First-principles study of the tunnel current between a scanning tunneling microscopy tip and a hydrogen-adsorbedSi(001)surface

Abstract

A scanning tunneling microscopy ͑STM͒ image of a hydrogen-adsorbed Si͑001͒ surface is studied using first-principles electron-conduction calculation. The resultant STM image and scanning tunneling spectroscopy spectra are in agreement with experimental results. The contributions of the states of bare dimers to the tunnel current are markedly large, and the states of the dimers rarely affect the STM images. The tunnel currents do not pass through the centers of the dimers but go through the edges of the dimers with local loop currents. In addition, when the tip exists above the hydrogen-adsorbed dimer, there are certain contributions from the state of the adjacent bare dimers to the tunnel current. This leads to the STM image in which the hydrogen-adsorbed dimers neighboring bare dimers look higher than those surrounded by hydrogen-adsorbed dimers. These results are consistent with the experimental images observed by STM.

Time-saving first-principles calculation method for electron transport between jellium electrodes

“…Since the system is divided into the equally spaced grid points in the RSFD approach and the wave functions and potentials are directly defined on the grid points, one can strictly treat systems with arbitrary boundary conditions and eliminate difficulties arising from the incompleteness of a basis set. Therefore, the OBM method enables us to examine tunneling transport [14] as well as ballistic transport [5,6,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] in nanostructures suspended between semi-infinite electrodes with a high degree of accuracy.…”

Parallel scanning tunneling microscopy imaging of low dimensional nanostructures

“…9 These computational techniques may be classified in two categories: those relying on first order perturbation theory for the tip-sample interactions and those which account for all multiple scattering events at the STM interface. 21 Despite some groups having implemented the NEGF for transport properties across nanodevices [22][23][24] at the ab initio level, the computational complexity of such calculations is too large for providing STM images in a fast way. This approach was pointed out by Tersoff and Hamann ͑TH͒ in their seminal work on STM theory 19 employing Bardeen's formalism 20 to obtain the tip-sample matrix elements.…”

Electron Transport Suppression from Tip−π State Interaction on Si(100)-2 × 1 Surfaces

“…Surface states originating from dangling bonds (DBs) play a pivotal role in providing active reaction sites − with covalent attachments and assisting conductance − in electron transport. For instance, the π/π* states induced from silicon surface dimerization are of great importance for understanding the conducting mechanisms. , Moreover, such π-like states are important in organic molecular electronics and have been intimately associated with the formation of some particular phenomena such as negative differential resistance (NDR) in recent studies. , In the theoretical research of Fan et al, the mismatch of the energy alignment between the nonlocal π* state of the conducting molecule and the metallic lead states results in NDR, while the NDR mechanism in the theoretical investigation by Bevan et al of a styrene adsorbed on a silicon substrate is attributed to the bias-induced pulling of the π state of the molecule out of the resonance window and into the band gap of the silicon substrate.…”

“…The DBs of an unpassivated silicon surface can serve as localized charge trap sites, and their corresponding energy levels often appear within the band gap close to the Fermi level and hence determine much of the electronic behavior of the surface. Intense research has been devoted to exploring the functionality of the DB in forming or characterizing reconstructed surfaces both experimentally − and theoretically. − One area of heavy interest is electron transport through crystallized surfaces with DBs. Hata et al presented a refined interpretation of images of Si(100) produced by a scanning tunneling microscope (STM) and attributed the typical high surface bias used to observe the π/π* state to the influence of the adsorbed defects.…”

“…In general, theoretical transport studies of DBs are performed in two directions: along and perpendicular , to the surface. Much work has been done in these regards.…”