Angle-resolved photoelectron spectroscopy investigation of intrinsic surface states on the Ge(001)-(2 × 1) reconstructed surface

1983 ◽  
Vol 27 (6) ◽  
pp. 3924-3926 ◽  
Author(s):  
Jeffrey G. Nelson ◽  
William J. Gignac ◽  
R. Stanley Williams ◽  
Steven W. Robey ◽  
J. G. Tobin ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Surface States ◽  
Reconstructed Surface

scholarly journals New insight on the role of localisation in the electronic structure of the Si(111)(7 × 7) surfaces

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. E. Dávila ◽  
J. Ávila ◽  
I. R. Colambo ◽  
D. B. Putungan ◽  
D. P. Woodruff ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Photoelectron Spectroscopy ◽  
Surface States ◽  
Emission Angle ◽  
Final State ◽  
Surface Mapping ◽  
Arpes Data ◽  
Reconstructed Surface ◽  
Bulk Band

AbstractNew angle-resolved photoelectron spectroscopy (ARPES) data, recorded at several different photon energies from the Si(111)(7 × 7) surface, show that the well-known S1 and S2 surface states that lie in the bulk band gap are localised at specific (adatom and rest atom) sites on the reconstructed surface. The variations in the photoemission intensity from these states as a function of polar and azimuthal emission angle, and incident photon energy, are not consistent with Fermi surface mapping but are well-described by calculations of the multiple elastic scattering in the final state. This localisation of the most shallowly bound S1 state is consistent with the lack of significant dispersion, with no evidence of Fermi surface crossing, implying that the surface is not, as has been previously proposed, metallic in character. Our findings highlight the importance of final state scattering in interpreting ARPES data, an aspect that is routinely ignored and can lead to misleading conclusions.

Electronic and Vibrational Properties of Single Crystal Surfaces of NiAl

1986 ◽  
Vol 83 ◽  
Author(s):  
S.-C. Lui ◽  
J. M. Mundenar ◽  
E. W. Plummer ◽  
M. E. Mostoller ◽  
R. M. Nicklow ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Nearest Neighbor ◽  
Surface States ◽  
Active Surface ◽  
Atomic Displacement ◽  
Inelastic Electron ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Nial Alloy ◽  
Bulk Surface

ABSTRACTSurface and bulk electronic structure of the ordered NiAl alloy were measured using angle resolved photoelectron spectroscopy. The measured bulk d-bands (Ni like) were observed to be narrower than theoretically calculated d band widths which are 20 to 40% wider (depending upon what is used as a measure of the width). At least two surface states were observed on both the (110) and (111) surfaces. The nature of these surface states and their relationship to the bulk band structure is discussed. Dispersion of bulk phonons was measured by neutron scattering and fitted with a fourth nearest neighbor Born-von Karman model. Dipole active surface phonons on the (110) and (111) surfaces were observed by inelastic electron scattering and the frequencies also calculated assuming a truncated bulk surface. The calculated surface modes present a qualitative picture of the atomic displacement at each surface and also show that the surface phonon energy and intensity depends upon the structure of the surface.

scholarly journals Weyl fermions, Fermi arcs, and minority-spin carriers in ferromagnetic CoS2

2020 ◽  
Vol 6 (51) ◽  
pp. eabd5000
Author(s):  
Niels B. M. Schröter ◽  
Iñigo Robredo ◽  
Sebastian Klemenz ◽  
Robert J. Kirby ◽  
Jonas A. Krieger ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Surface States ◽  
Anomalous Hall Effect ◽  
Half Metallicity ◽  
Spintronic Devices ◽  
Topological Materials ◽  
Fermi Arcs ◽  
Half Metal ◽  
Minority Spin ◽  
Electron Pocket

Magnetic Weyl semimetals are a newly discovered class of topological materials that may serve as a platform for exotic phenomena, such as axion insulators or the quantum anomalous Hall effect. Here, we use angle-resolved photoelectron spectroscopy and ab initio calculations to discover Weyl cones in CoS2, a ferromagnet with pyrite structure that has been long studied as a candidate for half-metallicity, which makes it an attractive material for spintronic devices. We directly observe the topological Fermi arc surface states that link the Weyl nodes, which will influence the performance of CoS2 as a spin injector by modifying its spin polarization at interfaces. In addition, we directly observe a minority-spin bulk electron pocket in the corner of the Brillouin zone, which proves that CoS2 cannot be a true half-metal.

