Preparation, characterization and photocatalytic activity of N-doped TiO_2 nanocrystals

N-doped TiO2 nanocrystals were prepared using titanium alkoxide as precipitant with different proportional materials. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectra. It is confirmed experimentally that the photocatalytic activity of N-doped TiO2 is much higher than that of Degussa P25, when used for the degradation of crystal violet. The degradation kinetics follows an apparent first-order reaction, which is consistent with a generally observed Langmuir-Hinshelwood mechanism. The doping of TiO2 with nitrogen significantly increases the absorption in the region of visible light. The energy of the band gap of N-doped TiO2 is 2.92 eV. The better performance of N-doped TiO2 can be explained by the fact that it is also excited with longer-wavelength light.

Structure and electrical properties of polysilicon films doped with ammonium tetraborate tetrahydrate

Here,p-type polysilicon films are fabricated by ex-situ doping method with ammonium tetraborate tetrahydrate(ATT)as the boron source,named ATT-pPoly.The effects of ATT on the properties of polysilicon films are comprehensively analyzed.The Raman spectra reveal that the ATT-pPoly film is composed of grain boundary and crystalline regions.The preferred orientation is the(111)direction.The grain size increases from 16−23 nm to 21−47 nm,by~70%on average.Comparing with other reported films,Hall measurements reveal that the ATT-pPoly film has a higher carrier concentration(>10^(20)cm^(−3))and higher carrier mobility(>30 cm2/(V·s)).The superior properties of the ATT-pPoly film are attributed to the heavy doping and improved grain size.Heavy doping property is proved by the mean sheet resistance(Rsheet,m)and distribution profile.The R_(sheet,m)decreases by more than 30%,and it can be further decreased by 90%if the annealing temperature or duration is increased.The boron concentration of ATT-pPoly film annealed at 950℃ for 45 min is~3×10^(20)cm^(−3),and the distribution is nearly the same,except near the surface.Besides,the standard deviation coefficient(σ)of Rsheet,m is less than 5.0%,which verifies the excellent uniformity of ATT-pPoly film.

Growth and Holographic Storage Properties of Sc, Fe Co-Doped Lithium Niobate Crystals

The holographic storage properties of Fe （0.03% （mass fraction） Fe2O3）：LiNbO3 doped with Sc at different levels （0, 1%, 2%, 3%） were investigated. The Sc threshold concentration in Fe：LiNbO3 was implied to be about 3% （mole fraction） because O-H vibration absorption peak of Sc （3%）：Fe：LiNbO3 was at 3508 cm^-1, compared with 3484 cm^-1 of crystals with lower Sc doping level. Sc（3%）：Fe：LiNbO3 exhibited higher optical damage resistance ability. The threshold intensity （wavelength 488 nm） of Sc （3%）：Fe：LiNbO3 was 2.2 ×10^2 W ·cm^-2, two orders of masnitude higher than that of Fe：LiNbO3. Holographic storage properties of the crystals were determined in an extraordinary polarized laser of wavelength 632.8 nm by a two-wave coupling method. It was found that in terms of holographic storage properties, the optimal doping concentration of Sc was 2% （mole fraction） among this crystal series.

Growth Techique of Sodium Bismuth Tungstate Crystal Doped by Nd

Nd∶NBW laser crystal with the size of Φ8 mm×20 mm was grown by the process of lifting and pulling. The growth technological parameters which have influence on the completeness of crystal were analyzed and the reasonable technological parameters were ascertained.

Optical and defect properties of S-doped and Al-doped GaSe crystals

S-doped and Al-doped GaSe crystals are promising materials for their applications in nonlinear frequency conversion devices. The optical and defect properties of pure, S-doped, and Al-doped GaSe crystals were studied by using photoluminescence（PL） and Fourier transform infrared spectroscopy（FT-IR）. The micro-topography of（0001） face of these samples was observed by using scanning electron microscope（SEM） to investigate the influence of the doped defects on the intralayer and interlayer chemical bondings. The doped S or Al atoms form the SSe^0 or AlGa^＋1） substitutional defects in the layer GaSe structure, and the positive center of AlGa-^＋1 could induce defect complexes. The incorporations of S and Al atoms can change the optical and mechanical properties of the GaSe crystal by influencing the chemical bonding of the layer structure. The study results may provide guidance for the crystal growth and further applications of S-doped and Al-doped GaSe crystals.

Growth and annealing study of hydrogen-doped single diamond crystals under high pressure and high temperature

A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 C to 1350 C.It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization.Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp 3-CH 2-symmetric（2850 cm-1） and sp 3 CH 2-antisymmetric vibrations（2920 cm-1）.The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst.The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm-1 to 1333.05 cm-1 and gives rise to some compressive stress in the diamond crystal lattice.Furthermore,hydrogen to carbon bonds are evident in the annealed diamond,indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm-1 have no observable shift.Therefore,we suggest that the sp 3 C-H bond is rather stable in diamond crystals.

