Growth and electronic structure of alkali-metal adlayers on icosahedralAl70.5Pd21Mn8.5

Abstract

We report x-ray photoelectron spectroscopy ͑XPS͒ study of Na and K adlayers on icosahedral Al 70.5 Pd 21 Mn 8.5 ͑i-Al-Pd-Mn͒ quasicrystal. The Na 1s core-level exhibits a continuous linear shift of 0.8 eV towards lower binding energies ͑BE͒ with increasing coverage up to one monolayer ͑ML͒ saturation coverage. In the case of K / i-Al-Pd-Mn, a similar linear shift in the K 2p spectra towards lower BE is observed. In both cases, the plasmon related loss features are observed only above 1 ML. The substrate core-level peaks, such as Al 2p, do not exhibit any shift with the adlayer deposition up to the highest coverage. Based on these experimental observations and previous studies of alkali metal growth on metals, we conclude that below 1 ML, both Na and K form a dispersed phase on i-Al-Pd-Mn and there is hardly any charge transfer to the substrate. The variation of the adlayer and substrate core-level intensities with coverage indicates layer by layer growth.

Quasiperiodic ordering in thick Sn layer on i -Al-Pd-Mn: A possible quasicrystalline clathrate

“…The absence of core level shift or change in the shape also excludes the possibility of any alloying or intermixing of Sn with the substrate. This observation also implies a propensity for condensed island growth [18] as also shown in Fig. 2(a), indicating the dominance of adsorbate-adsorbate interaction.…”

“…An elemental quasicrystal would be best suited for this purpose, but a single-element bulk quasicrystal has not been yet observed. Efforts in this direction for over a decade have involved the use of quasicrystalline substrates as a template to grow quasiperiodic elemental layers [14][15][16][17][18][19][20][21][22][23][24][25][26]. Pseudomorphic growth of one monolayer (ML) quasiperiodic Sn has been reported in the past on decagonal (d)-Al-Ni-Co [15] and icosahedral (i)-Al-Cu-Fe [16].…”

Quasiperiodic layers of free-electron metals studied using electron diffraction

“…The thickness of the adlayers has been calculated from the area under the ͑Na 1s and K 2p͒ and ͑Al 2p͒ core-level peaks, as in our previous work. 12,19 The atomic density of a completed monolayer is 0.067 atoms/ Å 2 , corresponding to a coverage of ⌰ = 0.50, i.e., roughly equal to the coverage of the ͑4 ϫ 4͒ phase of Na on Al͑111͒.…”

Inverse photoemission spectroscopic studies on phase separated La 0.2 Sr 0.8 MnO 3

“…The specimen was scrapped in vacuum using a diamond file in order to get rid of the surface contamination. An electron gun of Stoffel Jhnson [10,11] design and an acetone filled band pass detector with CaF 2 window is used for the experiments [12,13]. The experiments were carried out in the isochromat mode where the energy of the incident electron was varied in steps of 0.1 eV and photons of fixed energy (9.9 eV) were detected with an overall instrumental resolution of 0.55 eV.…”