Effect of Doping Density on the Charge Rearrangement and Interface Dipole at the Molecule–Silicon Interface

Yaffe, Omer; Pujari, Sidharam P.; Sinai, Ofer; Vilan, Ayelet; Zuilhof, Han; Kahn, Antoine; Kronik, Leeor; Cohen, Hagai

doi:10.1021/jp403177e

Cited by 16 publications

(39 citation statements)

References 52 publications

(77 reference statements)

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“…They open up the door to the examination of the influence of doping in several such systems, e.g., well-ordered SAMs of organic molecules on Si, which have been reported to be well passivated, but may possess significant doping-related surface polarization effects. [19][20][21]23 When dealing with nonpassivated semiconductor surfaces, additional considerations must be taken into account. In this case, one expects charge transfer between the semiconductor bulk and surface states, resulting in a surface SCR that further modifies the work function, 12,13 and affects surface properties, in general.…”

Section: Slab Calculations: Fermi Level and Work-function Dependenmentioning

confidence: 99%

“…However, doping has been suggested to play a more active, explicit role in several important phenomena, e.g., thermoelectric power, [14][15][16] surface reconstruction and passivation, 17,18 and interface dipole and level alignment at organic-inorganic interfaces. [19][20][21][22][23] Furthermore, the above-mentioned separation of length scales becomes increasingly blurred for high doping levels where the SCR is much narrower.…”

Section: Introductionmentioning

confidence: 99%

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Simulated doping of Si from first principles using pseudoatoms

Sinai

Kronik

2013

Phys. Rev. B

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Semiconductor doping is a process of fundamental importance to semiconductor physics and solid-state electronics, but cannot be explicitly simulated from first principles due to the huge system size needed for most doping scenarios. We examine the efficacy of the simulation of doping in silicon by the inclusion of "pseudoatoms" with fractional nuclear charge, introduced via specially constructed pseudopotentials. These provide a net charge carrier concentration matching an arbitrarily chosen doping level, at no increase of the computational cost. By extending this approach to consider minute deviations from the integer charge, we demonstrate that the electron Fermi level can be set to any value within the forbidden gap, at minimal perturbation of the electronic structure. Beyond the bulk scenario, we successfully simulate the development of the space-charge region in a heavily doped p-n junction and the doping dependence of the work function of the hydrogen-passivated (semiconducting) Si(111) surface.

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Section: Slab Calculations: Fermi Level and Work-function Dependenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Simulated doping of Si from first principles using pseudoatoms

Sinai

Kronik

2013

Phys. Rev. B

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“…(1) The distinction between ϕ surf and ϕ slab is no longer clear; this is in keeping with the blurring of the distinction between band bending and surface dipole at microscopic distances from the surface [12]. We denote their sum by ϕ tot S .…”

Section: B Finding the Common Energy U Dmentioning

confidence: 99%

“…However, in many cases global doping effects may play a crucial part in determining the microscopic properties of the surface or interface. These include, to name a few experimental examples reported in recent literature, the observation of a doping-dependent surface dipole [11,12], control of the work function of ZnO surfaces via doping-dependent charge transfer to an adsorbed The semi-infinite part of the system is "moved left," creating a parallel capacitor with an intermediate vacuum "layer." (d) Description of a typical slab system after contraction of the SCR to a charged sheet.…”