Growth and Properties of In-Doped Semi-insulating GaAs Crystals

Semi-insulating (SI) GaAs doped with indium has been grown and characterized. The relationship between the dislocation density and dopant concentration has been discussed. Study of the uniformity of electric properties of In-doped SI-GaAs, which has been annealed at 950°C for 6h under arsenic pressure, associates with decreases of point defects and arsenic vacancies.

Growth of gem-grade nitrogen-doped diamond crystals heavily doped with the addition of Ba(N_3)_2

Additive Ba（N3）2 as a source of nitrogen is heavily doped into the graphite-Fe-based alloy system to grow nitrogendoped diamond crystals under a relatively high pressure （about 6.0 GPa） by employing the temperature gradient method. Gem-grade diamond crystal with a size of around 5 mm and a nitrogen concentration of about 1173 ppm is successfully synthesised for the first time under high pressure and high temperature in a China-type cubic anvil highpressure apparatus. The growth habit of diamond crystal under the environment with high degree of nitrogen doping is investigated. It is found that the morphologies of heavily nitrogen-doped diamond crystals are all of octahedral shape dominated by {111} facets. The effects of temperature and duration on nitrogen concentration and form are explored by infrared absorption spectra. The results indicate that nitrogen impurity is present in diamond predominantly in the dispersed form accompanied by aggregated form, and the aggregated nitrogen concentration in diamond increases with temperature and duration. In addition, it is indicated that nitrogen donors are more easily incorporated into growing crystals at higher temperature. Strains in nitrogen-doped diamond crystal are characterized by micro-Raman spectroscopy. Measurement results demonstrate that the undoped diamond crystals exhibit the compressive stress, whereas diamond crystals heavily doped with the addition of Ba（N3）2 display the tensile stress.

Synthesis and characterization of A1 doped δ-laminar crystal sodium silicate

An modified laminar crystal sodium silicate （A1-SKS-6） was synthesized by spray drying and high temperature crystallization using sodium silicate as silicon source, A1 atom as inorganic source and hexadecyltrimethy ammonium bromide （CTMAB） as the structure template. The hydrothermal stability of product was at least 1 h. The synthesized material was characterized by XRD and SEM. The results indicated that shape and intensity of XRD diffraction peak at 20 took changes, but raw material 8 phase crystal form kept unchanged, and assured high Ca^2＋ and Mg^2＋ binding capacity of the products. The Ca^2＋ and Mg^2＋ binding capacity of product is up to 380 mg Ca/g and 410mg Mg/g respectively. It was found that the hole of product became smaller and appeared rod structure based on SEM. The hydrothermal stability was increased due to the pillaring of AI atom.

Up-conversion luminescence properties and energy transfer of Er^(3+)/Yb^(3+)co-doped oxyfluoride glass ceramic containing CaF_2 nano-crystals

The Er^3＋/yb^3＋ co-doped transparent oxyfluoride glass-ceramics containing CaF2 nano-crystals were successfully prepared. After heat treatments, transmission electron microscopy （TEM） images showed that CaF2 nano-crystals of 20-30 nm in diameter precipitated uniformly in the glass matrix. luminescence of Er^3＋ at 540 nm and 658 nm was observed in Comparing with the host glass, high efficiency upconversion the glass ceramics under the excitation of 980 nm. Moreover, the size of the precipitated nano-crystals can be controlled by heat-treatment temperature and time. With the increase of the nano-crystal size, the intensity of the red emission increased more rapidly than that of the green emission. The energy transfer process of Er^3＋ and Yb^3＋ was convinced and the possible mechanism of Er^3＋ up-conversion was discussed.

Formation Enthalpy Calculation of Oxygen Vacancy Defect in Doped Lithium Niobate Crystals

The relationship between temperature and oxygen vacancy concentration is deduced in this paper. Based on the data of thermal weight-loss experiment, the formation enthalpies of congruent and several doped LN crystals have been calculated. It was found that the formation enthalpy of oxygen vacancies can be decreased evidently by doping valence-changeable ions. The experimental results were discussed and a new reduction process of the photorefractive LN crystal at a relatively low temperature was proposed, and the reduced crystals showed a good effect in practical use.

Loss of Light Yield of Doped Lead Tungstate Crystals After Irradiation

Loss of light yield of doped lead tungstate crystals after irradiation with a low dose rate has been observed.The La,Pr,and Y doping may improve radiation hardness,whereas Bi or Mo doping is harmful.

Growth of Pure and Mo Doped Potassium Titanyl Phosphate (KTP) Crystals:Influence of KTP/Flux Ratios on the Growth Morphology

Pure and Molybdenum (Mo) doped Potassium Titanyl Phosphate (KTP) inorganic crystals were grown by high temperature solution growth (HTSG) from poly phosphate (K6P4O13) flux using different KTP/Flux ratios. The pure and doped KTP crystals of size 20x13x5 mm3 and 7x5x2.5 mm3 respectively were grown successfully by spontaneous nucleation. The grown crystals were characterized by XRD, UV, FTIR and Hardness studies. Micro hardness studies show that the pure crystals are harder than the Mo doped crystals.

