Low-energy antimony implantation in silicon

Abstract

Antimony is known to be a donor in silicon, Low-energy implantations of Sb in Si produce very shallow profiles which have many device applications. Gibbons et al. ¹ calulated the projected ranges of Sb ion-implanted in Si, using the LSS (Lindhard, Scharff, and Schiott) method. Oetzmann et al. ² measured projected ranges and range straggling for several heavy ions in Si, Al, and Ge, using high-resolution backscattering; in the energy region of interest to us, e = 10^?2 to 10^?1, their results were about 30% higher than those reported by Gibbons et al. In the study reported here, we implanted 5 × 10¹⁴ Sb/cm² in Si at 5–60 keV, measured the resulting depth distribution by secondary ion mass spectrometry, and checked the measurements by backscattering. Our results showed the experimental projected ranges to be about halfway between those reported in the earlier studies. The discrepancies between theoretical calculations and experimental results are due not to the electronic stopping cross section, which is negligible in the range of interest here, but to the nuclear stopping power. Using a modified nuclear scattering potential given by Wilson et al.,³ we calculated the projected range distribution according to the method described by Winterbon.⁴ Our results are in very good agreement with the experimental measurements.     

Mechanoluminescence by impulsive deformation of γ-irradiated Er-doped CaF2 crystals

An impulsive technique has been used for mechanoluminescence (ML) measurements in γ-irradiated Er doped CaF₂ crystals. When the ML is excited impulsively by the impact of moving piston on to γ-irradiated CaF₂:Er crystals, two peaks are observed in ML intensity with time and it is seen that the peak intensities of first and second peaks (I_m1 and I_m2) increase with increasing impact velocity. However the time corresponding to first and second peaks (t_m1 and t_m2) shifts towards shorter time values with increasing impact velocity. It is also seen that the total ML intensity I_Total initially increases with the impact velocity and then it attains a saturation value for higher values of the impact velocity. We have presented a theoretical explanation for the observed results.     

Fluorescence and persistent spectral hole burning of Eu in Ge-Ga-S-KBr glasses

Fluorescence and efficient persistent spectral hole burning of Eu³⁺ at 77 K were observed in chalcohalide glasses. The depth of the hole was approximately 30% after a burning process of 1 min with 50 mW power, and it was completely erased with Ar⁺ laser irradiation. The hole survived room temperature heat treatment and showed good thermal stability. The hole-burning mechanism was most probably the photo-reduction of Eu³⁺→Eu²⁺. Fluorescence from Eu³⁺ decreased with increasing temperature and disappeared at the temperature above ∼130 K.     

Chemical and catalytic effects of ion implantation

Energetic particles are used for inducing chemical reactions as well as for modifying the properties of materials with regard to their bulk and surface chemical behavior. The effects are partly caused by radiation damage or phase intermixing, partly by the chemical properties of the individual bombarding particles. In this contribution a survey of relevant applications of these techniques is presented:

1) Chemical reactions of implanted and recoil atoms and their use for syntheses, doping and labeling of compounds.

2) The formation of thin films by decomposing chemical compounds with ion beams.

3) Catalytic effects on substrates treated by sputtering or ion implantation. Recent results with nonmetallic substrates are reviewed. Mainly hydrogenation reactions at a solid/gas interface or redox reactions at an electrified solid/liquid interface are mentioned.

The present status and future prospects of these kinds of investigations will be discussed.     

Upconversion and color tunability in Tm/Ho/Yb doped low phonon energy bismuth tellurite glasses

Low phonon energy Tm³⁺/Ho³⁺/Yb³⁺ triply doped bismuth tellurite glasses exhibiting multicolor upconversion fluorescences have been fabricated and characterized. The multicolor fluorescence composed of three primary colors green, red and blue upconversion emissions from Ho³⁺ and Tm³⁺ has been investigated. By adjusting the excitation power, the fluorescence colors can be tuned from multicolor to white color, and the dependence of color tunability on pump power has been presented in the CIE 1931 chromaticity diagram. With the increase in pumping power, the color coordinates move along the down-left direction and hit the equal energy point. The upconversion and color tunability via changing the pump power of infrared excitation in Tm³⁺/Ho³⁺/Yb³⁺ triply doped bismuth tellurite glasses will lead to new breakthrough in the field of three-dimensional solid-state displays and white-light emitting devices.     

