Search query: Physical Theory of Semiconductor Surfaces

Related papers:

author_names: Charles Geoffrey Blyth Garrett

Walter Houser Brattain
title: Physical Theory of Semiconductor Surfaces
year: 1955

abstract: Functional hybrid interfaces between organic molecules and semiconductors are central to many emerging information and solar energy conversion technologies. Here we demonstrate a general, empirical parameter free approach for computing and understanding frontier orbital energies or redox levels of a broad class of covalently bonded organic semiconductor surfaces. We develop this framework in the context of specific density functional theory (DFT) and many body perturbation theory calculations, within the GW approximation, of an exemplar interface, thiophene functionalized silicon (111) Through detailed calculations taking into account structural and binding energetics of mixed monolayers consisting of both covalently attached thiophene and hydrogen, chlorine, methyl, and other passivating groups, we quantify the impact of coverage, nonlocal polarization, and interface dipole effects on the alignment of the thiophene frontier orbital energies with the silicon band edges. For thiophene adsorbate frontier orbital energies, we observe significant corrections to standard DFT ~1 eV) including large nonlocal electrostatic polarization effects ~1.6 eV) Importantly, both results can be rationalized from knowledge of the electronic structure of the isolated thiophene molecule and silicon substrate systems. Silicon band edge energies are predicted to vary by more than 2.5 eV, while molecular orbital energies stay similar, with the different functional groups studied, suggesting the prospect of tuning energy alignment over a wide range for photoelectrochemistry and other applications.
author_names: Min Yu

Peter W Doak

Isaac Tamblyn

Jeffrey B Neaton
title: Theory of Covalent Adsorbate Frontier Orbital Energies on Functionalized Light Absorbing Semiconductor Surfaces.
venue: The journal of physical chemistry letters
year: 2013

abstract: Submitted for the MAR09 Meeting of The American Physical Society Theory of the lifetime of adsorbate vibrations on semiconductor surfaces PETER KRATZER, SUNG SAKONG, University Duisburg Essen On semiconductor surfaces, the vibrational lifetime of covalently bonded adsorbates is rather long (nanoseconds or more) since the band gap precludes electronic dissipation. Due to the quantum nature of vibrational states, such slow relaxation is expected, as the large quantum of the bond stretching must be converted into several smaller (phononic or vibronic) quanta by a high order process. We use density functional theory calculations to map out the high dimensional potential energy surface governing the anharmonic coupling of the stretching to the local bending and shift modes, while the coupling to the substrate phonons is treated perturbatively. Applying our method to the vibrational lifetime of CO on Si(100) we find that the CO stretching relaxes predominantly via an intermediate state consisting of four shift and/or bending quanta and one phonon. Good agreement with the measured lifetime of 2.3 ns at T 100 K is achieved. As a second application, we elucidate the role of intermediate vibrational states in the relaxation of the stretching vibration at Ge(100):H surfaces. For Ge surface dimers saturated by one H and one D atom, the lifetime of the Ge H stretching vibration is up to five times shorter and less temperature dependent than in Ge dimers homogeneously saturated by H. Our analysis shows that the symmetry breaking associated with the isotope mixture opens up additional relaxation channels. Peter Kratzer University Duisburg Essen Date submitted: 21 Nov 2008 Electronic form version 1.4
author_names: Peter Kratzer

Sung Sakong
title: Theory of the lifetime of adsorbate vibrations on semiconductor surfaces
year: 2009

abstract: Electron phonon coupling can hamper carrier transport either by scattering or by the formation of mass enhanced polarons. Here, we use time dependent density functional theory molecular dynamics simulations to show that phonons can also promote the transport of excited carriers. Using nonpolar InAs (110) surface as an example, we identify phonon mediated coupling between electronic states close in energy as the origin for the enhanced transport. In particular, the coupling causes localized excitons in the resonant surface states to propagate into bulk with velocities as high as 10(6) cm/s. The theory also predicts temperature enhanced carrier transport, which may be observable in ultrathin nanostructures.
author_names: Dong Han