Preparation and Gas-sensing Characteristics of Na^+-doped ZnO Single Crystals

ZnO single crystals were grown by vapor phase reaction of Zno powder with active carbon powdei at an elevated temperature The typical crystals were colorless and transparent with maximum size o4 0.1 mm in diameter and 25 mm in length, The gas-sensing characteristics of Na+-doped anc undoped single crystals were investigated in 1 %H2. Co and CH, in air between 1 50 and 600℃. It was found that the undoped ZnO single crystals showed little gas sensitivity in air. and Na+-doping can greatly enhance the senstivity by increasing the resistivities. The maximum sensitivity of the samples is 22 (Ra/ Rg) for H2. 1 2 for CO and 4 for CH4

Single crystal growth and electronic structure of Rh-doped Sr_(3)Ir_(2)O_(7)

Ruddlesden-Popper iridate Sr_(3)Ir_(2)O_(7)is a spin-orbit coupled Mott insulator.Hole doped Sr_(3)Ir_(2)O_(7)provides an ideal platform to study the exotic quantum phenomena that occur near the metal-insulator transition(MIT)region.Rh substitution of Ir is an effective method to induce hole doping into Sr_(3)Ir_(2)O_(7).However,the highest doping level reported in Sr_(3)(Ir_(1-x)Rh_(x))_(2)O_(7)single crystals was only around 3%,which is far from the MIT region.In this paper,we report the successful growth of single crystals of Sr3(Ir_(1-x)Rh_(x))_(2)O_(7)with a doping level of~9%.The samples have been fully characterized,demonstrating the high quality of the single crystals.Transport measurements have been carried out,confirming the tendency of MIT in these samples.The electronic structure has also been examined by angle-resolved photoemission spectroscopy(ARPES)measurements.Our results establish a platform to investigate the heavily hole doped Sr_(3)Ir_(2)O_(7) compound,which also provide new insights into the MIT with hole doping in this material system.

Studies of Photorefractive Crystals of Cu-Doped (K_(0.5) Na_(0.5))_(0.2)(Sr_(0.75)Ba_(0.25))_(0.9)Nb_2O_6

In this paper, photorefractive crystals of Cu-doped (K0.5Na0.5)0.2 (Sr0.75Ba0.25)0.9Nb2O6 (KNSBN) are systematically studied. A series of Cu-doped KNSBN crystals have been grown and the samples with Cu-dopant in different levels and thicknesses have been fabricated. Their photorefractive properties including two-wave coupling gain coefficients and response rate are experimentally studied in details. The results show that (1) with high Cudopant cocentration, the crystal has larger coupling gain coefficient, higher effective charge carrier density, and faster time response; (2) thinner sample shows larger coupling gain coefficientl (3) at shorter wavelength 9 the crystal sample shows larger coupling gain coefficient and faster time response. The Cu-doping mechanisms were briefly referred. The analyses of the relationships among the crystal’s two-wave coupling, absorption property and the self-pumped phase conjugation are given. All the results show that Cu-doped KNSBN crystals are a kind of very promising photorefractive materials.

Synthesis and Crystal Structure of Yb-doped S-FAP

To abtain large crystals for improving the physical and optical properties of materials, the crystal of Yb-doped S-FAP was sythesized by the Czochralski method, the growth process was analyzed, and its structure was determined. This material was confirmed to have a hexagonal structure, unit-cell parameters （a=b-0.9683（4） nm, c=0.7277（4） nm） are slightly different from the crystal parameters of S-FAP reported before.

Effect of Growth Parameters on Core Length of Φ76．2mm Heavily Sb－doped Si Crystals

An M-shaped interface was observed in the top part of Φ76. 2 mm , (111) , dislocation-free, heavily Sb-doped Si single crystals, which is beneficial for crystals to keep dislocation-free condition at the beginning ofbody growth. Effects of seed rotation, crucible rotation , crown shape and growth rate on M-shaed interfacewere studied. Under proper conditions, impurity core length can be shortened from 6 cm to 1 cm , the yield israised by more than 5 %.

Microscale Crystalline Rare-Earth Doped Resonators for Strain-Coupled Optomechanics

Rare-earth ion doped crystals for hybrid quantum technologies are an area of growing interest in the solid-state physics community. We have earlier theoretically proposed a hybrid scheme of a mechanical resonator which is fabricated out of a rare-earth doped mono-crystalline structure. The rare-earth ion dopants have absorption energies which are sensitive to crystal strain, and it is thus possible to couple the ions to the bending motion of the crystal cantilever. This type of resonator can be useful for either investigating the laws of quantum physics with material objects or for applications such as sensitive force-sensors. Here, we present the design and fabrication method based on focused-ion-beam etching techniques which we have successfully employed in order to create such microscale resonators, as well as the design of the environment which will allow studying the quantum behavior of the resonators.

The Radiation Damage Mechanism of Rare Earth Doped BaF_2 Crystals

The Discrete variation Xα（DV-Xα）method was used to calculate the energylevel of some rare earth doped BaF2 crystals.The results indicated that elements Eu,Dyand Yb will change their valence from +3 to +2 under irradiation and thus change theoptical properties of the crystals.The calculation using radiation damage model agreeswell with experiments.