scholarly journals Раскрытие энергетической щели в области точки Дирака при осаждении кобальта на поверхность (0001) топологического изолятора BiSbTeSe-=SUB=-2-=/SUB=-

2020 ◽  
Vol 54 (9) ◽  
pp. 859
Author(s):  
А.К. Кавеев ◽  
А.Г Банщиков ◽  
А.Н Терпицкий ◽  
В.А Голяшов ◽  
О.Е Терещенко ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Room Temperature ◽  
Molecular Beam ◽  
Dirac Point ◽  
Surface States ◽  
Energy Band Gap ◽  
Temperature Dependent ◽  
Molecular Beam Epitaxy Method ◽  
Topological Surface ◽  
First Time

It was shown for the first time that Co subnanometer coaverage, being deposited by molecular beam epitaxy method onto the (0001) surface of the BiSbTeSe2 topological insulator at 330 °C, opens an energy band gap in the spectrum of topological surface states in the region of the Dirac point, with a shift in the position of the Dirac point caused by preliminary deposition of the adsorbate at room temperature. The gap band width is 21 +/- 6 meV. Temperature-dependent measurements in the 15-150 K range did not show any width changes.

Incorporation and Optical Activation of Er in Group III-N Materials Grown by Metalorganic Molecular Beam Epitaxy

1997 ◽  
Vol 468 ◽  
Author(s):  
J. D. Mackenzie ◽  
C. R. Abernathy ◽  
S. J. Pearton ◽  
S. M. Donovan ◽  
U. Hömmerich ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Room Temperature ◽  
Molecular Beam ◽  
Temperature Dependent ◽  
Group Iii ◽  
Metalorganic Molecular Beam Epitaxy ◽  
Optical Activation ◽  
First Time ◽  
Temperature Dependent Photoluminescence

ABSTRACTMetalorganic molecular beam epitaxy has been utilized to incorporate Er into AlGaN materials during growth utilizing elemental and metalorganic sources. Room temperature 1.54 μm photoluminescence was observed from AlN:Er and GaN:Er. Photoluminescence from AlN:Er doped during growth using the elemental source was several times more intense than that observed from implanted material. For the first time, strong room temperature 1.54 μm PL was observed in GaN:Er grown on Si. Temperature-dependent photoluminescence experiments indicated the 1.54 μm intensities were reduced to 60% and 40% for AlN:Er and GaN:Er, respectively, between 15 K and 300 K. The low volatility of Er(III) tris (2,2,6,6 - tetramethyl heptanedionate) and temperature limitations imposed by transport considerations limited maximum doping levels to ∼1017 cm-3 indicating that this precursor is unsuitable for UHV.

scholarly journals Experimental Evidence of Topological Surface States in Mg3Bi2 Films Grown by Molecular Beam Epitaxy

2019 ◽  
Vol 36 (11) ◽  
pp. 117303 ◽  
Author(s):  
Tong Zhou ◽  
Xie-Gang Zhu ◽  
Mingyu Tong ◽  
Yun Zhang ◽  
Xue-Bing Luo ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Experimental Evidence ◽  
Molecular Beam ◽  
Surface States ◽  
Topological Surface

Ferromagnetic and Paramagnetic Semiconductors Based upon GaN, AlGaN, and GaP

2001 ◽  
Vol 690 ◽  
Author(s):  
Mark E. Overberg ◽  
Gerald T. Thaler ◽  
Rachel M. Frazier ◽  
Brent P. Gila ◽  
Cammy R. Abernathy ◽  
...  
Keyword(s):  
Room Temperature ◽  
Molecular Beam ◽  
Hysteretic Behavior ◽  
Ferromagnetic Semiconductors ◽  
Temperature Dependent ◽  
Paramagnetic Behavior ◽  
Gas Source ◽  
P Type ◽  
First Time ◽  
Temperature Dependent Magnetization

ABSTRACTEpitaxial growth of the ferromagnetic semiconductors GaMnP:C and GaMnN has been investigated by Gas Source Molecular Beam Epitaxy (GSMBE). GaMnP:C films grown with 9.4% Mn are found to be p-type with hysteretic behavior to room temperature. GaMnN films grown at 700 °C with 2.8% Mn show hysteresis at 300 K, while temperature-dependent magnetization measurements indicate that the magnetism may persist to much higher temperatures (> 325 K). Samples of AlGaMnN have also been prepared for the first time that show improved surface morphology compared to GaMnN but which show only paramagnetic behavior.

scholarly journals Growth of (110) GaAs/GaAs by Molecular Beam Epitaxy

1985 ◽  
Vol 46 ◽  
Author(s):  
L.T. Parechanian ◽  
E.R. Weber ◽  
T.L. Hierl
Keyword(s):  
Molecular Beam Epitaxy ◽  
Substrate Temperature ◽  
Hall Effect ◽  
Room Temperature ◽  
Molecular Beam ◽  
Defect Density ◽  
Temperature Dependent ◽  
Mbe Growth ◽  
Order Of Magnitude ◽  
Hall Effect Measurements