Formation of interfacial phases in the epitaxial growth of Sb on Si(111)-7 ¥ 7 reconstructed surface

2002 ◽  
Vol 74 (9) ◽  
pp. 1651-1661 ◽  
Author(s):  
Vinod Kumar Paliwal ◽  
A. G. Vedeshwar ◽  
S. M. Shivaprasad
Keyword(s):  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Branching Ratio ◽  
Interface State ◽  
Peak Position ◽  
Band Bending ◽  
Desorption Process ◽  
Surface Phase Transformation ◽  
Complementary Techniques ◽  
Reconstructed Surface

Understanding the evolution of the Sb/Si(111) interface is of great interest in the formation of devices of nanodimensions. We have undertaken in situ (∼10-11 torr) studies of Sb adsorption (at room temperature) and its desorption on the 7 X 7 reconstructed Si(111) surface, by complementary techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and electron energy loss spectroscopy (EELS). For room-temperature (RT) Sb adsorption, the overlayer grows in the Frank van der Merwe mode, forming an interface state of δ(7 X 7) in the submonolayer Sb coverage regime. Adsorption of 1.0 monolayer (ML) Sb at RT shows an abrupt shift of 0.8 eV in the peak position of the Sb 3d5/2 transition owing to band-bending caused by a metallic (7 X 7) to a semiconducting (1 X 1) surface phase transformation. Changes observed in full width at half-maximum (fwhm) and Sb 3d3/2 and 3d5/2 branching ratio are discussed. Thermal annealing experiments provide evidence for agglomeration of Sb islands, before the multilayer and monolayer desorption. During this desorption process, we have observed two novel surface phases of (5 X 5) at 0.4 ML and (5√3 X 5√3­R30°) at 0.2 ML, stable at higher temperatures.

TiO2/Dye/Electrolyte Interface Engineering by Atomic Layer Deposited Ultra Thin SiO2 for Improved Dye Sensitized Solar Cell Performance

2010 ◽  
Vol 1260 ◽  
Author(s):  
Mariyappan Shanmugam ◽  
Braden Bills ◽  
Mahdi Farrokh Baroughi
Keyword(s):  
Photoelectron Spectroscopy ◽  
Short Circuit ◽  
Photovoltaic Performance ◽  
Dye Sensitized Solar Cells ◽  
Surface States ◽  
Atomic Layer ◽  
Open Circuit ◽  
Solar Cell Performance ◽  
Dye Sensitized ◽  
Layer Deposition

AbstractThe short circuit density (JSC) and open circuit voltage (VOC) of dye sensitized solar cells (DSSCs) were improved from 9.8 to 17.8 mA/cm2 and 728 to 743 mV by depositing an ultra thin SiO2 layer on mesoporous TiO2 using Atomic Layer Deposition (ALD) method. X ray photoelectron spectroscopy confirmed the growth of SiO2 on mesoporous TiO2 surface. It was also observed that the enhancement in DSSC performance highly depends on the thickness of the ALD grown SiO2 layers on mesoporous TiO2. Compared to the reference DSSC which used untreated TiO2, incorporation of 5 ALD cycles (about 5 atomic layers) of SiO2 on mesoporous TiO2 resulted in 80 % enhancement (E) in the photoconversion efficiency from 4 to 7.2%. It is believed that the deposition of the ultra thin SiO2 film on mesoporous TiO2 modifies the density and activity of the surface states and an optimized layer thickness (5 cycles) leads to significant improvement in the DSSC performance. The enhanced photovoltaic performance was confirmed by dark and illuminated I-V and external quantum efficiency (EQE) measurements.

NEW ELECTRONIC STATES ON CLEAN Si(110)-“16×2” SURFACES

1995 ◽  
Vol 02 (05) ◽  
pp. 573-577 ◽  
Author(s):  
A. CRICENTI ◽  
B. NESTERENKO ◽  
P. PERFETTI ◽  
G. LE LAY ◽  
C. SEBENNE
Keyword(s):  
Electronic Properties ◽  
Brillouin Zone ◽  
Photoelectron Spectroscopy ◽  
Structural Model ◽  
Electronic States ◽  
Surface States ◽  
Ultraviolet Photoelectron Spectroscopy ◽  
Surface Brillouin Zone ◽  
Differential Reflectivity

The electronic properties of a clean Si (110)-“16×2” surface have been studied by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and surface differential reflectivity (SDR). Four surface states have been recognized by ARUPS and their dispersions have been mapped along the main symmetry lines in the surface Brillouin zone. SDR experiments revealed transitions between filled and empty surface states at ~ 1.8, 2.4, and 2.9 eV. The results are explained on the basis of a new structural model of the Si (110)-“16×2” phase.

