Minimum Width Research Articles

Quantitative assessment of ramal bone width and the proximity of the inferior canal for the predictable insertion of ramal implants: Cone-beam computed tomography study

Objectives: The study aimed to investigate the optimum level for the placement of ramal implants as a source of anchorage for disimpacting mandibular molars. The criteria in relation to the maximum transverse width of the ramal bone and proximity of the implant to the inferior alveolar canal (IAC) were evaluated using a three-dimensional cone-beam computed tomography scan for predictable placement of ramal implants. Material and Methods: The cone-beam computed tomographic scans of 53 untreated patients (aged between 18 and 48 years) were utilized in this study. The maximum transverse width of the ramus and the proximity to the IAC from the site of insertion were measured at six different levels above the central groove of the mandibular first molar. To measure the proximity to the IAC, the mid-point of the maximum transverse width of the ramus was selected as the site of insertion of the implant. Results: The maximum and minimum transverse ramal width was 12.48 ± 1.76 mm at 3 mm and 10.42 ± 2.08 mm at 8 mm above the central groove of the permanent mandibular first molar. An average clearance of 9.62 ± 2.59 mm was measured from the site of insertion to the IAC at the different levels evaluated. Conclusion: The ramus of the mandible can be a predictable site for implant placement provided the variations in the anatomical structures have been carefully analyzed. It can be concluded that the ramal implants can be safely placed at a level 3–8 mm above the permanent mandibular first molar in relation to the occlusal plane.

Corrigendum

Corrigendum

Evaluation of different food waste for sustainable mass rearing of black soldier fly (Hermetia illucens L) in Bangladesh

Black solider fly (BSF) (Hermetia illucens L) is one of the potential organic protein sources which is utilised as feed for fish and poultry industries. Effective mass rearing of BSF is inevitable for future sustainable feed industries in Bangladesh. Therefore, this research was aimed at developing the sustainable mass rearing techniques for this insect’s larvae on different available food waste materials in the Bangladesh context. The study was conducted using different household waste, i.e. Rice-Fruit-Meat; Rice-Fruit-Fish; Rice-Vegetable-Meat; Rice-Vegetable-Fish; Rice-Fruit-Vegetable-Meat; and Rice-Fruit-Vegetable-Fish. Larvae reared on Rice-Fruit-Vegetable-Fish diet showed the best results among the treatments in terms of larval growth, i.e. length 23.3±0.1 mm and width 6.2±0.1 mm. The Rice-Fruit-Fish diet showed the minimum larval length (19.5±0.1 mm) and Rice-Fruit-Meat diet showed the minimum larval width (5.6±0.1 mm) compared to the other diets. Among these diets, Rice-Fruit-Vegetable-Fish diet gave the highest larval fresh weight (2.6±0.1 mg) compared to other treatments. In addition, the Rice-Fruit-Vegetable-Fish diet took less time (45.6±0.7 days) to complete its total life span, while the Rice-Fruit-Fish diet took more time (51.3±1.3 days). The absence of Fruit-Vegetable combination in diets could greatly affect the larval growth and development. It can be concluded that the diet combination of Rice-Fruit-Vegetable-Fish can be utilised for better mass production of BSF for sustainable feed production in Bangladesh.

A comparison of ventricular volume and linear indices in predicting shunt dependence in aneurysmal subarachnoid hemorrhage

