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1.
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. 相似文献
2.
The secondary radiation after resonant excitation of F center and its linear polarization P correlated to the polarization of resonant light have been measured for five alkali halides at low temperatures. In KC1, the spectrum of P over the whole Stokes region is divided into three successive regions, the depolarization range at the one-phonon Raman scattering, the near plateau range, and the depolarization range down to vanishing. The former two have common relevance to resonant energy and symmetries of coupled phonons. These relevances are interpreted adopting a configuration coordinate model for 2s- and 2p-like excited states. 相似文献
3.
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. 相似文献
4.
The EPR g factors g// and g⊥ for Ti3+ ions at the trigonal octahedral Li+ sites of LiNbO3 and LiTaO3 crystals are calculated from the third-order perturbation formulas of g factors for 3d1 ion in trigonal symmetry. In the calculations, the crystal-field parameters are obtained from the structural data by using the superposition model. The calculated values are in reasonable agreement with the observed values. The results are discussed. 相似文献
5.
W. Köhler 《辐射效应与固体损伤》2013,168(2):231-233
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. 相似文献
6.
With the help of the Dexter's theory, the energy transfer mechanism from Pr3+1S0 to Cr3+ is investigated theoretically in SrAl12O19:Pr3+, Cr3+ quantum cutting phosphors. The electron spin resonance (ESR) spectra of Pr3+ and Cr3+-doped SrAl12O19 with magnetoplumbite structure have been studied. The Cr3+ ion is found to enter the Al4(4f) site, which is very close to the Sr(2d) site replaced by the Pr3+ ions in the host. The theoretical results indicate that the efficient Pr3+1S0→Cr3+ energy transfer can only take place in the intermediate mirror planes, in which for the nearest and next-nearest Pr3+-Cr3+ pairs, both dipole-dipole and dipole-quadrupole interactions can play their parts in the transfer. Finally, an overview is given about the research on the energy transfer from Pr3+1S0 to codopants in their co-doped materials. 相似文献
7.
8.
Xiaoqing Zeng Seoung-Jae Im Sang-Hun Jang Young-Mo Kim Hyoung-Bin Park Seung-Hyun Son Hidekazu Hatanaka Gi-Young Kim Seul-Gi Kim 《Journal of luminescence》2006,121(1):1-6
Bi3+- and RE3+-co-doped (Y,Gd)BO3 phosphors were prepared and their luminescent properties under vacuum ultraviolet (VUV)/UV excitation were investigated. Strong red emission for (Y,Gd)BO3:Bi3+,Eu3+ and strong green emission for (Y,Gd)BO3:Bi3+,Tb3+ are observed under VUV excitation from 147 to 200 nm with a much broader excitation region than that of single Eu3+-doped or Tb3+-doped (Y,Gd)BO3 phosphor. Strong emissions are also observed under UV excitation around 265 nm where as nearly no luminescence is observed for single Eu3+-doped or Tb3+-doped (Y,Gd)BO3. The luminescence enhancement of Bi3+- and RE3+-co-doped (Y,Gd)BO3 phosphors is due to energy transfer from Bi3+ ion to Eu3+ or Tb3+ ion not only in the VUV region but also in the UV region. Besides, host sensitization competition between Bi3+ and Eu3+ or Tb3+ is also observed. The investigated phosphors may be preferable for devices with a VUV light 147-200 nm as an excitation source such as PDP or mercury-free fluorescent lamp. 相似文献
9.
10.
This work investigates the origin of novel visible photoluminescence (PL) bands observed in the spinel MgAl2O4:Co2+. Besides the well-known fourfold-coordinated Co2+(Td) PL at 670 nm [N.V. Kuleshov, V.P. Mikhailov, V.G. Scherbitsky, P.V. Prokoshin and K.V. Yumashev, J. Lumin. 55 (1993) 265.], a rich structured PL band at 686 nm was also observed that we associate with uncontrolled impurities of sixfold coordinated Cr3+(Oh) by time-resolved spectroscopy and lifetime measurements and their variation with temperature. We also show that the lifetime of the Co2+(Td) emission at 670 nm varies from τ=6.7 μs to 780 ns on passing from T=10 to 290 K. This unexpected behaviour for Td systems is related to the excited-state crossover (4T1↔2E), making the emission band to transform from a narrow-like emission from 2E at low temperature to a broad structureless band from 4T1 at room temperature. 相似文献
11.
