EL Measurement Research Articles

Direct Band-gap 1.64μm Electroluminescence from Edge Emitting Germanium Diode for Near-infrared Application

Germanium has been considered as a promising material for near-infrared optical devices due to its higher carrier mobility and adjustable band structure. In this study, the low temperature combined with high temperature (LT-HT) two-step method is utilized to fabricate the edge emitting germanium diode who can be an application for near infrared. The tensile strain of the germanium layer is determined by XRD and Raman, which are about 0.3%. The TEM results show a high material quality near the surface of the Ge layer with few defects at the Si/Ge interface. Then, the chip is packaged to facilitate testing and protect the device. The I-V characteristics indicate a reserve saturation current of about 10−3A/cm2 at -0.1V in the dark. The EL measurement with a stable EL peak at 1640nm was observed.

53‐2: Mini LED Emissive Display Product with Pitch 0.5mm Based on MIP Chips

In this work, we design a new type of LED chips named MIP (Micro LED in package) chips which are composed of three or more sub‐pixel LED chips. Compared with traditional Micro LED chips, MIP can achieve EL measurement and high transfer yield. The structure and optical performance of MIP chips are demonstrated in this work. Moreover, based on MIP chips, we successfully made a Mini LED emissive display product with the pitch 0.5 mm. Such MIP chips provide a new choice for Mini LED display with small pixel pitch.

Synthesis of ZnS Quantum Dots for QDs-LED hybrid device with different cathode materials

In this study, a chemical method was used to synthesise ZnS quantum dots (QDs) with low cost and simple process. A fixed molar ratio 1:1 of zinc chloride and sodium sulfide has been used for preparing two samples A and B. The X-ray diffraction (XRD) analyses prove the cubic phase of ZnS with an average particles size of (3-29) nm According to UV-Vis. spectra analyses, a large blue shift over 32 and 48 nm was observed, while the band gaps energy (Eg) were 3.55 and 3.8 eV for A and B samples respectively. The emission spectrum of quantum dots carries more evidence on the presence of shallow at 373 and 367 nm originated from the interstitial Zn and traps at 428 and 439 nm, whose origin ascribed to defects zinc vacancy (VZn), while 541 nm was due to sulfide vacancy (VS). QDs-LED hybrid devices were fabricated using ITO/PEDOT: PSS/Poly-TPD/ZnS-QDs/layers with two types of cathode materials LiF and Al. Using LiF as cathode in addition to the Al gives good enhancement to light generation in compares with that of Al cathode only. The spectra 350-700 nm appeared a wide emission band according to the EL measurement.

Properties of a CdZnO/ZnO multiple quantum-well light-emitting diode

A CdZnO/ZnO multiple quantum-well light-emitting diode (LED) structure was successfully grown by using plasma-assisted molecular beam epitaxy on a p-GaN template that had been grown by using metal-organic chemical-vapor deposition on a c-sapphire substrate. The properties of the sample were characterized by using high-resolution X-ray diffraction, transmission electron microscopy, and temperature-dependent photoluminescence measurements. The light output performance of the CdZnO/ZnO QW LED device was also investigated in detail by using I-V and electroluminescence spectral measurements. The characterization showed that our CdZnO/ZnO QW LED structure had good crystalline quality and weaker carrier localization. Owing to the heterojunction structure, the I-V curve indicated that the LED device had a higher turn-on voltage and series resistance. The EL measurement demonstrated that for our LED device’s optoelectronic characteristic, the carrier-screening effect played the dominant role in the emission-energy blue-shift mechanism, and the broadening of the emission energy width was mainly ascribed to the band-filling effect. Without a special heat sinking, the L-I curve exhibited slight efficiency droop after 30 mA.

The electroluminescence mechanism of non-doping PhOLEDs based on CBP/Ir(ppy)3 investigated by delayed EL measurements

In this paper, the non-doped PhOLED based on 4,4′-bis(9-carbazolyl)-1,1′-biphenyl(CBP) and fac-tris(2-phenylpyridine) iridium(Ir(ppy)3) with the emitting layer of [CBP/Ir(ppy)3]n/CBP in which n is equal to 2,3,4 and 5, respectively, are prepared. The electroluminescence and the luminance-voltage-current density characteristics of devices are detected. The wavelength range of these devices is varied from 517 nm to 540 nm. And the delay EL measurements are used to elucidate the carrier recombination and light emission mechanism in non-doped PhOLEDs. In this technique, the devices are driven using a square pulse driving scheme, with a forward bias pulse width of 1 ms, which is sufficiently long for prompt EL to reach its steady-state intensity. The delay EL results show that changing the number of the non-doped EML leads to marked changes in the charge-trapping and host–host TTA patterns, which suggests that the carrier transport and recombination processes depends on the number of non-doped EML. When the number of non-doped EML is less than 3, only the trapped carrier recombination signal are detected in the delay EL measurement. For the devices with more non-doped EML than 3, both the trapped carrier recombination and host–host TTA signal are detected. All these results are discussed and give the evidence for the electroluminescence mechanism of prepared devices.

