Deciphering the Growth Mechanism of Self-Assembled Nanowires on Pt-Deposited Ge(001) via Scanning Tunneling Microscopy and Density Functional Theory Calculations

Abstract

Shrinking the size of electronic components has been highly desirable in the semiconductor industry in recent years, and the next breakthrough in reducing the size of electronic devices may be via the bottom-up approach. Previous research showed that the deposition of metal atoms onto semiconductor surfaces could result in the self-assembly of atomically thin nanowires (NWs) extending for hundreds of nanometers. However, current understanding of the self-assembly mechanism of the NWs on semiconductor surfaces is still limited and unclear.Here, through a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) calculation, the atomistic details of NWs growth on Pt-modified Ge(001) surfaces are uncovered. Directly observing the coexistence of various intermediate phases after Pt deposition enables us to explore the correlation among these phases, which provides important insights in deciphering the self-assembly mechanism of the NWs on semiconductor surfaces. Deposited Pt atoms are capable of chemically interacting with surface atoms on Ge(001) surface layer at elevated temperature (∼873 K) leading to the formation of various phases (e.g., α-terraces, β-terraces, and NWs). Among them, three-row-wide trench−plateau structures are clearly identified in this work, and an energetically favorable structure for this phase is unveiled using DFT calculations. It is found that this intermediate phase plays a critical role in the process of NWs growth, and the trenches on the edges are believed to be the cradle for NWs growth. The atomistic understanding of the self-assembly of nanostructure on Ge(001) surfaces could further help us design more complex nanostructures on semiconducting platforms, which is crucial for further reduction in the size of electronic devices.

Uncovering the Self-Organized Nanowires on Au-Modified Ge(001) Surfaces

“…Early studies revealed that the deposition of Pt or Au atoms on pristine Ge(001) substrates could trigger the self-assembly of well-ordered nanowires (NWs) extending for hundreds of nanometers. − Substantial efforts have been devoted to investigate the NWs on Pt-modified Ge(001). Their atomic structures and growth mechanism had been established. − However, the atomic configurations of NWs on the Au-modified Ge(001) surfaces remain elusive, and their electronic behaviors have long been controversial.…”

Electric Field-Induced Phase Transition of Nanowires on Germanium(001) Surfaces

“…Earlier studies reported the self-assembly of atomic NWs on semiconductor surfaces after annealing at an elevated temperature. , Among those nanostructures on Si or Ge platforms, Au-NWs on Ge(001) surfaces have attracted significant attention due to their elusive atomic configurations and ambiguous electronic behaviors. − Much effort has been devoted to deciphering their atomic configurations, and many structural models were then proposed. ,− Previously, we reported different types of NWs on Au/Ge(001) surfaces based on scanning tunneling microscopy (STM) observations and identified two structural models, i.e., Au-NWs-in-trenches (ANT) and Au–Ge-modified-dimer-row (AGMDR), with the DFT calculation evaluation …”