Resonant photoemission study of Sm atoms on ZnO surface

Anna Reszka 1Bronislaw A. Orlowski 1Łukasz Wachnicki 1Sylwia Gierałtowska 1Elżbieta Guziewicz 1Bogdan J. Kowalski 1Marek Godlewski 1,2Robert L. Johnson 3

1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
2. Cardinal Stefan Wyszynski University, College of Science, Warszawa, Poland
3. University of Hamburg, Institute for Experimental Physics, Luruper Chausse 149, Hamburg D-22761, Germany

Abstract
Apart from optoelectronic applications due to its intense ultraviolet near-band-edge luminescence, zinc oxide is also considered as a host material for doping with optically active impurities (such as rare-earth ions [1-2]) in view of expanding the luminescence range into the visible light spectrum. In the present work we investigate properties of ZnO doped with Sm. Samarium is a very interesting dopant for photoemission studies because its divalent and trivalent configurations are characterized by distinct and well separated photoemission features. The multiplet corresponding to the initial 4f6 configuration is identified within 5 eV of the Fermi level while the multiplet associated with the initial 4f5 configuration appears between 5 eV and 10 eV below the valence band edge. Moreover, Sm2+ and Sm3+ ions produce quite different luminescence spectra [3].

The ZnO samples were grown by atomic layer deposition (ALD) in the Institute of Physics Polish Academy of Sciences in Warsaw. The main advantage of this method is a self limitation and sequential growth process, which enables using very reactive precursors and reducing growth temperature, while keeping good crystallographic and optical parameters. The polycrystalline and epitaxial ZnO films were deposited at 300ºC on a Si and a GaN/Al2O3 template, respectively.

Deposition of Sm atoms onto the ZnO surface and photoemission measurements were performed at the FLIPPER II beamline in HASYLAB synchrotron radiation laboratory (Hamburg, Germany).  Samarium was deposited from a Knudsen cell under ultra-high vacuum conditions at room temperature. Sm atoms were evaporated sequentially to obtain capping layers with the thickness of 1 ML, 3 ML and 7 ML. After the last deposition the samples were annealed for 0.5 and 4 hours at 300ºC. The set of energy distribution curves (EDC) was acquired after each step of the deposition and annealing processes. The investigations of Sm/ZnO system by resonant photoemission spectroscopy were carried out for the photon energy range of 130-160 eV that corresponds to the Sm4d→Sm4f Fano resonance region [4]. For the 4f6 (Sm2+) and the 4f5 (Sm3+) configurations, two resonant photoemission processes occur:

Sm4d104f6 + hν → [Sm4d94f7]* → Sm4d104f5 + e        (1)

and

Sm4d104f5 + hν → [Sm4d94f6]* → Sm4d104f4 + e        (2)

 

where []* denotes an excited state. Each of the processes described above is accompanied by the classical photoemission process as follows:

Sm4d104f6 + hν → Sm4d104f5 + e                                  (3)

and

Sm4d104f5 + hν → Sm4d104f4 + e                                  (4)

 

As a result of the interference between resonant and classical photoemission channels, we observe two separated resonances for divalent (channels (1) and (3)) and trivalent (channels (2) and (4)) samarium states [5]. The photoemission resonance for Sm3+ configuration is observed at photon energy 141 eV, whereas the resonance for Sm2+ configuration occurs at photon energy 136 eV [4]. Photoemission Energy Distribution Curves (EDCs) taken after each step of deposition and annealing at photon energy of both Fano resonances are shown in Fig. 1 and 2.

Fig. 1. Photoemission spectra EDCs for Sm/ZnO measured at hν = 136 eV to emphasize the 4f6 (Sm2+) emission. The spectra show the valence band and the nearest core levels.

After each step of deposition we observed photoemission enhancement at the valence band edge, i.e. in the energy region characteristic of Sm2+ configuration. We also see a small increase of photoemission intensity in the energy region between 5 eV and 10 eV below the valence band edge, i.e. characteristic of Sm3+ configuration. After 30 min. annealing at 300ºC the peak at the valence band edge (characteristic of Sm2+) disappears and the feature of Sm3+ markedly increases, which is the fingerprint that samarium atoms become trivalent. We also observe that the maximum of the Zn3d core level shifts to lower binding energy after samarium deposition, but returns to the previous position characteristic of ZnO crystal after 30 min. annealing. This indicates that chemical reaction between ZnO and Sm takes place at the interface region.

