Thanks to Artificial Intelligence algorithms, new digital systems that supervise machines in production or in power plants are more and more enabled to provide pattern recognitions realizing predictive maintenance workflows. Nevertheless, the requirements of predictive maintenance are still very challenging when it is applied on machines which are not completely new and do not consist of intelligent PLC-systems offering all required interfaces to sensors and actors out-of-the-box. That is why other embedded systems are needed to implement predictive maintenance systems for machines that are not controlled by a PLC. Furthermore, these systems usually do not have any internet connection at all. This results in two requirements for so called “retro-fitted” predictive maintenance solutions: (1) External hardware and sensors are needed; (2) The system must be offline-capable [1]. This paper focuses on the development of an offline-capable anomaly detection system analyzing the footprint of a waste incinerator power plant’s induced draft. The induced draft is responsible to drain the poisoned gas out of the power plant’s burning chamber. It is not a redundant component and a critical element of the smoke gas cleaning system. The goal of the footprint analysis in this paper is to find out if an external embedded system with sensors could be used to find anomalies in the behavior of the machine offering the possibility to estimate maintenance cycles as well as to predict dangerous incidents.

Локальный спектральный анализ полупроводниковых структур для устройств фотоники возможен с помощью наноспектроскопии, включая нано-КРС (комбинационное рассеяние света) и нано-ФЛ (фотолюминисценцию).Эти методы представляют собой комбинацию атомно-силовой микроскопии (АСМ) и КРС, либо ФЛ и основаны на усилении оптического сигнала наноструктуры полем локализованного поверхностного плазмона металлического зонда АСМ микроскопа могут быть применены для изучения фононного и электронного спектров двумерных (2D), одномерных (1D) и нульмерных (0D) отдельных полупроводниковых наноструктур с пространственным разрешением ниже дифракционного предела.Представлены результаты исследования нано-КРС на оптических фононах нанокристаллов (НК) CdSe и AlN наноколонн AlN и пленок графена и мультиграфена, помещенных на плазмонные подложки и нано-ФЛ нанокристаллов GaAs и двумерных островков дихалькогенидов металлов (MoS2 и WS2).В диапазоне частот оптических фононов выполнено нано-КРС коллоидных нанопластинок CdSe/CdS, сформированных по типу ядро/оболочка, монослоев MoS2, помещенные в зазоре между металлизированным (Au, Ag) острием АСМ микроскопа и плазмонной подложкой, определены размеры и форма наноструктур, структурные дефекты и возникающие в них механические напряжения.Обсуждается различие нано-КРС от НК CdSe на отдельном нанодиске золота, записанное при различных длинах волн возбуждения.Нано-КРС на частотах поверхностных оптических (SO) фононов наблюдалось от отдельных наноколонн AlN (1D), помещенных на поверхность Au, и НК AlN (0D), выращенных с помощью молекулярно-лучевой эпитаксии на Si, и.Нано-КРС изображение отдельного НК AlN размером около 250 нм с кристаллической структурой вюрцита демонстрирует его гексагональную форму.Обсуждаются различия в нано-КРС изображениях наноколонн AlN, записанных при различной поляризации света.Нано-ФЛ от монослойных островков MoS2 и WS2, выращенных кремниевой подложке, демонстрируют локальное изменение энергии и интенсивности экситонной ФЛ в зависимости от числа монослоев и наличия структурных дефектов.Обнаружено усиление непрямозонной нано-ФЛ в нанокристаллах GaAs, что позволило выполнить нано-ФЛ картирование отдельного нанокристалла.Исследование поддержано Российским Научным Фондом (грант №22-12-00302).

We demonstrate local phonon analysis of single AlN nanocrystals by two complementary imaging spectroscopic techniques: tip-enhanced Raman scattering (TERS) and nano-Fourier transform infrared (nano-FTIR) spectroscopy. Strong surface optical (SO) phonon modes appear in the TERS spectra with their intensities revealing a weak polarization dependence. The local electric field enhancement stemming from the plasmon mode of the TERS tip modifies the phonon response of the sample, making the SO mode dominate over other phonon modes. The TERS imaging allows the spatial localization of the SO mode to be visualized. We were able to probe the angle anisotropy on the SO phonon modes in AlN nanocrystals with nanoscale spatial resolution. The excitation geometry and the local nanostructure surface profile determine the frequency position of SO modes in nano-FTIR spectra. An analytical calculation explains the behaviour of SO mode frequencies vs. tip position with respect to the sample.

