Uncapped Samples Research Articles

Charge Distribution across Capped and Uncapped Infinite-Layer Neodymium Nickelate Thin Films.

Charge ordering (CO) phenomena have been widely debated in strongly-correlated electron systems mainly regarding their role in high-temperature superconductivity. Here, the structural and charge distribution in NdNiO2 thin films prepared with and without capping layers, and characterized by the absence and presence of CO are elucidated. The microstructural and spectroscopic analysis is done by scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) and hard X-ray photoemission spectroscopy (HAXPES). Capped samples show Ni1+ , with an out-of-plane (o-o-p) lattice parameter of around 3.30 Å indicating good stabilization of the infinite-layer structure. Bulk-sensitive HAXPES on Ni-2p shows weak satellite features indicating large charge-transfer energy. The uncapped samples evidence an increase of the o-o-p parameter up to 3.65 Å on the thin film top with a valence toward Ni2+ in this region. Here, 4D-STEM demonstrates (303)-oriented stripes which emerge from partially occupied apical oxygen. Those stripes form quasi-2D coherent domains viewed as rods in the reciprocal space with Δqz ≈ 0.24 reciprocal lattice units (r.l.u.) extension located at Q = ( ) and ( ) r.l.u. The stripes associated with oxygen re-intercalation concomitant with hole doping suggest a possible link to the previously reported CO in infinite-layer nickelate thin films.

Investigations on capping-induced changes in structural, optical, and thermal properties of Zn0.96Ni0.04S nanoparticles

We present the chemical precipitation technique for producing several quantities of sodium hexametaphosphate (SHMP) capped zinc sulphide nanoparticles doped with Ni2+ in an ambient environment. The average grain size of the nanoparticles generated was tuned by using SHMP concentration. SEM with EDAX, HRTEM, and SAED patterns was used to confirm the particle size, crystallinity, and composition. Compared to bulk ZnS, UV–Vis spectra of both capped and uncapped samples reveal a blue shift in the absorption edge. FTIR studies confirmed the capping of SHMP on the surface of Ni-doped ZnS. PL spectra of ZnS:Ni2+ nanoparticles exhibit intense and sustained visible-light emissions. The intensity of the blue emission centered at 468 nm increased with increasing SHMP concentration up to 0.75 wt percent but decreased with higher concentrations of SHMP. TG – DTA results show that SHMP – ZnS (Ni-doped) nanoparticles have excellent thermal stability due to improved shape and compactness.

Synthesis of infinite-layer nickelates and influence of the capping-layer on magnetotransport

The recent discovery of a zero-resistance state in nickel-based compounds has generated a re-excitement about the long-standing problem in condensed matter of high-critical temperature superconductivity, in light of the similarities between infinite-layer nickelates and cuprates. However, despite some formal valence and crystal symmetry analogies, the electronic properties of infinite-layer nickelates are remarkably original accounting, among other properties, of a unique Nd 5d-Ni 3d hybridization. This designates infinite-layer nickelates as a new class of oxide superconductors which should be considered on their own. Here we report about Nd1-x Sr x NiO2 (x = 0, 0.05 and 0.2) thin films synthesized with and without a SrTiO3 (STO) capping-layer, showing very smooth and step-terraced surface morphologies. Angle-dependent anisotropic magnetoresistance (AMR) measurements performed with a magnetic field rotating in-plane or out-of-plane with respect to the sample surface, rendered important information about the magnetic properties of undoped STO-capped and uncapped samples. The results point at a key role of the capping-layer in controlling the magnitude and anisotropy of the AMR. We discuss this control in terms of a combined effect between the Nd 5d-Ni 3d hybridization and an intra-atomic Nd 4f-Nd 5d exchange coupling. Further studies foresee the influence of the capping layer on infinite-layer nickelates with no magnetic rare-earth.

Effect of Hydrogen Treatment on Photoluminescence and Morphology of InGaN Multiple Quantum Wells.

In this paper, the photoluminescence (PL) properties and surface morphology of InGaN/GaN multiple quantum well (MQW) structures with the hydrogen (H2) heat treatment of InGaN are investigated to elucidate the effect of hydrogen on the structure and surface of the MQWs. The experimental results show that the H2 heat treatment on the as-grown MQWs may lead to the decomposition of InGaN and the formation of inhomogeneous In clusters. The atomic force microscope (AFM) study indicates that although the surface roughness of the uncapped samples increases after H2 treatment, the V-defects are suppressed. Moreover, the luminescence efficiency of the MQWs can be effectively improved by growing a GaN cap layer with an appropriate thickness on the top of the MQWs, which can reduce the effects of the H2 atmosphere and high temperature on the MQWs. In addition, a morphologic transformation from step bunching to shallow steps occurs and a much smoother surface can be obtained when a thicker cap layer is adopted.

