Doped Single Crystals Research Articles

Structural Modifications due to Bi-Doping in MAPbBr3 Single Crystals and Their Impact on Electronic Transport and Stability.

Doping strategy in lead halide perovskites is essential to enhance its optoelectrical properties and expand the potential applications. In this work, the mechanisms, for how dopants affect the overall structural, optical, electrical, and chemical properties and stability of lead halide perovskite materials, are investigated. This is done by specifically considering various bismuth (Bi)doping concentrations in MAPbBr3 single crystals grown using the inverse temperature crystallization method. The resultant doped single crystals exhibit a saturation point when Bi concentration exceeds 0.063% which is considered an optimum doping point. The highest thermal stability is also achieved at this doping concentration among the doped single crystals. This study clearly identifies how Bi doping affects the properties of MAPbBr3 and extends to consider stability, which has not been fully considered for MA-based perovskites previously. This will provide a clear understanding of evaluating doped perovskite materials for enhanced material properties, device performance, and stability.

Photoluminescence and scintillation properties of rare earth doped Lu2O3 single crystal grown by floating zone method

A series of Lu2O3 single crystals doped with rare earth (RE) ions (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb, dopant concentrations are 1 %) was synthesized by the floating zone method. Their photoluminescence (PL) and scintillation properties were evaluated. In PL, emissions due to 4f-4f transitions of trivalent rare earth ions were observed, and those doped with Nd3+, Eu3+, Tb3+ and Er3+ showed the highest emission intensities among the samples. As a scintillation property, those doped with Eu, Gd, and Dy showed a clear photoabsorption peak under 137Cs 662 keV γ-ray irradiation. Among them, the Eu3+-doped Lu2O3 showed the highest scintillation light yield of 67000 photons/MeV. The current work conducted the first systematic study of rare earth doped Lu2O3 single crystals grown by the floating zone method.

Er3+ doped BZBO single crystal: Growth and electro-elastic property characterization

Large-sized and high-quality Er: Bi2ZnB2O7 (Er: BZBO) single crystal has been grown using the Kyropoulos method. The crystal structure is refined by the Rietveld method, Er: BZBO belongs to the orthorhombic system and space group Pba2, lattice parameters: a = 10.811(1) Å, b = 11.006(1) Å, c = 4.8817(4) Å, which are slightly reduced after doping with Er3+. The thermal expansion anisotropy is studied and shows a decrease with coefficients of α11 = 7.69(1) × 10−6 K−1, α22 = 9.90(9) × 10−6 K−1, and α33 = 1.98(8) × 10−6 K−1, respectively. The relative dielectric constants are found to be εT11/ε0 = 32.8(1), εT22/ε0 = 17.2(1), and εT33/ε0 = 17.0(9), respectively. The dielectric, elastic, and piezoelectric constants for the Er: BZBO crystal are determined by the impedance method, with the piezoelectric coefficients d15, d24, d31, d32 and d33 are measured as 1.1(9), −5.4(2), 1.8(7), −5.9(1) and 1.1(5) pC/N, respectively. Furthermore, the temperature dependence of the piezoelectric coefficients from room temperature to 500 °C is evaluated, showing good temperature stability for d24 and d32 with variations were −7 % and 13 %, respectively.

Femtosecond Laser‐Induced Regulation of Photo‐ and Persistent Luminescence of Perovskite Crystals

AbstractManipulation of photoluminescence (PL) and persistent luminescence (PersL) provides a powerful tool for anti‐counterfeiting applications. Here, Sb3+‐doped CsCdCl3 perovskite single crystals (SCs) can be selectively irradiated via utilizing ultra‐fast femtosecond (fs) laser, creating tunable PL colors and PersL duration with high precision. The PL color of the synthesized SCs changes from cyan to orange along with the wavelength of the fs laser, for the successful regulation of the optical procedure from a single‐photon to a two‐photon absorption process. Moreover, an orange PersL of CsCdCl3:Sb3+ SC is observed after being charged with a fs laser, and the corresponding duration time can be feasibly controlled with the pump wavelength. In particular, CsCdCl3:Sb3+ is capable of ultrafast carrier capture (1 s) under fs laser compared to ultraviolet lamp pre‐irradiation enabling a high‐resolution micro‐PersL in photon trapping/de‐trapping modes. These findings not only give a new solution for the fabrication high‐resolution micro‐PL and trajectory‐writing micro‐PersL patterns, but also provide a deep insight to understand the photon–matter interactions.

