Radiation damage by implanted ions in GaAs and GaP

Abstract

The production of lattice disorder in GaAs and GaP by Te ions up to 40 keV has been investigated. For GaAs the build up of damage with implanted ion dose is linear until a saturation level is reached. For Gap, two linear regions are evident; a slow build up of damage to ?15 per cent of the saturation level, followed by a faster rate of increase up to the final 100 per cent level. Radiation annealing, for GaP samples, both by the heavy ion beam during implantation and by the helium beam during back-scattering measurements has been observed. The annealing temperatures required for re-ordering the lattice depend on the percentage of damage present. Samples damaged up to the saturation level require annealing at ?500°C, whilst 300°C is sufficient for samples damaged to ?50 per cent of the saturation value.     

Pr,Yb:ZBLAN上转换发光过程中的能量传递

详细地研究了Ｐｒ３＋，Ｙｂ３＋ＺＢＬＡＮ玻璃中Ｐｒ３＋和Ｙｂ３＋离子之间的能量传递过程、及能量传递对上转换发光的影响。实验结果表明，在９６０ｎｍ激光泵浦下Ｙｂ３＋通过Ｙｂ３＋—Ｐｒ３＋之间的交叉弛豫向Ｐｒ３＋传递能量。具体的能量传递形式有三种。Ｙｂ３＋作为敏化剂可提高Ｐｒ３＋的上转换发光强度。从Ｐｒ３＋向Ｙｂ３＋的反向能量传递过程也是存在的，具体的过程和Ｐｒ３＋向Ｙｂ３＋传递的相反。Ｐｒ３＋—Ｙｂ３＋的能量传递导致Ｐｒ３＋发光的淬灭，使Ｐｒ３＋上转换发光随着Ｙｂ３＋浓度增加出现饱和。和３Ｐ０能级相比较，Ｙｂ３＋对Ｐｒ３＋离子的１Ｄ２能级发光的淬灭作用更强     

The optical properties of Yb3+ ions in LiTaO3:Nd,Yb crystals

3+ ions excited by energy transfer from Nd³⁺ ions in LiTaO₃:Nd, Yb crystals are presented. The emission band of Yb³⁺ ions is broad, due to the strong phonon-coupling and to the relative large Stark-splitting of the ground ²F_7/2 multiplet. The emission cross-section was evaluated by the reciprocity method, and a value of 0.53×10^-20 cm² was obtained. The gain coefficients derived for the inversion parameters in the range 0.05 to 0.5 indicate positive gain in the 985–1070 nm range. Received: 17 March 1997/Revised version: 10 June 1997     

GdBO3：Pr3+，Yb3+中Pr3+到Yb3+的能量传递及发光性质

采用高温固相法制备了一系列单掺或双掺Pr3+和Yb3+的GdBO3材料,分别测试分析了材料的物相结构和发光性质。在446 nm蓝光( Pr3+：3 H4→3 P2)激发下,检测到Yb3+的近红外特征发射,表明样品中存在Pr3+到Yb3+的能量传递。 Pr3+的掺杂浓度一定时,样品的发光会随着Yb3+掺杂浓度的改变而发生变化。通过对比不同掺杂情况下Pr3+：3 P0能级的衰减曲线,发现随着Yb3+的掺杂浓度的增加,该能级的荧光寿命不断缩短;同时利用不同条件下的衰减特性计算得出不同 Yb3+掺杂浓度样品的能量传递效率。用 Inokuti-Hirayama模型分析表明Pr3+-Yb3+能量传递类型为偶极子-偶极子相互作用。     

