Study the structural properties of Ge nanoparticles formed by ion implantation and thermal annealing in nitride-base dielectric matrices

This thesis investigates the formation of Ge nanoparticles (NPs) in amorphous Si3N4 and SiOxNy by ion implantation and thermal annealing. The structural properties of the NPs were determined using a combination of laboratory and synchrotron based techniques including cross-section transmission electron microscopy (TEM), x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), Raman spectroscopy measurements and x-ray absorption spectroscopy (XAS). The motivation for this research is that NPs synthesized from Group IV semiconductors, including Ge, show potential for novel electronic and optoelectronic devices. Ge was chosen as the material for this study, mainly due to its very large bulk exciton Bohr radius (Rb~ 10 nm) and consequently small R/Rb ratio (where R is the NP radius), which increases the quantum confinement regime for optoelectronic applications. Also, Ge NPs embedded in thin dielectric films have exhibited impressive charge storage capabilities, useful in non-volatile memory (NVM) applications. While many studies have focused on the SiO2 matrix, there have been few experimental studies on the growth of Ge NPs in a silicon nitride and silicon oxynitride matrices. The main focus of this project was on the formation of Ge NPs in different Si3N4-based matrices and examining the short range atomic structure of embedded NPs as function of NP size using extended x-ray absorption fine structure (EXAFS). Specifically, four different matrices have considered: PECVD Si3N4, LPCVD Si3N4, PECVD SiO1.67N0.14 and PECVD SiO1.12N0.37. Size evolution and structural properties of NPs were examined as function of implantation conditions and the host matrix. Ge NPs were formed in plasma enhanced chemical vapour deposition (PECVD) Si3N4. Precipitations occurred for Ge concentrations of ≥6 at.%, which suggests the solubility limits of this order. NP size was influenced by Ge concentration and annealing temperature. NP size increased from 2.4 to 4 nm - for samples annealed at 900 ºC for 1 hour- when concentration was increased from 9 to 12 at.%. Moreover, as annealing temperature was increased from 700 to 900 ºC NP size increased from 3 to 4.5 nm (for 12 at.% Ge samples). In general NP diameters were much small compared to SiO2 matrix due to the N content of the system, low diffusivity and large interfacial energy between Ge atoms and Si3N4-based matrices. Unlike PECVD Si3N4, ion beam synthesis of Ge in LPCVD Si3N4 layers resulted in the formation of SiGe NPs. NP size altered from 2.8 to 3.2 nm for 12 at.% Ge concentration samples after annealing temperature was increased from 700 to 900 ºC. Also, NP size increased from 2.3 to 3.2 nm for samples annealed at 900 ºC for 1 hour when Ge concentration was increased from 9 to 12 at.%. Complementary XAS techniques (in particular EXAFS), allowed us a precise and better understanding of the structure of embedded SiGe NPs. Since the lattice difference between Ge and SiGe NPs (less than 4%) could not be distinguished by TEM. A phase transition of the matrix was observed for LPCVD and PECVD Si3N4 matrices after annealing at 1100 ºC. This significantly lowered crystallization temperature of un-implanted layers (1600-1800 ºC). Formation of nanosilicide particles, change of stoichiometry and implantation induced-damage are found to be the most likely causes of crystallization. Ge NPs were formed in SiO1.67N0.14 matrix for different Ge concentrations and annealing temperatures. For Ge concentrations from 9 to 12 at.% annealed at 900 ºC for 1 hour, NP size increased from 3.7 to 4.5 nm. Also, when annealing temperature was increased from 700 to 900 ºC NP size increased from 4.1 to 4.5 for 12 at.% Ge concentration. We observed that slight amount of the N in the system had a significant effect on NP size similar to PECVD Si3N4. Unlike other examined systems, cavities were formed near the implanted region in SiO1.12N0.37 matrix for different concentrations and annealing temperatures, which could be correlated to the matrix structure and composition or vacancy events after ion implantation. The size, origin and properties of formed cavities are subjects of future work. No phase transition (or long-range diffusivity of Ge atoms) was observed for SiOxNy matrices after annealing at 1100 ºC

Is there any putative mediatory role of inflammatory markers on the association between ultra-processed foods and resting metabolic rate?

