Dot Density Research Articles

Influence of He injection amount on the microstructure of ion irradiated Cr0.8FeMnNi medium entropy alloy compared with 316L stainless steel

In recent years, medium and/or high-entropy alloys (M/HEAs) have attracted attention due to their excellent mechanical properties, positioning them as potential candidates for structural materials in advanced nuclear reactors. This study investigated the effect of He injection amount on the microstructural evolution in Cr0.8FeMnNi MEA and 316L stainless steel. Helium atoms were injected, followed by Fe2+ irradiation. Transmission electron microscopy was used to characterize the irradiation-induced defects. The primary irradiation-induced defects observed across all He injection amounts were black dots; no voids were seen under any irradiation conditions. In He-injected Cr0.8FeMnNi, the number density of black dots was significantly lower than in non-He-injected Cr0.8FeMnNi, while the average size of black dots increased with higher He injection rates. As the He injection amount increased, the binding energy of the self-interstitial atom (SIA) to the He-V complex decreased. This reduction facilitated the nucleation and growth of numerous SIA clusters within the matrix, consequently increasing the number density of black dots. The change in the number density of black dots in Cr0.8FeMnNi was much smaller than that observed in 316L. This could be ascribed to the enhanced self-healing process caused by the diversity of point defects and higher lattice distortion in Cr0.8FeMnNi.

Spatial mapping of dengue fever prevalence and its association with geo-climatic factors in Lahore, Pakistan.

A vector-borne disease of concern for global public health, dengue fever has been spreading its endemicity and several cases in recent years, particularly in Lahore Pakistan. Dengue transmission is influenced by geo-climatic conditions. This study aimed to map the spatial prevalence of dengue fever in Lahore and its association with geo-climatic factors during the epidemic of the year 2021. In this study, geo-climatic factors that could potentially encourage the growth of the virus are chosen for this study, and their temporal and spatial changeability relate to dengue cases. The objective of this study is to use meteorological, satellite data and Geographic Information System (GIS) techniques to map dengue outbreaks and identify the risk-prone areas by relating geo-climatic factors with dengue outbreaks. The dengue patients and their locations data were collected from the Directorate General of Health Services (DGHS) Lahore. This study uses Google Earth and Landsat-8 OLI/TIRs images to extract geo-climatic and land use parameters. The dot density maps technique was used to represent the spatiotemporal distribution of dengue cases. The hotspot analysis was applied to show the hotspots of dengue cases in district Lahore at the Union Council (UC) level. The Normalised Difference Vegetation Index (NDVI), Normalised Difference Water Index (NDWI), built-up area, population density, precipitation, and Land Surface Temperature (LST) are the factors employed. In this study, correlation was performed to test the significance between precipitation and the prevalence of dengue fever in Lahore. The results show that the incidence and prevalence of dengue fever month-wise at the UC level in Lahore. The distribution pattern of dengue outbreaks in the Lahore area and its demographic factors were found to be associated. It concludes that the increase in the spread of dengue fever is associated with the monsoon rains. The prevalence of dengue is associated with water bodies and high land surface temperature, but it does not represent any significant relation with vegetation cover and land use in Lahore during the year 2021. The study pinpointed the locations that are most susceptible and require care to prevent such outbreaks in the future.

Threshold temperature of superfluorescence generation in CuCl quantum dots under resonant excitation of excitons and resonant two-photon excitation of biexcitons

We studied the threshold temperature of superfluorescence (SF) generation with regard to biexcitons in CuCl quantum dots (QDs) under resonant two-photon excitation of biexcitons and resonant excitation of excitons to demonstrate the influence of initial population densities in the QDs on SF generation. As a result, the threshold temperature under the resonant excitation of excitons was higher than that under the two-photon excitation of biexcitons. This indicates that the high density of excited dots facilitates the rapid establishment of coherence among the dots, overcoming disadvantages of incomplete population inversion and formation process of biexcitons. We performed a theoretical calculation of the time profiles of the biexcitonic emission based on semiconductor luminescence equations. The experimentally obtained temperature dependence of the time profiles was qualitatively reproduced by calculating their dependence on the dephasing rate. In addition, we estimated the temperature dependence of the phase relaxation time of the biexcitons in the CuCl QDs by analyzing the temperature dependence of SF.

Relative numerosity is constructed from size and density information: Evidence from adaptation.