Na5Y9F32:Yb3+/Ho3+/Tm3+ up-conversion luminescent single crystals for highly sensitive optical temperature sensor

A novel non-contact optical temperature sensor with excellent performance of its adequate temperature resolution (δ(T) = 0.017 K) and exceptional relative thermal sensitivity (Sr = 1.97% K−1) was developed based on the up-conversion fluorescence intensity ratio (FIR) of Ho3+/Tm3+/Yb3+ triply incorporated Na5Y9F32 single crystal grown by Bridgman method. The up-conversion (UC) emission bands at 482 nm/669 nm/700 nm of Tm3+ and 522 nm/542 nm/653 nm of Ho3+ ions were observed upon excitation of 980 nm. The effects of Yb3+ concentration from 0.5 to 4 mol% on the UC emission of the Ho3+/ Tm3+ fixed doped Na5Y9F32 single crystal were also carried out. It has been demonstrated through the calculation of the steady-state rate equation that the intensity of UC emission is linearly heightened with the pump power, confirming the conversion mechanism. The temperature sensing performance of the Ho3+/Tm3+/Yb3+ incorporated Na5Y9F32 single crystals was explored by analyzing the FIR employing thermally coupled energy levels (TCLs) and non-thermally coupled energy levels (NTCLs). The maximum values of absolute sensitivity (Sa) and relative sensitivity (Sr) of the material are estimated to be 19.1% K−1 (323 K) and 1.97% K−1 (398 K), separately, which are far higher than those of previously reported RE3+-doped UC optical temperature sensor materials. This study shows that the transparent single crystal has the great potential as a non-contact optical thermometer, and provides a new idea for studying other highly optical sensing materials.

Theoretical evaluation on the possibility of laser cooling and simultaneous temperature sensing in Er3+ doped LiYF4 single crystal

In our previous work, a novel laser cooling method was developed using anti-Stokes fluorescence from thermal equilibrium levels of Er3+, with its efficacy proven in Er3+ doped ZBLAN glass. This study has extended the method to Er3+ doped LiYF4 single crystal, where anti-Stokes fluorescence from 2H11/2 is utilized by excitation at the 4S3/2 level of Er3+ for optical in situ temperature control. The non-radiative and radiative transition probabilities among 4f levels of Er3+ were assessed, and the populations of all levels relevant to laser cooling and temperature sensing were calculated. Results demonstrate that the Er3+ doped LiYF4 crystal achieves effective cooling within a specific temperature range, exhibiting high temperature sensitivity.

Optical and scintillation properties of Pr3+-doped (La, Y)2Si2O7 single crystals

Pr-doped scintillators are attracting attention because of their potential applications in medical devices. In this study, we focused on Pr-doped (La, Y)2Si2O7 scintillators to grow single crystals by the micro-pulling-down method and to evaluate their optical and scintillation properties. From the powder XRD results, the crystal structure and the space group were identified to be monoclinic and P21/n, respectively. The results of optical and scintillation characterization show that the luminescence from the Pr3+ 5d1–4f transition increases with increasing Pr3+ concentration. The maximum light yield was also obtained for the sample with the highest Pr3+ concentration. The Pr-doped (La, Y)2Si2O7 single crystal shows promising properties for application in radiation detection.

