All Publications

  • Emergent phenomena at oxide interfaces studied with standing-wave photoelectron spectroscopy JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Kuo, C., Conti, G., Rault, J. E., Schneider, C. M., Nemsak, S., Gray, A. X. 2022; 40 (2)

    View details for DOI 10.1116/6.0001584

    View details for Web of Science ID 000741082300002

  • Probing the polar-nonpolar oxide interfaces using resonant x-ray standing wave techniques JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Kuo, C., Lin, S., Chuang, Y. 2022; 40 (1)

    View details for DOI 10.1116/6.0001484

    View details for Web of Science ID 000730515900002

  • Orbital contributions in the element-resolved valence electronic structure of Bi2Se3 PHYSICAL REVIEW B Kuo, C., Lin, S., Rueff, J., Chen, Z., Aguilera, I., Bihlmayer, G., Plucinski, L., Graff, I. L., Conti, G., Vartanyants, I. A., Schneider, C. M., Fadley, C. S. 2021; 104 (24)
  • High resolution depth profiling using near-total-reflection hard x-ray photoelectron spectroscopy JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Rault, J. E., Kuo, C., Martins, H. P., Conti, G., Nemsak, S. 2021; 39 (6)

    View details for DOI 10.1116/6.0001289

    View details for Web of Science ID 000711195300001

  • Interface Carriers and Enhanced Electron-Phonon Coupling Effect in Al2O3/TiO2 Heterostructure Revealed by Resonant Inelastic Soft X-Ray Scattering ADVANCED FUNCTIONAL MATERIALS Shao, Y., Kuo, C., Feng, X., Chuang, Y., Seok, T., Choi, J., Park, T., Cho, D. 2021
  • Two-dimensional electron systems in perovskite oxide heterostructures: Role of the polarity-induced substitutional defects PHYSICAL REVIEW MATERIALS Lin, S., Kuo, C., Shao, Y., Chuang, Y., Geessinck, J., Huijben, M., Rueff, J., Graff, I. L., Conti, G., Peng, Y., Bostwick, A., Gullikson, E., Gullikson, E., Nemsak, S., Vailionis, A., Gauquelin, N., Verbeeck, J., Ghiringhelli, G., Schneider, C. M., Fadley, C. S. 2020; 4 (11)
  • Hard x-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction JOURNAL OF APPLIED PHYSICS Conlon, C. S., Conti, G., Nemsak, S., Palsson, G., Moubah, R., Kuo, C., Gehlmann, M., Ciston, J., Rault, J., Rueff, J., Salmassi, F., Stolte, W., Rattanachata, A., Lin, S., Keqi, A., Saw, A., Hjorvarsson, B., Fadley, C. S. 2019; 126 (7)

    View details for DOI 10.1063/1.5089556

    View details for Web of Science ID 000483849000004

  • Depth-resolved resonant inelastic x-ray scattering at a superconductor/half-metallic-ferromagnet interface through standing wave excitation PHYSICAL REVIEW B Kuo, C., Lin, S., Ghiringhelli, G., Peng, Y., De Luca, G., Di Castro, D., Betto, D., Gehlmann, M., Wijnands, T., Huijben, M., Meyer-Ilse, J., Gullikson, E., Kortright, J. B., Vailionis, A., Gauquelin, N., Verbeeck, J., Gerber, T., Balestrino, G., Brookes, N. B., Braicovich, L., Fadley, C. S. 2018; 98 (23)
  • Atomic-layer-resolved composition and electronic structure of the cuprate Bi2Sr2CaCu2O8+delta from soft x-ray standing-wave photoemission PHYSICAL REVIEW B Kuo, C., Lin, S., Conti, G., Pi, S., Moreschini, L., Bostwick, A., Meyer-Ilse, J., Gullikson, E., Kortright, J. B., Nemsak, S., Rault, J. E., Le Fevre, P., Bertran, F., Santander-Syro, A. F., Vartanyants, I. A., Pickett, W. E., Saint-Martin, R., Taleb-Ibrahimi, A., Fadley, C. S. 2018; 98 (15)
  • Interface properties and built-in potential profile of a LaCrO3/SrTiO3 superlattice determined by standing-wave excited photoemission spectroscopy PHYSICAL REVIEW B Lin, S., Kuo, C., Comes, R. B., Rault, J. E., Rueff, J., Nemsak, S., Taleb, A., Kortright, J. B., Meyer-Ilse, J., Gullikson, E., Sushko, P., Spurgeon, S. R., Gehlmann, M., Bowden, M. E., Plucinski, L., Chambers, S. A., Fadley, C. S. 2018; 98 (16)
  • Element- and momentum-resolved electronic structure of the dilute magnetic semiconductor manganese doped gallium arsenide NATURE COMMUNICATIONS Nemsak, S., Gehlmann, M., Kuo, C., Lin, S., Schlueter, C., Mlynczak, E., Lee, T., Plucinski, L., Ebert, H., Di Marco, I., Minar, J., Schneider, C. M., Fadley, C. S. 2018; 9: 3306


