Optical characteristics of bilayer decoupling MoS2 grown by the CVD method.

Study of exciton recombination process is of great significance for the optoelectronic device applications of two-dimensional transition metal chalcogenides (TMDCs). This research investigated the decoupling MoS2 structures by photoluminescence (PL) measurements. First, PL intensity of the bilayer MoS2 (BLM) is about twice of that of the single layer MoS2 (SLM) at low temperature, indicating no transition from direct bandgap to indirect bandgap for BLM due to the decrease of interlayer coupling which can be shown by Raman spectra. Then, the localized exciton emission appears for SLM at 7 K but none for BLM, showing different exciton localization characteristics. The PL evolution with respect to the excitation intensity and the temperature further reveal the filling, interaction, and the redistribution among free exciton states and localized exciton states. These results provide very useful information for understanding the localized states and carrier dynamics in BLM and SLM.

[Spectral characteristics of Ba3SiO4Cl2 : Eu2+ phosphor for white LED].

Ba3SiO4Cl2 : Eu2+ was synthesized by a high temperature solid state method. BaCO3 (A. R.), BaCl2 (A. R.), SiO2 (99.99%) and Eu2O3 (99.99%) were used as the raw materials. The final phase was checked with a conventional X-ray diffraction (XRD) (D/max-rA, CuKalpha, 40 kV, 100 mA, lambda = 0.154 06 nm). The spectral characteristics of the phosphors were performed by using a Hitachi F-4600 fluorescence spectrophotometer equipped with a 450 W Xe lamp. Ba3SiO4Cl2 : Eu2+ showed broad emission bands at 445 and 510 nm under the 365 nm radiation excitation. For the two emission peaks, the excitation spectra have two different spectral distributions, and the excitation peaks locate at 350 and 400 nm, respectively. The results indicate that different Eu2+ emission centres exist in Ba3SiO4Cl2. The emission intensity of the 445 and 510 nm peaks is influenced by Eu2+ doped content. With increasing its content, the emission intensity of 445 nm gradually increases, and that of 510 nm decreases. With washing the phosphor, the 445 nm emission peak disappears, and the emission spectrum has only the 510 nm emission band, and its intensity is lower than that of the original phosphor.

[Spectrum diagnostics for the time of pre-sputtering in thin films deposited by magnetron puttering].

Abstract A plasma analysis system comprised of Omni-X300 series grating spectrometer, CCD data acquisition system and optical fiber transmission system was utilized in the present paper to realize the real-time acquisition of plasma emission spectra during the process of radio frequency (RF) magnetron sputtering. The plasma emission spectra produced by NiTa, TiAl ceramic targets and NiA1, TiA1 alloy targets were monitored respectively, in addition, the behavior of analysis lines of Ta I 333.991 nm, Ni I 362.473 nm, Al I 396.153 nm and Ti I 398.176 nm with time was obtained, according to which the time of pre-sputtering of the four kinds of target materials was fixed. At the same time, for the TiAl alloy target as the research object, the influence of different powers and pressures on the time of pre-sputtering was studied.

[Study on the spectral properties of Ca7(SiO4)2Cl6 phosphor for white LED].

A bluish green Ca7 (SiO4)2Cl6 : Eu2+ phosphor used for UV excited white LED was synthesized by high temperature solid state method. The XRD patterns and luminescence properties were investigated. The results indicated that the sample was single Ca7 (SiO4)2Cl6 phase; the emission spectrum included two emission peaks located at 418 and 502 nm, respectively. Monitoring for the two emission peaks, the excitation spectra were two broad band peaks centered at 290 and 360 nm respectively, which illustrated that Eu2+ ions located at two different crystal lattice sites. The influence of Eu2+ ions concentration on the luminescence intensity was studied and the optimal doping concentration was 0.75 mol%. The results showed that this phosphor was a better candidate bluish phosphor for UV based white LED.

