Quantum Size Effects Induced Novel Properties in Two-Dimensional Electronic Systems: Pb Thin Films on Si(111)

Abstract

Atomically flat metal ultrathin films grown on semiconductor substrates form a quasi-two-dimensional (2D) electronic system, which offers a great opportunity to explore novel properties induced by quantum size effects (QSE). In such a system, the motion of electrons in the film plane is essentially free, however, in the film normal direction it is confined, which leads to the quantized electronic states, i.e., quantum well states (QWS). The formation of QWS induces the redistribution of electrons and changes the electronic structure of the metal films and thus modifies their properties. By controlling the film thickness-the width of the confinement potential well, the QWS, together with the physical and chemical properties of the films can be engineered. In this article, we will summarize our recent studies on this problem in the Pb/Si(111) system, and discuss the perspectives in this area.

Atomically smooth ultrathin films of topological insulator Sb2Te3

“…QWSs are formed in ultrathin films because of the confinement of the movement of electrons. For atomically flat thin films grown on Si(111), QWSs have been found to give rise to many novel properties [39,40]. Clearly, the QWSs observed in our Sb 2 Te 3 films also originate from quantum confinement.…”

Spilling of electronic states in Pb quantum wells

“…Behavior of metallic quantum wells (QW) on semiconductor surfaces exhibiting quantum-size effects (QSE) has been a topic of great fundamental interest for many years [1][2][3]. The spatial confinement of electrons and the presence of discrete electronic subbands affect electronic properties of ultrathin films, as shown for the electrical resistivity [4][5][6], Hall coefficient [7,8], surface morphology [9][10][11][12][13][14][15], surface energy [16,17], work function [18,19], chemical reactivity [20], electron phonon coupling [21], superconducting transition temperature [22,23], Kondo temperature [24], Rashba spin-orbit interaction [25], and Friedel oscillations [26,27], to name a few.…”

Van Hove singularities as a result of quantum confinement: The origin of intriguing physical properties in Pb thin films

“…More interestingly, the anisotropy of the m-band of a Pb film is smaller than for the band of the bulk, the reason for which needs more detailed studies. We can explain very strong thickness-dependent physical properties observed in Pb thin films [5][6][7][8][9][10][11][12][13][14][15][16][17] in terms of the 1-D-like DOS singularity developing from the 2-D band bending: it is simply because the electronic structure near EF is now dominated by the singularity. Although we have only studied 23 and 24 ML Pb films, we know where the VHS of other Pb films is from previous STS measurements [16].…”

“…These have been explained by an oscillation in electronic density of states (DOS) near the Fermi level (E F ) [5][6][7][8][9][10][11][12][13][14][15][16][17], particularly in the bottom of subbands that pass though the Fermi level [18,19]. More interestingly, the oscillations in the properties of Pb persist for large film thicknesses, and quantized electronic states have even been observed at film thicknesses up to 45 ML [14], a much larger thickness [5][6][7][8][9][10][11][12][13][14][15][16][17] than observed for other films [2][3][4]. These strong oscillations in the properties of thick Pb films are very puzzling since, according to theory, the quantum size effect should quickly become damped with increasing thickness [18].…”