Anomalous photoluminescence of InAs quantum dots implanted by Mn ions

The photoluminescence (PL) of Mn-implanted quantum dot (QD) samples after rapid annealing is studied. It is found that the blue shift of the PL peak of the QDs, introduced by the rapid annealing, decreases abnormally as the implantation dose increases. This anomaly is probably related to the migration of Mn atoms to the InAs QDs during annealing, which leads to strain relaxation when Mn atoms enter InAs QDs or to the suppression of the inter-diffusion of In and Ga atoms when Mn atoms surround QDs. Both effects will suppress the blue shift of the QD PL peaks. The temperature dependence of the PL intensity of the heavily implanted QDs confirms the existence of defect traps around the QDs.     

X-ray diffraction studies of silicon implanted with high-energy erbium ions

Silicon crystals after implantation of erbium ions with energies in the range 0.8–2.0 MeV and doses in the range 1×10¹²–1×10¹⁴ cm⁻² have been studied by two-and three-crystal x-ray diffraction. Three types of two-crystal reflection curves are observed. They correspond to different structural states of the implanted layers. At moderate doses (1×10¹²–1×10¹³ cm⁻²) a positive strain is observed, due to the formation of secondary radiation defects of interstitial type. An increase of the implantation dose is accompanied by the formation of an amorphous layer separating the bulk layer and a thin monocrystalline surface layer. At an implantation dose of 1×10¹⁴ cm⁻² the monocrystalline surface layer is completely amorphized. Parameters of the implantation layers are determined. A model of the transformation of structural damage is discussed. Fiz. Tverd. Tela (St. Petersburg) 39, 853–857 (May 1997)     

Proposal for X-ray spectroscopy of muonic atoms formed from implanted ions in solid hydrogen films

A new method is proposed to extend muonic atom X-ray spectroscopy to the study of nuclear beams, including radioactive beams, by stopping both muon and nuclear beams in a solid hydrogen film. The muon transfer reaction to higher Z nuclei is used then to form muonic atoms. This method would allow studies of the nuclear charge distribution of unstable atoms. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electronic structure of carbyne studied by X-ray photoelectron spectroscopy and X-ray emission spectroscopy

The electronic structure of amorphous carbyne has been investigated by X-ray photoelectron spectroscopy and X-ray emission spectroscopy. Carbyne band structure has been calculated semiempirically and the experimental data have been interpreted on the basis of the calculation results. The valence band width was found to be about 20 eV which is the same as that in all other condensed carbon structures. The fine satellite structure near the 1s line of carbon has been studied. It is shown that the energy bands in carbyne are arranged in a mirror-like way relative to the Fermi level. The real carbyne structure is susceptible to conformations which affect primarily the π-subband structure.     

X-ray photoelectron spectroscopy of copper compounds

The X-ray photoelectron spectra of some forty-six copper compounds and complexes have been measured. The chemical shifts obtained from accurate determinations of the binding energies have been qualitatively explained on the basis of the Pauling electronegativity concept using the group electronegatives of Huheey for the polyatomic counter anions. The chemical shifts of the copper atoms as well as the atoms in the ligands were found to be dependent not only on the oxidation state but also on the kind and number of ligand atoms.

Intense satellite lines were found in the 2p and 2s bands of the cupric compounds; the number and splitting of the satellites were found to be sensitive to the chemical environment. A correlation was found between the satellite splitting and the binding energies and this is explained by a 3d→4s, 4p ‘shake-up’ mechanism.     

Study of silicon implanted with zinc and oxygen ions via Rutherford backscattering spectroscopy

The structural features and dopant profiles of a Si surface layer implanted with Zn⁺ and O⁺ ions are studied via Rutherford backscattering spectroscopy based on the analysis of He²⁺-ion spectra with the use of the channeling technique. The doping-impurity redistribution is analyzed upon the formation of zinc-oxide nanoparticles. The sample surface morphology is examined by means of atomic-force microscopy and scanning electron microscopy under secondary-electron emission conditions. X-ray phase analysis of the implanted layers is carried out.     

The effect of Mg ions on the photoluminescence of Ce-doped silica

In this paper, we report enhanced luminescence of Mg-co-doped silica gels, which were prepared by a sol-gel method. The total amount of Ce³⁺ ions was kept constant in this experiment at 0.5 mol% total doping. Structural, morphological, thermal, optical absorption and photoluminescence studies were employed. The XRD spectra show that all the samples are non-crystalline. Scanning electron microscopy (SEM) images show that the particles were in nano-range and spherical in shape. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) of samples depict that the presence of dopant and co-dopant decreases the endothermic peak temperature; while Ce³⁺ increase the yield, Mg²⁺ reduces it. UV analyses revealed that the presence of Ce³⁺ ions increases transmittance but lowers absorbance of annealed silica xerogels, while that of Mg²⁺ ions reduces transmittance but increases absorbance. Luminescence intensities were compared for different gels with and without Mg particles by varying the different concentrations of Mg. Silica containing Mg²⁺ ions had broad blue emission due to energy transfer from Mg²⁺ to Ce³⁺, which is due to radiative recombination. An increase in luminescence intensity was observed as the Mg²⁺ to Ce³⁺ ratio increased for the range investigated.     