To dissociate aftereffects of size and density in the perception of relative numerosity, large or small adapter sizes were crossed with high or low adapter densities. A total of 48 participants were included in this preregistered design. To adapt the same retinotopic region as the large adapters, the small adapters were flashed in a sequence so as to "paint" the adapting density across the large region. Perceived numerosities and sizes in the adapted region were then compared to those in an unadapted region in separate blocks of trials, so that changes in density could be inferred. These density changes were found to be bidirectional and roughly symmetric, whereas the aftereffects of size and number were not symmetric. A simple account of these findings is that local adaptations to retinotopic density as well as global adaptations to size combine in producing numerosity aftereffects measured by assessing perceived relative number. Accounts based on number adaptation are contraindicated, in particular, by the result of adapting to a large, sparse adapter and testing with a stimulus with a double the density but half number of dots.

Neighborhood mobility and racial disparities in preterm birth: A sibling study in California

Recent work finds that upward neighborhood mobility—defined as reductions in neighborhood socioeconomic disadvantage due to moving—may improve birth outcomes. Less work, however, explores whether changes in socioeconomic context differentially impact birth outcomes by maternal race and ethnicity. In the US, mothers of minoritized racial and ethnic identity often experience worse neighborhood conditions and pregnancy outcomes than White mothers. Using a sibling-linked dataset, we examined whether neighborhood mobility corresponds with changes in preterm birth risk among Asian (N = 130,079), Black (N = 50,149), Hispanic (N = 429,938), and White (N = 233,428) mothers who delivered multiple live births in California between 2005 and 2015. We linked residential addresses at each birth to census-derived indices of neighborhood disadvantage and defined levels of neighborhood mobility as moving-induced changes in disadvantage between pregnancies. We mapped neighborhood mobility patterns and fit conditional logistic regression models estimating the odds of preterm birth in the sibling delivered after moving, controlling for the risk of preterm birth in the sibling delivered before moving, by maternal race and ethnicity. Dot density maps highlight racialized patterns of neighborhood mobility and segregation between Black and White mothers. Regression results show that Black and, in some cases, Asian and Hispanic mothers who experienced upward mobility (moves away from neighborhood disadvantage) exhibited reduced odds of preterm birth in the second delivery. Upward mobility did not reduce the odds of preterm birth among White mothers. Findings suggest that policies and programs that enable opportunities for neighborhood mobility may reduce persistent racial and ethnic disparities in adverse birth outcomes.

Exploring tactile identification accuracy through advanced braille embossers: The dynamic combination of dot density and dot elevation

Exploring tactile identification accuracy through advanced braille embossers: The dynamic combination of dot density and dot elevation

Two new species of the armored catfish genus Panaqolus (Siluriformes, Loricariidae) from the Ecuadorian Amazon

Currently four described species of genus Panaqolus have been reported from the Amazon River basin in Ecuador: P. albomaculatus (Kanazawa 1958), P. dentex (Günther 1868), P. gnomus (Schaefer & Stewart 1993) and P. nocturnus (Schaefer & Stewart 1993). Revision of specimens deposited at the fish collection of Museo de la Escuela Politécnica Nacional (MEPN), Quito, indicated the presence of two additional species, both new to science: P. orcesi n. sp. and P. pantostiktos n. sp. The new species are similar to each other, and to P. albomaculatus and P. nix Cramer & Rapp Py-Daniel 2015 in having the head, body, and fins covered with light dots. Diagnostic characters comprise differences in color pattern, including size and density of light dots on head, body, and fins; as well as various morphometric characters. Apparently, both new species reach larger sizes than previously described species of Panaqolus. The two new species can be included in the subgenus Panafilus (Lujan et al. 2017); they come from the Tigre and Napo River basins, two isolated tributaries in the western Amazon.

Effect of changing the growth mechanism on the synthesis of two-dimensional germanium layers and quantum dots on silicon

Subject of study. The work studied the formation of germanium quantum dots on silicon with (100) crystallographic orientation under different growth regimes. Aim of study. The work is devoted to conducting experimental studies of the influence of growth mechanisms on the formation of germanium layers and quantum dots on a silicon (100) substrate for the production of optical elements based on silicon-germanium nanostructures. Methods. After pre-epitaxial cleaning of the Si substrate, germanium is synthesized on Si(100) through molecular beam epitaxy. The surface morphology is analyzed using reflection high-energy electron diffraction during synthesis and scanning electron microscopy after deposition. Main results. The work determines the temperature ranges at which the Si/Si(100) growth occurs due to the nucleation of islands, due to the movement of steps, and in combination. The effect of changing growth mechanisms on the size and density of Ge quantum dots on Si(100) is shown. Practical significance. The research results provide insight into the influence of growth mechanisms on the sizes of formed germanium quantum dots on silicon, which will make it possible to create nanophotonics and nanoelectronics elements with strictly specified parameters.