Near-infrared (NIR) persistent luminescent β-Ga2O3:Cr3+ nanowire assemblies were synthesized by a hydrothermal process followed by calcination. The phosphor exhibits more than 4 h afterglow in the wavelength range of 650-850 nm after ceasing the ultraviolet light (280-360 nm) irradiation. The trap structure and persistent luminescence mechanism were revealed by thermoluminescence measurement. The β-Ga2O3:Cr3+ nanowire assemblies may find applications as identification taggants in security and optical probes in bio-imaging. 相似文献
12.
Zheng Wen-Chen 《辐射效应与固体损伤》2013,168(1-2):169-178
Abstract The tetragonal distortions of local octahedral environments of Cr3+, Fe3+ and Gd3+ ions in Rb2CdF4, Cs2CdF4, RbCdF3 and CsCdF3 crystals have been studied by analyzing their EPR spectra. From the studies, it is found that the tetragonal distortions for Cr3+ and Fe3+ impurity ions, which substitute Cd2+ and have nearly the same ionic radius, are close to each other, whereas that for Gd3+ impurity ion, having a larger ionic radius, is larger than those for Cr3+ and Fe3+ ions in the same crystal. It appears that not only the impurity-ligand distance, but also the tetragonal distortions of impurity centres in crystals are closely related to the size of impurity. 相似文献
13.
The spin Hamiltonian parameters (g factors, hyperfine structure constants and zero-field splittings D and E) and local structures for Mn2+ and Ni2+ in [Zn(en)3](NO3)2 single crystal are theoretically investigated from the perturbation calculations for trigonally distorted 3d5 and trigonally (or orthorhombically) distorted 3d8 cluster. The trigonal Mn2+ and Ni2+ centres are found to undergo the moderate angular variations Δβ of 4.5° and 5.2°, respectively, related to host Zn2+ site due to size mismatch. The orthorhombic Ni2+ centre shows the relative axial elongation ratio ρ (≈ 2.5%) and the relative perpendicular bond length variation ratio τ (≈0.2%). For Mn2+ centre, the contributions to g-shifts ΔgCT (or hyperfine structure constants ACT and zero-field splitting DCT) from charge-transfer (CT) mechanism are opposite in sign and five times (or 5% and 8%) in magnitude compared with those from crystal-field (CF) mechanism. For the trigonal Ni2+ centre, ΔgCT (or DCT) are the same (or opposite) in sign and 17% (or 2%) in magnitude related to those from CF mechanism. For the orthorhombic Ni2+ centre, ΔgCT and ECT (or DCT) are same (or opposite) in sign and 16% and 48% (or 442%) in magnitude with respect to those from the CF mechanism. The signs and magnitudes of the trigonal distortion angles δβ (≈ ?0.3 and 0.4°) related to an ideal octahedron and the local angular variations Δβ related to the host bond angle are suitably illustrated by those of the axial distortion degree (ADD) and the angular variation degree (AVD) of the systems, respectively. 相似文献
14.
The electron paramagnetic resonance g factors and the local structure for Ni3+ in LaAl0.9Ni0.1O3 (LAN), La0.75Y0.25Al0.99Ni0.01O3 (LYAN) and YAl0.9Ni0.1O3 (YAN) are theoretically studied from the perturbation formulas of the g factors for a 3d7 ion of low spin (S = 1/2) in tetragonally elongated octahedra. In these formulas, the contributions to the g factors from the tetragonal distortion, characterized by the tetragonal field parameters Ds and Dt are taken into account. According to the calculations, the ligand octahedra around Ni3+ are suggested to suffer 2% relative elongation along the [001] (or C4) axis due to the Jahn-Teller effect. 相似文献
15.
