A mechanism of transverse charge transfer through hexagonal boron nitride (h-BN) in a MIS structure has been studied. Experimental data for charge transfer have been analyzed in terms of different ...models of charge transfer in insulators. It has been shown that charge transfer in h-BN is described by the model of phonon-assisted tunneling between neutral traps. The thermal and optical energies of phonon-coupled traps in h-BN have been determined. Based on charge transfer measurements, XPS spectra, and the ab initio electronic structure of intrinsic defects in h-BN it has been found that boron–nitrogen divacancies are most probably responsible for charge transfer in h-BN and transfer is provided by electrons.
Titanium dioxide (anatase, a-TiO
2
) films have been prepared by electron beam sputtering of a TiO
2
target in reactive atmosphere and their structural, microstructural, and optical properties were ...evaluated by reflection high- energy electron diffraction (RHEED) and x-ray diffraction (XRD) analyses, atomic force microscopy (AFM), and spectroscopic ellipsometry (SE). Different reflection models for determination of film optical parameters were tested and compared. The dispersive optical parameters were defined using the Tauc–Lorentz model by SE in the photon energy range of
E
= 1.12–4.96 eV. The films were transparent at
E
< 3 eV, but noticeable absorption was detected at
E
> 3 eV. The bandgap was estimated at the level of
E
g
≈ 3.44 eV.
One of the most important issues during the selection of low-
k
dielectrics is related to their intrinsic properties including their electric breakdown and leakage current that are predominantly ...determined by conduction mechanisms. This study is devoted to elucidating the charge transport mechanism in the SiOCH low-
k
dielectric films fabricated by plasma-enhanced chemical vapor deposition. By analyzing four bulk-limited models of the charge transport it was found that only the Nasyrov–Gritsenko model of phonon-assisted electron tunneling between neutral traps describes the experimental
I
–
V
–
T
characteristics with all the fitting parameters with reasonable physical values. The obtained thermal trap energy value 1.2 eV is confirmed independently by photoluminescence spectroscopy data analysis. The trap nature and comparison of the obtained results with the corresponding data for low-
k
films with similar chemical composition and deposited by the spin-on-glass technology using self-assembling chemistry is discussed. It is hypothesized that the defect with ionization energy of 1.2 eV is the oxygen divacancy.
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•We calculate XPS and absorption spectra for crystalline HfO2 in frame of hybrid DFT.•We got the experimental XPS for bombarding with Ar-ions hafnia and HfOx.•Oxygen vacancies in HfO2 ...produce the defect states at 3.0eV above the valence band.•Ar+ ion bombardment of HfO2 produces the oxygen vacancies and polyvacancies.•Absorption peak at 3.0–4.5eV for HfO2 is attributed to the oxygen vacancy.
The electronic structure of oxygen vacancies and polyvacancies in HfO2 was studied theoretically from the first-principles calculations and experimentally, by X-ray photoelectron spectroscopy. The electronic structure calculations of crystalline HfO2 were performed within the hybrid density functional theory. The experimental photoelectron spectra indicate that both nonstoichiometric chemistry and Ar-ion bombardment of hafnia films lead to the generation of the defect states at 3.0eV above the valence band. According to the calculations, these defect states are attributed to the oxygen vacancies.
It is shown that the treatment of stoichiometric HfO
2
, which is synthesized by atomic layer deposition, in electron cyclotron resonance hydrogen plasma leads to a significant depletion of the film ...in oxygen and the formation of nonstoichiometric HfO
x
(
). The longer the treatment time, the higher the degree of oxygen depletion. The charge transfer in the films under study occurs by phonon-assisted tunneling between oxygen vacancies serving as traps. It has been found that the
-Si/HfO
x
/Ni structures, where the oxide layer is treated in the electron cyclotron resonance hydrogen plasma, have memristor properties: they are reversibly switched between high and low resistance states. The fabricated memristor structures are forming-free.
Broad photoluminescence (PL) band at 2.97eV excited in the band near 6.0eV in amorphous chemical vapor deposition films is related to the neutral oxygen vacancy by analogy with crystalline Al2O3. The ...identification of this PL band was supported by the results of first-principle quantum chemical simulation, which showed 6.3 and 6.4eV bands in the extinction spectra for alpha - and gamma -Al2O3, respectively. Other PL bands are attributed to ionized single vacancies (F+-centers), divacancies (F2) and, probably, interstitial Al.
The influence of temperature fluctuations of the reference section of an optical fiber as part of the instrumental part on the absolute measurement error of a distributed fiber-optical temperature ...sensor was performed. The design of the reference section with active temperature control with high stability as part of the instrumental part of the sensor is proposed and experimentally investigated. The efficiency of using active temperature control to improve the repeatability of measurements and reduce the measurement error has been experimentally demonstrated.
The sensitivity of the Sagnac interferometer for various acoustic influence coordinates was studied. The principles of the formation of a dead zone in an acoustic distributed fiber-optic sensor based ...on the Sagnac interferometer have been obtained and experimentally confirmed. The response of the interferometer was studied for different types of acoustic impact on the circuit: in the form of a rectangular pulse, sinusoidal, and in the form of a periodic triangular function. The nature of the change in the phase difference at the output of the Sagnac interferometer for each of them was studied. With the found value of the typical frequency
= 10.8 kHz and a loop length of 20 km, numerical simulation and experimental study of the amplitude of the phase difference under acoustic impact through each 1 km of the loop in the range from 0 to 10 km were carried out. A dead zone elimination method is proposed for integrating the Sagnac interferometer into a complex monitoring system using a phase-sensitive optical time domain reflectometer.
Thin films of La-doped hafnium oxide synthesized by plasma-enhanced atomic layer deposition with subsequent rapid annealing have been studied. It has been found that the films under study have an ...orthorhombic noncentrosymmetric structure with the space group
Pmn2
1
. It has been shown that these films have ferroelectric properties. The ratio of atomic concentrations of elements in a film has been determined. It has been found that the film consists of the mixture of the HfO
2
and La
2
O
3
phases. It has been shown that argon ion etching results in the generation of oxygen vacancies with a concentration of about 1 at % in the surface region of the films. Vacancies are formed primarily through the knock-out of oxygen atoms to interstitial positions with the formation of a Frenkel pair.
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