[Effect of KCI additive on laser-induced soil plasma radiation].

In order to improve laser-induced breakdown spectroscopy for low-level elements testing capability, the enhancement effects of KCl additive on the emission spectra of soil samples were studied. The laser spectrum analytical system is composed of a high-energy neodymium glass laser ablating samples, a multifunctional and automatic scanning spectrometer, and a CCD data acquisition system recording plasma spectra. The electron temperature and electron density of plasmas were calculated by measuring spectral line intensity and stark broadening respectively. The experimental results showed that with the increase in the KCl additive, the spectral intensity, signal-to-background ratio, the electron temperature and the electron density all went up firstly and then down. When 15% KCl was added, the radiation intensity of plasma reached the maximum value, the spectral lines intensity of element Mn, Fe, and Ti increased by 2.23, 1.13 and 2.04 than that without additive respectively, the spectral signal-to-background ratio increased by 1.33, 0.89 and 0.94 times respectively; while the electron temperature and electron density of plasmas were heightened by 14% and 38% respectively.

[Spectral characteristics of Ba2B2P2O10 : Eu3+ phosphor].

Ba2B2P2O10 : Eu3+ phosphor was synthesized by high temperature solid-state method. BaCO3(A.R), NH4H2PO4 (A.R), H3BO3(A.R), Eu2O3 (99.99%), NH4Cl (A.R), Li2CO3 (A.R), Na2CO3 (A.R.) and K2CO3 (A.R.) were used for starting materials. After these individual materials were blended and grounded thoroughly in an agate mortar, the homogeneous mixture was heated at 1000 degrees C for 3 h, and the phosphors were obtained. The phase present of the samples were characterized by powder X-ray diffraction (XRD) (D/max-rA, Cu Kalpha, 40 kV, 40 mA, lamda = 0.15406 nm). The spectral characteristics of these phosphors were measured by a SHIMADZU RF-540 fluorescence spectrophotometer. Under the condition of 400 nm excitation, the emission spectrum of Ba2B2P2O10 : Eu3+ phosphor shows several bands at 600, 618, 627 and 660 nm respectively, which correspond to the electric dipole (5)D0-->(7)F1, (7)F2, (7)F3 and (7)F4 transitions of Eu3+. The effect of Eu3+ concentration or charge compensator on the emission intensity of Ba2B2P2O10 : Eu3+ phosphor was investigated, and the result shows that the emission intensity of the phosphor increases with increasing Eu3+ concentration, viz. the concentration quenching has not existed. And the emission intensity of the phosphor was enhanced by doping charge compensator. All the results illuminate that Ba2B2P2O10 : Eu3+ phosphor is a promising red phosphor for white LEDs.

[Enhancing effect of sample additive on laser-induced plasma radiation].

In order to improve the radiation characteristic of laser-induced plasma, with the national standard soil taken as the target sample, a laser spectrum analytical system which composed of a high-energy neodymium glass laser, a multifunctional and compact integrated spectrometer, and a CCD detector was used to detect the influence of the NaCl sample additive on the laser plasma radiation intensity. The electron temperature and the electron density of the plasmas were also calculated from the lines intensity and stark broadening of emission spectral line respectively. The experimental results indicated that with the increase in the NaCl additive, the spectral intensity, signal-to-background ratio, the electron temperature, and the electron density all went up firstly and then down. When 15% NaCl was added, the radiation intensity of the plasma reached the maximum value, the spectral lines intensity of element Mn, K, Fe, and Ti increased by 39.2%, 42.5%, 53.9% and 33.8% compared to that without additive respectively, the spectral signal-to-background ratio increased by 64.4%, 84.39, 44.55% and 58.2% respectively, while the electron temperature and the electron density of the plasmas were heightened by 0.17 times and 0.36 times respectively.

[Spectral properties and energy transfer of Ce3+ and Tb3+ ions co-doped Ca2SrAl2O6 phosphor].