Junhyeok Bang

Weiyu Xie

Vincent Meunier

Shengbai B Zhang
title: Phonon Enabled Carrier Transport of Localized States at Non Polar Semiconductor Surfaces: A First Principles Based Prediction.
venue: The journal of physical chemistry letters
year: 2016

abstract: The intention of this paper is to present theoretical and experimental results to demonstrate the wide range of application of Brillouin scattering (BS) in investigating mechanical and photoelastic properties of semiconductors. It is well known that BS has been used since the 1930s to study bulk acoustic waves in transparent media. The spreading of the laser has made it possible to use BS as a standard method of quantitative measurement of various physical properties [1] In case of transparent media the optical beam penetrates several acoustic wavelengths in all dimensions, so that wavevector is conserved in the scattering process and the scattering geometry completely specifies the acoustic wavevector. Conversely in opaque materials, like semiconductors in the spectrum of visible radiation, the penetration depth of light is rather small and the scattering may involve both proper surface excitations and bulk phonons at and near the surface, where the surface boundary conditions play an important role. The experimental approach to studying surface phonons of opaque materials in the long wavelength limit is relatively recent [2,3] and it has been made possible by considerable advances in instrumentation [4,5] A simple Fabry Perot interferometer which is currently used in bulk Brillouin experiments is not useful in surface scattering.
author_names: Fabrizio Nizzoli
title: Theory of Brillouin Scattering from Surfaces Waves in Semiconductor Supported Films and Layered Structures
year: 1985

abstract: A heterojunction made by coexposed anatase (001) (101) surfaces is studied using an explicit atomistic model of the interface via density functional theory. High photoactivity for this system has been demonstrated recently. Usually, the nature of a semiconductor heterojunction is evaluated by looking at band edges of the separate, noninteracting units, thus neglecting interfacial effects. Our results show non negligible structural and electronic effects occurring at the junction, but because of the canceling nature of these effects, the alignment of the bands is qualitatively similar for the real interface and for the separated, noninteracting fragments. We also show from first principles that upon light absorption and electron excitation, the junction promotes charge carrier separation via localization of holes at O ions of the (001) side and electrons at Ti ions of the (101) side of the junction. This hinders recombination and is most likely the reason for high photoactivity.
author_names: Giovanni M Di Liberto

Sergio Tosoni

Gianfranco Pacchioni
title: Role of Heterojunction in Charge Carrier Separation in Coexposed Anatase (001) (101) Surfaces.
venue: The journal of physical chemistry letters
year: 2019

abstract: Abstract.I investigated the spectra of well ordered semiconductor surfaces within an ab initio framework. Both the quasi particle spectrum of electron and hole states and the optical differential reflectivity spectrum were addressed. As examples, I discuss the spectra of three surfaces: Si(111) (2x1) hydrogenated H:Si(111) (1x1) and Si adatom terminated 6H SiC(0001) (x) I studied a number of physical features beyond the single particle band structure picture. In the case of Si(111) (2x1) the dangling bond surface states give rise to a surface exciton which dominates the differential reflectivity spectrum. In the case of 6H SiC(0001) (x) a Mott Hubbard metal insulator transition is observed. All calculations were performed within many body perturbation theory, employing single and two particle Green functions. The solutions of the corresponding equations of motion yielded the observable excitations, i.e. single particle electron and hole excitations, as well as bound and resonant electron hole pair excitations.
author_names: Michael Rohlfing
title: Quasiparticle spectrum and optical excitations of semiconductor surfaces
year: 2001

abstract: Tin diselenide (SnSe2) is a van der Waals semiconductor, which spontaneously forms a subnanometric SnO2 skin once exposed to air. Here, by means of surface science spectroscopies and density functional theory, we have investigated the charge redistribution at the SnO2 SnSe2 heterojunction in both oxidative and humid environments. Explicitly, we find that the work function of the pristine SnSe2 surface increases by 0.23 and 0.40 eV upon exposure to O2 and air, respectively, with a charge transfer reaching 0.56 e /SnO2 between the underlying SnSe2 and the SnO2 skin. Remarkably, both pristine SnSe2 and defective SnSe2 display chemical inertness toward water, in contrast to other metal chalcogenides. Conversely, the SnO2 SnSe2 interface formed upon surface oxidation is highly reactive toward water, with subsequent implications for SnSe2 based devices working in ambient humidity, including chemical sensors. Our findings also imply that recent reports on humidity sensing with SnSe2 should be reinterpreted, considering the pivotal role of the oxide skin in the interaction with water molecules.
author_names: Gianluca D'Olimpio

