The paper highlights that research in the field of agricultural physics in this country began in the 1930s and is closely linked to the renowned physicist Abram Fedorovich Ioffe. Under his leadership, the world’s first Agrophysical Research Institute was established in 1932. A.F. Ioffe directed this institute from 1932 to 1942 and from 1954 to 1959. These periods are particularly noteworthy in terms of the scientist’s contributions to formulating and executing the institute’s objectives. (Research purpose) The paper aims to examine A.F. Ioffe’s role in the development of agrophysical science during his tenure as the director of the Agrophysical Institute from 1954 to 1959. (Materials and methods) The research is grounded in the analysis of archival materials, reports detailing research activities of the Agrophysical Research Institute, publications, and A.F. Ioffe’s engagements from 1932 to 1959. The study explores the role of physics in shaping and refining methods within domestic agricultural production. The paper presents the outcomes of theoretical and applied research conducted under the guidance of A.F. Ioffe, particularly focusing on the development of measuring instruments for integration into control systems within industrial agricultural production. (Results and discussion) It was revealed that during A.F. Ioffe’s leadership periods, the methodology of an «electronic agronomist» was developed, marking a global pioneering achievement. The paper shows the integration of advanced physics achievements into agriculture, and highlights the use of semiconductor devices to monitor the physical and chemical parameters of the soil, as well as external factors affecting crop life. (Conclusions) The paper underscores the pivotal role played by the scientist and organizer A.F. Ioffe during the emergence and development of domestic agronomic physics. It points out the primary directions of agrophysical work and the results achieved directly under the leadership of A.F. Ioffe. The paper also sheds light on their contribution to developing the main research directions in the field of agronomic physics, which continue to be pertinent in modern conditions.

This work is devoted to the determination of the mechanisms of generation, transfer, and recombination of charge carriers in a hybrid organic–inorganic system—a polymer poly-3-hexylthiophene with silicon nanoparticles ( nc -Si). It is shown that by varying the nc -Si concentration, it is possible to change the conductivity and photoconductivity of such a system within a fairly wide range, achieving optimal values for applications in optoelectronics (photodetectors, solar cells, etc.). A model is proposed making it possible to describe the photoelectric properties of poly-3-hexylthiophene modified with nc -Si from a single point of view. The model assumes a Gaussian distribution of the density of electronic states along which the hopping transport of charge carriers occurs. The influence of nc -Si mainly affects the parameters of the Gaussian distribution of the density of electronic states and the position of the Fermi level.

The spectral dependence of current sensitivity and kinetics of photoconductivity and the increase and decrease of photoresistances based on a composite of poly(3-hexylthiophene) polymer and silicon nanoparticles have been investigated. It has been found that the introduction of silicon nanoparticles makes it possible to vary both the spectral operating range and current sensitivity of photo-resistances based on the poly(3-hexylthiophene) polymer composite within a wide range. At the same time, the time characteristics of the photoresistance investigated in this work are not inferior to conventional photodetectors based on P3HT/fullerene.

The influence of grain size on the sensitivity of indium oxide with extremely small grains in range of 7–40 nm to nitrogen dioxide in low concentration at room temperature is investigated under the UV illumination. It is found that the sample with the intermediate size of nanocrystals shows the greatest response to nitrogen dioxide. The possibility of using nanocrystalline In2O3 to create a sensor for detecting NO2 in air at room temperature under UV illumination is demonstrated. It is shown that pulsed illumination may be used for NO2 detection at room temperature that significantly reduces the sensor power consumption.

The effect of the nanocrystal size on the sensitivity of nanocrystalline indium oxide In2O3 with an extremely small size of nanocrystals (from 7 to 40 nm) synthesized by the sol-gel method to nitrogen dioxide with low concentrations is investigated at room temperature under ultraviolet (UV) illumination and without it. It is found that the greatest response to nitrogen dioxide is demonstrated by a sample with an intermediate nanocrystal size. The possibility of using nanocrystalline In2O3 for fabricating sensors for detecting NO2 in air at room temperature under conditions of additional UV illumination is demonstrated. It is shown that such a sensor can also operate under conditions of pulsed illumination, which significantly reduces its power consumption.

The distribution of the potential and the parameters of the potential barrier for electrons in semiconductor crystallite is numerically calculated. The calculations are made in a spherical crystallite with uniformly distributed surface states and uniformly distributed donors. It is considered in the calculations that the surface charge is screened both by the ionized donors and on free electrons; the contibution of free electrons should not be neglected in semiconductors with a high concentration of free electrons. It is demonstrated that the height of the potential barrier depends non-monotonically on the concentration of the donors in the crystallite. Moreover, in the curve of the height of the potential barrier as a function of the concentration of the donors, it is possible to highlight two segments corresponding to the cases of the complete and partial depletion of the crystallite. The height of the potential barrier increases with the concentration of the donors in the first segment and decreases in the second segment. It is established that the height of the potential barrier increases with the increase in the concentration of the surface states. The possibility of the existence of surface potential barriers in nano- and polycrystalline metal-oxide semiconductors, which are applied as a sensitive layer of gas sensors, is estimated. It is concluded that if the crystallite radius in metal-oxide semiconductors does not exceed 10 nm the sensor’s sensitivity to gas could hardly be attributed to the usual barrier model. It is demonstrated that shape of crystallite and the contribution of free electrons to screening of surface charge have to be taken into account to calculation of width of potential barrier.

