Quantum Confinement between Self-Organized Pt Nanowires on Ge(001)

Abstract

The existence of one-dimensional (1D) electronic states between self-organized Pt nanowires spaced 1.6 or 2.4 nm apart on a Ge(001) surface is revealed by low-temperature scanning tunneling microscopy. These perfectly straight Pt nanowires act as barriers for a surface state (located just below the Fermi level) of the underlying terrace. The energy positions of the 1D electronic states are in good agreement with the energy levels of a quantum particle in a well. Spatial maps of the differential conductivity of the 1D electronic states conclusively reveal that these states are exclusively present in the troughs between the Pt nanowires.

Electronically stabilized nanowire growth

“…At 0.3-0.35 eV below the Fermi level, a pronounced electronic state is observed in the density of states of the nanowires. Despite the fact that this electronic state is located on the nanowires, thermal and instrumental broadening are too large to resolve the exact dimensionality from the energy dependence of the density of states 17 .…”

“…Fortunately, the heavy 5d-transition metals such as Pt and Au have a strong tendency to self-assemble into defect-free, straight, long and narrow nanowires on annealing, subsequent to deposition on semiconductor group IV (001) surfaces [16][17][18][19][20][21][22][23] . The Pt-and Au-induced nanowires, although different in nature, that is, in their structure [16][17][18][19][20][21][22] , share the property of being able to attain lengths of up to a few microns. Guided by the similarities in quantum transport between Ir on the one hand and Au and Pt on the other hand, we have investigated the self-organized growth of Ir on Ge(001) using scanning tunneling microscopy (STM) and spectroscopy in an attempt to expand the playground for 1D physics.…”

Modeling 1D structures on semiconductor surfaces: synergy of theory and experiment

“…In most experimental work, this is stated as 0.25 ML, 18,86,88,91 although some authors report larger deposition amounts of 0.5 or even 1.2 ML. 21 Investigation of STM images presented shows the surface is only partially covered with Pt NWs.…”

“…112 Let us now return to the case at hand: nanowires on Ge. The formation of nanowires, chains, and rods has been observed on Ge surfaces after deposition of Pt, 18,19,21,[86][87][88][89][90][91][92][93][94] Au, [95][96][97][98][99][100][101][102][103][104] In, 79,82,83,199 Er, 77 Ho, 78 Co, 108 Ir, 109 Yb, 200 Sr, 198,201 and Ba. 198 Many of these systems show a large variety of surface reconstructions at different submonolayer depositions and temperatures (cf., the surface phase-diagram for In on Ge(001) given in Ref.…”

“…More recently Pt and Au NWs on Ge(001) attracted attention. 85 After deposition of (sub)monolayer amounts of Pt 18,19,21,[86][87][88][89][90][91][92][93][94] or Au [95][96][97][98][99][100][101][102][103][104] on Ge(001), large NW arrays were observed by several groups. These NWs have a width of the order of a single atom and their length is only limited by the underlying plateau, resulting in huge aspect ratios.…”