Aluminum Arsenide Research Articles

Оптические свойства InGaAs/InAlAs метаморфных наногетероструктур для фотопреобразователей лазерного и солнечного излучения

AbstractReflectance spectroscopy has been used to determine the refractive indices of nanoscale In_ x Al_ y Ga_1– x – y As and In_ x Al_1– x As layers with indium and aluminum concentrations x = 0.21–0.24 and y = 0, 0.1, and 0.2 on specially created Bragg-reflector heterostructures at wavelengths in the range 700–2000 nm. It was demonstrated that the method based on an analysis of the auto- and cross-correlation coefficients of the wavelength derivatives of the dependence of the reflectance of structures of this kind in order to determine the dispersion curves of the materials forming a reflector. It was found that raising the concentration of indium in InGaAs and AlInAs leads to a substantial rise in the refractive index, with a preserved spectral run of the refractive indices, which is characteristic of gallium arsenide and aluminum arsenide.

Low-Level Laser Therapy in Periodontics: A Review Article

Low-Level Laser Therapy (LLLT) is a light source treatment that generates light of a single wavelength. The low-level lasers do not cause temperature elevation within the tissue, but rather produce their effects from photobiostimulation effect within the tissues. Low-level lasers do not cut or ablate the tissue. The therapy performed with Low-Level Lasers is called as LLLT. LLLT devices include the gallium arsenide, gallium aluminum arsenide infrared semiconductor (gallium-aluminum-arsenide), and helium-neon lasers. The output powers range from 50 to 500 mW with wavelengths in the red and near infrared of the electromagnetic spectrum, from 630 to 980 nm with pulsed or continuous-wave emission.

The Doping Effect on Ferromagnetic Arrangement and Electronic Structure of Cubic AlAs with Low Concentration of 3d (V, Cr, and Mn) Impurities

The doping effect of aluminum arsenide (AlAs) with 3d (TM = V, Cr, and Mn) of transition metal impurities gives new materials called diluted magnetic semiconductors, which have interesting electronic and magnetic properties for spintronics applications. We have used the full-potential linearized augmented plane wave (FP-LAPW) method to calculate the electronic band structures and magnetic properties of Al1−x TM x As at low concentration x = 0.0625 of transition metal (TM = V, Cr, and Mn) atoms. We have found that the majority-spin states of Al0.9375 TM 0.0625As compounds are metallic due to large p-d hybridization between 3d levels of TM and the 4p levels of As around Fermi level, whereas the minority-spin states have semiconductor character. These compounds exhibit a half-metallic behavior with spin polarization of 100%, where the ferromagnetism is originated from double-exchange mechanism. Therefore, Al0.9375 TM 0.0625As (TM = V, Cr, and Mn) materials seem to be good candidates for spin injection in the field of spintronics applications.

The Effects of Transcutaneous and Intraoral Low-Level Laser Therapy After Extraction of Lower Third Molars: A Randomized Single Blind, Placebo Controlled Dual-Center Study.

The surgical removal of impacted third molars is one of the most common procedures performed by oral and maxillofacial surgeons. The purpose of this study is to determine whether either transcutaneous or intraoral low-level laser therapy (LLLT) reduces postoperative pain and assists in the healing of mandibular third molar extraction. This randomized, placebo controlled, single-blind, split-mouth design study was conducted on 60 patients with full bony impacted similar position mandibular third molars bilaterally. The patients were divided into two groups of 30 each: transcutaneous LLLT and intraoral LLLT and the other side of each group treated with nonactive laser (60 teeth). The laser treatment consisted of administering laser energy immediately before and after the extraction procedure with gallium aluminum arsenide (GaAlAs) 830 nm diode lasers. Postoperative pain and healing of the sockets were compared in transcutaneous and intraoral group with placebo for 1 week following the extraction. Descriptive and bivariate statistics was computed, and the p-value was set at 0.05. Intraoral LLLT application resulted in a statistically significant reduction of postoperative pain in comparison with transcutaneous laser group and placebo. The unhealed socket numbers were compared in two groups at seventh day and no differences were observed. The results of this study suggest that single-session intraoral LLLT is more effective than extraoral application for reducing postoperative pain. It was postulated that the differences between skin and mucosa could have effect on the results. Although intraoral use would allow closer application to the surgical site, the size of some laser devices precludes their use intraorally.