Ce3+, Tb3+ co-doped green phosphor Ca2SrAl2O6 was synthesized by solid state method and its excitation and emission spectra were measured and studied. The results showed that the emission spectrum is composed of four groups of narrow bands and the peaks are located at 497, 545, 595 and 623 nm. The strongest emission peak islocated at 545 nm and chromaticity coordinate (x, y) is (0.300 5, 0.500 2) at 4 mol% Ce3+ and Tb3+ doping, which indicate that Ca2SrAl2O6 : Ce3+, Tb3+ was a good green phosphor. The excitation spectrum for 545 nm was in the region of 320-400 nm, which indicated that this phosphor could be effectively excited by UVLED. Duo to the overlap of the Ce3+ emission bands and the Tb3+ excitation bands, the energy transfer between Ce3+ and Tb3+ is expected to be very efficient. The emission intensity of co-doped Ca2SrAl2O6 phosphor was stronger than that of Tb3+ doped phosphor. The luminescence intensity reached the maximum when the concentration of Ce3+ and Tb3+ was 4 mol%.

[Spectral characteristics of Ce3+ in alkali-alkaline earth borate system].

Alkali-alkaline earth borate LiCaBO3 : Ce3+, LiSrBO3 : Ce3+ and LiBaBO3 : Ce3+ were investigated by solid-state method. CaCO3 (99.9%), SrCO3 (99.9%), BaCO3 (99.9%), Li2 CO3 (99.9%), Na2 CO3 (99.9%), K2 CO3 (99.9%), H3BO3 (99.9%) and CeO2 (99.9%) were used as starting materials, After these individual materials were blended and ground thoroughly in an agate mortar, the homogeneous mixture was heated at 700 degrees C for 2 h in a reduced atmosphere (5 : 95 (H2/N2)), and these three phosphors were obtained. The excitation and emission spectra of these phosphors were measured by a SHIMADZU RF-540 fluorescence spectrophotometer. The spectral characteristics of Ce3+ in alkali-alkaline earth borate LiCaBO3, LiSrBO3 and LiBaBO3 were investigated. The emission spectra of Ce3+ in these three phosphors all exhibited a dissymmetrical band, and the emission peaks were located at 428, 436 and 440 nm, respectively. The excitation spectra for 428, 436 and 440 nm emission of these three phosphors showed a dissymmetrical band at 364, 369 and 370 nm, respectively. The effects of Li+, Na+ and K+ on the emission intensities of these three phosphors were studied. The results show that the emission intensities of these phosphors were enhanced, and the maximal emission intensity of doping Li+ is higher than that of Na+ and K+.

[Study of spectra characteristics of Dy3+ -activated LiSrBO3 phosphor].

The LiSrBO3:Dy3+ phosphor was synthesized by solid-state method. SrCO2 (99.9%), Li2CO3 (99.9%), H3BO3 (99.9%) and Dy2O3 (99.9%) were used as starting materials. After these individual materials were blended and grounded thoroughly in an agate mortar, the homogeneous mixture was heated at 700 degrees C for 2 h in air, and LiSrBO3:Dy3+ phosphors were obtained. The phase present of the samples was characterized by powder X-ray diffraction (XRD) (D/max-rA, Cu Kalpha, 40 kV, 40 mA, lamda = 0.15406 nm). The excitation and emission spectra of these phosphors were measured by a RF-540 photoluminescence spectrophotometer. The emission spectrum of LiSrBO3:Dy3+ phosphor shows several bands at 486, 578 and 668 nm, respectively. The excitation spectrum for 578 nm emission has several excitation bands at 331, 368, 397, 433, 462 and 478 nm, respectively. The effect of Dy3+ concentration on the emission intensity of LiSrBO3:Dy3+ was investigated, and the result shows that the emission intensity of LiSrBO3:Dy3+ phosphor firstly increases with increasing Dy2+ concentration, then decreases, viz. the concentration quenching exists. And the Dy3+ concentration corresponding to the maximal emission intensity is 3 mol%, and the concentration quenching mechanisms are the d-d interaction by Dexter theory.