Microstructures and tribological properties of plasma sprayed WC-Co-Cu-BaF2/CaF2 self-lubricating wear resistant coatings

A promising WC-Co-Cu-BaF₂/CaF₂ self-lubricating wear resistant coating was deposited via atmospheric plasma spraying (APS) process by using homemade feedstock powders composed of WC-Co, Cu and BaF₂/CaF₂ eutectic. The as-prepared cermet coatings had better frictional behavior comparing with the WC-Co coating. Moreover, the often-occurred decarburization of WC in APS process was noticeably improved due to the binding of copper and BaF₂/CaF₂ phase, which not only offered effective solid lubrication, but also acted as bind phases to mend the microstructure and protected WC from decomposition. The optimized specimen contained 10 wt.% Cu and 10 wt.% BaF₂/CaF₂ in a WC-Co matrix, which had excellent frictional and wear performance. The wear mechanism of the self-lubricating wear resistant coating was discussed with the microstructures, compositions and mechanical properties of the composite materials in detail.     

The effects of added foreign ions in Gd2O2S : Tb; crystal field calculations, lifetimes, photo-luminescence and absorption spectra

A spectroscopic study is carried out in which the effects of added Ca²⁺ and Ru⁴⁺ transition metal ions on some characteristics of the emission of Gd₂O₂S : Tb³⁺ phosphors (energy levels, intensities, lifetimes) are examined and compared. In order to distinguish the Tb³⁺ emissions from impurity ones, the electronic energy levels of trivalent terbium are determined and the energy level scheme is completed by a crystal field analysis. The optical spectra reveal no terbium doped impurity phase; however, other rare earth ions present as impurities in the starting materials are detected. They are identified, and the influence of the added Ca²⁺ and Ru⁴⁺ on their emission lines is also examined.     

Yb3+敏化的Er3+/Ho3+共掺碲酸盐玻璃的上转换发光研究

用高温熔融法制备了系列Er³⁺/Yb³⁺共掺，Ho³⁺/Yb³⁺共掺，和Er³⁺/Yb³⁺/Ho³⁺三掺碲酸盐玻璃，在975nm激光抽运下三种掺杂玻璃中都出现了较强的绿光和红光上转换.研究了Yb³⁺离子对Er³⁺和Ho³⁺离子上转换发光强度的影响以及Yb³⁺→Er关键词： 3+/Yb³⁺/Ho³⁺共掺')" href="#">Er³⁺/Yb³⁺/Ho³⁺共掺 碲酸盐玻璃 光谱性质 上转换     

Charge states of the activator and size effects in BaF2: Eu nanophosphors

ABSTRACT

According to the spectra of stationary X-ray excited luminescence (XEL) of BaF₂: Eu nanophosphors at 80 and 294 K, it was revealed that the thermal annealing of fine-grained nanoparticles (d?=?35?nm) in the range of 400–1000°C, which is accompanied by an increase of their sizes in the range of 58–120?nm, does not result in effective changes of the charge state of Eu^{3 +} → Eu^{2 +} activator, in contrast to CaF₂: Eu nanoparticles. The maximum light output of X-ray excited luminescence of BaF₂: Eu nanophosphors in the 590?nm emission band of Eu³⁺ ion was observed at an annealing temperature of 600°C with the average size of nanoparticles 67?nm. The subsequent growth of annealing temperatures, especially in the range of 800–1000°C, causes decrease in the light output of X-ray excited luminescence due to the increase of defect concentration in the lattice as a result of sharp increase of nanoparticle sizes and their agglomeration. In BaF₂: Eu nanoparticles of 58?nm size, according to the thermostimulated luminescence (TSL) spectrum, transformation of Eu³⁺ → Eu²⁺ under the influence of long-time X-ray irradiation was revealed for the peak of 151?K. Thus, X-ray excited luminescence spectra of BaF₂: Eu nanophosphors are formed predominantly due to the emission of Eu³⁺ ions, while emission of Eu²⁺ ions is observed in the TSL spectra.     

Up-conversion white light of Tm/Er/Yb tri-doped CaF2 phosphors

Tm³⁺/Er³⁺/Yb³⁺ tri-doped CaF₂ phosphors were synthesized using a hydrothermal method. The phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and up-conversion (UC) emission spectra. After annealing, the phosphors emitted white light under a 980 nm continuous wave diode laser (CW LD 2 W) excitation. As the excitation power density changed in the range of 20-260 W/cm², the chromaticity coordinates of the UC light of the phosphor Ca_0.885Tm_0.005Er_0.01Yb_0.1F₂ fell well in the white region of the 1931 CIE diagram. For the proportion of red, green and blue (RGB) in white light is strict, key factors for achieving UC white light, such as host materials, rare earth ions doping concentrations, annealing temperatures, as well as the excitation power densities, were investigated and discussed.     