BackgroundGuidelines for determining shunt dependence after aneurysmal subarachnoid hemorrhage (aSAH) remain unclear. We previously demonstrated change in ventricular volume (VV) between head CT scans taken pre- and post-EVD clamping was predictive of shunt dependence in aSAH. We sought to compare the predictive value of this measure to more commonly used linear indices. MethodsWe retrospectively analyzed images of 68 patients treated for aSAH who required EVD placement and underwent one EVD weaning trial, 34 of whom underwent shunt placement. We utilized an in-house MATLAB program to analyze VV and supratentorial VV (sVV) in head CT scans obtained before and after EVD clamping. Evans' index (EI), frontal and occipital horn ratio (FOHR), Huckman's measurement, minimum lateral ventricular width (LV-Min.), and lateral ventricle body span (LV-Body) were measured using digital calipers in PACS. Receiver operating curves (ROC) were generated. ResultsArea under the ROC curves (AUC) for the change in VV, sVV, EI, FOHR, Huckman's, LV-Min., and LV-Body with clamping were 0.84, 0.84, 0.65, 0.71.0.69, 0.67, and 0.66, respectively. AUC for post-clamp scan measurements were 0.75, 0.75, 0.74, 0.72, 0.72, 0.70, and 0.75, respectively. ConclusionVV change with EVD clamping was more predictive of shunt dependence in aSAH than change in linear measurements with clamping and all post-clamp measurements. Measurement of ventricular size on serial imaging with volumetrics or linear indices utilizing multidimensional data points may therefore be a more robust metric than unidimensional linear indices in predicting shunt dependence in this cohort. Prospective studies are needed for validation.

The Interaction between a Liquid Combustion Front and a Fire Barrier Made of CO2 Hydrate

This paper presents experimental research into the propagation of a liquid fuel combustion front interacting with a fire barrier made of CO2 hydrate and ice. The combustible liquids studied here were kerosene, gasoline, Diesel fuel, oil, petroleum, and alcohol. The experiments with gas hydrate involved fire barriers based on powder and tablets. Heat and mass transfer and phase transitions in the area between the fire barrier and the combustion front were found to play a fundamental role. The liquid fuel combustion fronts propagate at a velocity ranging from 0.1 m/s to 3 m/s under natural convection. Forced convection leads to 2- to 5-fold changes in the flame propagation velocities. According to our experiments, 2–4 cm is the minimum width of a CO2 hydrate fire barrier for stopping the flame combustion front. We also determined the contribution of the gas hydrate dissociation to fire suppression and identified the conditions of the combustion front stoppage. The dimensionless processing of experimental data made them scalable to industrial applications. Finally, the experimental findings were also used to develop physical and mathematical models predicting the necessary and sufficient amount of CO2 hydrate in a fire barrier to provide the effective deceleration and stoppage of a flame combustion front.

Retinal Nerve Fiber Layer Thickness/Minimum Rim Width Ratio Differentiates Glaucoma from Other Optic Neuropathies.

Global peripapillary retinal nerve fiber layer thickness/Bruch membrane opening- minimum rim width ratio is an objective and effective parameter to separate glaucomatous optic neuropathies (GONs) from nonglaucomatous optic neuropathies (NGONs). This study was undertaken to evaluate the diagnostic capability of the peripapillary retinal nerve fiber layer (pRNFL)/ Bruch membrane opening-minimum rim width (BMO-MRW) ratio to differentiate glaucomatous optic neuropathies (GONs) from nonglaucomatous optic neuropathies (NGONs). This retrospective study included patients with an optic neuropathy (ON), visual loss for>6 months and a confirmed single etiology. pRNFL thickness and BMO-MRW were measured with spectral-domain OCT (Spectralis®, Heidelberg Engineering, Heidelberg, Germany). The diagnostic accuracies of pRNFL, BMO-MRW and the global pRNFL/BMO-MRW ratio were evaluated with the areas under receiver operating characteristics curves (AUROCs). One eye each from 171 patients was investigated: 50 primary open-angle glaucomas, 15 normal pressure glaucomas, 50 optic neuritises, 15 nonarteritic anterior ischemic ONs, 24 compressive ONs, 10 dominant optic atrophies and 7 nutritional ONs. The global pRNFL/BMO-MRW ratio had the highest AUROC [0.97 vs. 0.92; P =0.01]. It was able to distinguish between GONs and NGONs with a cut-off value of 0.34. Increased mean deviation of the visual field-defect severity was associated with a higher ratio for GONs and a lower ratio for NGONs. Compared to NGONs and for the same degree of pRNFL thinning, lower BMO- MRW was found to be a specific marker of glaucoma, reflecting the neuroglial architecture changes within the optic nerve head typical of glaucoma and supporting fundamental pathophysiological differences.