Optical properties of InGaP(As) quantum dots in GaAs/AlGaAs/InGaP/InGaAs heterostructures

Subject of study. InGaP(As) quantum dots in GaAs/AlGaAs/InGaP/InGaAs heterostructures were studied. Aim of study. The aim was to establish the correlation between the maximum photoluminescence wavelength of InGaP(As) semiconductor quantum dots and the location of InGaAs quantum wells within GaAs/AlGaAs/InGaP/InGaAs heterostructures. Method. InGaP(As) quantum dots were synthesized by molecular-beam epitaxy; phosphorus was replaced with arsenic in a thin InGaP layer during the epitaxial growth. The optical properties of these InGaP(As) quantum dots were investigated using photoluminescence spectroscopy. Main results. The results show that using an InGaAs quantum well and the formation surface for the InGaP layer, which is subsequently transformed into quantum dots, does not affect the maximum photoluminescence wavelength of the quantum dots. However, the photoluminescence peaks under a long-wave shift of 56 nm when the quantum dots are overgrown with a 5-nm-thick InGaAs quantum well with an InAs molar fraction of 0.17. The measured surface density of the quantum dots is 1.3×1012cm−2. Practical significance. The results obtained from the analysis of the optical properties of the synthesized InGaP(As) quantum dots will serve as a foundation for the fabrication of active regions for near-infrared light sources.

Comparison of bleb morphologies between phacoemulsification combined with Ex-PRESS mini shunt implantation, phacotrabeculectomy and trabeculectomy alone: a two-year retrospective in vivo confocal microscopy study

BackgroundTo compare the bleb morphologies of phacoemulsification combined with Ex-PRESS implantation (Phaco-ExPRESS), phaco trabeculectomy (Phaco-Trab), and trabeculectomy (Trab) in postoperative two years.MethodsPatients with primary open-angle glaucoma (POAG) with or without cataracts were included in this study. All patients underwent surgeries of either Phaco-ExPRESS, Phaco-Trab, or Trab. The morphologic structures of the filtering bleb, including microcysts area, hyperreflective dot density, and stromal connective tissue under in vivo confocal microscope (IVCM), were compared between the three groups. The data were collected preoperatively and postoperatively at 2 weeks, 1 month, 3 months, 6 months, 12 months, 18 months, and 24 months.ResultsEighty-nine eyes from 89 patients were enrolled, including 32 in the Phaco-ExPRESS group, 25 in the Phaco-Trab group, and 32 in the Trab group. In a 24-month follow-up, bleb morphologies in Phaco-ExPRESS were similar to the Trab group. The area of epithelial microcysts was significantly increased in Phaco-ExPRESS and Trab groups while significantly decreased in Phaco-Trab. At postoperative 24 months, the complete success rate was 65.1% in Phaco-ExPRESS, 32.0% in Phaco-Trab, and 59.4% in the Trab group (P = 0.03). The phaco-Trab group had more postoperative anti-glaucoma medications than the other two groups (P < 0.05).ConclusionsPhaco-ExPRESS group and Trab group had similar blebs morphologies in IVCM, with larger microcyst area, looser connective tissue, and less inflammation than Phaco-Trab, indicating that the function of blebs in the Phaco-ExPRESS and Trab group, was more potent than that of Phaco-Trab. All these surgical methods provided adequate IOP control, but Phaco-Trab required more anti-glaucoma medications.

Service Characteristic Evolution of 3D Four‐Directional Braided C/SiC Ceramic Matrix Composites Under Space Electron Radiation Erosion Environment

The specific effects on the evolution of microstructure, components, and mechanical properties of the 3D braided C/SiC composites under different‐time electron irradiation environment tests are analyzed and discussed to elaborate the corresponding corrosion damage mechanism. The damage to the C/SiC composites is intensified by the continuous electron irradiation, the areas of surface bulges and cracks are significantly enlarged, and the surface roughness increases. The density of white dots on the surface of the specimen increased as the electron irradiation time is prolonged, while the size does not change significantly, and the oxygen content on the surface of the specimen increases to some extent. With the prolongation of electron irradiation time, the decrease of bending strength of C/SiC composites increases, but does not level off after a certain degree, probably because of the existence of certain pores on the surface layer of the C/SiC composite. With the increase of electron radiation time, the crack defects on the surface layer of the C/SiC composite increase, and the electron radiation further damages the internal matrix and reinforcing fibers in the C/SiC composite; thus, the mechanical properties decline continuously and seriously after the radiation exceeds 1 h.