Abstract Pairs of copper samples—one for electrical resistivity, the other for Young's modulus measurements - were irradiated simultaneously at 120°K with 3 MeV electrons up to an integrated dose of 2 × 1020 el/cm2. The effect of dislocation pinning and the bulk effect of point defects on Young's modulus E could clearly be separated. The following relation between the bulk effect ΔE/E and the resistivity increase Δρ[Ωcm] was found: ΔE/E = ?25 × 104 × Δρ. Besides strong annealing in stages II and III (180–300°K) and some annealing between 300–500°K, stage V annealing (500–600°K) also was found. In stage III the resistivity annealed more than Young's modulus. whereas the converse occurred in stage V. These measurements are discussed in connection with the electron microsopical observation of point defect clusters after electron irradiation at 120°K and heating to room temperature. Probenpaare, bestehend aus einer Widerstandsprobe und einer Probe zur Messung des Elastizitätsmoduls, wurden gleichzeitig bei 120°K mit 3 MeV-Elektronen bis zu einer Dosis von 2 × 1020 el/cm2 bestrahlt. Die direkte Reein-flussung des E-Moduls durch die im Gitter verteilten Punktdefekte (Volumeneffekt) konnte getrennt von der Beeinflussung durch Versetzungsverankerung gemessen werden. Es ergab sich dabei folgende Beziehung zwischen relativer Modulanderung ΔE/E und strahlungsinduziertem Widerstand Δρ[Ωcm]: ΔE/E = ?25 × 104 × Δρ. Neben starker Erholung in den Stufen II und III (180–300 °K) und schwacher Erholung zwischen 300–500°K wurde auβerdem Stufe V (500–600°K) beobachtet. In Stufe III erholte sich der Widerstand starker als der E-Modul, wahrend in Stufe V das umgekehrte der Fall war. Die Messungen werden diskutiert in Zusammenhang mit der elektronenmikroskopischen Beobachtung von Punktdefektclustern nach Elektronenbestrahlung bei 120°K und anschlieβender Erwärmung auf Raumtemperatur. 相似文献
16.
Electron spectra of optical absorption and EPR of Cr3+ ions in a LaBeAl11O19 crystal are investigated. It is shown that the Cr3+ ions occupy, three different octahedral positions of Al3+ in the LaBeAl11O19 structure, namely, 12k, 2a, and 4f2; the ratio of their intensitites is 1∶2∶30, respectively. Parameters of the Cr3+ centers are determined and its is shown that the optical absorption spectra in the visible region are practically determined
by the Cr3+ (III) occupying the 4f2-positions.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 275–277, March–April, 1999. 相似文献
17.
Chang-Chun Ding Shao-Yi Wu Qing-Sheng Zhu Guo-Liang Li Zhi-Hong Zhang Yong-Qiang Xu 《Molecular physics》2013,111(12):1478-1484
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. 相似文献
18.
Aripin S. Mitsudo T. Shirai K. Matsuda T. Kanemaki T. Idehara T. Tatsukawa 《International Journal of Infrared and Millimeter Waves》1999,20(11):1875-1888
Fine structure constant of ruby has been measured using an ESR spectrometer with a pulse magnetic for high fields and a gyrotron as a radiation source in a millimeter to submillimeter wave range. The measurement was carried out at room temperature. The Zeeman energy in this frequency range is large enough compared with the fine structure constant. The higher order term in the effective spin Hamiltonian can explain the dependence of fine structure constant on the frequency. The observed fine structure constants depend on the field intensity. 相似文献
19.
Michèle D. FaucherO.K. Moune 《Journal of luminescence》2002,96(1):37-49
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. 相似文献
20.
Yang Zi-Yuan 《Physica B: Condensed Matter》2011,406(20):3975-3979
The local structure distortion and the spin Hamiltonian (SH) parameters, including the zero-field splitting (ZFS) parameter D and the Zeeman g-factors g‖ and g⊥, are theoretically investigated by means of complete diagonalization method (CDM) and the microscopic spin Hamiltonian theory for tetragonal charge compensation CrF5O defect center in Cr3+:KMgF3 crystals. The superposition model (SPM) calculations are carried out to provide the crystal field (CF) parameters. This investigation reveals that the replacement of O2− for F− and its induced lattice relaxation Δ1(O2−) combined with an inward relaxation of the nearest five fluorine Δ2(F−) give rise to a strong tetragonal crystal field, which in turn results in the large ZFS and large anisotropic g-factor Δg. The experimental SH parameters D and Δg can be reproduced well by assuming that O2− moves towards the central ion Cr3+ by Δ1(O2−)=0.172R0 and the five F− ions towards the central ion Cr3+ by Δ2(F−)=0.022R0. Our approach takes into account the spin-orbit (SO) interaction as well as the spin-spin (SS), spin-other-orbit (SOO), and orbit-orbit (OO) interactions omitted in previous studies. This shows that although the SO interaction is the most important one, the contributions to the SH parameters from other three magnetic interactions are appreciable and should not be omitted, especially for the ZFS parameter D. 相似文献