Violet and visible up-conversion emission in Yb-Ho co-doped germanium-borate glasses

The up-conversion emission properties of Yb³⁺-Ho³⁺ co-doped germanium-borate glasses have been investigated with 980 nm excitation. The violet, blue, green and red emission bands at about 350, 485, 544 and 653 nm can be identified, respectively. Experimental results indicated that the relative intensity ratios of the peaks I_Red/I_Green increased with increasing B₂O₃ concentration, which led to changing color of up-conversion emission from green at x=0 to yellow at x=40, to red at x=60. The violet emission at 350 nm was first reported in germanium-borate glass host and up-conversion mechanisms of the emissions were discussed. The Yb³⁺-Ho³⁺ co-doped germanium-borate glasses could be an alternative for the generation of violet and primary colors for application in solid-state displays.     

The effect of flux materials on the physical and optical properties of Eu-activated yttrium oxide phosphors

A flux fusion method was used to obtain the various sizes of Eu³⁺-activated Y₂O₃ red phosphors. The flux material was selected as an independent variable to control the physical properties of phosphor particles and their effects on the morphology and size distribution of phosphors were examined by scanning electron microscopy. The concentration of the flux materials and synthetic temperature were optimized for maximal photoluminescence intensity. Fluoride-based flux materials were found to work for the crystal formation of Eu³⁺-activated Y₂O₃. In particular, when a BaF₂ flux was used during the reaction at 1450 °C for 3 h, the photoluminescence (PL) intensity of Eu³⁺-activated Y₂O₃ was 25% higher than that without a flux and spherical phosphors had a mean particle size of 4-5 μm. The morphology and size distribution of the synthesized Eu³⁺-activated Y₂O₃ phosphor were predominantly dependent upon the type and concentration of flux material and synthetic temperature.     

Thermoluminescence and opitical absorption of BaF2 crystals

Abstract

Nominally pure and Dy-doped BaF₂ crystals were investigated concerning their optical absorption (OA) and thermoluminescence (TL) properties. Peaks at 120—150 and 200°C were observed for a heating rate of 1.7°C/s. The TL response for γ-rays and the TL emission spectra were obtained for these peaks. Except for the purest crystal, all BaF₂ crystals produced OA bands before irradiation typical of Ce³⁺ ions. After irradiation, Dy doped crystals showed bands due to Dy²⁺ ions. A nominally pure sample gave bands related to Ce²⁺ ions and photochromic centers of Ce³⁺ ions. and photochromic centres of Ce³⁺ ions. The correlation between some OA bands and TL peaks is discussed.     

Application of solid state track recorders for neutron spectra measurements in a reactor irradiation facility

Abstract

In connection with the IAEA-neutron seed irradiation Programme, a standard neutron irradiation facility has been constructed. The application of solid state track recorders for fast neutron spectra measurements inside this facility is discussed. Fissionable targets of ²³⁵U, ²³⁹Pu, ²³⁷Np, ²³⁸W and ²³²Th will be used, an approximative solution for the incident neutron spectrum will be obtained by a five-group method.     

Manifestations of hyperfine interaction in optical spectra of KY3F10:Ho

We report on the first observation of the well-resolved hyperfine structure in optical spectra of the KY₃F₁₀:Ho³⁺ single crystals. Some interesting peculiarities of this structure and the origin of the observed forbidden transitions are discussed.     

Theory studies of the local lattice distortions and the EPR parameters for Cu2+, Mn2+ and Fe3+ centres in ZnWO4

The local lattice distortions and the electron paramagnetic resonance (EPR) parameters (g factors, hyperfine structure constants and zero-field splittings) for Cu²⁺, Mn²⁺ and Fe³⁺ in ZnWO₄ are theoretically studied based on the perturbation calculations for rhombically elongated octahedral 3d⁹ and 3d⁵ complexes. The impurity centres on Zn²⁺ sites undergo the local elongations of 0.01, 0.002 and 0.013 Å along the C₂ axis and the planar bond angle variations of 8.1°, 8.0° and 8.6° for Cu²⁺, Mn²⁺ and Fe³⁺, respectively, due to the Jahn–Teller effect and size and charge mismatch. In contrast to the host Zn²⁺ site with obvious axial elongation (～0.31 Å) and perpendicular (angular) rhombic distortion, all the impurity centres demonstrate more regular octahedral due to the above local lattice distortions. The copper centre exhibits significant Jahn–Teller reductions for the spin-orbit coupling and orbital angular momentum interactions, characterised by the Jahn–Teller reduction factor J (≈0.29 ? 1). The calculated EPR parameters agree well with the experimental results. The local structures of the impurity centres are analysed in view of the corresponding lattice distortions.     

