Investigation of random telegraph noise characteristics of Hf-based MONOS nonvolatile memory devices with HfO2 and HfON tunneling layer

This paper investigated the low frequency noise (LFN) utilizing 1/f noise and random telegraph noise (RTN) characteristics of Hf-based metal/oxide/nitride/oxide/silicon (MONOS) nonvolatile memory (NVM) device with HfO2 and HfON tunneling layer (TL). The low frequency noise spectral density (SID ) was investigated to evaluate the interface characteristics with fresh and after programming/erasing (P/E) cycles of 104. Both devices show similar slope of ~1/f in all of the frequency regions. Although HfON TL shows high SID compared to HfO2 TL, increased ratio is 15.4 which is low compared to HfO2 TL of 21.3. As decreasing the channel length from 10 to 2 μm, HfON TL shows small increased ratio of SID . Due to the nitrided characteristics, HfON TL suppress the degradation of interface. Finally, it is found that trap site of HfO2 TL is located near the interface by RTN measurement with capture (τC) and emission time constant (τE).

Sound Absorption Performance of Aluminum Silicate Fiber for Noise and Vibration Reduction of Distribution Transformer

In view of the low-frequency noise problem in urban substation, the sound absorption (SA) properties of aluminum silicate fibers (ASF) with different materials, unit weight, plate thickness and cavity thickness were tested in this paper. It was found that the high-purity ASF with larger unit weight, plate thickness and cavity thickness had larger low-frequency SA coefficient, which provided technical support for the development of new low-frequency noise reduction materials for substation.

Transcriptome Analysis of the Central Nervous System of Sea Slug (Onchidium reevesii) Exposed to Low-Frequency Noise

Low-frequency noise has become a marine pollutant that cannot be ignored, but most studies have focused on the behavioral and physiological effects on marine vertebrates, with few studies in marine mollusks. Therefore, sea slug was used in this study to investigate the effect of low-frequency noise on its physiological aspects. This experiment was designed with different low-frequency noise (0, 100, 300, and 500 Hz) and different stimulation times (0, 6, and 12 h) to measure superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT) activities in hemolymph and transcriptomics in the control (C) and 6 and 12 h groups (L1 and L2) with 500 Hz noise. The results showed a positive correlation between antioxidant enzyme activity and low-frequency noise frequency (P < 0.05) and no correlation with time (P > 0.05). In central nervous system (CNS) transcriptomics, 2,460 and 3,268 genes had upregulated expression and 2,765 and 2,783 genes had downregulated expression in the L1 and L2 groups, respectively, compared to the C group. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, low-frequency noise mainly affects signaling pathways such as cytokine-cytokine receptor interaction, the FoxO signaling pathway, natural killer cell-mediated cytotoxicity, apoptosis immune-related pathways, and energy metabolic pathways such as glycolysis, the TCA cycle, and glycerophospholipid metabolism, as well as neurological pathways such as GABAergic synapses, the synaptic vesicle cycle, amyotrophic lateral sclerosis (ALS) and other neurological pathways. This study would provide valuable reference information on the potential response of mollusks to low-frequency noise stress.

Features of time variations of microseismic noise at seismic stations in Tajikistan

The spectral structure of microseismic noise in the frequency range of 0.01-40 Hz at different times of the day and year, recorded by broadband equipment at eight IRIS group seismic stations in Tajikistan in 2005-2020, was analyzed. Two disjoint frequency ranges are distinguished, which we conditionally call "high-frequency" (2-40 Hz) and "low-frequency" (0.01-0.75 Hz) noise, separated by a natural drop in the noise amplitude to 20-30 Db. It is assumed that the high-frequency range of noise has a local nature, due to exogenous sources of natural origin in the form of wind gusts, concussions from powerful watercourses and fluctuations in the level of large reservoirs, as well as man-made in-terference due to road and quarry explosions, the work of large industrial enterprises and concussions from road traffic. Low-frequency noise is most likely caused by global storm microseisms. High-frequency noise has a well-defined daily frequency, which is completely absent in low-frequency noise. At the same time, in both frequency ranges, the existence of a clearly pronounced seasonal peri-odicity has been established, the amplitude of which reaches 6-7 Db for high-frequency noise and about half as much for low-frequency noise. However, at the same time, the seasonal frequency of high frequency and low-frequency noise turns out to be antiphase, which indicates in favor of the different genesis of these two components of microseismic noise. The amplitude of the diurnal periodicity in variations of the high-frequency noise level is maximal during the daytime, remaining approximately constant for 8-10 hours. At the same time, the decline in the noise amplitude in the evening lasts longer than the steeper morning growth. The time intervals of a sharp increase and decrease in the intensity of the discussed daily extreme are quite well correlated, respectively, with morning and evening twilight at different times of the year. This is reflected in the wider flat part of the maximum noise level in summer compared to winter and the differences in its level up to 6 Db in favor of summer time. This observation can be considered as a manifestation of the deep influence of the Sun on the oscillatory processes that generate high-frequency microseismic noise.

Review of Low-Frequency Noise Properties of High-Power White LEDs during Long-Term Aging

Low-frequency noise investigation is a highly sensitive and very informative method for characterization of white nitride-based light-emitting diodes (LEDs) as well as for the evaluation of their degradation. We present a review of quality and reliability investigations of high-power (1 W and 3 W) white light-emitting diodes during long-term aging at the maximum permissible forward current at room temperature. The research was centered on the investigation of blue InGaN and AlInGaN quantum wells (QWs) LEDs covered by a YAG:Ce3+ phosphor layer for white light emission. The current-voltage, light output power, and low-frequency noise characteristics were measured. A broadband silicon photodetector and two-color (blue and red) selective silicon photodetectors were used for the LED output power detection, which makes it possible to separate physical processes related to the initial blue light radiation and the phosphor luminescence. Particular attention was paid to the measurement and interpretation of the simultaneous cross-correlation coefficient between electrical and optical fluctuations. The presented method enables to determine which part of fluctuations originates in the quantum well layer of the LED. The technique using the two-color selective photodetector enables investigation of changes in the noise properties of the main blue light source and the phosphor layer during the long-term aging.