Search

The effect of low exposure doses (5–40 kR) of gamma radiation on the electrical properties of structures based on a mesoporous silicon (SiMP) layer is investigated. It is demonstrated that the conductivity of the SiMP layer increases, the Fermi level shifts, and the trap density changes in gamma-irradiated Al/SiMP/p-Si/Al structures. Long-term stable switched-state memory in the region of the I–V curve hysteresis is revealed. This effect is controlled by the irradiation dose.

Electrical and photoelectric properties of porous silicon with introduced silver nanoparticles have been studied. It is shown that in the “dark–light–dark” operation mode, an abrupt jump of the dark current is observed upon illumination (with light spectrally close to sunlight), which is three to five times the initial dark current and the photocurrent. The voltages at which these abrupt changes in current are observed correspond to the range of existence of traps formed when the starting mesoporous silicon is obtained. It was found that the increased value of the dark current exhibits a long-term memory effect. The “current jump” can be attributed to the maximum capture of the generated photocarriers by traps, followed by their release in an electric field after the illumination.

A comparative study of the optical and morphological properties of different modifications of silicon and their dissolution upon interaction with distilled water and a biologically active medium is carried out. For the biologically active medium, nonpathogenic baker’s yeast (Saccharomycetes cereviseae) is chosen. It is shown that water and the biologically active medium interact with the surface of the materials and, thus, change the surface morphology and produce a modified layer. The strengths of the effect upon nanoparticles, nanoparticle-based structures (porous silicon), and single-crystal silicon doped with different types of impurities to different levels are different.

The photoelectric and photovoltaic properties of structures based on mesoporous silicon passivated with iron (SiMP:Fe) are studied. It is shown that these properties ambiguously depend on the iron concentration. In the case of a sample with space-charge-limited currents (SCLCs), the charge-transport mechanism in the Al-SiMP:Fe-p-Si-Al heterostructure changes under illumination from the SCLC type to the barrier type. Passivation with 0.1–0.2 at % iron stabilizes not only the electrical, but also the photoelectric and photovoltaic properties of the structures. A further increase in the Fe concentration gives rise to new traps caused by the appearance of iron and silicon oxides, which leads to instability of the properties. The structures exhibit high sensitivity under low-level illumination. The open-circuit voltage is 16 mV under AM-1 irradiation (∼2 mW/cm2).

The current-voltage and capacitance-voltage characteristics of structures based on mesoporous silicon, obtained by electroless etching with passivation by iron, (SiMP:Fe) are investigated. It is shown that the conductivity and barriers in Al-SiMP:Fe-p-Si-Al heterostructures ambiguously depend on the Fe concentration. Passivation by iron changes not only the conductivity of the SiMP:Fe layer but also the character of carrier transport at low frequencies. At an iron concentration of ∼1 at % tunneling transport through barriers becomes dominant in comparison with jumps over dangling bonds. Passivation of the SiMP layer by iron stabilizes the SiMP electrical properties (which is confirmed by the values of the trap concentrations estimated from the current-voltage characteristic) of structures subjected to long-term storage. This is likely to be related to the interaction between iron ions and the silicon surface with the formation of oxides.

The electrical and photoelectric properties of nanostructures with porous silicon layers obtained by electroless etching of silicon have been investigated. It is found that the photoelectric and photovoltaic properties of these structures depend on their morphology and are determined by not only the properties of the modified layer, but also the presence of possible barriers in the layered porous silicon. The ratio of the photoconductivity to the dark conductivity reached 102−5 × 102. An open-circuit voltage V oc was detected that amounted to ∼250 mV at an incident light power close to AM-1 (∼100 mW/cm2). In this case, the density of short-circuit current I sc was about 20 μA/cm2.

The electron-transport processes in structures with oxidized porous silicon (OPS) are investigated during adsorption and desorption of polar molecules from atmosphere when the air pressure varies. It is shown that the cause of the existence of the open-circuit voltage in Pd-OPS-p+-Si-Al structures in the initial state is the surface-charge change on the Pd-OPS interface due to the polar-molecule adsorption from atmospheric air. The desorption of atmospheric-air molecules leads to a change in the current-voltage characteristics of structures, growth of the metal-OPS barrier in samples with the Schottky barrier, and initiation of current instabilities. The nanocrystalline nature of OPS manifests itself in the charge-carrier localization in quantum dots (QDs) during desorption in samples with space-charge-limited currents.

