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With the shift in advanced packaging toward 3D integration and flexible electronics, it is becoming critical to produce high-quality silicon nitride films under low thermal budgets. To overcome the limitations of low-temperature deposition, this study compares two gas mixtures—SiH4/NH3/N2 and SiH4/N2—in plasma-enhanced chemical vapor deposition of silicon nitride coatings. We systematically evaluated how the NH3 precursor affects deposition kinetics, chemical bonds, non-uniformity, optical properties, and internal stress at different RF powers and electrode gaps. The test results show that NH3, with its lower dissociation energy, avoids the high activation barrier associated with pure N2 plasma, leading to a higher reactive nitrogen flux and a doubled deposition rate. In the SiH4/NH3/N2 system, raising RF power from 300 W to 900 W reduced hydrogen content from 23.58% to 12.25%. This suppression of hydrogen promoted structural densification, shifting the mechanical stress from 173.3 MPa to −989.7 MPa. At a larger electrode gap of 19 mm, NH3’s better diffusion characteristics offset the electric field sensitivity typical of N2 systems, reducing large-area film non-uniformity by 28.7% compared to a 13 mm gap. This work offers a practical, mass-production-friendly approach for depositing robust, low-hydrogen, highly uniform silicon nitride films at low temperatures.

The impact of ammonia (NH3) emissions from animal agriculture on the secondary formation of inorganic fine particulate matter (i.e., iPM2.5) has become of great public concern. The formation of iPM2.5 from NH3 is known as the gas–particle partitioning of gaseous NH3 and aerosol ammonium (NH4+), which is assumed to be in a thermodynamic equilibrium. This research aimed to gain an in-depth understanding of the impact of ambient NH3 on secondary iPM2.5 by analyzing the PM2.5 mass closure, atmospheric chemical conditions, and the gas particle partitioning of NH3-NH4+ in the near field of a poultry production unit in North Carolina. Samples of precursor gases (i.e., NH3, SO2, NO2) to iPM2.5 and PM2.5 were taken on this poultry production unit at four sampling stations in four wind directions through summer, autumn and winter seasons to determine gas concentrations and PM2.5 chemical compositions. It was discovered that this rural site contained low ambient concentrations of iPM2.5 precursor gases, and PM2.5 composition was dominated by organic carbon (OC) (80% to 94%) while iPM2.5 fraction was insignificant (0% to 2%). Low availability of H2SO4 and HNO3 gases (from SO2 and NO2 conversions) limited NH3 neutralization potential and iPM2.5 formation; moreover, high OC fraction may inhibit NH4+ formation. With the field measurements of ambient temperature, humidity, precursor gases and PM2.5 chemical speciation data, the ISORROPIA-II thermodynamic equilibrium model was used to conduct the sensitivity analysis, and we found that iPM2.5 was the most sensitive to increasing total HNO3 (gas + aerosol) at low temperatures. The formation potential of iPM2.5 at this rural site was at its highest during the wintertime when SO2 was extremely low.

Urban areas in developing countries are major sources of carbonaceous aerosols and air pollutants, pointing out the need for a detailed assessment of their levels and origin close to the source. A multi-instrument research campaign was performed in Delhi during December 2015–February 2016 aimed at exploring the pollution levels and the contribution of various sources to particulate matter (PM) concentrations, black carbon (BC) aerosols, and trace gases. The weak winds (< 5–6 m s −1 ) along with the shallow boundary layer favoured the formation of thick and persistent fog conditions, which along with the high BC (24.4 ± 12.2 μg m −3 ) concentrations lead to the formation of smog. Very high pollution levels were recorded during the campaign, with mean PM 10 , PM 2.5 , CO, NO, and O 3 concentrations of 245.5 ± 109.8 μg m −3 , 145.5 ± 69.5 μg m −3 , 1.7 ± 0.5 ppm, 7.9 ± 2.3 ppb, and 31.3 ± 18.4 ppb, respectively. This study focuses on examining the daily/diurnal cycles of the aerosol optical properties (extinction, scattering, absorption coefficients, single scattering albedo), as well as of PM and other pollutant concentrations, along with changes in meteorology (mixing-layer height and wind speed). In addition, the hot-spot pollution sources in the greater Delhi area were determined via bivariate plots and conditional bivariate probability function (CBPF), while the distant sources were examined via the concentration weighted trajectory (CWT) analysis. The results show that the highest aerosol absorption and scattering coefficients, PM, and trace gas concentrations are detected for weak winds (< 2 m s −1 ) with a preference for eastern directions, revealing high contribution from local sources and accumulation of pollutants within urban Delhi.