Synthesis, characterization, and in vitro DPPH radical scavenging assay study of PEG-capped carbon nanoparticles derived from Butea monosperma flower extract

In this work, the core carbon nanoparticles (BM CNs) and polyethylene glycol 400 (PEG400)-capped BM CNs were synthesised from Butea monosperma flower extract via the facile direct heating method. They were investigated for their intriguing properties and in vitro antioxidation activity in comparison with Carica papaya seed (CPS) extract via DPPH assay. The CNs were characterised by DLS, XRD, HR-TEM, TGA, FT-IR, UV–vis spectral analysis and quantum yield measurement. The PEGylated CNs demonstrated decent quantum yield, favourable size, and turbostratic carbon phase apart from better stability and dispersion nature as compared to the uncapped entity. The mildly stable uncapped sample with zeta potential −17.9 mV featured its extensively aggregated form, unlike the capped sample with −23.0 mV zeta potential, which sheds light on its enhanced stability by PEG400. Antiradical capacities of the CNs in comparison with CPS extract demonstrated the PEG400-bound nanomaterial of its superior antiradical activity against the other two controls. This study provides an insight into the novel polymer-CNs’ potent antioxidant property which can be further explored for its incorporation in targeted drug delivery and other biomedical applications.

Effect of polyethylene glycol capping on structural, optical and thermal properties of ZnS:Ni2+ nanoparticles

To study the effect of polyethylene glycol capping on structural, optical and thermal properties, ZnS:Ni2+ nanoparticles have been prepared by chemical precipitation method. It is demonstrated that by varying the concentration of PEG the particle size can be varied within ∼3.58 to 12 nm. To analyze the samples of nanostructures, the samples are subjected to X-ray diffraction, Field emission scanning electron microscopy and High resolution transmission electron microscopy characterization techniques. The spectral bands between 673 and 494 cm−1 are related to Zn-S stretching vibrations which was confirmed by Fourier transform infrared spectral studies. It is found that the uncapped sample emits strong UV light, whereas the capped samples exhibit strong and broad visible emission. An enhancement of fluorescence intensity has been obtained, in a capped sample with the minimum particle size and thus with more defect centers, in comparison to that of uncapped one.

Correlation between the structure and luminescence of InAs submonolayer stacked nanostructures

The correlation between the structure, measured by atomic force microscopy (AFM), and luminescence, measured by photoluminescence (PL), of InAs submonolayer stacked (SMLS) nanostructures near the 2D to 3D transition is investigated. Topographic measurements using AFM reveal a significant change in the structure of uncapped InAs SMLS samples occurs under certain conditions. This structural change is attributed to the transition from 2D to 3D growth. Optical measurements by PL of corresponding capped SMLS samples showed a significant change in the luminescence properties, in the form of significant redshift and linewidth broadening, also occurs at the same conditions where the structural change occurred. Therefore, the data in the present work establishes a strong correlation between the structural and luminescence properties of InAs SMLS nanostructures. Furthermore, the results demonstrate that two forms of InAs SMLS, stacked 2D islands and 3D structures, possess distinct properties in terms of both structure and luminescence.

Non Destructive Evaluation of AlGaN/GaN HEMT structure by cathodoluminescence spectroscopy

We have investigated radiative defects in various component layers in an AlGaN/GaN HEMT structure by measuring Cathodoluminescence (CL) spectrum as a function of accelerating voltage. Low electron beam accelerating voltages (below 1 kV) CL spectra are used to get information about defects in the cap layer and the barrier layer. Samples with good quality GaN cap layer showed surface quantum well (SQW) transition in the CL spectrum. The cap layer thickness and its quality can be determined from the SQW emission energy and its integrated intensity. We show that low intensity electron beam provides information about the defects in the cap layer as well as barrier layer through the intensity and energy of the yellow luminescence peak. The observed changes in the CL intensity of the barrier layer towards the surface have been correlated to the formation of aluminium oxide, giving rise to higher concentration of deep acceptor defects probably related to the adsorbed oxygen on the uncapped AlGaN barrier layer samples. The results are supported by X-ray photoelectron spectroscopy (XPS), High resolution X-ray diffraction (HRXRD) and Secondary ion mass spectrometry (SIMS) techniques.