Enhanced Red Emission of Na5Lu9F32: Eu3+ Single Crystal by Introducing of GdF3

AbstractThe bulk Na5Lu9F32 single crystals with high quality serial Eu3+/Gd3+ co‐doped were grown by an ameliorative Bridgman technique. The measurement of X‐ray diffraction (XRD) and analysis of Rietveld refinement were implemented to validate the crystal phase. The Eu3+ doped Na5Lu9F32 single crystal emits intense red emission at 611 nm excited by 394 nm light. The intensity of 1.8 mol % Gd3+ doped sample is boosted by 3.56 times compared with the un‐doped one. The doping of Gd3+ ions replace competitively Lu3+ lattice sites with Eu3+ ions. Thus, they cause the lattice distortion and reduction of symmetry, enabling Eu3+ ions to overcome their 4f forbidden transitions. The change of Eu3+ ion local environment induced by Gd3+ ion doping was explored by the Eu3+ emission spectra and the variations of ratios between red and orange emission intensities (R/O). The fluorescence lifetime indicates that the introduction of GdF3 decreases the probability of non‐radiative transitions and increases the fluorescence lifetime. These results demonstrated that the Na5Lu9F32: Eu3+ single crystal doped with an appropriate concentration of GdF3 is a type of promising red emission single crystal for related optical devices of detector and laser due to its strong red emission, high transparency and high physico‐chemical stability.

The effect of SiC on the growth habit of Fe-Ni-C system Ib gem grade diamond crystals

This article investigates the influence of different silicon carbide contents on the morphology and quality of diamond single crystals synthesized in the Fe-Ni-C-Si system under high temperature and pressure environments. It was found that silicon successfully entered the diamond lattice through bonding. As the doping concentration increases, the growth rate of diamond crystals decreases and defects appear on the crystal surface. The increase in internal stress in the lattice reduces the quality of diamond, as evidenced by the shift in Raman peak and half peak width of the diamond. Moreover, the infrared characterization results showed that the nitrogen element in the crystal exists as a single atom (C-center) in the diamond crystal, and the nitrogen content decreases with the increase of SiC content. This work provides insights for understanding the growth mechanism of natural diamonds and enriching the application of silicon doped diamond single crystals.

Luminescent characteristics at ∼2.9 μm in Lu3+ modified Dy3+/Tm3+ co-doped LiYF4 single crystal

The single crystals specimens comprising 0.3 mol% Dy3+, 0.5 mol% Tm3+ and γ mol% Lu3+ doped LiYF4 (γ = 0, 0.3, 0.5, and 1.5) were meticulously synthesized using the Bridgman method, with the specific aim of catering to applications in the ∼2.9 μm laser domain. The microstructure of the obtained single crystal was investigated by conducting X-ray diffraction (XRD) measurements. The Judd-Ofelt (J-O) intensity parameters of the Dy3+ ion and the impacts of Lu3+ doping on fluorescence characteristics of the 6H13/2 (Dy3+) level were studied. The Dy3+/Tm3+ doped LiYF4 single crystal exhibits ∼52 % enhancement in emission intensity at ∼2.9 μm (Dy3+: 6H13/2→6H15/2) through a favorable introduction of Lu3+ ions into the single crystal at 808 nm LD excitation. The Tm3+/Dy3+/Lu3+ triply doped single crystal exhibited a maximum emission cross section of 2.480 × 10−20 cm2 at 2904 nm. The fluorescent lifetimes of the Dy3+: 6H13/2 level in the single crystals were determined to be located in the range of 2.78 ms–3.33 ms. The microscopic mechanism of energy transfer (ET) between Tm3+ and Dy3+ ions were investigated and the ET coefficients from 3H4 level of Tm3+ ion to 6F5/2 of Dy3+ ion (ET1) and 3F4 of Tm3+ to 6H11/2 of Dy3+ (ET2) in the triply doped single crystal were calculated, yielding values of 3.422 × 10−39 cm6/s and 5.768 × 10−39 cm6/s, separately. The results clearly demonstrated that the mid-infrared luminescence at ∼2.9 μm from Dy3+ ions can be significantly enhanced by the strategic incorporation of appropriate Lu3+ ions into Tm3+/Dy3+: LiYF4 single crystal.