AbstractThe simultaneous molecular beam epitaxy (MBE) growth of (100) and (110) GaAs/GaAsintentionally doped with Si(∼lE16/cm^3) was studied as a function of substrate temperature, arsenic overpressure, and epitaxial growth rate. The films wereanalyzed by scanning electron and optical microscopy, liquid helium photoluminescence (PL), and electronic characterization.For the (110) epitaxal layers, an increase in morphological defect density and degradation of PL signal was observed with a lowering of the substrate temperature from 570C. Capacitance-voltage (CV) and Hall Effect measurements yield room temperature donor concentrations for the (100) films of n∼l5/cm^3 while the (110) layers exhibit electron concentrations of n∼2El7/cm^3. Hall measurements at 77K on the (100) films show the expected mobility enhancement of Si donors, whereas the (110) epi layers become insulating or greatly compensated. This behavior suggests that room temperature conduction in the (110) films is due to a deeper donor partially compensated by an acceptor level whose concentration is of the same order of magnitude as that of any electrically active Si. Temperature dependent Hall effect indicates that the activation energy of the deeper donor level lies ∼290 meV from the conduction band. PL and Hall effect indicate that the better quality (110) material is grown by increasingthe arsenic flux during MBE growth. The nature of the defects involved with the growth process will be discussed.

Photoreflectance Study of Strained InAIAs/InP Structures

1995 ◽  
Vol 379 ◽  
Author(s):  
Jenn-Shyong Hwang ◽  
W. Y. Chou ◽  
S. L. Tyan ◽  
Y. C. Wang ◽  
J. H. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Electric Field ◽  
Fermi Level ◽  
Layer Thickness ◽  
Surface Potential ◽  
Molecular Beam ◽  
Surface States ◽  
Energy Band Gap ◽  
Characteristic Region ◽  
Surface Fermi Level

ABSTRACTWe have studied the photoreflectance spectra at 300 K from a series of strained In1−xAlxAs/InP (0.42<x<0.57) strained structures grown by molecular beam epitaxy. From the observed Franz-Keldysh Oscillation we evaluate the built-in de electric field and hence the surface potential under different strain. We found that the surface Fermi level is not pinned at midgap under different strainwhich results in contrast to AIGaAs and GaAs. In addition, from the observed dependence of the built-in electric field Fdc and surface potential barrier Vm on the top layer thickness, we conclude that the surface states are distributed over two separate regions within the energy band gap under different strain and the densities of the surface states are as low as (2,71α0.05)x 1011 cm−2 for the distribution near the conduction band and (4.29α0.05)x1011 cm-2 for the distribution near the valence band. The Fermi level is weakly pinned while the top layer thickness is within the characteristic region of each sample.

Phosphorus-Vacancy-Related Deep Levels in Gainp Layers Grown by Molecular Beam Epitaxy

1993 ◽  
Vol 325 ◽  
Author(s):  
Z.C. Huang ◽  
C.R. Wie ◽  
J.A. Varriano ◽  
M.W. Koch ◽  
G.W. Wicks
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Deep Levels ◽  
Electron Trap ◽  
Material System ◽  
Temperature Dependent ◽  
Illumination Time ◽  
Electric Effect ◽  
First Time ◽  
Lattice Matched

AbstractDeep levels in lattice matched Ga0.51In0.49P/GaAs heterostructure have been investigated by thermal-electric effect spectroscopy(TEES) and temperature dependent conductivity measurements. Four samples were grown by molecular beam epitaxy with various phosphorus (P2) beam equivalent pressure(BEP) of 0.125, 0.5, 2, and 4×10−4 Torr. We report for the first time, to our knowledge, an electrical observation of phosphorus vacancy point defects in the GaInP/GaAs material system. The phosphorus vacancies, Vp. behave as an electron trap which is located at EC−0.28±0.02 eV. We have found that this trap dominates the conduction band conduction when T> 220K, and is responsible for the variable-range hopping conduction when T < 220K. Its concentration decreases with the increasing phosphrous BEP. Successive rapid thermal annealing showed that its concentration increases with the increasing annealing temperature. Another electron trap at EC−0.51eV was also observed only in samples with P2 BEP less than 2×10−4 Torr. Its capture cross section is 4.5×10−15 cm 2 as obtained from the illumination time dependent TEES spectra.

Electrical transport properties of cerium doped Bi2Te3 thin films grown by molecular beam epitaxy

2021 ◽  
Vol 42 (12) ◽  
pp. 122902
Author(s):  
Peng Teng ◽  
Tong Zhou ◽  
Yonghuan Wang ◽  
Ke Zhao ◽  
Xiegang Zhu ◽  
...  
Keyword(s):  
Thin Films ◽  
Molecular Beam Epitaxy ◽  
Electrical Transport ◽  
Kondo Effect ◽  
Molecular Beam ◽  
Magnetic Moments ◽  
Surface States ◽  
Electrical Transport Properties ◽  
Doping Effects ◽  
Topological Surface

Abstract Introducing magnetism into topological insulators (TIs) can tune the topological surface states and produce exotic physical effects. Rare earth elements are considered as important dopant candidates, due to their large magnetic moments from heavily shielded 4f electrons. As the first element with just one 4f electron, cerium (Ce) offers an ideal platform for exploring the doping effect of f-electron in TIs. Here in this work, we have grown cerium-doped topological insulator Bi2Te3 thin films on an Al2O3(0001) substrate by molecular beam epitaxy (MBE). Electronic transport measurements revealed the Kondo effect, weak anti-localization (WAL) effect and suppression of surface conducting channels by Ce doping. Our research shows the fundamental doping effects of Ce in Bi2Te3 thin films, and demonstrates that such a system could be a good platform for further research.