Luminescence of YAG doped with Eu,Yb, and Mn ions under VUV excitation

Hydrothermal synthesis has been successfully used to obtain fine-crystalline powders of yttrium aluminum garnet (YAG) doped with manganese ions and codoped with cerium and manganese ions. Using the method of high-temperature solid-state synthesis, ceramic specimens of YAG that contain europium and ytterbium ions have been obtained. In synthesized YAG:Eu and YAG:Yb ceramics, no luminescence that can be attributed to 5d-4f transitions in Eu²⁺ or Yb²⁺ ions has been detected, even though the scheme of energy levels of these ions constructed with respect to YAG energy bands indicates that there is a potential possibility of the occurrence of 5d-4f luminescence for Eu²⁺ ions in YAG. At room temperature, the luminescence spectrum of hydrothermally synthesized YAG doped with manganese ions consists of two broad bands with maxima at ～600 and ～750 nm and does not contain any narrow bands in the red or IR range. Therefore, the spectrum contradicts to the properties of the luminescence of Mn²⁺, Mn³⁺, or Mn⁴⁺ ions in YAG described in the literature, even though the obtained hydrothermal specimens can contain noticeable concentrations only of Mn³⁺ ions.     

Luminescence of Pr3+ and Nd3+ Ions in Double Molybdates

Physics of the Solid State - The optical spectra of samples of double zirconium molybdates activated by rare-earth Pr3+ and Nd3+ ions are studied. The presence of bands corresponding to the...     

Laser annealing of GaAs dual implanted with Si and P ions

Laser annealing of SI(100) GaAs:Cr implanted either with Si⁺ ions (150 keV, 6×10¹³-1×10¹⁵cm^–2) or dual implanted with Si⁺ ions (150 keV, 6×10¹⁴–1×10¹⁵cm^–2) and P⁺ ions (160 keV, 1×10¹⁴–1×10¹⁵cm^–2) has been examined using backscatteringchannelling technique and via electrical measurement of Hall effect. It has been found that at laser energy densities 0·8 J cm^–2 a full recovery of the sample surface occurs. In dual implanted samples (1×10¹⁵ Si⁺ cm^–2+1×10¹⁵P⁺cm^–2) up to 46% of Si atoms become electrically active after the laser annealing. Resultant Hall mobility of carriers is, however,lower than that obtained after common thermal annealing.The authors are pleased to take the opportunity of thanking Professor M. Kubát for his encouragement and continuous support. Accelerator staff is gratefully acknowledged for its assistance in the course of experiments.     

Large Z1-range effect for Eu,Yb and Au ions implanted in amorphized silicon

The Z₁-range oscillation amplitude is investigated as a function of energy for Eu, Yb and Au ions implanted in amorphous Si at energies from 10 to 390 keV. The obtained experimental results are not reproduced by the recent theoretical predictions of Burenkov and collaborators, showing large discrepancies for energies lower than 50 keV.     

Luminescence of ZnO films implanted with Au+ ions and annealed in oxygen radicals

Visible and ultraviolet luminescence spectra of ZnO:Au⁺ samples with various dose of implanted gold were studied at a temperature of 77 K. Luminescence peaks of bound and free excitons, D-A pairs, and electron recombination to the gold acceptor level were detected. The optical depth (0.117 eV) of the Au_Zn impurity acceptor level was determined. Diffusive spreading of the implanted impurity profile upon annealing of the zinc oxide film was observed by SIMS.     

Field-ion microscopy of GaAs and GaP

Clean surfaces of GaAs and GaP were studied by field-ion microscope (FIM). Field-ion images with ordered surfaces were first obtained in pure hydrogen, neon-50% hydrogen and pure neon gases at 78 K, by using channeltron electron multiplier arrays (CEMA). The field-ion images of GaAs were quite similar to those of GaP with respect to the surface structure and the image contrast. They showed the anisotropies of the ion emission and the surface structure between the [111] and $\text{[}\text{1}\text{1}\text{1}\text{]}$ orientations. Ring steps expected from a spherical surface were observed on the (111) and {100} planes, but not on the $\text{[}\text{1}\text{1}\text{1}\text{]}$ and {110} planes. The regional brightness of the FIM patterns was discussed in terms of the Knor and Müller model and the atomic and electronic structures of the surface. The image field of these crystals was much lower than that of metals usually used in FIM. For example, the image field strength for the hydrogen and GaAs system was about 1.1 V/Å. The reduction of the field necessary to image was also discussed in terms of the field penetration effect.     