The resting metabolic rate (RMR) represents the largest component of total daily energy expenditure. The sale of ultra-processed foods (UPF) is increasing globally; however, UPF can have many adverse effects, including increasing inflammatory markers and altering RMRs. This cross-sectional study included 285 healthy overweight and obese women. Anthropometric measurements were evaluated using a bioelectrical impedance analyzer InBody 770 scanner. High-sensitivity C-reactive protein (hs-CRP), plasminogen activator-1 (PAI-1), monocyte chemoattractant protein (MCP-1), and interleukin-1 beta (IL-1β) blood levels were measured after a 12-h fasting. Indirect calorimetry was used to evaluate the RMR by using the Weir equation, and RMR deviation (RMR estimated - RMR actual), RMR per body mass index (BMI), and free fat mass (FFM) were estimated. A validated food frequency questionnaire (FFQ) was used, and seven groups of UPFs were extracted based on the NOVA method. A negative association between the RMR [β = −0.159, 95% confidence interval (CI): −0.471, −0.052, P = 0.044], RMR per BMI (β = −0.014, 95% CI: −0.025, −0.006, P = 0.036), and RMR per FFM (β = −0.241, 95% CI: −0.006, −0.000, P = 0.041) using the NOVA score was observed after adjusting for confounders. This association disappeared after inclusion of each inflammatory marker. All the markers may inversely mediate the relationship between the mentioned variables and the NOVA score. hs-CRP and MCP-1 also had a negative effect on the relationship between the NOVA score and RMR deviation. Finally, UPF intake is likely related with the RMR, mediated through changes in the production of hs-CRP, PAI-1, MCP-1, and IL-1β

The Association of Inflammatory Markers, IL-1α and TGF-β, with Dietary Insulin Load and Dietary Insulin Index in Overweight and Obese Women with Healthy and Unhealthy Metabolic Phenotypes: A Cross-Sectional Study

Context Research has shown IL-1α might play a role in the associations between the MH group and DII and DIL. Objective. We evaluated the association of inflammatory markers, IL-1α and TGF-β, with dietary insulin load and index in women with healthy and unhealthy obesity phenotypes. Materials and Methods. 228 obese/overweight women aged 18–48 years were included in this study. Biochemical factors were obtained from blood samples. Body composition, anthropometric measures, and physical activity assessments were performed. Dietary intakes, DII, and DIL were assessed. Results. Significant associations were observed between the MH group and the DII group (OR = 2.142, 95% CI = 1.421, 2.850, and p = 0.040), in which IL-1α may play a role. Discussion and Conclusion. Significant associations were observed between the MH group and DII. IL-1α might play a role in these associations

Evidence for the formation of SiGe nanoparticles in Ge-implanted Si3N4

SiGe nanoparticles were formed in an amorphous Si3N4 matrix by Ge+ ion implantation and thermal annealing. The size of the nanoparticles was determined by transmission electron microscopy and their atomic structure by x-ray absorption spectroscopy. Nanoparticles were observed for excess Ge concentrations in the range from 9 to 12 at. % after annealing at temperatures in the range from 700 to 900 °C. The average nanoparticle size increased with excess Ge concentration and annealing temperature and varied from an average diameter of 1.8 ± 0.2 nm for the lowest concentration and annealing temperature to 3.2 ± 0.5 nm for the highest concentration and annealing temperature. Our study demonstrates that the structural properties of embedded SiGe nanoparticles in amorphous Si3N4 are sensitive to the implantation and post implantation conditions. Furthermore, we demonstrate that ion implantation is a novel pathway to fabricate and control the SiGe nanoparticle structure and potentially useful for future optoelectronic device applications.We also thank the Australian Research Council and Australian Synchrotron for support

Sensory and Motor Behavior Evidences Supporting the Usefulness of Conditioned Medium from Dental Pulp-Derived Stem Cells in Spinal Cord Injury in Rats

Study Design Experimental animal study. Purpose This study aimed to assess effects of conditioned medium (CM) of dental pulp-derived stem cells loaded in collagen hydrogel on functional recovery following spinal cord injury (SCI). Overview of Literature SCI affects sensory and motor functions, and behavioral recovery is the most essential purpose of therapeutic intervention. Recent studies have reported that CM from dental pulp-derived stem cells has therapeutic benefits. In addition, collagen hydrogel acts as a drug delivery system in SCI experiments. Methods Stem cells from human exfoliated deciduous teeth (SHEDs) were cultured, and SHED-CM was harvested and concentrated. Collagen hydrogel containing SHED-CM was prepared. The rats were divided into five groups receiving laminectomy, compressive SCI with or without intraspinal injection of biomaterials (SHED-CM), and collagen hydrogel with or without SHED-CM. Basso, Beattie, and Bresnahan (BBB) scoring, inclined plane, cold allodynia, and beam walk tests were performed for 6 weeks to assess locomotor, motor, sensory, and sensory-motor performances, respectively. Results Scores of the rats receiving SHED-CM loaded in collagen hydrogel were significantly better than those of the other injured groups at 1-week post-injury for BBB, 2 weeks for inclined plane, 2 weeks for cold allodynia, and 4 weeks for beam walk tests (p <0.05). The differences remained significant throughout the study. Conclusions Intraspinal administration of SHED-CM loaded in collagen hydrogel leads to improved functional recovery and proposes a cell-free therapeutic approach for SCI