Influence of low-level laser therapy on the healing of human bone maxillofacial defects: A systematic review

PurposeThis systematic review evaluates the effectiveness of low-level laser therapy (LLLT) to enhance maxillofacial area bone repair. MethodsA comprehensive search of studies published up to February 2017 and listed in PubMed/MEDLINE, Scopus, and Cochrane Library databases was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. ResultsThe 15 selected studies evaluated a total of 374 patients (mean age, 28.5years) who were treated with LLLT. Gallium-arsenide (GaAs) and gallium aluminium arsenide (GaAlAs) were the most commonly used devices, and LLLT parameters varied greatly. Wavelengths varied from 500 to 1000nm. Tooth extraction, distraction osteogenesis, maxillary expansion, periodontal defects, orthodontic movement and maxillary cystic defects were evaluated. From the 15 selected studies, six evaluated bone repair (primary outcomes). Of these, four studies showed improvement in bone formation after using LLLT, two demonstrated improved results for only one follow up period, and one showed no additional benefits. The other 9 studies evaluated secondary parameters related to healing (secondary outcomes) in the maxillofacial area after applying LLLT, including anti-inflammatory, analgesic, and healing accelerator effects, and quality of life related to oral health. There were no adverse or negative effects of LLLT reported. ConclusionWithin the limitation of this review, a possible improvement in bone density can be found when LLLT is applied postoperatively in maxillofacial bony defects. LLLT also seems to promote anti-inflammatory and analgesic effects and accelerate healing, as well as enhance quality of life related to oral health. However, LLLT use protocols need to be standardized before more specific conclusions can be drawn about this subject.

Understanding band gaps of solids in generalized Kohn–Sham theory

The fundamental energy gap of a periodic solid distinguishes insulators from metals and characterizes low-energy single-electron excitations. However, the gap in the band structure of the exact multiplicative Kohn-Sham (KS) potential substantially underestimates the fundamental gap, a major limitation of KS density-functional theory. Here, we give a simple proof of a theorem: In generalized KS theory (GKS), the band gap of an extended system equals the fundamental gap for the approximate functional if the GKS potential operator is continuous and the density change is delocalized when an electron or hole is added. Our theorem explains how GKS band gaps from metageneralized gradient approximations (meta-GGAs) and hybrid functionals can be more realistic than those from GGAs or even from the exact KS potential. The theorem also follows from earlier work. The band edges in the GKS one-electron spectrum are also related to measurable energies. A linear chain of hydrogen molecules, solid aluminum arsenide, and solid argon provide numerical illustrations.

Effects of Porphyromonas gingivalis on Titanium Surface by Different Clinical Treatment

As peri-implantitis is associated with biofilm development, the characteristics of titanium implants may influence biofilm formation, and thereby increase the risk for inflammation. The objective of this study was to evaluate the effect of titanium surface roughness induced by various debridement methods of peri-implants, such as the use of an ultrasonic scaler, rubber polishing cup, gallium–aluminum–arsenide laser, and chlorhexidine (CHX) rinse, on Porphyromonas (P.) gingivalis. Surface debridement was performed by immersing titanium discs in CHX rinse for 24 h or treatment with a laser, polishing cup, or ultrasonic scaler for 60 s. Surface topography was examined using a profilometer. For the bacterial assay, specimens were inoculated with P. gingivalis for 2 h and incubated for 6, 12, and 24 h. After incubation, bacterial adhesion on the discs was quantified via spectrophotometric evaluation. Moreover, scanning electron microscopy (SEM) images were analyzed to quantify P. gingivalis colonization on the titanium surfaces. Data were analyzed using one-way analysis of variance and Pearson’s correlation test (p < 0.05). Scaled surfaces showed the highest surface roughness (Ra, p < 0.001). There was a significant positive correlation between Ra values and optical density measurements at all incubation times (p < 0.05). The quantitative evaluation of P. gingivalis attachment through SEM revealed that the amounts of bacteria were significantly lower in the control, laser, and CHX groups compared with those in the other groups (p < 0.05). Moreover, a significant positive correlation was found between Ra and attached P. gingivalis number obtained from SEM images (p < 0.05). In conclusion, polishing, CHX, and laser treatments of titanium surfaces provide the highest reduction in P. gingivalis biofilm mass and regrowth in vitro. This effect was enhanced as the smoothness of the titanium surface was increased.