Sub-nm Near-Surface Activation Profiling for Highly Doped Si and Ge Using Differential Hall Effect Metrology (DHEM)

Contact resistivity at the metal-semiconductor interface is a strong function of the carrier concentration in the near surface. For next generation 2D/3D MOSFET transistors, industry has been investigating very highly doped materials (>1x1021cm-3) approaching alloy concentrations in Silicon and various Silicon-Germanium materials. All the while, contact development in Ge NMOS has favored co-doping approaches. Regardless of the material system, it is very important to accurately measure near-surface dopant activation. In this paper, we use Differential Hall Effect Metrology (DHEM) implemented on the ALPro™ tool to characterize the activation profiles in both materials. The method employs electrochemical means of reducing the electrically active thickness of a semiconductor film and determining the sheet resistance and mobility of the thinned down layer using Van der Pauw/Hall effect type measurements. By repeating this process and using differential equations, depth profiles of mobility and carrier concentration are obtained [1] at sub-nm resolutions.It is difficult to achieve high n-type dopant activation in Ge. Point defects in Ge are known to behave as acceptor sites and reduce the overall free electron density, particularly near the surface. Minimization of these defects is essential to achieving high performance Ge NMOS. Accurate analysis of dopant activation within 5 nm of the surface is critical to understanding effectiveness of various process steps on improving contact resistance. We have previously published a study on the effect of Ge co-doping with Sb and P on near-surface dopant activation. In Ge with only P-doping it was found that only ~5x1018cm-3 or 5% of the total surface dopants (~1x1020cm-3) were electrically active. With Sb as a co-dopant, the active electron concentration increased to ~2x1019cm-3 with a similar P chemical concentration. Prior work has shown similar increases in activation with co-doping but did not capture the significant decrease in electron concentration by 4x within 10 nm of the surface. Here, we further study the effects of the implantation and annealing processes on near-surface dopant activation in n-type Ge. Samples were prepared by growing 3 µm thick epi-Ge layers on Si substrates. Sample 1 was capped with 20 nm SiO2 and Sample 2 was capped with 20 nm Al2O3 to minimize implant damage and control implant depth. Both samples were implanted first with Sb (dose: 6x1014cm-2, energy: 65 keV) followed by P (dose: 6x1014cm-2, energy: 90 keV). Post-implant anneal was done at 500°C for 10 s in N2 to activate the dopants. ALProTM and SIMS measurements were done to characterize active dopant concentration and total chemical dopant concentration, respectively. The Al2O3 capped sample (Sample 2) showed significantly lower carrier concentration than the SiO2 capped sample (Sample 1) throughout the depth of the profile (Figure 1). Carrier concentration at the surface was lower by nearly an order of magnitude, decreasing from ~2x1019cm-3 to ~2x1018cm-3. Additionally, the peak concentration decreased from 1x1020cm-3 to 5x1019cm-3 at a depth of ~30 nm in both cases. The variations in the carrier profile for the Al2O3 capped sample also indicate greater process variation. SIMS profiles show that there is significant diffusion of Al into the Ge matrix after implant and anneal. Al chemical concentration is 1x1020cm-3 at the Ge surface and steadily decays up to a depth of more than 300 nm. This indicates that there is significant damage caused during the implantation process and the activation anneal is not enough to remove these defects. Al atoms then diffuse from the Al2O3 capping layer into the highly defective Ge substrate. Al is a p-type dopant in Ge and counter-dopes the Sb and P implants to reduce overall electron concentration in Sample 2. It is important to note the high resolution DHEM technique was able to resolve this important phenomenon right near the surface of the material.Additionally, we present early data on very highly phosphorus-doped (~1x1021cm-3) epitaxial silicon thin films grown on Si substrates. In very highly doped Silicon materials, the effect of near-alloy levels of dopant in the matrix on dopant deactivation is not well-known. Samples were obtained with different levels of dopant concentration above ~1x1021cm-3and different anneal temperatures. It was found that near-surface activation in these un-capped samples led to a lowering of activation in the <20nm region from the surface. Extensive post-DHEM metrology (using TEM and SIMS analysis) will also be presented demonstrating control and precision of DHEM data.