    The dilute magnetic semiconductors have promise in spin-based electronics applications due to their potential for ferromagnetic order at room temperature, and various unique switching and spin-dependent conductivity properties. However, the precise mechanism by which the transition-metal doping produces ferromagnetism has been controversial. Here we have studied a dilute magnetic semiconductor (5% manganese-doped gallium arsenide) with Bragg-reflection standing-wave hard X-ray angle-resolved photoemission spectroscopy, and resolved its electronic structure into element- and momentum- resolved components. The measured valence band intensities have been projected into element-resolved components using analogous energy scans of Ga 3d, Mn 2p, and As 3d core levels, with results in excellent agreement with element-projected Bloch spectral functions and clarification of the electronic structure of this prototypical material. This technique should be broadly applicable to other multi-element materials.

    View details for DOI 10.1038/s41467-018-05823-z

    View details for Web of Science ID 000441865700002

    View details for PubMedID 30120237

    View details for PubMedCentralID PMC6098022

  • Characterization of free-standing InAs quantum membranes by standing wave hard x-ray photoemission spectroscopy APL MATERIALS Conti, G., Nemsak, S., Kuo, C., Gehlmann, M., Conlon, C., Keqi, A., Rattanachata, A., Karslioglu, O., Mueller, J., Sethian, J., Bluhm, H., Rault, J. E., Rueff, J. P., Fang, H., Javey, A., Fadley, C. S. 2018; 6 (5)

    View details for DOI 10.1063/1.5022379

    View details for Web of Science ID 000433944800007

  • Nitride Semiconductor Nanorod Heterostructures for Full-Color and White-Light Applications III-NITRIDE SEMICONDUCTOR OPTOELECTRONICS Gwo, S., Lu, Y. J., Lin, H. W., Kuo, C. T., Wu, C. L., Lu, M. Y., Chen, L. J., Mi, Z., Jagadish, C. 2017; 96: 341–84
  • Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures SCIENTIFIC REPORTS Gray, B. A., Middey, S., Conti, G., Gray, A. X., Kuo, C., Kaiser, A. M., Ueda, S., Kobayashi, K., Meyers, D., Kareev, M., Tung, I. C., Liu, J., Fadley, C. S., Chakhalian, J., Freeland, J. W. 2016; 6: 33184


    The superconductor-to-insulator transition (SIT) induced by means such as external magnetic fields, disorder or spatial confinement is a vivid illustration of a quantum phase transition dramatically affecting the superconducting order parameter. In pursuit of a new realization of the SIT by interfacial charge transfer, we developed extremely thin superlattices composed of high Tc superconductor YBa2Cu3O7 (YBCO) and colossal magnetoresistance ferromagnet La0.67Ca0.33MnO3 (LCMO). By using linearly polarized resonant X-ray absorption spectroscopy and magnetic circular dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a complete picture of the interfacial carrier doping in cuprate and manganite atomic layers, leading to the transition from superconducting to an unusual Mott insulating state emerging with the increase of LCMO layer thickness. In addition, contrary to the common perception that only transition metal ions may respond to the charge transfer process, we found that charge is also actively compensated by rare-earth and alkaline-earth metal ions of the interface. Such deterministic control of Tc by pure electronic doping without any hindering effects of chemical substitution is another promising route to disentangle the role of disorder on the pseudo-gap and charge density wave phases of underdoped cuprates.

    View details for DOI 10.1038/srep33184

    View details for Web of Science ID 000383191400001

    View details for PubMedID 27627855

    View details for PubMedCentralID PMC5024130

  • X-ray Absorption Spectroscopy Study of the Effect of Rh doping in Sr2IrO4 SCIENTIFIC REPORTS Sohn, C. H., Cho, D., Kuo, C., Sandilands, L. J., Qi, T. F., Cao, G., Noh, T. W. 2016; 6: 23856


    We investigate the effect of Rh doping in Sr2IrO4 using X-ray absorption spectroscopy (XAS). We observed appearance of new electron-addition states with increasing Rh concentration (x in Sr2Ir1-xRhxO4) in accordance with the concept of hole doping. The intensity of the hole-induced state is however weak, suggesting weakness of charge transfer (CT) effect and Mott insulating ground states. Also, Ir Jeff = 1/2 upper Hubbard band shifts to lower energy as x increases up to x = 0.23. Combined with optical spectroscopy, these results suggest a hybridisation-related mechanism, in which Rh doping can weaken the (Ir Jeff = 1/2)-(O 2p) orbital hybridisation in the in-planar Rh-O-Ir bond networks.