Low-level Laser Therapy on Postoperative Pain after Mandibular Third Molar Surgery.

Introduction:The analgesic effect of low-level laser therapy (LLLT) after mandibular third molar (MTM) extraction is controversial. The aim is to evaluate the effect of intraoral LLLT on postoperative pain after MTMs extraction.Methods:Thirty patients with bilateral symmetrical impacted MTMs underwent surgical extractions. Experimental and control sides were randomly selected to receive LLLT or placebo. Following suturing, a dental assistant applied 810 nm gallium aluminum arsenide (GaAlAs) at three points for 30 s each with a total energy of 9 J. Pain was recorded on a visual analog scale on the 7 successive days.Results:Data analyzed by IBM SPSS Statistics 23 for Windows with P ≤ 0.05 significance level. LLLT appeared to have a high significant effect on pain reduction; however, there was a mild increase in pain after the 4th day.Conclusion:Intraoral 810 nm GaAlAs is effective in reducing postoperative pain when a dose of 32.86 J/cm2 is used.

Effect of the Clinical Application of the GLUMA Desensitizer vs Gallium Aluminum Arsenide Diode Laser in the Treatment of Dentin Hypersensitivity: A Scanning Electron Microscopy Study

Effect of the Clinical Application of the GLUMA Desensitizer vs Gallium Aluminum Arsenide Diode Laser in the Treatment of Dentin Hypersensitivity: A Scanning Electron Microscopy Study

Low-level laser therapy: A novel therapeutic approach to temporomandibular disorder - A randomized, double-blinded, placebo-controlled trial.

The objective of this study was to assess the effectiveness of low-level laser therapy (LLLT)/low intensity laser therapy (LILT) in the management of temporomandibular joint (TMJ) pain in a random and double-blind research design. TMJ pain patients, randomly assigned into two groups: Group 1 (n = 20) and Group 2 (n = 20), received 2-3 treatments per week for 8 sessions of active LILT with diode laser (gallium aluminum arsenide, 810 nm, 0.1 W). Measures of TMJ pain during function were evaluated at baseline, after completion of 8 sessions of laser treatment, and 30 days after the final laser therapy. At the final treatment point, within-group, pain reduction was observed in both active LLLT and placebo groups at day 0 (P = 0.000), 8th session (P = 0.000), and 1 month (P = 0.001). Between the groups, there is no significant difference at day 0 (P = 0.214), 8th session (P = 0.806), and 1 month (P = 0.230). Significant increased mouth opening was observed in both Group 1 and Group 2 (P = 0.006 and P = 0.021, respectively) after treatment. However, no significant difference was found between the two groups (P = 0.330). Furthermore, significant improvement in clicking was recorded before and after treatment both in Group 1 (P = 0.000) and Group 2 (P = 0.001). The study suggests that LLLT is not better than placebo at reducing TMJ pain during function. It may be assumed that a more tailored application of LLLT should be developed to take into account the multifactorial aspect of the disorder.