A crack characterization model for subsea pipeline based on spatial magnetic signals features

The inspection and quantification of minor defects for subsea pipelines is an important topic for ensuring structural stability and safety. This study proposes an in-line inspection and characterization model for the subsea pipeline cracks based on spatial magnetic signals extraction technology and machine learning algorithms. First, the crack inspection mechanism is elaborated by the magnetic domain deflection from the micro level, and the effect of the crack width, depth, and lift-off on the signal features are evaluated by numerical simulations. Second, a custom-built experimental system adopted to scan the tiny cracks is incorporated to validate the reliability of the simulation results. Finally, 11 statistic features are extracted from the time series signals and defined as the input of the regression models based on various machine learning algorithms to realize the quantitative characterization of the crack dimensions. Consequently, the probes manufactured in this research can accurately identify cracks with a minimum width of 0.3 mm. Moreover, the random forest algorithm achieves state-of-the-art inversion performance with mean errors of the prediction accuracy to the crack width, depth, and lift-off at 0.102 mm, 0.040 mm, and 0.004 mm, respectively.

The Short-Term Results of Autologous Platelet-Rich Plasma as an Adjuvant to Re-Intervention in the Treatment of Refractory Full-Thickness Macular Holes

The purpose of this study was to investigate the short-term efficacy and safety of autologous platelet-rich plasma (a-PRP) as an adjuvant to revisional vitrectomy for refractory full-thickness macular holes (rFTMHs). We conducted a prospective, non-randomized interventional study including patients with rFTMH after a pars plana vitrectomy (PPV) with internal limiting membrane peeling and gas tamponade. We included 28 eyes from 27 patients with rFTMHs: 12 rFTMHs in highly myopic eyes (axial length greater than 26.5 mm or a refractive error greater than -6D or both); 12 large rFTMHs (minimum hole width > 400 μm); and 4 rFTMHs secondary to the optic disc pit. All patients underwent 25-G PPV with a-PRP, a median time of 3.5 ± 1.8 months after the primary repair. At the six-month follow-up, the overall rFTMH closure rate was 92.9%, distributed as follows: 11 out of 12 eyes (91.7%) in the highly myopic group, 11 out of 12 eyes (91.7%) in the large rFTMH group, and 4 out of 4 eyes (100%) in the optic disc pit group. Median best-corrected visual acuity significantly improved in all groups, in particular from 1.00 (interquartile range: 0.85 to 1.30) to 0.70 (0.40 to 0.85) LogMAR in the highly myopic group (p = 0.016), from 0.90 (0.70 to 1.49) to 0.40 (0.35 to 0.70) LogMAR in the large rFTMH group (p = 0.005), and from 0.90 (0.75 to 1.00) to 0.50 (0.28 to 0.65) LogMAR in the optic disc pit group. No intraoperative or postoperative complications were reported. In conclusion, a-PRP can be an effective adjuvant to PPV in the management of rFTMHs.

The Q‐switching performance of BP/SnSe2 heterojunction saturable absorber in Er‐doped fiber laser

AbstractIn this paper, we report the first Q‐switching operation utilizing black phosphorus (BP)/SnSe2 heterojunction as the saturable absorber (SA) in an Er‐doped fiber laser. The BP/SnSe2 heterojunction was prepared by the liquid phase combination method and its properties were observed. Stable Q‐switching operations were achieved based on the BP/SnSe2 SA. The maximum peak power of 71.27 mW and the minimum pulse width of 910 ns were produced, respectively. This paper demonstrates the pulse modulation characteristics of BP/SnSe2 heterojunction SA in the midinfrared region for the first time, laying an important foundation for the application of heterojunction based on BP and two‐dimensional transition metal dichalcogenides.

