A. M. Yafyasov

Field and explosive emissions from graphene-like structures

It was shown earlier that the excitation threshold of electron emission from carbon nanoclusters is extremely low (two to three orders of magnitude lower than for metals and semiconductors). In this work, this effect is confirmed by direct experiments with graphene and graphene-like structures. A new model explaining this effect by resonance tunneling due to size quantization is suggested. A low-threshold explosive emission is discovered.

Scattering on a Compact Domain with Few Semi‐Infinite Wires Attached: Resonance Case

A Scattering problem is studied for Neumann Laplacian with a continuous potential on a domain with a smooth boundary and few semi-infinite wires attached to it at the points of contact on the boundary. In resonance case when the frequency of the incoming waves in the wires coincides with some resonance frequency of the domain the approximate formula for the transmission coefficient from one wire to another is derived: in the case of weak interaction between the domain and the wires the transmission coefficient is proportional to the product of values of the corresponding resonance eigenfunction of inner problem at the corresponding points of contact.

ALD synthesis of SnSe layers and nanostructures

Growth of SnSe structures by the ALD method using Et4Sn and H2Se as precursors has been investigated. It was established that coverage occurs at a temperature above 250 °C and the morphology of the layer depends on the temperature. At 350 °C we have grown sphere-shaped particles 100–200 nm in diameter completely covering the substrate in one monolayer. For samples grown at 450 °C petal-shaped crystal islands were observed. The IR spectrum of SnSe grown at 350 °C shows a small shift (~0.20 eV) of the room-temperature band gap energy.

About Scattering on the Ring

The mathematical model of a simplest quasi-one-dimensional quantum network constructed of relatively narrow waveguides (the width of the waveguide is less than the de Broghlie wavelength of the electron in the material) is developed. This model allows to reduce the problem of calculating the current through the quantum network to the construction of scattered waves for some Schrodinger equation on the corresponding one-dimensional graph. We consider a graph consisting of a compact part and few semiinfinite rays attached to it via some boundary condi-tion depending on a parameter β (analog of the inverse exponential “mass” e -bH of a potential barrier H separating the rays from the compact part of the graph). This parameter regulates the connection between the rays and the compact part. Spectral properties of the Schrodinger operator on this graph are described with a special emphasis on the resonance case when the Fermi level in the rays coincides with one of eigenvalues of the nonperturbed Schrodinger operator on the ring. An explicit expression is obtained for the scattering matrix in the resonance case for weakening connection β → 0 between the rays and the compact part.

Low-threshold field emission from carbon nano-clusters

Detonation carbon materials (DCM) composed of non-equilibrium nano-structures show the low-threshold field emission (LTFE). These materials have forward-looking application especially due to high reproducibility of the LTFE-phenomenon on a surface of emitter, where the emitting centers are homogeneously distributed. In this paper we link the effect of LTFE to the nature of the corresponding wave functions based on the experiment results obtained for DCM by the field effect on electrolytes. As we had shown before DCM had been described by an ultra-relativistic dispersion function with extremely small effective mass of electrons and the size-quantization effect had been observed in DCM at even room temperature. Our results based on emission and electrolyte technics of the field-effect measurements in DCM along with modern observations of the field emission in strong electric fields allowed to propose a new resonance transmission model for LTFE-phenomenon, which is alternative to most widely discussed models based on the field-enhancing factors or barrier-lowering mechanisms.

Self-Consistent Quantum Calculation of Space Charge Region for Accumulation and Inversion Band Bending

A new method of self-consistent quantum calculation of the density of the space charge near the surface of a crystal is carried out for a semiconductor with parabolic dispersion law of bands. The remarkable feature is the solution of the Schrodinger equation for electrons and holes in the energy range, including both bound energy states and the states in the continuum. Voltage-capacitance dependences of MIS structures are calculated.

Rashba splitting in MIS structures HgCdTe

The measured parameters of spin-orbit spectral splitting in HgCdTe-based MIS structures with positive and negative Kane gap Eg are compared with the parameters calculated using the three-and four-band Kane model. The disregard of the finite spin-orbit splitting Δ of the valence band in calculations leads to exaggerated values of Rashba splitting (especially for Eg < 0) even for small ratios |Eg|/Δ, although the subband parameters averaged over two spin branches of the spectrum in the two-, three-, and four-band Kane approximations for the same concentrations are practically identical. In the zero-gap HgCdTe, the measured as well as calculated values are noticeably higher, but the four-band approximation leads to values of splitting for both materials which are 20–40% lower than the experimental value. The inclusion of the interband interaction reduces these discrepancies, but does not eliminate them completely. It is shown that the approximations of the 2D spectrum with spin-orbit splitting linear in quasimomentum, which are conventionally used in the analysis, may lower the effective Rashba parameter by a factor of 2–4.

Quantization of the free charge carriers on InSb at room temperature

Abstract A new method of self-consistent quantum calculation of the density of the space charge near the surface of a crystal is carried out for the semiconductor with nonparabolic (Kane) dispersion law of bands. The remarkable feature is the solution of the Schrodinger equation for electrons and holes in the energy range, including both bound energy states and states in the continuum. Theoretical voltage–capacitance dependence is calculated and coincides with experimental data. The dependence of the electron mass and surface mobility from the value of surface potential are analyzed.

Extremely low threshold of field emission from graphene nanoclusters

Carbon nano-cluster cathodes exhibit a low threshold electron emission, which is 2-3 orders lower than on metals and semiconductors. We confirm the effect by direct experiments with graphene structures. We are suggesting the model based on interference electrons wave function in 2D-space charge region of carbon and Tamms surface states of dangling bonds. This barrier is transparent for electrons at Fermi level due to the resonance.

The Electrophysical Properties of the Surface Layer of the Semiconductor TlBiSe2

The field effect method in electrolytes is used for finding the electrophysical characteristics of the surface and the band parameters in the surface layers of the semiconductor TlBiSe 2 . In this paper the dispersion law and the effective mass of electrons of a conduction band, the concentration of ionized donor impurities, and the energy position of the Fermi level are defined. The experimental and theoretically calculated C(V) characteristics are compared.