Metastable phases, phase transformation and properties of AlAs based on first-principle study

By utilizing an evolutionary methodology on crystal structure search, we propose three new metastable phases for aluminum arsenide (AlAs) as follows: (1) a P6422 symmetric structure (hP6-AlAs), (2) a C222 symmetric structure (oC12-AlAs), and (3) a I4¯3d symmetric structure (cI24-AlAs). By controlling the unloading pressure rate, oC12-, hP6-, and cI24-AlAs may be acquired through quenching NiAs-AlAs. The elastic constants and phonon dispersion spectra are calculated to certify the mechanical and dynamic stabilities of three newly discovered phases. On the basis of first-principle study, we explore phase transformations under pressure for several AlAs polymorphs. The calculation of mechanical properties illustrates that oC12-, and hP6-AlAs possess similar hardness levels, which are higher than that of cI24-AlAs. Meanwhile, oC12-, and hP6-AlAs hold similar shear anisotropic factors, which are smaller than that of cI24-AlAs. Electronic band structure calculation reveals that at zero pressure, oC12-, and hP6-AlAs possess indirect band gaps of 0.468eV and 1.356eV, respectively. cI24-AlAs is a direct semiconductor with a gap value 1.761eV.

Determination of Band Structure of Gallium-Arsenide and Aluminium-Arsenide Using Density Functional Theory

This research paper is on Density Functional Theory (DFT) within Local Density Approximation. The calculation was performed using Fritz Haber Institute Ab-initio Molecular Simulations (FHIAIMS) code based on numerical atomic-centered orbital basis sets. The electronic band structure, total density of state (DOS) and band gap energy were calculated for Gallium-Arsenide and Aluminium-Arsenide in diamond structures. The result of minimum total energy and computational time obtained from the experimental lattice constant 5.63 A for both Gallium Arsenide and Aluminium Arsenide is -114,915.7903 eV and 64.989 s, respectively. The electronic band structure analysis shows that Aluminium-Arsenide is an indirect band gap semiconductor while Gallium-Arsenide is a direct band gap semiconductor. The energy gap results obtained for GaAs is 0.37 eV and AlAs is 1.42 eV. The band gap in GaAs observed is very small when compared to AlAs. This indicates that GaAs can exhibit high transport property of the electron in the semiconductor which makes it suitable for optoelectronics devices while the wider band gap of AlAs indicates their potentials can be used in high temperature and strong electric fields device applications. The results reveal a good agreement within reasonable acceptable errors when compared with the theoretical and experimental values obtained in the work of Federico and Yin wang [1] [2].

A comparative evaluation to assess the efficacy of 5% sodium fluoride varnish and diode laser and their combined application in the treatment of dentin hypersensitivity.

Background:Dentin hypersensitivity (DH) is an age old complaint with a great number of treatment modalities, but none of these are totally effective till date. Lasers being one of the latest treatment options in periodontics, a study was conducted to test the efficacy of diode laser (DL) in DH alone and in comparison with 5% sodium fluoride (NaF) varnish.Aim:The aim of the present study was to compare the effectiveness of 5% topical NaF varnish and 980 nm gallium aluminum arsenide (GaAlAs) DL alone and combination of 5% NaF + 980 nm GaAlAs DL in the management of DH.Materials and Methods:The study was conducted on 120 teeth in thirty patients with DH assessed by tactile and air blast (AB) stimuli measured by visual analog scale (VAS). Teeth were randomly divided into Group 1 (P) placebo-treated control group, Group 2 (NaF) treated by 5% NaF varnish, Group 3 (DL) treated with 980 nm DL, and Group 4 (NaF + DL) treated with both 5% NaF varnish and 980 nm DL (combination group).Results:There was a significant reduction in DH. The VAS reduction percentages were calculated, and there was a significant decrease in DH above all in G4 (NaF + DL) than G3 (DL) and G2 (NaF).Conclusion:Even though all the three groups (2, 3, and 4) showed improvement in terms of DH reduction, 5% NaF varnish with DL showed the best results among all the groups.