Scalability of Superconductor Electronics: Limitations Imposed by AC Clock and Flux Bias Transformers

Flux transformers are the necessary component of all superconductor digital integrated circuits utilizing ac power for logic cell excitation and clocking, and flux biasing, e.g., Adiabatic Quantum Flux Parametron (AQFP), Reciprocal Quantum Logic, superconducting sensor arrays, qubits, etc. We consider limitations to the integration scale (device number density) imposed by the critical current of the ac power transmission lines and cross coupling between the adjacent transformers. The former sets the minimum line width and the mutual coupling length in the transformer, whereas the latter sets the minimum spacing between the transformers. Decreasing linewidth of superconducting (Nb) wires increases kinetic inductance of the transformer's secondary, decreasing its length and mutual coupling to the primary. This limits the minimum size of transformers. As a result, there is a minimum linewidth ~100 nm which determines the maximum achievable scale of integration. Using AQFP circuits as an example, we calculate dependence of the AQFP number density on linewidth for various types of transformers and inductors available in the SFQ5ee fabrication process developed at MIT Lincoln Laboratory, and estimate the maximum circuit density as a few million AQFPs per cm^2. We propose an advanced fabrication process for a 10x increase in the density of AQFP and other ac-powered circuits. In this process, inductors are formed from a patterned bilayer of a geometrical inductance material (Nb) deposited over a layer of high kinetic inductance material (e.g., NbN). Individual pattering of the bilayer layers allows to create stripline inductors in a wide range of inductances, from the low values typical to Nb striplines to the high values typical for NbN thin films, and preserve sufficient mutual coupling in stripline transformers with extremely low crosstalk.

Compact Optical System Based on Scatterometry for Off-Line and Real-Time Monitoring of Surface Micropatterning Processes

In this study, a scatterometry-based monitoring system designed for tracking the quality and reproducibility of laser-textured surfaces in industrial environments was validated in off-line and real-time modes. To this end, a stainless steel plate was structured by direct laser interference patterning (DLIP) following a set of conditions with artificial patterning errors. Namely, fluctuations of the DLIP process parameters such as laser fluence, spatial period, and focus position are introduced, and also, two patterning strategies are implemented, whereby pulses are deliberately not fired at both deterministic and random positions. The detection limits of the system were determined by recording the intensities of the zero, first, and second diffraction order using a charge-coupled device (CCD) camera. As supported by topographical measurements, the system can accurately calculate spatial periods with a resolution of at least 100 nm. In addition, focus shifts of 70 µm from the optimum focus position can be detected, and missing patterned lines with a minimum width of 28 µm can be identified. The validation of this compact characterization unit represents a step forward for its implementation as an in-line monitoring tool for industrial laser-based micropatterning.

On the field size definition and field output factors in small field dosimetry.

There is a major conceptual difference between small-field and large field dosimetry that is, different definition of the field size. The dosimetry protocol IAEA TRS-483 recommends the use of the field size defined by measured dose profiles (full-width half maximum, FWHM) that is significantly different from conventional field size definition by the geometric field opening of MLC/Jaw at the isocenter. The application of the effective field size concept, Sclin , was introduced by Cranmer-Sargison etal. (DOI:10.1016/j.radonc.2013.10.002) as a reporting mechanism for field output factors of rectangular fields. The study by Das etal. (DOI:10.1002/mp.15624) indicated the limitations of obtaining the field size by experimentally measuring FWHM, for example, the measured FWHM is smaller than beam geometric size, which is contradictory to what is expected as a result of partial occlusion of the primary photon source by the collimating devices. Cranmer-Sargison etal. and Das et al suggested that additional investigations are needed to evaluate its limitations. This study investigates the validity of the field size definition by FWHM and by MLC/Jaw opening and finds the pros and cons between these two methods to resolve the controversial issue. The FWHM can be obtained by measuring or calculating dose profiles. Using Monte Carlo simulations this study compares the field size obtained by FWHM and by field geometric field opening. The EGSnrc system is used to simulate 6 MV beam to generate square and rectangular fields from 5-30mm with every possible permutation (keeping one jaw fixed and varying other jaw from 5 to 30mm). The calculated FWHM and output factors are compared with measurements obtained by a microSilicon detector. The results show that field width (FWHM) derived from MC calculations generally agrees with machine geometric field width within 0.5mm for square or rectangular fields with a minimum field width of ≥8mm. For the extremely small fields with a minimum field width of 5mm the discrepancies are up to 1.6mm. The field width (FWHM) obtained by measuring dose profiles are unreliable for small fields due to the measurement uncertainties for an extremely small field. The effect of partial occlusion of the primary photon source by the jaws on the beam axis is clearly observed in the calculated dose profiles. For the extremely small field width of 5mm, Monte Carlo predicted up to 10% exchange factor differences which are confirmed by the measurements. The field size defined by the geometric opening of the beam-defining system, is still valid for small fields. The field size defined by geometric opening is independent of measurement uncertainties, independent of machine design, and highly reproducible. It is feasible to accurately tabulate the output factors as a function of geometric field opening thus eliminating user and detector choice for FWHM measurements. The field output factor of a small rectangular field cannot be related to an equivalent field size without considering the exchange factor due to partial occlusion of the photon source.