X-ray photoelectron spectroscopy of boron implanted 4145 steel surface

The near-surface region of 4145 steel following boron implantation was investigated by x-ray photoelectron spectroscopy (XPS). The steel surface was implanted with¹¹B⁺ ions to a constant dose of 1.0×10¹⁷ ions cm^–2 at energies of 30 and 135 keV. The XPS spectrum of the implanted surface showed a shift in the B(1s) level towards the higher binding energy. The observed 188.0 eV binding energy of the B(1s) level was found to be in good agreement with the characteristic binding energy of the B(1s) level corresponding to iron boride (Fe₂B). Hence the increase in surface hardness reported previously is related to the formation of an iron boride layer in the near-surface region known for its hardening capabilities.     

X-ray emission from highly stripped atomic ions

Relativistic Dirac-Fock (DF) and central-field Dirac-Fock-Slater (DFS) calculations of X-ray emission from highly stripped atomic lead ions have been performed. The X-ray line shifts provide a nonmonotone characteristic of outer-shell ionization. The intensities of the most intense X-ray lines are largely unaffected by the removal of outer-shell electrons.     

Optical spectroscopy of Nd ions in a nanostructured glass matrix

This paper presents the optical characterization of Nd³⁺ ions in nanostructured SiO₂-Na₂CO₃-Al₂O₃-B₂O₃ (SNAB) CdS glass, synthesized by fusion. Radiative properties of the glass were determined by absorption, luminescence spectroscopy and lifetime measurements. Nd³⁺ emission enhancement and quenching were investigated in the presence of CdS nanocrystals. Nd³⁺-emission quenching was attributed to upconversion mechanisms and nonradiative processes such as multiphonon decay and energy transfer, while the Nd³⁺-emission enhancement was due to energy transfer from the CdS nanocrystals. Changes in the chemical environment around CdS nanocrystals were also confirmed by Judd-Ofelt calculations.     

X-ray spectroscopy of multiply-charged ions from laser plasmas

Original results are reported on the observation and identification of spectra of multiply-charged ions in the range of λ ≈ 1.5–15 Å, which corresponds to transitions with a range of principal quantum number n. The main part of the review consists of tables with about a thousand spectral lines, which have been mainly observed in laser-plasma radiation, as well as in the solar corona and other laboratory sources at an electron temperature T_e≈10⁷°K. The accuracy for the wavelengths (Δλ) is the following: Δλ is equal to ≈ 0.0005 Å for λ ≈ 2.5 Å and it is equal to ≈ 0.003 Å for λ ≈ 15 Å. The spectral lines are considered for the following transitions: 1-n type for [H]-like ions (Z = 11–16)and [He]-like ions (Z = 11–26); 2-n type for [Li]-like ions (Z = 19–26), [Be]-like ions (Z = 22–34) and [Ne]-like ions (Z = 26–42); 3-n type [Co]- and [Ni]-like ions (Z = 73). The line-list contains about four hundred wavelengths for multiply-charged iron L-ions (Fe(XVII)-Fe(XXIV)) and is presented with identification of some of the transitions. The wavelengths and intensities of satellites of the [H]-like ions and [He]-like ions, which are caused by transitions from the doubly-excited autoionization states 2l2l′ and 1s2l2L′ of [He]-like ions (Z = 11–16) and [Li]-like ions (Z = 11–26), respectively, are also considered.     

Ar的类氦和类锂离子与Mo表面相互作用过程中的x射线发射

在兰州重离子加速器国家实验室电子回旋共振离子源上用Si(Li)探测器观测到了不同动能的Ar¹⁵⁺和Ar¹⁶⁺离子与Mo表面相互作用过程产生的x射线.在不同动能 的Ar¹⁶⁺与Mo表面作用过程中不仅能观测到Ar的K层x射线而且能观测到Mo的L层x 射线.在不同动能的Ar¹⁵⁺入射下只能观测到Mo的L层x射线.实验结果表明，Ar的 K层x 射线的产额与入射离子的动能、作用过程中形成的空心原子携带的势能以及入射离子和靶原 子x射线的竞争等有关，Mo的L层x射线随入射离子动能的增加而增加. 关键词： x射线发射 高电荷态离子 Mo表面     

Determination of charge states of cobalt ions in nanostructured GdBaCo2O5.5 cobaltites by means of X-ray absorption spectroscopy

Physics of the Solid State - X-ray absorption spectroscopy has been applied for a characterization of charge states of cobalt ions of nanostructured GdBaCo2O5.5 complex oxides. The analysis of...     