Structure and morphology of InSb epitaxial films in the AlAs matrix

We report the results of electron microscopy study of the structural and morphological features of epitaxial films in the AlAs matrix. The epitaxial films were grown in the matrix by deposition of indium and antimony from molecular flows onto the aluminum arsenide surface and subsequent deposition of aluminum and arsenic. The objects of study were (110) cross sections and (001) planar foils. Instead of the InSb binary compound, we found the InxAl1–xSbyAs1–y quaternary solid solution in the AlAs matrix in the form of a wetting layer with coherently conjugated and relaxed islands. The In and Sb contents in the solid solution were indirectly estimated. Misfit dislocations at the heterointerfaces of relaxed islands were analyzed using the geometric phase method. It was established that each misfit dislocation is formed by a pair of close 60° dislocations with the inclined Burgers vectors of the a/2〈110⟩ type. In this case, the resulting Burgers vector of each pair lies in the heterointerface plane.

24 Years’ Experience of Low Level Laser Therapy (LLLT) for Children with Cerebral Palsy

Since 1991, phototherapy (low-level laser therapy, near-infrared ray therapy and light-emitting diode: LED therapy) has been used in the management and rehabilitation of patients with various orthopaedic diseases. The laser used was a gallium aluminum arsenide (GaAlAs) diode laser giving output powers in continuous wave of 100 mW, at a wavelength of 810 nm. The target points were the acupuncture and the nerve block points, where the myotonia was observed, and the irradiation was performed daily. Each site was irradiated for 1 minute, with a total irradiation time of 20 minutes in total per day with contact method. The spot size at the tissue was 1.04 mm2 giving power densities of 9.61 W/cm2 at 100 mW. Energy densities were 288.3 J/cm2. When compared with patients at other training sites, where only functional training therapy was applied without LLLT, the efficacy of functional training was clearly enhanced by combination with LLLT [1,2].

Evaluation of Low Level Laser Therapy on Pain Perception Following Orthodontic Elastomeric Separation: A Randomized Controlled Trial.

Periodontal pain caused by elastomeric separators is a very common problem in the commencement of orthodontic treatment. Previous studies have shown good results in reducing this pain by Low Level Laser Therapy (LLLT) and different protocols of application have been suggested in the literature. This trial aimed to evaluate LLLT on managing orthodontic pain caused by elastomeric separators and to compare single versus double irradiation in possible pain reduction. A clinical randomized compound (parallel-group and split-mouth design) trial was conducted on 36 patients between 12 and 26 years of age. Elastomeric separators were placed at the mesial and distal surfaces of the first molars in one jaw (upper or lower) for each patient and in only one side of the mouth (the other side served as the placebo side). The trial had two groups: the first group received single irradiation of LLLT [Gallium Aluminum Arsenide (GaAlAs): 830 nm, 4J/cm2, 100mW] immediately after separators insertion, where as the second group received double irradiation immediately after separators insertion and after 24hours. All patients were instructed to rate the level of pain at 1, 6, 24, 48, 96 hours on a Visual Analog Scale (VAS). The student 't' tests, repeated measures ANOVA and LSD post-hoc tests were employed. LLLT was successful in reducing post-separation pain when the experimental side was compared to the placebo side at all assessment times in each group (p<0.05). There were no statistically significant differences between single and double irradiation groups in terms of pain reduction (p>0.05). GaAlAs LLLT application reduced early orthodontic pain caused by elastomeric separators by single or double irradiation.

The effects of combined low level laser therapy and mesenchymal stem cells on bone regeneration in rabbit calvarial defects