YAG晶体中Cr4+和Yb3+的光谱和荧光特性研究

报道了（Ｃｒ＾４＋,Ｙｂ＾３＋）：ＹＡＧ晶体的吸收光谱和荧光光谱特性。在室温下,（Ｃｒ＾４＋,Ｙｂ＾３＋）：ＹＡＧ晶体在９３７ｎｍ和９６８ｎｍ处存在两个吸收带,能与ＩｎＧａＡｓ激光二级管有效耦合：而且在１０３０ｎｍ处有一Ｃｒ＾４＋吸收峰,可以实现对Ｙｂ＾３＋的自调Ｑ激光输出。（Ｃｒ＾＋,Ｙｂ＾３＋）：ＹＡＧ 荧光光谱与Ｙｂ＾３＋：ＹＡＧ晶体一样,发光中心也是位于１０２９ｎｍ,但其强度比Ｙｂ＾３＋：     

Three-dimensional range distribution of 400 KeV Nd ions implanted into Si

Abstract

The 400 keV Nd ions were implanted into Si at a variety of tilt angles from 7° to 75°. The range distributions were accurately measured by the TOF-SIMS (Time-of-Flight secondary ion mass spectrometry) method. The results show that the measured range profiles can be represented by Pearson I type distributions which are in the same category as predicted by TRIM (TRansport of Ions in Matter). The first four statistical moments of the Nd-depth distribution, namely range, longitudinal straggling, skewness, and kurtosis, were obtained from the fitted profiles, and compared with the corresponding TRIM calculated values. Results show that the experimentally obtained range profiles are obviously deeper and broader than TRIM'95 (version 95.2) predictions, but very good agreements were obtained between the measured values and TRIM'98 (version 98.10) calculation. The longitudinal and lateral range stragglings for normal incidence were deduced from the angular dependence of the measured range distributions. Based on the range distributions for different angle implantation, the three-dimensional range distribution was reconstructed, and the lateral range straggling was obtained from the three-dimensional distribution and compared with both the predicted TRIM values and the deduced value.     

Anion antisite defects in GaAs and GaP

The electronic properties of anion antisite defects and the related ideal cation vacancies are calculated based on tight-binding Hamiltonians and using a novel recursion method. For the antisite defects symmetric A₁ states are found in the upper part of the fundamental gaps, and for the ideal vacancies T₂ states are found in the lower part of the gaps. These results for antisite defects compare favorably with recent ESR experiments.     

Superconductivity of F-substituted LnOBiS2 (Ln=La,Ce, Pr,Nd, Yb) compounds

Polycrystalline samples of F-substituted LnOBiS₂ (Ln?=?La, Ce, Pr, Nd, Yb) compounds were synthesized by solid-state reaction. The samples were characterized by X-ray diffraction measurements and found to have the ZrCuSiAs crystal structure. Electrical resistivity and magnetic susceptibility measurements were performed on all of the samples and specific heat measurements were made on those with Ln?=?La, Ce, and Yb. All of these compounds exhibit superconductivity in the range 1.9?K–5.4?K, which has not previously been reported for the compounds based on Ce, Pr, and Yb. The YbO_0.5F_0.5BiS₂ compound was also found to exhibit magnetic order at ～2.7?K that apparently coexists with superconductivity below 5.4?K.     

