Home – Home – Jornals – Avtometriya 2024 number 4

A preparation method is described in detail, which allows one to obtain defect-free cross sections of heterostructures for transmission electron microscopy and ensures the achievement of atomic resolution over a large area. The method is illustrated with examples of studying heterointerfaces of complex shape, selective oxidation, and selective etching of superlattices.

Photosensitive germanium layers on a silicon substrate have been formed by molecular beam epitaxy. The structural, optical and photovoltaic characteristics of the films have been investigated. The data obtained confirm the possibility of utilizing the developed Ge-on-Si heterostructures for the fabrication of photodetectors in the spectral range of 1.3-1.55 μm.

In this study, the electrical, morphological, and optical properties of thin aluminum films obtained by magnetron sputtering on SiON are studied. It is found that the growth of Al films on SiON follows the Stransky─Krastanov mechanism. At the stage of 3D growth, films with a cluster structure of Al grains and a pit/pore size of up to 20-50 nm are formed. For multilayer porous Al/SiON stacks, absorption of up to ~82% in the range of 1-4.2 µm and a redshift with an increase in the number of layers are observed. The analysis of optical losses of porous Al films, carried out by numerical modeling, shows the presence of optical absorption bands with a linear increase in the position of the absorption maximum λ_max at an increase in the thickness of the Al film, as well as a shift of λ_max to the long-wavelength region with a decrease in the size of Al clusters and pores between them.

We demonstrate the possibility of designing a semitransparent heater based on thin gold films. A thin 15 nm thick gold film with a surface resistivity of 3.5 Ω/□ and a transmittance in the visible range of 0.4 is deposited on a quartz substrate by pulsed laser deposition. The maximum heating temperature of the semitransparent heater is 113 °C at an applied power of 1.2 W. When a voltage is applied, the heating rate varies between 1-2 °C/s, and the rate rapidly decreases as the temperature approaches a steady state.

Using the catalytic chemical vapor deposition method, VACNT arrays with a height of 25 to 100 μm and a resistivity of 1.5 to 4 Ohm ⋅ cm have been grown for the first time on a Si/HfO₂/Fe surface. The growth of VACNTs on hafnium oxide is observed in the temperature range T = 625-725°C, but is not realized at T ≥ 750 °C. In this case, the temperature dependence of the VACNT growth rate is characterized by a value of ~1.5 eV. Using high-resolution scanning electron microscopy and Raman spectroscopy, the dominant presence of nanotubes with diameters from 1 to 10 nm in the array is shown. It is found that nanocrystallization of HfO₂ during annealing of substrates complicates the SEM analysis of catalytic Fe particles whose size on the surface of the initial amorphous HfO₂ is 2-5 nm.

The manuscript considers fundamental research in the field of nanomechanics of corrugated semiconductor nanomembranes composed of strained heterostructures. The results of a study of the magnetotransport of a two-dimensional electron gas in a corrugated nanomembrane made of a GaAs/InGaAs heterofilm are presented.

The results on the miniaturization of silicon-on-insulator (SOI) structures and SOI elements of integrated circuits (IC) are presented. To increase the IC performance, it is necessary to increase barriers and pulling electric fields due to high-k dielectrics and nanoscales, which lead to a noticeable decrease in the mobility of charge carriers with a decrease in the channel length and thickness. This, along with an increase in leakage due to source-drain tunnel currents, limits the physical length of the channel to 10 nm even when replacing silicon with two-dimensional (2D) materials such as graphene and metal dichalcogenides [1]. Three-dimensional (3D) integration in the form of double-gate transistors with complete depletion in SOI structures with a high-k buried dielectric (h- k BOX), in the form of the so-called fin transistors (FinFET) with two to four (gate-all-around ─ GAA) gates and channels of nanowires (NW FET), nanosheets (NS FET), nanoforks (FS FET), 2D materials and their 3D packaging allows one to increase the number of transistors on the chip, but not their performance. As an alternative, the option of increasing the functionality of the elements is considered, by replacing dielectrics in capacitors and transistors with ferroelectrics, and resistors with memristors, which leads to a transition from binary to neuromorphic logic, as well as to the implementation of the principles of radiophotonics, quantum devices, and sensors with parallel processing. A dynamically adjustable threshold and polarization of the gate ferroelectrics of complementary MOSFETs in heterosystems on a chip (SoC) will preserve ultra-low power consumption.