ObjectiveThis study evaluated the effect of Low Level Laser Therapy (LLLT) and Mesenchymal Stem Cells (MSCs) on bone regeneration. Background dataAlthough several studies evaluated the effects of MSCs and LLLT, there is little information available regarding in vivo application of LLLT in conjunction with MSCs. MethodsForty-eight circular bone defects (6mm in diameter) were prepared in the calvaria of 12 New-Zealand white rabbits. The defects of each animal were randomly assigned to 4 groups: (C) no treatment; (L) applying LLLT; (SC) filled with MSCs; (SCL) application of both MSCs and LLLT. LLL was applied on alternate days at wavelength of 810nm, power density of 0.2W/cm2 and a fluency of 4J/cm2 using a Gallium–Aluminum–Arsenide (GaAlAs) diode laser. The animals were sacrificed after 3weeks and then histological samples were evaluated to determine the amount of new bone formation and the remaining scaffold and inflammation. ResultsThe histological evaluation showed a statistically significant increase in new bone formation of LLLT group relative to the control and the other two experimental groups (p<0.05). There was no significant difference in bone formation of the control group compared to experimental groups filled with MSCs. Laser irradiation had no significant effect on resorption of the scaffold material. In addition, inflammation was significantly reduced in LLLT group compared to the control defects and the other two experimental groups. ConclusionLow level laser therapy could be effective in bone regeneration but there is no evidence of a synergistic effect when applied in conjunction with MSCs.

Effect of gallium aluminium arsenide diode laser therapy on Porphyromonas gingivalis in chronic periodontitis: a randomized controlled trial

The aim of this randomized, controlled trial was to evaluate the effects of 685-nm gallium aluminium arsenide (GaAlAs) diode laser therapy (1.6Jcm-2 ) as an adjunct to scaling and root planing in the treatment of chronic periodontitis. Thirty-two patients aged 35-60years old who had chronic periodontitis met the eligibility criteria. They were randomly assigned to two equal groups: scaling and root planing were performed in the SRP group, while scaling, root planing and laser irradiation of periodontal pockets were performed in the SRP + DL group. Subgingival plaque samples were subjected to polymerase chain reaction (PCR) to detect P.gingivalis-colonized sites, and common clinical indices were evaluated before and 2months after treatment. Clinical examination included gingival index (GI), plaque index (PI), probing depth (PD), clinical attachment level (CAL) and gingival bleeding index (GBI), all of which were recorded. Data from 30 patients [19 women and 11 men; mean age, 48.4 (5.4) years old] were analysed. There were statistically significant improvements in GI, PD, CAL and GBI for the SRP + DL group compared to SRP group but no significant difference in PI between the groups. Additionally, the percentage of P.gingivalis-positive sites in the SRP + DL group decreased from 80% (12/15) to 20% (3/15) after laser irradiation (P<0.05). No significant changes were noted in the SRP group. GaAlAs diode laser irradiation of diseased periodontal pockets at 685nm and 1.6Jcm-2 seemed to be an effective adjuvant to mechanical instrumentation to treat chronic periodontitis.

Design and study of nano‐plasmonic couplers using aluminium arsenide and alumina

A theoretical study of nano-plasmonic couplers constructed using aluminium arsenide (AlAs) and alumina (Al2O3) is presented. The analysis has been done using the finite difference time domain technique. The dependence of coupling efficiency on the width of the air layer of silver–air–silver waveguide has been investigated to determine the optimal width of air. Coupling efficiency with the variation in input signal wavelength, reflection coefficient and return loss have been calculated numerically in order to characterise the performance of AlAs and Al2O3 as nano-plasmonic couplers. The resonant peaks have also been obtained for both AlAs and Al2O3. The couplers provide appreciable performance at 1550 nm wavelength and have simple rectangular shape with no tapering which provides advantage in the fabrication process. It also offers broadband operation.

Low-level laser therapy: A biostimulation therapy in periodontics

Low-level laser therapy (LLLT) is a light source treatment that generates light of a single wavelength. The low-level lasers do not cause temperature elevation within the tissue, but rather produce their effects from photobiostimulation effect within the tissues. Low-level lasers do not cut or ablate the tissue. The therapy performed with low-level lasers ia called as LLLT. LLLT devices include the gallium arsenide, gallium aluminum arsenide infrared semiconductor (gallium-aluminum-arsenide), and helium-neon lasers. The output powers range from 50 to 500 mW with wavelengths in the red and near infrared of the electromagnetic spectrum, from 630 to 980 nm with pulsed or continuous-wave emission. The application of LLLT has become popular in a variety of clinical applications in periodontics including promotion of wound healing and reduction of pain following nonsurgical and surgical procedures.