Fig. 2. Photoemission spectra EDCs for Sm/ZnO measured at hν = 141 eV to emphasize the 4f5 (Sm3+) emission. The spectra show the valence band and the nearest core levels.

Acknowledgements: The authors acknowledge support by MSHE of Poland research Projects DESY/68/2007 and by the European Community via the Research Infrastructure Action under the FP6 Structuring the European Research Area" Programme (through the Integrated Infrastructure Initiative "Integrating Activity on Synchrotron and Free Electron Laser Science") at DESY. Partially supported by Innovative Economy  (POIG.01.01.02-00-008/08).

References

[1] W. M. Jadwisienczak et al., J. Electron. Mater. 31, 776 (2002)

[2] L. Armelao et al., J. Phys. Chem. C  111, 10194 (2007)

[3] C.T.M. Ribeiro, F. Alvarez, A.R. Zanatta, Adv. Mat. 14, 1154 (2002)

[4] E. Guziewicz et al., Surf. Sci. 551, 132 (2004)

[5] F. Gerken, et al., in: B. Craseman (Ed.), Proceedings of the International Conference on X-ray and Atomic Inner-Shell Physics, AIP Conference Proceedings no. 94, AIP, New York, 1982, p. 602.

 

Related papers
  1. Nanoparticles for medical imaging 
  2. The effect of annealing on properties of Europium doped ZnO nanopowders obtained by a microwave hydrothermal method
  3. Microwave conductivity of ZnO:Co and ZnO:Cu thin films with nano-size metallic Co/Cu inclusions.
  4. Tb3+ ion luminescence enhancement in yttria host lattice obtained via microwave hydrothermal process
  5. Quantum semiconductor nanostructures for applications in biology and medicine -development and commercialisation of new generation devices for molecular diagnostics on the basis of new Polish semiconductor devices
  6. Growth and properties of inclined GaN nanowires on Si(001) substrates by PAMBE
  7. Impact of substrate microstructure on self-induced nucleation and properties of GaN nanowires grown by plasma-assisted MBE
  8. Optical Characterisation of Bulk ZnO Crystals Grown by CVT
  9. Physical properties of unique ZnO single crystals from Oława Foundry
  10. MBE growth of GaN nanowires on Si(111) substrates for gas sensor applications 
  11. Electronic and optical properties – As and As+Sb doped ZnO grown by PA-MBE
  12. Hydrothermal growth of ZnO nanorods for solar cells applications
  13. Epitaxial growth and characterization of zinc oxide nanorods obtained by the hydro-thermal method
  14. Growth of zinc oxide and dielectric films using Atomic Layer Deposition method from organic precursors
  15. Grown ZnMgO/ZnO/ZnMgO heterostructures on p-type Si(111) by MBE method
  16. Dual-acceptor doped p-ZnO:(As+Sb)/n-GaN heterojunctions grown by PA-MBE as a highly selective UV detector
  17. Structural, morphological and optical properties of ZnAl2O4 nanoparticles co-doped with Er3+and Yb3+ prepared by combustion aerosol synthesis.
  18. Stany Mn 3d w paśmie walencyjnym Ga1-xMnxSb
  19. Rezonansowe badania fotoemisyjne ferromagnetycznych warstw ZnCoO
  20. X-ray photoemission from CdTe/PbTe/CdTe nanostructure in normal and grazing-incidence modes
  21. Mangan w warstwach ZnMnO hodowanych metodą osadzania warstw atomowych
  22. ZnO and core/shell ZnO/ZnS nanofibers: Characterization and applications
  23. Lokalne otoczenie atomów kobaltu w cienkich warstwach ZnCoO
  24. Contactless electroreflectance of ZnSe layers grown by atomic layer epitaxy
  25. Electrical and optical properties of zinc oxide layers obtained by Atomic Layer Deposition
  26. Zinc oxide grown by Atomic Layer Deposition - a material for novel 3D electronics
  27. Dimethylzinc and diethylzinc as precursors for monocrystalline zinc oxide grown by Atomic Layer Deposition
  28. Thin films of ZnS and ZnSe by Atomic Layer Deposition for light sensor applications
  29. Photovoltaic cells based on nickel phthalocyanine and zinc oxide formed by atomic layer deposition
  30. Effects related to deposition temperature of ZnCoO films grown by Atomic Layer Deposition – uniformity of Co distribution, structural, electric and magnetic properties
