Cs deposition on layered 2H TaSe2 (0 0 0 1) surfaces: Adsorption or intercalation?

Pettenkofer, C.; Jaegermann, Wolfram; Schellenberger, Alfred; Holub-Krappe, E.; Papageorgopoulos, C.A.; Kamaratos, M.; Papageorgopoulos, Aris

doi:10.1016/0038-1098(92)90459-m

Cited by 52 publications

(30 citation statements)

References 27 publications

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“…6) with previous experiments [22]. Only with much larger amounts an intercalated component is visible at lower binding energy, as the arrows indicate.…”

Section: Cs/li/tase2supporting

confidence: 75%

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Alkali displacements in intercalated 1T-TaSe2

Tonti

Pettenkofer

Jaegermann

et al. 1998

Ionics

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Abstract. Single crystals of lT-TaSe2 have been intercalated with different alkali metals by deposition in ultra-high vacuum onto in situ-cleaved (0001) surfaces. In a second step a different alkali metal, or C12, has been deposited on top. The interactions among the deposited species and the substrate have been investigated using soft x-ray photoelectron spectroscopy (SXPS). Li and Na appear to compete in the intercalation process. Li replaces Na, by pushing it deeper into the crystal. Cs on Li:TaSe2 does not intercalate, but stays on top, repelling intercalated Li + deeper inside. For Li on Cs:TaSe2 an exchange reaction takes place, and Cs is deintercalated. The same effect is induced by Na deposited on intercalated Cs. 1T--->2H phase transition for TaSe2 has been observed only for Li depos!tion. C12 deposition on Na intercalated substrate induced deintercalation of Na. The experimental results are discussed in relation to thermodynamic, electronic and electrostatic effects.

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“…6) with previous experiments [22]. Only with much larger amounts an intercalated component is visible at lower binding energy, as the arrows indicate.…”

Section: Cs/li/tase2supporting

confidence: 75%

“…A dramatic change of the electronic structure is evident at the last Li deposition step. The new structure is known to correspond to that of 2H-TaSe2 [22]. No further drastic change occurs with Na deposition.…”

Section: Resultsmentioning

confidence: 76%

Alkali displacements in intercalated 1T-TaSe2

Tonti

Pettenkofer

Jaegermann

et al. 1998

Ionics

Self Cite

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“…A new method suited for preparing samples for the studies of surface science was also reported, the intercalated compounds were prepared by in situ evaporation of metal atoms to the (0 0 0 1) cleaved surface of the TMDC's crystals. This process should be realized under the condition of ultra high vacuum (UHV) 14,21 . In this paper, we report the growth of crystals of N a x T aS 2 directly with chemical reaction.…”

Section: Methodsmentioning

confidence: 99%

Fabrication and superconductivity ofNaxTaS2crystals

et al. 2005

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In this paper we report the growth and superconductivity of N axT aS2 crystals. The structural data deduced from X-ray diffraction pattern shows that the sample has the same structure as 2H − T aS2. A series of crystals with different superconducting transition temperatures (Tc) ranging from 2.5 K to 4.4 K were obtained. It is found that the Tc rises with the increase of N a content determined by Energy-Dispersive x-ray microanalysis(EDX) of Scanning Electron Microscope (SEM) on these crystals. Compared with the resistivity curve of un-intercalated sample 2H − T aS2 (Tc = 0.8 K, TCDW ≈ 70 K), no signal of charge density wave (CDW) was observed in samples N a0.1T aS2 and N a0.05T aS2. However, in some samples with lower Tc, the CDW appears again at about 65 K. Comparison between the anisotropic resistivity indicates that the anisotropy becomes smaller in samples with more N a intercalation (albeit a weak semiconducting behavior along c-axis) and thus higher Tc. It is thus concluded that there is a competition between the superconductivity and the CDW. With the increase of sodium content, the rise of Tc in N axT aS2 is caused mainly by the suppression to the CDW in 2H − T aS2, and the conventional rigid band model for layered dichalcogenide may be inadequate to explain the changes induced by the slight intercalation of sodium in 2H − T aS2.

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“…One way of doing this, is to measure spectra frequenly during the deposition to obtain a record of the development of different alkali metal species as a function of the deposited amount. During room temperature Cs deposition on Pettenkofer et al [34] first observed increasing Cs 5p emission features typical of surface adsorbed Cs. Later during the deposition, features characteristic of intercalated Cs appeared and grew stronger while the surface related features gradually vanished.…”

Section: Crystallographic Structurementioning

confidence: 99%

“…In particular, the intercalated crystals tend to become severely cracked, so that attempts to obtain clean surfaces by cleavage are likely to expose only contaminated fissure surfaces. In many cases this problem can be avoided by first preparing a high-quality surface of the pure TMDC (usually by cleavage in UHV), and then to deposit the metal on this surface (still in UHV), from which it may intercalate spontaneously without major damage to the surface [8,33,34]. Since the deposition typically is done in the measurement chamber (or a connected preparation chamber) immediately before performing the desired experimental study, this technique is often referred to as in situ intercalation.…”

Section: Intercalation Of Tmdcsmentioning

confidence: 99%