[Spectrum diagnostics for optimization of experimental parameters in thin films deposited by magnetron sputtering].

The plasma emission spectra generated during the deposition process of Si-based thin films by radio frequency (RF) magnetron sputtering using Cu and Al targets in an argon atmosphere were acquired by the plasma analysis system, which consists of a magnetron sputtering apparatus, an Omni-lambda300 series grating spectrometer, a CCD data acquisition system and an optical fiber transmission system. The variation in Cu and Al plasma emission spectra intensity depending on sputtering conditions, such as sputtering time, sputtering power, the target-to-substrate distance and deposition pressure, was studied by using the analysis lines Cu I 324. 754 nm, Cu I 327. 396 nm, Cu I 333. 784 nm, Cu I 353. 039 nm, Al I 394. 403 nm and Al I 396. 153 nm. Compared with the option of experimental parameters of thin films deposited by RF magnetron sputtering, it was shown that emission spectra analysis methods play a guiding role in optimizing the deposition conditions of thin films in RF magnetron sputtering.

[Effect of ambient atmosphere on laser micro-plasma radiant intensity].

The plasma radiant intensity was investigated by a laser micro-plasma spectral analysis system. The system consists of an YJG-II laser micro-spectral analyzer and a CCD data acquisition and processing system. National standard soil samples were studied in the experiment under different ambient atmosphere with argon, helium and the mixture of argon and helium by using the analysis lines, Ca II 393.367 nm and Ca II 396.847 nm. The results of this research suggest that both the time of plasma illumination and the radiant intensity of plasma in an atmosphere of helium-argon mixture were better than that in pure helium or argon gas. The plasma radiant intensity was obviously enhanced when the proportion of helium and argon was 66.7% and 33.3%, respectively. Under these conditions, the influence of the height of auxiliary electrode on laser micro-plasma radiant intensity was also investigated. The maximum laser micro-plasma radiant intensity was reached when the height of auxiliary electrode was 3 mm.

[Study of enhancement effect of laser-induced crater on plasma radiation].

Single pulses exported from high-energy neodymium glass laser were used to act on the same position of soil sample surface repeatedly, and the plasma emission spectra generated from sequential laser pulse action were collected by spectral recording system. The experimental results show that the laser-induced soil plasma radiation was enhanced continuously under the confinement effect of the crater walls, and the line intensities and signal-to-background ratios both had different improvements along with increasing the number of acting pulses. The photographs of the plasma image and crater appearance were taken to study the plasma shape, laser-induced crater appearance, and the mass of the ablated sample. The internal mechanism behind that laser-induced crater enhanced plasma radiation was researched. Under the sequential laser pulse action, the forming plasma as a result enlarges gradually first, leading to distortion at the trail of plasma plume, and then, its volume diminishes slowly. And also, the color of the plasma changes from buff to white gradually, which implies that the temperature increases constantly. The laser-induced crater had a regular shape, that is, the diameter increased from its bottom to top gradually, thus forming a taper. The mass of the laser-ablated substance descends along with increasing the amount of action pulse. Atomization degree of vaporized substance was improved in virtue of the crater confinement effect, Fresnel absorption produced from the crater walls reflection, and the inverse bremsstrahlung, and the plasma radiation intensity was enhanced as a result.

[Effect of charge compensation on emission spectrum of Sr2SiO4 : Dy3+ phosphor].