Multi-wavelength structured light based on metasurfaces for 3D imaging

Abstract Structured light projection provides a promising approach to achieving fast and non-contact three-dimensional (3D) imaging. The resolution is a crucial index that represents security and accuracy in applications such as face recognition and robot vision. It depends on the density of dots in the projection. However, further improving the density of dots in the current system must be at the cost of speed or volume. Here, an all-dielectric ultra-thin metasurface is designed and fabricated to project a multi-wavelength dot array. The density of dots is improved because projected dots with different wavelengths fill the gaps with each other. The experimental results demonstrate that the multi-wavelength projection improves the resolution of 3D imaging. Furthermore, the multi-wavelength system is beneficial to measuring a surface with varying colors. The approach has the potential to achieve a new generation of high-resolution systems for tiny fluctuations and colorful 3D imaging in dark environments.

Fabrication and characterization of NiCu/GO and NiCu/rGO nanocomposites for fuel cell application.

This study investigated the electrochemical behavior of NiCu, NiCu/GO, and NiCu/rGO nanocomposites designed by combining a modified Hummers' method and hydrothermal technique. The prepared nanocomposites are tested as electrocatalysts in direct alcohol oxidation fuel cells (DAFCs) to identify the role of GO and rGO as catalyst supports for the enhancement of the NiCu composite performance. The production of the NiCu/GO and NiCu/rGO composites was demonstrated by FTIR spectroscopy, EDX, and SEM analyses. In DAFCs experiments, NiCu/rGO has better catalytic activity than pure NiCu and NiCu/GO composites, whereas the use of rGO and GO as supports enhances the performance of NiCu by 468.2% and 377.7% in methanol and 255.6% and 105.9% in ethanol, respectively. The higher performance was caused by the increased density of active dots and the combined electronic effects in the designed catalysts. The stabilities of the catalysts and charge carriers' dynamics are studied using chronoamperometry and electrochemical impedance spectroscopy.

Visualization-Driven Illumination for Density Plots.

We present a novel visualization-driven illumination model for density plots, a new technique to enhance density plots by effectively revealing the detailed structures in high- and medium-density regions and outliers in low-density regions, while avoiding artifacts in the density field's colors. When visualizing large and dense discrete point samples, scatterplots and dot density maps often suffer from overplotting, and density plots are commonly employed to provide aggregated views while revealing underlying structures. Yet, in such density plots, existing illumination models may produce color distortion and hide details in low-density regions, making it challenging to look up density values, compare them, and find outliers. The key novelty in this work includes (i) a visualization-driven illumination model that inherently supports density-plot-specific analysis tasks and (ii) a new image composition technique to reduce the interference between the image shading and the color-encoded density values. To demonstrate the effectiveness of our technique, we conducted a quantitative study, an empirical evaluation of our technique in a controlled study, and two case studies, exploring twelve datasets with up to two million data point samples.

Monocular and binocular mechanisms detect modulations of dot density and dot contrast

Strong reciprocity has been demonstrated between (1) spatial modulations of dot density and modulations of dot luminance, and (2) modulations of dot density and modulations of dot contrast, in textures. The latter are much easier to detect when presented in phase with one another than when presented 180° out of phase, although out-of-phase modulations can also be detected given sufficient amplitude. This result supports the existence of two detection mechanisms: one that is excited by both density modulations and contrast modulations (quiescent when those modulations are presented 180° out of phase) and another that is relatively insensitive to either density modulations or contrast modulations (thus remaining stimulated regardless of phase angle). We investigate whether the mechanism responsible for detecting out-of-phase modulations depends on high-level computations (downstream from the confluence of monocular signals) or whether both mechanisms are situated at the monocular level of visual processing. Specifically, density-modulated and/or contrast-modulated stimuli were presented monocularly (i.e., to the same eye) or dichoptically (i.e., to opposite eyes). Out-of-phase modulations of density were much easier to detect when presented dichoptically. A dichoptic advantage was also found for out-of-phase density and contrast modulations. These dichoptic advantages imply conscious access to a mechanism at the monocular level of processing. When density modulations were presented dichoptically, 180° out of phase, detection thresholds were highest. Consequently, a mechanism with binocular input must also contribute to the detection of these modulations. We describe a minimal, image-based model for these results that contains one monocular computation and one binocular computation.