  31. Diffusion profiles of transition metals (TM= Co or Mn) in ZnO and GaN incorporated by annealing of thin TM film
  32. Fluorination of Carbon Nanotubes in CF4 Plasma
  33. Effect of annealing on the structure and microstructure of Pr doped ZrO2-Y2O3 nanocrystals
  34. Synthesis of doped ZnO nanopowders in microwave hydrothermal reactors
  35. Synthesis of Al doped ZnO nanopowders and their enhanced luminescence
  36. How we can stimulate intra-shell emissions of rare earth and transition metal ions in thin films and in nanoparticles
  37. ZnO thin films for organic/inorganic heterojunctions
  38. Combining microwave and pressure techniques for hydrothermal synthesis of ZnO and ZrO2 nanopowders doped with a range of metal ions
  39. Luminescence properties of zinc oxide nanopowders doped with Al ions obtained by the hydrothermal and vapour condensation methods.
  40. Gd atoms on Si (111) surface – AFM and photoemission study
  41. Mn 3d electrons in the valence band of Mn/Ge0.9Mn0.1Te- a resonant photoemission study
  42. Wide band-gap II-VI semiconductors for optoelectronic applications
  43. Water absorption by epitaxial LaNiO3-x thin films
  44. Low temperature ZnMnO by ALD
  45. Electronic Structure of Pd Nanoparticles on Carbon Nanotubes
  46. Functionalization of MWCNTs Using Atomic Nitrogen: Effects on Electronic Structure
  47. ZnMnO Films grown by Atomic Layer Deposition with uniform Mn distribution
  48. Effect of annealing on electrical properties of low temperature ZnO films
  49. Doping of ZnO nanopowders with Mn, Ni and Cr In an ultrasound and microwave driver hydrothermal reaction
  50. Time-resolved ODMR investigations of II-VI based DMS heterostructures
  51. Method of Manganese co-doping of LT ZnO films
  52. Photoluminescence of ZnO films studied by femptosecond sapphire:Ti laser
  53. Two color spectroscopy of ZnSe:Cr
  54. Photo-EPR studies of charge tunneling processes in CdxZn(1-x)Se:Fe,Cr (0 ≤ x ≤ 0.3) crystals
  55. Luminescence of CdMnTe Crystals in Magnetic Field
  56. Luminescence of doped nanoparticles of wide band gap II-VI compounds
  57. Doping of ZnO nanopowders with Mn and Cr in an ultrasound and microwave driven hydrothermal reaction
  58. Investigation of epitaxial LaNiO3-x thin films by High-Energy XPS
  59. GaN(0001) surface Fe atoms doped
  60. Growth and characterization of thin films of ZnO by Atomic Layer Epitaxy
  61. Dynamics of spin interactions in II-Mn-VI semiconductors studied with time-resolved optically detected magnetic resonance
  62. Influence of n-type doping on light emission properties of GaN layers and GaN-based quantum well structures
  63. Fe photoionization transition in ZnSSe:Fe crystals - photo-ESR studies
  64. Interaction of Mn and Ti atoms with GaN surface - a resonant photoemission study
  65. VUV photoemission using synchrotron light: a tool for characterising surfaces and interfaces occurring in OLEDs
  66. In-depth and in-plane profiling of InGaN-based laser diodes and heterostructures
  67. Cathodoluminescence study of n-type doped GaN epilayers and GaN/InGaN quantum well structures
  68. Compensation mechanisms in magnesium doped GaN
  69. Optical and magnetic resonance investigations of ZnO crystals doped with transition metal ions
  70. Optical and ODMR study of GaN-based HEMT structures
  71. Photo-ESR and optical studies of Cr photoionization transition in CdZnSe:Cr crystals
  72. Gallium nitride surface formation and modification by Mn deposition - photoemission studies with use of synchrotron radiation
  73. Luminescent properties of wide bandgap materials at room temperature
  74. Mn doped ZnTe (110) (1x1) surface in Resonant Photoemission study
  75. Differential Reflectivity and Photoemission study of ZnTe and CdTe(110) surface

Presentation: Poster at IX Krajowe Sympozjum Użytkowników Promieniowania Synchrotronowego, by Anna Reszka
See On-line Journal of IX Krajowe Sympozjum Użytkowników Promieniowania Synchrotronowego

Submitted: 2011-06-16 15:25
Revised:   2011-09-16 18:35