Quantum size effects on surfaces without a projected bandgap: Pb/Ni(111)

Abstract

Abstract. We have studied the initial growth of Pb on Ni(111) using lowenergy electron microscopy (LEEM) and selective area low-energy electron diffraction (µLEED). First, a one-layer-high wetting layer develops that consists of small (7 × 7) and (4 × 4) domains. For larger coverages, Pb mesas are formed that are embedded in the wetting layer. In spite of the absence of a projected bandgap on clean Ni(111), we observe distinct quantum size effect (QSE)-driven preferred heights. These are apparent from a variety of frequently occurring island height transitions during growth, both on wide terraces and across substrate steps. Also, the average island heights that evolve during deposition at 422 and 474 K show a clear signature of QSE-driven preferred heights. These distinctly include five, seven and nine layers and thus correspond nicely to the values obtained in the key examples of QSE: Pb films on Si(111) and Ge(111). We suggest that the Pb-induced surface modification of Ni(111) shifts the Fermi level into the gap of the interface projected Ni bulk bands, thereby effectively causing decoupling of the Pb states with the bulk Ni states.

Electronically stabilized nanowire growth

“…The main access road to these Friedel oscillations in a film is through calculations. Experimentally, direct access is impossible, but QSE have been observed in electron reflectivity for electrons above the vacuum level, both in integral measurements [34][35][36] and in position-resolved experiments [37][38][39][40][41] . However, because of their unique geometry, the Ir wires would offer a unique and viable opportunity to access the relationship between size selection and Friedel oscillations in a most direct manner.…”

Quantum size stabilization of Ge3Pt nanofilms on Ge(001)

“…Therefore, we select the n = 7 peak as the Bragg peak. From the number of peaks, one then immediately obtains the number of layers and, thus, the thickness of the film [16,[21][22][23][24][25]. We stress that the (I, √ E ) curve contains also information on the electronic structure of unoccupied bands.…”

Growth morphology of Pb films on Ni3Al(111)

“…3(e growth with dislocations for Pb adsorption on Mo(110) has been observed [19]. The presence of compressed wetting layers with density higher than the metallic Pb(111) density by approximately 5% has been identified as the key factor that provides unusually fast and nonclassical kinetics in the uniform height island [11,14]. It is not unusual to expect that the p(44) phase plays the same role and superfast diffusion can be present in this system as well.…”

“…Recently a novel growth mode has been observed in epitaxial growth of Pb on Si(111) [1][2][3][4][5][6][7][8][9][10][11][12][13], Ni(111) [14][15][16], Cu(111) [13,[17][18] and Mo(110) [19][20] surfaces. Pb islands grow to specific heights 'magic heights,' which are stable due to quantum size effects (QSE) [21][22][23][24] associated with electron confinement in the vertical direction within the islands.…”