Internet of Things (IoT) and Industry 4.0 hard- and software components are complex systems of application in the production and machinery field. Newer systems often approach the machine operators with modern user interfaces and capabilities of exporting data, connection of the sensors to manufacturing execution systems (MES) and analysis functionalities on specific cloud systems. But there are enormous amounts of production plants and machine park operators that are not able to use modern technologies due to diverse reasons: (1) The machines used for production are old machines and not capable to apply modern IoT technologies; (2) The production plant does not have an internet connection; (3) The machines used are modern but simple machines without IoT components fulfilling easy but critical tasks. This paper focuses on the development of a technological solution enabling machine operators with the above-mentioned challenges to benefit from IoT components like data acquisition, long-term data storing and flexible data exportation, including the important requirement “offline-capability”. To solve these challenges, the research team was combining a soft- and hardware solution that can acquire data continuously at machines with different technology components. The following steps were executed: (1) Evaluation and implementation of a load-balanced data acquisition technology with open-source database technologies and long-term data storage capabilities; (2) Evaluation and implementation of intelligent and flexible data exportation possibilities with no internet connection.

The light reflection properties of Ge disk lattices on Si substrates are studied as a function of the disk height and the gap width between disks. The interdisk spacing effect is observed even at such large gap widths as 500 nm. The gap width decrease leads to the appearance of the reflection minimum in the short wavelength region relative to one originated from the magnetic and electric dipole resonances in individual Ge disks, thereby essentially widening the antireflection properties. This minimum becomes significantly deeper at small gap widths. The observed behavior is associated with the features of the resonant fields around closely spaced disks according to numerical simulation data. The result shows the importance of using structures with geometrical parameters providing the short-wavelength minimum. This can essentially enhance their other resonant properties, which are widely used for applications, in particular, based on collective lattice resonances.

Resonance reflection of light from the ordered arrays of silicon nanopillars (Si NP) was investigated. The height of Si NP was 450 nm. The effect of Si NP oxidation in concentrated nitric acid on the position of resonances in reflection spectra was studied. A weak influence of the additional polymeric coating on the characteristics of reflection from the structures was proven. It is established on the basis of the results of experimental investigation and direct numerical modeling by means of three-dimensional finite difference time domain algorithm (3D FDTD) that the dependence of the resonant wavelength for Si NP on the diameter of Si NP is a linear function with nonzero displacement depending on the pitch.

Resonance reflection of light from the ordered arrays of silicon nanopillars (Si NP) was investigated. The height of Si NP was 450 nm. The effect of Si NP oxidation in concentrated nitric acid on the position of resonances in reflection spectra was studied. A weak influence of the additional polymeric coating on the characteristics of reflection from the structures was proven. It is established on the basis of the results of experimental investigation and direct numerical modeling by means of three-dimensional finite difference time domain algorithm (3D FDTD) that the dependence of the resonant wavelength for Si NP on the diameter of Si NP is a linear function with nonzero displacement depending on the pitch. Keywords: silicon nanopillars, structural colors, all-dielectric nanophotonics.

In this work, approaches for fabrication metal coated probes for Tip Enhanced Raman Spectroscopy (TERS) are considered. It was proposed to use optical characterization of probes to achieve the effective TERS of semiconductor nanoobjects. The shape and size of the metal cluster at the tip apex determines the position of the localized surface plasmon resonance, the electromagnetic field enhancement and, thus, TERS performance. The possibility of optimizing the characteristics of the probes for TERS studies of nanoobjects has been investigated.

В данной работе исследовался фононный спектр нанопластинок ZnSe разной толщины, синтезированных методом коллоидной химии. Для определения структурных параметров нанопластинок ZnSe использовалась просвечивающая электронная микроскопия. Нанопластинки ZnSe наносились капанием на Si подложку, покрытую тонким слоем (100 нм) золота. Затем проводился термический отжиг полученных образцов при Т=140ºС для удаления органики. Для измерения ИК спектров использовался ИК Фурье спектрометр Vertex 80v. ИК измерения проводились при нормальном и наклонном (75º) падении. Измерение спектров КРС проводилось с помощью спектрометра Horiba XploRa Plus в геометрии обратного рассеяния при комнатной температуре, длины волн возбуждения составляли 532 и 638 нм.

We report on the resonant plasmon enhancement Raman scattering (RS), photoluminescence (PL), and IR absorption by colloidal CdSe-based nanocrystals deposited on Au nanodisk and nanoantenna arrays. Numerical simulations were applied to calculate structural parameters of nanodisks and nanoantennas for which local surface plasmon resonance (LSPR) energy coincides with interband transition energies and surface optical (SO) phonon energies in NCs, correspondingly. The enhancement factors of RS and PL depend resonantly on the nanodisk size. Tip-Enhanced Raman Scattering (TERS) imaging allowed us to carry out the local spectral analysis of CdSe NCs with nanometer spatial resolution. A design of H-type nanoantennas was chosen to achieve maximal enhanced absorption by SO phonons from 1 monolayer of NCs.