The effect of illumination and adsorption of polar molecules on the properties of structures based on oxidized porous silicon has been investigated. The specific features of these structures are fluctuations and a change in the sign of open-circuit voltage under the influence of long-term photoexcitation, time-related instabilities of the current in media with a high content of hydrogen sulfide, long periods of photocurrent decay after switching off the illumination, and the occurrence of negative photoconductivity in structures with space-charge-limited currents. The results obtained are explained by the presence of multiply charged traps of different types in oxidized porous silicon, their charge exchange, and the tunneling of charge carriers between silicon nanocrystallites.

In situ measurement of the formation process of low-dimensional porous silicon (PS) structures was developed. The measurements are based on the analysis of polyharmonic time dependence of the reflected radiation. The results show high sensitivity to H 2 S in PS based structures with catalytic (Pd, Ni) and ohmic (Al) electrodes. In the best samples the appearance of three molecules H 2 S on 10 9 molecules N 2 increased the electrical current value by a factor of 2–3. The structures selectively measure H 2 S concentration from 0.02 to 1000 ppm. It was found that unusually high reversible and nonreversible optical properties change because of the influence of gas solvents and alcohol. The exposure of PS layers to ethyalcohol vapor changes the color of PS from bright blue to crimson and the refraction coefficient in the IR region changes up to 0.06.

Memristor structures based on tunnel-thin organic dielectric and porous silicon layers are investigated.

The current-voltage and the current-capacitance characteristics of structures on the basis of mesoporous silicon received by nonelectrolitic method of etching at passivation by iron (SiMP:Fe) are investigated. It is shown, that in heterostructures Al-SiMP:Fe-pSi-Al conductivity and barriers depend on Fe concentration no monotonic.

The effect of biologically active environments and water on various modifications of silicon are investigated.

Nickel nanoparticles influence on the electrical properties of porous silicon obtained by the no-current electroless etching are investigated.

The influence of NiSO 4 saturation on the electrophysical mesoporous silicon layers obtained by electrochemical method are investigated.

This article deals with investigation of nanostructures properties' synthesized by no-current modification of monocrystal silicon.

This article deals with investigation of nanolayers' properties generated on Si surface in H 2 O

The possibilities of creating sensors on the basis of silicon structures with classical and quantum-dimensional effects have been researched theoretically and experimentally. The technology of forming qnantuln-well and wire structures of porous and amorphous silicon and their modifications by multiparameter monitoring in situ has been studied. H 2 S sensor samples, developed on this basis, have a high sensitivity (on the level 10-20 ppb), low operating voltage (1-1.5 V), low power consumption (not more than 10 -8 -10 -6 W) and relative selectivity to hydrocarbons, CO and CO 2 . The most sensitive to H 2 S ate structures having p = 0.03 Ω cm, oxidized porous silicon layer thicknesses of 6-10 μcm, porosity of 0.75-0.8 and Pd layer thicknesses of 50-60 nm. The obtained results verify the principle possibilities in solving all growing contradictions between information processing and its reception by using low-dimensional structures.

We discuss the possibility of determining the electrophysical properties of semiconducting materials based on the determination of their optical constants by the method of broken total internal reflection. As the material for the total-internal-reflection prism it is proposed to use the experimental material, but with a much lower carrier concentration, The possibilities of the proposed method are demonstrated using as an example high-resistance silicon for the TIR prism and the experimental sample of n-type silicon.

A nondestructive method of determining the parameters of epitaxial film systems is proposed based on a variational method of computing the coefficients of reflection and transmission of an electromagnetic wave in lamellarly inhomogeneous semiconductor structures. Structures of the type low-alloy film-transition layer-high-alloy substrate are considered with various prescriptions for varying the concentration of the alloying additives in the transition layer near the plasma resonance of the charge carriers in the substrate. Preliminary experimental investigations of the epitaxial N-N+ structures of silicon are in satisfactory agreement with computed data. The proposed method makes it possible to determine the thickness of the low-alloy layer and of the transition layer separately on the basis of the spectral dependence of the reflected radiation.