ASC-G4, an algorithm to calculate advanced structural characteristics of G-quadruplexes.

ASC-G4 is an algorithm for the calculation of the advanced structural characteristics of G-quadruplexes (G4). It allows the unambiguous determination of the intramolecular G4 topology, based on the oriented strand numbering. It also resolves the ambiguity in the determination of the guanine glycosidic configuration. With this algorithm, we showed that the use of the C3' or C5' atoms to calculate the groove width in G4 is more appropriate than the P atoms and that the groove width does not always reflect the space available within the groove. For the latter, the minimum groove width is more appropriate. The application of ASC-G4 to 207 G4 structures guided the choices made for the calculations. A website based on ASC-G4 (http://tiny.cc/ASC-G4) was created, where the user uploads his G4 structure and gets its topology, the types of its loops and their lengths, the presence of snapbacks and bulges, the distribution of guanines in the tetrads and strands, the glycosidic configuration of these guanines, their rise, the groove widths, the minimum groove widths, the tilt and twist angles, the backbone dihedral angles, etc. It also provides a large number of atom-atom and atom-plane distances that are relevant to evaluating the quality of the structure.

Charge carrier density dependent Raman spectra of graphene encapsulated in hexagonal boron nitride

We present low-temperature Raman measurements on gate tunable graphene encapsulated in hexagonal boron nitride, which allows to study in detail the Raman G and 2D mode frequencies and line widths as function of the charge carrier density. We observe a clear softening of the Raman G mode (of up to 2.5 cm$^{-1}$) at low carrier density due to the phonon anomaly and a residual G~mode line width of $\approx$ 3.5 cm$^{-1}$ at high doping. From analyzing the G mode dependence on doping and laser power we extract an electron-phonon-coupling constant of $\approx$ 4.4 $\times$ 10$^{-3}$ (for the G mode phonon). The ultra-flat nature of encapsulated graphene results in a minimum Raman 2D peak line width of 14.5 cm$^{-1}$ and allows to observe the intrinsic electron-electron scattering induced broadening of the 2D peak of up to 18 cm$^{-1}$ for an electron density of 5$\times$10$^{12}$ cm$^{-2}$ (laser excitation energy of 2.33 eV). Our findings not only provide insights into electron-phonon coupling and the role of electron-electron scattering for the broadening of the 2D peak, but also crucially shows the limitations when it comes to the use of Raman spectroscopy (i.e. the use of the frequencies and the line widths of the G and 2D modes) to benchmark graphene in terms of charge carrier density, strain and strain inhomogenities. This is particularly relevant when utilizing spatially-resolved 2D Raman line width maps to assess substrate-induced nanometer-scale strain variations.

Experimental Investigation of High-Viscosity Conductive Pastes and the Optimization of 3D Printing Parameters

Traditional contact printing technology is primarily controlled by the shape of the mask to form the size, while for the more popular non-contact printing technologies, in recent years, adjusting the print parameters has become a direct way to control the result of the printing. High-viscosity conductive pastes are generally processed by screen printing, but this method has limited accuracy and wastes material. Direct-write printing is a more material-efficient method, but the printing of high-viscosity pastes has extrusion difficulties, which affects the printed line width. In this paper, we addressed these problems by studying the method of printing high-viscosity conductive paste with a self-made glass nozzle. Then, by parameter optimization, we achieved the minimum line width printing. The results showed that the substrate moving speed, the print height, and the feed pressure were the key factors affecting the line width and stability. The combination of the printing parameters of 0.6 MPa feed pressure, 200 mm/s substrate moving speed, and 150 μm print height can achieve a line width of approximately 30 μm. In addition, a mathematical model of the line width and parameters was established, and the prediction accuracy was within 5%. The results and the prediction model of the parameters provide an important reference for the printing of high-viscosity pastes, which have immense potential applications in electronics manufacturing and bioprinting.