The distribution of potential and parameters of potential barrier in semiconductor crystallite was calculated numerically. The calculation was carried out in spherical crystallite with evenly distributed donors and surface states. The calculation assumed that the surface charge is screened by both ionized donors and free electrons, the contribution of which cannot be neglected in semiconductors with high concentration of free electrons. The height of potential barrier is shown to nonmonotonically depend on the concentration of donors. The dependence of height of potential barrier on the concentration of donors may be divided into two part. One part of dependence describes the fully depleted crystallite and the second part describes the party depleted crystallite. On the first part the height of potential barrier increases with the donor concentration but on the second part the height of potential barrier decreases. The height of the potential barrier increases with increasing of concentration of surface states. The possibility of existing of potential barriers is estimated in nano− and polycrystalline metal oxide semiconductors used as sensitive layers of gas sensors. It is concluded that if the radius of crystal grains in metal oxide semiconductors does not exceed 10 nm, the explanation of the sensitivity of the sensor to gas by using a commonly barrier model seems unlikely. It is demonstrated that shape of crystallite and the contribution of free electrons to screening of surface charge have to be taken into account to calculation of width of potential barrier.

We study the carrier transport mechanisms in the layers of mesoporous silicon for carrier transport along the layer surface (perpendicular to silicon columns) and perpendicular to the layer surface (along silicon columns). It is established that the conductivity measured along the layer surface is much lower than the conductivity measured perpendicular to the surface. The analysis of the temperature and frequency dependences of the conductivity lead to a conclusion that there are various carrier transport mechanisms in the cases considered.

The distribution of potential and parameters of potential barrier in semiconductor crystallite was calculated numerically. The calculation was carried out in spherical crystallite with evenly distributed donors and surface states. The calculation assumed that the surface charge is screened by both ionized donors and free electrons, the contribution of which cannot be neglected in semiconductors with high concentration of free electrons. The height of potential barrier is shown to nonmonotonically depend on the concentration of donors. The dependence of height of potential barrier on the concentration of donors may be divided into two part. One part of dependence describes the fully depleted crystallite and the second part describes the party depleted crystallite. On the first part the height of potential barrier increases with the donor concentration but on the second part the height of potential barrier decreases. The height of the potential barrier increases with increasing of concentration of surface states. The possibility of existing of potential barriers is estimated in nano− and polycrystalline metal oxide semiconductors used as sensitive layers of gas sensors. It is concluded that if the radius of crystal grains in metal oxide semiconductors does not exceed 10 nm, the explanation of the sensitivity of the sensor to gas by using a commonly barrier model seems unlikely. It is demonstrated that shape of crystallite and the contribution of free electrons to screening of surface charge have to be taken into account to calculation of width of potential barrier.

An investigation into carrier-transport mechanisms in mesoporous silicon layers for the cases of transport along the layer surface (perpendicularly to silicon columns) and perpendicularly to the layer surface (along silicon columns) is presented. It is established that the conductivity measured along the layer surface is much lower than the conductivity measured perpendicularly to the surface. It is concluded from analysis of the temperature and frequency dependences of the conductivity that the carrier-transport mechanisms are different in the cases under consideration (along and perpendicularly to the surface).

Nanocrystalline indium oxide films with extremely small grains in range of 7–40 nm are prepared by sol-gel method. The influence of grain size on the sensitivity of indium oxide to nitrogen dioxide in low concentration at room temperature is investigated under the UV illumination and without illumination. The sensitivity increases with the decrease of grain sizes when In2O3 is illuminated while in the dark In2O3 with intermediate grain size exhibits the highest response. An explanation of the different behavior of the In2O3 with different grain size sensitivity to NO2 under illumination and in the dark is proposed. We demonstrate that pulsed illumination may be used for NO2 detection at room temperature that significantly reduces the power consumption of sensor.

Nanocrystalline indium oxide films with extremely small grains in range of 7 to 40 nm were prepared by sol-gel method. The influence of grain size on the sensitivity of indium oxide to nitrogen dioxide in low concentration at room temperature was investigated under the UV illumination and without illumination. The sensitivity increases with the decrease of grain sizes when In2O3 is illuminated while in the dark In2O3 with intermediate grain size exhibits the highest response. An explanation of the different behavior of the In2O3 with different grain size sensitivity to NO2 under illumination and in the dark is proposed. The pulsed illumination is demonstrated may be used for NO2 detection at room temperature that significantly reduces the power consumption of sensor.

The influence of NO2 adsorption on the electric conductance of the nanocrystalline indium oxide with various sizes of nanocrystals has been investigated. When the nanocrystal size decreases, the sensitivity (the ratio of the In2O3 conductance in the air and the conductance after NO2 adsorption) grows at first but then declines. An explanation for the nonmonotonous behavior of the sensitivity is offered.

Influence of NO2 gas adsorption on electrical conductivity of nanocrystalline indium oxide with various sizes of nanocrystals was investigated. The sensitivity (the ratio between In2O3 conductivity in air and the conductivity after NO2 adsorption) increases at first with nanocrystals size reduction, but then the decrease is observed. The explanation of nonmonotonic dependence of sensitivity was proposed.

The current-voltage characteristics and temperature dependences of conductivity (in the temperature range from 210 to 330 K) of the structures containing silicon nanocrystals in the SiO2 matrix have been measured. Samples with various numbers of layers and nanocrystal sizes have been investigated. Based on the results, possible mechanisms of the charge carrier transfer in the studied structures at different temperatures have been analyzed.

Nanocrystalline indium oxide samples with various sizes of nanocrystals are synthesized by the sol-gel method. The minimal and maximal average sizes of nanocrystals are 7–8 and 18–20 nm, respectively. An analysis of conductivity measured at dc and ac signals in a wide temperature range (T = 50–300 K) shows that the transport of charge carriers at high temperatures takes place over the conduction band, while in the low-temperature range, the hopping mechanism with a varying jump length over localized states is observed.