Shyamal Konar

Electrical transition of (3,3) carbon nanotube on patterned hydrogen terminated Si(001)-2 × 1 driven by electric field

Structure, energetics, and electrical properties of (3,3) carbon nanotube (CNT) supported on patterned hydrogen terminated Si(001): 2 × 1 surface are studied using density functional theory. Our investigation reveals that an otherwise metallic (3,3) CNT when supported becomes semiconducting with a band gap of ≈0.5 eV due to its strong interaction with the surface. During adsorption, Si-C bonds form at the interface and charges transfer from Si surface to CNT. The Si-C bonds at the interface are partially covalent and partially ionic in nature. Under the application of an external electric field, the bandgap of the supported CNT reduces to zero, hence rendering the system metallic.

Formation of atomic gold chain on hydrogen terminated Si(001):3×1 surface: A density functional study

Electronic structure calculations are carried out for investigating the formation of a stable atomic gold wire on the hydrogen terminated Si(001):3×1 [H–Si(001):3×1] surface. The H–Si(001):3×1 surface is patterned in various ways by removing desired hydrogen atoms from the surface. Gold atoms are adsorbed on the patterned H–Si(001):3×1 surface at various submonolayer coverage. However, zigzag continuous Au chains are found to be favorable on patterned H–Si(001):3×1 surfaces at a 4/9 monolayer (ML) coverage. The stabilities of continuous atomic gold chains on the patterned H–Si(001):3×1 surfaces are compared. In addition, the Au chains on the patterned H–Si(001):3×1 surfaces are compared with the existing results of the favorable Au chain structures on patterned H–Si(001):1×1 surfaces [Konar et al., Phys. Rev. B 77, 245411 (2008)], and it is found that a continuous Au chain on the H–Si(001):3×1 surface is energetically more favorable. Our calculations also reveal that beyond the 4/9 ML coverage, the additi...

Structural evolution due to Zn and Te adsorption on As-exposed Si(211): density functional calculation

Systematic theoretical investigations are carried out under the density functional formalism in an effort to understand the initial structural evolution due to the adsorption of ZnTe on As-exposed Si(211). Our calculations indicate that after the adsorption of Zn and Te on the As-exposed Si(211), the stable atomic structure qualitatively follows the ideal atomic structure of Si(211) with alteration of various bond lengths. Since the basic symmetry of the Si(211) is preserved after the adsorption of ZnTe, the deposition of ZnTe on the As terminated Si(211) prior to the deposition of CdTe and HgCdTe is useful for obtaining an ultimate quality layer of HgCdTe on Si(211). Some of our results are compared with the available experimental results, and they are found to agree with each other qualitatively.