This work was devoted to studying the atomic structure and electron spectrum of a-SiO.sub.x : H films created on silicon and glass substrates by means of plasma-enhanced chemical vapor deposition ...(PECVD). Depending on the conditions of oxygen supply into the reactor, the stoichiometric parameter x of the films was varied from 0.57 to 2. The structure of the films and the specific features of their electron structure were characterized depending on the parameter x with a complex of structural and optical methods and ab initio quantum-chemical simulation for the model SiO.sub.x structure. The studied SiO.sub.x : H films were established to consist predominantly of silicon suboxides SiO.sub.y, SiO.sub.2 clusters, and amorphous silicon. Based on the spatial fluctuations of their chemical composition, the model of bandgap width and potential fluctuations was proposed for SiO.sub.x electrons and holes. The obtained data would provide the charge transport in a-SiO.sub.x : H films with more precise modeling important for the creation of nonvolatile random-access memory (RAM) elements and memristors on their basis.
The optical properties of amorphous nonstoichiometric silicon oxide (SiOx) films of variable composition (x = 0.62–1.92) formed by plasma-enhanced chemical vapor deposition are studied in the ...spectral range of 1.12–4.96 eV. Spectral ellipsometry showed that the refractive index dispersion character allows one to assign the formed SiOx films to silicon-like films, dielectrics, or intermediate-conductivity-type films depending on the content of oxygen in the gas phase during synthesis. A model of the SiOx structure for ab initio calculations is proposed and describes well the experimental optical spectra. Ab initio calculations of the dependences of the SiOx refractive index and band gap on stoichiometry parameter x are performed.
The charge transport mechanism in thin amorphous and ferroelectric Hf
0.5
Zr
0.5
O
2
films has been studied. It has been shown that the transport mechanism in studied materials does not depend on the ...crystal phase and is phonon-assisted tunneling between traps. The comparison of the experimental current–voltage characteristics of TiN/Hf
0.5
Zr
0.5
O
2
/Pt structures with the calculated ones provides the trap parameters: thermal energy of 1.25 eV and the optical energy of 2.5 eV. The trap concentration has been estimated as ~10
19
–10
20
cm
–3
.
The atomic and electronic structures of metal-rich noncentrosymmetric zirconium oxide synthesized by the ion beam sputtering of a metallic target in an oxygen atmosphere has been studied by X-ray ...photoelectron spectroscopy, Raman scattering, spectral ellipsometry, and quantum-chemical simulation. It has been established that ZrOx < 2 consists of ZrO2, metallic Zr, and zirconium suboxides ZrOy. The stoichiometry parameter of ZrOy has been estimated. It has been shown that the optical properties of ZrOx < 2 are determined by metallic Zr. A model of fluctuation of the width of the band gap and a potential for electrons and holes in ZrOx < 2 based on spatial fluctuations of the chemical composition has been proposed.
Optical properties of amorphous nonstoichiometric tantalum-oxide films of variable composition (TaO
x
,
x
= 1.94–2.51) in the spectral range of 1.12–4.96 eV, obtained by ion-beam ...sputtering-deposition of metallic tantalum at different partial oxygen pressures (0.53–9.09 × 10
–3
Pa), have been investigated. It is shown by spectral ellipsometry that the character of dispersion of the absorption coefficient and refractive index in TaO
x
of variable composition suggests that light-absorbing films with dispersion similar to that in metals are formed at oxygen pressures in the growth chamber below 2.21 × 10
–3
Pa, whereas transparent films with dielectric dispersion are formed at pressures above 2.81 × 10
–3
Pa. According to the data of quantumchemical simulation, the absorption peak at a photon energy of 4.6 eV in TaO
x
observed in the absorptioncoefficient dispersion spectrum is due to oxygen vacancy. The peak in the Raman-scattering spectra of TaO
x
films with metallic dispersion at frequencies of 200–230 cm
–1
is presumably related to tantalum nanoclusters.
Synaptosomal protein SNAP-25 is involved in the process of transmitting nerve spikes in the CNS and in the consolidation of memory traces in the hippocampus. Two independent studies have demonstrated ...associations between SNAP-25 gene polymorphisms and intellectual functions in a group of mentally healthy subjects and patients with schizophrenia. The aim of the present work was to perform a comparative study of the association between the MnlI polymorphism of SNAP-25 and cognitive functions (verbal memory, attention/executive functions) in 66 patients with endogenous psychoses, 75 of their mentally healthy relatives, and 136 healthy control subjects. Statistical analysis showed that the effectiveness of performing cognitive tests was significantly affected by group assignment (
p
= 0.00001) and genotype (
p
= 0.012). The interaction between genotype and group assignment also had an influence (
p
= 0.02). In all groups, carriers of the TT genotype had worse measures than carriers of other genotypes. The similar nature of the influences of the MnlI polymorphism on variations in measures in all groups indicates that this gene is related to overall intellect.
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► The electronic and optical properties of HfO
2 polymorphs calculated with hybrid DFT. ► The effective electron and hole masses and dielectric properties were calculated. ► Oxygen ...vacancy in HfO
2 polymorphs can be both electron and hole trap. ► The calculated findings can be used in carrier transport simulations hereafter.
The band structure, dielectric constants and linear optical properties of the cubic, tetragonal and monoclinic HfO
2 were calculated within density functional methods. The calculation were performed with both standard and hybrid density functionals which accurately reproduce the experimental band gaps. Electronic structures of hafnia polymorphs with oxygen vacancies were investigated. It was found out, that oxygen vacancy can be both electron and hole trap in HfO
2.
We studied the relationship between
DRD5
gene polymorphism presented by microsatellites with cognitive signs in 152 schizophrenic patients, 81 mentally healthy relatives, and 125 mentally healthy ...control individuals. An association was found between
DRD5
polymorphism with efficiency of visual voluntary attention in patients (
p
=0.02) and their relatives (
p
=0.006). Carriers of two copies of the 148-b.p. allele were characterized by low efficiency of attention.
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