The Interaction of Carbon with the Diamond Surface: A Photoelectron Spectroscopy Study

1997 ◽  
Vol 498 ◽  
Author(s):  
P. Reinke ◽  
T. Wrase ◽  
K. Müller ◽  
P. Oelhafen ◽  
R. Locher
Keyword(s):  
Photoelectron Spectroscopy ◽  
Carbon Film ◽  
Polycrystalline Diamond ◽  
Carbon Films ◽  
Electron Beam Evaporation ◽  
Diamond Surface ◽  
Field Emission Current ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Reconstructed Surface

ABSTRACTThe modification of the diamond surface through adsorbants offers the opportunity to adjust the electronic and electron emission properties of the surface. In the study presented here, we deposited between 0.1 and 100 monolayers of carbon from an electron beam evaporation source on polycrystalline diamond films. Photoelectron spectroscopy in the ultraviolet and X-ray regime was employed to characterize the surface. Observations on a (100) polycrystalline diamond film show, that the surface is first depleted of hydrogen and subsequent growth of an amorphous carbon film (a-C) occurs on the reconstructed surface. The deposition of these ultrathin carbon films allows the controlled introduction of sp2carbon and p-π states onto the diamond surface. The field emission current increases considerably with the amount of sp2-carbon accumulated at the diamond surface. The current-voltage characteristics only partially follow the Fowler-Nordheim equation, and the results obtained for different films are described and possible emission mechanism discussed.

FORMATION OF ONE-DIMENSIONAL Ga STRUCTURES ON Si(5 5 12)-2 × 1 TRENCHED TEMPLATES

2011 ◽  
Vol 10 (01n02) ◽  
pp. 117-121 ◽  
Author(s):  
PRAVEEN KUMAR ◽  
MAHESH KUMAR ◽  
GOVIND ◽  
B. R. MEHTA ◽  
S. M. SHIVAPRASAD
Keyword(s):  
Photoelectron Spectroscopy ◽  
Large Scale ◽  
Secondary Electron Emission ◽  
Emission Spectra ◽  
Uptake Curve ◽  
Group Iii ◽  
Reduced Dimensions ◽  
Reconstructed Surface ◽  
Band Spectra ◽  
Group Iii Nitride

In the advent of GaN photonic devices, there is renewed interest in looking at the growth of nanostructures of III-Nitrides that can yield novel properties. To grow a high density of self-assembled GaN nanostructures on a large scale, there is a need to use templates with well-defined nanometer scale features. The Si (5 5 12)-2 × 1 surface is a naturally faceted stable surface that has several nanotrenches of (225) and (337) with a large unit cell of 5.35 × 0.77 nm2. In this work we present here, the first report on the X-ray photoelectron spectroscopy study of the adsorption kinetics of Ga on Si (5 5 12)-2 × 1 reconstructed surface. The uptake curve which is the plot of the ratio of Ga (2 p ) to Si (2 p ) intensity with deposition time, shows that Ga grows in a Stranski–Krastnov growth mode on Si (5 5 12) surface. The core level spectra of Si (2 p ) and Ga (2 p ) have been deconvoluted to see the evolution of the interface during the adsorption process of Ga . The valence-band spectra show the modification of the electronic structure and the secondary electron emission spectra yield the change in work function during Ga adsorption. Correlating the electronic and structural aspects of the interface formation results the study demonstrates the possibility of integrating Si and group III-nitride technologies while exploiting the novel properties due to reduced dimensions.

scholarly journals Фотоэмиссионные исследования электронной структуры GaN, выращенного методом молекулярно-пучковой эпитаксии с плазменной активацией азота

2019 ◽  
Vol 61 (12) ◽  
pp. 2294
Author(s):  
С.Н. Тимошнев ◽  
А.М. Мизеров ◽  
Г.В. Бенеманская ◽  
С.А. Кукушкин ◽  
А.Д. Буравлев
Keyword(s):  
Electronic Structure ◽  
Charge Transfer ◽  
Synchrotron Radiation ◽  
Photoelectron Spectroscopy ◽  
Molecular Beam ◽  
Experimental Studies ◽  
Surface States ◽  
Li Adsorption ◽  
Semiconductor Character

The results of experimental studies of the electronic and photoemission properties of an epitaxial GaN layer grown on a SiC/Si(111) substrate by plasma assisted molecular beam epitaxy are presented. The electronic structure of the GaN surface and ultrathin Li/GaN interface was first studied in situ under ultrahigh vacuum conditions under different Li coverages. The experiments were performed using photoelectron spectroscopy with synchrotron radiation in the photon energy range of 75–850 eV. The photoemission spectra in the region of the valence band and surface states and the photoemission spectra from the N 1s, Ga 3d, Li 2s core levels were studied for different submonolayer Li coverages. It is established that Li adsorption causes significant changes in the general form of the spectra induced by charge transfer between the Li layer and the lower N and Ga layers. It is established that the GaN surface has predominantly N-polarity. The semiconductor character of the Li / GaN interface is shown.

Sign in / Sign up

Export Citation Format

Share Document