Electrical and structural properties of In-implanted Si1−xGex alloys

We report on the effects of dopant concentration and substrate stoichiometry on the electrical and structural properties of In-implanted Si1−xGex alloys. Correlating the fraction of electrically active In atoms from Hall Effect measurements with the In atomic environment determined by X-ray absorption spectroscopy, we observed the transition from electrically active, substitutional In at low In concentration to electrically inactive metallic In at high In concentration. The In solid-solubility limit has been quantified and was dependent on the Si1−xGex alloy stoichiometry; the solid-solubility limit increased as the Ge fraction increased. This result was consistent with density functional theory calculations of two In atoms in a Si1−xGex supercell that demonstrated that In–In pairing was energetically favorable for x ≲ 0.7 and energetically unfavorable for x ≳ 0.7. Transmission electron microscopy imaging further complemented the results described earlier with the In concentration and Si1−xGex alloy stoichiometry dependencies readily visible. We have demonstrated that low resistivity values can be achieved with In implantation in Si1−xGex alloys, and this combination of dopant and substrate represents an effective doping protocol

Determining the Concentration of Particulate Matters and Microbiological Quality of Indoor Air in Intensive Care Units of Kashan Hospital, Iran

Introduction: Maintaining hospital air quality is very important, especially in intensive care units (ICUs), where patients undergo invasive procedures. Therefore, the present study was conducted with the aim of determining the relationship between particulate matters (PMs) and bioaerosols in pediatric ICU (PICU), neonatal ICU (NICU), and ICU open heart (ICU OH) of Shahid Beheshti Hospital in Kashan. Materials and Methods: This cross-sectional study was conducted for six consecutive months, i.e., autumn and winter of 2021. PM samples were taken using a Grimm Dust Monitor and microbial samples were taken using a Quick Take 30 sampler. Kolmogorov-Smirnov test was used for analysis and then ANOVA and LSD were used for further tests. Results: The maximum and minimum PM10 concentrations in the PICU and ICU OH were 59.19 and 9.71 μg/m3, respectively; and the maximum and minimum PM2.5 concentrations were 20.23 μg/m3 in the NICU and 4.69 μg/m3 in PICU. The mean PM concentration and the number of bacterial and fungal colonies were consistent with the WHO and EPA guidelines. Gram-positive Staphylococcus were the most abundant bacteria (90.96%). The most abundant fungi were Aspergillus (54.23%), Penicillium (15.64%), and Cladosperium (12.17%) species. There was also no significant relationship between PMs and bioaerosols. Conclusion: The mean concentrations of PMs and bioaerosols match with the guidelines, which can be attributed to more observance of health protocols and restrictions on the movement of people into ICUs due to the COVID-19 outbreak

EXAFS study of the structural properties of In and In + C implanted Ge

The structural configurations of In implanted Ge have been studied via x-ray absorption spectroscopy with and without the codoping of C. In the case of In singly implanted Ge, while the In atoms occupy an substitutional site in Ge (InGe4) at low In concentration (≤0.2 at. %), they precipitate into a metallic phase (In metal) and form complexes composed of one vacancy and three Ge atoms (InVGe3) at concentration ≥ 0.6 at. %. This behaviour can be suppressed by the addition of C leading to In-C pairing to form InCGe3 complexes. This cluster enables In atoms to recover a four-fold coordinated structure and has the potential to improve the electrical activation of In atoms in Ge.We acknowledge access to NCRIS and AMMRF infrastructure at the Australian National University including the Australian National Fabrication Facility, the Heavy Ion Accelerator Capability and the Center for Advanced Microscopy. We also thank the Australian Research Council and the Australian Synchrotron for support

Enhanced Electrical Activation in In-Implanted Si0.35Ge0.65 by C Co-Doping

In this report, we have achieved a significant increase in the electrically active dopant fraction in Indium (In)-implanted Si0.35Ge0.65, by co-doping with the isovalent element Carbon (C). Electrical measurements have been correlated with X-ray absorption spectroscopy to determine the electrical properties and the In atom lattice location. With C+ In co-doping, the solid solubility of In in Si0.35Ge0.65 was at least tripled from between 0.02 and 0.06 at% to between 0.2 and 0.6 at% as a result of C-In pair formation, which suppressed In metal precipitation. A dramatic improvement of electrical properties was thus attained in the co-doped samples.We also thank the Australian Research Council and Australian Synchrotron for support