispersion in CH₃NH₃PbI₃ Single Crystals