The Sr2SiO4 : Dy3+ phosphor was synthesized by the high temperature solid-state reaction method in air. Dy2O3 (99.9%), SiO2 (99.9%), SrCO3 (99.9%), Li2CO3 (99.9%), Na2CO3 (99.9%) and K2CO3 (99.9%) were used as starting materials, and the Dy3+ doping concentration was 2 mol%. The emission spectrum was measured by a SPEX1404 spectrophotometer, and all the characterization of the phosphors was conducted at room temperature. The emission spectrum of Sr2 SiO4 : Dy3+ phosphor showed several bands centered at 486, 575 and 665 nm under the 365 nm excitation. The effect of Li+, Na+ and K+ on the emission spectra of Sr2SiO4 : Dy3+ phosphor was studied. The results show that the location of the emission spectrum of Sr2SiO4 : Dy3+ phosphor was not influenced by Li+, Na+ and K+. However, the emission spectrum intensity was greatly influenced by Li+, Na+ and K+, and the evolvement trend was monotone with different charge compensation, i. e. the emission spectrum intensity of Sr2SiO4 : Dy3+ phosphor firstly increased with increasing Li+ concentration, then decreased. However the charge compensation concentration corresponding to the maximum emission intensity was different with different charge compensation, and the concentration is 4, 3 and 3 mol% corresponding to Li+, Na+ and K+, respectively. And the theoretical reason for the above results was analyzed.

[Spectra characteristics of LiM (M = Ca, Sr, Ba) BO3 : Tb3+ phosphor].

LiM (M = Ca, Sr, Ba) BO3 : Tb3+ phosphors were synthesized by solid state reaction. The starting materials CaCO3, SrCO3, BaCO3, H3 BO3, Li2 CO3, Na2 CO3, K2 CO3 and Tb4 O7 (99.99% in mass) in appropriate stoichiometric ratio were mixed in the alumina crucible, then the mixed powders were calcined at 700 degrees C for 2 h, and LiCaBO3 : Tb3+, LiSrBO3 : Tb3+ and LiB-aBO3 : Tb3+ phosphors were obtained. The emission and excitation spectra were measured by a Shimadzu RF-540 ultraviolet spectrophotometer. All the photoluminescence properties of these phosphors were measured at room temperature. The emission spectra of LiM (M = Ca, Sr, Ba) BO3 : Tb3+ phosphors show several bands, and the main emission peaks correspond to the 5D4 --> 7F6(486, 486, 488 nm), 5D4 --> F5 (544, 544, 544 nm), 5D4 --> 7F4 (590, 595, 593 nm) and 5D4 --> 7F3 (620, 620, 616 nm) typical transitions of Tb3+, and the typical transitions of Tb3+ happens to split because of the effects of LiM (M = Ca, Sr, Ba) BO3 crystals field. The excitation spectra for the 544 nm green emission of LiM (M = Ca, Sr, Ba)BO3 : Tb3+ phosphors illuminate that these kinds of phosphors can be effectively excited by ultraviolet (350-410 nm) light, and emit green light, therefore, they are promising phosphors for white light emitting diodes. Effects of activation and charge compensation on the luminescence intensities of LiM (M = Ca, Sr, Ba) BO3 : Tb3+ phosphors were studied, and the results show that the intensities were obviously effected.

[Enhancing effect of magnetizing solution sample on inductively coupled plasma atomic emission spectrum].

In the present paper, the physics property and nebulization character of the sample solution as well as elemental spectrum intensity were investigated with the prolonging of magnetization time after the water solution with the ethanol was magnetized under magnetic field of 0.24T. The magnetization mechanism was discussed. The experiment result shows that the efficient age-rate of the analyzed sample is increased. The peak values of the spectrum intensity appear when the ethanol is added into the sample. Under the magnetization time of 2 hours, the spectrum intensities of Zn, Pb, Cd, Fe, Si, Cu, Cr and Sr in the sample solution without the ethanol were increased by 22.9%, 38.8%, 25.6%, 48.3%, 52.4%, 6.0%, 22.3% and 22.7% than that with the non-magnetic water, respectively; The signal intensities of the elements in the sample solution with the ethanol of 6% were increased by 22.4%, 42.6%, 39.4%, 72.4%, 43.9%, 9.7%, 16.1% and 17.1% than that with the non-magnetic water, respectively. The detection limit of spectral analysis was reduced when the magnetized sample solution was analyzed.