Broadened and enhanced ∼ 2.9 μm mid-infrared emission in Dy3+/Er3+: Na5Y9F32 single crystals by Gd3+ co-doping

A series of Er3+, Dy3+ and Gd3+ doped Na5Y9F32 single crystals for laser output at ∼ 2.9 μm have been fabricated via a reformative Bridgman technique. The impacts of optically active ions of Dy3+ and Er3+ and non-optically active ion of Gd3+ on the emission spectra at ∼ 2.9 μm were investigated. The patterns of X-ray diffraction (XRD) of the obtained crystals indicated that the doping level of rare earth (RE) ions had inconspicuous effects on the lattice structure of Na5Y9F32. The emission spectra at ∼ 2.9 μm of the as-grown single crystals as change of various Er3+/Dy3+/Gd3+ contents were measured systematically excited by 974 nm light. A strong and wide emission band at ∼ 2.9 μm could be obtained in Er3+/Dy3+ co-doped crystal by utilizing Er3+ as sensitizer for Dy3+ ions. Meanwhile, the introduction of Gd3+ ions into Er3+/Dy3+ doped Na5Y9F32 single crystal could further widen the emission band at ∼ 2.9 μm due to the lattice distortion and variation of the crystal fields around Er3+ and Dy3+. Furthermore, the effective ∼ 2.9 μm emission bandwidth (Δλeff) of the Er3+/ Dy3+/ Gd3+ triply incorporated crystal was approximately 255.65 nm, which was nearly 3.4 times that of the 0.5 mol% Er ion singly doped sample (74.86 nm) and 1.4 times that of the 0.5 mol% Er/0.3 mol% Dy ions doubly incorporated sample (182.25 nm). The results unveiled that the introduction of Gd3+ was conducive to the generation of level population inversion of 6H13/2 and 6H15/2 of Dy3+ ions to help the output of ∼ 2.9 μm laser.

Growth and efficient laser emission of Er3+ doped LGGG single crystal at 2.8 μm

A novel kind of high-quality Er3+:LGGG crystal has been grown using the Czochralski method and exhibited excellent lasing performance for the first time at around 2818 nm in the mid-infrared spectral region. The J-O intensity parameters, spontaneous emission probability, branching ratio, and exited state lifetimes parameters have been calculated for the first time using the J-O theory, providing theoretical references for future analysis of the absorption and emission characteristics of Er3+:LGGG crystals. The fluorescence lifetimes of the upper (4I11/2) and lower (4I13/2) laser levels are 1.42 and 5.18 ms, respectively. Under 976 nm laser pumping, a continuous-wave laser output of 374 mW with excellent beam quality factors Mx2/My2 of 1.374/1.228 has been achieved by using the Er3+:LGGG crystal. These results indicate that Er3+:LGGG crystals are promising materials for generating 2.8 μm mid-infrared lasers.

Study on the characteristics of Si-doped diamond synthesized by different iron-based catalyst systems under high temperature and pressure

This article investigates the effects of different iron based catalysts on the morphology and quality characteristics of diamond single crystals synthesized in high-temperature and high-pressure environments. The results indicated that incorporating silicon impurities led to defects in diamond crystals, increased internal stress in the lattice, and decreased crystal quality. In addition, there are also differences in the synthesis of silicon doped diamonds under different iron based catalyst systems. This manuscript uses optical microscopy, scanning electron microscopy and Raman spectroscopy to characterize diamond crystals, exploring the influence of catalyst differences on the structure of silicon-doped diamonds. At the same time, simulation analysis was conducted on the convective field of the catalyst in the diamond synthesis chamber, and the convective field characteristics of silicon doped diamond growth under different iron based catalysts were established. The simulation results are consistent with the synthesis experimental work. This work provides a new approach to improve the quality of silicon doped diamond single crystals.