Cryogelation of Human Hair Keratins

Human hair keratins (HHK) are known for their biocompatibility and potential to regulate cell response, possibly due to the presence of the leucine-aspartic-valine cell adhesion and signaling motifs. Together with the abundance of cysteine residues in HHK, 3D HHK scaffolds are fabricated through cryogelation based on spontaneous disulfide crosslinks and noncovalent interactions. Herein, the molecular mechanism of HHK self-assembly during cryogelation is interrogated and the influence of cryogelation parameters on the properties of the resultant scaffolds is studied. With successive freeze-thaw cycles, the storage modulus (G') of HHK cryogels substantially improves from 116.4 Pa at freeze-thaw cycle 3 (FT3) to 1908.7 Pa at freeze-thaw cycle 10 (FT10). Meanwhile, it is found that complete thiol-capping of HHK samples significantly inhibits cryogel formation as compared to partially or uncapped HHK samples, suggesting the dominant role of disulfide stabilization in cryogelation. Finally, uniaxial compression tests on HHK sponges demonstrate that FT cycling, from 0 to 10, is able to improve the compression modulus of sponges by ≈12-folds. These findings show that macroscale properties of HHK cryogels can be conveniently modulated by physical parameters of cryogelation and that disulfide bonding is the main stabilizing force in HHK cryogels.

Epitaxial growth of a silicon capping layer to mitigate roughness after the selective chemical etching of Si1-xGex

The gate-all-around structure is a promising candidate for future generations of advanced metal-oxide semiconductor field-effect transistor technologies, as it provides higher drive current and low-power operation. The commonly-suggested nanowire structure uses a selective etching technique in the silicon/silicon-germanium multilayer to reveal the channel area. The revealed Si surface is rough, however, due to the missing atoms and remnants of Si1-xGex. This leads to increased interfacial state density, which degrades device performance, such as subthreshold voltage swing. Regarding the usage of high-k metal gates on the channel area, the issue of this rough surface, and the subsequent increase of the dangling bonds after etching, should be properly addressed.In this study, we report the enhanced roughness and density of interface state by applying a Si capping layer. The epitaxial Si0.87Ge0.13 layer, with a thickness of 30 nm on the Si substrate, was removed by an etchant consisting of nitric acid, hydrofluoric acid, and acetic acid, after which a 1-nm thick Si capping layer was epitaxially grown onto the surface. Atomic Force Microscopy was used to measure the roughness, and X-ray Photoelectron Spectroscopy was conducted to characterize the atomic bonds on the surface. A 10-nm thick SiO2 film was deposited using the Atomic Layer Deposition process to characterize the capacitance-voltage curve and interface trap density. The Si-capped sample exhibited half of the surface roughness of the un-capped sample, and exhibited a 30% lower interface trap density, by mitigating the impact of wet etching.

A Study of the Structural, Morphological and Luminescence Characteristics of Polyvinyl Pyrrolidone and Chitosan Capped Calcium Sulfide Nanoparticles

Semiconductor nanoparticles have gained impressive attention due to their novel optical and electronic properties. Here we report the synthesis of calcium sulfide (CaS) nanophosphors through a simple wet chemical co-precipitation method using two different capping agents polyvinyl pyrrolidone (PVP) and chitosan. The role of capping agents in determining the particle size, morphology and luminescence of CaS nanoparticles was determined using X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), room temperature Photoluminescence (PL), UV-Vis spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. XRD studies confirmed that the nanoparticles were crystallized in cubic phase with space group 3 Fm m. PL emission spectra of the capped samples consisted of broad peaks in the range 350-500 nm with enhanced PL intensity compared to that of uncapped sample. An increase in bandgap was observed due to capping which may be attributed to size quantization effects. Capped nanoparticles showed better structural and optical properties compared to uncapped samples which can be exploited in various optoelectronic and biomedical applications.

Study on the role of growth time on structural, morphological and optical properties of un-capped and L-cyst.-capped ZnO nanorods grown on a GZO seeded thin film layer from an aqueous solution