    View details for DOI 10.1038/srep23856

    View details for Web of Science ID 000373049800001

    View details for PubMedID 27025538

    View details for PubMedCentralID PMC4812298

  • The energy band alignment at the interface between mechanically exfoliated few-layer NiPS3 nanosheets and ZnO CURRENT APPLIED PHYSICS Kuo, C., Balamurugan, K., Shiu, H., Park, H., Sinn, S., Neumann, M., Han, M., Chang, Y., Chen, C., Kim, H., Park, J., Noh, T. 2016; 16 (3): 404–8
  • Exfoliation and Raman Spectroscopic Fingerprint of Few-Layer NiPS3 Van der Waals Crystals SCIENTIFIC REPORTS Kuo, C., Neumann, M., Balamurugan, K., Park, H., Kang, S., Shiu, H., Kang, J., Hong, B., Han, M., Noh, T., Park, J. 2016; 6: 20904


    The range of mechanically cleavable Van der Waals crystals covers materials with diverse physical and chemical properties. However, very few of these materials exhibit magnetism or magnetic order, and thus the provision of cleavable magnetic compounds would supply invaluable building blocks for the design of heterostructures assembled from Van der Waals crystals. Here we report the first successful isolation of monolayer and few-layer samples of the compound nickel phosphorus trisulfide (NiPS3) by mechanical exfoliation. This material belongs to the class of transition metal phosphorus trisulfides (MPS3), several of which exhibit antiferromagnetic order at low temperature, and which have not been reported in the form of ultrathin sheets so far. We establish layer numbers by optical bright field microscopy and atomic force microscopy, and perform a detailed Raman spectroscopic characterization of bilayer and thicker NiPS3 flakes. Raman spectral features are strong functions of excitation wavelength and sample thickness, highlighting the important role of interlayer coupling. Furthermore, our observations provide a spectral fingerprint for distinct layer numbers, allowing us to establish a sensitive and convenient means for layer number determination.

    View details for DOI 10.1038/srep20904

    View details for Web of Science ID 000370054900001

    View details for PubMedID 26875451

    View details for PubMedCentralID PMC4753463

  • Insulating-layer formation of metallic LaNiO3 on Nb-doped SrTiO3 substrate APPLIED PHYSICS LETTERS Yoo, H., Chang, Y., Moreschini, L., Kim, H., Sohn, C., Sinn, S., Oh, J., Kuo, C., Bostwick, A., Rotenberg, E., Noh, T. 2015; 106 (12)

    View details for DOI 10.1063/1.4916225

    View details for Web of Science ID 000351876700013

  • Experimental Determination of Electron Affinities for InN and GaN Polar Surfaces APPLIED PHYSICS EXPRESS Lin, S., Kuo, C., Liu, X., Liang, L., Cheng, C., Lin, C., Tang, S., Chang, L., Chen, C., Gwo, S. 2012; 5 (3)
  • Plasmonic Green Nanolaser Based on a Metal-Oxide-Semiconductor Structure NANO LETTERS Wu, C., Kuo, C., Wang, C., He, C., Lin, M., Ahn, H., Gwo, S. 2011; 11 (10): 4256–60


    Realization of smaller and faster coherent light sources is critically important for the emerging applications in nanophotonics and information technology. Semiconductor lasers are arguably the most suitable candidate for such purposes. However, the minimum size of conventional semiconductor lasers utilizing dielectric optical cavities for sustaining laser oscillation is ultimately governed by the diffraction limit (∼(λ/2n)(3) for three-dimensional (3D) cavities, where λ is the free-space wavelength and n is the refractive index). Here, we demonstrate the 3D subdiffraction-limited laser operation in the green spectral region based on a metal-oxide-semiconductor (MOS) structure, comprising a bundle of green-emitting InGaN/GaN nanorods strongly coupled to a gold plate through a SiO(2) dielectric nanogap layer. In this plasmonic nanocavity structure, the analogue of MOS-type "nanocapacitor" in nanoelectronics leads to the confinement of the plasmonic field into a 3D mode volume of 8.0 × 10(-4) μm(3) (∼0.14(λ/2n)(3)).