A comparative assessment of the accuracy of electronic apex locator (Root ZX) in the presence of commonly used irrigating solutions

Objectives: This study aimed to evaluate the accuracy of Root ZX in determining working length in presence of normal saline, 0.2% chlorhexidine and 2.5% of sodium hypochlorite. Material and Methods: Sixty extracted, single rooted, single canal human teeth were used. Teeth were decoronated at CEJ and actual canal length determined. Then working length measurements were obtained with Root ZX in presence of normal saline 0.9%, 0.2% chlorhexidine and 2.5% NaOCl. The working length obtained with Root ZX were compared with actual canal length and subjected to statistical analysis. Results: No statistical significant difference was found between actual canal length and Root ZX measurements in presence of normal saline and 0.2% chlorhexidine. Highly statistical difference was found between actual canal length and Root ZX measurements in presence of 2.5% of NaOCl, however all the measurements were within the clinically acceptable range of ±0.5mm. Conclusion: The accuracy of EL measurement of Root ZX within±0.5 mm of AL was consistently high in the presence of 0.2% chlorhexidine, normal saline and 2.5% sodium hypochlorite. Clinical significance: This study signifies the efficacy of ROOT ZX (Third generation apex locator) as a dependable aid in endodontic working length. Key words:Electronic apex locator, working length, root ZX accuracy, intracanal irrigating solutions.

Improved Yellow Light Emission in the Achievement of Dichromatic White Light Emitting Diodes

ABSTRACTA study about the achievement of dichromatic white light-emitting diodes (LEDs) was performed. A series of dual wavelength LEDs with different last quantum-well (LQW) structure were fabricated. The bottom seven blue light QWs (close to n-GaN layer) of the four samples were the same. The LQW of sample A was 3 nm, and that of sample B, C and D were 6 nm, a special high In content ultra-thin layer was inserted in the middle of the LQW of sample C and on top of that of sample D. XRD results showed In concentration fluctuation and good interface quality of the four samples. PL measurements showed dual wavelength emitting, the blue light peak position of the four samples were almost the same, sample A with a narrower LQW showed an emission wavelength much shorter than that of sample B, C, D. EL measurement was done at an injection current of 100 mA. Sample A only showed LQW emission due to holes distribution. Because of wider LQW, the emission wavelength of sample B, C and D was longer and peak intensity was weaker. Sample D with insert layer on top of LQW showed strongest yellow light emission with a blue peak. As the injection current increased, sample A showed highest output light power due to narrower LQW. Of the other three samples with wider LQW, sample D showed highest output power. Effective yellow light emission has always been an obstacle to the achievement of dichromatic white LED. Sample D with insert layer close to p-GaN can confine the hole distribution more effectively hence the recombination of holes and electrons was enhanced, the yellow light emission was improved and dichromatic white LED was achieved.

Evaluation of Cold Hardiness in Seven Iranian Commercial Pomegranate (Punica granatum L.) Cultivars

Freezing injury is one of the most important limiting factors in commercial pomegranate production. The objectives of this study were to compare cold hardiness of seven Iranian pomegranate cultivars at three stages: November, January, and March, and to investigate the relationship between freezing tolerance and soluble carbohydrate and proline changes of shoots during acclimation and deacclimation. LT50 values, estimated by both electrolyte leakage measurement (EL LT50) and tetrazolium stain test (TST LT50), allowed us to discriminate between the cultivars in terms of freezing tolerance. Acclimation and deacclimation did not occur simultaneously in different cultivars, having a key role in cold tolerance of cultivars, especially in fall and late winter. Post Sefid Bafgh cultivar showed high cold tolerance early in fall, but it was susceptible to cold during winter. ‘Naderi’, ‘Yusef Khani’, ‘Malas Saveh’, and ‘Robab Neyriz’ had the highest midwinter cold hardiness; ‘Mahabadi’ showed an intermediate hardiness, whereas ‘Post Sefid Bafgh’ and ‘Shishe Kap’ were found to be cold-susceptible in this period. Freezing tolerance estimated by TST corresponded to those measured by the EL method in all cultivars, but in November and January, higher variation in freezing tolerance was observed among the cultivars through TST compared with EL measurement. However, LT50 values, estimated by EL measurement, were lower than those estimated through TST in November and March. Soluble carbohydrate concentrations of stem samples increased during cold acclimation from November to January; then it decreased in March. Proline had a narrow range of variation among the cultivars in November, but an increase in the amount of proline was observed during the period of hardening. In general, stronger correlations were observed between LT50 values and the amounts of soluble carbohydrates compared with proline, particularly from fall to midwinter.