Section: Introductionmentioning

confidence: 99%

Multiscale approach to the electronic structure of doped semiconductor surfaces

et al. 2015

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The electronic effects of semiconductor doping pose a unique challenge for first-principles simulations, because the typically low concentration of dopants would require intractably large system sizes in an explicit atomistic treatment. In systems which do not display longrange band bending, a satisfactory remedy is offered by the use of "pseudoatoms", with a fractional nuclear charge matching the bulk doping concentration. However, this alone is insufficient to account for charged semiconductor surfaces in the general case, where the associated space-charge region (SCR) may be very wide relative to tractable simulation dimensions. One generalization of the pseudoatom approach which overcomes this difficulty relies on the introduction of an artificially high doping level within a slab calculation, in conjunction with a multi-scale electrostatic energy correction. Here, we present an alternative technique that naturally extends the pseudoatom approach while bypassing the need for calculations with an unrealistically high doping level. It is based on the introduction of a two-dimensional sheet of charge within a slab-based surface calculation, which mimics the SCR-related field, along with free charge such that the system is neutral overall. The amount of charge involved is obtained from charge conservation and Fermi level equilibration between the bulk, treated semi-classically, and the electronic states of the slab/surface, which are treated quantum-mechanically. The method, which we call CREST -the Charge-Reservoir Electrostatic Sheet Technique -can be used with standard electronic structure codes. We validate the approach using a simple tight-binding model, which allows for comparison of its results with calculations encompassing the full SCR explicitly. Specifically, we show that CREST successfully predicts scenarios spanning the full range from no to full Fermi-level pinning. We then employ it with density functional theory, where it is used to obtain insights into the electronic structures of the "clean-cleaved" Si(111) surface and its buckled (2x1) reconstruction, at various doping densities.

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“…9−12 The most widely used approaches for derivatizing the surface of silicon involve the formation of Si−H bonds (hydride termination), 13−17 Si−O bonds (oxidation and silyl ether linkages), 18−21 Si−Cl bonds, 22,23 and Si−C bonds (via reactions such as hydrosilylation). 24−32 The nature of the linkage to the surface, including bond length and dipole, can have profound effects on electronic properties of the underlying silicon, 33−37 including modulation of work function, 38−40 introduction of surface states of varying energies, 41 as well as affecting the packing of an overlying organic monolayer in the case of molecular adsorbates. 37,42 The band edges of a semiconductor are highly sensitive to the nature of the bound surface molecules, 37 and thus choice of surface termination is important.…”

Section: ■ Introductionmentioning

confidence: 99%

From Molecules to Surfaces: Radical-Based Mechanisms of Si–S and Si–Se Bond Formation on Silicon

Buriak

Sikder

2015

J. Am. Chem. Soc.

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The derivatization of silicon surfaces can have profound effects on the underlying electronic properties of the semiconductor. In this work, we investigate the radical surface chemistry of silicon with a range of organochalcogenide reagents (comprising S and Se) on a hydride-terminated silicon surface, to cleanly and efficiently produce surface Si-S and Si-Se bonds, at ambient temperature. Using a diazonium-based radical initiator, which induces formation of surface silicon radicals, a group of organochalcogenides were screened for reactivity at room temperature, including di-n-butyl disulfide, diphenyl disulfide, diphenyl diselenide, di-n-butyl sulfide, diphenyl selenide, diphenyl sulfide, 1-octadecanethiol, t-butyl disulfide, and t-butylthiol, which comprises the disulfide, diselenide, thiol, and thioether functionalities. The surface reactions were monitored by transmission mode Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ionization mass spectrometry. Calculation of Si-Hx consumption, a semiquantitative measure of yield of production of surface-bound Si-E bonds (E = S, Se), was carried out via FTIR spectroscopy. Control experiments, sans the BBD diazonium radical initiator, were all negative for any evident incorporation, as determined by FTIR spectroscopy. The functional groups that did react with surface silicon radicals included the dialkyl/diphenyl disulfides, diphenyl diselenide, and 1-octadecanethiol, but not t-butylthiol, diphenyl sulfide/selenide, and di-n-butyl sulfide. Through a comparison with the rich body of literature regarding molecular radicals, and in particular, silyl radicals, reaction mechanisms were proposed for each. Armed with an understanding of the reaction mechanisms, much of the known chemistry within the extensive body of radical-based reactivity has the potential to be harnessed on silicon and could be extended to a range of technologically relevant semiconductor surfaces, such as germanium, carbon, and others.

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Effect of Doping Density on the Charge Rearrangement and Interface Dipole at the Molecule–Silicon Interface

Cited by 16 publications

References 52 publications

Simulated doping of Si from first principles using pseudoatoms

Simulated doping of Si from first principles using pseudoatoms

Multiscale approach to the electronic structure of doped semiconductor surfaces

From Molecules to Surfaces: Radical-Based Mechanisms of Si–S and Si–Se Bond Formation on Silicon

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