The influence of the deposition time (ranging from 30 to 300 min) and the role of l-cysteine on the structural and optical properties of the un-capped and L-cyst.-capped ZnO nanorods (ZNRs) grown using the chemical bath deposition method was discussed. X-ray diffraction patterns showed that the estimated crystallite size increased with the deposition time up to 240 min for both capped and un-capped samples, while the calculated strain was found to decrease to a minimum for the 240 min deposition time. The Fourier transform infra-red spectroscopy of the as-grown ZNRs films showed various absorption bands in the range of 250–4000 cm-1 indicating the presence of different functional groups. Scanning electron microscopy analysis illustrated that the aspect ratios of the L-cyst.-capped ZNRs increased six-fold as the growth duration varied from 30 to 240 min, but decreased slightly at longer growth time. The root mean square roughness increased continuously from 10.9 to 36.3 nm as the growth time was raised from 30 to 240 min for the un-capped ZNRs. The samples deposited at 240 min exhibited the highest photoluminescence emission intensity ratios suggesting a low density of deep level defects. An inverse relation between the optical band gaps and growth time was observed. The highly luminescent cyst.-capped sample, with well-aligned nanorods and highest aspect ratio and good crystallization grown at 240 min growth time can be used as a possible photoanode component of dye-sensitized solar cells.

A comparative study of epitaxial InGaAsBi/InP structures using Rutherford backscattering spectrometry, X-ray diffraction and photoluminescence techniques

In this work, we used a combination of photoluminescence (PL), high resolution X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) techniques to investigate material quality and structural properties of MBE-grown InGaAsBi samples (with and without an InGaAs cap layer) with targeted bismuth composition in the 3%–4% range. XRD data showed that the InGaAsBi layers are more homogeneous in the uncapped samples. For the capped samples, the growth of the InGaAs capped layer at higher temperature affects the quality of the InGaAsBi layer and bismuth distribution in the growth direction. Low-temperature PL exhibited multiple emission peaks; the peak energies, widths, and relative intensities were used for comparative analysis of the data in line with the XRD and RBS results. RBS data at a random orientation together with channeled measurements allowed both an estimation of the bismuth composition and analysis of the structural properties. The RBS channeling showed evidence of higher strain due to possible antisite defects in the capped samples grown at a higher temperature. It is also suggested that the growth of the capped layer at high temperature causes deterioration of the bismuth-layer quality. The RBS analysis demonstrated evidence of a reduction of homogeneity of uncapped InGaAsBi layers with increasing bismuth concentration. The uncapped higher bismuth concentration sample showed less defined channeling dips suggesting poorer crystal quality and clustering of bismuth on the sample surface.

Characterization of Zinc Ferrite Nanoparticles Capped with Different PVP Concentrations

The effects of polyvinyl pyrrolidone (PVP) as a capping agent on the structure, morphology, magnetic hysteresis (M–H) loop, optical and dielectric properties of ZnFe2O4 nanoparticles synthesized by a co-precipitation method were investigated. The precursors used during preparation were FeCl3·6H2O, ZnCl2, and 4 M NaOH with different concentrations of PVP: 0 (pure sample), 0.35 × 10−3 M, 0.69 × 10−3 M, 1.03 × 10−3 M, and 1.38 × 10−3 M. The prepared samples were characterized and investigated using x-ray powder diffraction (XRD), transmission electron microscope (TEM), UV–visible optical spectroscopy, Fourier transform infrared (FTIR), magnetic hysteresis (M–H), and dielectric measurements. XRD patterns reveal a face-centered cubic structure for ZnFe2O4 and confirm that the lattice parameter decreases as the PVP concentration increases. TEM results reveal some aggregation of nanoparticles and a decrease in crystallite size with increasing PVP addition. The energy gap (Eg) increases with an increase of PVP concentration, confirming the decrease of crystallite size as the PVP concentration increases. The FTIR results indicate that PVP addition induces a blue shift with slight variations in the wavelengths of the metal oxide bands. M–H results show that the uncapped PVP sample exhibits ferromagnetic behavior that changes to superparamagnetic with PVP addition up to 1.03 × 10−3 M, along with an increase in the saturation magnetization Ms. The coercivity Hc increases up to a PVP concentration of 0.35 × 10−3 M, and then decreases up to a PVP concentration of 1.03 × 10−3 M. The dielectric constant and dielectric loss measured at room temperature decrease when increasing the frequency, but increase when increasing the temperature or PVP concentration. These results indicate that there is a critical amount of PVP that must be added in order to control the properties of ZnFe2O4 nanoparticles to use them for dielectric and magnetic applications.