Ultra-high Curie temperature transparent piezoelectric Bi doped Ca2Nb2O7 single crystals

Ca2Nb2O7 is a promising material for high-temperature piezoelectric applications due to its ultra-high Curie temperature, which makes it a suitable candidate for use in harsh environments. However, their piezoelectric performance needs improvement. Here, through chemical engineering methods, we have successfully grown Bi3+ doped Ca2Nb2O7 single crystals using the optical floating zone technique. The Ca1.94Bi0.06Nb2O7 single crystals achieved better high-temperature stability, transparency and a higher piezoelectric constant of 12.8 pC/N at 298 K and 20.0 pC/N at 660 K. In addition to the dopant effects, mechanisms for enhancing the piezoelectric properties of perovskite-like layer structure (PLS) materials have been identified, highlighting the significant contribution of the NbO6 octahedron and interlayer ions. These findings offers valuable insights into improving the performance of PLS materials, which is crucial for promoting their practical applications as high-temperature lead-free piezoelectric materials.

The effect of Pr3+ concentration on the microstructure, luminescence and scintillation properties of Pr:LuAG single crystals

High-quality lutetium aluminum garnet doped with various Pr3+ concentrations ((Lu1-xPrx)3Al5O12, abbreviated to Pr:LuAG) single crystals were grown by the optical floating zone method. The concentration of Pr3+ dependence on microstructure, luminescence and scintillation properties were systematically studied. Based on the results of Rietveld refinement, the doping of Pr3+ leads to lattice distortion and lowers its symmetry. The symmetry of the LuO8 dodecahedron center is lowest at 0.010, as confirmed by the Raman spectra. When excited at 450 nm and X-rays, the primary emission peak at 614 and 300 nm, respectively, induced by Pr3+ 4f2-4f2 and 4f5d-4f2 transitions. The optimal doping concentration is 0.010. The electric dipole-electric dipole interaction between adjacent Pr3+ was responsible for the concentration quenching in the Pr:LuAG single crystals. (Lu0.990Pr0.010)3Al5O12 shows the shortest average scintillation decay time (22.55 ns) and highest light yield (23,842 ± 2300 ph./MeV) under 662 KeV 137Cs gamma-ray irradiation. In terms of overall luminescence and scintillation performance, 0.010 doping was the best for Pr3+ doped LuAG single crystals.

Spectroscopic investigations of Tm3+ doped CdF2 single crystals and infrared laser potentialities

By use of standard Bridgman technique, CdF2 single crystals doped with Tm3+ have been obtained with good optical quality. XRD analysis has been performed confirming the cubic structure. An ordered sequence of spectroscopic measurements (including absorption, excitation, emission and fluorescence dynamics) was carried out at room temperature. By exploiting both UV–Visible and near-infrared absorption spectra, the JO phenomenological parameters are determined by taking into account the complete refractive index dispersion, which allowed us to compute the probabilities of all transitions. Under 355 nm wavelength excitation, the Stokes emission spectrum exhibits mainly an intense blue emission line around 450 nm which is associated to 1D2→3F4 excited state transition. Whereas, the anti-Stokes blue emission around 480 nm associated to 1G4→3H6 transition is obtained under infrared excitation according to a two photon absorption mechanism. For both blue emissions, the CIE chromaticity coordinates of CdF2:Tm3+ are located in the blue region.As trivalent Tm3+ ions are known for their emissions in the near- and mid-infrared spectral ranges suitable for efficient laser operation, we have systematically studied the fluorescence behavior of the eye safe emission (pointed at ∼1.8 μm) and associated to the 3F4 → 3H6 transition. Such transition exhibit a relatively high emission cross-section (σem = 0.22 × 10−20 cm2) and a positive gain cross-section at low pumping threshold with a metastable fluorescence lifetime decay.

Investigation of structural, mechanical, dielectric, and thermal behaviour of pure and L-H doped LSMH single crystals

Lithium Sulphate Monohydrate (LSMH) and L-histidine amino acid doped Lithium Sulphate Monohydrate single crystals in a conjugate solution were grown using a slow evaporation process. The mechanical properties, thermal stability, and dielectric properties have all been confirmed by using various characterization techniques. Powder X-Ray diffraction studies were used to examine the space group and its lattice parameters, and the results showed that both crystals were arranged in a monoclinic system that was non-Centro symmetric and had the space group P21. Functional groups that were present in the grown samples were explained in great detail by Fourier Transform Infrared Spectroscopy. EDAX analysis was used to identify the measurements of the various elements that were present in the crystal sample of Lithium Sulphate Monohydrate doped with L-histidine amino acid. A Vickers micro hardness analyzer was used to determine the crystals' hardness characteristics. In-depth explanations were provided for the thermal stability of the samples, which was determined by TG/DTA analysis. The electrical behaviour of the pure LSMH and L-Histidine-doped LSMH crystal was observed using the LCRZ metre.