Сообщается об исследовании фононного спектра одиночных наноструктур AlN с помощью ИК спектроскопии с пространственным разрешением в несколько десятков нанометров. В работе исследовались два типа образцов: (1)- вертикально стоящие гексагональные наноколонны AlN с латеральным размером около 300 нм и высотой 25 нм, сформированные методом аммиачной молекулярно-лучевой эпитаксии на поверхности слоя AlN на кремниевой подложке, (ось с перпендикулярна плоскости образа) и (2)- наноколонны AlN диаметром около 200 нм. и длиной до нескольких нанометров, лежащие на поверхности золота (ось с направлена вдоль поверхности образца), полученные эпитаксией из газовой фазы.

We report the phonon spectra of core/shell CdSe/CdS nanoplatelets with different shell thicknesses studied using Raman scattering. The nanoplatelets are rectangular colloidal nanocrystals, with thicknesses of core and shell layers of a few nanometers. The Raman spectra show features corresponding to the dominating longitudinal optical (LO) and surface optical (SO) phonon modes of the CdSe core in CdS shell located in the frequency regions of 200-210 and 250-290 cm-1, respectively. As the shell thickness increases, the phonon modes reveal a frequency shift and a change in intensity. The frequency shift associated with a change in the stress state in the core and shell, as well as with confinement effects is discussed. The phonon mode intensities are determined by the thickness of the shell and the proximity to resonant Raman scattering conditions.

We report on the study of localized surface plasmon resonances (LSPRs) arising in arrays of metal (Au) nanoclusters, dimers, and nanoantennas under the influence of external electromagnetic radiation. Using nanolithography, the plasmonic arrays with different morphologies including cylindrical nanoclusters and dimers, linear and H-type nanoantennas were fabricated. Their LSPR frequencies were determined from the analysis of optical reflection and IR spectra. LSPR frequency depends strongly on morphology of metal nanostructures and is varied from visible to terahertz spectral range with variation of the structures from cylindrical nanoclusters to the nanoantennas with a high aspect ratio. We established the interconnection between the structural parameters of the plasmonic arrays and their LSPR frequencies based on the results of 3D electrodynamic simulations.

We apply Raman spectroscopy to study the phonon spectrum in periodical GeSiSn/Si nanostructures with Sn concentration varied from 0 to 20%. In the optical spectral region, an insignificant shift of the phonon mode positions with a variation of the Sn content prevents determination of Sn concentration relying only on the optical phonons behavior. In the acoustic region, we observe the doublets of the folded acoustic phonons, the spectral positions of which undergo the low-frequency shift with increasing the Sn content. The application of the elastic continuum model with the linear approximation of sound velocity via Sn content in GeSiSn layers fails to explain the experimental results. This indicates a nonlinear Sn concentration dependence of sound velocity in GeSiSn layers which describes well the positions of the folded acoustic phonons.

Semiconducting nanoplatelets (NPLs) have attracted great attention due to the superior photophysical properties compared to their quantum dot analogs. Understanding and tuning the optical and electronic properties of NPLs in a plasmonic environment is a new paradigm in the field of optoelectronics. Here, we report on the resonant plasmon enhancement of light emission including Raman scattering and photoluminescence from colloidal CdSe/CdS nanoplatelets deposited on arrays of Au nanodisks fabricated by electron beam lithography. The localized surface plasmon resonance (LSPR) of the Au nanodisk arrays can be tuned by varying the diameter of the disks. In the case of surface-enhanced Raman scattering (SERS), the Raman intensity profile follows a symmetric Gaussian shape matching the LSPR of the Au nanodisk arrays. The surface-enhanced photoluminescence (SEPL) profile of NPLs, however, follows an asymmetric Gaussian distribution highlighting a compromise between the excitation and emission enhancement mechanisms originating from energy transfer and Purcell effects. The SERS and SEPL enhancement factors depend on the nanodisk size and reach maximal values at 75 and 7, respectively, for the sizes, for which the LSPR energy of Au nanodisks coincides with interband transition energies in the semiconductor platelets. Finally, to explain the origin of the resonant enhancement behavior of SERS and SEPL, we apply a numerical simulation to calculate plasmon energies in Au nanodisk arrays and emission spectra from NPLs in such a plasmonic environment.