Temperature Dependence of Optical Properties of AlAs, Studied by In Situ Spectroscopic Ellipsometry

1992 ◽  
Vol 242 ◽  
Author(s):  
Huade Yao ◽  
Paul G. Snyder ◽  
Kathleen Stair ◽  
Thomas Bird
Keyword(s):  
Optical Properties ◽  
Molecular Beam Epitaxy ◽  
Room Temperature ◽  
Optical Constants ◽  
Molecular Beam ◽  
Gaas Layer ◽  
Temperature Dependent ◽  
Harmonic Oscillator Approximation ◽  
Quantitative Analyses

ABSTRACTThe dielectric functions ε = ε1+iε2 of AlAs were determined from 1.5 eV to 5.0 eV, by spectroscopie ellipsometry (SE), from room temperature (RT) to ∼577 °C in an ultrahigh vacuum (UHV) chamber. Molecular beam epitaxy (MBE)-grown AlAs was covered by a thin GaAs layer, which was passivated by arsenic capping to prevent oxidation. The arsenic cap was desorbed inside the UHV chamber. SE measurements of the unoxidized sample were made, at various temperatures. Temperature dependent optical constants of AlAs were obtained by mathematically removing the effects of the GaAs cap and substrate. Quantitative analyses of the variations of critical-point energies with temperature, by using the harmonic oscillator approximation (HOA), indicate that the E1 and E1+Δ1 energies decrease -350 meV as temperature increases from RT to 500 °C.

scholarly journals Discovery of a weak topological insulating state and van Hove singularity in triclinic RhBi2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kyungchan Lee ◽  
Gunnar F. Lange ◽  
Lin-Lin Wang ◽  
Brinda Kuthanazhi ◽  
Thaís V. Trevisan ◽  
...  
Keyword(s):  
Time Reversal ◽  
Topological Insulators ◽  
Dirac Point ◽  
Saddle Points ◽  
Surface States ◽  
Van Hove Singularity ◽  
Space Group ◽  
Topological Materials ◽  
Topological Surface ◽  
Optimal Space

AbstractTime reversal symmetric (TRS) invariant topological insulators (TIs) fullfil a paradigmatic role in the field of topological materials, standing at the origin of its development. Apart from TRS protected strong TIs, it was realized early on that more confounding weak topological insulators (WTI) exist. WTIs depend on translational symmetry and exhibit topological surface states only in certain directions making it significantly more difficult to match the experimental success of strong TIs. We here report on the discovery of a WTI state in RhBi2 that belongs to the optimal space group P$$\bar{1}$$ 1 ¯ , which is the only space group where symmetry indicated eigenvalues enumerate all possible invariants due to absence of additional constraining crystalline symmetries. Our ARPES, DFT calculations, and effective model reveal topological surface states with saddle points that are located in the vicinity of a Dirac point resulting in a van Hove singularity (VHS) along the (100) direction close to the Fermi energy (EF). Due to the combination of exotic features, this material offers great potential as a material platform for novel quantum effects.

scholarly journals 2D weak anti-localization in thin films of the topological semimetal Pd$$_{3}$$Bi$$_{2}$$S$$_{2}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shama ◽  
R. K. Gopal ◽  
Goutam Sheet ◽  
Yogesh Singh
Keyword(s):  
Thin Films ◽  
Phonon Scattering ◽  
Surface States ◽  
Relaxation Mechanism ◽  
Transport Studies ◽  
Bulk Carriers ◽  
Topological Semimetal ◽  
Topological Surface ◽  
First Time ◽  
Electron Phonon Scattering

AbstractPd$$_{3}$$ 3 Bi$$_{2}$$ 2 S$$_{2}$$ 2 (PBS) is a recently proposed topological semimetal candidate. However, evidence for topological surface states have not yet been revealed in transport measurements due to the large mobility of bulk carriers. We report the growth and magneto-transport studies of PBS thin films where the mobility of the bulk carriers is reduced by two orders of magnitude, revealing for the first time, contributions from the 2-dimensional (2D) topological surface states in the observation of the 2D weak anti-localization (WAL) effect in magnetic field and angle dependent conductivity measurements. The magnetotransport data is analysed within the 2D Hikami-Larkin-Nagaoka (HLN) theory. The analysis suggests that multiple conduction channels contribute to the transport. It is also found that the temperature dependence of the dephasing length can’t be explained only by electron-electron scattering and that electron-phonon scattering also contributes to the phase relaxation mechanism in PBS films.

Sign in / Sign up

Export Citation Format

Share Document