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I. A. Stepanov

Publications and source records attributed to I. A. Stepanov.

14 recordsLinked to original sources
arXiv2026

Investigation of tantalum films growth for coplanar resonators with internal quality factors above ten million

Alpha-tantalum on silicon is a promising platform for high-coherence superconducting quantum circuits. However, the growth mechanism of alpha-tantalum on silicon remains poorly understood. We present a comprehensive study on alpha-tantalum films growth on various substrate. The decisive role of a substrate material Debye temperature on phase selection mechanism in tantalum films growth is experimentally confirmed, contradicting the prior assumptions on substrate temperature influence. Crucially, we confirm that alpha-tantalum starts growing only after a 7-10 nm thick beta-tantalum underlayer. It results in ranging the critical temperature of α-Ta films from 3.77 K to 4.39 K for the total thickness from 20 to 150 nm, respectively. Finally, we compared high-quality Al and Ta coplanar resonators on silicon, demonstrating compact tantalum resonators (4/10.5/4 um) with an internal quality factor exceeding 10 million at single-photon excitation powers.

quant-ph↗
arXiv2025

Mutual control of critical temperature, residual resistance ratio, stress, and roughness for sputtered Nb films

Superconducting single quantum logic integrated circuits traditionally exploit magnetron sputtered niobium thin films on silicon oxide substrates. The sputtering depends on multiple process parameters, which dramatically affect mechanical, electrical, and cryogenic properties of Nb thin films. In this work, we focus on the comprehensive relationship study between 200-nm Nb film characteristics and their intrinsic stress. It is shown that there is a critical value of the working pressure pcritical at the fixed sputtering power above which stress in the film relaxes whereas the film properties degrade significantly. Below pcritical one can control intrinsic stress in the wide range from -400 MPa to +600 MPa maintaining perfect film surface with a 0.8 nm roughness (Rq), electrical resistivity less than 20 uOhm*cm, critical superconducting transition temperature above 8.9 K and residual resistance ratio over 6.4. We suggest a modified kinetic model to predict Nb films stress with the linear dependence of high-energy parameters on the working pressure replaced with an exponential one, which allowed reduction of the approximation error from 20 to 8%.

cond-mat.mtrl-sci↗
arXiv2008

The Wave Vector is Limited from Below

It is shown that the electron wave vector in a crystal cannot be smaller than a certain value. As a result, in a crystal there are many first Brillouin zones, and not only one as it had been supposed earlier. In crystal there can be many electrons with the same wave vector, and not only two as it had been supposed earlier. These electrons must be at sufficiently large distances from each other. An attempt is made to explain the decrease of electric and thermal conductivity with decreasing crystal size.

physics.gen-ph↗
arXiv2006

Dependence of the Energy of Molecules on Interatomic Distance at Large Distances

Earlier it has been supposed that energy of molecules depends on interatomic distance according to the curve 1, Fig. 1. However, dissociation of molecules (for example, Te2=2Te) often is a chemical reaction. According to chemical kinetics, chemical reactions overcome a potential barrier. This barrier is absent at the curve 1. It is a very strong argument against the curve 1. It is shown that the molecule energy dependence on interatomic distance can behave at large distances not so but like the curve 2, Fig. 1. Earlier it has been supposed that quantum chemical methods give a wrong result at big distances if the wave function does not turn to zero. In this paper, it is been shown that it must not turn to zero. The wave function can be a piecewise function.

physics.gen-ph↗
arXiv2003

Supercooled Water: Contradiction to Thermodynamics

It has been shown that the dependence of thermal expansion coefficient and of the isobaric heat capacity of supercooled water on the temperature contradicts to an important thermodynamic relation. Keywords: Supercooled water, Negative thermal expansion, The 1st law of thermodynamics, Anomalous behaviour of heat capacity.

physics.gen-ph↗
arXiv2002

Thermodynamics of Substances with Negative Thermal Expansion Coefficient

The 1st law of thermodynamics for heat exchange is dQ=dU+PdV. According to K. Martinas etc., J. Non-Equil. Thermod. 23 (4), 351-375 (1988), for substances with negative thermal expansion coefficient, P in this law is negative. In the present paper it has been shown that P for such substances is positive but the sign before P must be minus not plus: dQ=dU-PdV.

physics.gen-ph↗
arXiv2002

Paradoxes of Thermal Expansion

It is shown that the dependence of negative thermal expansion coefficient of many substances on the temperature contradicts to an important thermodynamic relation. It is supposed that there are oscillations at the Cp(T) and alpha(T) curves at alpha>0 and they are in reverse phases.

physics.gen-ph↗
arXiv2001

The Heats of Reactions. Calorimetry and Van't-Hoff. 3

Earlier, the author found that for the biggest part of chemical reactions the law of conservation of energy must have the following form: dU=dQ+PdV+SUM. In the present paper this result is confirmed by other experiments.

physics.gen-ph↗
arXiv2000

The Heats of Reactions. Calorimetry and Van't-Hoff. 2

Earlier, the author found that for the biggest part of chemical reactions the law of conservation of energy must have the following form: dU=dQ+PdV+SUM In the present paper this result is confirmed by other experiments.

physics.gen-ph↗
arXiv2000

The 1st Law of Thermodynamics in Chemical Reactions

In the previous papers of the author it has been shown that the 1st law of thermodynamics in chemical reactions is the following one: dU=dQ+PdV+SUM In the present paper this theory was developed and it has been shown that the 1st law of thermodynamics in chemical reactions has the following form: dC=-dU+dA and -dU=dQ where dC is the change in the chemical energy, dU is the change in the internal energy. Internal energy is the energy of thermal motion of molecules.

physics.gen-ph↗
arXiv2000

The Heats of Dilution. Calorimetry and Van't-Hoff

Earlier it has been found that there is a big difference between heats of dilution measured by calorimetry and by the Van't-Hoff equation. In the present paper a reason for that is proposed. Experimental data for dilution of benzene and n-hexane in water were used.

physics.chem-ph↗
arXiv2000

The Heats of Reactions. Calorimetry and Van't-Hoff. 1

It has been supposed that the law of conservation of energy in chemical reactions has the following form: dU=dQ-PdV+SUM Earlier the author has shown that for the biggest part of reactions it must have the following form: dU=dQ+PdV+SUM In the present paper this result is confirmed by other experiments.

physics.gen-ph↗
arXiv2000

The Law of Conservation of Energy in Chemical Reactions

Earlier it has been supposed that the law of conservation of energy in chemical reactions has the following form: DU=DQ-PDV+SUM(muiDN) In the present paper it has been proved by means of the theory of ordinary differential equations that in the biggest part of the chemical reactions it must have the following form: DU=DQ+PDV+SUM(muiDN) The result obtained allows to explain a paradox in chemical thermodynamics: the heat of chemical processes measured by calorimetry and by the Vant-Hoff equation differs very much from each other. The result is confirmed by many experiments.

physics.chem-ph↗