Local structure investigation of Cr3+ doped KTP single crystals

Using superposition model (SPM), the crystal field (CF) parameters and zero field splitting (ZFS) parameters of Cr3+ doped KTP single crystals are determined The possible sites for Cr3+ ions in KTP with distortion are taken up for calculation. Considering local distortion the theoretical ZFS parameters are in good agreement with the experimental values. The optical energy values for Cr3+ in KTP are calculated with the help of CF parameters and CFA program. The results show that Cr3+ ions substitute at Ti4+ (2) sites in KTP single crystals.

Mn2+ doped LiBaF3 fluoride perovskite single crystal with broadband infrared luminescence pumped by blue LED

In this study, Mn2+ ions doped lithium barium fluoride single crystals (LiBaF3: Mn2+) with perovskite structure were successfully prepared by a reformative Bridgman technique. A near-infrared (NIR) emitting broadband of the single crystal with a peak wavelength of 767 nm and a full width half maxima (FWHM) of 77 nm is owing to the 4T1g(4G)→6A1g(6S) transition of the Mn2+ ions in strong crystal field. Mn2+ ions replace the lattices of Li+ ions from the results of Rietveld structure refinements of the crystals performed by General Structure Analysis System (GSAS) program. A high internal quantum efficiency (41.4%) can be obtained in the synthesized single crystal upon excitation of 494 nm, and the emission intensity of this single crystal at 473 K remains at 42.9% of that at 298 K. Therefore, the LiBaF3: Mn2+ single crystal is a promising candidate for NIR solid-state light-emitting material due to its effective broadband NIR emission. This work offers a novel route to rational design of efficient broadband NIR luminescence and provides a new insight into Mn2+ luminescence and its applications.

Evidence of Yb3+ band broadening and continuous wave laser operation in bismuth modified KY1-x-yBixYby(WO4)2 mixed single crystals

To increase the Yb3+ optical bandwidths in highly anisotropic β:KY(WO4)2 (KYW) type laser single crystals, the simultaneous contributions of the Bi3+ 6 s2 lone electron pair and Y3+/Bi3+ ionic radii mismatch is proposed. The top seeded solution growth method with K2W2O7 as solvent was used to grow Yb doped single crystals of the KY(WO4)2/KBi(WO4)2 (KYBiW) solid solution. Crystals obtained across the used KY1xBixW solid solution range show always the low temperature β phase, with the monoclinic C2/c crystalline structure, but important differences between the Y/Bi composition of the starting solute and that of the crystal grown are found. The incorporation of Y and Yb into the crystal is preferential, resulting in a low Bi segregation coefficient, SBi= 13%, on the KYW side but near SBi= 90% in the KBiW side (Yb is still strongly incorporated filling the remaining 10%). The saturation temperature of the melt decreases as the Bi concentration in the precursor KY1-x-yBixYby(WO4)2/K2W2O7 mixture increases. Evidence of optical absorption and photoluminescence broadening of the Yb3+ bands with Bi3+ incorporation is derived from 6 K and 300 K measurements. Laser operation of KY1-x-yBixYby(WO4)2 crystals is shown to be comparable to that of KY1−yYby(WO4)2 ones. Up to ≈ 0.5 W of output power is obtained pumping in continuous wave regime with a Ti sapphire laser with slope efficiency η ≈ 65% and pump threshold< 200 mW, which is within the usual performance of KYW:Yb crystals, but the spectral distribution of the laser output in KYBiW:Yb crystals is larger than that for KYW:Yb. This spectral broadening may help in the reduction of ultrashort (fs) laser pulse duration generated by modelocking.