A strong response of nanosystems to the action of weak microwave power through the gap between the sample and the end of the coaxial cable from the microwave generator is detected by measurements at 4.2 K of the conductance of a short-channel p-type silicon transistor, as well as samples with a short quantum point contact in a two-dimensional electron gas of GaAs/AlGaAs heterostructures. The conductance response is gigantic in the tunnel regime of the devices; outside this regime, the sign of the microwave photoconductance depends on the mesoscopic state of the sample and the gate voltage interval under study. The mechanism of the discovered effects is elucidated by modeling mesoscopic transport within the framework of single-particle quantum mechanics and the Landauer formula, as well as by analyzing the basic circuits of electrical control of the semiconductor device. The main reason for the response of nanosystems to microwave exposure is found to be forced in-phase charge oscillations in contacts to the semiconductor due to capacitive connections in the near metallic environment of the sample.

Local anodic oxidation (LAO) of the Si(111) surface in the contact mode of an atomic force microscope (AFM) is studied depending on the relative humidity of the ambience - (35-75)% at two potentials U (-8 and -10 V) applied to the AFM probe. It is shown that LAO for U = -8V is realized at Θ ≥ 40% in the absence of growth of oxide lines in width; at U = -10V, their height and width increase linearly over the entire range of Θ values. Based on a detailed analysis of LAO and the deviation of the cantilever during the approach and retraction of the probe from the surface with variation of Θ without voltage on the probe, taking into account literature data for the semi-contact mode of AFM operation, a generalized model of the dependence of the LAO process on U and Θ is proposed.

This paper presents the results of a study of the structural and optical properties of arrays of (111)-oriented GaP nanowires (NWs) and single NWs using Raman spectroscopy and atomic force microscopy (AFM). GaP NW arrays are grown on a (111)-Si substrate by self-catalytic growth via the vapor-liquid-crystal mechanism. Single GaP NWs are mechanically transferred onto a gold surface. Transverse (TO), longitudinal (LO), and surface (SO) optical phonon modes are observed in the Raman spectra of GaP NWs. Surface-enhanced Raman scattering by optical phonon modes in GaP NWs near a gallium droplet is detected, due to the localized surface plasmon resonance in the droplet. Raman maps for GaP NWs recorded on various scattering geometries are obtained. The Raman enhancement factor for GaP NWs with a diameter of 104 and 60 nm reaches values of ~11 and 6, respectively.

The paper presents the results of a study of scanning irregularity in an optical interference microscope, performed both by a micrometer stage and a piezoceramic actuator. Registration of interference during the scanning process was carried out with a high-speed digital video camera, which allowed us to register the interference signal in detail. The obtained scanning results show the non-uniformity of the distances between adjacent interference fringes along the reference axis ─ the frame number. The procedure is presented that significantly decrease the value of non-uniformity. Application of such procedure allows to form a metric scale along scanning axis which can be used at performing high accuracy interference measurements of surface microrelief.

The paper presents results of identification of acoustic emission signatures of processes occurring during direct laser melting. As part of the experimental study, samples from the powder alloy EP 648 are grown in various modes with simultaneous recording of acoustic emission signals. Based on the results of the analysis of the registered signals parameters, their characteristic distribution patterns are formed during laser melting of defect-free and defective samples.

This paper proposes solutions that increase the efficiency of parallel program execution on high-performance computing systems when simulating heteroepitaxial growth on multiprocessor systems with shared memory. The developed algorithms are oriented towards the execution of program implementation of simulation of heteroepitaxial growth on multiprocessor NUMA nodes with shared memory. The primary prerequisite for the effective execution of parallel programs on the resources of a multiprocessor node is the incorporation of an architectural approach to the implementation of algorithms for data transfer through the shared memory of NUMA nodes. The proposed algorithms for optimizing synchronization in shared memory systems enhance the efficiency of accessing the shared memory of a multiprocessor node and reduce the time required for barrier synchronization. The developed methods and algorithms are implemented in the form of software for multiprocessor NUMA nodes with shared memory.