Limits...
Dynamic probe of ZnTe(110) surface by scanning tunneling microscopy

View Article: PubMed Central - PubMed

ABSTRACT

The reconstructed surface structure of the II–VI semiconductor ZnTe (110), which is a promising material in the research field of semiconductor spintronics, was studied by scanning tunneling microscopy/spectroscopy (STM/STS). First, the surface states formed by reconstruction by the charge transfer of dangling bond electrons from cationic Zn to anionic Te atoms, which are similar to those of IV and III–V semiconductors, were confirmed in real space. Secondly, oscillation in tunneling current between binary states, which is considered to reflect a conformational change in the topmost Zn–Te structure between the reconstructed and bulk-like ideal structures, was directly observed by STM. Third, using the technique of charge injection, a surface atomic structure was successfully fabricated, suggesting the possibility of atomic-scale manipulation of this widely applicable surface of ZnTe.

No MeSH data available.


(a) Schematic illustration of the ZnTe structure used for the DFT calculation. (b) Total energy difference between the ideal and reconstructed surface structures (Eide−Erec) as a function of the number of injected electrons. (c) Schematic diagrams showing atom manipulation by charge injection. Electrons injected from the STM tip induce the displacement of the topmost Zn atoms toward the vacuum side. (d) and (e) Calculated partial density of states (PDOS) for the topmost Zn and Te atoms and the Zn atom located in the third (110) layer of the reconstructed surface with no (d) and one (d) additional electron. (f) DOS calculated for the ideal surface structure with two additional electrons. (g) Calculated spatial distributions of the LDOS integrated over EF−0.2 eV < E < EF (EF: Fermi energy) for the ideal surface structure with two additional electrons.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC5036505&req=5

Figure 4: (a) Schematic illustration of the ZnTe structure used for the DFT calculation. (b) Total energy difference between the ideal and reconstructed surface structures (Eide−Erec) as a function of the number of injected electrons. (c) Schematic diagrams showing atom manipulation by charge injection. Electrons injected from the STM tip induce the displacement of the topmost Zn atoms toward the vacuum side. (d) and (e) Calculated partial density of states (PDOS) for the topmost Zn and Te atoms and the Zn atom located in the third (110) layer of the reconstructed surface with no (d) and one (d) additional electron. (f) DOS calculated for the ideal surface structure with two additional electrons. (g) Calculated spatial distributions of the LDOS integrated over EF−0.2 eV < E < EF (EF: Fermi energy) for the ideal surface structure with two additional electrons.

Mentions: In order to establish a possible interpretation for the surface dynamics induced by the electron injection of the STM sequence, we carried out a DFT calculation using the Perdew–Burke–Ernzerhof generalized gradient approximation with the ABINIT code and plane-wave-based norm-conserving pseudopotentials. A supercell including a slab model with five ZnTe(110) layers was used for the calculation. The dangling bonds of atoms in the bottom layer were passivated by hydrogen atoms, as shown in figure 4(a). The energy cutoff of the calculation was 60 Ry. As the sampling k-points, we used 8 × 8 × 2 grids within the first Brillouin zone. Here, we focused on a possibility of the atomic displacement of the topmost Zn atom, because the Zn atom is considered to be most easily desorbed from the surface, referring to the previous study [9], which reports that the defects on the cleaved ZnTe(110) surface mainly consist of the absences of Zn only or Zn–Te pairs and not Te only. As a possible computational model to describe the atomic displacement of the surface Zn atom toward the vacuum side from the reconstructed structure, we consider the ideal (110) surface structure consisting of a truncated bulk structure. The stability of the surface was analyzed by comparing the total energy difference between the ideal and reconstructed surface structures in the neutral state and in charged states with up to six additional electrons per supercell.


Dynamic probe of ZnTe(110) surface by scanning tunneling microscopy
(a) Schematic illustration of the ZnTe structure used for the DFT calculation. (b) Total energy difference between the ideal and reconstructed surface structures (Eide−Erec) as a function of the number of injected electrons. (c) Schematic diagrams showing atom manipulation by charge injection. Electrons injected from the STM tip induce the displacement of the topmost Zn atoms toward the vacuum side. (d) and (e) Calculated partial density of states (PDOS) for the topmost Zn and Te atoms and the Zn atom located in the third (110) layer of the reconstructed surface with no (d) and one (d) additional electron. (f) DOS calculated for the ideal surface structure with two additional electrons. (g) Calculated spatial distributions of the LDOS integrated over EF−0.2 eV < E < EF (EF: Fermi energy) for the ideal surface structure with two additional electrons.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036505&req=5

Figure 4: (a) Schematic illustration of the ZnTe structure used for the DFT calculation. (b) Total energy difference between the ideal and reconstructed surface structures (Eide−Erec) as a function of the number of injected electrons. (c) Schematic diagrams showing atom manipulation by charge injection. Electrons injected from the STM tip induce the displacement of the topmost Zn atoms toward the vacuum side. (d) and (e) Calculated partial density of states (PDOS) for the topmost Zn and Te atoms and the Zn atom located in the third (110) layer of the reconstructed surface with no (d) and one (d) additional electron. (f) DOS calculated for the ideal surface structure with two additional electrons. (g) Calculated spatial distributions of the LDOS integrated over EF−0.2 eV < E < EF (EF: Fermi energy) for the ideal surface structure with two additional electrons.
Mentions: In order to establish a possible interpretation for the surface dynamics induced by the electron injection of the STM sequence, we carried out a DFT calculation using the Perdew–Burke–Ernzerhof generalized gradient approximation with the ABINIT code and plane-wave-based norm-conserving pseudopotentials. A supercell including a slab model with five ZnTe(110) layers was used for the calculation. The dangling bonds of atoms in the bottom layer were passivated by hydrogen atoms, as shown in figure 4(a). The energy cutoff of the calculation was 60 Ry. As the sampling k-points, we used 8 × 8 × 2 grids within the first Brillouin zone. Here, we focused on a possibility of the atomic displacement of the topmost Zn atom, because the Zn atom is considered to be most easily desorbed from the surface, referring to the previous study [9], which reports that the defects on the cleaved ZnTe(110) surface mainly consist of the absences of Zn only or Zn–Te pairs and not Te only. As a possible computational model to describe the atomic displacement of the surface Zn atom toward the vacuum side from the reconstructed structure, we consider the ideal (110) surface structure consisting of a truncated bulk structure. The stability of the surface was analyzed by comparing the total energy difference between the ideal and reconstructed surface structures in the neutral state and in charged states with up to six additional electrons per supercell.

View Article: PubMed Central - PubMed

ABSTRACT

The reconstructed surface structure of the II&ndash;VI semiconductor ZnTe (110), which is a promising material in the research field of semiconductor spintronics, was studied by scanning tunneling microscopy/spectroscopy (STM/STS). First, the surface states formed by reconstruction by the charge transfer of dangling bond electrons from cationic Zn to anionic Te atoms, which are similar to those of IV and III&ndash;V semiconductors, were confirmed in real space. Secondly, oscillation in tunneling current between binary states, which is considered to reflect a conformational change in the topmost Zn&ndash;Te structure between the reconstructed and bulk-like ideal structures, was directly observed by STM. Third, using the technique of charge injection, a surface atomic structure was successfully fabricated, suggesting the possibility of atomic-scale manipulation of this widely applicable surface of ZnTe.

No MeSH data available.