[Optics heterodyne detection of the autoionization state of barium].

The autoionization state of barium was observed by optics heterodyne between three-photon resonant nondegenerated six-wave mixing (NSWM) and two-photon resonant nondegenerated four-wave mixing (NFWM). In this way, optics heterodyne spectrum of 6p(3/2) 19d autoionization state of barium was measured. The suppression and enhancement of the NFWM signal was observed which was caused by the quantum interference between NFWM and NSWM. Our method is a pure nonlinear optic technique. It has the advantages of excellent spatial signal resolution and simple optical alignment. Here two-photon resonant NFWM is used as local oscillation, while three-photon resonant NSWM signal is used as signal beam. Detection of autoionization states of Ba was achieved by changing the frequency of signal beam. The phase matching condition of this technique is not so stringent and can be achieved over a very wide frequency range, which is very difficult in the general six-wave mixing. Furthermore, the signal is coherent light. Optics heterodyne spectrum is a Doppler-free spectroscopy when the incident lasers have narrow bandwidths.

[The current development of laser-induced plasma spectral analysis technique].

In the present paper, the productions by applying laser-induced plasma spectral analysis technique in different research fields were summarized. Many examples of the application based on laser-induced breakdown spectroscopy (LIBS) and laser-induced plasma spectroscopy (LIPS) methods were introduced, including the substance composition and correlative characteristics of the solid samples (e.g. metal alloy, soil, concrete, mineral, fossil, medicine etc.), liquid samples (e.g. solution, pure water, liquid jets etc.), and gaseous samples (e.g. air, pure gas, vapor and aerosol etc.). Some other investigations and applications were also included. The factors, which influence the detection capability, were discussed. Laser wavelength, pulse energy, power density, environmental atmosphere, external electric field, carbon layer on sample surface, sample material characteristic, and so on all have effects on the precision and the limit of detection. Finally, a simple introduction of the improvements in experimental equipment and methods was also covered. The development of laser-induced plasma spectral analysis technique creates favorable conditions, such as convenience and shortcut, for many science and application researches. It plays an important role in the progress in science and technology.

[Enhancing effect of ethanol additive on the plasma emission in ICP source].

In the present paper, the effects of the ethanol-water solution temperature (20, 40, and 60 degrees C) on the emission intensity of ICP source, plasma parameters (excitation temperature and electron density), physical properties (surface tension and viscosity) of sample solution, and nebulization (uptake rate, effective uptake rate and nebulization efficiency) were studied by using optical-to-electrical detection method. The experimental results showed that the velocity of the sample entering the plasma increased, so that the line intensity of the elements Zn, Fe, Mg, Si, and Sr in water increased obviously with increasing the content of ethanol and the rise of the corresponding solution temperature. And the excitation capacity in the plasma was strengthened with the rise of the ethanol-water solution temperature. The maximal spectrum intensity of the elements Zn, Fe, Mg, Si, and Sr at 60 degrees C was higher by 55.8%, 45.4%, 48.9%, 17.7%, and 21.6% than that at 20 degrees C, respectively. It's valuable for the detection of the trace element.

[Determination of Al and ca in soil by laser micro-plasma spectroscopy].

Laser micro-spectral analyzer, coupled with CCD spectrometer, was used to determine soil elements in argon atmosphere at reduced pressure in the authors' experiment. The accuracy and availability of this method were studied. With Al I 394.40 nm and Ca II 396.85 nm as spectral analysis lines, using "the three standard samples method", the contents of Al and Ca in soil were determined. The results show that the maximum of relative standard deviation (RSD) of quantitative analysis is 5.80%; the maximum of relative difference between the quantitative analysis result and the standard value is 7.65%, suggesting that the accuracy of determination of Al and Ca in soil meets the challenge of quantitative analysis.