Francesca Genuzio

Tevfik Onur Mentes

Valentina Paolucci

Chia Nung Kuo

Amjad Al Taleb

Chin Shan Lue

Piero Torelli

Daniel Farias

Andrea Locatelli

Danil W Boukhvalov

Carlo Cantalini

Antonio Politano
title: Charge Redistribution Mechanisms in SnSe2 Surfaces Exposed to Oxidative and Humid Environments and Their Related Influence on Chemical Sensing
venue: The journal of physical chemistry letters
year: 2020

abstract: Understanding photoinduced charge transfer from nanomaterials is essential to the many applications of these materials. This review summarizes recent progress in understanding charge transfer from quantum dots (QDs) an ideal model system for investigating fundamental charge transfer properties of low dimensional quantum confined nanomaterials. We first discuss charge transfer from QDs to weakly coupled acceptors within the framework of Marcus nonadiabatic electron transfer (ET) theory, focusing on the dependence of ET rates on reorganization energy, electronic coupling, and driving force. Because of the strong electron hole interaction, we show that ET from QDs should be described by the Auger assisted ET model, which is significantly different from ET between molecules or from bulk semiconductor electrodes. For strongly quantum confined QDs on semiconductor surfaces, the coupling can fall within the strong coupling limit, in which case the donor acceptor interaction and ET properties can be described by the Newns Anderson model of chemisorption. We also briefly discuss recent progress in controlling charge transfer properties in quantum confined nanoheterostructures through wavefunction engineering and multiple exciton dissociation. Finally, we identify a few key areas for further research.
author_names: Haiming Zhu

Ye Yang

Kaifeng Wu

Tianquan Lian
title: Charge Transfer Dynamics from Photoexcited Semiconductor Quantum Dots.
venue: Annual review of physical chemistry
year: 2016

abstract: This work presents extensive first principles studies of the energetics and the reconstructions of the clean low index (111) (110) (100) and high index (113) surfaces of the three group IV semiconductors diamond, silicon, and germanium. The calculations have been performed within density functional theory (DFT) using the local density approximation (LDA) and the repeated slab approximation. Different reconstructions including the largest ones observed experimentally such as Si(111)7?7 and Si(110)16?2 have been investigated. The atomic geometries have been optimized in order to find the minimum of the total energy. For these atomic structures the electronic band structures have also been calculated. For the most interesting surface reconstructions scanning tunneling microscopy (STM) images have been simulated in order to make a comparison with experimentally observed surface images. Presented results highlight the physical origins of the reconstruction behavior in dependence on surface orientation and size of the group IV atoms. Clear evidence for an opposite reconstruction behavior of diamond and Si or Ge surfaces is shown. Adatoms, interstitials, and symmetry breaking distortions are unlikely for diamond as a consequence of the short interatomic distances and strong bonds. However, such elements of the surface reconstruction occur on Si and Ge surfaces. The complicated interplay of bonding, resulting atomic geometry, and accompanying electronic structure has been derived and used to discuss driving forces for the surface reconstruction. A rather complete data base of absolute surface energies of group IV semiconductors is presented. For all the elements, there is a strong tendency to reduce substantially surface energies by taking into account surface reconstructions. The absolute surface energies have been used to discuss the equilibrium shapes of diamond, silicon and germanium.
author_names: Andrey Stekolnikov
title: Reconstruction of group IV semiconductor surfaces origin, energetics and consequences
year: 2005