Interplay between tip-induced band bending and voltage-dependent surface corrugation on GaAs(110) surfaces (original) (raw)
Related papers
Applied Surface Science, 1998
We report bias voltage-dependent images of scanning tunneling microscopy taken on a GaAs 110 surface with small Ag Ž. clusters. The direction of the observed atom rows changes at certain negative and positive sample bias voltages V. Such s Ž. changes are attributed to the different atoms Ga or As in the case of V-0 and to the different surface states of Ga in the s case of V) 0. The images also show a change in contrast with the V. All of these results are explained by tip-induced and s s surface charge-induced band bendings in addition to the fundamental surface states.
Influence of surface states on tunneling spectra of n-type GaAs (110) surfaces
2009
We show that surface states within the conduction band of n-type GaAs͑110͒ surfaces play an important role in reducing the tunneling current out of an accumulation layer that forms due to an applied potential from a nearby probe tip. Numerical computation of the tunneling current combined with an electrostatic potential computation of the tip-induced band bending ͑TIBB͒ reveals that occupation of the surface states limits the TIBB, thus leading to the limitation of the accumulation. As a result, the tunneling current out of the accumulation layer is strongly suppressed, which is in quantitative agreement with the experiment.
Fixing the Energy Scale in Scanning Tunneling Microscopy on Semiconductor Surfaces
Physical Review Letters, 2013
In scanning tunneling experiments on semiconductor surfaces, the energy scale within the tunneling junction is usually unknown due to tip-induced band bending. Here, we experimentally recover the zero point of the energy scale by combining scanning tunneling microscopy with Kelvin probe force spectroscopy. With this technique, we revisit shallow acceptors buried in GaAs. Enhanced acceptorrelated conductance is observed in negative, zero, and positive band-bending regimes. An Anderson-Hubbard model is used to rationalize our findings, capturing the crossover between the acceptor state being part of an impurity band for zero band bending and the acceptor state being split off and localized for strong negative or positive band bending, respectively.
Applied Surface Science, 1998
Using scanning tunneling microscopy, Coulomb blockade of tunneling electrons was realized on a simple metal/semiconductor system, by taking a sample of individual Ag clusters formed on the clean GaAs(110) surface. The second barrier of a two tunneling junction is at a space interval at the Ag/GaAs(110) interface, which is naturally formed due to a lattice match of the cluster and the GaAs(110) substrate. Images of differential conductance taken of the clusters by current image tunneling spectroscopy (CITS) demonstrate that the electron tunneling is closely related to detailed atomic structures of the clusters.
Physical Review B, 2007
The electronic properties of shallow acceptors in p-doped GaAs{110} are investigated with scanning tunneling microscopy at low temperature. Shallow acceptors are known to exhibit distinct triangular contrasts in Scanning tunneling microscopy images for certain bias voltages. Spatially resolved I(V)-spectroscopy is performed to identify their energetic origin and behavior. A crucial parameter -the STM tip's work function -is determined experimentally. The voltage dependent potential configuration and band bending situation is derived. Ways to validate the calculations with the experiment are discussed. Differential conductivity maps reveal that the triangular contrasts are only observed with a depletion layer present under the STM tip. The tunnel process leading to the anisotropic contrasts calls for electrons to tunnel through vacuum gap and a finite region in the semiconductor.
Physical Review B
Ab initio pseudopotential total energy techniques are used to investigate the tip-surface interaction in atomic force microscopy on a GaAs͑110͒ surface with a Si tip. Our simulations show significant surface relaxation effects in the near contact region, which lead to a complicated behavior of the total energy and force curves. In particular, the tip-induced displacement of the Ga atoms can exceed 1 Å even in the attractive force region, leading to hysteresis in the energy and force curves. These large tip-induced relaxations of the surface Ga atoms provide a natural explanation to the simultaneous imaging of both anions and cations in recent nearcontact scanning tunneling microscopy experiments on this surface. We show that, for tip-surface distances where the surface topography remains unchanged and for a charge neutral Si tip, only the anion sublattice can be resolved in noncontact atomic force microscopy. Close to contact, our simulations prove that, even for atomically sharp tips ͑1͒ there is a significant contribution to the total interaction from tip atoms different from the apex atom; ͑2͒ large lateral ͑bonding͒ forces on the tip apex may develop and change the tip structure well before significant normal repulsive forces appear. ͓S0163-1829͑99͒09939-7͔
Internal image potential in semiconductors: Effect on scanning tunneling microscopy
Physical Review B, 1993
The tunneling of electrons from a semiconductor surface to a metal tip, across a vacuum gap, is influenced by two image interactions: an attractive image potential in the vacuum region, which lowers the apparent tunneling barrier, and a repulsive image potential in the semiconductor interior, which raises it for conduction-band electrons. We report on detailed calculations of tunneling currents and apparent barrier heights for a model metal-vacuum-semiconductor junction which utilize semiclassical dielectric functions to compute the image potential in all three regions. The effect of image forces is found to be small compared to that of either the vacuum barrier or tip-induced band bending. In particular, the image-induced barrier in the semiconductor has only a minor influence on either the apparent barrier height or the shape of current-voltage characteristics, both of which are routinely measured in scanning-tunneling-microscopy experiments. This finding is explained by a qualitative WKB analysis and several simple arguments.
Dual-probe scanning tunneling microscope for study of nanoscale metal-semiconductor interfaces
Review of Scientific Instruments, 2005
Using a dual-probe scanning tunneling microscope, we have performed three-terminal ballistic electron emission spectroscopy on Au/ GaAs͑100͒ by contacting the patterned metallic thin film with one tip and injecting ballistic electrons with another tip. The collector current spectra agree with a Monte-Carlo simulation based on modified planar tunneling theory. Our results suggest that it is possible to study nanoscale metal-semiconductor interfaces without the requirement of an externally-contacted continuous metal thin film.
Scanning tunneling microscopy of semiconductor surfaces
Surface Science Reports, 1996
This review describes advances in understanding the structural, electronic, and chemical properties of clean low-index semiconductor surfaces during the first decade following the advent of the scanning tunneling microscope (STM). The principles of STM are discussed together with the instrumentation required to perform STM measurements on semiconductor surfaces in ultrahigh vacuum. A comprehensive review of the structures of the clean, low-index surfaces of elemental and compound semiconductors is presented. These structures are discussed using the general physical principles that determine them.
Semiconductor interfaces studied by scanning tunneling microscopy and potentiometry
Surface Science, 1987
The potential distribution across the cleaved end-faces of a forward-biased GaAs pn Junction and a &As double heterojunction laser diode were simultaneously mapped with its surface topography. In both cases space charge regions next to the interfaces are visible with nanometer resolution. The potentiometric method shows to be very useful for the localization of heterostructure interfaces.