(Invited) Formation and Characterization of Fe-Silicide Nanodots for Optoelectronic Application

Light emission from group-IV based nanostructures has been attracting much attention in the field of Si-based photonics because of its potential to combine photonic processing with electronic processing on a single chip [1]. Among various Fe-silicides, semiconducting β-FeSi2 shows light emission in the near-infrared region [2, 3] and is one of promising materials in optoelectronic application from viewpoints of tuning emission energy and improving luminous efficiency by means of quantized structures. In this work, we focus on low temperature formation of β-FeSi2 nanodots (NDs) over ~1011 cm-2 in areal density on SiO2 and the characterization of light emission properties of β–FeSi2 NDs.After conventional wet-chemical cleaning steps of p-type Si(100) substrates, a ~300-nm-thick SiO2 layer was grown at 1000°C in dry O2 and followed by dipping shortly in a dilute HF solution to make uniform surface termination with Si-OH bonds. After that, Fe films in the thickness range from 1.0 to 3.0 nm were formed on the OH-terminate SiO2 layer by electron beam evaporation without any extra heating. And then, the Fe–films were exposed to remote plasma of pure H2 (H2-RP) at 400°C to form highly-dense Fe-NDs [4]. Subsequently, so-prepared Fe-NDs were exposed to pure SiH4 at 400°C while controlling the amount of SiH4 exposure by duration and pressure.AFM images taken after exposure of Fe-films to H2-RP confirm the high-density formation of well-defined NDs. In the cases of H2-RP exposure of 1.3-nm-thick and 3.0-nm-thick Fe-films, the areal dot densities as high as ~1.1 × 1011 and ~1.3 × 1011 cm−2 were obtained, respectively, in which the average dot-heights of self-assembled Fe-NDs were determined to be ~5.3 and ~10.9 nm, respectively, by fitting a log-normal function to each measured size distribution. Notice that AFM images taken after SiH4 exposure show almost no change in the areal dot density while a slight increase in the average dot height. From cross-sectional transmission electron microscope images, we have also verified the formation of distorted-spherical shape NDs with a lattice spacing of ~0.18 nm associated with β-FeSi2. And the result is well consistent with the chemical composition of NDs after SiH4 exposure as evaluated by x-ray photoelectron spectroscopy. In addition, with 976 nm light excitation using a semiconductor laser, the NDs after the SiH4 exposure show stable photoluminescence (PL) signals in the energy region from ~0.7 to ~0.9 eV even at room temperature. On the other hand, no PL signals were detected from the NDs before the SiH4 exposure and after Ar anneal at 400°C. Also, when the size of the Fe-silicide NDs was increased from ~5.3 to ~10.9 nm in average dot height by increasing the initial Fe-film thickness, a distinct red-shift in PL was clearly observed. Thus, the observed PL can be interpreted in terms of radiative recombination of photogenerated carriers through quantized states of β-FeSi2 NDs. These results indicate that SiH4 exposure to Fe-NDs formed on SiO2 is a very promising technique for the low-temperature fabrication of luminescent FeSi2 NDs.AcknowledgementThis work was supported in part by Grant-in-Aid for Scientific Research (A) 21H04559 of MEXT Japan, and the Cooperative Research Project Program of the Research Institute of Electrical Communication, Tohoku University.

Modeling of light absorption in self-assembled truncated conical quantum dot structures

Quantum Dots have shown a significant potential as a top candidate for infrared photodetection at higher temperatures. In the presented work, a theoretical model for estimating the coefficient of optical absorption of self-assembled truncated conical quantum dot is developed. This model considers both bound-to-continuum and bound-to-bound absorption mechanisms that increase the accuracy of the absorption coefficient estimation. The developed model is based on estimating the bound states by diagonalizing the Hamiltonian matrix, where the density of states is computed using the Non-Equilibrium Greens function and the effective mass theory to obtain the unbound states. The kinetic equation of Green’s function is solved numerically by finite difference method. Besides, the effects of quantum dot size, height, aspect ratio, and density on the coefficient of the optical absorption are investigated. The results of the developed model are contrasted with those of other alternative QD structures where the truncated conical QD structure results in a higher absorption coefficient in infrared range than semispherical and conical QD structures.

Serial dependencies between form orientation and motion direction are asymmetric.