Forensic Gender Determination by Using Mandibular Morphometric Indices an Iranian Population: A Panoramic Radiographic Cross-Sectional Study.

Gender determination is the first step in forensic identification, followed by age and height determination, which are both affected by gender. This study assessed the accuracy of gender estimation using mandibular morphometric indices on panoramic radiographs of an Iranian population. This retrospective study evaluated 290 panoramic radiographs (145 males and 145 females). The maximum and minimum ramus width, coronoid height, condylar height, antegonial angle, antegonial depth, gonial angle, and the superior border of mental foramen were bilaterally measured as well as bicondylar and bigonial breadths using Scanora Lite. Correlation of parameters with gender was analyzed by univariate, multiple, and best models. All indices except for gonial angle were significantly different between males and females and can be used for gender determination according to univariate model. Condylar height, coronoid height, and superior border of mental foramen and ramus were still significantly greater in males than in females after controlling for the effect of confounders (p < 0.05). Based on the best model, a formula including five indices of bicondylar breadth, condylar height, coronoid height, minimum ramus width, and superior border of mental foramen was used for gender determination. Values higher than 56% indicate male gender, while lower values indicate female gender, with 81.38% specificity for correct detection of females and 88.97% sensitivity for correct detection of males. Despite the satisfactory results, future research should focus on larger populations to verify the accuracy of the present findings.

Emergence of macroscopic directional motion of deformable active cells in confined structures.

There is now growing evidence of collective turbulentlike motion of cells in dense tissues. However, how to control and harness this collective motion is an open question. We investigate the transport of deformable active cells in a periodically asymmetric channel by using a phase-field model. We demonstrate that collective turbulent-like motion of cells can power and steer the macroscopic directional motion through the ratchet channel. The active intercellular forces proportional to the deformation of cells can break thermodynamical equilibrium and induce the directional motion. This directional motion is caused by the ratchet effect rather than the spontaneous symmetry breaking. The motion direction is determined by the asymmetry of the channel. Remarkably, there exits an optimal nonequilibrium driving (depending on the active strength, the elasticity, and the packing fraction) at which the average velocity reaches the maximum. In addition, the optimized packing fraction and the optimized minimum width of the channel can facilitate the directional motion of cells. Our findings are relevant to understanding how macroscopic directional motion relates to the local force transmission mediated by cell-cell contacts in cellular monolayers.

Analysis of Hand Joint Space Morphology in Women and Men with Hereditary Hemochromatosis

