Low-temperature scanning tunneling microscopy study on the electronic properties of a double-decker DyPc₂molecule at the surface

Abstract

To fully achieve potential applications of the double-decker molecules containing rare earth elements as single-molecule magnets in molecular spintronics, it is crucial to understand the 4f states of the rare earth atoms sandwiched in the double-decker molecules by metal electrodes. In this study, low-temperature scanning tunneling microscopy and spectroscopy were employed to investigate the isolated double-decker DyPc2 molecule adsorbed on Au(111) via its differential conductance measurements. The experimental results revealed that the differential conductance maps acquired at a constant height mode simply depicted the authentic molecular orbitals; moreover, the differential conductance maps achieved at a constant current mode could not directly probe the 4f states of the sandwiched Dy atom. This was consistent with the spectra obtained over the molecule center around the Fermi level, indicative of no Kondo feature. Upon decreasing the tip-molecule distance, the CH-mode images presented high-resolution structure but no information of the 4f states. All results indicated that the Dy atom barely contributed to the tunneling current because of the absence of coupling with the microscope tip, echoing the inaccessibility of the Dy 4f states in the double-decker DyPc2 molecule.

Imaging isodensity contours of molecular states with STM

“…However, these so-called constant-current dI/dV maps suffer from the fact that the tip-sample distance (z) varies during the scan and therefore do not properly reflect the local DOS of the probed nanostructure. This well-known limitation has been evidenced for surface-confined electronic states [19,20], adatoms [21] or molecules adsorbed on surface [22][23][24]. To extract reliable information from these maps, a time-consuming image treatment is required after acquisition [20][21][22][23][24].…”

On-surface structural and electronic properties of spontaneously formed Tb2Pc3 single molecule magnets

“…6,19,24,26,30,35 The location and strength of the Kondo resonance has been attributed to charge transfer between the substrate and the TbPc 2 molecules. [5][6][7]11,[13][14][15][17][18][19][20]22,[24][25][26][28][29][30]35,36 The Kondo phenomenon is observed in all studies conducted on the monolayer TbPc 2 on Au(111) 19,27 but not on the Ag (111) substrate. 24 Nevertheless, in the case of the higher apparent height (i.e.…”

A tetrairon(III) single-molecule magnet and its solvatomorphs: synthesis, crystal structures and vapor-phase processing

“…The real application potential [8] of most SMMs, however, is severely limited by their instability under the processing methods customarily used in spintronics, above all thermal sublimation in high vacuum (HV). Some mononuclear SMMs withstand sublimation, like those of the LnPc2 [9][10][11][12][13][14] and Ln(trensal) [15][16][17] families, as well as a few other lanthanoid (Ln) complexes [18][19][20] (H2Pc = phthalocyanine, H3trensal = 2,2′,2′′-tris(salicylideneimino)triethylamine).…”