离子注入n型GaN光致发光谱中宽黄光发射带研究

利用离子注入方法和光致发光技术系统研究了注入离子对n型GaN宽黄光发射带的影响.实验采用的注入离子为：N，O，Mg，Si和Ga，剂量分别为10¹³，10¹⁴，10¹⁵和10¹⁶/cm²，注入温度为室温.注入后的样品在900 ℃流动氮气环境下进行热退火，退火时间为10 min，并对退火前后的样品分别进行室温光致发光测量.通过实验数据的分析，独立提出了提取注入离子对晶体黄光发光特性影响的半经验模型.利用该模型导出的公式，可以确定注入的N，O，Ga，Mg和Si离子对黄光发射带的影响随注入剂量的变化关系以及该影响的相对强弱. 关键词： 氮化镓 光致发光谱 离子注入     

Simple fabrication of nanostructured silicon and photoluminescence

Porous Si (PS) was fabricated simply by electrochemical anodic etching of a Si wafer. By a combination of SEM, EDX and infrared spectrum measurements hydrogen-terminated crystalline Si surfaces were identified. Transparent Si nanocolloids were obtained via thermally-initiated hydrosilation of the hydrogenated Si surfaces reaction with unsaturated 1-undecene. In contrast to weak luminescence in the hydrogenated PS dispersed in toluene, intense luminescence was observed in the Si nanocolloid. In the Si nanocolloid, both strong luminescence and long-term stability can be correlated with alkylated passivation, as formation of Si–C bonds identified in infrared spectrum. Additionally, the oxidation effect was noticeable in affecting the luminescence of nano-Si during the process.     

Secondary electron emission control in X-ray photoelectron spectroscopy

Secondary electron emission (SEE) is a major player in surface charging during X-ray photoelectron spectroscopy (XPS); its characteristics and applicability as a current source for electrical measurements are studied. We employ sample biasing and a top retarding grid to control the photoelectron current, and further compare their I–V characteristics with direct spectroscopy of the secondary electrons. Using silica-coated gold substrates, the effect of sample work function on the emitted secondary electrons is shown and fine control over the surface potential gradients, in the range of 10–100 meV, is achieved. XPS-based chemically resolved electrical measurements (CREM) can thus be extended to the positive current regime.     

Tunable light emission and decaying process of photoluminescence from a nanostructured Si-in-SiNx film

Strong photoluminescence (PL) covering the green-violet band was measured at room temperature in an as-deposited amorphous Si-in-SiN_x film, which was prepared by plasma-enhanced chemical vapor deposition on cold (below 60 °C) Si(1 0 0) wafer. With an increase in photon energy of excitation, the PL shifts its peak position from 510 to 416 nm at yet-comparable intensities, thus allowing an energy-selected excitation in practical application. Also, a time-resolved analysis was performed for the emissions at various wavelengths, which showed a decay time shorter than 1.0 ns. These results indicate that the nanostructured Si-in-SiN_x can be a promising candidate material for the fabrication of silicon-based optical interconnections and switches.     

Study of iron implanted MgO crystals by low-energy electron induced X-ray spectroscopy

Magnesium oxide crystals implanted with Fe⁺ ions have been studied by means of Low-Energy-Electron-Induced X-ray Spectroscopy. All the implantations were carried out with 100 or 150 keV ion energy, at doses in the range from 10¹⁵ to 10¹⁷ ions cm^?2. The structure of the Fe L_II, L_III X-ray emission bands provides information about the iron chemical state. Fe L_II/L_III band intensity ratio measurements have been performed with a 3 keV electron excitation in order to investigate the whole implanted layer. In addition, by using a filtered Fourier transform technique on observed spectra, some modifications in the oxygen K emission band can be observed in implanted MgO crystals after thermal annealings in air. The oxygen spectrum fine structure suggests that the MgO matrix, partially destroyed by iron implantation, is restored after high temperature treatments. All the implantation, is restored after high temperature treatments. All the results are discussed on the basis of previous Mössbauer Spectroscopy studies and ion channeling investigations.     

Luminescent vacuum ultraviolet spectroscopy of Cr3+ ions in nanostructured aluminum oxide

Impurity Cr³⁺ centers in submicron and nanostructured Al₂O₃ crystals of different phase compositions at temperatures of 300 and 7.5 K were studied by a luminescent vacuum ultraviolet (VUV) spectroscopy method. Photoluminescence (PL) spectra and the energies of ²E, ⁴T₂, and ⁴T₁ excited states of Cr³⁺ ion depend on the type of crystalline samples phase. The PL excitation spectrum of R-line in α-Al₂O₃ nanoscale crystals is formed by intracenter transitions (2.5–5.5 eV region), by charge transfer band (6.9 eV) and by effective formation of impurity-bound excitons (9.0 eV region). Such impurity-bound excitons correspond to O₂p→Al₃s electron transition in surroundings of an impurity Cr³⁺ center. The efficiency of impurity-bound excitons formation decreases with the increase of the grain size above 100 nm. The size dependence is noticeably shown in PL excitation spectra in VUV region. Excitons bound to impurity centers do not appear in nanostructured δ+θ-Al₂O₃ crystals. The effect of the electron excitation multiplication is observed distinctly in nanostrucured α-Al₂O₃ at an excitation energy above 19 eV (more than 2E_g).