Hereditary hemochromatosis (HH) causes unbalanced iron deposition in many organs including the joints leading to severe cartilage loss and bone damage in the metacarpophalangeal joints (MCPJ). High-resolution peripheral quantitative computed tomography (HR-pQCT) and its joint space width (JSW) quantification algorithm quantifies in vivo 3D joint morphology. We therefore aimed to (i) determine feasibility and performance of the JSW algorithm in HH, (ii) quantify joint space morphology, and (iii) investigate the relationship between morphological and clinical parameters in HH. Here, we performed an exploratory study on 24 HH patients and sex- and age-matched controls using HR-pQCT imaging of MCPJ. Mineralized bone structure was automatically segmented from the grayscale image data and periosteal surface bone masks and joint space masks were generated. Mean, minimal, and maximal joint space width (JSW; JSW.MIN; JSW.MAX), JSW heterogeneity (JSW.SD), JSW asymmetry (JSW.AS), and joint space volume (JSV) were computed. Demographics and, for HH patients, disease-specific parameters were recorded. Segmentation of JS was very good with 79.7% of MCPJs successfully segmented at first attempt and 20.3% requiring semi-manual correction. HH men showed larger JSV at all MCPs (+ 25.4% < JSV < + 41.8%, p < 0.05), larger JSW.MAX at MCP 3-4 (+ 14%, 0.006 < p < 0.062), and wider JSW (+ 13%, p = 0.043) at MCP 4 relative to HH women. Compared to controls, both HH men and HH women showed larger JSW.AS and smaller JSW.MIN at all MCP levels, reaching significance for HH men at MCP 2 and 3 (JSW.AS: + 323% < JSW.AS < + 359%, 0.020 < p < 0.043; JSW.MIN: − 216% < JSW.MIN < − 225%, p < 0.043), and for women at MCP 3 (JSW.AS: + 180%, p = 0.025; JSW.MIN: − 41.8%, p = 0.022). Time since HH diagnosis was correlated positively with MCP 4 JSW.AS and JSW.SD (0.463 < ρ < 0.499, p < 0.040), and the number of phlebotomies since diagnosis was correlated with JSW.SD at all MCPs (0.432 < ρ < 0.535, p < 0.050). HR-pQCT-based JSW quantification in MCPJ of HH patients is feasible, performs well even in narrow JS, and allows to define the microstructural joint burden of HH.

Effective substrate for the growth of multilayer h-BN on sapphire—substrate off-cut, pre-growth, and post-growth conditions in metal-organic vapor phase epitaxy

The substrate is one of the key components that determines the quality of the epitaxial layers. However, the implications of growing two-dimensional layers on three-dimensional bulk substrates have not yet been fully understood, and these implications need to be studied for different combinations of materials and substrates. Here, we present a study that addresses the influence of the sapphire substrate off-cut angle on the final growth of two-dimensional layers of hexagonal boron nitride (h-BN) by metal-organic vapor phase epitaxy (MOVPE). A two-step wafer-scale process was used in one epitaxial MOVPE procedure. The main process starts with a self-limiting continuous growth of a BN buffer followed by flow-modulated epitaxy in the second step, and is used to study substrates with different off-cuts angles, pre-growth nitridation steps, and post-growth annealing. An initial nitridation step at the growth temperature allowed for the growth of an AlN sublayer. This layer is shown to smooth out the underlying sapphire and establishes an ‘effective’ sapphire/AlN substrate. This step is also responsible for enforcing a specific growth of the BN layer in a crystallographic orientation, which is shown to strongly deviate from the substrate for off-cut angles larger than 0.3°. A substrate with off-cut angle of 1° clearly yields the highest quality of h-BN layers as evidenced by the lowest amount of debris on the surface, most intense x-ray diffraction signal, minimal Raman phonon line width and thinnest amorphous BN (a-BN) at the interface with the effective substrate. Our study shows that the off-cut angles of sapphire substrates strongly influence the final epitaxial h-BN, clearly indicating the importance of optimal substrate preparation for the growth of two-dimensional BN layers. Post-growth annealing in N2 atmosphere at 800 °C improves the top surface morphology of the final stack, as well as suppresses further the presence of a-BN.

Pulsed Er:YAG single corner cube ring cavity with variable output ratio

In this paper, a ring cavity of Er:YAG laser with a single corner cube prism is investigated. Due to the depolarization effect of the corner cube, the tunable output coupling ratio was 0.25% to 72.67% by changing the angle of the λ / 4 plate according to the calculation results of Jones matrix. An experiment for checking the anti-detuning performances of the single corner cube cavity was also carried out. The results indicated that the output power was stable at the rotating angles of <3.06 deg and 1.637 deg along the vertical and horizontal directions, respectively. Under continuous wave operation, a 5.4 W vertically-polarized laser of 1645.1 nm was acquired through double polarizers with the beam quality factors (M2) of 1.17 in the x direction and 1.42 in the y direction, and the slope efficiency was 45.47%. Additionally, under the condition of a pulse-repetition-frequency (PRF) of 200 Hz, the pump power of 29.04 W, a maximum pulse energy of 2.2 mJ was realized, and the minimum pulse width was 86 ns, leading to a peak power of 25.58 KW.