Modélisation par éléments finis du chauffage infrarouge des membranes thermoplastiques semi-transparentes

Resume Dans cette etude, nous avons etabli par la methode des elements finis en trois dimensions une approche simplifiee pour analyser l'evolution de la temperature au sein d'une membrane semi-transparente de type polyethylene terephtalate (PET) amorphe, exposees a une source radiative. En se basant sur le comportement optique du PET, un transfert radiatif monodirectionnel, suivant l'epaisseur de la membrane est considere. Des simulations numeriques ont permis de confronter et de valider les resultats obtenus vis-a-vis des resultats analytiques et experimentaux. Comme application, nous avons etudie le chauffage d'une feuille thermoplastique en PET exposee a une source radiative infrarouge.

Relationship of Emotional Intelligence and Adherence to Combination Antiretroviral Medications by Individuals Living With HIV Disease

Medications are an intentional and purposeful means to the successful management of many chronic diseases. In the treatment of disease caused by HIV, adherence to medication is of particular concern because any level of nonadherence, often a few missed doses, will lead eventually to the development of drug resistance. Many predictors of poor adherence to HIV medications have been identified as significant factors in adherence. Among these is the emotional aspect. The purpose of this study was to examine emotional intelligence (EI) and adherence to combination antiretroviral therapy in individuals who are infected with HIV. EI is defined as the ability to perceive and express emotions, facilitate emotions, understand and reason with emotion, and manage emotions. EI has been correlated with various aspects of success in life. In this study, EI was measured by the Mayer, Salovey, Caruso Emotional Intelligence Test. Adherence to medications was measured by self-report and defined as less than 10% missed doses of medications. Eighty-two participants were recruited from an urban hospital-based HIV clinic. Pearson's r was used to analyze the data for significance, and no correlation was reported. This data set was not large enough to prove significance, statistically, of the research question. However, an unexpected result of this study was that the overall EI scores for this particular population were markedly lower than the test norms. Further study would be warranted and recommended to explore El measurement in people at risk for HIV disease or in those who have the disease to further understand the impact of emotions and EI in this specific population.

Improved characteristics of GaN-based light-emitting diodes by distributed Bragg reflector grown on Si

We report the improved characteristics of GaInN light-emitting diodes (LEDs) on Si substrates by a distributed Bragg reflector (DBR). The DBR-based GaInN multi quantum-well LED structures were grown on n-Si (111) substrates using a conventional horizontal metalorganic chemical vapor deposition method. The number of Al0.3Ga0.7N/AlN pairs in the DBR was changed from 1 to 5. The measured PL peak intensity ratio agrees well with the calculated value. In an EL measurement, the output power increases with an increase in the number of pairs in the DBR (less than 3 pairs). The light output power of a 3-pair DBR-based LED is approximately twofold larger than that of a non-DBR-based LED. However, it significantly decreases in a 5 pair of DBR, because of a crack formation. Although the suppression of crack formation remains a problem, the DBR is still very promising for the fabrication of high-performance LEDs on Si. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Accuracy of a new apex locator: an in vitro study.

The purpose of this study was to test in an in vitro model the accuracy of a Bingo 1020 electronic apex locator, to compare the results to those of a well known apex locator, Root ZX, as well as to those of the radiographic method of tooth length determination. A total of 120 extracted teeth, preserved in Thymol solution and kept refrigerated, was used for the study. The experiment was performed on single-rooted teeth and on one-root canal, chosen randomly, in multirooted teeth. The teeth were randomly divided into 12 groups of 10 teeth each. After access preparation, the actual length (AL) was measured. The teeth were embedded in an alginate model specially developed for testing apex locators. Electronic tooth length measurements (EL) were carried out prior to root canal preparation using the two electronic apex locators (EAL) - Root ZX and Bingo 1020; three measurements were taken and an average computed. After the third measurement, the file was left in the root canal and a periapical radiograph was taken. The radiographic length (RL) was recorded by measuring the file length from the coronal reference point to the tip of the file. Each root canal was then prepared to a no. 40 K-file diameter using a standardized technique; saline was used for irrigation. Upon completion of the root canal preparation, EL measurements were taken by each EAL in dry conditions and with different irrigation solutions. Each measurement was repeated three times. The RL was recorded according to the last EL measurement. Results were subjected to statistical analysis. In all parameters tested, a significant statistical difference was found between Bingo 1020 and the Root ZX. Measurements obtained using the Bingo 1020 were consistently closer to the AL (0.08 mm) than those obtained using the Root ZX. Both EALs measured the tooth length with great accuracy and a positive correlation of 0.76 (P = 0.00) existed between the two devices. No significant difference was found between the two apex locators when measurements were taken with the different irrigants (P = 0.34) and the content of the root canal did not affect the accuracy of the measurements. Lengths obtained by calculations from the radiographs were longer than the AL as well as the length obtained by both EALs (P = 0.00). The Bingo 1020 proved to be as reliable as Root ZX and was user friendly. Under the experimental conditions, electronic measurements were more reliable than radiographs in the process of root length determination.