The impact of operating cost savings in a plasma-enhanced atomic layer deposition (P-ALD) process to fabricate the ultrathin yttria-stabilized zirconia (YSZ) electrolyte for low-temperature solid oxide fuel cells is quantitatively evaluated by comparison with a thermal atomic layer deposition (T-ALD) process considering the two cost factors: (1) operating costs of power consumption and precursor/gas usages and (2) capital costs of plasma generator installations. Because of lower precursor/gas usages and lower power consumption of the P-ALD YSZ process, it is evaluated that the specific operating costs of the P-ALD YSZ process is ~ 47% lower than that of the T-ALD YSZ process. For annual production of 2.6 kW fuel cell systems of 100 units, it is estimated that the cumulative cost savings of the P-ALD YSZ process versus the T-ALD YSZ process amounts to $678,000 in the fifth year.

A semi-continuous monitoring system, a parallel plate wet denuder and particle into liquid sampler coupled with ion chromatography (PPWD-PILS-IC), was used to measure the hourly precursor gases and water-soluble inorganic ions in ambient particles smaller than 2.5 µm in diameter (PM2.5) for investigating the thermodynamic equilibrium of aerosols using the ISORROPIA-II thermodynamic equilibrium model. The 24-h average PPWD-PILS-IC data showed very good agreement with the daily data of the manual 5 L/min porous-metal denuder sampler with R2 ranging from 0.88 to 0.98 for inorganic ions (NH4+, Na+, K+, NO3−, SO42−, and Cl−) and 0.89 to 0.98 for precursor gases (NH3, HNO3, HONO, and SO2) and slopes ranging from 0.94 to 1.17 for ions and 0.87 to 0.95 for gases, respectively. In addition, the predicted ISORROPIA-II results were in good agreement with the hourly observed data of the PPWD-PILS-IC system for SO42− (R2 = 0.99 and slope = 1.0) and NH3 (R2 = 0.97 and slope = 1.02). The correlation of the predicted results and observed data was further improved for NH4+ and NO3− with the slope increasing from 0.90 to 0.96 and 0.95 to 1.09, respectively when the HNO2 and NO2− were included in the total nitrate concentration (TN = [NO3−] + [HNO3] + [HONO] + [NO2−]). The predicted HNO3 data were comparable to the sum of the observed [HNO3] and [HONO] indicating that HONO played an important role in the thermodynamic equilibrium of ambient PM2.5 aerosols but has not been considered in the ISORROPIA-II thermodynamic equilibrium model.

Increased ammonia (NH3) emissions from intensive agriculture negatively affect environmental and ecosystem health, contributing to formation of particulate matter (PM) and the potent greenhouse gas, N2O. Better understanding NH3 emissions from the manure composting process and their behavior as a constituent of the atmospheric aerosol load is a crucial element in creating better farm management systems, improving public health outcomes, and mitigating the broader environmental and climatic impacts of agriculture. Retarded generation of PM with a major constituent source of NH3 is a primary mechanism for evaluating the effects of agricultural contribution to PM. This study aimed to quantify NH3 emissions, examine the influence of environmental factors, and investigate the relationship between precursor gases (SO2, NOx, NH3) and PM2.5 at a modern manure composting facility in Paju, South Korea. Over 35 days, average internal concentrations of NH3, SO2, and NOx were significantly higher than external levels. NH3 concentrations reached 3.64 ± 0.06 mg m−3 at 3 m height and 2.43 ± 0.16 mg m−3 at ground level, while the total NH3 flux from the facility was 24.47 ± 1.39 NH3-N kg d−1. Internal PM2.5 concentrations (36.9 ± 2.6 µg m−3) were about 50% higher than external levels (23.7 ± 2 µg m−3), with a moderate correlation (r = 0.341) suggesting some contribution of external PM2.5 to internal levels. Despite large quantities of internal emissions, the facility’s sealed design with a negative pressure ventilation system effectively minimized external emissions. These results suggest that while manure composting facilities are significant sources of NH3 and PM2.5, advanced systems like high-volume ventilation and scrubbing technologies can effectively reduce their impact on regional air pollution, contributing to better environmental management in agriculture.