Hexagonal MoTe2 with Amorphous BN Passivation Layer for Improved Oxidation Resistance and Endurance of 2D Field Effect Transistors

Environmental and thermal stability of two-dimensional (2D) transition metal dichalcogenides (TMDs) remains a fundamental challenge towards enabling robust electronic devices. Few-layer 2H-MoTe2 with an amorphous boron nitride (a-BN) covering layer was synthesized as a channel for back-gated field effect transistors (FET) and compared to uncovered MoTe2. A systematic approach was taken to understand the effects of heat treatment in air on the performance of FET devices. Atmospheric oxygen was shown to negatively affect uncoated MoTe2 devices while BN-covered FETs showed considerably enhanced chemical and electronic characteristic stability. Uncapped MoTe2 FET devices, which were heated in air for one minute, showed a polarity switch from n- to p-type at 150 °C, while BN-MoTe2 devices switched only after 200 °C of heat treatment. Time-dependent experiments at 100 °C showed that uncapped MoTe2 samples exhibited the polarity switch after 15 min of heat treatment while the BN-capped device maintained its n-type conductivity for the maximum 60 min duration of the experiment. X-ray photoelectron spectroscopy (XPS) analysis suggests that oxygen incorporation into MoTe2 was the primary doping mechanism for the polarity switch. This work demonstrates the effectiveness of an a-BN capping layer in preserving few-layer MoTe2 material quality and controlling its conductivity type at elevated temperatures in an atmospheric environment.

Density Control of InP/GaInP Quantum Dots Grown by Metal-Organic Vapor-Phase Epitaxy

We investigated structural and emission properties of self-organized InP/GaInP quantum dots (QD) grown by metal organic chemical vapor deposition using an amount of deposited In from 7 to 2 monolayers (ML). In the uncapped samples, using atomic force microscopy (AFM), we observed lateral sizes of 100–200 nm, together with a bimodal height distribution having maxima at ∼5 and ∼15 nm, which we denoted as QDs of type A and B, respectively; and reduction of the density of the type-B dots from 4.4 to 1.6 μm–2. The reduction of the density of B-type dots were observed also using transmission electron microscopy of the capped samples. Using single dot low-temperature photoluminescence (PL) spectroscopy we demonstrated effects of Wigner localization for the electrons accumulated in these dots.

The effect of different thickness alumina capping layers on the final morphology of dewet thin Ni films

Nanoparticles on a substrate have numerous applications in nanotechnology, from enhancements to solar cell efficiency to improvements in carbon nanotube growth. Producing nanoparticles in a cost effective fashion with control over size and spacing is desired, but difficult to do. This work presents a scalable method for altering the radius and pitch distributions of nickel nanoparticles. The introduction of alumina capping layers to thin nickel films during a pulsed laser-induced dewetting process has yielded reductions in the mean and standard deviation of radii and pitch for dewet nanoparticles with no noticeable difference in final morphology with increased capping layer thickness. The differences in carbon nanotube mats grown, on the uncapped sample and one of the capped samples, is also presented here, with a more dense mat being present for the capped case.

Integrity of Uncapped Routine Coagulation Specimens Processed in an Automated Integrated Laboratory.

The validity of laboratory results depends on pre-analytical variables not detected by conventional quality control. Recommendations are for post-centrifugation coagulation samples to remain capped with cappiercing primary tube analysis. Total laboratory automation integrates analytical platforms with potential incompatibilities necessitating changes including pre-analytical uncapping of samples. Samples analyzed for Prothrombin Time (PT), activated Partial Thromboplastin Time (aPTT), D-dimers, Antithrombin and Fibrinogen at baseline, and after 60 and 120 minutes were left at ambient temperature, either re-capped or uncapped, in order to simulate changes from baseline that could occur in uncapped samples on an automation track prior to analysis. Changes were compared to the maximal permissible bias. Sample uncapping for up to 120 minutes at ambient temperature post-centrifugation did not result in clinically significant changes in routine coagulation parameters. Routine coagulation parameters will not change significantly if the primary citrate tubes are uncapped after centrifugation prior to analysis.

Density control of InP/GaInP quantum dots grown by metal-organic vapor-phase epitaxy

AbstractWe investigated structural and emission properties of self-organized InP/GaInP quantum dots (QD) grown by metal organic chemical vapor deposition using an amount of deposited In from 7 to 2 monolayers (ML). In the uncapped samples, using atomic force microscopy (AFM), we observed lateral sizes of 100–200 nm, together with a bimodal height distribution having maxima at ∼5 and ∼15 nm, which we denoted as QDs of type A and B, respectively; and reduction of the density of the type-B dots from 4.4 to 1.6 μm^–2. The reduction of the density of B-type dots were observed also using transmission electron microscopy of the capped samples. Using single dot low-temperature photoluminescence (PL) spectroscopy we demonstrated effects of Wigner localization for the electrons accumulated in these dots.