Nd~(3+)/Yb~(3+)掺杂YNbO_4粉末上转换发光特性

采用高温固相法,以50Nb_2O_5-40Y2O_3-2Nd2O_3-8Yb_2O_3的量比在1 300℃下制备Nd~(3+)/Yb~(3+)掺杂YNbO_4粉末样品。运用Judd-Ofelt理论研究样品光谱特性。由吸收谱中各吸收峰面积计算得到谱线强度参数Ωλ(λ=2,4,6),进而得出理论振子强度及实验振子强度,二者均方根偏差δ_(rms)=1.618×10-7。计算了Nd~(3+)能级4F3/2→4IJ'(J'=15/2,13/2,11/2,9/2)跃迁几率、跃迁分支比和能级寿命。4F3/2→4I11/2跃迁分支比最高(56.91%),对应波长1 062 nm。且亚稳态4F3/2能级寿命较长,为1.435 2 ms,适合作为上转换中间能级。在980 nm半导体激光器激发下,观测到波长为487,541,662 nm上转换发光,分别对应于Nd~(3+)的2G9/2→4I9/2、4G7/2→4I9/2和4G7/2→4I13/2辐射跃迁。通过样品上转换发射功率与激光器工作电流进行的曲线拟合,得到吸收光子数目依次为2.06,1.99,2.15,确定3个发射峰均对应于双光子吸收。     

Ultraviolet-visible spectroscopic characterization of lanthanum beryllate crystals doped with Er,Nd, or Pr ions

Spectroscopic characterization of lanthanum beryllate La₂Be₂O₅ (BLO) single crystals doped with trivalent ions of Eu, Nd or Pr, was carried out in the ultraviolet-visible spectral range using synchrotron radiation spectroscopy in combination with conventional optical absorption and luminescence spectroscopy techniques. On the basis of the obtained data, the energy level diagram for these trivalent impurity ions in BLO host lattice was developed; the optical and electronic properties of the crystals were determined; the possibility of the 4f-4f, 4f-5d and charge transfer transitions was analyzed; spectroscopic properties of the lattice defects formed during the introduction of trivalent impurity ions in the BLO host lattice, were investigated. We found that the lattice defects are responsible for a wide-band photoluminescence (PL) in the energy region of 400–600 nm. The most efficient excitation of the defect photoluminescence in the energy gap of BLO occurs in broad PL excitation-bands at 270 and 240 nm. The PL intensity of defects depends on the type of impurity ion and increases in the sequence: Pr-Nd-Er.     

ENDOR-investigations of iron doped GaAs and GaP

From ENDOR-measurements of GaAs:Fe³⁺ the symmetries and hyperfine parameters of three groups of neighbour nuclei have been obtained. The values of ||², r ^–3 and of the electric field gradients at the sites of the neighbour nuclei have been determined for GaAs:Fe³⁺ and GaP:Fe³⁺. The comparison of our results with those of NMR-investigations indicates the Fe³⁺-ion to be an interstitial impurity surrounded by four groupV atoms in a tetrahedral arrangement.     

Yb:YAG及Cr,Yb:YAG晶体的发光特性

研究了室温下YbYAG的上转换荧光光谱,此荧光归因于Yb3+离子的"合作"发光和Yb3+离子到稀土杂质离子的能量转移.测试了YbYAG晶体的X射线荧光,发光峰对应于电荷迁移态到Yb3+离子的基态、激光态间的跃迁.研究了Cr,YbYAG晶体的荧光光谱,讨论了Cr4+激光输出的可能性.     

Atom-probe field-ion microscopy of GaAs and GaP

The atom-probe field-ion microscope (atom-probe FIM) was applied for the first time to GaAs and GaP which belong to the III–V compound semiconductors. The general character of the pulsed field-evaporation of GaAs and GaP was quite similar. Ga field-evaporated predominantly in the form of singly charged ions. As and P also field-evaporated mainly as singly charged ions, but their abundances were small compared with Ga⁺. It appears that As (or P) atoms can field-evaporate more easily in the form of AsO⁺ (or PO⁺) in the presence of oxygen on the surface. In all experiments, GaAsⁿ⁺ and GaPⁿ⁺ were rarely detected. After chemical etching the surfaces were covered with oxide films and various oxide ions were detected. The abundance of oxide ions dramatically decreased after field evaporation in hydrogen. No distinct difference between the 〈111〉 orientations of these materials which have zinc-blende structure could be observed. Most of the experimental results obtained were explained in terms of the existing theory of field evaporation. It was concluded that field penetration effects have a considerable influence on the field evaporation processes of these materials as well as on the field ionization processes.