    View details for DOI 10.1021/nl2022477

    View details for Web of Science ID 000295667000039

    View details for PubMedID 21882819

  • Natural band alignments of InN/GaN/AlN nanorod heterojunctions APPLIED PHYSICS LETTERS Kuo, C., Chang, K., Shiu, H., Liu, C., Chang, L., Chen, C., Gwo, S. 2011; 99 (12)

    View details for DOI 10.1063/1.3641422

    View details for Web of Science ID 000295853500030

  • Spontaneous-polarization-induced heterojunction asymmetry in III-nitride semiconductors APPLIED PHYSICS LETTERS Kuo, C., Chang, K., Shiu, H., Lin, S., Chen, C., Gwo, S. 2011; 99 (2)

    View details for DOI 10.1063/1.3610976

    View details for Web of Science ID 000292777300035

  • Is electron accumulation universal at InN polar surfaces? APPLIED PHYSICS LETTERS Kuo, C., Lin, S., Chang, K., Shiu, H., Chang, L., Chen, C., Tang, S., Gwo, S. 2011; 98 (5)

    View details for DOI 10.1063/1.3549874

    View details for Web of Science ID 000286988400029

  • Effects of (NH4)(2)S-x treatment on indium nitride surfaces JOURNAL OF APPLIED PHYSICS Chang, Y., Lu, Y., Hong, Y., Kuo, C., Gwo, S., Yeh, J. 2010; 107 (4)

    View details for DOI 10.1063/1.3318685

    View details for Web of Science ID 000275028900055

  • Valence band offset and interface stoichiometry at epitaxial Si3N4/Si(111) heterojunctions formed by plasma nitridation APPLIED PHYSICS LETTERS Lee, H., Kuo, C., Shiu, H., Chen, C., Gwo, S. 2009; 95 (22)

    View details for DOI 10.1063/1.3269601

    View details for Web of Science ID 000272627600028

  • Direct imaging of GaN p-n junction by cross-sectional scanning photoelectron microscopy and spectroscopy APPLIED PHYSICS LETTERS Kuo, C., Lee, H., Shiu, H., Chen, C., Gwo, S. 2009; 94 (12)

    View details for DOI 10.1063/1.3109778

    View details for Web of Science ID 000264633500027

  • Electronic Properties of III-Nitride Surfaces and Interfaces Studied by Scanning Photoelectron Microscopy and Spectroscopy Symposium on III-Nitride Materials for Sensing, Energy Conversion and Controlled Light-Matter Interactions, at the 2009 MRS Fall Meeting Kuo, C., Lee, H., Wu, C., Shiu, H., Chen, C., Gwo, S. MATERIALS RESEARCH SOC . 2009: 1202–I04-03

    View details for DOI 10.1557/PROC-1202-I04-03

  • Immobilization of DNA-Au nanoparticles on aminosilane-functionalized aluminum nitride epitaxial films for surface acoustic wave sensing APPLIED PHYSICS LETTERS Chiu, C., Lee, H., Kuo, C., Gwo, S. 2008; 93 (16)

    View details for DOI 10.1063/1.3003875

    View details for Web of Science ID 000260383700052

  • Absence of Fermi-level pinning at cleaved nonpolar InN surfaces PHYSICAL REVIEW LETTERS Wu, C., Lee, H., Kuo, C., Chen, C., Gwo, S. 2008; 101 (10): 106803


    Prior experimental work had found that the Fermi level at InN growth surfaces is pinned well above the conduction band edge, leading to strong surface band bending and electron accumulation. Using cross-sectional scanning photoelectron microscopy and spectroscopy, we show definitive evidence of unpinned Fermi level for in situ cleaved a-plane InN surfaces. To confirm the presence or absence of band bending, the surface Fermi level relative to the valence band edge was precisely measured by using both the Fermi edge of Au reference sample and the core level of ultrathin Au overlayer. It is confirmed that flat surface bands only occur at cleaved nonpolar surfaces, consistent with the recent theoretical predictions.

    View details for DOI 10.1103/PhysRevLett.101.106803

    View details for Web of Science ID 000258975100048

    View details for PubMedID 18851242

  • Cross-sectional scanning photoelectron microscopy and spectroscopy of wurtzite InN/GaN heterojunction: Measurement of "intrinsic" band lineup APPLIED PHYSICS LETTERS Wu, C., Lee, H., Kuo, C., Chen, C., Gwo, S. 2008; 92 (16)

    View details for DOI 10.1063/1.2913204

    View details for Web of Science ID 000255456100031

  • Polarization-induced valence-band alignments at cation- and anion-polar InN/GaN heterojunctions APPLIED PHYSICS LETTERS Wu, C., Lee, H., Kuo, C., Gwo, S., Hsu, C. 2007; 91 (4)

    View details for DOI 10.1063/1.2764448

    View details for Web of Science ID 000248345500052