Eu2+, Cr3+共掺杂的MAl12O19 (M=Ca, Sr, Ba) 的发光性质及能量传递

三基色荧光粉中, 红色荧光粉性能较差, 为获得性能优良的红色荧光粉, 本文采用高温固相法合成了Eu²⁺, Cr³⁺单掺杂及共掺杂的碱土金属多铝酸盐MAl₁₂O₁₉ (M =Ca, Sr, Ba) 发光体. 实验表明, 在以上三种基质中均存在Eu²⁺→Cr³⁺的能量传递, 利用能量传递可以有效将Eu²⁺的蓝光或绿光转换为红光. 三种碱土金属多铝酸盐基质的晶体结构相似,但Eu²⁺, Cr³⁺发光受晶体场影响,导致在不同的基质中Eu²⁺, Cr³⁺间能量传递效率不同.通过光谱分析及能量传递效率计算发现, 相同掺杂浓度下,CaAl₁₂O₁₉中Eu²⁺→Cr³⁺的能量传递效率最高,SrAl₁₂O₁₉次之, BaAl₁₂O₁₉最低.红光转换率在CaAl₁₂O₁₉中最高.     

Optical characterization of Mn, Ni and Co ions doped zinc lead borate glasses

This paper reports on the development and optical characterization of heavy metal oxide (HMO)-based transparent glasses in the chemical composition of 15PbO-40B₂O₃-(45−x) ZnO−x TM²⁺ (=Mn²⁺ or Ni²⁺ or Co²⁺) (where x=0.2, 0.5 mol%). For these glasses both absorption and emission spectra have been measured, in order to understand their optical performances. The XRD profiles have confirmed their glassy nature and the FTIR spectral features have been analyzed. From the emission spectra, a bright green emission (538 nm) from Mn²⁺-glasses, an intense red emission (670 nm) from Ni²⁺ and from Co²⁺ (625 nm) glasses have been noticed very clearly. Based on the UV-absorption spectra of these materials, both direct and indirect bond gaps have been computed. Apart from the spectral analysis, different physical properties of these glasses have also been carried out. Due to the presence of both PbO and ZnO, these glasses are found to be good moisture-resistant optical systems. Both optical and physical properties have been found to be more encouraging towards their use as novel luminescent optical materials.     

镱、钠共掺的氟化钙晶体在1050nm的可饱和吸收作用

通过在稳定连续波运转的Yb:YAG 激光器中插入不同掺杂浓度的新型钠、镱共掺的氟化钙晶体的对比性实验,证明了镱、钠共掺的氟化钙晶体在1050nm具有明显的可饱和吸收作用,从而解释了该晶体作为增益介质在该波段总是趋于自调Q运转的原因.Yb³⁺离子是该晶体可饱和吸收作用的主要因素,但是共掺入适当的Na离子可以明显改善晶体的调Q效果.优化共掺镱、钠离子的浓度和比例后的氟化钙晶体能够作为1050nm波段激光器的被动Q开关. 关键词： 镱、钠共掺氟化钙 可饱和吸收体 调Q     

Luminescence of Ce and Pr doped Sr2Mg(BO3)2 under VUV-UV and X-ray excitation

This report presents the luminescence properties of Ce³⁺ and Pr³⁺ activated Sr₂Mg(BO₃)₂ under VUV-UV and X-ray excitation. The five excitation bands of crystal field split 5d states are observed at about 46 729, 44 643, 41 667, 38 314 and 29 762 cm⁻¹ (i.e. 214, 224, 240, 261 and 336 nm) for Ce³⁺ in the host lattice. The doublet Ce³⁺ 5d→4f emission bands were found at about 25 840 and 24 096 cm⁻¹ (387 and 415 nm). The influence of doping concentration and temperature on the emission characteristics and the decay time of Ce³⁺ in Sr₂Mg(BO₃)₂ were investigated. For Pr³⁺ doped samples, the lowest 5d excitation band was observed at about 42017 cm⁻¹ (238 nm), a dominant band at around 35714 cm⁻¹ (280 nm) and two shoulder bands were seen in the emission spectra. The excitation and emission spectra of Ce³⁺ and Pr³⁺ were compared and discussed. The X-ray excited luminescence studies show that the light yields are ∼3200±230 and ∼1400±100 photons/MeV of absorbed X-ray energy for the samples Sr_1.86Ce_0.07Na_0.07Mg(BO₃)₂ and Sr_1.82Pr_0.09Na_0.09Mg(BO₃)₂ at RT, respectively.