The light reflection spectra of Ge disk nanoresonators on a Si substrate are studied, depending on their diameter (d) and height (h). The Ge disks, fabricated at temperatures close to room temperature using the bottom-up approach, exhibit a polycrystalline structure. The reflection at resonance wavelengths decreases more than 10 times, compared to surface areas without disks when the disk aspect ratio h/d increases to 1.0 and d > 100 nm. The strong dependence of the reflection minimum on h/d can be associated with the influence of the substrate. An effective refractive index, defined as neff = lambda(m)/d and determining the long-wavelength resonance mode position lambda(m), turns out to be larger for disks than for spheres. It is also significantly larger than the Ge refractive index. This allows the use of disks of smaller diameter than spheres to achieve the resonance effects at the same wavelength.

A review of recent results and new data on the study of the optical response from semiconductor nanocrystals obtained using plasmon-enhanced optical spectroscopy, including surface enhanced Raman scattering (SERS) and plasmon-enhanced IR absorption, is presented. These methods are based on the amplification of the phonon response of semiconductor nanocrystals located in the field of localized surface plasmon resonance (LSPR) of metal nanostructures. Owing to the choice of a specific morphology of metal nanostructures, coincidence of the LSPR energy with the laser excitation energy and / or the energy of optical phonons in nanocrystals is provided. Resonant conditions ensure a significant increase in local electric fields and, as a result, a sharp increase in the Raman signal and IR absorption at the frequencies of surface optical phonons of nanocrystals. Amplification of the optical response makes it possible not only to detect monolayer coatings of nanocrystals, but also to study their crystal structure, phase and element compositions, and internal mechanical stresses. Application of Raman scattering (RS) in combination with atomic force microscopy with the use of a metallized probe has opened up new possibilities for analyzing the vibrational and electronic spectra of nanocrystals with nanometer spatial resolution

Multicomponent semiconductor nanostructures were studied by local spectral analysis based on surface-enhanced Raman scattering by semiconductor nanostructures located on the surface of an array of Au nanoclusters near the metallized tip of an atomic force microscope. In the gap between the metal nanoclusters and the tip, where a semiconductor nanostructure is located, there is a strong increase in the local electric field (hot spot), resulting in a dramatic enhancement of the Raman scattering signal. An unprecedented enhancement of the Raman scattering signal by two-dimensional (over 10(8) for MoS2) and zero-dimensional (10(6) for CdSe nanocrystals) semiconductor nanostructures was achieved. The use of the method for mapping the Raman scattering response of a multicomponent system of MoS2 and CdSe made it possible to identify components with a spatial resolution far exceeding the diffraction limit.

We report on the investigation of the localized surface plasmon resonance (LSPR) in periodical Au nanostructures. The arrays of Au nanoclusters and dimers were fabricated on Si and Si/SiO2 surfaces by electron beam lithography. Diameters and periods of nanoclusters with disk shape vary in the range of 30–150 and 130–200 nm, respectively. Because of the opaque nature of the substrates, optical reflection spectroscopy was chosen to probe the plasmonic properties of the metal nanostructures. From a comparison of experimental reflection spectra with those numerically simulated by the Finite Difference Time Domain (FDTD) method, we determined the model structural parameters of the plasmonic nanostructures. These parameters were further used for the calculation of absorptance spectra of the plasmonic structures for which absorptance in the substrate was subtracted. LSPR positions were determined from the maxima of the absorptance spectra.

Предложен новый метод локального спектрального анализа полупроводниковых наноструктур, основанный на обнаруженном гигантском комбинационное рассеяние света (КРС) полупроводниковыми наноструктурами, расположенными на поверхности массива нанокластеров Au, вблизи металлизированного кантилевера атомно-силового микроскопа (АСМ). В зазоре между металлическими нанокластерами и острием кантилевера АСМ микроскопа, где расположена полупроводниковая наноструктура, возникает сильное увеличение локального поля («горячая точка») и, как следствие, резкое усиление сигнала КРС. В эксперименте наблюдается гигантское усиление сигнала КРС локализованными продольными и поверхностными оптическими фононами (LO и SO) в нанокристаллах (НК) CdSe (коэффициент усиления 106). Картирование сигнала КРС на частоте оптических фононов CdSe позволило изучить эффекты локальных электромагнитных полей на фононный спектр нанокристаллов CdSe с пространственным разрешением 2 нм [1], определить фононный спектр отдельных нанокристаллов CdSe размером 6 нм [2], что находится далеко за дифракционным пределом (Рис.1б). Показано, что максимальное усиление сигнала наблюдается от торцов нанокластеров Au, имеющих цилиндрическую форму, где локальное электромагнитное поле максимально.