Much work has been done to uncover the mechanisms underlying form and motion information integration. However, no study examined the symmetry of the integration of form and motion across the temporal domain (i.e., serial dependence). In Experiment 1, we presented form and motion displays sequentially. In the form displays, dot pairs were oriented toward one screen position, indicating the form orientation; in the motion displays, dots moved radially outward. Their motion trajectories were oriented toward one screen position, indicating the motion direction. In each trial, participants reported their perceived form orientation after the form display or their perceived motion direction after the motion display. We found that the current trial's perceived motion direction was biased toward the previous trial's form orientation and vice versa, indicating serial dependencies between form orientation and motion direction. In Experiment 2, we changed the form and motion displays' reliability by varying the two displays' dot densities. The results showed that the serial dependence of form orientation on motion direction perception decreased only with increasing the current motion display's reliability; neither the reliability of the previous motion display nor that of the current form display significantly affected the serial dependence of motion direction on form orientation perception. Hence, serial dependencies between form orientation and motion direction were asymmetric. Our across-temporal integrations between form and motion, together with the simultaneous integration of form and motion revealed in the previous studies, depict a comprehensive mechanism underlying the integration of the two pieces of information.

Inkjet Printing-Manufactured Boron-Doped Diamond Chip Electrodes for Electrochemical Sensing Purposes.

Fabrication of patterned boron-doped diamond (BDD) in an inexpensive and straightforward way is required for a variety of practical applications, including the development of BDD-based electrochemical sensors. This work describes a simplified and novel bottom-up fabrication approach for BDD-based three-electrode sensor chips utilizing direct inkjet printing of diamond nanoparticles on silicon-based substrates. The whole seeding process, accomplished by a commercial research inkjet printer with piezo-driven drop-on-demand printheads, was systematically examined. Optimized and continuous inkjet-printed features were obtained with glycerol-based diamond ink (0.4% vol/wt), silicon substrates pretreated by exposure to oxygen plasma and subsequently to air, and applying a dot density of 750 drops (volume 9 pL) per inch. Next, the dried micropatterned substrate was subjected to a chemical vapor deposition step to grow uniform thin-film BDD, which satisfied the function of both working and counter electrodes. Silver was inkjet-printed to complete the sensor chip with a reference electrode. Scanning electron micrographs showed a closed BDD layer with a typical polycrystalline structure and sharp and well-defined edges. Very good homogeneity in diamond layer composition and a high boron content (∼2 × 1021 atoms cm-3) was confirmed by Raman spectroscopy. Important electrochemical characteristics, including the width of the potential window (2.5 V) and double-layer capacitance (27 μF cm-2), were evaluated by cyclic voltammetry. Fast electron transfer kinetics was recognized for the [Ru(NH3)6]3+/2+ redox marker due to the high doping level, while somewhat hindered kinetics was observed for the surface-sensitive [Fe(CN)6]3-/4- probe. Furthermore, the ability to electrochemically detect organic compounds of different structural motifs, such as glucose, ascorbic acid, uric acid, tyrosine, and dopamine, was successfully verified and compared with commercially available screen-printed BDD electrodes. The newly developed chip-based manufacture method enables the rapid prototyping of different small-scale electrode designs and BDD microstructures, which can lead to enhanced sensor performance with capability of repeated use.

Improvement in Performance of InAs Surface Quantum Dot Heterostructure-Based H2S Gas Sensor by Introducing Buried Quantum Dot Layer

In this work, we have demonstrated InAs surface quantum dot (SQD) based H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S gas sensors. The epitaxial growth of the strain-coupled and uncoupled InAs/GaAs QD heterostructures is done using the solid-source Molecular Beam Epitaxy (MBE) tool. For both types of heterostructures, the coverage of the InAs monolayer (ML) for the SQD layer varies from 0.9 ML to 2 ML. The ML coverage of the buried quantum dots (BQDs) layer for the coupled heterostructures is kept constant (2.7 ML). The atomic force microscopy results demonstrated that the coupled heterostructures have higher quantum dot density in the SQDs layer in comparison to the uncoupled one due to strain propagation from the BQDs towards the SQD layer. The sensor fabricated using the coupled heterostructure with 2 ML SQDs has demonstrated better performance than the uncoupled one for various concentrations (1 ppm -1000 ppm) of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S gas due to inter-dot carrier tunneling between BQDs and SQDs layer. The coupled InAs gas sensor showed the best sensing properties at room temperature (45.9% sensor response @ 100ppm H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S). We have demonstrated the selectivity of the sensor towards H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S among various target gasses like CO, CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O, and NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and the stability over a longer period of time with only 3% deviation (within acceptable limit). These findings have the potential to promote the fabrication of high-performance gas sensors using SQDs-based coupled heterostructures.