The formation of inorganic fine particulate matter (i.e., iPM2.5) is controlled by the thermodynamic equilibrium partitioning of NH3-NH4+. To develop effective control strategies of PM2.5, we aim to understand the impacts of changes in different precursor gases on iPM2.5 concentrations and partitioning of NH3-NH4+. To understand partitioning of NH3-NH4+ in the southeastern U.S., responses of iPM2.5 to precursor gases in four seasons were investigated using field measurements of iPM2.5, precursor gases, and meteorological conditions. The ISORROPIA II model was used to examine the effects of changes in total ammonia (gas + aerosol), total sulfuric acid (aerosol), and total nitric acid (gas + aerosol) on iPM2.5 concentrations and partitioning of NH3-NH4+. The results indicate that reduction in total H2SO4 is more effective than reduction in total HNO3 and total NH3 to reduce iPM2.5 especially under NH3-rich condition. The reduction in total H2SO4 may change partitioning of NH3-NH4+ towards gas-phase and may also lead to an increase in NO3− under NH3-rich conditions, which does not necessarily lead to full neutralization of acidic gases (pH < 7). Thus, future reduction in iPM2.5 may necessitate the coordinated reduction in both H2SO4 and HNO3 in the southeastern U.S. It is also found that the response of iPM2.5 to the change in total H2SO4 is more sensitive in summer than winter due to the dominance of SO42− salts in iPM2.5 and the high temperature in summer. The NH3 emissions from Animal Feeding Operations (AFOs) at an agricultural rural site (YRK) had great impacts on partitioning of NH3-NH4+. The Multiple Linear Regression (MLR) model revealed a strong positive correlation between cation-NH4+ and anions-SO42− and NO3−. This research provides an insight into iPM2.5 formation mechanism for the advancement of PM2.5 control and regulation in the southeastern U.S.

In recent years, ozone (O 3 ) air pollution has become a major problem—which is still increasing—in China. In this study, data on the O 3 concentration as well as on two of its influencing factors, meteorological parameters and traffic conditions, were collected in Fuzhou and then analyzed via wavelet transforms to evaluate the variation in O 3 concentration and its relationships with the factors. High concentrations appeared during spring and summer, and notable fluctuations occurred primarily from March till April, from June till July and during September. The level of O 3 exhibited significant positive correlations with the temperature and sunshine duration but negative ones with the relative humidity, precipitation and air pressure; additionally, it increased when the wind speed was low and fluctuated when the wind speed was high. The concentration was also significantly negatively correlated with the concentrations of O 3 precursors (NO x and CO) and hence closely related to the traffic conditions, as the reduced vehicle speed during rush hour due to increased vehicle flow and traffic density led to higher precursor emissions in the vehicular exhaust. A prominent “weekend effect” was observed with the precursor levels, which displayed greater fluctuations during the weekdays than the weekends; the vehicle flow and the O 3 concentration.

To assess the surface ozone concentration (O 3 ), there is a need to establish relationship between air pollutants and meteorological parameters. The study was conducted on variation of air pollutants, viz. O 3 , nitrogen oxides (NO X  = NO 2  + NO) and carbon monoxide (CO) along with meteorological parameters like temperature (Temp), relative humidity (RH), solar radiation (SR) and wind speed (WS). The precursor gases were recorded in Hyderabad at Tata Institute of Fundamental Research-National Balloon Facility (TIFR-NBF; 17.47° N, 78.58° E). Correlation analysis is done on hourly averaged trace gases concentration and metrological data for the entire year 2016. O 3 is in negative correlation with NO X , CO and RH. NO X which is one of the precursor gases plays a major role in formation of O 3 by photo-chemical reaction (PCR). The increase in O 3 concentration is in proportion with the decrease in NO X concentration. O 3 correlated positively with Temp, SR and WS. Two sets of four models were constructed with multiple linear regression (MLR) representing the data for the three seasons (summer, winter and monsoon) and for the total year as well. The adjusted R 2 was determined and found to be in the range of 0.6 to 0.9 for the models using precursor gases and 0.9 by meteorological parameters. The models were validated by various performance indicators, viz. root mean square error (RMSE), mean absolute error (MAE) and mean biased error (MBE).